2022 Volume 48 Issue 1 Pages 2-9
Fiber-reinforced thermoplastics (FRTPs) have superior strengths and elastic moduli compared to most other materials and are lighter than metal and ceramic materials. The mechanical properties of FRTPs are broadly dominated by those derived from the material and from the interface between the fibers and plastics. In recent years, research on the strength of this interface has been active, and various evaluation methods have been proposed. These methods target a single fiber and do not assume a dispersed state in which multiple fibers are present inside the composite material. In particular, using the evaluated values to predict the strengths and impact resistances of composite materials is difficult because the interaction force generated between fibers is ignored. We propose a short beam method to determine the interfacial shear strength of FRTP injection-molded products, and we verify the validity of the method. Analysis of the obtained results based on the theory proposed in this study found that, in terms of fiber content, the interfacial shear strength has a small dependence, whereas the interfacial interaction force and solidification temperature have a considerable dependence. It is also clarified that the solidification temperature of polypropylene/glass fiber is the crystallization completion temperature.
