Increasing fracture toughness via architected porosity

Abstract

Fracture toughness, rather than strength, is often the limiting factor of structural materials. Developing new base materials with improved fracture toughness often takes more than a decade. Alternatively, topological design has recently been expanded by additive manufacturing. In the present study, architected planes of internal porosity mimicking a weak interface were found capable of arresting and deflecting a propagating crack, delaying fracture. This concept was demonstrated experimentally in solid beams of polymeric 3D printed material, and in gyroid metamaterials constructed from either a brittle polymer or stainless steel. Improvements in fracture toughness ranged from 22% to 300% depending on the material. Especially with topological optimization, toughening via designed porosity provides an avenue for cost-effective and simple toughening across a range of materials.

Keywords

• Fracture toughness
• Gyroid
• Crack path
• Additive manufacturing