Elastic and failure characteristics of additive manufactured thin wall lattice structures with defects

Abstract

The design and realization of lightweight thin wall lattice structures assisted by additive manufacturing (AM) has the potential for a broad range of engineering applications. Due to the more pronounced material and feature defects that commonly occur with AM lattice structures, the application of these structures are currently hindered by the lack of adequate understanding of the effects of material defects on various structural performance, including the fracture characteristics. In this work, an analytical modeling-based analysis was carried out with two types of lattice designs, including the re-entrant auxetic and the diamond structures, in order to understand the effect of material defects on the elastic and fracture characteristics of these structures. The material defect characteristics were represented by introducing material property variability (strength and elastic modulus) functions using stochastic normal distribution functions, which were experimentally established in this study. The models provided good predictions of various fracture characteristics of the lattice structures fabricated by laser powder bed fusion AM (L-PBF-AM) process. Furthermore, the models were employed to investigate the effect of varying material property variabilities on the fracture characteristics of the two types of lattice structures. The results showed that the existence of material property variability not only result in reduced initial fracture strength, but also lead to some unexpected characteristics such as the increase of retaining strength and the divergence of fracture patterns. In addition, it was found that the auxetic and diamond structures exhibit significantly different sensitivities to material property variabilities, which translates into various implications for their use in different potential applications.