Jamming Criticality in Dense Soft Composites

Grains dispersed in a liquid solvent can jam into a solid under shear. This jamming transition is crucial for controlling the non-Newtonian behaviors of dense granular suspensions. However, for soft composites made of particles in a soft matrix, the role of the jamming transition in nonlinear mechanics remains unclear. Traditional composite mechanics theories, like the classical Eshelby model, work well for dilute composites but struggle to describe interactions in dense composites. In this work, we experimentally show that the strain-stiffening response of dense soft composites is governed by critical scalings near the shear-jamming transition of the particles. By proposing a criticality framework that links the overall mechanics to the elasticity of both the matrix and the particles, we effectively capture the diverse mechanical responses of dense soft composites across a wide range of material parameters. Our findings reveal a new design approach for composite mechanics that focuses on engineering the jamming properties of the embedded inclusions.