FRACTURE-TOUGHNESS OF INJECTION-MOLDED GLASS-FIBER-REINFORCED POLYPROPYLENE

The fracture behavior of polypropylene reinforced with 30% by weight of short glass fibers was studied using single and double feed plaque moldings. Plaques were injection molded using several gate types and gate positions. Fracture toughness, K-c, was calculated at different positions in the plaque moldings using single edge notched tension specimens. Fracture toughness was assessed in the directions parallel and perpendicular to the mold fill direction through measurements of the load to produce complete fracture. Results indicated that the value of fracture toughness is affected by the type of gate as well by size of gate. Position of the specimen also affected fracture toughness. Generally, specimens taken from positions near cavity walls gave higher toughness values than those taken from the center of the moldings. Furthermore, fracture toughness in the transverse direction was consistently higher than in the melt flow direction. Finally, in the case of double feed moldings, a much higher fracture toughness was obtained when the initial crack was perpendicular to the weld line than when it was placed inside the weld line.