Geometry and temperature effects on tensile properties and failure behaviors of open-hole and bolted-joint CF/PEKK composites

Abstract

Temperature-dependent tensile properties of carbon-fiber-reinforced polyetherketoneketone (CF/PEKK) composites with varying width-to-diameter ( W/D ) ratios in open-hole (OH) and bolted joint (BJ) were investigated. CF/PEKK exhibited higher modulus and strength at lower temperature due to restricted polymer chain mobility, and lower values at elevated temperature due to increased polymer ductility. OH net tensile strength decreased with decreasing W/D , with strain retention dropping significantly at W/D ≤ 2. The approximate average strain concentration factor determined from digital image correlation slightly exceeded theoretical values due to semi-crystalline nature of PEKK. Distinct failure behaviors highlighting the complex interplay between temperature, W/D , and failure characteristics. Evaluating W/D and temperature effects on BJ CF/PEKK revealed changing failure modes. Bolted joint efficiency emphasizing the need to optimize W/D ratios above 2 to achieve high efficiency. These findings highlight the geometry and temperature interplay affects CF/PEKK composites, which are crucial for designing high-performance materials, especially for aerospace applications .