Estimating Strength of Lattice Structure Using Material Extrusion Based on Deposition Modeling and Fracture Mechanics

Geometrical complexity in lattice 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. This initiates cracks between layers and increases possibility of fracture by crack propagation. As a result, a lattice structure fabricated by material extrusion tends to fail at significantly lower stress than estimated strength without consideration of fracture mechanism. The goal of this research is to estimate strength of material extruded lattice structures considering bonding strength among layers. To achieve this, the bonding strength is determined based on a deposition process modeling scheme and fracture mechanics analysis. A two-layer deposition model is generated to investigate deposited geometry, and the effective interlayer-bonding strength is calculated using a cohesive zone model (CZM) and peel tests. The resulting strength is incorporated into the property-estimation procedure.