Modeling of Pyramidal Lattice Structures Compared to Tomographic Analysis

Abstract

Architectured materials can now be easily produced thanks to recent developments in additive manufacturing processes. Such mesostructures have great potential to supplement the classical materials used for shock absorption in multiple protective applications (with expanded polystyrene (EPS) or ethylene-vinyl acetate (EVA) components), conferring security, comfort and lightness. Beyond the selected raw material, the choice of the lattice pattern and the way it is repeated directly affects the macroscopic mechanical response of the manufactured structure under compressive loading. With respect to the colossal amount of lattice shapes, a cost effectiveness design of experiment is needed in order to efficiently find the right compromise between geometries, material, and applications. Based on identified mechanical properties of a thermoplastic polyurethane (TPU) material selective laser sintered, and the characterization of several lattice structures, we propose a relevant numerical modeling tool of pyramidal lattice structures and validate its reliability and robustness.The finite element model (FEM) is based on a beam design of trusses with parameterized stiffeness at the vertices (beam intersections). The patterns studied are octet-structures of 1mm diameter beams with 35°, 45° and 55° angles. In parallel, X-Ray computed tomographic analysis performed during compressive tests provided the macroscopic static behavior and kinematic behavior of the considered structures. The tomographic images are analyzed and directly confronted to the FEM results, which enables us to improve and assess our model.