Antioxidant-enhanced interfacial adhesion and mechanical properties of polyetheretherketone–carbon fiber composites

The effects of antioxidants on the interfacial adhesion between polyetheretherketone (PEEK) and carbon fiber (CF) and the mechanical properties of PEEK/CF were investigated. The interfacial shear strength of PEEK/CF was improved 30–50 % by adding phosphorus and phenolic antioxidants to PEEK. Its elastic modulus was increased by 40 %, and cohesive failure occurred with the addition of the antioxidants. Electron spin resonance spectroscopy and rheological property analysis of the molten state assumed that the antioxidants helped enhance the interfacial interaction owing to an increase in phenoxy radicals and the generation of phenyl radicals. Micro-Raman spectroscopy indicated that the improved interfacial interactions suppressed the formation of PEEK crystals at the interphase, resulting in cohesive failure. The addition of antioxidants not only improved the interfacial adhesion of PEEK/CF but also suppressed the interfacial fracture of PEEK/CF. • Antioxidants contribute to interfacial interactions at PEEK/CF. • Antioxidants suppress interfacial fracture in PEEK/CF. • Consideration of interfacial interactions using electron spin resonance. • Crystal analysis at interphase using micro-Raman spectroscopy.