Effects of Gaseous Environments on the Mechanical Failure of Polyethylene Pipe Materials

摘要

This final report briefly reviews the important results of the two previous annual reports and presents in detail the work of the third and final year involving the micromechanisms of deformation and fracture. It was found that the formation of crack-pores at the root of a notch is the initiation stage for fracture. The various stages of fracture were found to consist of (1) pore formation (2) fibrillation and (3) fibril fracture. The details of fibril fracture were observed. The reason for characterizing these micromechanisms is to formulate a basis for comparing short time tests with the micromechanisms that occur in failures after long times. The results of the first two years showed that gases such as CH3, CO2, N2 O2 and liquids such as water and isopentane have a minor effect on the fracture behavior of polyethylenes at room temperature.