Nonmonotonic fracture behavior of polymer nanocomposites

TL;DR

This paper investigates how varying silica nanoparticle content affects the fracture behavior of rubber composites, revealing an optimal filler concentration that maximizes fracture resistance through experimental and theoretical analysis.

Contribution

It introduces a modified Griffith theory to relate nanoparticle content with fracture behavior, identifying an optimal filler level for maximum strength.

Findings

Small silica amounts increase fracture stress and strain.

Excess filler causes brittleness and reduces fracture resistance.

An optimal intermediate filler concentration exists.

Abstract

Polymer composite materials are widely used for their exceptional mechanical properties, notably their ability to resist large deformations. Here we examine the failure stress and strain of rubbers reinforced by varying amounts of nano-sized silica particles. We find that small amounts of silica increase the fracture stress and strain, but too much filler makes the material become brittle and consequently fracture happens at small deformations. We thus find that as a function of the amount of filler there is an optimum in the breaking resistance at intermediate filler concentrations. We use a modified Griffith theory to establish a direct relation between the material properties and the fracture behavior that agrees with the experiment.