Probabilistic analysis of additively manufactured polymer lattice structures

Filigree lattice structures are sensible to geometrical imperfections and the scatter of material parameters which all depend on the stability of the manufacturing process. The aim of this study is to analyze these effects for polymer lattice structures and incorporate them in a finite element model for robust design. Micrographs of lattice structure slices show a smaller diameter for vertical struts. Basic mechanical tests on bulk material exhibit a tension–compression asymmetry which is captured with a Drucker-Prager material model in simulations. Digital image correlation measurements allow to determine true material properties. Plateau stress and failure strain are a result of the biggest flaw in the specimen. Hence, a new model to determine their probability distribution is proposed. This model outperforms standard approaches deriving the probability distribution from the central moments. A spatial correlation of geometric deviations and scatter of the material is investigated with variography subsequently allowing to model the varying properties with random fields. Simulations of dog-bone specimens show that the probability distributions of material properties are captured well. Also simulations of lattice structures are able to represent the probability distributions of their homogenized mechanical properties. The whole stress–strain response and the failure progression agree well with experimental results.