Energy Absorption of Additively Manufactured Lattices

Abstract

Cellular solids are characteristically excellent energy absorbers due to their capacity to store large amounts of energy through compression. A bioinspired design approach identified the Pomelo fruit (Citrus Maximus) as a biological role model for energy absorption. Fruit peels’ biologically most important functions lies in the need to provide protection of the seeds from mechanical damage or other negative environmental influences. This qualifies such biological structures as role models for the development of novel structures that protect commodities from damage. The main structural principle extracted from the Pomelo is a density graded strategy. With maturing additive manufacturing (AM) technologies allowing unprecedented control over structural topology, controlled lattice structures can now be investigated . Using a class of AM, selective laser sintering (SLS), lattice structures were fabricated out of polypropylene and subjected to static and dynamic compressive loadings. The lattices were designed to determine the influence of the biomimetic density grading, cell shape and cell size in 3 distinct lattice configurations. Quasi-static simple compression results are compared to analytical micro-mechanical models, finite element method simulations and digital image correlation. Dynamic impact data is assessed using high-speed camera images and evaluated with an analytical momentum analysis. Data analysis is discussed and it is concluded that the density grading strategy beneficially influences the energy absorption. This is attributed to a combination of local plasticity manipulation and higher densification strains in static regime. In dynamic tests, the collapse initiation trigger led to controlled, more gradual collapse with lower corresponding loads.