Mechanical and self-monitoring properties of coextrusion 3D printed continuous carbon fibre reinforced polymer composites

Continuous carbon fibre composites are distinguished by their lightweight design and high strength-to-weight ratio. The development of additive manufacturing technology has expanded the possibilities for continuous carbon fibre-reinforced polymer composites (CCFRPCs). However, damage within this structure, such as matrix cracking, fibre fracture, delamination, etc., is inevitable in practical applications and may lead to catastrophic events. Therefore, structural health monitoring of CCFRPCs is important for comprehending their usefulness and performance. External sensors are susceptible to environmental and practical constraints during the service period, whereas embedding the sensors into the polymer matrix requires additional methods and other conductive materials, which is a complex process and costly to produce. Therefore, the piezoresistive features of continuous carbon fibre composites are exploited in this study to investigate the integrated stress-strain damage sensing capability due to carbon fibre networks in the 3D printed CCFRPCs. Continuous CFRPCs with different fibre resistance networks are produced by co-extrusion 3D printing technique to demonstrate the strain sensing functionality by incorporating a resistance measuring circuit. The resistance change of 3D printed structures is significantly correlated with the loading and deformation of CCFRPCs. The resistance change in the structure can be used to determine the status of the composite part. Lastly, the potential of 3D-printed, integrated self-monitoring CCFRPC specimens is assessed through a finger joint motion case study. The study demonstrates that the change in resistance in the structural components can be used to monitor the loading and strain damage of the 3D-printed continuous carbon fibre composite, expanding the range of applications for 3D-printed CCFRPCs.