THE FRACTURE-BEHAVIOR OF SHORT GLASS-FIBER-REINFORCED POLYOXYMETHYLENE

This paper describes an examination of the fracture behaviour of hydrostatically extruded polyoxymethylene. Unfilled and glass-filled extrudates were tested, both with a nominal draw ratio of 8, the highest obtainable for this material using the extrusion process. The compact tension geometry was used for the fracture tests. Samples were loaded perpendicular and parallel to the extrusion direction and tests were carried out at +20 and -50 degrees C. The glass-filled extrudate showed a significant improvement in fracture behaviour compared with the unfilled extrudate, with an increase in the fracture toughness and stable rather than unstable crack propagation. Most interestingly, the crack propagation was still stable at -50 degrees C.