Fracture toughness and auxeticity in disordered metamaterials

TL;DR

This study explores the design of disordered auxetic metamaterials optimized for either high energy absorption or auxeticity, revealing trade-offs and deformation behaviors through simulation and experiments.

Contribution

It introduces a multi-objective optimization approach to design disordered metamaterials balancing auxeticity and energy absorption, validated by experiments.

Findings

Optimal configurations form a Pareto front showing trade-offs.

High auxeticity correlates with lower energy absorption.

Deformation modes vary with optimization targets.

Abstract

Auxetic metamaterials are commonly thought to exhibit favorable mechanical properties, notably high energy absorption. Here we investigate disordered metamaterials obtained from random beam networks by optimizing simultaneously auxeticity and the energy absorbed before fracture. By giving different weights to these optimization targets, we demonstrate that the optimal configurations are connected along a Pareto front where high auxeticity implies comparatively low energy absorption and vice versa. We study the mechanical properties of the resulting metamaterials and characterize the different deformation modes obtained for distinct optimization targets. The simulation and optimization results are validated by comparison with the deformation behavior of additively manufactured samples. Our work provides an illustration of the potentials and limitations of multi-objective optimization in the design of disordered mechanical metamaterials