/smash/get/diva2:536454/FULLTEXT01.pdf

/smash/get/diva2:536454/FULLTEXT01.pdf
Requirements for Designing Moulds for
Composite Components
Nina Thorvaldsen
Master of Science in Product Design and Manufacturing
Submission date: February 2012
Supervisor:
Andreas Echtermeyer, IPM
Co-supervisor:
Tor Sigurd Breivik, Kongsberg Defence Systems
Norwegian University of Science and Technology
Department of Engineering Design and Materials
1
TRE NORWEGIAN UNIVERSITY
OF SCIENCE AND TECHNOLOGY
DEPARTMENT OF ENGINEERING DESIGN
AND MATERIALS
MASTER THESIS AUTUMN 2011
FOR
STUD.TECHN.
NINA THORVALD SEN
Requirements for designing molds for composite components
Krav til design av former for kompositt komponenter.
Composite materials are typically made in a mold giving them their geornetrical shape and
surface quality. Making good rnolds is important for the success of a composite product,
however, what are the criteria for a good mold has not been investigated rnuch. Different
product will require different molds depending on the performance requirements.
This thesis shall establish a set of criteria for a good mold that should be applicable for a wide
range of products. A review of current mold making techniques shall be made and the
techniques shall be evaluated against the newly established criteria. Ernphasis wiIl be put on
critical material properties and how these can be measured.
Finally a promising mold making method will be selected and evaluated for one specific
application.
The thesis should be written as a research report with summary both in English and
Norwegian, conclusion, literature references, table of contents, etc. During preparation of the
text. the candidate should make efforts to create a well arranged and well written report. To
ease the evaluation ofthe thesis, it is important to cross-reference text, tables and figures. For
evaluation ofthe work a thorough discussion ofresults is appreciated.
Three weeks after start of the thesis work, an A3 sheet illustrating the work is to be handed
in. A template for this presentation is available on the IPM’s web site under the menu
“Undervisning”. This sheet should be updated when the Master’s thesis is submitted.
The thesis shall be submitted as two paper versions. One electronic versjon is also requested
on a CD or a DVD, as a pdf-file.
Ole Ivar Sivertsen
Head of Division
Andreas Echtermeyer
Professor/Supervisor
•
NTNU
Norges teknisk
nanrvitenskapeige univei
jr
üg
titutt for produktutvi1cIrn
matcriakr
Acknowledgments
I would like to thank all of the people at KONGSBERG that has in one
way or another helped me with this thesis. It has been a big advantage for
the thesis to be able to stay there and work.
Tor Sigurd Breivik, my head supervisor at KONGSBERG deserves a
thank.
So do Alf Pettersen and Håvard Endresen for making this master
possible.
Terje Simlenes, Fred Simensen, Erik N. Eliassen and Per Olav
Kristiansen for good help and answering questions.
A great thanks to all
of the people in the workshop that has in small or bigger ways helped in
the process. People who must be named are Renate, Jean-David, Trond and
Eirin.
My gratitude is also for my supervisor at NTNU, Andreas Echtermeyer,
for good counsellings. The rest of the polymer and composite group has also
been a good help. I would especially thank Stanislav, Giovanni, Magnus and
John Harald for nice inputs.
At least my gratitude to Uta Freia Beer, for her hospitality.
ii
Preface
This thesis is the nal report in the degree of MSc in mechanical engineering at the Norwegian University of Science and Technology.
During the summer 2011 I had a summer internship at KONGSBERG
Defense Systems, at the division at Arsenalet.
KONGSBERG and I were
discussing the possibility for writing the master thesis in cooperation with
them. We landed on the topic of moulds for composite production, which is
highly relevant for Arsenalet.
Moulds for composite production are often ordered with an external company. As long as the nal part turns out well, is it a good mould. To make a
good laminate and a good nal product, it is important to have a good tool
to work with. The longer a mould lasts and the better the surface of the part
gets after it, the better. KONGSBERG wants to be able to make their own
moulds with high accuracy so that they fulll the tight tolerances.
Nina Thorvaldsen, Trondheim, 8th February 2012
Front page: A 20cm wide cut of a aluminium master mould and cured Beta
prepreg mould placed on top, after the composite has been released and it
is possible to see the spring-in.
[Photo: Nina Thorvaldsen]
iii
iv
Summary
The aim with this thesis was to investigate moulds for composite production.
A set of requirements needs to be established for such moulds.
The
requirements will then be used to nd the right material and production
method concerning the desired result.
Dierent production methods and
materials that can be used for moulds are presented.
Two dierent master moulds were made using two dierent types of materials, ytong and aluminium. On each of these master moulds, has two types
of carbon bre prepreg been used to make moulds. After cure has the dimensional accuracy of these moulds been measured and compared with the CAD
models. The accuracy has been one of KONGSBERG's main requirements.
One of the two shapes of moulds was used to make parts in. These two parts
have been measured after cure.
Abaqus has been used to carry out an FE-analysis with simulations of
spring due to cooling after cure.
The measurements and the analysis shows the spring-in, but with some
dierence in the results.
The two types of mould materials indicates good results for the shape
and size they were tested on. They fulll many of their requirements.
v
vi
Sammendrag
Målet med oppgaven har vært å utforske støpeformer for komposittstrukturer nærmere. Et sett med krav trengs å etableres for slike støpeverktøy.
Kravene blir så brukt til å komme frem til riktig materiale og produksjonsmetode i forhold til det resultatet man ønsker å oppnå. Det er presentert
forskjellige produksjonsmetoder og materialer som kan benyttes til å lage
støpeformer.
Det har blitt laget to mastermodeller med forskjellig utforming og med
forskjellige materialer, ytong og aluminium.
På hver av disse mastermod-
ellene har to forskjellige typer karbonber prepreg blitt brukt for å lage
støpeverktøy. Etter herding har den dimensionelle nøyaktigheten til støpeformene blir målt og sammenlignet med CAD modellene. Nøyaktigheten har
vært et av hovedkravene til KONGSBERG. Den ene verktøytypen ble brukt
til å lage deler i. Delene har blitt målt etter herding.
Abaqus har blitt brukt til å utføre en FE-analyse som illustrerer krymp
grunnet nedkjøling av delen etter herding.
Målingene og analysene viser spring-in, men med noe forskjeller i resultatene.
De typene av støpeformmaterialer indikerer gode resultater for de formene
og størrelsene de har blitt testet for. De utfyller mange av dems krav.
vii
viii
Nomenclature
α
=
Coecient of thermal expansion
BMI
=
Bismaleimid, type of resin
CFRP
=
Carbon bre reinforced plastic
CLT
=
Classical lamination theory
CMM
=
Coordinate measuring machine
CTE
=
Coecient of thermal expansion
Debulk
=
Apply vacuum on part during layup
Demould
=
Part release from mould
FDM
=
Fused deposition modeling
κ
=
Thermal conductivity
LTM
=
M61
=
Low Temperature Moulding
R used in this report
The type of HexTOOL
Master mould
=
The mould where the mould tool is made, not for
metals
Mould
=
The support structure that holds the laminate or
lay-up during the laminate consolidation process
[1]
NDT
=
Non-destructive test
Plug
=
Male mould
Prepreg
=
Preimpregnated bres with a resin system
RTM
=
Resin transfer moulding
Tg
=
Glass transition temperature
Tool
=
In this report used as the same as mould
UD
=
Uni-directional
VARTM
=
Vacuum-assisted Resin Transfer Moulding
ix
x
Contents
1
Introduction
1
1.1
Description of a mould . . . . . . . . . . . . . . . . . . . . . .
1
1.2
Master moulds
4
1.3
Production methods
1.4
Autoclave
1.5
Out-of-autoclave
1.6
Resin Transfer moulding, RTM
1.7
Vacuum-Assisted Resin Transfer Moulding
1.8
Pressure moulding
1.9
. . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . .
4
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
. . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . .
6
6
. . . . . . . . . . .
7
. . . . . . . . . . . . . . . . . . . . . . . .
7
Filament winding . . . . . . . . . . . . . . . . . . . . . . . . .
8
1.10 Injection moulding
. . . . . . . . . . . . . . . . . . . . . . . .
8
1.11 A typical mould for building of boats . . . . . . . . . . . . . .
9
1.12 Electically heated ceramic composite tooling . . . . . . . . . .
9
1.13 Fused deposition modeling, FDM
1.14 Nickel deposition
. . . . . . . . . . . . . . . .
9
. . . . . . . . . . . . . . . . . . . . . . . . .
10
2
Objectives
11
3
Requirements
13
3.1
Release part . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
3.2
Coecient of thermal expansion . . . . . . . . . . . . . . . . .
15
3.3
Dimensional accuracy and stability
. . . . . . . . . . . . . . .
15
Spring-in . . . . . . . . . . . . . . . . . . . . . . . . . .
16
3.3.1
3.4
Hold vacuum
. . . . . . . . . . . . . . . . . . . . . . . . . . .
18
3.5
Finish
3.6
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18
Durability . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19
3.7
Environment, health and safety
. . . . . . . . . . . . . . . . .
19
3.8
Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
3.9
Costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21
3.10 Machinability
. . . . . . . . . . . . . . . . . . . . . . . . . . .
3.11 Repair and modify
. . . . . . . . . . . . . . . . . . . . . . . .
21
22
3.12 Heat and pressure . . . . . . . . . . . . . . . . . . . . . . . . .
22
3.13 Materials lifetime . . . . . . . . . . . . . . . . . . . . . . . . .
22
3.14 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23
3.15 Adaptive work on part
. . . . . . . . . . . . . . . . . . . . . .
23
3.16 Curing conditions . . . . . . . . . . . . . . . . . . . . . . . . .
23
3.17 Lead time
24
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
xi
4
Materials for moulds
25
4.1
Aluminium
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
25
4.2
25
4.3
Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Invar
25
4.4
Titanium
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26
4.5
Ceramic
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
26
4.6
Composite - high/low cure . . . . . . . . . . . . . . . . . . . .
26
4.7
Graphite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
27
4.8
Nickel
27
4.9
Carbon foam
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . .
29
4.10 Concrete/ Ytong / Siporex . . . . . . . . . . . . . . . . . . . .
29
4.11 Wood
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
4.12 Tooling board . . . . . . . . . . . . . . . . . . . . . . . . . . .
29
4.13 Epoxy paste . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30
5
From requirements to design
33
6
Mould production
37
6.1
38
6.2
R . . . . . . . . . . . . . . . . . . . . . . . . . . . .
HexTOOL
R . . . . . . . . . . . . . .
6.1.1
Material data for HexTOOL
Beta Prepreg
6.2.1
6.3
6.4
7
8
. . . . . . . . . . . . . . . . . . . . . . . . . . .
Material data Beta Prepreg
39
. . . . . . . . . . . . . .
39
shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
41
6.5
C-shape
6.6
Parts made in C-shape mould
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . .
FE analysis
42
43
45
7.1
The process
7.2
Analysis of the
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ω
mould
. . . . . . . . . . . . . . . . . . . . .
Measurements
45
49
57
Ω
8.1
Measurements of the two
8.2
Measurements of the C shape
8.3
39
. . . . . . . . . . . . . . .
Layup of prepregs for autoclave cure
Ω
38
moulds
. . . . . . . . . . . . . . .
57
. . . . . . . . . . . . . . . . . .
62
8.2.1
Aluminium master mould
. . . . . . . . . . . . . . . .
64
8.2.2
Moulds made in C-shape . . . . . . . . . . . . . . . . .
64
Measurement of parts made in C-shape mould . . . . . . . . .
67
8.3.1
73
All three C-shapes together
xii
. . . . . . . . . . . . . . .
9
Results
75
9.1
FE analysis and real part . . . . . . . . . . . . . . . . . . . . .
75
9.2
Measurements, C-shape . . . . . . . . . . . . . . . . . . . . . .
R and Beta prepreg . . . . . . . . . . . . . . . . . .
HexTOOL
75
9.3
10 Discussion
10.1 The selection
10.2 FE analysis
76
77
. . . . . . . . . . . . . . . . . . . . . . . . . . .
77
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
77
10.3 The measurements
. . . . . . . . . . . . . . . . . . . . . . . .
78
10.4 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . .
78
11 Conclusion
81
12 References
83
A Appendix, thermologger
87
B
Appendix, FE analysis
89
C
Appendix, Measurements
91
xiii
xiv
List of Figures
1
Mould
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2
Female and male mould tool . . . . . . . . . . . . . . . . . . .
2
3
Visualization of master mould . . . . . . . . . . . . . . . . . .
4
4
Ω
5
5
RTM mould with part
. . . . . . . . . . . . . . . . . . . . . .
6
6
Vacuum infusion in the composite lab at NTNU . . . . . . . .
7
7
Pressure moulding with core material . . . . . . . . . . . . . .
8
8
Filament winding . . . . . . . . . . . . . . . . . . . . . . . . .
8
9
Visulaization of spring-in . . . . . . . . . . . . . . . . . . . . .
17
10
Machining of Ebaboard block at NTNU . . . . . . . . . . . . .
30
11
Width, height and length of a mould
. . . . . . . . . . . . . .
37
12
Thermocouples (Tc ) . . . . . . . . . . . . . . . . . . . . . . . .
41
42
of Beta prepreg in autoclave in KONGSBERG
. . . . . . .
2
13
Ω
14
Layup of C-shaped M61
15
Inner bag, during bagging of the C-shape . . . . . . . . . . . .
43
16
Layup of part in M61 C-shaped mould
. . . . . . . . . . . . .
44
17
Analysis of a plate
. . . . . . . . . . . . . . . . . . . . . . . .
46
18
Analysis of plate U2, y-direction . . . . . . . . . . . . . . . . .
◦
Illustration of a 0/90 laminate in Abaqus . . . . . . . . . . .
46
19
20
Fibre orientations . . . . . . . . . . . . . . . . . . . . . . . . .
47
mould and master mould after cure . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . .
Ω
21
Material orientation of the
22
Meshed part, four elements in the thickness direction
23
Selecting of nodes on the
24
Analysis of the
25
Analysis of the
26
Analysis of the
27
Analysis of the
28
Analysis of the
29
Analysis of the
30
The C-shaped mould with Beta prepreg during measuring
31
37
Ω shapes . . . . .
Ω moulds . . . . . . .
Cut 8 of the two Ω moulds . . . . . . .
Cut 13 of the two Ω moulds . . . . . .
A section of cut 8 of the two Ω moulds
...measurements point on the Ω... . . .
The average form of the two Ω . . . . .
38
...dierent measurements point on the C-shape
39
Plot of the various values of the Aluminium master mould
32
33
34
35
36
Ω
Ω
Ω
Ω
Ω
Ω
Ω
part . . . . . . . . . . . . . . . .
42
47
50
. . . . .
50
. . . . . . . . . . . . . . . . . . .
50
in U1, x-direction . . . . . . . . . . . . . . .
51
in U2, y-direction . . . . . . . . . . . . . . .
52
in U3, z-direction . . . . . . . . . . . . . . .
52
with a part, U1 x-direction . . . . . . . . . .
54
part made on a aluminum master mould
55
. .
part made on a ytong master mould . . . . .
. .
55
57
Plot of the measured
. . . . . . . . . . . . .
58
Cut 3 of the two
. . . . . . . . . . . . .
59
. . . . . . . . . . . . .
60
xv
. . . . . . . . . . . . .
60
. . . . . . . . . . . . .
61
. . . . . . . . . . . . .
61
. . . . . . . . . . . . .
62
. . . . . . . .
. .
64
65
40
Cut 1.10 on the C-shaped aluminium master mould . . . . . .
65
41
Cut 1.7 on the C-shaped aluminium master mould . . . . . . .
66
42
Plot of the measured depart from CAD part, C-shape, HexTool 66
43
Plot of the measured depart from CAD part, C-shape, Beta
.
67
44
Cut 1.2 on the C-shaped moulds . . . . . . . . . . . . . . . . .
68
45
Cut 1.7 on the C-shaped moulds . . . . . . . . . . . . . . . . .
69
46
Cut 1.10 on the C-shaped moulds . . . . . . . . . . . . . . . .
69
47
Cut 2.8 on the C-shaped moulds . . . . . . . . . . . . . . . . .
70
48
Plot of the measured parts . . . . . . . . . . . . . . . . . . . .
70
49
Cut 1.2 on the C-shaped parts . . . . . . . . . . . . . . . . . .
71
50
Cut 1.7 on the C-shaped parts . . . . . . . . . . . . . . . . . .
72
51
Cut 1.10 on the C-shaped parts
. . . . . . . . . . . . . . . . .
72
52
Cut 2.7 of the aluminium mould, HexTOOL mould, and part .
73
53
Cut 2.7 of the aluminium mould, HexTOOL mould, and part .
74
54
Thermo log of Beta cure, C-shape . . . . . . . . . . . . . . . .
87
Ω
55
Boundary conditions on the
56
Plot with the measurement points in the arc of the
mould and master mould . . . .
. . . . .
91
57
Measurements points 3 . . . . . . . . . . . . . . . . . . . . . .
92
58
Plot with the measurement points on the wings of the
59
Analysis of the
Ω
Ω
89
. . .
92
. . . . . . . . . . . . . . . . . . . . .
93
60
Aluminium master mould with measuring points . . . . . . . .
93
61
Carbon mould with measuring points . . . . . . . . . . . . . .
94
62
Carbon part with measuring points
94
Ω,
wings
xvi
. . . . . . . . . . . . . . .
List of Tables
1
Materials used for moulds
. . . . . . . . . . . . . . . . . . . .
3
2
Method used for nding a result . . . . . . . . . . . . . . . . .
11
3
Requirements for moulds . . . . . . . . . . . . . . . . . . . . .
14
4
3 reasons for why spring-in occurs . . . . . . . . . . . . . . . .
17
5
Suppliers and material for mould in composite . . . . . . . . .
28
6
Material selection . . . . . . . . . . . . . . . . . . . . . . . . .
31
7
Approximate sizes of moulds given in mm
37
9
. . . . . . . . . . .
R . . . . . . .
Uncured and cured material data for HexTOOL
R
Mechanical Properties for HexTOOL , for dry material . . . .
10
Uncured and cured material data for Beta Prepreg . . . . . . .
40
11
Mechanical Properties Beta Prepreg . . . . . . . . . . . . . . .
40
12
Number of plies, nal thickness and weight of the C-shape
. .
44
13
Material properties used in the analysis . . . . . . . . . . . . .
48
14
Displacement of the
8
Ω,
FE analysis
Ω
. . . . . . . . . . . . . . .
38
39
53
15
Average displacement of the
. . . . . . . . . . . . . . . . . .
63
16
Displacements in y-direction for C-shaped moulds . . . . . . .
68
17
Displacements in y-direction for C-shaped parts
. . . . . . . .
71
18
Displacements of master moulds of aluminium and ytong . . .
90
xvii
xviii
1 INTRODUCTION
1
Introduction
Moulds for composite are made in dierent materials.
known and extensively used as mould materials.
requires high accuracy to their products.
Metals are well
The aerospace industry
They seek materials that have
closer material properties to the product they are making.
Composite materials have many advantages over metals.
is rst of all lighter.
The material
Another advantage is that it is possible to produce
a material that meets a set of specic requirements.
Examples of this is
high strength, low density, excellent durability and many more.
However,
composite materials also have disadvantages. The cost is high both due to
high material and production cost. The lack of dimensional control are still
one of the main challanges.
When designing a component one of the rst, and most important considerations to make, is which material to use. Metals and plastics are well
known to most of us. Though, composite material is a newer way to get a
material with the properties specially designed for the wanted part. When
designing products of composite materials are there thousands of ways to use
it. One of the main benets of composites is its possibility to make complex
shapes with high strength and light weight.
When making shapes in composites a mould is needed. The mould serves
as support during production of the part. Depending on how the part should
look like, what kind of material is being used and how many parts are going
to be produced, mould tools are made especially for the purpose. Tooling for
composites is a wide eld which contains many technologies [2].
1.1 Description of a mould
A mould is a tool to make a part in or on. In the composite world, this is
the tool that you do the laminating on or in. This means that the laminate
will have the exact look as the mould on at least one side, only mirrored. So
every sign of scratches or bumps will be shown on the surface of the part.
Like it is said in an article about proper mould care: The tool surface sets
the quality baseline for production-part quality, so the part shape and surface
quality can be no better than that of the tool [3]. If the mould has a perfect
nish, the part will have that as well, as long as everything turns out right in
the layup and curing process. Some materials has to be machined afterwards
to have the perfect surface.
There is a cost aspect of what is the most eective way to make the mould.
The price of the material is a big investment.
To produce the mould in a
cost eective manner, you need to optimize the usage of material, labour and
1
1.1 Description of a mould
1 INTRODUCTION
Master mould and
mould
or
Mould and part
Mould / Part
Master mould
/ mould
Figure 1: Mould
machining hours spent. Either if it is fully machined or built up in dierent
steps and then maybe machined. When a lot of post work must be made on
the mould before it can be used, it might lead to big additional expense.
As Taylor-Wide says in his guide to composites [4] : Bear in mind that
this is one of the few processes where we make the material at the same time
as we make the component.
The parts are either made in a female mould, which can be seen in gure
2a, or on a male mould, gure 2b(also called a plug). Depending on which
side of the part that needs the right size and surface nish it is chosen either
female or male mould. A male mould has the lowest layup cost. It is also
possible to use a matched die mould, where both female and male moulds
are used. This is a good way to control the thickness, but it has high tooling
cost [2]. If the tool is correct in pressure moulding or RTM, as can be seen
in gure 7 and 5, all sides will have a nice and smooth nish.
(a) Female mould tool
(b) Male mould tool / plug
Figure 2: Female and male mould tool
When choosing a mould technique one of the main things to consider
is how the nal part should be produced.
Will the part for example be
exposed to high temperatures or pressure? The number of parts expected to
be produced will have a big inuence both on the production method and
the material of the mould.
For a prototype, the material can be of a less
2
1 INTRODUCTION
1.1 Description of a mould
durable material than if the form should handle hundreds of part produced
in it. This will contain layup, curing cycles and release. During production
the part is most likely to be moved around. Therefore is it important to take
in to consideration how much space that is required.
One of the biggest challenges and main considerations when choosing
material for the tool is the thermal expansion.
This should be as close to
the coecient of thermal expansion of the composite as possible[2]. There
are dierent curing techniques for dierent materials. Some can be cured
◦
◦
in room temperature, other in for example 60 C and other up to 500 C.
This makes of course dierent requirements for the mould and its material.
The curing method, as for example room temperature with vacuum or in
autoclave, will also aect the chois of tool-material. More information about
the dierent types of materials for moulds is to be found in section 4.
Some of the most common materials for moulds are listed in table 1, these
will be more described in section 4.
Table 1: Materials used for moulds
◦
◦
◦
◦
◦
◦
◦
Aluminum
Steel
Invar
◦
◦
◦
◦
◦
◦
R
Titanium
Ceramic
Composite - high/low cure
Graphite
Nickel
Carbon foam
Concrete/Ytong/plaster
Wood
Tooling board
Epoxy paste
Independent of what kind of material is used, the mould needs proper
care. If the mould does not get the attention it needs it will show either in
shorter life time for the mould, or in increased post mould rework for the
nished part. The results of insucient mould care is rst shown when it is
too late, and the mould needs extensive care and renovation [3].
Composite tools are one way of producing moulds, and can be made in
dierent ways. Airtech [5] and Composite Airframe Structures [2] divides it
into three groups, but a bit dierently:
Airtech
Composite Airframe Structures
◦
◦
◦
◦
◦
◦
Hand layup
Prepreg / Autoclave processing
Resin infusion processing
3
Wet layup
Hot-cured prepreg
Room-temperature-curing prepreg
1.2 Master moulds
1 INTRODUCTION
1.2 Master moulds
The master mould is the support structure used for making a mould. The
master is then a shape of the nal part, see gure 3. The master mould is
usually used very few times, often only once. For master moulds the materials
are often dierent from the mould. When the master mould is designed, it
is important to have the two next steps in mind, that means the mould and
the nal part. Both of them will somehow change, and it is then important
to know that the nal result will be as expected. Since it might only be used
once, it can be made of a material that is not so durable, and then often
at a lower cost. One of the main dierences in choosing material for master
mould and moulds is the temperature the curing should be carried out in.
◦
For typically low temperature components, the curing will be below 100 C
◦
[4], but often not higher than 90 C. This means that high temperature
◦
components are from 100 C and above. There exist more materials for low
cures than for high, and they are usually at a lower price.
Mould
Part
Master
Mould
Mould
(a) Master mould and mould
(b) Mould with part
Figure 3: Visualization of master mould
1.3 Production methods
Described in the next's subsections are dierent ways to make composite
parts.
This is for the part itself, but many of the methods are also used
for mould production.
All moulds, that will say masters, and moulds in
dierent materials, have to be coated with release agent before the layup can
take place. For the wash out mandrel, this is not so essential.
1.4 Autoclave
An autoclave is widely used for production of aerospace composite parts.
An autoclave is an expense for the company, both the acquisition and to run
the autoclave. It uses both heat and nitrogen to get the right temperature
4
1 INTRODUCTION
and pressure.
1.4 Autoclave
It works like a pressure vessel, which is why it looks like
a cylindrical tube with one closed end and door in the other end. The
◦
temperatures can be up to 650 C and normal working pressure is 7 bar;
max pressure is approximately 34 bar [2]. The cycle time for production in
autoclave is long, normal cure can be 15 hours with heating and cooling in
the right step, graph of a autoclave cure can be seen in gure 54 in appendix
A. The method of layup is either hand layup by the wet layup method or by
prepreg, but it is also possible with automated placement or automated tape
laying [6].
The material for moulds in autoclave production has to perform properly
at the temperatures and pressure the produced part needs for being cured
[7].
The temperature is controlled by thermocouples
Tc
that are attached to
the part, see gure 12. In gure 4 a part can be seen before and after cure
in autoclave with attached vacuum and thermocouples.
(a) Ω of Beta prepreg before autoclave cure
Figure 4:
Ω
(b) Ω of Beta prepreg after autoclave cure
of Beta prepreg in autoclave in KONGSBERG
[Photo: Terje Simlenes]
5
1.5 Out-of-autoclave
1 INTRODUCTION
1.5 Out-of-autoclave
The new thing in the aerospace industry is out-of-autoclave manufacturing. It is discussed in an article by G. Gardner, Out-of-autoclave prepregs:
Hype or revolution? [8], if out-of-autoclave really is the new thing. When
a company already has an autoclave, then they should use it. The prepregs
that are made for this purpose can be cured at lower temperatures and therefore the dierences of the CTE of the mould and the part will not have so
big inuence on the part. Many of the resin transfers methods are not for
autoclave cure.
1.6 Resin Transfer moulding, RTM
Resin transfer moulding, called RTM, is a process of transferring resin
into the dry reinforcement, typically a preformed form of bres in the form
of short, woven or stitched, which are placed in a closed mould. That means
that the mould is sealed, resin is injected into the mould vacuum may be
used. The part is cured with or without pressure. It is possible to heat both
the mould and the resin for better ow and faster cure. The mould can look
a bit like the mould for compression moulding, but it has an inlet for resin.
It also has some of the same requirements as for compression and injection
moulding. It has to withstand the pressure from the resin and the opposite
force of holding the form together. There are many advantages of RTM, like
class-a surface nish, short cycle times and near net shape moulded parts.
The mould is expensive due to matched moulds [7, 6, 9].
A new method called Same-Qualied Resin Transfer Moulding (SQRTM)
is a process where prepregs are laid up in a RTM matched mould. The same
resin type as in the prepreg is drawn through the mould with vacuum, and
then lls the small air holes with resin and prevents void formation [10].
Resin inlet
Laminate
Figure 5: RTM mould with part
6
1 INTRODUCTION
1.7 Vacuum-Assisted Resin Transfer Moulding
1.7 Vacuum-Assisted Resin Transfer Moulding
The short name is VARTM, or vacuum infusion (VI). This is similar to
RTM, but the resin is pulled through the bres by vacuum.
It can either
be a one sided tool with vacuum bag or two sided; gure 6 shows this with
vacuum bag. The tooling cost can then be lower than for RTM process. The
curing process causes heat, this have to be taken into account for big parts,
where large amount of resin is needed.
Clamp to clamp of
the vacuum and
resin
Vacuum pump
and outlet
Sealant tape
with tuck
Stack of glass
fibre plies with
peel ply,
realise film
and vacuum
bag
Flow
mesh
Resin
Inlet
Figure 6: Vacuum infusion in the composite lab at NTNU
[Photo: Nina Thorvaldsen]
1.8 Pressure moulding
This is a low volume production process where prepregs are placed inside
a mould, often by hand.
These moulds are usually made of some kind of
metal. The mould consists of a matched die mould see gure 7, where the part
are assembled inside one of the two tools. There are as good opportunities
to apply core material here as with many of the other techniques.
The
mould has to withstand a lot of pressure and temperature changes.
One
of the challenges is to know that the part inside the mould has the right
temperature, and that it lls the form perfectly without edges or dry spots
[11]. Compression moulding is a higher volume production method, where
the material is laid lightly on top of the mould and pressed into shape by the
pressure [9].
7
1.9 Filament winding
1 INTRODUCTION
Laminate
Mould
Core
Figure 7: Pressure moulding with core material
1.9 Filament winding
It is impossible not to mention lament winding even if the focus of this
report is not on that subject.
The winding technique is based on wind-
ing continuous long bre, impregnated with resin, on a rotating mandrel.
The impregnating of the bres can either be done by the manufacturer, like
prepreg, or by having a resin bath during winding right before the mandrel
that wets the bres. The direction of the bers depends on how the desired
strength should be.
The cure can be either in an oven or autoclave.
The
mould, called mandrel, can either be a part of the nal structure, or a part
that is removed after cure by mandrel extraction equipment, or washed out
if it is a material that dissolves in water [6].
Figure 8: Filament winding test done at NTNU by the polymer and composite group
[Photo: Nina Thorvaldsen]
1.10 Injection moulding
Injection moulding is a high volume production process, especially compared with many of the other composite processes. It can contain a type of
thermoplastic and some kind of reinforcement in form of short bres. The
material is injected into the mould while the mould is clamped together. It is
8
1 INTRODUCTION
1.11 A typical mould for building of boats
required matched metal dies because of the high temperature and pressure.
This makes the mould expensive, but it can be a cost saving process due to
high production volume with good tolerances. The part will not be able to
reach the same high strength and stiness as long bres [9].
1.11 A typical mould for building of boats
A leisure boat is usually built of glass bre.
This is a relativity large
structure, and also here the more time spent on surface nish of the master
mould, the more time is saved later.
The master should be produced at
specic dimensions and must resist styrene and heat, but it is cured at room
temperature. The second step is to apply gelcoat, and let cure until it feels
tacky. Then a skin coat should be applied, this gives a nice surface. Then
the lled resin system is sprayed on to the desired thickness, then a roller or
brush is used to remove entrapped air and get the lled resin into all small
places.
It is possible to apply cores to increase the stiness.
A stiening
frame can either be laid down at the wet laminate or glued onto the cured
surface. The curing time is usually 24 hr. This information is taken from
R Prole Tooling
one specic tooling brochure from Reichhold on Polylite
System [12]. Moulds for boats usually do not have those tight tolerances as
for example the aerospace industry. So it is not so bad if the mould slightly
changes its shape, but they also need to be assembled, so it cannot change
too much. The moulds are often made of random oriented glass bre and a
resin system, but not always done by spray layup, but by hand wet layup.
1.12 Electically heated ceramic composite tooling
Brádaigh, Doyle and Feerick [13] discussed ceramic composite tooling that
is electrically heated. These moulds are good for large composite structures
such as wind turbine blades and components for the aerospace industry. This
has an advantage since the parts can be cured out-of-autoclave and then saves
◦
investments and energy. The ceramic can be heated up to 1000 C, but the
◦
mould itself can be used at up to 300 C. The result of this study was
promising, and from the tests done at 12.6 metre wind turbine blade and an
aerospace part successfully manufactured [13].
1.13 Fused deposition modeling, FDM
As discussed in [14], one new way to produce master moulds and moulds
is by fused deposition modelling (FDM). The wanted result was to reduce
cost and cycle time, with the same or better result. FDM has for many years
9
1.14 Nickel deposition
1 INTRODUCTION
been used for prototyping. By using this method is it possible to produce a
tool without a series of negative and positive splash moulds. This reduces
cycle time and saves the environment from cure and deposit of extra parts.
The material that is used for this type are various types of thermoplastics
[14].
1.14 Nickel deposition
The electro-deposition nickel mould production is a process that has many
steps, which is one of the reasons why it is a costly method. First a master
model has to be created.
Then a splash is made on the master for then
making a plating mandrel in the splash. The plating mandrel is sunken into
an electroforming nickel solution to make the layer of nickel.
The nickel
part is then attached to a tool support structure, and the plated mandrel
is removed.
It has several advantages like a durable mould, easy release
of part, damage resistance and the possibility to repair with soldering or
welding.
But the CTE is quite high, close to the one for steel, which is
higher than composites.
Also here a correction factor must be included,
since the electroformed tool expands during cure, or shrink [2]. Nickel Vapour
Deposition (NVD) is another and faster way to make a nickel mould. The
method creates a more uniform wall thickness than electro-deposited and
is a much faster method.
A shell of nickel is created with nickel powder
and carbon monoxide gas in a chamber, and applied on a CNC machined
aluminium master. The method gives a virtually stress free mould with low
CTE and fast heating and cooling of the mould [10].
10
2 OBJECTIVES
2
Ob jectives
One of the aims with this project was to establish a set of requirements
for moulds for making composite parts.
Another aim was to nd a good
mould technique for some of the models for KONGSBERG. To be able to
reach this, it was important to know what they where looking for.
What
are actually the requirements for the moulds they are making? There exist
a various ways to make moulds, so some dierent methods will briey be
described.
The requirements will be dierent for dierent types of parts.
This depend much among others on the size and shape of the part. To know
if the mould reaches its dimensional requirements, the mould and part will
be measured.
KONGSBERG have the interest of knowing more about shapes that are
formed as the
Ω
and the C-shape.
There was chosen two rather small parts, see among others gure 11 and
14. On each of these shapes will there be tested two promising materials for
moulds, to nd the positive and negative about them. Within each of them,
there will be dierent ways to make them. These two materials was choosen
mainly because KONGSBERG wanted to investigate them further.
Since KONGSBERG is using most epoxy based carbon bre prepreg with
long bre, that is the main focus area in the report.
The procedure of the document and work are listed in table 2;
Table 2: Method used for nding a result
◦
◦
◦
◦
◦
◦
◦
Description of dierent mould techniques
Requirements for moulds
Dierent materials available for mould production
How to get from requirements to the selection
Make two of the promising solutions
Measurements and analyses
Was this as wanted?
11
2 OBJECTIVES
12
3 REQUIREMENTS
3
Requirements
The need to establish requirements for mould can be compared with the
importance of identifying costumers need in product design. To be able to
know what the nal result should look like, the product specication must
be known. The spesications are often revised more than once due to lack of
information on the constraints to the product technology. Tool design and
fabrication is the foundation for a good part.
There is just as important
to spend engineering time and money on the mould design as for the part
[15, 9].
As mentioned earlier, there exists a number of mould techniques and ways
to make composites. Many of the requirements for these techniques are often
the same, but many are dierent. There are dierent ways to make the parts,
dierent materials, thickness, stability, surface nish, look and so on. One
of the most common requirements is that the part turns out the way it was
supposed to, that the size ts in with the assembly it should t into. With a
good surface nish on the mould, the part will have a good surface quality,
but never better than the mould. Not all moulds have to withstand the same
temperatures and pressure during manufacturing and that will make dierent
requirements and specications. Some parts are meant to have the perfect
nish while others are meant to be done something with afterwards.
Is it
desired to make the mould in house or outsource it? Some of the techniques
require a lot of equipment, so if the company only wants to have a very few
number of moulds in that technique, it should be considered to let somebody
else do the making.
Many of the requirements for making a tool for metallic structures or
injection moulding are the same for lamination tools for composites as well.
Many of the requirements are so naturally given, that it sounds strange to
mention, and might be easy to forget to mention. Others are so matter of
course that they are always mentioned but not necessarily easy to maintain.
In addition for the mould design it is important that the tool extend at least
5cm beyond the part to make room for sealant tape. It is also important to
have the vacuum attachment in mind.
For KONGSBERG it is important to have a mould with the right shape
and to know what they are working with. This is more important than to
reduce cost and time.
Of course these are important aspects as well, but
they don't have the highest priority. Since parts they produce are assembled
with many other parts, it is important to have them as accurate as possible.
The requirements for accuracy in the aerospace industry are stricter than in
many other industries. The less time used on unnecessary adjustments on
each part, the more time and money is saved and it is possible to achieve a
13
3.1 Release part
3 REQUIREMENTS
Table 3: Requirements for moulds, more described in the next sections
1
Release part
2
Coecient of thermal expansion
3
Dimensional accuracy and stability
4
Hold vacuum
5
Finish
6
Durability
7
Environment, health and safety
8
Weight
9
Costs
10
Machinability
11
Repair and modify
12
Heat and pressure
13
Materials lifetime
14
Maintenance
15
Adaptive work on part
16
Curing conditions
17
Lead time
higher production rate. There are quite tight tolerances, so it calls for more
accurate mould. Many of the products KONGSBERG are making are meant
to be ying, and small changes in the symmetry or wrong size of shapes
can make big dierence to the performance and the fuel consumption.
It
is important to have a mould they can use many times, since much time
and eort is used on one mould.
One of the reasons for that is of course
that they don't have to make a new one all the time, there are expenses
of making a mould in labour and material costs, but also environmental
concerns of the use and disposal of parts. If they have to make a new one
every 10th time instead of every 100ed time, it will lead to a lot of waste.
For other applications as one of the rst prototype it is best to for example
make a low cost mould for one time use.
A summary of some requirements compared with dierent material types
can be found in table 6.
3.1 Release part
It is desired that it should be as easy as possible to release the part from
the mould. Release agent must always be applied on the mould before layup.
The material in the mould and part must not react with this agent. In some
cases it is not possible to make the part without having an assembled mould.
14
3 REQUIREMENTS
3.2 Coecient of thermal expansion
That means that the mould is taken apart when the part should be released.
This leads to extra concerns about where it is possible to have edges and
where the part can be sanded afterwards. There is also a challenge to get
it vacuum tight. The sealing of the part must withstand the same heat and
pressure, but must be able to release again. For lament winding a segment
mandrel is required where the part are not to be slided o after cure, a wash
out mandrel or is a part of the structure.
3.2 Coecient of thermal expansion
Coecient of thermal expansion, CTE (α), is especially an issue for parts
that are undergoing high temperature changes during cure.
If the CTE is
similar to the produced part, the spring will be smaller and likely make crack
in the ply or delamination [9, 16].
In the mould making industry for composites this is one of the main considerations. The CTE for composites is low, and it is an advantage to have
the coecients for the mould and the part as close to each other as possible. The coecient tells how much the material expands with temperature
changes. Some carbon bre epoxies have negative CTE.
There are dierent standards for measuring the CTE. A typical method
is to measure the change in length of a specimen when constant heat is
applied. ASTM E228-11 describes it for rigid solid materials with a Push-Rod
Dilatometer. In ISO 11359-2 the method of testing the coecient of linear
thermal expansion and glass transition temperature by Thermomechanical
analysis (TMA) is given. This is by using thermodilatometry where TMA is
one type [17]. In Structural Analysis of Polyneric Composite Materials says
it that a normal method to nd the in plane thermal expansion is to use
resistance foil strain gages [18].
3.3 Dimensional accuracy and stability
As mentioned in the book Advanced Composites Manufacturing [7], the
production method for all advanced composites needs the tooling to be hard
if the structure should be supported during layup and cure.
As discussed
later in this chapter, the spring-in phenomena is a well known problem in
composite production, meaning both the mould and part making.
Some moulds need support structure, either for holding the mould stable
during layup or to stabilise the structure during cure. If autoclave is used, the
mould has to withstand a certain pressure, usually 7 bar, and it then most
likely has to be solid. If not, you might risk to having the mould collapse
15
3.3 Dimensional accuracy and stability
3 REQUIREMENTS
during cure, and the part will then be totally dierent from what you wanted
[4].
Thermal conductivity (κ), also called heat conductivity, is the conduction
of heat transfer and is aected by temperature and pressure. This is often
evaluated when mould material are selected.
A high thermal conductivity
means a high heat up and cool down rate.
A test method would be to
calculate the heat by applying two dierent temperatures in each end of a
specimen. Typical test method that are more described in ISO/TR 22007-1
are: hot-wire method, line-source method, transparent plane source method,
temperature wave analysis method, laser ash method [19, 20].
Tg
is the point of where a polymeric material changes from a rigid glossy
solid into a softer, semi-exible material [9].
This means that
Tg
is the
maximum temperature in which the material can be used, and still have
the same mechanical properties. The actual operating temperature should
◦
always be at least 10 C lower than Tg [9]. This value is often provided by
the material manufacturer.
For compression moulding, injection moulding and transfer moulding
the ASTM standard D 6289-08 [21], Standard Test Method for Measuring Shrinkage from Mold Dimensions of Molded Thermosetting Plastics,
gives one interpretation of the results of the mould shrinkage (MS), given in
equation (1).
MS =
L0 − L1
· 100%
L0
(1)
This is in percentage where:
L0
L1
=
=
length of the dimension of the mould, specied in mm
length of the corresponding dimension measured on the test
specimen, mm
L2
=
length of the same dimension of the test specimen, measured
after heat treatment at 48h or 168h, mm.
All measurements of dimensions should measure the length of the cavities
◦
to the nearest 0.02mm at a temperature of 23 ± 2 C.
The post shrinkage (PS) is given in equation (2)
P S 48h orP S 168h =
3.3.1
L1 − L2
· 100%
L1
(2)
Spring-in
Spring-in, also called spring back, is a common phenomenon for most
kind of materials and especially moulded parts. The behaviour is dierent
16
3 REQUIREMENTS
3.3 Dimensional accuracy and stability
from material to material, thickness, shape, temperatures etc. For metal for
example the spring can occur when sheet metal is bent, and it then bends
slightly back.
For composite materials the spring often happens after or
during curing, then opposite of metals, so the nal shape might be smaller
◦
than the mould. It is normal to make the mould with an angle of 2 bigger
than how the nal part should be, see gure 9, [9].
Spring-in
angle
Part
Spring-in
angle
Part
Mould
Mould
(a) Female mould with spring-in
(b) Male mould with spring-in
Figure 9: Visulaization of spring-in
There are three main reasons for why spring-in occurs, these can be seen
in table 4.
Table 4: 3 reasons for why spring-in occurs, taken from [22]
◦
◦
◦
Chemical shrinkage (the volume changes/shrink due to resin hardening)
Thermal shrinkage (the volume changes due to CTE)
Mismatch between coecient of thermal expansion (CTE) for resin and
carbon ber
Chemical shrinkage happens when the resin is crossed linked in the curing
process. Thermal shrinkage is caused by the CTE. The mismatch CTE of
resin and bre is one of the main reasons for the spring-in on curved parts.
This because of the strain dierence in x and z direction [23, 24, 22].
An equation for predicting spring-in for laminates with angle are found
in equation (3). The equation considers temperature dierence during cure,
thermal expansion, cure shrinkage and the angle of the part. This is more
discussed in [25], it is also used by people at KONGSBERG.
∆θ = ∆θCT E + ∆θCS = θ
(αl − αt )∆T
1 + αt ∆T
+θ
φl − φt
1 + φt
(3)
One way to measure the spring is using dierent measuring machines,
either with laser or coordinate measuring machine. Another way to measure
17
3.4 Hold vacuum
3 REQUIREMENTS
Where:
∆θ
∆θCT E
∆θCS
θ
αl
αt
∆T
φl
φt
=
Spring in angle
=
Thermal component of the spring-in angle
=
Cure shrinkage component of the spring-in angle
=
Part angle
=
longitudinal coecient of thermal expansion
=
Through thickness coecient of thermal expansion
=
dierence between cure temperature and ambient temperature
=
longitudinal cure shrinkage
=
through-thickness cure shrinkage
it might be to embed optical bres in the laminate, and measure the changes
during cure and post curing of the mould.
This has been considered, but
a solution to measure during cure with optical bres in autoclave has not
been found. Then another solution can be to glue the bres on after curing.
It is also possible to apply a grid on the master mould and then inside the
mould, take pictures of it after cure, compare the pictures and see what the
dierences are.
3.4 Hold vacuum
If the part is exposed to vacuum and pressure it must withstand it. This
is very obvious, and it will be a very bad mould if it does not. If the moulds
are to be used many times it must hold the vacuum during its whole life.
Composite mould tools are often sealed with some kind of resin, both for
sealing pinholes and to get rid of potential vacuum leaks. For smaller mould
an envelope bag can be used, then the vacuum tightness is not so critical.
Methods for which this is important are VARTM, RTM and autoclave moulding. Pressure moulds for example must not handle vacuum, but the pressure
from the press [4].
In the most of composite production is it important to avoid voids. This
is also important for a mould made of composite. This is on of the resons
for using vacuum. One way to nd out if there are voids in a laminate are
to use non-destructive testing (NDT). Normal methods for this is ultrasonic
inspection and x-ray [9].
3.5 Finish
Since the part will have the same nish as the mould, this is an important
aspect. If it is desired to have a shiny nish of the part, the mould has to
18
3 REQUIREMENTS
3.6 Durability
be absolutely perfect and highly polished. It must be considered which side
to be tooled. If there is desired to have a nice and smooth outer surface or
are parts to be assembled inside, so it need dimensional control on the inside
[20, 9]. See gure 2 for male and female moulds.
The mould should ideally have center points and a type of line that locate
where the part are to be trimmed. The points will help on the location of
the layup.
If the part is a loadbearing structure during use, the production method
may be dierent from a non structural element.
The part receives better
material properties by curing in autoclave than with for example pressure
moulding.
This is due to the combination of vacuum and pressure in the
autoclave that eliminates voids. Pressure moulding usually have only pressure and heat [9].
It is possible to measure the surface with a surface roughness tool. These
measurements should be taken of the master mould rst to be sure that is
good enough.
The master mould will be coated with release agent before
the mould layup is done, this will seal small pores and smoothen the surface
more. One of the main reasons for this is of course to be able to release the
mould from the master. How good nish does the material gives us? Is it a
perfect mirrored picture of the master?
3.6 Durability
Some moulds are used only once, other hundreds or thousands. The materials durability has to be chosen so it ts to the number of cycles it is
supposed to last. This is often one of the overriding factors in the material
selection process. It is one way to make moulds that ts for one type of production method but not others. Some moulds are better for RTM production
and some are better for autoclave. Steel is a typical material for processes
that requires many cycles, 1000-100 000.
Composite moulds have various
lifetime, from 1 to 1000 cure cycles [9].
3.7 Environment, health and safety
The concern of health and safety are always dierent from company to
company. How much health and safety equipment that must be used often
depends on how often a mould will be made and how volatile the material
is during the whole life cycle. Either way it is desired to use materials that
are best both for the people who are going to work with them and of course
for the environment before, during and after use. Things that are often not
mentioned in the data sheets, are the volatiles and odoures that might aect
19
3.8 Weight
3 REQUIREMENTS
some people more than others. Some materials and liquids are more allergies
inciting than others and some people are more sensitive to chemicals than
others. If the mould will only be used or produced a few number of times, it
can be more justiable to use more personal protective equipment then if it
is for everyday use.
Machining of composites is not good for the health, the dust is light
and the particles are very small. Fibres might penetrate the skin; the carbon
bres are often thinner and stier than glass bres, so it is even worse and care
must be taken. If possible, the machining should be done in a closed room.
Dust should be prevented, dust extract fan and masks should be used. Some
health and safety issues that are normal for composite production [26, 27]
are:
◦
◦
◦
◦
◦
Irritating to eyes
Irritation to skin
Risk of serious damage to skin
May cause sensitization by skin contact
Must be considered as having carcinogenic eects on human beings
For the environment, the toxicity of the material is important. When the
material are selected, the disposal must be considered. If the material is very
toxic, it will be bad for the health as well. Other aspects of the environmental
are the amount of produced and deposed parts. Which means that a material
that can take many cure cycles before it need replacement is better for the
environment. An other aspect is how much energy that are used for heat-up
and cool-down. A material with high thermal mass will need more energy
for this.
3.8 Weight
This is not always the main criteria, but it must be taken into account. It
is especially important for the worker who transports the mould in dierent
areas of the production hall. It should be possible to move during layup as
well.
This is also a health criterion for the workers who move the moulds
around.
If the part is too heavy to move, this might lead to strain injury
since the mould has to be moved at some point. For small parts it might be
interesting to be able to use an envelope bag for vacuum. It is sometimes
easier to get an envelope bag sealed than one that is sealed around the edges.
Then it must be possible to move the mould into the bag. In many companies
where big parts is produced, the movement of the mould are often done with
machines, and then the machine must be able to handle the weight. If the
part and mould are big and heavy it might lead to challenges.
Weight is also an issue for the production rate and energy for heat-up.
20
3 REQUIREMENTS
3.9 Costs
Lover weight means lower thermal mass, enabling faster heat-up/cool-down
cycles. [16]
3.9 Costs
One way to make perfect surface nish on a composite mould is to make
the master mould perfect, and then have the right material that can be used
directly from the master to create the mould. Or the master can be rather
roughly machined, and then the mould machined to the right tolerance. It
must be considered if it is more expensive to make a perfect master mould or
to machine the mould tool afterwards. The cost can be measured in dierent
ways. One way is to only look at the real cost of the materials, but that is
not accurate enough. Everything in the process that leads to more people
involved and more hours spent on the part is a disadvantage. If the material
cost is low, but it leads to high labour costs because of maintenance and
complementary work, it might not be the best solution after all.
Considering for example the master mould; machining the master mould
perfectly in metal compared with a rougher material with not so tight requirements. It costs less to machine a soft material to a rough nish than to
machine it to a ne surface or machine metals.
Small
cost example
◦
◦
◦
◦
Cost of ytong pr kg
Cost of machining ytong pr
m2
Cost of materials to strengthen the ytong surface
Cost of machining the mould
versus
◦
◦
Cost of aluminum pr kg
Cost of machining aluminum pr
m2
3.10 Machinability
If the material is easy to machine it will lead to reduced production costs.
Some materials are better for machining than others, and some might change
stability during or after machining. Sti materials are easy to machine, but
soft materials are better to shape by forming than machine. If it is machined
in blocks and put together after machining it might lead to challenges if the
machined parts have deformed.
21
3.11 Repair and modify
3 REQUIREMENTS
3.11 Repair and modify
Often when a full assembly is to be done, the dierent parts in the assembly don't t like they were supposed to, or there is an assembly detail
that has not been considered. It might be things that people haven't thought
about, like that hands should be able to reach into small places, and put the
dierent parts together.
It might also be that parts change during curing
and then are slightly dierent from the requirements that are set.
These
are things that lead to changes of the part, and then it must be possible to
change the tool. Also as discussed in chapter 3.3.1, the spring-in, is one of
the things that might lead to changes of the mould, if it is not calculated
right. The spring is often applied to the tool by trial and error to nd the
right shape, and then changes must be possible to make.
Changes can be
done either by applying material to the master mould, the mould, or if it is
too big, machine it down.
3.12 Heat and pressure
The material has to handle the temperatures it is exposed for. Most of the
epoxies that has been post cured, is cured so that changes are not supposed
to occur. Maximum cure-, post-cure- and service temperatures are easy to
nd in the manufactures papers.
High temperatures strain gauges can be
used on specimens to nd for example
Tg .
able to withstand autoclave pressure.
Solid materials will most likely be
In moulding methods where a press
is used, metal moulds are the most common in use. The materials thermal
mass have something to say of how fast the material can be heated up and
cooled down. For all cures except for room temperature, has this a role. It
can aect the curing process if this is slow.
3.13 Materials lifetime
As known, prepregs has a limited life time, metals of course don't have
1
the same issue. The material must handle the out-time
it takes to make the
part. All materials that contain resin have a certain time it can be held at
room temperature before the curing process gets too far. The out of store
life is described by hours, days or months. The storage is usually maximum
−18 ◦ C. These data are provided by the manufacturer and may wary for
dierent materials. It might take days to make a mould in composites, so it
1 Prepregs
temperature
has a certain time it can be exposed to other temperatures than the storage
22
3 REQUIREMENTS
3.14 Maintenance
must be known roughly how long time it will take to make the part and how
long time it is left for the material.
3.14 Maintenance
All moulds have to be taken care of and perfectly cleaned and released
after each use.
The less time this takes, the better.
If the mould has low
durability it either can be used only a few times or it need extended maintenance or coating. The hardest material is not always the best. After the
material is cured it has to be demoulded, and if the mould is not perfectly
cleaned and/or treated with release agent, it might be dicult to loosen. If
the mould then is made by soft material, it might stick to the part, and the
mould needs repair.
3.15 Adaptive work on part
For metals moulds that are perfectly machined, the adaptive work is only
release agent, if the part tolerate spring and thermal issues are taken into
consideration. If the mould is being made of a composite material, the way
to proceed from the production is dierent. Either the master mould has to
have a perfect surface or the mould has to be machined to a perfect nish.
Often a combination is used. If one machining is saved, time is saved.
3.16 Curing conditions
If the part is going to be cured in an autoclave it is preferred that all
parts that have been laid up in a mould can be cured together. It is always
desired to ll the autoclave with as many parts as possible.
Some mater-
ials can inuence dierently on the temperature and curing process.
It is
recommended to cure parts made on metal moulds together and parts made
on composite moulds together, and not to mix, according to expertise in
autoclave curing at KONGSBERG. This due to dierent thermal mass, and
dierence in the heat up rate. If a small mould with short heat up rate are
cured together with a massive metal mould with slow heat up rate, can the
curing be wrong.
The autoclave temperature is controlled by the thermo-
couple with the highest and lowes temperature. The thermocouples on the
two parts will then display a higher temperature on the part for the fast heat
up rate.
23
3.17 Lead time
3 REQUIREMENTS
3.17 Lead time
For example dierent tooling materials in carbon bre are not produced
in an innite amount, and there are not many that produces it. This means
that it might take a while to order it and the price can be high. Materials
like wood, steel and aluminium might be easier to get on short notice, but it
might also here be challenges like nding a place that has machining capasity.
24
4 MATERIALS FOR MOULDS
4
Materials for moulds
Material selection for moulds is often based on experience, which can be
either one in the company, recommendations from others in the industry or
suppliers.
It is not always possible to say which material is best for the
specic mould [20].
In the subsections below are brief summaries of some
typical materials for mould production, what kind of production is typical
for them and benets and negative aspects of using that material. In table
6 is there a summary of the materials with dierent properties.
When mould material is selected with a greater expands rate than the
composite produced on it, this must be taken into account when dimensioning
the tool. The tool will then expand more during heat-up, and contract more
during cure than the produced part. Both can cause cracks in the part in
incorrect method is used [9].
4.1 Aluminium
Aluminium is a well known material for moulds in composite production.
It is possible to achieve a perfect surface and it can be used in relatively
high temperature curing processes. The CTE is higher than for composites.
The material is quite expensive and the machining cost is high, and higher
R is one aluminium type in the
with better surface nishes [16, 2] . CERTAL
7000-series. This is used and recommended as a mould material due to good
shape stability, corrosion resistance and good machinability [28].
4.2 Steel
Some of the main advantages of steel are the low material cost. Other
positive thins for moulds are steels ability for readily cast and welding. It is
also durable and can stand 1500 autoclave cures [9]. It has good availability
−6
◦
and better CTE compared with aluminium; 10.2 − 14.5 · 10
/ C for mould
R
−6
◦
steel vs. 23 · 10
/ C for CERTAL
[29, 28], but yet again higher than
carbon/epoxy.
One of the main disadvantage is high manufacturing costs,
which applies for all metals, diculties of forming into complex shapes, but
maybe most important its high weight [9, 2].
4.3 Invar R
Invar
R
is an alloy of iron and nickel. The material is expensive and heavy,
R is a well known mould material especially
Invar
but performs very well.
in the aerospace industry, where the tolerances are higher than in other
25
4.4 Titanium
4 MATERIALS FOR MOULDS
−6
◦
industries [16]. CTE is from 0.63 · 10
/ C for temperatures
2.5 · 10−6 / ◦ C for higher temperatures like 20 − 200 ◦ C [29].
(−55) − 95 ◦ C,
4.4 Titanium
Titanium is normally only used as coating in form of titanium nitride
TiN for injection moulding tools.
This is if it is desired to have a harder
surface on a metal mould and better ow. It has excellent chemical resistance.
Advantages are better abrasion and corrosion resistance and better lubricant.
◦
Application temperatures are 425 C and higher. There are more types of
coating for moulds with more or less the same purpose [30, 29].
4.5 Ceramic
Ceramic is a group of materials, they are known as brittle material.
◦
In general can they withstand heat very well, up to 1000 C and can be
shaped into several contours and complex shapes. They have low CTE at
0.9 − 8.1 · 10−6 , close to carbon ber composites. The dimensional control
is very good.
It is suitable for high temperature cure like of polyamides
and thermoplastic. Disadvantages are low machinability, dicult to repair,
long heat-up and cool-down rates [2, 13].
Is often used with electric heat
embedded in the tool, which ceramics are perfect for, see more in chapter
1.12.
4.6 Composite - high/low cure
One of the biggest benets of composite moulds is its possibility to match
CTE to the carbon bre part. It exist a high number of various compositions
of bre and resin types. All of the composite moulds need a master mould or
mandrel. They also have a weight that is much lighter than metals. There has
been challenges with cracking of the mould after some cures, which results in
leakages. The materials on the marked now are better developed, so it there
are less changes of matrix cracking [9, 31]
Glass bres and epoxy are good for low temperature moulding. Depend180 ◦ C,
ing on the postcure temperature, can they take temperatures up to
but in general they are for low temperature cures than carbon bre. One of
the reasons for this might be that they can not match carbon bres on fatigue properties and modulus. For high performance composite applications
carbon bre is preferred. But in commercial use glass bres are extensively
used. They have advantages like low cost, good impact, chemical and tensile
strength [9].
26
4 MATERIALS FOR MOULDS
4.7 Graphite
It is of course advantages and disadvantages with composite mould tools,
and some of the positive ones that are mentioned in Composite Airframe
Structures [2] are listed below:
◦
Since the mould is not machined from a block, but built up, it contains
less materials than others.
◦
Low cost can be achieved since the master model can be of a lower cost
than the mould.
◦
◦
Low CTE and more similar to the produced part can be achieved.
Low density makes it easier to handle in production.
One of the main weak points of composite mould tools is the matrix. It
is tough for the matrix to withstand the number of cycles of the curing of
parts if this is many without cracking.
A list of dierent types of suppliers with some of their composite materials
for moulds, taken from [31], is found in table 5.
Most of them have more
types than listed.
4.7 Graphite
The monolithic graphite method is to create a near net size by bonding
blocks together and machine them down. The surface is coated either with a
lm, resin or resin and laminate. Advantages are easily machining, low fab◦
rication and material cost, low CTE and dimensional stability up to 2000 C.
It is easy to repair and modify, but might be brittle and soft, so it can easily
be destroyed as well. This depends on the quality, there exist many dierent
qualities. The cross section cannot be too small to maintain the structural
integrity. When machining the material a lot of dust is created, this can be
injurious to the health [2].
4.8 Nickel
Nickel is most used as electro-deposited, or as Nickel Vapour Deposition
(NVD), this is more discussed in section 1.14.
Both methods make good
moulds, that requires less metal than with steel and aluminium. Since it is
not machined but deposited, this also leads to lighter moulds. They often
need a backing structure for layup and cure.
27
4 MATERIALS FOR MOULDS
4.8 Nickel
Table 5: Suppliers and material for mould in composite
BMI/Carbon prepreg
Material
125
190
Use
Postcure
Postcure
Postcure
Engineered
Materials
Cytec
Materials
Advanced Composites Group
Comment
Name
Epoxy/Carbon prepreg
High
Postcure
C
R M61
HexTOOL
R M81
HexTOOL
BMI/Carbon prepreg
Mid
◦
Autoclave
DURATOOL 450
Epoxy/Carbon prepreg
200/250
Prod.
Autoclave
DURATOOL 7620
BMI/prepreg
200
Supplier
Hexcel
Autoclave
R 556 & 515-1
HTM
Epoxy/prepreg
High
Interna-
method
Hexcel
Autoclave
HX42
Epoxy/prepreg
High
Engineered
Amber Composites
Carbon foam
Cytec
Amber Composites
HX90N
R
GRAFOAM
Graftech
tional
Zero
TM
TM
Shrink
Zero
be
For master's
coated
To
with carbon
Laminated
ial
Core mater-
Machined
Ceramic block
Polyurethane foam
Low
High
MB5000
Polyester
Low
Coal
RM2000
Vinylester
Shrink
Resin
Vacuum in-
OptiPLUS
Postcure
High
RM3000
R
CFOAM
CB1100
hand lay-up
and
TM
Machined
Machined
Machined
Res.
Advanced Composites Group
Touchstone
BBC Products
Spray
Laboratory
Nord Composites
Spray
and
Nord Composites
and
hand lay-up
Spray
Composites
Epoxy
185
fusion
R
Toolfusion
Benzoxazine
Infusion
Cook
Adv.
hand lay-up
Airtech
Beta prepreg
Autoclave
hybrid tool
TM
High
Invalite
Invar and composite
ConnexSys
and Polymers
Adv.
Materials Group
Airtech
Materials Group
Remmele
Engineering
28
4 MATERIALS FOR MOULDS
4.9 Carbon foam
4.9 Carbon foam
CFOAM is a rather new technology.
The material is non-combustible,
and is made from coal, has a CTE close to composite and is then good for
mould production.
The material contains pores. A way to seal them and
R material and cure. It will then
make a good surface is to apply HexTOOL
need to be machined, but the rst part does then not has to be perfectly
machined [16].
Anette Sæter tested in her master thesis [32] two dierent
types of carbon foam, CFOAM and GRAFOAM, and it seemed promising
to use as mould materials. KONGSBERG have after that investigated a bit
more, and it performs well, but it absorbs too much moisture, Fred Simonsen
R
told. It was the intension to use GRAFOAM together with HexTOOL , but
R
the technical support in HexTOOL
will not support any use of these two
R
materials together, since the foam can fail during cure of the HexTOOL
R
material, or during use later [Email from Hexcel
forward by Tor Sigurd
Breivik].
4.10 Concrete/ Ytong / Siporex
Ytong is actually a building material, but can be machined and used as
master moulds with low material cost.
Before use it needs many hours of
drying. It is some kind of porous concrete material, contains a lot of air, so
it is lighter than in the normal form of concrete. It needs dierent layers of
coating after machining, before use. It is quite brittle so it is not unlikely
that it is not reusable after cure [33],[KONGSBERG].
4.11 Wood
Wood is a quite known in one form for all of us, and usually has a low
cost. It can be used for mould tools, but then usually for master moulds due
to it's softness. One of the most expensive sorts is one of the easiest types
to work with due to its stable and close grained timber, Mahogany. It might
distort during heat up and cool down [33, 4].
4.12 Tooling board
Ebaboard is one of many good tooling board products; they are usually
used for master moulds and for other applications for the tool making industries. It is a resin based material that is perfect for being machined to the
right shape. The weight is high, it is quite expensive as well as high CTE.
There is many dierent products for dierent use, nish and purpose [34, 33].
29
4.13 Epoxy paste
4 MATERIALS FOR MOULDS
Figure 10: Machining of Ebaboard block at NTNU
[Photo: Nina Thorvaldsen]
4.13 Epoxy paste
Epoxy paste exists in many dierent resin types and application methods.
One of the methods is to make dough with hand layup of glass bre and resin
on both sides. Often used together with some kind of bre for better strength.
Curing is done in room temperature. There are types both for low and high
cure temperatures. Hysol is one of Henkels series of epoxy paste [35].
30
31
1100
Low
Med-high
Low-med
Med
Low
Low
Mid
High
Low-med
Low
Low-med
Low-high
High
High
Low-med
size
limita-
Not
durable
hogany
Ma-
[29]
material
balsa,
master,
Plywood,
As
gile, for master's [36]
Absorbs moisture, fra-
Absorbs moisture, [29]
tions [2, 9]
Durable,
Need master mould
Time consuming [35]
Not found
450-1760
Low
Low
High
Med
Low-med
[34]
93
Not found
90-600
115-535
272
8900
Low
Epoxy pasta
35-109
Tooling
0.052
0.045-0.138
0.25-25
72.6-77.8
1900
High
Need master mould [9,
trol [2, 29]
board
3.6-21.6
Wood
Plaster
/
10
Concrete
Ytong
4.86
Carbon foam
/
11.9-13.3
Nickel
3.17-4.33
Medium
Low-high
coating
mould
Tight dimensional con-
as
[29]
12.6-23.4
epoxy
Low
High
High
[29] TiN
Durable,
[2, 29]
steel
durable
Fair durability [29]
Glass bre /
1730
High
High
High
High
High
High
Comment
Low therm mass [2, 29]
57.6-125
1500
Low
High
High
Med-high
High
Cure
2.2-3.6
3.46-6.63
1600-3900
High
High
Low
High
Production
Cost
Graphite
0-9
Carbon bre
1.44-11.5
5220
8140
7640-7890
2810
Material
2]
0.9-8.1
Ceramic
19
10.15
14.4-42.4
173
ρ [kg/m3 ]
Density
/ resin
9.4
0.63-2.5
Titanium
R
10.2-14.5
Steel
Invar
23
Aluminium
κ [W/m ◦ C]
Thermal
α [ · 10−6 / ◦ C]
Material
Table 6: Material selection
4 MATERIALS FOR MOULDS
4.13 Epoxy paste
4.13 Epoxy paste
4 MATERIALS FOR MOULDS
32
5 FROM REQUIREMENTS TO DESIGN
5
From requirements to design
The mould design is in close relation with the part design. The material
used in the part has big inuence on the material in the mould and the
same applies for production method. It is not possible to consider only one
requirement individually.
To select the right material, and how it should
be produced are in close relation. The master mould and the mould are as
important as the part itself.
Often are the parts shape and number of produced parts overriding requirements in the design process [9].
KONGSBERG has, as mentioned earlier high requirements towards tolerances, so the stability of the mould is important.
They want to control
most of the processes, so making the mould is one thing they want to do
them self. They want the mould to be light, easy to handle, possible to cure
in the autoclave together with other moulds made out of composites. This
means that to make the mould out of metal is maybe not the best solution.
Listed below are KONGSBERG's requirements for the
Ω-
and C-shape to-
gether with how materials from section 4 can fulll these.
Release part
The shape of the
Ω
mould. In this case the
a proper
Ω
and the C are so they can be made by a one piece
Ω is actually a half circle with anges.
If it had been
with opening smaller than the biggest width, a two piece mould
must have been considered, this if the part could not have been slided out.
All materials in table 6 are applicable.
Coecient of thermal expansion
KONGSBERG wants this to be matched with the CTE of the produced
part. The part will be made with a typical woven carbon bre prepreg. The
CTE for these are low, the mould material should be the one with the best
matching. Since they want a light material with CTE close to the part, it is
wise to rst consider a composite mould. Materials that are closest in CTE
R and some types
is carbon bre/resin, carbon foam, graphite, ceramic, Invar
R is not light.
of wood, but Invar
Dimensional accuracy and stability
Dimensional accuracy and stability is one of KONGSBERG's main criteria. The mould will need some kind of support structure for layup, which
can be used as stabilizing tool during cure as well. For all of the materials
mentioned in section 4 this is a challenge, some more than others, like wood.
Some, like graphite is stable with thick cross sections, but might be unstable
if the thickness of the mould is too small. For resin types, the temperature
must be kept under
Tg
for being stable.
33
The materials with low CTE are
5 FROM REQUIREMENTS TO DESIGN
more stable than with high. Ceramic for example have very good dimentional
stability.
Hold vacuum
The part must hold vacuum. On these two parts may a envelope bag be
used. The because of small size. For larger structures, it can not be based
on that. All of the materials can achieve vacuum tightness with help form
for example resin.
Finish
KONGSBERG want to have a good surface nish on the part.
They
want the outside of the part to have the best surface. Which leads to female
mould, and male master if that is needed. Trim lines and center points are
applicable for the best location of the part in the mould. These criteria can
be complied by any material.
Durability
The cycles are desired to be as many as possible, at least 200. The only
materials that don't fulll this is wood, ytong, tooling board and epoxy paste.
Metals, especially steel can take many curing cycles.
Environment, health and safety
High priority are on the health and safety for the workers. It is desired
to be able to do the layup without gas masks. For many prepreg types this
can be done. Concerning the machining must the dust have to be evaluated.
For the environment is it desired to have a mould with fast heat-up and
cool-down rate that can take many cure cycles. For resin types these things
has to be looked up for each type. The materials without resin are sucient.
Weight
KONGSBERG among others want a light mould. It will be transported,
and the heat-up rate is desired to be as short as possible. These two moulds
are quite small so the weight have a natural limit, but for bigger parts this
is a real issue. Here all the metal moulds falls out.
Costs
Low cost is desireble, but not the most important requirement. Due to
this, it might be a good idea of using a known durable and stable method
and material, even if it has a higher cost. There are not that many materials
with both low material and production cost. Ytong, wood, epoxy paste and
glass bre can have a low cost, the most of these materials have already been
excluded by other requirements.
Machinability
If the master is rough, the mahchinability of the mould material is important. The machinability to a material depends much on the quality, it usually
exist more than one type. One of the material with poorest machinability is
ceramic.
34
5 FROM REQUIREMENTS TO DESIGN
Repair and modify
KONGSBERG want to be able to modify their moulds. Metals can easily
be machined down. There is possible to welded parts on, but it might lead to
pores. Ceramics are dicult to repair and modify. The rest of the materials
are possible to machine and add parts by adhesion.
The adhered surface
might be waker then the rest of the part, depending on the material, the
adhesion might behave dierent to heat.
There are individual dierences
of how machinable they are. With for example laminates with long bres,
machining can cause unsymmetrical stresses, but also vacuum leakage along
the bres.
Heat and pressure
The mould will be used in autoclave with temperatures up to
180 ◦ C.
Wood, tooling boards and epoxy pasta can have problems with the temperature, some resin types as well.
Materials lifetime
If the mould is made out of composite, the layup and bagging of these
parts will take from 3 to 5 days before they are cured. For these small parts,
the material life time will not going to be a problem. But for bigger parts,
where the layup may take more than a working week, it can cause diculties
for some prepregs. Resin for infusion are mixed after the plies are layed up,
so that is not a problem.
Maintenance
KONGSBERG have good routines for mould care, and want to use the
same methods that is used today. It is desired to use as little time as possible
on each part. For any material to use, mold care have to be executed.
Adaptive work on part
The adaptive work on a mould are today a time consuming process.
KONGSBERG want to use less time on this. The material have to be either
master mould that can be ne machined or a mould material that can be
ne machined.
Curing conditions
The curing are to be done in autoclave with other composite moulds.
This leads to a preference for composite moulds.
Lead time
KONGSBERG must know that it is possible to receive enough material
when they need it. This is can be dicult for some carbon bres types. For
all materials this depends on the supplier and how big amount.
KONGSBERG already have experience with HexTOOL
R
M61 and want
to compare it with another material. Beta prepreg was as mentioned demonstrated from Airtech, with good result. A decision of make another mould
35
5 FROM REQUIREMENTS TO DESIGN
with these two materials was taken. Looking at the dierent requirements,
each are fullled in a sucient way. To see material properties for the materials, look in section 6.1.1 and 6.2.1. They have many of the same qualities
like low CTE, light, can be cured with composite moulds and ability to be repaired and modied, with their individual dierences. Beta can for example
be stored in room temperature for long time, while this is not the case for
the M61 material.
The weight of the Beta are 36% lighter than the M61 type.
One thing that are not mentioned in Betas data sheets [37] are the materials odour of degasication.
The safety data sheet [37] have the same
requirements for protective equipment as for other prepregs, and are not
rated as more injurious to the health, but people have reacted on it.
R
In the two materials data sheets they are rated as machinable. HexTOOL
are in general a more tested product, and the surface after machining turns
out good. The shape have shown tendency of change after machining.
36
6 MOULD PRODUCTION
6
Mould production
From the results of the dierent requirements, KONGSBERG's needs
and experience, was it decided to make tests for moulds with two dierent,
but still quite similar materials.
of moulds.
There has been made two dierent types
One is shaped as a half circle with anges, after this referred
to as Omega (Ω), made of ytong, see gure 11. The other mould is a part
that will for the rest of the document be called C-shape, see gure 12 to 15.
This is made on an aluminium master mould. They have both been made of
the same two dierent materials, and the same production method has been
used. One of the materials is a known product for composites moulds, this
R M61, and is produced by Hexcel
R . The other type is
is called HexTOOL
called Beta Prepreg, produced by Airtech and contains a dierent resin type
called benzoxazine. For material data for these two materials see table 8 to
11.
Length
Height
Width
Figure 11:
Width,
height and length of a
Ω
mould during layup at
KONGSBERG
[Photo: Nina Thorvaldsen]
Table 7: Approximate sizes of moulds given in mm
Shape
Ω
Material
HexTOOL
Beta
C
HexTOOL
Beta
R
R
Width
Hight
Length
200
140
450
200
140
550
400
250
300
400
250
300
37
6.1 HexTOOLR
6 MOULD PRODUCTION
6.1 HexTOOL R
R M61 is a prepreg type that contains a bismaleimid (BMI)
HexTOOL
resin.
The ply contains random oriented strips of chopped unidirectional
carbon ber. It has extensively been used for producing composites moulds.
The thickness of a ply is approximately 1.27mm, but this varies quite a lot
over the ply. Some places has holes and other places, thick parts that are
up to 2mm. If a thick mould should be made, it does not require that many
layers to achieve the wanted thickness. The material is quite hard to work
with in normal room temperature, especially to cut. It is sti, and needs to
be heated with a heating gun to be able to shape it correctly around edges
and corners. When the ply is heated it becomes very ductile and exible. It
then forms well by using hands or forming equipment to guide the ply into
the right places.
R is the material KONGSBERG is using today for mould pro
HexTOOL
duction.
This has given various results and satisfaction.
One of the di-
culties has been the lack of knowing how it deforms.
6.1.1
R
Material data for HexTOOL
All of the material data are collected from [33], and are listed in table 8
and 9.
R M61 [33]
Table 8: Uncured and cured material data for HexTOOL
Property, uncured
Value
Fibre
Carbon
Resin
Bismaleimid
Nominal resin Content
38 %
Nominal bundle size ( prepreg strip size)
8.0mm x 50mm bundle, quasi
isotropic orientation
2
2000 g/mm
Nominal ply areal weight
◦
Storage life, (−18) C or below
12 months
Property, cured
Cured
ply
thickness,
Value
based
on
nominal
prepreg properties
ations)
◦
Out of autoclave post cure
Coecient of linear thermal expansion
Minimum initial cure temperature
Tg
1.27mm (big individual vari-
Glass transition temperature (Dry / wet)
Maximum service temperature
38
220 C
4 · 10−6 / ◦ C
190 ◦ C
275/230 ◦ C
220 ◦ C
6 MOULD PRODUCTION
6.2 Beta Prepreg
Table 9: Mechanical Properties for HexTOOL
Property
Temp.[
◦
C]
R
M61, for dry material [33]
Method
Value
Unit
Tensile Strength
23 / 180
EN2561
260 / 210
MPa
Tensile Modulus
23 / 180
EN2561
41 / 40
GPa
Compression Strength
23 / 180
EN2850B
300 / 270
MPa
Compression Modulus
23 / 180
EN2850B
32 / 30
GPa
23
EN2562
380
MPa
23
EN2562
38
GPa
23 / 180
EN2563
50 /43
MPa
Flexural Strength
Flexural Modulus
Short Beam Shear Strength
6.2 Beta Prepreg
Beta prepreg is a new composite tooling material on the marked. KONGSBERG had some material for testing to see if this a suitable material for their
production of composite tooling. This is a woven material, which makes it
easy to predict the nal laminate thickness. One of the big advantage of the
Beta prepreg is it's tack.
and it stays there.
It is easy to apply the dierent plies to another
This may be a disadvantage as well since it sticks to
everything. The plies are fair to cut with a laminate scissor.
6.2.1
Material data Beta Prepreg
All the material data on Beta Prepreg BG-6 are collected form [37], and
are listed in table 10 and 11.
6.3 Layup of prepregs for autoclave cure
To achive the best possible result of the nal product, both the recommendations from the manufacture and experience are important. The time
it takes to lay up a part depends a lot on the complexity of the part, how
many plies, the specied accuracy, the tting of the plies and the experience.
First step:
The mould has to be perfectly cleaned and inserted with the
necessary number of release agent, and dried. Some of the prepregs are easier
to form into the right shape if the mould is a bit warm, so this is sometimes
done before the rst ply.
Second step:
It is extremely important to get the rst ply perfectly aligned
and into all corners of the mould. This among other reasons to avoid bridging
and collection of resin. A debulk is always required after the rst ply. Here
it is normal to use a release lm, breather and vacuum bag.
39
6.3 Layup of prepregs for autoclave cure
6 MOULD PRODUCTION
Table 10: Uncured and cured material data for Beta Prepreg [37]
Property, uncured
Value
Fiber
Carbon
Resin
Benzoxazine
Nominal resin content
37
Weaving style
6K 2x2 twill,
2
±3
%
orientation
365 g/mm
Nominal ply areal weight
◦
Storage life, 25 C or below
◦
Storage life, (−17) C or below
6 months
12 months
Property, cured
Value
Cured ply thickness
0.36mm
−6
Coecient of linear thermal expansion
Minimum initial cure temperature
Out of autoclave post cure
Tg
0/90◦
Glass transition temperature
Maximum service temperature
2.7 · 10 / ◦ C
185 ◦ C
218 ◦ C
251 ◦ C
218 ◦ C
Table 11: Mechanical Properties Beta Prepreg BG-6 [37]
Property
Temp.[
◦
C]
Method
Value
Unit
Tensile Strength
22 / 185
ASTM D 3039-08
800 / 740
MPa
Tensile Modulus
22 / 185
ASTM D 3039-08
64.3 / 62.3
GPa
Compression Strength
22 / 185
SASMA 94-1R
720 / 430
MPa
Compression Modulus
22 / 185
SASMA 94-1R
59.9 / 60.6
GPa
Flexural Strength
22 / 185
ASTM D 790-03
1900 / 610
MPa
Flexural Modulus
22 / 185
ASTM D 790-03
58.8 / 56.0
GPa
Third step:
The rest of the layup is done with the specied ply direction,
and debulk as often as needed.
Fourth step:
Then it is time for the nal bagging. Here some materials
require a resin trap to keep the resin in the part and not all over the inside
of the bag. Resin leak might also lead to bag burst. If there is made a resin
trap, it also need an inner bag. This should not be airtight, so small strings
of glass bres are applied around the edge, see gure 12.
In this case the
inner bag was the realise lm, see gure 15. Thermocouples are applied to
know the temperature of the part. Vacuum valves are applied through the
bag. For smaller parts like this, two is sucent.
40
6 MOULD PRODUCTION
6.4
Sealant
tape for
inner bag
Ω
shape
Thermocouples
Glass
strings
Figure 12: Thermocouples (Tc ), glass ber strings and sealant tape for inner
bag on the C-shape mould
[Photo: Nina Thorvaldsen]
6.4
Ω
shape
The master material of the
Ω
shaped mould was ytong which was coated
with dierent layers to protect the ytong, making it possible to remove mould
from the master mould and obtaining a slightly better surface nish. Both
R and Beta Prepreg was laid up on this type of plug.
materials, HexTOOL
The approximate size is given in table 7.
The thickness of the mould was
approximately 10mm, they where choosen to be that thick for the ability to
machine them after cure.
The layup of the mould in HexTOOL
R
material was done by people in
KONGSBERG. The manufacturer's user guide [33] was used as assistance
to get a good result. It was used 8 plies for the layup. The nal thickness
was 10mm
±2mm.
The lay up of the Beta prepreg was mostly done by people from Airtech, as
a part of promoting the new material. It was done with help and observation
of a team from KONGSBERG and the writer.
curing can bee seen in gure 11, 4a and 4b.
Pictures of the layup and
This was also done following
the manufacturer's user guide [38] and are more described in part 6.3. It was
used 28 plies, which gave a thichness of 10mm
±0.5mm.
There were used
two thermocouples to maintain the right temperature during cure, and two
vacuum valves to maintain the vacuum. This is recommended for parts at
this size.
41
6.5 C-shape
6 MOULD PRODUCTION
Figure 13:
Ω
mould and master mould after cure
[Photo: Nina Thorvaldsen]
6.5 C-shape
For the C-shaped mould the machining of the master mould was outR aluminium, which is more described
sourced. The material was CERTAL
in the part about aluminium, section 4.1. This is an aluminuim type that is
thermally stable, and often used for moulds. This is an advantage when the
material is being machined and heated and cooled. When the master mould
had arrived KONGSBERG, it was released with frekote B-15 and 44 by the
instructions given in their respective technical data sheets [39, 40].
Figure 14: Layup of C-shaped M61
[Photo: Nina Thorvaldsen]
R material was done by the author
The layup of the mould in HexTOOL
R
with assistance from people at KONGSBERG. The plies of the HexTOOL
are approximately 4 times thicker than the Beta prepreg, so to achieve the
42
6 MOULD PRODUCTION
6.6 Parts made in C-shape mould
most similar nal thickness there where used 5 plies. HexTOOL
R
was done
in 2 days, and half a day with bagging. Figure 14 is during layup, the rear
part shoves a uneven surface after demoulding. In front the stiness of the
ply before heating is showed. Three thermocouples was used, one was in the
place where the aluminium mould was thicker than the rest, and the two
others located where the mould had a more average thickness, picture of this
on the Beta perepreg can be seen in gure 12.
After a free standing post
cure, the mould was sanded. Nothing was used for sealing the pores, to gure
out how it works without. It was coated with release agents.
The layup of Beta prepreg was done mainly by the author, with good
◦
assistance of KONGSBERG employees. The layup was 15 plies of 0/90
of woven layers. The manufacturer's specication [38] was followed during
the production and curing. The lay up took 4 days including bagging. The
curing was done in an autoclave. After demoulding, the mould was postcured
free-standing. Then a layer of pore sealing was applied. This works good on
small pinholes and small irregularities, it gives a good surface and makes it
easier to release the part form the mould after cure.
The two moulds were then sanded to a nish of 2000 grit paper.
The
moulds were coated with frekote, as the aluminium master mould was.
Figure 15: Inner bag, during bagging of the C-shape
[Photo: Nina Thorvaldsen]
6.6 Parts made in C-shape mould
The layup of this part was done by the same materials as if it should
◦
◦
have been a proper part. Woven carbon bre fabric with 0/90 and ±45
43
6.6 Parts made in C-shape mould
6 MOULD PRODUCTION
Table 12: Number of plies, nal thickness and weight of the C-shape
Material
HexTOOL
Beta
Plies
Thickness [mm]
Weight [g]
5
4.50-8.70
1942.55
15
5.12-5.44
1656.45
R mould and one in
was used. There was made one part in the HexTOOL
the Beta prepreg. Most of the layup was done by people in the layup team
at KONGSBERG, but also some of it by the author.
Some of the shapes
on the mould are hard to follow by one ply, since it is double bent and with
90◦ bends on each side. So to be able to get the ply into the mould, there
had to be made some cuts in the laminate. This was lled with small pieces
of fabric in the same directions. All types of cutting bres in a layup will
weakened the strength.
Figure 16: Layup of part in M61 C-shaped mould at KONGSBERG
[Photo: Nina Thorvaldsen]
44
7 FE ANALYSIS
7
FE analysis
Finite element analysis is a tool used to evaluate the strength of the struc-
ture. The program used for the analysis is Abaqus/CAE-6.10-2, which is a
software application for nite element analysis and computer aided engineering. The CAE version was used, which is a Complete Abaqus Environment.
This provides a simple but consistent interface for creating, monitoring and
evaluate results from Abaqus Standard and explicit simulations.
The pro-
gram is divided into dierent modulus where values like geometry and material properties, generating of mesh of the part are applied to get the desired
simulation[41].
One of the main challenges in mould making is, as mentioned earlier,
the spring-in phenomenon that appears during cure. In this nite element
analysis the spring-in has been analyzed. The main focus has been on the
mould, but also master mould and part has been applied.
From [25] it is expected that a part made on an aluminium mould, which
have higher CTE, will spring more than if it were made in a carbon bre
mould. It also concludes that a C-shaped part spring more than a L-shaped.
◦
It is normal to calculate with a draft angle of 1 − 2 , to be able to remove
part from mould [9, 4].
7.1 The process
To be able to make the analysis for curved shapes, it is a good idea to
make a simple plate model of the laminate before making a more advanced
shape. With a plate is it easy to see if the boundary conditions are correct.
In gure 17 and 18 one of these tests is shown.
In x and z directions the
displacements are the same, and in y it is dierent.
The plate test was
done with BMI and CFRP materials in table 13, shown here is CFRP. The
smallest, solid part is after cure and shrink, the bigger, shaded part is the
basis.
The thought is if only one element is considered locally as a block in
x-y-z directions, the bres have strength in one direction and are weaker in
the two resin direction. The laminate has the same thermal properties in the
resin directions and a dierent along the bre. Since the laminates are either
0/90◦ , ±45◦ or chopped bundles in all directions, they will have the same
properties in the two bre directions, and then it will only be one direction
for the resin.
The resin usually has a much higher coecient of thermal
expansion than the bre. Many of the carbon bre have a negative value,
see table 13, while the resin has a positive. This is one of the main reasons
for the spring [18].
45
7.1 The process
7 FE ANALYSIS
(a) U1, x-direction
(b) U3, z-direction
Figure 17: Analysis of a plate
Figure 18: Analysis of plate U2, y-direction
If it is only the thermal expansion factor that is dierent in two directions,
the plate has the same geometries and material properties in the two directions. The temperature dierence was applied over the whole plate, which
leads to the uniform shrink of the plate. The corners was fasten, all four in
y-direction, two in x-direction and two in z-direction, for gure 17a to 18.
In gure 20a and 20b it can be seen how a laminate with various orientations are connected to coordinates.
This is how it is applied in Abaqus.
They are inspired by gures in [18].
Material data that have been used in these analysis are listed in table 13.
The material data for CFRP is for unidirectional bres which can be seen in
◦
gure 20a. To orient the rbers in the right direction, in this case 0/90 as
in gure 19, the dierent directions have to be applied when the composite
laminate is created.
Composites are often oriented in dierent directions,
so to be able to calculate dierent properties, the angle
calculations.
46
θ
are used in the
7 FE ANALYSIS
7.1 The process
Z
X
Y
Figure 19: Illustration of a
0/90◦
laminate in Abaqus
X
1
Z=3
the resin
direction
X=1
along
the
fibres
Y
Y=2
transverse to
the fibre
2
(a) UD laminate
(b) UD with θ orientation of bres
Figure 20: Fibre orientations
47
7.1 The process
7 FE ANALYSIS
Table 13: Material properties used in the analysis
Material
CFRP
BMI
Aluminium
Ytong
Symbol
Value
Unit
Ref
E11
E22 = E33
ν12 = ν23
ν31
G12 = G13
G23
ρ
α11
α22 = α33
E11 = E22 = E33
ν12 = ν23 = ν31
G12 = G13 = G23
ρ
α11 = α33
α22
E
ν
ρ
α
E
ν
ρ
α
150.76
GPa
[23]
7.93
GPa
for
0.2525
all
0.3
except
3.7
GPa
2.5
GPa
3
1300
−6
−0.8 · 10
27.62 · 10−6
kg/m
◦
/ C
◦
/ C
2.0
GPa
0.49000
[29]
Per Olav
Kristiansen
0.8
GPa
800
−6
4.9 · 10
4.9 · 10−5
kg/m3
◦
/ C
◦
/ C
72
GPa
0.33
from
KONGSBERG
[28]
and
2810
−6
kg/m3
◦
/ C
[29]
2
GPa
[36]
23 · 10
0.3
115
−6
10 · 10
48
ρ
and
kg/m3
◦
/ C
[29]
7 FE ANALYSIS
7.2 Analysis of the Ω mould
7.2 Analysis of the Ω mould
There has been performed a temperature analysis, with temperature difference as load. With one of the methods for thermal analysis, like coupled
temperature displacement, some things are not permitted within Abaqus.
The temperature for example can not be predened, but must be applied as
an boundary condition. While by using static/general analysis, the temperature have to be used as predened [41].
With help from KONGSBERG, one solution for the analysis has been
made.
The theory is to only apply thermal load, and then the part will
spring since it has dierent thermal expansion in the dierent directions.
This was tested out on the BMI material listen in table 13 and worked well.
It is absolutely desired to use the through thickness expansion.
It was
then chosen to build the model as a solid and not a shell, though it is recommended for composite parts to use a shell method unless the through
thickness is of interest[41].
Predened elds was here used as temperature. It will lead to thermal
strains in a stress/displacement analysis when there is a temperature dierence between a predened temperature eld and any initial temperatures,
this if the CTE is given [41].
There are basically two dierent methods of modeling that have been
investigated, if not considering shell vs solid. The shell method was tested,
but results are not included since the through thickness deformation is desired.
The rst method is to use coupled temperature displacement with
dierent temperatures as boundary conditions. The structured mesh is then
C3D20RT, which is a 20-node thermally coupled brick, triqadratic displacement, trilinear temperature and with reduced integration.
The other method is a more normal static/general analysis with predened temperatures.
The start temperature is applied in initial and the
dierence in temperature is applied in step, which is
∆T. This gave the most
promising results with the plate test, so this method was chosen for the rest
of the analysis.
The material orientation have been applied so the normal are turning
outwards the whole part. This will give the desired sets of squared elements
with the stacking of the plies in the right order. See gure 22.
◦
It has been made composite layup with four plies, in 0/90 , this means
◦
◦
two in 0 and two in 90 , see gure 19. When a laminate of woven fabric
are made in Abaqus it has to be made as two plies. Four plies was created.
These where made symmetric, which is the same as 8 plies. The mesh has
been divided in four elements in the hight, so each element contains 8 plys,
which in total give 32 plies. The mesh of the
49
Ω
can bee seen in gure 22.
7.2 Analysis of the Ω mould
7 FE ANALYSIS
Figure 21: Material orientation of the
Ω
part
Figure 22: Meshed part, four elements in the thickness direction
Figure 23: Selecting of nodes on the
50
Ω
7 FE ANALYSIS
7.2 Analysis of the Ω mould
In gure 24, 25 and 26 it is possible to see how the shape crimps after
◦
cure. This is from 180 C and cooled down to room temperature. The
smallest, inner part is the coled one, the outer shaded one is before cooling.
The material used in the analysis is CFRP in table 13. In table 14 can the
dierent values across the shape be seen. To see where the dierent points
are, see gure 36, note here y and z have changed places.
The table and
gures shows a signicant displacement in the x-direction. The z-direction
has a change, but less. The maximum displacement is in x-direction, and are
◦
4.946mm, which is 3.5%, or 1.03 .
In table 14 results from two analysis have been assembled.
The two
column to the left are for the rst analysis, this is only the mould. Figure 24
to 26 displays these. The four column to the right is for the second analysis.
This is of a mould with a part inside. This can be seen in gure 27, where
only the deformed shape is shown. The mould and part was assembled, and
the analysis was done with both parts. The maximum displacement on the
◦
moud was 5.394mm, which is 3.8%, or 1.13 . The maximum displacement of
◦
the part was 4.054mm, which is 2.8%, or 0.84 .
Figure 24: Analysis of the
Ω
in U1, x-direction
The analysis in gure 27 is done by the same method as for the mould
in gure 24- 26. The more detailed numbers are presented in table 14. The
numbers shows a similar displacement of these tree shapes. The part with
master mould and mould has 3D elements, C3D20R: a 20-node quadratic
◦
brick, reduced integration. Initial temperature at 180 C was applied with
51
7.2 Analysis of the Ω mould
7 FE ANALYSIS
Figure 25: Analysis of the
Ω
in U2, y-direction
Figure 26: Analysis of the
Ω
in U3, z-direction
52
7 FE ANALYSIS
7.2 Analysis of the Ω mould
Table 14: Displacement of the
Point
in arc
Ω,
FE analysis
Displacement, [mm]
Mould alone
Mould with part
Part in mould
Nr
X
Y
X
Y
X
Y
A.1
-0.004
0.006
-3.145
0.001
-3.099
-0.035
A.2
-3.143
0.006
-3.136
0.007
-2.522
0.120
A.3
-3.102
0.104
-0.355
0.144
-2.157
0.263
A.4
-0.700
0.255
-0.834
0.285
-1.889
0.440
A.5
-1.040
0.412
-1.183
0.486
-1.687
0.650
A.6
-1.285
0.592
-1.455
0.761
-1.591
0.813
A.7
-1.527
0.905
-1.552
0.935
-1.560
0.895
A.8
-1.562
0.991
-1.578
0.997
-1.548
0.878
A.9
-1.574
1.012
-1.609
0.917
-1.501
0.766
A.10
-1.641
0.857
-1.719
0.733
-1.401
0.616
A.11
-1.803
0.643
-1.967
0.490
-1.224
0.438
A.12
-2.019
0.401
-2.249
0.260
-0.955
0.261
Piont
Displacement, wings, [mm]
Nr
X
Y
X
Y
X
Y
W.1
-0.122
0.140
-3.137
0.003
-0.010
-0.036
W.2
-0.001
0.001
-3.026
0.124
-3.098
-0.032
W.3
-3.156
-0.000
-0.013
0.000
-0.129
0.041
W.4
-3.139
0.0317
-0.124
0.120
-0.007
-0.040
W.5
-3.035
0.127
-3.139
0.002
-3.101
0.029
W.6
-2.215
0.344
-2.705
0.165
-0.670
0.142
W.7
-2.329
0.290
-2.885
0.134
-0.504
0.096
W.8
-2.454
0.242
-0.003
-0.000
-0.324
0.061
W.9
-2.589
0.201
-0.006
-0.001
-0.068
0.026
W.10
-2.893
0.140
-0.009
-0.001
-0.014
-0.024
53
7.2 Analysis of the Ω mould
−160 ◦ C
7 FE ANALYSIS
in step1. 20-nodes is with quadratic elements, without is a 8-node
element.
Figure 27: Analysis of the
Ω
with a part, U1 x-direction
The two analysis of master mould and part showed in gure 28 and 29
was carried out by the same method as the mould with part in gure 27.
Table 18 in appendix B presents the results from gure 28 and 29. The
displacement on the aluminium master are bigger than for the ytong master.
The displacement of the two mould on top are to be considered as the same,
there can have been small individual dierences in the selection of nodes.
It was expected that the part cured on the aluminium master would had
a lager displacement than the one at the ytong master.
This means that
the distribution of temperature and expansion between the master and the
mould most likely not are done correctly.
Due to time consuming process
of analysis and processing data, there were not found a better solution. It
indicates the reason for equal numbers for the dierent parts in table 14.
54
7 FE ANALYSIS
Figure 28: Analysis of the
7.2 Analysis of the Ω mould
Ω
part made on a aluminum master mould, U1
x-direction
Figure 29: Analysis of the
Ω
part made on a ytong master mould, U1 x-
direction
55
7.2 Analysis of the Ω mould
7 FE ANALYSIS
56
8 MEASUREMENTS
8
Measurements
Eight parts have been made in total. Two master moulds, four moulds,
and two are parts made in two of the moulds.
As described in section 6,
two dierent types of materials have been used for the moulds. These two
materials have been made on two dierent shapes. In this section the results
will be presented from the measurements of these parts. The intension was to
nd out which one of these two materials has the lowest spring-in, and how
much the nal parts in these mould deforms. The number of produced part
is not enough to give a nal conclusion, but it will give some ideas. All measurements that are reported is done in an ZEISS CMM machine (coordinate
measure machine) at KONGSBERG, see gure 30.
It has to operated by
qualied people with a certicate of apprenticeship in measurement.
This
machine has a big working load. This is the reason for why new measurements have not been carried out when it was discovered something with the
measurements that could have been done dierently.
Figure 30: The C-shaped mould with Beta prepreg during measuring
[Photo: Eirin Holmstrøm]
8.1 Measurements of the two Ω moulds
The outer surface of the two materials in the two
ent.
Ω
moulds are dier-
This is one of the reasons why it is expected to have dierent res-
ults. The Beta prepreg has an even thickness over the whole part, while the
57
8.1 Measurements of the two Ω moulds
8 MEASUREMENTS
R has rather big individual dierences of up to
HexTOOL
±2mm
on a 6mm
thick part. Both moulds have been made on ytong. The inside of the two
moulds has approximately the same roughness, of
±0.5mm.
A rst rough
measurement was done using a slide caliper. This showed a result of approxmetly 4mm spring-in in total, which means 2mm on each side. This was for
R had
the mould made of Beta prepreg. The mould made with HexTOOL
a spring-in of 7mm, this is 3.5mm on each side. The spring was measured
more accurately with the ZEISS CM machine.
The interest is to nd out
how much spring-in there has been. To see if the spring is constant over the
whole curvature, and if there is that big a dierence for the two materials.
This will be compared to the CAD-model of the ytong master mould.
R
(b) Ω made of HexTOOL
(a) Ω made of Betaprepreg
Figure 31: Plot of the measured
Ω
shapes
The measurements were done with 10-12 points in the arc and 4-5 points
on each of the wings.
Figure 31 illustrate with colours which points are
inside the tolerance and whats outside.
Green is zero, red is outside in
the negative direction, and blue in the positive. By looking at the plots in
picture 31 it can be seen that one of them is more out of tolerances than the
other. It also illustrates the tendency of smaller parts. This plot is from the
measurements done without the wings. One measurement was done after
this, where the wings on the part were measured as well.
The numbers
used in the report is from the last measurement, can be seen in table 15. To
look closer at where the dierent points were measured, see appendix C.
In gure 32 to 34 two dierent results of the measuring of the
Ω part can
be seen. This is a shape of cut number 3, 8 and 13 in y-direction. The black
line with small dots illustrates the CAD shape of the
58
Ω
mould.
The blue
8 MEASUREMENTS
8.1 Measurements of the two Ω moulds
line with circles is the mould made of HexTOOL
R
. The red line with a cross
R mould
is the mould made of Beta prepreg. The values of the HexTOOL
showed a oset in the z-direction of 5mm.
This can happen when part is
R has been shifted
placed in the measuring machine. The curve of HexTOOL
5mm lower in the z-direction. This has been done with all of the Ω shaped
R mould. This applies also for the results presented in table 15.
HexTOOL
A cut of the six points on the top left hand side from cut 8, can be seen in
gure 35.
C−shape, cut 3
20
0
−20
Z [mm]
−40
−60
−80
−100
−120
−140
−160
−350
CAD
HexTOOL
Beta
−300
−250
−200
−150
−100
−50
0
50
X [mm]
Figure 32:
Cut 3 of the two Ω moulds.
Maximum displacement for
R
◦
HexTOOL
was 3.099mm, which is 1.14%, or 0.68 . For Beta was the dis◦
placement 1.889mm, which is 0.69%, or 0.02
Out of what is known about the spring-in phenomenon is that the change
depends on the material and the bre orientation. A part will decrease its
various angles during cure.
This means for the
Ω
shape, the arc will be
smaller. This will push the edge of the wings downwards, when the model
is seen with the arc on top and the vings on the bottom. The spring in the
angle between wings and arc, will bend them slightly upwards again. From
the FE analysis, see gure 59, it should cross the original arc by having a
small part on the outside at one side and a bigger part on the inside at the
other end.
In table 15 are the maximum, minimum and average dierences from
the CAD part presented. These values are taken on 14 places along the yaxis, see gure 36 and appendix C for a better understanding of where the
R
points were taken. As the table shows, the mould made from HexTOOL
59
8.1 Measurements of the two Ω moulds
8 MEASUREMENTS
C−shape, cut 8
20
0
−20
Z [mm]
−40
−60
−80
−100
−120
−140
−160
−350
CAD
HexTOOL
Beta
−300
−250
−200
−150
−100
−50
0
50
X [mm]
Figure 33:
Cut 8 of the two Ω moulds.
Maximum displacement for
R was 2.624mm, which is 0.96%, or 0.28◦ . For Beta was the dis
HexTOOL
◦
placement 1.935mm, which is 0.70%, or 0.20
C−shape, cut 13
20
0
−20
Z [mm]
−40
−60
−80
−100
−120
−140
−160
−350
CAD
HexTOOL
Beta
−300
−250
−200
−150
−100
−50
0
50
X [mm]
Figure 34: Cut 13 of the two Ω moulds.
Maximum displacement for
R was 3.168mm, which is 1.17%, or 0.34◦ . For Beta was the dis
HexTOOL
◦
placement 1.223mm, which is 0.49%, or 0.13
60
8 MEASUREMENTS
8.1 Measurements of the two Ω moulds
C−shape, cut 8
20
0
Z [mm]
−20
−40
−60
CAD
HexTOOL
Beta
−80
−100
−310
−300
−290
−280
−270
−260
−250
−240
X [mm]
Figure 35: A section of cut 8 of the two
Ω
W.1
moulds
W.6
A.1
A.12
1-14
Z
Y
A.6
X
Figure 36: A schematic drawing of where the dierent measurements point
on the
Ω
have been taken
61
8.2 Measurements of the C shape
8 MEASUREMENTS
has a bigger spring than the Beta prepreg.
The maximum of the average
x-displacement in the arc is 3.8194mm and 0.1671mm respectively for them.
It also shows that the spring in x-direction are highest, as expected, closest
to the wings. The graph of the average displacement can be seen in gure
R is shifted 5mm lower
37. In these numbers as well the mould of HexTOOL
in the z-direction. It can also be seen that the Beta mould has more even
displacement.
Average Ω
20
0
−20
Z [mm]
−40
−60
−80
−100
−120
−140
−160
−400
CAD
HexTOOL
Beta
−350
−300
−250
−200
−150
−100
−50
0
50
100
X [mm]
Figure 37: The average form of the two Ω mouls together with the CAD
R is 3.8194mm and 0.1671mm for Beta
part, displacement for HexTOOL
In z-direction of A.5,A.6,A.7 and A.8 there are increased height, see table
R
15. In these points as well as in the dierent graphs, is the HexTOOL
shifted 5 mm lower as the graph in gure 34. A graph of the average displacements is found in gure 37.
8.2 Measurements of the C shape
The C-shaped aluminum master mould was measured against the CAD
le. The two moulds made on it was also measured. One of them was made
R M61 and the other of Beta prepreg. The production and
of HexTOOL
materials are more described in section 6 about mould production.
Two
carbon ber parts were also made in the two dierent moulds. These have
also been measured. Here also the layup is more described in section 6.6 and
the measurements in section 8.3.
62
8 MEASUREMENTS
8.2 Measurements of the C shape
Table 15: Maximum, minimum and average displacement of the
Ω
mould in
the whole y-direction, all measurements are in mm
Point
Displacement, x-direction, arc, [mm]
R
HexTOOL
Beta
in arc
Nr
Max
Min
Average
Max
Min
Average
A.1
5.514
4.729
5.172
2.184
0.703
1.631
A.2
5.786
4.451
5.201
1.636
0.724
1.252
A.3
5.101
3.256
4.264
1.078
0.066
0.614
A.4
4.208
2.900
3.604
0.534
0.014
0.263
A.5
2.654
1.385
2.026
-0.374
-0.065
-0.198
A.6
0.836
0.001
0.436
-0.208
-0.005
-0.092
A.7
-0.889
-0.381
-0.580
0.663
0.092
0.317
A.8
-1.129
-0.717
-0.890
1.012
0.627
0.796
A.9
-0.839
-0.369
-0.625
1.367
0.991
1.223
A.10
-0.369
-0.007
-0.004
1.558
1.054
1.346
A.11
1.906
0.467
1.381
1.642
1.193
1.419
A.12
2.789
0.059
2.154
1.998
1.159
1.684
Displacement, z-direction, arc
A.5
-0.273
-0.004
0.006
-1.160
-0.160
-0.538
A.6
-1.266
-0.062
-0.541
-1.401
-0.685
-1.143
A.7
-2.564
-0.512
-1.527
1.970
-1.260
-1.650
A.8
-3.438
-1.945
-2.894
-2.058
-1.626
-1.829
Point on
Displacement, z-direction, wings, [mm]
R
HexTOOL
Beta
wings
Nr
Max
Min
Average
Max
Min
Average
W.1
1.401
0.944
1.114
-0.152
0.008
0.031
W.2
1.242
0.903
1.085
-0.412
-0.015
-0.141
W.3
1.283
0.881
1.041
-0.631
-0.078
-0.194
W.4
1.018
0.630
0.714
-0.669
-0.165
-0.367
W.5
-2.865
-0.586
-1.281
-0.755
0.014
-0.237
W.6
-6.937
-4.986
-6.178
-2.329
0.016
-1.878
W.7
-1.376
-0.459
-0.908
1.432
-0.039
-0.632
W.8
-0.906
-0.003
-0.359
-0.878
0.036
-0.406
W.9
-0.769
-0.003
-0.303
-0.556
0.009
-0.130
W.10
-0.744
-0.160
-0.401
0.417
0.116
0.224
63
8.2 Measurements of the C shape
8 MEASUREMENTS
1.10
1.7
2.1
2.18
2.8
1.2
X
Z
Y
Figure 38: A schematic drawing of where the dierent measurements point
on the C-shape have been taken
8.2.1
Aluminium master mould
The machining of the master mould was done by another company as
mentioned earlier.
It was not delivered with a measurement report.
The
surface was not as the specied requirements. That two tings is why it was
decided to measure it.
These values show that there are dierences from
the CAD, see gure 39 and 40, as also seen by only looking at the part.
The comparison of the two moulds made on the aluminium plug are mostly
compared with the CAD part.
The values of aluminium master shows that there is a dierence of up to
2.3mm from the CAD part in the y-direction. The measurements was taken
mostly on the top of the mould and not all the way down, this means that
it might only be the corners that are smaller. One possibility is also that it
might have been a dislocation from its axises. It can be seen in gure 40 that
the top cure follows perfectly, so this is most likely not the case.
8.2.2
Moulds made in C-shape
R mould and the Beta prepreg mould
The points where the HexTOOL
are taken at the same places.
The intention was to match these with the
points taken of the aluminum master mould, but as it can be seen, they are
not at exactly the same places. This can be seen from comparing gure 39
with 42 and 43. From the various numbers there is a bigger depart on the
numbers in the x-direction, than in the two other directions. This dierence
is between 2 and 0,3mm, see table 16 and gure 42 to 47.
In gure 43 the dierence from CAD part and Beta mould can be seen.
The red points has number from +0.4mm and higher, the green points are
64
8 MEASUREMENTS
8.2 Measurements of the C shape
Figure 39: Plot of the various values of the Aluminium master mould
Aluminium master mould
20
CAD
Alu
0
Z [mm]
−20
−40
−60
−80
−100
−350
−300
−250
−200
−150
−100
−50
0
Y [mm]
Figure 40: Cut 1.10 on the C-shaded aluminium master mould, the total
displacement in y-direction is 0.2mm, which is 0.06%
65
8.2 Measurements of the C shape
8 MEASUREMENTS
The middle rerion in yz direction, C−shape, moulds
−20
−30
CAD
Alu
−40
Z [mm]
−50
−60
−70
−80
−90
−100
−350
−300
−250
−200
−150
−100
−50
0
Y [mm]
Figure 41:
Cut 1.7 on the C-shaded aluminium master mould, the total
displacement in y-direction is 0.2mm, which is 0.06%
R X- (b) C-shape made of HexTOOL
R Y(a) C-shape made of HexTOOL
direction
direction
Figure 42: Plot of the measured depart from CAD part, C-shape, HexTool
66
8 MEASUREMENTS 8.3 Measurement of parts made in C-shape mould
around 0, and blue -0.4mm and lower. This is most meant as an illustration
of where the poins of biggest deposits are.
(a) C-shape made of Beta prepreg X- (b) C-shape made of Beta prepreg Ydirection
direction
Figure 43: Plot of the measured depart from CAD part, C-shape, Beta
In table 16 is the displacement in the y-direction of the C-shape shown.
Number 2.7-2.11 are not of interest in this direction. From numbers 2.3, 2.4,
2.5, 2.14, 2.15 and 2,16 is the dierence less in the middle of the part than
in the edges. This means that the curve in the middle is helping the part
to be held in the right shape. This can also be seen from the graphs in the
opposite direction, gure 47, where it is as close as zero displacement.
8.3 Measurement of parts made in C-shape mould
Two parts were made in each of the C-shaped moulds, as explained in
R mould and the other in
section 6.6. One part was made in the HexTOOL
the Beta prepreg mould. This was to see if they turned out with the same
deformation or not.
The shape has a slightly dierent height at one side
◦
compared to the other. They were measured with a 180 angle dierence.
This was solved by shifting places for the z-direction on the Beta part, and
this gave correct results.
The part made in the Beta mould is measured
part around the z-axis.
180◦
dierent to the CAD
Which means that the displacements in table 17
is showing a higher value than what is really the case. The maximum displacement is bigger, and the minimum is most likely smaller than the actual.
Lack of time is the reason for why this have not been done once more. The
capacity in the measuring machine is pushed to the limit.
67
8.3 Measurement of parts made in C-shape mould 8 MEASUREMENTS
Table 16: Displacements in y-direction for C-shaped moulds, given in mm
Displacement, y-direction, [mm]
R
HexTOOL
Beta
Nr
Max
Min
Average
Max
Min
Average
2.1
0.717
0.131
0.443
0.608
0.203
0.408
2.2
1.215
0.589
0.929
1.083
0.554
0.853
2.3
1.424
0.654
1.037
1.245
0.406
0.838
2.4
1.362
0.007
0.640
1.153
0.008
0.536
2.5
0.933
0.011
0.426
0.864
0.003
0.363
2.6
0.456
0.005
0.157
0.360
0.002
0.113
2.12
0.398
0.000
0.106
0.337
0.002
0.066
2.13
0.658
0.013
0.441
0.554
0.001
0.331
2.14
1.821
0.013
0.834
1.548
0.000
0.645
2.15
2.259
0.045
1.167
1.957
0.006
0.927
2.16
2.571
1.220
1.905
2.221
0.960
1.551
2.17
2.637
2.067
2.333
2.196
1.575
1.794
2.18
2.831
2.350
2.558
2.274
1.677
1.889
The middle rerion in yz direction, C−shape, moulds
80
60
40
Z [mm]
20
0
−20
−40
−60
CAD
HexTOOL
Beta
−80
−100
−350
−300
−250
−200
−150
−100
−50
0
Y [mm]
Figure 44:
Cut 1.2 on the C-shaped moulds, maximum displacement for
R
HexTOOL
was 2.311mm, 0.69% and for Beta 1.7064mm, 0.50% this is
where the opening is biggest, y-direction. At point 4 from the bottom it was
0.787mm and 0.683mm
68
8 MEASUREMENTS 8.3 Measurement of parts made in C-shape mould
The middle rerion in yz direction, C−shape, moulds
60
40
20
Z [mm]
0
−20
−40
−60
CAD
HexTOOL
Beta
−80
−100
−350
−300
−250
−200
−150
−100
−50
0
Y [mm]
Figure 45:
Cut 1.7 on the C-shaped moulds, maximum displacement for
R
HexTOOL
was 1.617mm, 0.46% and for Beta 1.124mm, 0.33% this is where
the opening is biggest, y-direction. At point 3 from the bottom it was 0.5mm
for both moulds
The middle rerion in yz direction, C−shape, moulds
100
Z [mm]
50
0
−50
−100
−400
CAD
HexTOOL
Beta
−350
−300
−250
−200
−150
−100
−50
0
Y [mm]
Figure 46: Cut 1.10 on the C-shaped moulds, maximum displacement for
R was 1.913mm, 0.53% and for Beta 1.206mm, 0.34% this is where
HexTOOL
the opening is biggest, y-direction.
At point 5/4 from the bottom it was
0.296mm and 0.197mm
69
8.3 Measurement of parts made in C-shape mould 8 MEASUREMENTS
C−shape, xz−direction
90
85
80
Z [mm]
75
70
65
60
55
50
−200
CAD
HexTOOL
Beta
−150
−100
−50
0
50
100
X [mm]
Figure 47:
Cut 2.8 on the C-shaped moulds, maximum displacement for
R was 0.428mm and for Beta 0.254mm, z-direction
HexTOOL
(a) Part made in C-shape mould of (b) Part made in C-shape mould of Beta
R
HexTOOL
prepreg
Figure 48: Plot of the measured parts made in composite C-shape mould
70
8 MEASUREMENTS 8.3 Measurement of parts made in C-shape mould
Table 17: Displacements in y-direction for C-shaped parts, given in mm
Displacement, y-direction
R
made in Beta
made in HexTOOL
Nr
Max
Min
Average
Max
Min
Average
2.1
-0.711
0.006
-0.0503
-9.740
0.057
3.451
2.2
1.878
0.200
1.095
-9.292
0.008
2.167
2.3
2.019
0.000
1.010
-7.442
-0.001
-1.814
2.4
2.312
0.001
0.731
-2.480
-0.008
-0.552
2.10
1.164
-0.002
0.494
-2.949
0.006
-0.901
2.11
1.928
-0.001
1.072
-3.456
-0.002
-0.882
2.12
2.590
-0.505
1.446
-4.738
-0.113
-1.172
2.13
3.078
1.893
2.588
5,805
0.001
-2,617
Cut 1.13/ 1.2 in yz direction, C−shape, parts
20
0
Z [mm]
−20
−40
−60
CAD Part
In HexTOOL
In Beta
−80
−100
−50
0
50
100
150
200
250
300
350
Y [mm]
Figure 49: Cut 1.2 on the C-shaped parts, maximum displacement for part
R was 1.504mm, 0.48% and in Beta 5.741mm, 1.182%
made in HexTOOL
71
8.3 Measurement of parts made in C-shape mould 8 MEASUREMENTS
The middle rerion in yz direction, C−shape, moulds
−10
−20
CAD Part
In HexTOOL
In Beta
−30
Z [mm]
−40
−50
−60
−70
−80
−90
−50
0
50
100
150
200
250
300
350
Y [mm]
Figure 50: Cut 1.7 on the C-shaped parts, maximum displacement for part
R was 0.746mm, 0.23% and in Beta 0.634mm, 0.2%
made in HexTOOL
The middle rerion in yz direction, C−shape, moulds
20
0
Z [mm]
−20
−40
−60
CAD Part
In HexTOOL
In Beta
−80
−100
−50
0
50
100
150
200
250
300
350
Y [mm]
Figure 51: Cut 1.10 on the C-shaped parts, maximum displacement for part
R was 1.643mm, 0.57% and in Beta 3.403mm, 1.18%
made in HexTOOL
72
8 MEASUREMENTS 8.3 Measurement of parts made in C-shape mould
8.3.1
All three C-shapes together
C−shape
10
5
0
Z [mm]
−5
−10
−15
−20
−25
−30
−200
Alu
HexTool
Part
−150
−100
−50
0
50
100
X [mm]
Figure 52: Cut 2.7 of the aluminium mould, HexTOOL mould, and part
In gure 52 is the graphs of the aluminim master mould, M61 mould and
and the part made in the M61 mould showed. Here it looks like they are all
out of tolerances. By looking at gure 53, where the same graphs are put
together with each of the dierent CAD models, can it be seen that there are
only small displacements. The dierence in gure 52 is due to measurements
on dierent places of the mould, and is the reason for why the results are not
presented this way.
73
8.3 Measurement of parts made in C-shape mould 8 MEASUREMENTS
C−shape
10
5
0
Z [mm]
−5
−10
−15
−20
−25
−30
−200
CAD
Alu
CAD Mold
HexTool
CAD Part
Part
−150
−100
−50
0
50
100
X [mm]
Figure 53: Cut 2.7 of the aluminium mould, HexTOOL mould, and part with
their CAD part
74
9 RESULTS
9
Results
It was choosen to make the two moulds with composite materials. Ad-
vanced composite materials are thermally stable which makes it easier to
achieve dimensional control.
The maximum displacements in x-direction of the Ω moulds are 4.670mm
R and 1.206mm for the Beta, see table 15.
for HexTOOL
The moulds made on a ytong plug received a rough surface, which must
be machined before it can be used as a mould.
Since it anyways needs
machining, the spring is not too big problem as long as the cross section is
thick enough. The moulds are approxmetly 10mm in thickness. The strength
will still be sucient if half of the measured displacement is removed on each
side. It was not available machining time to see if the dimensional accuracy
was maintained if this was done.
9.1 FE analysis and real part
The
Ω
shape has been evaluated both using FE analysis and as a real
mould. They both shows the same tendency of a smaller arc after cure. The
FE analysis shows a more pessimistic trend than the real part. This means
3.5% for the FE-analysis and 1.17% for the measured part.
For both the FE-analysis and the measurements shows a tendency of when
the arc is decreasing, it naturally receive a smaller radius. Which pushes the
arc of the deformed shape to cross the original shape.
9.2 Measurements, C-shape
The C-shaped master mould were made using a ne machined aluminium
plug. This gave the moulds a ner surface which only needed sanding and
pore sealing to achieve a sucient mould surface. The thickness of the moulds
were not made for machining.
It was choosen to not have a machinable
thickness because the master mould would give it a good enough surface,
which it did.
The C-shape has been made with the whole mould process. That means
master mould, mouls and part.
R had dierence from the CAD model of max
The mould of HexTOOL
imum 3.55mm, average 3.0mm and minimum of 2.481mm.
The mould in
Beta had dierence in y-direction of maximum 2.882mm, average 2.29mm
and minimum 1.88mm.
R mould has a dierence from
The nal part produced in the HexTOOL
the CAD le of 3.789mm.
The average is 2.638mm and the smallest were
75
9.3 HexTOOLR and Beta prepreg
9 RESULTS
1.887mm. The part made in Beta had a dierence of maximum 15.54mm,
average 6.07mm, and minimum 0.06mm.
9.3 HexTOOL R and Beta prepreg
R and Beta prepreg will be compared with consideration of
HexTOOL
KONGSERG's needs and use. The number of made parts are not sucient
to give a real statement of what is best, but it will give some ideas. It will
be compared both what the numbers actually say and experience in working
with the dierent materials.
In table 8 to 11 the values for the two tooling materials, cured and uncured, and mechanical property are listed. As seen, the temperature values
are similar. The plies are dierent both in thickness and bre orientation.
R material is both an
The random orientation of the bres in the HexTOOL
advantage and disadvantage. It makes it easier to form into places since it
allows a certain deformation of the plies. The randomness also leads to random thickness before and after cure. This gives a more varying deformation.
The woven plies of Beta prepreg are easier to cut and predict thickness, but
uses much more time with layup due to smaller thickness of plies than for
R
the HexTOOL .
Beta prepreg have a natural tack that makes it easier for the layup because
the plies stick to each other. This has showed itself as nearly too good, but
it can be decreased with cooling of the material. In the same way that the
M61 material gets soft and easy to shape with heat.
The main disadvantage of the Beta prepreg is how some people have
reacted on its volatiles.
When comparing the two moulds made as C-shape in gure 42 and 43,
it can be seen that the overall dierence from the CAD le is bigger for the
R than the Beta prepreg mould. This is also given by the numbers
HexTOOL
in table 16. The dierence is not big, the maximum between them is about
0.5mm. They have the same tendency of where this dierence is biggest, at
the biggest gap in the y-direction.
Both of the materials advertise themselves as being stable after and during
machining.
76
10 DISCUSSION
10
Discussion
One method for using requirements is to rate them with values and always
be sure that the highest rated is followed. This might give a dierent nal
result than to look at all of them, not equally, but more evenly. As mentioned
earlier, mould selection is often in the end based on what is known and tried
out.
10.1 The selection
There has been used two types of master moulds.
One of them was
Ytong, this gave a rough surface on the produced mould.
This leads to
supplementary work on the mould in form of machining in addition to normal
pore sealing and release agent.
Was it best to use; ytong or aluminium master? The cost of ytong is much
lower than for aluminium, both in raw material and machining. The ytong
master require adaptive work before it can be used.
It is often assembled
from blocks. It also need layers on the outside so it is possible to release the
mould. The cured mould need to be machined. For each part this must be
compared.
It was chosen to make two moulds in two quite similar materials. Both of
them are light, and easy to maneuver. One disadvantage of having a small
mould in a light material, is that it might move too easily. A solution for
this is to make a support structure that can be fastened to a table. It should
be possible to move for better layup.
It may have given a wider idea of dierent materials for moulds if only
one shape was tested, but with more than two types of materials.
NDT of the mould to see if the composite have received any cracks from
the aluminium plug.
10.2 FE analysis
In table 14, displacements for the cured mould are listed together with
those of a mould cured with a part inside. The number for the dierent parts
showers similar results of 4
±0.5mm
displacement in x-direction.
In the FE analysis a ner mesh could have been used. This might have
given a more accurate result. The mash on the part was equally distributed
without to sharp angles in the corners of the elements.
It was used material data for one type of carbon bre prepreg for the
analysis. It was not applied the resin cure shrinkage in the analysis. This
could have been done for each of the two produced parts, this might have
77
10.3 The measurements
10 DISCUSSION
given results closer to each of them. It was not the intention for this thesis to
nd the material properties for the used materials in the produced parts. If
this had been carried out and used in the analysis it would have given more
accurate results for each of the material type.
It was tested out to apply pressure that should have illustrated the autoclave pressure, but a good solution for this was not found.
10.3 The measurements
There are uncertainties in the measurement results. One of them is that
the
Ω shape had a rough surface.
The ytong material gives a roughness on the
surface. It was thought of straightening out the biggest peak, but that might
have caused the shape to change. The ytong is brittle and crumble easily,
which means that it might have lost some material at some places. It has
also been covered with a thin sheet of release lm, which built 3/10mm. It
was not possible to do accurate measurements of the ytong part, so results of
how the nal shape looked like do not exist. Instead the parts were measured
against the 3D drawing.
The two parts were made out of two dierent ytong master moulds, which
also might have contained small individual dierences.
mould broke after cure.
The rst master
This may happen with ytong moulds, so if it is
desired to make more than one part on the mould, it should be considered
another material.
The measurements of the C-shape could have been done with more points
to achieve a more accurate result. It was not possible to measure the mould
up against the master mould, or part against the measured mould. If it was
found a solution for connecting the measured aluminium master mould to
the made mould, and then the made mould to the made part, a more clear
result would have been presented.
Since the points are taken on slightly
dierent places, it can not be directly compared, but it indicates a trend.
The measured parts was in this report measured with the CAD part as
point of departure, this give a result if the nal part are alike the designed
shaped. But if the mould has changed during production, this is not taken
into consideration.
10.4 Future work
Suggestions for future work:
◦
Find a way to link the measured mould to the new measurements of
the part produced in the mould.
78
10 DISCUSSION
◦
10.4 Future work
One way to get a strong but light material with low CTE could be to
attach cores in the laminate.
This can be an advantage for lower spring,
and then can be possible to use in moulds. One of the challenges with core
material is to expose them to many temperature changes.
◦
Make for example the same C-shape mould in materials at lower cost.
It could have been for example glass bres with high cure resin or epoxy
paste method.
It would hopefully give a answer if the materials at higher
cost performs better or not.
R are now also made with long bres, as woven plies. This
◦ HexTOOL
might be an interesting material to investigate more. This will give a more
even thickness, but the advantages of the easy forming of the ply due to the
short random bres are gone.
◦
Machine the two
Ω
moulds after cure to see if they change during or
after machining. In composite parts that is always a possibility.
79
10.4 Future work
10 DISCUSSION
80
11 CONCLUSION
11
Conclusion
This report has considered dierent techniques for mould making. This
is a phase under continuous development and improvement. There are many
materials that can be used for each production method.
factors that play a role in the selection.
There are many
Depending on size, shape, cure
temperature a method is selected. What kind of material to use and which
method varies for dierent parts.
A set of requirements for composite moulds have been establiched. The
most important requirement are dierent for dierent parts.
Things that
divides the most important aspects are among others shape, size, accuracy
of part, and material for part.
For big moulds one of the biggest challenges is to be able to maneuver the
mould. The weight of the mould itself might be a challenge to the structure
holding it.
To reduce the thermal mass is important.
For small parts the
dimensional accuracy are often a bigger challenge.
One of the main challenges in mould production is to know how much
the material changes during cure. This has been investigated in form of FEanalysis and measurements of real parts.
The real part showed a smaller
spring-in than the FE-analysis, 1.17% versus 3.5%.
Two mould materials were choosen to investigate.
From the produced
moulds, both materials gives a good nal mould for the given part. From the
R 0.7 ±0.5mm larger spring than Beta.
measurements shoves the HexTOOL
Parts made with double bended mould, have here a tendency of less
spring-in in the area of two curves.
81
11 CONCLUSION
82
12
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85
Ana-
http://ivt-
86
A APPENDIX, THERMOLOGGER
A
Appendix, thermologger
The thermo log of the curing of the C-shaped Beta prepreg in autoclave.
The temperature and pressure was sucient during the whole cure.
____e.
_
______
__
______
______
______
load no. 101040 profile-no. Beta G6 16.11.2011 10:47:16 16.11.2011 21:18:16
-10
220
210
200
[j 184,6
190
I
H
I
9
1806
I
180
-8
.7
.
ft
/
130
/1
120
1128,71
-6
/
I
0
50
100
150
re,04...4
I un
01011
200
250
300
‘
ill lf
5
I
I
I
I
350
400
450
500
550
600
runtimer [mini
pressure
set
JSM Test. Med Beta Pre-Preg
air
part
#1
Figure 54: Thermo log of Beta cure, C-shape
87
650
700
A APPENDIX, THERMOLOGGER
88
B APPENDIX, FE ANALYSIS
B
Appendix, FE analysis
Figure 55: Boundary conditions on the
89
Ω
mould and master mould
B APPENDIX, FE ANALYSIS
Table 18: Displacements of master moulds of aluminium and ytong, with
their respective moulds
Point
in arc
Displacement, [mm]
Aluminium master
Mould, on alu
Ytong master
Mould, on ytong
Nr
X
Y
X
Y
X
Y
X
Y
A.1
-2,885
-1,066
-3,146
0,001
-0,456
-0,463
-3,142
0,001
A.2
-2,620
-1,348
-3,136
0,007
-0,571
-0,586
-3,098
0,097
A.3
-2,274
-1,520
-0,029
0,061
-0,722
-0,661
-2,792
0,148
A.4
-1,967
-1,564
-2,619
0,186
-0,855
-0,680
-2,386
0,260
A.5
-1,735
-1,539
-2,248
0,320
-0,956
-0,669
-2,016
0,455
A.6
-1,514
-1,466
-1,922
0,526
-1,082
-0,622
-1,745
0,700
A.7
-1,253
-1,299
-1,774
0,666
-1,165
-0,565
-1,642
0,849
A.8
-0,943
-0,858
-1,658
0,822
-1,234
-0,491
-1,590
0,966
A.9
-0,845
-0,494
-1,574
0,997
-1,300
-0,373
-1,574
0,997
A.10
-0,547
-0,469
-1,544
0,916
-1,342
-0,215
-1,563
0,965
A.11
-0,312
-0,469
-1,345
0,629
-1,472
-0,203
-1,345
0,629
A.12
-0,078
-0,469
-0,834
0,285
-1,574
-0,204
-0,763
0,256
Piont
Displacement, wings, [mm]
Nr
X
Y
X
Y
X
Y
X
Y
W.1
W.2
-3,058
-0,555
-3,137
0,003
-0,381
-0,242
-3,131
0,031
0.000
-0,469
-3,132
0,031
-1,710
-0,204
-2,977
0,124
W.3
-3,049
-0,469
-2,977
0,124
-0,340
-0,204
-0,019
0,026
W.4
-3,015
-0,709
-0,124
0,120
-0,391
-0,308
0.000
0.000
W.5
-2,990
-0,858
-0,014
0.000
-0,410
-0,373
-3,147
0,001
W.6
-3,699
-0,469
-0,263
0,130
-0,443
0,161
-0,443
0,161
W.7
-3,542
-0,469
-0,011
-0,001
-0,012
-0,001
-0,012
-0,001
W.8
-3,386
-0,469
-0,008
-0,001
-0,009
-0,001
-0,009
-0,001
W.9
-3,230
-0,469
-0,004
-0,000
-0,006
-0,000
-0,005
-0,000
W.10
-2,680
-1,202
-0,002
-0,000
-0,003
-0,000
-0,003
-0,000
90
C APPENDIX, MEASUREMENTS
C
Appendix, Measurements
(a) Measurements points 1
(b) Measurements points 2
Figure 56: Plot with the measurement points in the arc of the
91
Ω
C APPENDIX, MEASUREMENTS
Figure 57: Measurements points 3
(a) Measurements points 4
(b) Measurements points 5
Figure 58: Plot with the measurement points on the wings of the
92
Ω
C APPENDIX, MEASUREMENTS
(a) Plot of depart of the wings on HexTOOL
(b) Plot of depart of the wings on Beta
Figure 59: Analysis of the
Ω,
wings
Figure 60: Aluminium master mould with measuring points
93
C APPENDIX, MEASUREMENTS
Figure 61: Carbon mould with measuring points
Figure 62: Carbon part with measuring points
94
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