DIGIMAT FOR CONTINUOUS FIBER REINFORCED COMPOSITES
Roger Assaker, Pierre-Paul Jeunechamps, Jan Seyfarth, Laurent Adam
May 2011
DIGIMAT FOR CONTINUOUS FIBER
REINFORCED COMPOSITES
The Challenge
Continuous fiber reinforced composites in automotive industry
Synergy between different industries
Simulation technology for Continuous fiber reinforced composites
e-Xstream engineering
DIGIMAT Software
Application example: Wind Turbine Rotor Blade
Simulation Approach
Model
Materials
Results
Summary
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Courtesy of
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Continuous fiber reinforced composites in automotive industry
Glass fiber reinforcement (GFRP)
Carbon fiber reinforcement (CFRP)
• PROS
– Strong, stiff and light
• CONS
– High material costs
– Long manufacturing cycle times
Some applications already exist (sports cars, formula 1)
Not yet used in mass production vehicles
Seen as the technology for the future...
The Challenge
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Continuous fiber reinforced composites in automotive
High-end sports cars
The Challenge Sources:
www.cardesignonline.com
www.rumors.automobilemag.com
www.wot.motortrend.com
Mercedes-Mclaren SLR Lamborghini Aventador
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Continuous fiber reinforced composites in automotive
Future technology - CFRP passenger compartment
The Challenge
BMW i3 @ JEC Composites 2011
BMW i3 / BMW i8 Hybrid concept car
Sources:
www.bmw-i.de
www.wardsauto.com
www.treehugger.com
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Continuous fiber reinforced composites in automotive
First approaches towards mass production
• Production facility in Landshut, Germany
– Serves as both a laboratory and pilot plant
– Houses what BMW calls "the world's first highly automated production process for CFP body components."
• 1.400 roofs produced for the M3 CSL coupe in 2003
• Increasing demand can bring price down to some acceptable level
– BMW and VW fight over SGL Carbon
– Access to carbon fiber ressources is critical
The Challenge Source:
www.findarticles.com:
„Can Carbon fibers compete?“
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Investigation of design concepts
Synergy between different industries
• Run on Carbon fiber material is ongoing
– Strongly growing market in automotive
– Strongly growing market in renewable energy
The Challenge www.zoltek.com
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Investigation of design concepts
Synergy between different industries
Automotive
• Mass production needed
• Cycle times & costs critical
• Strong focus on carbon fibers
Aerospace
• Automated production
• Cycle times not critical
• Glass & Carbon fibers
Renewable energy
• Automated & manual production
• Cycle times not critical
• Mainly glass fibers
The Challenge
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Simulation is key to the investigation of future designs
For all of these industries there is a lack of sufficient material models to describe composites
• This is especially true for the demands from the automotive industry
• Material modeling must cover
– Different matrix properties
» Nonlinear effects
» Temperature dependency
» Strain rate dependency
– Different fiber properties
» Isotropic as well as transversely isotropic
» Anisotropy
– Failure
» Complex failure
» Fatigue failure
DIGIMAT Technology
e-Xstream engineering
Founded in 2003
The Business:
Simulation Software & Services
100% focused on material modeling
The team
Strong & highly motivated
High level of education
The product
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Louvain-la-Neuve
Bascharage
Munich
Belgium
Luxembourg
Germany
U.S.
DIGIMAT Technology
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DIGIMAT
DIGIMAT Technology
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DIGIMAT Technology
Material modeling
Setup the material model
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DIGIMAT Technology
Material modeling
Reverse Engineer material parameters
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Interface to Drapage simulation
DIGIMAT Technology
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Coupled solution
DIGIMAT Technology
Drapage(4.2.1/4.3.1)
FEA
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Multi-scale Simulation
DIGIMAT Technology
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Wind turbine rotor blade
Virtual design of a wind turbine rotor blade
Check the performance of (expensive) carbon fibers in the virtual environment
• Compare to the existing design based on glass fiber material
Strategy
• Go from draping to FEA in a simple workflow
• Use one unique approach for the modeling of different composites
– Epoxy / Glass fiber
– Epoxy / Carbon fiber
• Define & use failure indicators on the microscopic level
– Max. Principle Stress in the fiber phase
– Max. Principle Strain in the matrix phase
Application Example
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Model
Boundary conditions:
• The blade is fixed in displacement and rotation on the end where the blade is in real connected to the engine’s rotor
• A pressure is uniformly applied on one side of the blade, in the opposite direction to acceleration’s direction
Loading: +Z linear acceleration applied on the blade
Application Example
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Application Example
Model
Shell sections
• 8 layers
• UD composite
Composite properties exchanged by DIGIMAT
material
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Application Example
Model
Shell sections
• 18 layers
• 3 different materials
– Paint
– UD composite
– Foam
Composite properties exchanged by DIGIMAT
material
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Application Example
Epoxy matrix (Isotropic)
Density 1100.0 kg/m^3
E 3300 MPa
PR 0.3
VF 0.4
Max Principal Strain (tens.) 5 %
Max Principal Strain (comp.) 10 %
Glass fibers (Isotropic)
Density 2540.0 kg/m^3
E 72000 MPa
PR 0.22
VF 0.6
AR 10000
Max Principal Stress (tens.) 1500 MPa
Max Principal Stress (comp.) 700 MPa
Materials
UD composite / DIGIMAT model 1
• Glass fiber reinforcement
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Application Example
Epoxy matrix (Isotropic)
Density 1100.0 kg/m^3
E 3300 MPa
PR 0.3
VF 0.4
Max Principal Strain (tens.) 5 %
Max Principal Strain (comp.) 10 %
Carbon T300 fibers (Isotropic)
Density 1800.0 kg/m^3
E 233000 MPa
PR 0.2
VF 0.6
AR 10000
Max Principal Stress (tens.) 2000 MPa
Max Principal Stress (comp.) 1500 MPa
Materials
UD composite / DIGIMAT model 2
• Carbon fiber reinforcement
Epoxy matrix (Isotropic)
Density 1100.0 kg/m^3
E 3300 MPa
PR 0.3
VF 0.4
Max Principal Strain (tens.) 5 %
Max Principal Strain (comp.) 10 %
Carbon T300 fibers (Transversely isotropic)
Density 1800.0 kg/m^3
Axial E 233000 MPa
In-plane E 23100 MPa
In-plane PR 0.2
Transverse PR 0.2
Transverse shear 8963 MPa
VF 0.6
AR 10000
Max Principal Stress (tens.) 2000 MPa
Max Principal Stress (comp.) 1500 MPa
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Application Example
Materials
UD composite / DIGIMAT model 3
• Carbon fiber reinforcement
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Failure analysis in Digimat-MF
Principle behavior of failure in a RVE
• No significant difference between isotropic and transversely isotropic carbon fibers models
• Matrix begins to break for lower values of j for glass fibers: 30° vs. 50° for carbon fibers
• Values of failure are much higher for Carbon fibers
Application Example
Loading direction
j
Max. Princ. Stress in Fibers
Max. Princ. Strain in Matrix
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Result: von Mises stress
In the Epoxy phase
Application Example
Layer 31
Min. 0 MPa
Max. 72 MPa(iso.)
Glass fibers(iso.)
Layer 31
Min. 0 MPa
Max. 26 MPa(iso.)
25 MPa(trans.)
Carbon fibers(iso.)
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Result: von Mises stress
In the Fiber phase
Application Example
Layer 33
Min. 0 MPa
Max. 674 MPa(iso.)
Glass fibers(iso.)
Layer 33
Min. 0 MPa
Max. 744 MPa(iso.)
793 MPa(trans.)
Carbon fibers(iso.)
Result: von Mises stress
The value in the epoxy matrix is much more significant when using Glass fibers
Danger of plasticity to occur in matrix
• Max. v.M. stress in epoxy matrix with Glass fibers 71 MPa
• Max. v.M. stress in epoxy matrix with Carbon fibers 25 MPa
To be on the save side, for glass fiber reinforcement nonlinear elastoplastic modeling of the epoxy matrix can be performed with DIGIMAT
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Application Example
Result: Failure indicators (maximum values)
Highest values are found
• In the epoxy matrix under tension
• In the fiber phase under compression
Values are
• Critical for glass fibers under compression
• In general much lower for carbon fibers
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Isotropic Glass
fibers Isotropic Carbon
fibers Transversely isotropic
Carbon fibers FI value Layer nr FI value Layer nr FI value Layer nr Max Epoxy tensile FI 0.408 31 0.148 31 0.129 31
Max Epoxy compression FI 0.182 31 0.057 31 0.075 3
Max fibers tensile FI 0.438 33 0.368 33 0.394 33
Max fibers compression FI 0.835 33 0.435 33 0.593 1
Application Example
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Result: Maximum Principle Strain failure (tension)
In the Epoxy phase
Application Example
Layer 31(iso.)
fmax=0.408
Glass fibers(iso.)
Layer 31(iso.)
fmax=0.129
Carbon fibers(iso.)
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Result: Maximum Principle Stress failure (compression)
In the Fiber phase
Application Example
Layer 33(iso.)
fmax=0.835
Glass fibers(iso.)
Layer 33(iso.)
fmax=0.435
Carbon fibers(iso.)
What happens upon switching from an isotropic to a transversely isotropic material model for the Carbon fibers?
For compression failure in Epoxy and Fibers
• Maximum values are reached for the same layer for isotropic material model
• Maximum values are reached for different layers for transversely isotropic material model
• Values are ~30-40% higher for the transversely isotropic material model
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Isotropic Glass
fibers
Isotropic Carbon fibers
Transversely isotropic Carbon fibers
FI value Layer nr FI value Layer nr FI value Layer nr
Max Epoxy tensile FI 0.408 31 0.148 31 0.129 31
Max Epoxy compression FI 0.182 31 0.057 31 0.075 3
Max fibers tensile FI 0.438 33 0.368 33 0.394 33
Max fibers compression FI 0.835 33 0.435 33 0.593 1
Application Example
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Result: Maximum Principle Stress failure (compression)
In the Carbon Fiber phase
Application Example
Layer 33 (iso.)
fmax=0.435
Layer 1(trans.)
fmax=0.593
Layer 33(trans.)
fmax=0.442
Summary
DIGIMAT enables the coupling between processing and finite element simulation based on one unique approach to material modeling
• All major FEA codes accessible
• All major injection molding codes accessible
• Drapage added with version 4.2.1/4.3.1
The concept of multiscale modeling was successfully applied to design of a wind turbine blade
• ANSYS Composite Pre/Post was coupled with ANSYS implicit solver using DIGIMAT material description
• Failure was investigated on the phase level of the material
• It was shown that it is important to take into account transversely isotropic material models when describing carbon fibers
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DIGIMAT FOR CONTINUOUS FIBER
REINFORCED COMPOSITES
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T h a n k y o u f o r y o u r a t t e n t i o n !
w w w . e - X s t r e a m . c o m
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