Honeycomb-patterning in soft polymer networks: using geometry to manipulate toughness and failure

Abstract

Hexagonal (i.e. honeycomb) patterning has been previously shown to increase overall material toughness as a function of geometry when the base lattice material is brittle in nature. However, similar design parameters have yet to be identified for soft materials such as polymer networks that are viscoelastic in nature. Here, systematic stress-strain experiments of honeycomb-patterned lattice sheets based in poly(ethylene glycol) explore the failure behavior as a function of honeycomb geometry as well as base material rigidity. Experimental results demonstrate that geometry impacts Young’s modulus and alters failure mode and toughness differently than previously observed in other material classes. Specifically, honeycomb structures of smaller dimensions enhance tortuosity during crack propagation while also allowing for rotations and deformations that dissipate stress, enabling simultaneous enhancement of toughness and strength.