Comparison of Mechanical Properties Between PE80 and PE100 Pipe Materials

摘要

Mechanical properties, including yield stress, relaxation behavior, moduli (elastic modulus at the strain of 0.5% and strain hardening modulus at strains above 70%), viscous stress, and quasi-static stress, are compared between polyethylene (PE) pipes that are made of PE80 and PE100 resins. The mechanical properties are measured using D-split tensile test on modified notched pipe ring specimens. The comparison includes the influence of strain rate (by the change of crosshead speed) on the yield strength and influence of pre-strain on the relaxation behavior and the modulus values. A two-stage approach is used to characterize the influence of pre-strain on the moduli, to ensure that viscous recovery from the first-stage of the test, to introduce the pre-strain, does not affect the modulus measurement from the second-stage test. The results show that elastic modulus, yield stress, strain hardening modulus, viscous stress, and quasi-static stress for PE100 are higher than those for PE80, but PE80 shows higher resistance to stress relaxation. The results also show that with the increase in the pre-strain level, the elastic modulus drops but the strain hardening modulus remains relatively constant.