Influence of strand size and morphology on the mechanical performance of recycled CF/PEKK composites: Harnessing waste for aerospace secondary load-bearing applications

Abstract

The flexibility and precision of automated fiber placement (AFP) have made it a standard methodology in the aviation industry. However, the use of continuous slit tapes along component lengths generates significant waste. This waste presents an opportunity for recycling into secondary load-bearing structures, particularly in applications where components are not subjected to extreme working conditions. In this study, carbon fiber-reinforced polyetherketoneketone (CF/PEKK) strands are recycled into randomly oriented strand (ROS) panels using a cost-effective, vacuum-assisted hot press process while maintaining aerospace-quality standards. Both long and short strand lengths, as well as shredded strands mimicking real-life industrial waste, are analyzed for their mechanical performance and geometric stability. Mechanical properties of the recycled CF/PEKK composites are evaluated through tensile, shear, compression, Izod impact, and dynamic mechanical analysis (DMA), using digital image correlation (DIC) for precise measurements. Additionally, topological 3D scanning is used to assess the geometric stability of the panels. Results indicate that short strands offer superior mechanical properties, while shredded strands perform comparably. This study makes a unique contribution by demonstrating the effective recycling of slit tape waste into high-performance composite materials, advancing sustainable practices in aerospace applications.