Effect of strain rate, thickness, welding on the J–R curve for polyethylene pipe materials

• Mechanical properties of HDPE are significantly affected by the welding technique.
• For all HDPE specimens the fracture toughness decreases as the thickness increases.
• The fracture toughness of HDPE decreases with decreasing the crosshead speed.

The main purpose of the present paper is to investigate the effect of strain rate, specimen thickness and welding on the fracture toughness for the specimens made from high-density polyethylene (HDPE). The welds at the pipe junction are produced by butt-fusion (BF) welding. Tensile tests specimens are cut longitudinally from the pipe with thickness, T = 30 mm, and are tested at different crosshead speeds (10–500 mm/min), and gauge lengths, G = 20 mm, to determine the mechanical properties of welded and unwelded specimens. Curved three-point bend (CTPB) fracture specimens are used. The effect of specimen thickness variation for welded and unwelded specimens is studied at room temperature, (Ta = 23 °C), and at different crosshead speeds, VC.H, (10–500 mm/min). The study reveals that the crosshead speed has a significant effect on the fracture toughness of both welded and unwelded specimens. The fracture toughness, JIC, is greater for unwelded than welded specimen.