A STUDY OF THE EFFECT OF FORMING TEMPERATURE ON THE MECHANICAL-BEHAVIOR OF CARBON-FIBER PEEK COMPOSITES

In this paper, a study of the effect of forming temperature over the range 360-440-degrees-C on the mechanical behaviour of carbon-fibre/PEEK composites is presented. The properties examined include mode I and II delamination resistance of unidirectional specimens and the tensile strength of (+/-45-degrees) and (90-degrees) specimens. A previous report suggested that G(IC,Init) can be doubled by forming specimens at a temperature 20K higher than the recommended forming temperature (380-degrees-C). Results in this paper show that other mechanical properties are also improved if higher forming temperatures are used, but the increase is most dramatic in mode I delamination behaviour. To explain this phenomenon, a microscopic analysis of fractured specimens and an evaluation of the preparation technique of delamination test specimens were carried out. Results of these analyses suggest that the improvement in mechanical properties with forming temperature is due to an increase in interfacial strength between fibre and matrix.