A technical approach toward pre-crack generation and its effect on the fracture behavior of polymeric materials

Abstract

Regarding the urgent need for a proper pre-crack generation method in polymeric materials, this study addressed the design and fabrication of a broaching machining apparatus. The performance of this device was examined by preparing polyvinyl chloride (PVC) samples with high sensitivity to the crack-tip radius. Pre-cracks generated by broaching and slotting and then examined by SEM analysis. The fracture parameters were determined by the essential work of fracture (EWF) method. Studies indicated that the energy required for crack growth was on average 24 % lower in the broached samples, suggesting a higher stress concentration in the crack-tip by the broaching approach. The numerical analysis also revealed the more coincidence of the modeled energy values with the broaching method results, further highlighting the higher resemblance of the cracks made by this method to the ideal cracks. Interestingly, the radius of the plastic region in the slotting method was three times larger than in the broaching method, indicating the sharper tip of the pre-cracks in the broaching method. The application of the broaching method for pre-crack generation can lead to more accurate results in the mechanical fracture tests.