Improvement of Static and Fatigue Durability of CFRTP Joint Using Bite Plate and Modified PP Film

Abstract

This study aims to propose a new joint technique to improve the static and fatigue durability of the bolted joint of a carbon fiber reinforced thermoplastic (CFRTP) plate. A pair of steel plates called “bite plates” was prepared; the plate surfaces were machined using a V-shaped cutter. Three types of polypropylene (PP) film were pressed, which included normal PP film and PP film modified by the addition of 0.5 or 1.0 wt% sub-micron glass fiber. A CFRTP plate and pair of bite plates were used to assemble the joint specimen using heat pressing with the paired PP film. Specimens of each bite plate and PP film were used for tensile shear and tensile-tensile fatigue tests. Test results demonstrated that the joint efficiency and fatigue durability were improved by using a bite plate and modified PP film. A detailed investigation of the joint under a loading condition revealed that the load transfer along the width direction of the specimen was enhanced by using a bite plate. The fractured surface observation also revealed that the interfacial shear strength between the PP and carbon fiber was improved. As such, our joint efficiency improvement mechanism was validated by the enhancement in the load transfer to the surface of the CFRTP due to the increase in its interfacial shear strength.