EXPERIMENTAL STUDY OF CRACK GROWTH IN HDPE PE100 PIPES

The operation conditions of a piping system such as impact loads, cyclic loadings and discontinuities cause damages, cracking or weakening in the material. The High Density Polyethylene (HDPE) is amply used in the fabrication of pipes due to its versatility, low cost and lightweight. In this study, an experimental study of fracture mechanics of HDPE PE100 specimens obtained directly from extruded pipes is developed. The research is aimed at characterizing the pipe mechanical behaviour under operation loadings, for which elastic-plastic mechanical tests under the ASTM D-5045, E-1820, E-399 and E-813 standards and ESIS protocol are carried out. The influence of the orientation induced by the extrusion process (circumferential or longitudinal direction) on pipes fracture resistance is established. SENB type specimens (three point bending) are used for the fracture characterization and J-R Curves (J vs. Delta a) for elastic-plastic analysis are generated according to ESIS protocol. The PE100 fracture characterization throughout the J vs. Delta a curves indicates that in both circumferential and longitudinal directions require similar quantities of energy to generate new fracture surfaces on HDPE pipes. Indeed, the orientation of the polymer chains as a result of pipe extrusion process could be not so relevant for predicting the direction of crack growth in HDPE pipes