TEMPERATURE-DEPENDENT FRACTURE MECHANISMS IN GEL-SPUN HOT-DRAWN ULTRA-HIGH-MOLECULAR-WEIGHT POLYETHYLENE FIBERS

Tensile testing of gel-spun hot-drawn ultra-high molecular weight poly ethylene (UHMWPE) fibres reveal a ductile-brittle transition temperatu re. Ductile fracture above the transition temperature is believed to b e initiated by a stress-induced orthorhombic-hexagonal phase transitio n, whereas at lower temperatures brittle fracture occurs in the orthor hombic phase. SEM micrographs of the fracture surfaces of UHMWPE fibre s fractured below the transition temperature show fibrillar fracture a nd cannot be distinguished from fibres fractured in a ductile way abov e the transition temperature.