Investigation of Fomulation of the Energy Release Rate in the Fracture Mechanics of Short Fiber Composite

Abstract

The aim of the paper is to investigate the fracture of short carbon fiber reinforced PA66 (20wt% fibers) and formulate the formula of the energy release rate GIC. Experimental specimens were injection-molded in end-gated molds with dimension 4×10×80 mm. Most of short fibers are oriented in the same direction of the plastic flow during injection process. The volume fraction of short fibers is about 13%. Very sharp notches (angle 25°, tip radius R=0.015mm) of different depths were created to the edge-sides (narrow sides of the specimens). The experiments have been carried out at the ambient temperature. Charpy impact test was used to examine the impact on specimens. Fracture tests were performed with the machine in the position of edgewise impact according to the standard ISO 179. By observing and analyzing the fracture surfaces of specimens, a fracture mechanism of the short fiber composite has been developed and modeled. Based on the model and the experimental results, the energy release rate GIC can be calculated. As a result, the formula for calculating GIC has been established in order to estimate and predict fracture properties of the material for the unidirectional short fiber composite.