Morphological aspects of the interface in the PEEK‐carbon fiber system

Abstract Although high modulus PAN based carbon fibers (HMS) induce transcrystallinity in PEEK and a wide variety of other semi‐crystalline polymers, the interfacial strength is lower than PEEK in contact with low modulus carbon fibers (AS4) where transcrystallinity is not induced. In the PEEK/HMS system, crystalline lamellae were found to be oriented edge‐on to the fibers, while in AS4 they were oriented flat‐on, reflecting the difference in surface energies between the two fibers. The intrinsic effect of transcrystallinity on the fiber matrix interaction is therefore obscured when the chemistry of the interaction varies.