Co-authors​ :

 Murat ÇELIK (UNITED KINGDOM), Arun Kumar ALAPATI (UNITED KINGDOM), James R DAVIDSON (UNITED KINGDOM), Hanisa HASRIN (UNITED KINGDOM), David MAY (GERMANY), Colin ROBERT (UNITED KINGDOM), Conchúr M Ó BRÁDAIGH (UNITED KINGDOM) 

Hybrid composites, which combine different fibre reinforcement types in a single matrix, aim at enhancing and tailoring mechanical properties for specific applications. Based on the combination of fibres, it is possible to reduce production costs while simultaneously preserving or improving the mechanical performance. The hybridisation process offers versatility with numerous possibilities for combinations, including the integration of synthetic and natural fibres, or the blending of various types within each category. This flexibility allows for customised solutions, considering factors such as strength, weight, and cost-effectiveness. The use of powder epoxy can be attractive for hybrid composites, due to its exceptional characteristics. At room temperature, powder epoxy is solid, and it undergoes melting at around 45°C. The heat-activated curing agents in its formulation prevent curing until the temperature surpasses 140°C. This allows powder epoxy-based composites to be reshapable, provided the curing temperature limit is not surpassed. Exploiting this unique characteristic, powder epoxy-based towpregs have been successfully developed for use in automated composite manufacturing techniques. These towpregs do not need refrigerated conditions, resulting in a significant reduction in transportation and storage costs. Moreover, powder epoxy exhibits low viscosity, minimal curing exotherms and does not release any volatile organic compounds (VOC), further enhancing its processability. Automated fibre placement (AFP) processing can be employed to produce reshapable, hybrid composite preforms from powder epoxy-based towpregs. In this study, a concept for the production of hybrid composites through the use of powder epoxy-based towpregs is proposed. Towpregs made from powder epoxy are laid on glass fibre fabrics using an AFP head, without curing the towpregs completely. The preform is then cured through a hot press to produce carbon fibre/glass fibre hybrid composites. The interface quality between the carbon and glass fibres is evaluated through interlaminar shear testing. Furthermore, imaging techniques such as scanning electron microscopy (SEM) and optical microscopy are utilised to assess the internal structure of the final part and identify fracture morphologies of tested specimens. The primary objective of the study is to assess the potential of utilising powder epoxy-based towpregs in AFP applications for the production of composite parts that are specifically customised to particular applications. This approach, for instance, enables local strengthening of composite parts based on anticipated stress/load in a cost effective way.