A Relationship between the Fracture Strength and the Fracture Surface Markings of Brittle Plastic Plates

An experimental relationship between the fracture strength and the parabola marking density on the fracture surface has been investigated on the plate material of the unsaturated polyester resin. Fracture tests were conducted both on mild notch tensile specimens and on single edge notch impact specimens having the arbitrary notch depth and radius. The fracture strength in tension decreases with the length to width ratio in the outside loading method and increases with that in the inside loading method. The fracture energy decreases in different degrees in each method of loading. The parabola marking density on the fracture surface increases as the fracture strength increases in tension. The fracture energy and the parabola marking density increase with the decreases in the notch depth and/or sharpness in Charpy impact tests. Consequently, the parabola marking density increases with the increases in the fracture strength and energy both in tension and impact tests. The results are discussed on the energy point of view by using the analytical fracture markings and reasonable conclusion is drawn.