Bending behavior of additively manufactured lattice structures: numerical characterization and experimental validation

TL;DR

This paper investigates the bending behavior of additively manufactured octet-truss lattice structures using a numerical framework that incorporates manufacturing defects, validating models with experimental data and exploring high-order continuum theories.

Contribution

It introduces an immersed image-to-analysis framework with the Finite Cell Method to efficiently analyze as-manufactured lattice geometries and assesses the applicability of beam models for predicting bending behavior.

Findings

SLM lattices show size effects requiring advanced modeling.

The FCM effectively incorporates manufacturing defects into analysis.

Classical and strain gradient beam theories are validated for lattice structures.

Abstract

Selective Laser Melting (SLM) technology has undergone significant development in the past years providing unique flexibility for the fabrication of complex metamaterials such as octet-truss lattices. However, the microstructure of the final parts can exhibit significant variations due to the high complexity of the manufacturing process. Consequently, the mechanical behavior of these lattices is strongly dependent on the process-induced defects, raising the importance on the incorporation of as-manufactured geometries into the computational structural analysis. This, in turn, challenges the traditional mesh-conforming methods making the computational costs prohibitively large. In the present work, an immersed image-to-analysis framework is applied to efficiently evaluate the bending behavior of AM lattices. To this end, we employ the Finite Cell Method (FCM) to perform a three-dimensional numerical analysis of the three-point bending test of a lattice structure and compare the as-designed to as-manufactured effective properties. Furthermore, we undertake a comprehensive study on the applicability of dimensionally reduced beam models to the prediction of the bending behavior of lattice beams and validate classical and strain gradient beam theories applied in combination with the FCM. The numerical findings suggest that the SLM octet-truss lattices exhibit size effects, thus, requiring a flexible framework to incorporate high-order continuum theories.