Water Absorption and Fiber-Matrix Interface Durability in Carbon-PEEK

Abstract

Moldings have been prepared from carbon-PEEK prepreg (APC2) in which the fibers were unidirectional. Their transverse mechanical properties were compared with those of moldings made from unreinforced PEEK. In addition, the water absorption at 23°C, 60°C, and 90°C of the polymer and composite were measured, together with the mechanical properties after various durations of immersion in 90°C water. The results showed that the interface was not affected by the immersion, at least up to 8000 h. There was a slight loss of polymer strength (20%) and failure strain (25%), which was reflected in the composite properties. Water absorption was determined almost entirely by the amount of polymer present in the composite. However, there was a small additional absorption, probably due to the relief of residual stresses. The results with respect to the interface were far more clear cut than those obtained from single fiber tests, supporting the contention that single fiber tests should be phased out as soon as possible.