Fracture Mechanics of Rubber Epoxy Composites

The effect of the addition of rubber micro-particles to epoxy matrix on the mechanical properties and the fracture toughness were investigated. Rubber epoxy composites were prepared with different weight percentages namely, 0, 5, 10, 15, 20, 25, 30 wt pct of rubber. Both quasi-static and dynamic ultrasonic measurements of the elastic modulus were found to decrease by 60 pct, and the critical value of the stress intensity factors was found to increase by approximately 45 pct for the rubber epoxy composites. This was also confirmed with the finite element analysis that had the same increasing trend. The fracture surface morphology reveals rough cleavage fracture in the epoxy matrix with brittle intergranular decohesion caused by the impurity segregation that exhibits relatively high micro-roughness of the fracture surfaces.