Thermally conditioned aerospace‐grade carbon fiber reinforced polyether ketone ketone composites: Structure, impact response, and thermomechanical performance
Emi̇ne Feyza Şükür
Abstract
Abstract Carbon fiber‐reinforced high‐performance thermoplastic composites have recently become an efficient alternative for aerospace engineering applications. However, the temperature sensitivity of semi‐crystalline carbon fiber/polyether‐ketone‐ketone (CF/PEKK) polymers revealed the necessity of investigating their performance in service conditions. This study aims to evaluate the effect of extreme service conditions on thermomechanical performance and fracture characteristics of CF/PEKK composite laminates. For this, aerospace‐grade composite laminates were manufactured with the automated fiber placement process and were exposed to extreme service temperatures of −50°C (Conditioned I), 180°C (Conditioned II), and initially 180°C following −50°C (Conditioned III), simulating critical service temperature ranges in aerospace applications. According to impact tests, the energy absorbance of CF/PEKK composites decreased in all thermal conditioning scenarios by up to 25%. Additionally, Conditioned I samples represented relatively low glass transition temperature and degree of crystallinity compared to the control samples; however, Conditioned II and Conditioned III samples exhibited an opposite behavior. Dynamic mechanical analysis (DMA) investigations revealed a 13% reduction in the storage modulus for all thermal conditionings. While CF/PEKK composites represented ductile/brittle behavior at room temperature and high/low conditioning temperatures, their brittleness increased at −50°C, and the structure became ductile at 180°C. This study confirms that DMA is a powerful tool for determining the glass transition temperature for fiber‐reinforced composites with higher sensitivity and accuracy than DSC.