Evaluation of Elastic-Plastic Fracture Toughness J_<IC> of High Density Polyethylene

Abstract

Cylindrical non-fused sharp notch is produced between the Erectro-fusion Polyethylene joint and the outer circumferential edge of the Polyethylene pipe in their fusing process. Elastic-plastic fracture toughness J_<IC> of Polyethylene is required for the joint to be designed safely based on fracture mechanics. In the present study, three points bending tests are conducted for single edge notch specimens over the temperature range from -100℃ to 20℃. The value of J_<IC> of high density Polyethylene is evaluated based on ASTM standard E813-81 and on E813-87. Although determination of J_<IC> according to both the standards make difference in its value by 30% over the temperature range from -100℃ to -60℃, J_<IC> values become almost constant within 3.5 to 5kJ/m^2. At the temperature above about -20℃, the value of J_<IC> increases significantly with increasing temperature. Using of E813-87 may cause the pronounced overestimation of J_<IC> value at 20℃.