Lightweight design has led to an increased use of materials with complex microstructures such as porous metals or ceramics or 3D printed lattice structures. Besides such intended porosity, manufacturing processes like 3D printing, casting or injection molding inevitably lead to unintended porosity which also needs to be taken into account in the characterization of mechanical properties.
As a consequence, there is an increased need for micromechanics simulations to determine the effective mechanical properties of materials and components with cellular and porous microstructures. Classical FEM simulation of such complex domains may not always be feasible because it requires the generation of geometry conforming meshes which must be fine enough to capture all relevant geometric details on the one hand, but coarse enough to keep the effort for mesh generation and computation at a practical level on the other hand.
Recently, immersed-boundary finite element methods have been used to overcome the meshing problem. Such methods do not require the generation of a geometry-conforming mesh and are suited for the simulation of arbitrarily complex domains. This approach is implemented in the Structural Mechanics Simulation module of VGSTUDIO MAX by Volume Graphics and works directly on CT scans which accurately represent complex material structures and internal discontinuities.
This simulation approach was validated against both a classical FEM simulation and experimental tests. For a solid cube and a strictly regular cubic lattice made from Ti6Al4V, the simulated effective Young’s modulus and the maximum local stress were in good agreement with a classical FEM simulation. For two types of additively manufactured AlSi10Mg components, a tension rod and a bionically optimized aeronautic structural bracket, the predicted and measured tensile strengths and the locations of the first crack occurrences showed a good correlation.
The simulation approach presented here provides a realistic, low effort and validated method for the determination of stress distributions and displacements in material probes or components with cellular, porous or otherwise complex microstructures under external loads and allows to determine their effective elastic properties.