Influence of Crack Orientation and Crosshead Speed on the Fracture Toughness of PVC Pipe Materials

In many modern engineering applications, designers and manufacturers of Polyvinyl chloride (PVC) pipes are interested in the evaluation of fracture toughness under several operation conditions. The aim of the present work is to investigate the fracture toughness of commercial amorphous thermoplastic PVC materials used in piping applications. The experimental work is carried out using three different specimens’ types: Taper Double Cantilever Beam (TDCB), Three Point Bend (TPB), and Compact Tension (CT). Tests are conducted on specimens with thickness (17, 20, 22, and 26 mm), longitudinal and transverse extrusion orientations, at different crosshead speeds (50–500 mm/min) to calculate the fracture toughness of PVC pipe materials. The experimental work has revealed that the crosshead speed has a significant effect on the fracture toughness at low speed rates. This effect, however, becomes insignificant at high rates since, the fracture behavior becomes brittle. The stress intensity factor $KQ$ is approximately the same in both longitudinal and transverse orientations. The fracture toughness decreases as the specimen thickness increases.