Experimental Study of Size Dependence of Fracture Toughness of PMMA

In order to study the size dependence of the fracture toughness,pure mode I and pure model Ⅱ fracture tests for polymethyl methacrylate(PMMA) were performed under quasi-static loading by using central cracked circular disk specimen.The experimental results show that the fracture toughness of PMMA is dependent on the relative crack length α,and the pure model I fracture toughness and the pure model Ⅱ fracture toughness decrease with increasing the relative crack length α.The relative crack length has a larger effect on the pure model I fracture toughness,and a smaller effect on the pure model Ⅱ fracture toughness.In addition,the experimental results also show that the pure model Ⅱ fracture toughness of PMMA is less then the pure model I fracture toughness.