DIGIMAT: Microscopic Simulation

The software enables engineers to predict the influence of the material microstructure on the performance of the end product. The applications of DIGIMAT (DIGItal MATerial) range from the use as an independent material laboratory over a material interface for structural mechanics (ANSYS and LS-DYNA) to a complete coupling between injection moulding simulations and structural mechanics. This also includes a solution for mapping between different meshes coming from injection moulding and the structural analysis.

The mean field module of DIGIMAT delivers constitutional laws for complex multiphase systems using homogenization theory. For instance, the non-linear properties of glass fiber reinforced plastics can be reproduced on the base of given polymer and filler properties and a given material microstructure.

Homogenization delivers accurate results, is fast and efficient. For the definition of the respective components a broad range of material models is supported:

• Thermo-linear-elastic
• Thermo-elasto-plastic
• Linear visco-elastic
• Elasto-visco-plastic
• Hyperelastic

The fillers can be varied almost arbitrarily in terms of:

• Type  (particles, coated particles or cavities)
• Material   (kept rigid or defined via a constitutional law)
• Form   (aspect ratio)
• Orientation  (random in 1D, 2D or 3D / through orientation tensor)

The homogenized material can be exposed to diverse loads:

• Mechanical / thermo-mechanical
• Traction / shear
• Linear / cyclic

The finite element module of DIGIMAT delivers microstructure models, also called as Representative Volume Elements (RVEs), for the use in ANSYS or LS-DYNA. Almost any microstructure can be generated through the definition of versatile parameters describing the fillers of the composite material. Digimat-FE generates different file formats for the import into the FE software (BREP, IGES, STEP).

FE analysis provides the effect of traction and shear on e.g. the stress or accumulated plastic strain of the composite material.

This detailed insight into the microstructure enables both the optimization of the material as well as a deeper understanding of wear and fatigue under load.

Thanks to the high speed of a homogenization calculation with Digimat to CAE, the software can also be used as a direct material interface to Computer Aided Engineering software. This allows the use of composites from DIGIMAT within ANSYS and LS-DYNA structural FEA. The module is linked to the respective solver through a user-defined subroutine. Therefore DIGIMAT completely replaces the usual material definition and the whole range of non-linear materials becomes available in structural mechanics calculations, including the anisotropic effect of the local microstructure on the behaviour of the simulated assembly.

Digimat to CAE works as a truly bidirectional micro/macro multiscale coupling with significant influence on the simulation results. For example, the fiber orientation in a composite material has a strong impact on the plastic distortions under a traction load.

In addition to the exclusive use as a material interface, Digimat to CAE also permits the coupling of injection moulding simulation with structural mechanics. The local microstructure is strongly dependent on the manufacturing process of the part. In the case of injection moulding, the local fiber orientation results from individual the flow of the polymer melt.

Digimat to CAE reads in the orientation tensors of the injection moulding simulation and, based on this, calculates the microstructure of the composite. Together with the previously defined parameters for the composite, an individual local material can be provided for every point of the assembly. On the FE side of the simulation one resulting advantage is that only one material, the DIGIMAT composite, needs to be defined for the entire structure. Another is the accessibility of non-linear material behavior which fully includes the influence of the local microstructure.

With this approach differences in the microstructure, for example due to a variation of the feed gate, which have a significant effect on the whole assembly can be simulated within structural mechanics. The whole process from die casting to structural mechanics is included in one simulation solution.

With the Map module, DIGIMAT offers a complete solution to this problem. Information from injection moulding as for example the fiber orientation, initial stresses or temperatures can be transferred to structural meshes. It is also possible to integrate single injection moulded parts in whole assemblies of components.

Map is an interactive software which helps to assess the level of difference between the data on the original and the final mapped solution. Map enables structural engineers to generate the optimal mesh refinement and element choice.

The required material data are either entered on a macroscopic level (composite/core) or are generated on a microscopic level (fiber resin/cell) through homogenization. Through easy and intuitive use, Micross is immediately usable also for users who are not familiar with FEM to develop composite sandwich panels through standard numerical bending and shear tests.