Compressive properties and energy absorption of BCC lattice structures with bio-inspired gradient design

Inspired by the gradient structure of the nature, two gradient lattice structures, i.e., unidirectional gradient lattice (UGL) and bidirectional gradient lattice (BGL), are proposed based on the body-centered cubic (BCC) lattice to obtain specially designed mechanical behaviors, such as load-bearing and energy absorption capacities. First, a theoretical model is proposed to predict the initial stiffness of the gradient lattice structure under compressive loading, and validated against quasi-static compression tests and finite element models (FEMs). The deformation and failure mechanisms of the two structures are further studied based on experiments and simulations. The UGL structure exhibits a layer-by-layer failure mode, which avoids structure-wise shear failure in uniform structures. The BGL structure presents a symmetry deformation pattern, and the failure initiates at the weakest part. Finally, the energy absorption behaviors are also discussed. This study demonstrates the potential application of gradient lattice structures in load-transfer-path modification and energy absorption by topology design. [Figure not available: see fulltext.].