Experimental Study of Elastic-Plastic Fracture Toughness JIC Measurement to Plastic Materials by Reflection Caustic Method

Abstract

The usage of plastic materials that have excellent properties such as light weight and ease of formation has been spreading widely in recent years as an alternative to metal materials. The traditional application of plastic materials has been limited to areas that do not require mechanical strength, and fracture mechanics verification has been disregarded. As a result, elastic-plastic fracture toughness JIC testing method has not been standardized for many plastic materials that show nonlinear fracture at room temperature. The establishment of this testing method would play a significant role in expanding the application of polymeric material in the future. In this paper we describe three methods that have been adopted to measure JIC for polycarbonate and polyethylene terephthalate. The first method is a reflection caustic method that evaluates information about an internal crack from the material surface. The second method is a reflection caustic method using an ultrasonic method which is effective in evaluating an internal crack. In order to verify the effectiveness of these two methods, the R-curve method, which is a standard JIC testing method for metal material, was performed as the third method. These three methods were compared experimentally. It is clear that JIC evaluation by the reflection caustic method is effective in polycarbonate that exhibits nonlinear fracture.