Numerical and experimental investigation of a variable cross-section hollow BCC lattice subjected to axial and oblique impact loadings

Light-weight lattice materials are usually and inevitably subjected to impact scenarios from various loading directions in practical engineering applications. Oblique impact loadings have a strong effect on energy absorption of lattice materials. In this work, the reinforced variable cross-section hollow (RVCH) lattice structures were proposed to improve the crashworthiness behaviors. The axial and oblique impact experiments of RVCH lattices were conducted by a drop tower testing system to study the dynamic mechanical response and energy absorption performance. In addition, the finite element (FE) models of RVCH lattices under impact loading conditions were established, and more oblique impact conditions with the loading angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees and 40 degrees were discussed based on simulation methods. Moreover, the effects of the reinforcing strips and different gradient configurations on the deformation behaviors and energy absorption characteristics of RVCH lattices were discussed. The deformation behaviors of RVCH lattices subjected to the axial impact loadings is mainly the sequential layer-by-layer failure mode. However, the deformation mode of RVCH lattices under the oblique impact turns into the locally struts layer-wise collapse mixed with the holistic shearing deformation. The reinforcing strips of the lattice structure can provide better tensile strength and bending strength for the RVCH lattices. As a result, energy absorption performance of RVCH lattices can be refined at different impact angles, especially for the 40 degrees oblique impact condition. The gradient design configurations have positive effects on energy absorption characteristic of RVCH lattices compared with that of the lattices with uniform unit-cells. The results can provide novel insights on the design strategy of innovative lattices as a potential energy absorber which can absorb more impact energy under oblique impact loadings.