Interlamellar Fracture and Craze Growth in PEEK Composites under Cyclic Loading

Abstract

In this paper microscopic details of the crack tip in a unidirectional car bon/PEEK composite material subjected to interlaminar fatigue loading at room tempera ture and elevated temperature are discussed. The photomicrographs show a distinct difference in failure modes at room and elevated temperatures. At room temperature, the failure occurs due to separation between crystalline lamellae in the matrix. In contrast, at elevated temperature, failure is due to breakup of crystalline lamellae which allows forma tion of crazes at the crack tip. For a slowly cooled specimen tested at elevated temperature, a mixture of these failure modes is evident. This understanding is essential to ap propriately model delamination growth in advanced semicrystalline thermoplastic com posites.