Impact behaviour of functionally graded lattice structures fabricated by additive manufacturing

Abstract

Lattice structure is increasingly popular for application in aircrafts, motor-vehicles and bone implants due to their superior strength to weight ratio. With the recent development of additive manufacturing technology, it is more viable to fabricate metallic lattice structure. The scope of this project is to investigate the compressive strength of uniform and functionally graded lattice by numerical method. The stress in uniform lattice drops after the first failure and when the sheared off section comes in contact with the bottom plate, the stress increases. This is also known as the plastic zone which the energy absorption is highest. When the lattice is compressed further, it reaches the densification zone. In FGM lattice, the diameter of strut in the lattice are varying from layer to layer. During compression, failure occurs at the layer with the thinnest strut followed by the second thinnest strut. The failure mode in FGM lattice yield a more predictable trend compared to uniform lattice in compression testing. In this project, the 3 lattices to be analyse are C1 uniform, C1 FGM and C2 uniform. 3 methods were tested to create the Abaqus model for the analyses. The first 2 analyses are the comparison between Implicit and Explicit analysis. The following analyses are the comparison for the time period optimisation. The last analysis is the comparison for the interaction between the lattice and the compression plates. In C2 uniform, the failure mode of the experimental and the analysis is in good agreement with each other. Both C1 uniform and C1 FGM overall performance of the numerical result is not in good agreement with the experimental. Out of the 3 lattice analyses, only C2 uniform is in some agreement to the experimental results.