challenges in the simulation of car body structures made from composite materials
TRANSCRIPT
Challenges in the Simulation of Car Body Structures made from Composite Materials Jochen Döll, Nico Feindler, Audi Lightweight Design Center
5th European HyperWorks Technology Conference,
Bonn 7.-9. Nov. 2011
2
Agenda
► Trend towards Multi-Material-Design including CFRP applications
► Challenges for the simulation process
► Characteristics of composites - methods and quality of prediction
► Progresses in the simulation of FRP body structures
► Simulation of CFRP-crash-structures in full vehicle models
► Ply book definition of a front bonnet
► Summary
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
3
Trend towards Multi-Material-Design Reversal of the weight spiral
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
• Initiation by
lightweight
body design
• light, sportive,
less fuel consumption
• Lightweight design
measures in detail (all
departments)
• Downsizing
Power Train
• Secondary effects
e.g. Fuel tank etc.
We
igh
t R
ed
uct
ion
- kg
4
Trend towards Multi-Material-Design Flexible material architectures driven by product and demands
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
6
Challenges for car body design process New tasks to develop composite car body structures
► Predictive material models for the virtual rating and advance computing of body
functions, especially in crash situations:
► A precondition for establishment of the material in series projects
► Selection of FRP and assessment of suitability in body structures with a flexible
material policy, in particular with regard to crash disciplines
► Target: Lighter than Audi-Space-Frame - ASF
► A suitable CAE-CAD data interface
► Optimization tools with regard to the wide variety of design parameters
► Delta Alpha simulation and forecasting of critical construction methods
► Continuous simulation of processes and properties
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
7
Modeling composites - behavior and quality of prediction Anisotropy und Stiffness (linear elastic)
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
► Covered by CLT, included in most FE-Solvers
► Additional effort for defining fiber orientations
► Methods for optimization fiber orientation and stack up are established and in use (Altair, Optistruct)
Time and effort Q
ua
lity
of
pre
dic
tio
n
high
hig
h
Stiffness and anisotropy
9
Modeling composites - behavior and quality of prediction Ply Failure
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
► Essential for any crash simulation
► Needs extensive material characterization
► Know how for fitting and use of suitable material models (combined damage and ply failure models in use)
Time and effort Q
ua
lity
of
pre
dic
tio
n
high
hig
h
Ply Failure
10
Modeling composites - behavior and quality of prediction Failure between plies - Delamination
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
► Failure mode leads to significant reduction of load carrying capacity and structural integrity
► Modeling in full vehicle models possible but moderate accuracy (coarse discretization)
► Needs FE-discretization through the thickness and characterization of additional material parameters Time and effort
Qu
ali
ty o
f p
red
icti
on
high
hig
h
Delamination
11
Modeling composites - behavior and quality of prediction Example – Pole test of an Al/CFRP floor structure (Ply failure + Delamination)
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
Test Simulation
Conta
ctforc
e P
ole
Intrusion pole
13
Time and effort Q
ua
lity
of
pre
dic
tio
n
high
hig
h
Crushing
Modeling composites - behavior and quality of prediction Crushing / Fragmentation
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
► Classic FE-modeling doesn’t work on macroscopic level for that failure mode
► Most state-of-the-art approaches are not satisfying (non predictive, many complex hardware tests)
► New efficient numeric method with simple material testing developed and in use at Audi
15
Ply book definition using Optistruct Engineering of a lightweight front bonnet
Jochen Döll, Daniel Werum, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
Explosion view of CFRP-concept bonnet
► Task
► Ultra lightweight design
► Meet pedestrian protection
requirements
► Design same properties compared
to aluminium version (series) for
stiffness, deformation under wind
load and HIC
► Adopt geometry of aluminium
concept (tooling was fix)
16
Ply book definition using Optistruct Sensitivity analysis of fibre orientation using free size optimisation
0° 90°
45° - 45°
Specific fibre orientations are sensitive when matching the orientation of an existing load path
Jochen Döll, Daniel Werum, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
17
Ply book definition using Optistruct Interpretation and engineering of an optimal fabric
90° +x°
Realisation via simple Triax-NCF Fibre orientation fits load paths
• Triax Fabric for optimal stiffness
• Thickness sizing according HIC-Targets
Jochen Döll, Daniel Werum, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
18
Ply book definition using Optistruct Performance of manufactured CFRP front bonnets
P05L
Simulation:
Test 1-3:
Head Impact Deformation at Wind Load [mm]
Test / Simulation
► Good correlation between simulation and test
► CFRP-bonnet concept fulfils all requirements and functions
► 30 % lighter than full-aluminium bonnet (series)
Jochen Döll, Daniel Werum, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011
19
Summary
► Realization of advanced Multi-Material-Concepts including composite materials
needs suitable simulation tools useable within industrial development routine
► Aspects like anisotropy and ply failure important for basic design process are well
covered with current FE-Codes and simulation techniques
► Simulation and prediction of delamination and especially crushing mode in full
vehicle models is a challenge (not state of the art in many FE-Codes)
► At Audi a new method is developed and used to design and predict the behavior of
new CFRP crash structures
► To ensure maximum lightweight potential composite materials have to be designed
anisotropic as much as possible by using composite optimization tools (Altairs
Optistruct)
Jochen Döll, Nico Feindler, Challenges in the Simulation of Car Body Structures made from Composite Materials, 09.11.2011