Fracture Toughness of Polymer Composites Using Pure Shear Tearing

Background Fracture of particle-polymer composites can diminish their performance in service. Current fracture characterization methods like direct empirical characterization of every composite formulation or micromechanical analysis using finite element analysis can be impractical and cost prohibitive, reducing their value for fracture measurement. Objective Our goal is to validate a straightforward fracture toughness characterization method to describe the fracture toughness of particle-polymer composites. Methods Utilizing pure shear tearing experiments of glass-silicone composites, empirical relationships are constructed to describe the dependence of the elasto-cohesive length and elastic modulus on particle concentration, φ φ , and mean particle diameter, D D . These relationships are combined to describe the critical strain energy release rate of the composite, analogous to fracture toughness. Results The elasto-cohesive length is modeled, capturing the particle reinforcement behavior that leads to a peak value around φ φ ≅ 0.15. Elastic modulus is also empirically modeled, monotonically increasing with φ φ , and is independent of D D , in agreement with literature relationships. The relative accuracies of the fracture toughness model predictions and the causes behind them are discussed. Conclusions The pure shear tearing method provides a simple and fast method to describe the fracture toughness of particle-polymer composites. In the future, this method may be adapted to explore the effects of other formulation characteristics on macroscopic fracture behavior, moving towards an all-encompassing predictive relation.