Fiber Patch Placement

Fiber Patch Placement
Interaction of lay-up pattern and mechanical performance of the
composite
Bernhard Horn
„A Comprehensive Approach to Carbon Composites Technology“
Symposium on the occasion of the 5th anniversary of the Institute for Carbon Composites
Research Campus Garching, September 11th - 12th 2014
Institute for Carbon Composites
donated by
Agenda
1
Motivation
2
Introduction to FPP laminate design
3
Influence of the patch pattern on tensile strength
4
Approach to predict the tensile strength of a FPP laminate
5
Summery and Outlook
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
2
Agenda
1
Motivation
2
Introduction to FPP laminate design
3
Influence of the patch pattern on tensile strength
4
Approach to predict the tensile strength of a FPP laminate
5
Summery and Outlook
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
3
Motivation
Idea of lightweight design
Maximum lightweight design requires load path optimized design
Fig. 1: Load paths in a component [1]
Fig. 2: Snowboard reinforcement
Variable angle tow composites
[1] Mattheck, C. Design in der Natur: Der Baum als Lehrmeister, 3rd edn. Freiburg im Breisgau; 1997
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Motivation
Limitations of typical automated manufacturing processes using UD fibers
Uneven thickness distribution
Buckling on inner radius
Tow gap
Fig. 1: TFP: Uneven thickness
distribution and fiber misalignment for
steered roving cf. [1]
Fig. 2: AFP: Buckling of steered tapes
cf. [2]
Fig. 3: Curved endless fibers
In-plane bending deformation reduces the design flexibility and weakens the
mechanical properties
[1] Kim BC. Limitations of Fibre Placement Techniques for Variable Angle Tow Composites and their process-induced Defects; 2011
[2] Blom AW. Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells. Dissertation. Delft; 2010
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Motivation
Different approach to reduce the process induced defects
Use of long fiber patches instead of endless fibers
Fig. 1: Curved endless fibers
Fig. 2: Cut fiber patches
Fig. 3: Small radi possible due to
cut fiber patches
High flexibility for load path optimized layup design
Butt splices reduce the maximum strength of the composite
Optimization of butt splices distribution necessary
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Motivation
Video demonstration
6 steps of the FPP-process:
1.
2.
3.
4.
5.
6.
Feeding dry, bindered tape
Cutting tape into patches
Quality inspection of patches
Picking up patches
Checking patch position at gripper
Positioning patch
(1)
Technical Specifications:
Patching rate:
Performance:
(2)
(3) (4&5) (6)
up to 1 Patch/s
up to 500 g/h
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Agenda
1
Motivation
2
Introduction to FPP laminate design
3
Influence of the patch pattern on tensile strength
4
Approach to predict the tensile strength of a FPP laminate
5
Summery and Outlook
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
8
Introduction to FPP laminate design
Structure of a FPP laminate
Each laminate consists of a specific amount of patch pattern
Patch pattern
FPP-Laminate
Butt splice
Fiber patch
Sublayer
Patch pattern
Fiber orientation
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Introduction to FPP laminate design
Structure of a patch pattern
Assumption
Crack propagation
F [N]
F [N]
Fiber orientation
patch pattern
Design characteristics
 Each sublayer can be shifted in-plane
 Position of butt splice in thickness direction can vary
𝜎
𝜎𝑒𝑛𝑑𝑙𝑒𝑠𝑠 𝑓𝑖𝑏𝑒𝑟
4
3
2
1
𝜎𝑟𝑒𝑠𝑖𝑛
Overall aim: Crack length should be maximized
𝜀
c.f. Oliver Meyer. Kurzfaser-Preform-Technologie zur kraftflussgerechten Herstellung von Faserverbundbauteilen. Dissertation. Stuttgart; 2008
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Agenda
1
Motivation
2
Introduction to FPP laminate design
3
Influence of the patch pattern on tensile strength
4
Approach to predict the tensile strength of a FPP laminate
5
Summery and Outlook
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Influence of the patch pattern on tensile strength
Influence of the critical fiber overlap length
The layup problem can be visualized as a double lap joint
Redirection of force flow from one layer to another
Postulation [1]:
Critical overlap length depends on fiber architecture
z
y
x
F
loverlap
Patch
σ
F
Expected laminate failure [1]
𝑙𝑜𝑣𝑒𝑟𝑙𝑎𝑝 < 𝑙𝑐𝑟𝑖𝑡
𝑙𝑜𝑣𝑒𝑟𝑙𝑎𝑝 > 𝑙𝑐𝑟𝑖𝑡
τ
𝐹𝑖𝑏𝑒𝑟 𝑝𝑢𝑙𝑙 − 𝑜𝑢𝑡
𝐹𝑖𝑏𝑒𝑟𝑓𝑟𝑎𝑐𝑡𝑢𝑟𝑒
Fig. 1: Schematic stress and shear distribution in a double
lap joint
For maximum strength of the laminate: overlap length > critical fiber length
[1] Och G. Berechnung der Elastizitätskonstanten und der Zugfestigkeit: MBB Technische Niederschrift; 1970.
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Influence of the patch pattern on tensile strength
Strength model for FPP-laminates by O. Meyer [1] (1/2)
Restrictions
 𝑙𝑜𝑣𝑒𝑟𝑙𝑎𝑝 > 𝑙𝑐𝑟𝑖𝑡
 𝑙𝑐𝑟𝑎𝑐𝑘 = 𝑚𝑎𝑥
Prediction:
 Every section with a butt splice has the same probability to fail
patch
butt splice
patch pattern
section with butt splice
sublayer
There are always n-1 sublayers which can transfer the load in a pattern
σ𝑡,𝐶𝑜𝑚𝑝𝑜𝑠𝑖𝑡𝑒
𝑛−1
=
σ𝑡,𝑓𝑖𝑏𝑒𝑟
𝑛
for n = number of sublayer
and σt,fiber ≫ σt,resin
[1] Oliver Meyer. Kurzfaser-Preform-Technologie zur kraftflussgerechten Herstellung von Faserverbundbauteilen. Dissertation. Stuttgart; 2008
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Influence of the patch pattern on tensile strength
Strength model for FPP-lamintes by O. Meyer [1] (2/2)
σ𝑡,𝐶𝑜𝑚𝑝𝑜𝑠𝑖𝑡𝑒 =
𝑛−1
σ𝑡,𝑓𝑖𝑏𝑒𝑟
𝑛
Maximum Strength
continuous fiber
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
2
3
5
6
10
Amount of sublayer per patch pattern
Experimental Results
Model by Mayer
Fig. 1: Influence of sublayer on maximum strength [2]
Fig. 2: Failure for different patch pattern [1]
Model by Mayer overpredicts the maximum tensile strength
[1] Oliver Meyer. Kurzfaser-Preform-Technologie zur kraftflussgerechten Herstellung von Faserverbundbauteilen. Dissertation. Stuttgart; 2008
[2] unpublished LCC bachelor thesis: 2012 Philipp Stahl, „Untersuchungen der mechanischen kennwerte von unidirektionalm Faserverbundmaterial – erstellt im FPP-Prozess“
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Agenda
1
Motivation
2
Introduction to FPP laminate design
3
Influence of the patch pattern on tensile strength
4
Approach to predict the tensile strength of a FPP laminate
5
Summery and Outlook
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Approach to predict the tensile strength of a FPP laminate
New approach to predict maximum tensile strength for straight patch path
Assumption by Mayer
Every layer has the same contribution to the strength of the composite
New approach considers two main influencing factor
Overlap length for each sublayer
l4,5
Influence of butt splice with each other
z
l3,4
y
l1,2
Quality-Value 𝑄𝐿𝑧
x
l2,3
Weighting -Value 𝐺𝑧
[unpublished LCC diploma thesis: 2014, Yannik Blößl, „Untersuchungen zur Qualitätsbewertung der Patchanordnung von unidirektionalem FPP-Material“]
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Approach to predict the tensile strength of a FPP laminate
Transformation of approach into a formula
Overlap length 𝑙𝑧
Empirical finding: Asymptotic
behavior for higher overlap
length
Weighting -Value 𝐺𝑧
Material properties
Scaling factor
Quality-Value 𝑄𝐿𝑧
Consideration of butt splices in z-direction
Weighting function
Quality function
Consideration of overlap length
Scaling-Factor 𝑆𝑀𝑎𝑡𝑒𝑟𝑖𝑎𝑙
Distance between butt splices
Assumption: Decreasing
influence for higher
distance between butt
splices
Estimated maximum tensile strength:
Material
Empirical value
zmax
Xtensile = SMaterial ∗
(Gz ∗ QLZ )
z=1
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Approach to predict the tensile strength of a FPP laminate
Comparison of both models with experimental results
Influence of the amount of sublayer on maximum strength
100%
90%
Maximum Strength
80%
70%
60%
50%
40%
30%
20%
10%
0%
2
3
Experimental Results
5
Amount of sublayer per patch pattern
Model by Mayer
6
10
New Approach
New prediction of maximum strength leads to better results
Further investigation for different materials necessary
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Agenda
1
Motivation
2
Introduction to FPP laminate design
3
Influence of the patch pattern on tensile strength
4
Approach to predict the tensile strength of a FPP laminate
5
Summery and Outlook
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Summary & Outlook
Summary
 Patch pattern influences the tensile strength of the composite
 New approach includes overlap length and butt splice distribution in z-direction for
each sublayer
 New model and experimental results show a high similarity
Weighting -Value 𝐺𝑧
Scaling-Factor 𝑆𝑀𝑎𝑡𝑒𝑟𝑖𝑎𝑙
Influence of the amount of sublayer on
maximum strength
Maximum Strength
100%
Scaling factor
Quality-Value 𝑄𝐿𝑧
Consideration of butt splices in z-directionMaterial properties
Weighting function
Quality function
Consideration of overlap
length
50%
0%
2
Overlap length 𝑙𝑧
Distance between of butt splices
Material
3
5
6
10
Amount of sublayer per patch pattern
Experimental Results
Model by Mayer
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Summery and Outlook
Outlook
 Understanding of the failure mechanism and their contribution to maximum tensile strength
 Validation for different material combinations
 Expansion of the model for curvilinear patch path
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Summery and Outlook
Project Patchwork
Key facts
 Government-funded project to transfer the FPP technology into commercial applications (EXIST Forschungstransfer)
 Focus on individual components and tailored reinforcement layers
 Automated production of geometrically-complex and high-performance components
 Tailored reinforcement layers in combination with other preforming technologies
Contact / Info
Engineering objectives
Production
CAE
Preforming
1
CFR component
Injection
2
•1
Method for efficient simulation and optimization of FPP structures
•2
Automated handling of FPP-preform and automated resin injection process
Dipl.-Ing. Felix Michl
[email protected]
Tel: +49 89 289 15788
The team is currently
looking for prototypes to demonstrate
the unique benefits of
FPP in commercial
applications!
Objective: develop a continuous process chain to leverage the FPP technology in automated serial productions
12.09.2014 | Horn | Fiber Patch Placement – Interaction of lay-up pattern and mechanical performance of the composite
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Contact
Bernhard Horn
Room
Tel
Fax
Email
1427
+49 89 / 289 - 15076
+49 89 / 289 - 15097
[email protected]
Address
Technische Universität München
Institute for Carbon Composites
Boltzmannstraße 15
85748 Garching
www.lcc.mw.tum.de
Institute for Carbon Composites
donated by
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