Failure and energy absorption characteristics of advanced 3D truss core structures

Lightweight core structures with high strength and high potential for energy absorption are crucial for a range of applications in the aerospace and automotive industry, but data is lacking for validated failure prediction. We undertake both compression and shear tests to determine and successfully predict the energy absorption capacity of Ti-based Kagome and atomic lattice truss configurations (bcc, f2cc and f2bcc) built by selective laser melting. The failure characteristics are determined through a combination of experimental tests and numerical finite element simulations. The novel failure prediction approach for truss structures utilises a ductile metallic damage model with triaxial stress state dependence and results in very good agreement of deformation patterns, predicted failure strain and failure location. These findings result in the development of optimum design strategies for truss-based structures. The four unit cell structures are ranked against traditional core structures with the help of comprehensive Ashby design charts for both strength and energy absorption. Of the four lattice types investigated, Kagome structures perform best and also show superior strength compared to traditional core materials for the same density, while their energy absorption capacity is competitive with titanium and aluminium honeycomb materials.