Sustainable aerospace composites: enhancing mechanical performance of FFF-printed onyx through fibre optimization

Carbon fibre composites, known for their high strength-to-weight ratio, are extensively used in critical aerospace components. However, traditional manufacturing methods are time-intensive, costly, and resource-heavy. Fused Filament Fabrication (FFF), a material extrusion-based additive manufacturing technique, offers a sustainable alternative, enabling complex geometries with minimal waste. Despite its advantages, FFF-printed parts made from standard thermoplastics often lack the mechanical strength needed for high-stress applications. This study investigates the mechanical performance of nylon-short carbon fibre (Onyx) and carbon fibre–reinforced composites with different lay-up orientations. Composites with [0,90]s and [0,45,90,-45]s orientations were compared to non-oriented samples which showcased significant improvements in flexural and comparable tensile strength respectively. Scanning electron microscopy revealed that the fibre alignment delayed crack propagation and enhanced durability, with fibre pull-out as the primary failure mechanism. These findings demonstrate that optimizing fibre orientation during FFF can significantly improve composite performance, offering a sustainable pathway for high-performance applications in aerospace and automotive industries where strength, efficiency, and sustainability are paramount.