Estimating failure of material extrusion truss structures based on deposition modeling and a cohesive zone model

Geometrical complexity in truss structures yields large bounding surfaces to be approximated during additive manufacturing (AM) processes. In material extrusion, approximation of geometries using finite-sized thin filaments introduces defects such as voids and gaps in as-fabricated geometries. These can serve as crack initiation sites and increase possibility of fracture by crack propagation. As a result, a truss structure fabricated by material extrusion tends to fail at significantly lower stress than estimated strength without consideration of fracture mechanisms. In this paper, we propose a strength estimation framework for truss structures fabricated by material extrusion that is based on process modeling simulation and a cohesive zone model (CZM). The proposed method assesses two failure criteria: elastic failure and fracture. To evaluate geometrical characteristics of initial cracks embedded by layer-by-layer deposition process, a two-layer deposition model is generated using process modeling simulation. The effective interlayer-bonding strength is estimated based on a cohesive zone model analysis and double cantilever beam (DCB) tests. Resulting embedded crack length and interlayer-bonding strength is integrated into the strength-estimation procedure. (C) 2018 Elsevier Ltd. All rights reserved.