APPLICATION OF THE J-INTEGRAL CONCEPT FOR THE DESCRIPTION OF TOUGHNESS PROPERTIES OF FIBER REINFORCED POLYETHYLENE COMPOSITES

For the determination of toughness properties of HDPE/glass fiber and HDPE/cotton fiber composites, an instrumented Charpy impact test has been used. The interpretation of impact load-deflection curves has been carried out with several concepts of fracture mechanics. Here the limits of linear elastic fracture mechanic (LEFM) have been shown. The change of toughness properties with increasing fiber volume can be described for short fiber reinforced composites with the help of the J-integral concept in a suitable mode. An application of the conventional Charpy impact test will result in an overestimation of material behavior because of the energy of crack propagation. With the help of a micromechanical model to describe failure processes, taking account of energy dissipative processes, it is possible to calculate fracture mechanical material parameters. Because of the peculiarities of deformation and fracture behavior, the application of elastic-plastic fracture mechanic (EPFM)-concepts for fiber reinforced polymers is required.