Multifunctional fibre reinforced polymer (FRP) composites combine multiple properties that can include mass efficiency, damage resistance, damage tolerance, self-repair, in-service health monitoring and ease of inspection. This paper describes a new type of multifunctional FRP composite material that enables large improvements to the interlaminar fracture toughness and damage tolerance whilst also allowing rapid self-sensing and material-enabled thermography capabilities. The composite material is reinforced in the through-thickness direction using shape memory alloy (SMA) wires inserted by tufting.

Tufting is a cost-effective manufacturing process that uses commercially available automated systems to insert yarns in the through-the-thickness direction of dry fabric preforms [1]. Tufting uses a single needle to penetrate the fabric stack, and requires access only from a single side of the preform. As shown in Fig. 1, thin and flexible SMA filaments made of nitrol (Ni-Ti alloy) were tufted into six layers of 0˚/90˚ non-crimp carbon fabric using a KSL RS 522 tufting machine mounted on a KUKA KR240–2 robotic arm. The tufted fabric was infused with epoxy resin using the resin transfer moulding (RTM) process. The final cured composite panel was cut into double cantilever beam (DCB) coupons to perform mode I interlaminar fracture toughness tests according to the ASTM D5528-01 specification.