Composite materials play a crucial role for light weight applications, but the analysis of their behavior is challenging due to the highly anisotropic behavior and the complex damage mechanisms they exhibit. The expensive, time consuming and often impracticable experimental tests for the study of composites can be supplemented or replaced by simulation.
The ElastoDict module helps characterizing the mechanical properties of composites, to understand and optimize the material using accurate simulations on the 3D microstructure.
For example, it is possible to carry out simulations of anisotropic stiffness, damage and material failure, which can also be seen directly on CT images when examining existing materials.
The properties of new material designs can be computed on 3D structural models, which can be created e.g. with FiberGeo. The exact results at the microstructure scale can be used to improve component simulations.
Damage in a carbon and steel fiber reinforced epoxy matrix
3-point bending test of a closed-cell foam
Compression of a metal foam modeled from µCT scans
Using simulation to find answers to mechanical properties and deformation questions is key not only for composites, but also for porous materials. For example, the ElastoDict module can be used to simulate how the clamping pressure changes the structure of a gas diffusion layer (GDL) in a PEM fuel cell, or how the properties of rock samples change under in-situ conditions.
All these ElastoDict simulations run at high-speed and in a extremely memory-efficient way with the FeelMath solver integrated in ElastoDict and developed at the Fraunhofer ITWM.
Three options can be chosen in the ElastoDict module:
AF computes analytic approximations and bounds for the linear elastic properties of complex micro-structures. The computation is very fast, as no partial differential equation is solved, and gives a first approximation of the material behavior.
VOX accurately computes the linear elastic properties of complex micro-structures by solving the corresponding partial differential equation on the 3D image or model. The results include the local von Mises stress (revealing possible points of material failure), the complete stiffness tensor, and the information on the orthotropic, transversal isotropic or isotropic character of the material, indicative of directionally dependent properties. Additionally, many post-processing steps can be carried out on the VOX results.
LD simulates nonlinear large deformations. For example, a standard tensile experiment in an arbitrary direction of the 3D micro-structure can be set up. The models of the constituent materials might contain damage, failure, plastic deformation, viscous effects, and many more. To model the constituent materials, Abaqus UMAT’s can be used to include all kinds of possible effects in the nonlinear simulation. Results of the simulation are e.g. a strain-stress curve and local information on the regions where damage sets in and the material ends up failing. Cyclic load experiments or shear experiments are also possible. The LD simulation also delivers deformed 3D structures from each computed deformation step for visualization and further analysis.
Examples of ElastoDict applications
- Computations for composite materials:
- thermal expansion.
- anisotropic elastic properties.
- large deformations including damage, failure, plastic deformation and other effects.
- Computations for sectors of the Oil and Gas industry:
- anisotropic elastic properties of rock, like bulk modulus.
- in-situ conditions (compression) of rock samples.
- Computations for electrochemistry:
- compression of gas diffusion layers (GDL) in fuel cells.
- Computations for filtration simulation:
- compressed structure of nonwovens, like filter media and paper dewatering felts.
- Computations of calendering of metal wire mesh.
Rock Wool Compression-Uncompressed
Rock Wool Compression-Compressed
Strain stress curve
Strain simulation in Bereas sandstone (Von Mises Stress)
Additional modules needed?
The GeoDict Base package is needed for basic functionality.
The ElastoDict module works on 3D (micro-) structure models that can either be a segmented 3D image (µCT-scan, FIB-SEM) imported with the ImportGeo-VOL module, or a 3D material model created with one of the GeoDict Modules for Digital Material Design, e.g. the FiberGeo module for nonwovens and composites with fibrous reinforcement.
The FiberFind module is required for computations on µCT-scans of composites using non-isotropic constituent materials, like carbon fibers. FiberFind estimates and delivers the model’s local fiber orientation which can be used in ElastoDict for mechanic properties simulations.
- The result of a large deformation simulation is again a 3D structure model, e.g. for a porous material, a compressed nonwoven. The FlowDict module computes the flow properties of this deformed porous structure, such as the permeability at a certain compression level. Of course, the other properties of the deformed structure can also be computed.