Relationships among Fracture Testing Condition, Crack Velocity and Fracture Surface Marks in a Polycarbonate Resin

We have reported that brittle fracture strength and crack propagation velocity change with a specimen design, a fracture type, a loading location and so on in a plastic sheet specimen of unsaturated polyester (UP) or polymethyl methacrylate (PMMA) resin. It is also reported that the both-ends-closed mark (BECM) like an ellipse and the one-end-opened mark (OEOM) like a parabola or a hyperbola are observed on a fracture surface of the specimens, and their shape, size, total number of the marks change with fracture strength and crack velocity. Here, crack velocity and fracture surface marks of a polycarbonate (PC) resin were measured in a tension and a dynamic bend tests at room temperature. The crack velocity of tensile test was about 450m/s in maximum, and the crack branching phenomena appeared which caused roughening of the fracture surface. On this surface, there were many bands and striations without any marks of BECM and OEOM. As the crack propagated, the crack velocity decreased to 250m/s&acd