Multi-material 3D printing of continuous carbon fibre reinforced thermoset composites with tailored fibre paths and bespoke conforming thermoplastic moulds

This paper proposes a novel additive manufacturing approach for rapid, integrated fabrication of complex structures made from 3D-printed composites with low porosity and a high continuous fibre content. Continuous carbon fibre reinforced epoxy composites with >50% fibre volume fraction were printed in parallel with short carbon fibre reinforced polyamide-6 (PA6) conforming moulds which have a melt temperature higher than the curing temperature of epoxy. The research further optimised the continuous fibre paths through experiments and as-manufactured finite element simulations, using 3D-printed truss structures under three-points bending as a case study. Additionally, the incorporation of polylactic acid (PLA) with a lower melting temperature, enhanced compatibility and bonding between the epoxy and PA6. The approach was applied and demonstrated for a lightweight composite wing box using tailored material interface and customised reinforcement alongside varying infill densities. This approach also opens up possibilities for assembling lightweight, large-scale composite structures using 3D-printed high-performance continuous carbon fibre units. • Novel AM method achieves >50% fibre volume fraction in 3D-printed composites. • Multi-material printing integrates thermoset composites and thermoplastic moulds. • PLA enhances interfacial bonding with epoxy through co-melting and curing. • Optimised fibre paths and infill densities enable lightweight, high-strength structures. • Demonstrated scalable fabrication of composite aerofoil with tailored reinforcements.