DYNAMIC FRACTURE-TOUGHNESS OF POLYPROPYLENE REINFORCED WITH CELLULOSEFIBER

To better understand mechanisms of fracture under impact loading in ce llulose-reinforced polypropylene, dynamic fracture analysis was perfor med based on linear elastic fracture mechanics. Dynamic critical energ y release rates and dynamic critical stress intensity factors were ded uced from instrumented Charpy impact test measurements. Dynamic fractu re toughness increased with cellulose content. However, the assumption of linear elasticity began to break down for cellulose fiber contents exceeding 40% by weight. Scanning electron microscopy showed consider able fiber curl in the composites, especially at low fiber contents; a t high fiber contents, composites developed a three-layer structure.