Elasticity-Controlled Jamming Criticality in Soft Composite Solids

TL;DR

This study reveals how the mechanical response of soft composite solids near a shear-jamming transition can be controlled through elasticity, providing a new framework for designing materials with programmable properties.

Contribution

It introduces a criticality framework linking composite mechanics with particle jamming, advancing understanding of dense soft elastomer behavior.

Findings

Strain-stiffening is governed by shear-jamming critical scalings.

The framework quantitatively predicts mechanical responses across parameters.

Designing inclusion jamming properties enables control of composite mechanics.

Abstract

Soft composite solids are made of inclusions dispersed within soft matrices. They are ubiquitous in nature and form the basis of many biological tissues. In the field of materials science, synthetic soft composites are promising candidates for building various engineering devices due to their highly programmable features. However, when the volume fraction of the inclusions increases, predicting the mechanical properties of these materials poses a significant challenge for the classical theories of composite mechanics. The difficulty arises from the inherently disordered, multi-scale interactions between the inclusions and the matrix. To address this challenge, we systematically investigated the mechanics of densely filled soft elastomers containing stiff microspheres. We experimentally demonstrated how the strain-stiffening response of the soft composites is governed by the critical scalings in the vicinity of a shear-jamming transition of the included particles. The proposed criticality framework quantitatively connects the overall mechanics of a soft composite with the elasticity of the matrix and the particles, and captures the diverse mechanical responses observed across a wide range of material parameters. The findings uncover a novel design paradigm of composite mechanics that relies on engineering the jamming properties of the embedded inclusions.