Maximising strength retention for carbon fibre prepreg scraps: A patch-based laminate approach

Abstract

The growing use of carbon fibre prepreg in high-performance composite applications has led to a rapid increase in material waste from ply cutting. Components manufactured from the discarded, uncured discontinuous fibre material typically exhibit lower strength than continuous fibre counterparts, particularly when small patches are used and intra-ply joints are required to cover the surface of the final component. This study investigates strategies to enhance the performance of parts made using discontinuous woven prepreg patches, for structural applications. By exploring different patching patterns and incorporating interlaminar toughening mechanisms, high-performance laminates can be developed from otherwise wasted material. The optimum patch configuration, featuring a 100 mm patch size and a 30 mm stagger offset (Si100St30), retains 66% of the tensile strength of a continuous fibre benchmark. Introducing interleaved non-woven thermoplastic veils between the patch-based plies reduced the effect of the stress concentration at the patch ends for this design, increasing tensile strength retention to 73%. This performance is comparable to that achieved with continuous outer plies in continuous/discontinuous fibre hybrid laminates. While additional mechanical testing is needed to validate this approach for load-bearing applications, the study highlights the significant potential of patch-based laminates and identifies effective methods to maximise tensile strength retention, extending the viable use of waste prepreg materials.