Dynamic Fracture Analysis of Polycarbonate by the Optical Method of Caustics

Glassy polycarbonate (PC) is a widely used engineering material in industries, since it has high strength and toughness as well as good transparency. However, these advantages of PC can be suppressed by physical aging, especially its dynamic fracture toughness. In addition, the material properties of PC can be changed dramatically after large plastic compressive deformation, and it can show obvious orthotropic behavior. Here, the combined effect of aging and plastic compressive deformation on dynamic facture of PC was investigated by the optical method of caustics. The dynamic reflective method of caustics for orthotropic materials was developed here to study the dynamic fracture property of PC with plastic deformation. The samples were prepared with different extents of plastic compressive strain up to approximately 50% engineering strain, followed by aging with various aging times up to 300 hours. The shadow spot patterns during the fracture processes were recorded by a high speed camera. Results show that the PC with plastic compressive deformation has different fracture toughness even quite different fracture modes on its different orientations. Aging affects the fracture property of PC with or without plastic flow in similar trend. Under large plastic compressive strain, PC has more strong anisotropy and dynamic fracture tolerance, which has great potential for optimal material design.