Self-sensing and self-healing smart fiber-reinforced thermoplastic composite embedded with CNT film

Impacts can degrade the strength of composite structures; thus, impact damages should be monitored and repaired. In this study, a novel composite consisting of carbon nanotube film and glass fiber-reinforced thermoplastic was thermoformed. The fabricated smart composite demonstrated self-sensing and self-healing capabilities for damage caused by low-energy impacts. Elastic deformation of the composite caused by a 0.5-J impact was monitored from the immediate change in resistance of approximately 0.25 Ω. Internal damage such as tears and debonding was detected in real time by monitoring the permanent resistance variation of approximately 0.4 Ω using a Wheatstone bridge with a 3-J impact on the smart composite. This difference occurs because a 3-J impact discontinues the conductive path of the carbon nanotubes and changes the total resistance of the smart composite. The internal damage caused by a 3-J impact was repaired through the Joule heat effect when 0.7 MPa and 55 V were applied to heat the composite to 330°C. A three-point bending test demonstrated that the self-healing efficiency of the smart composite reached 87% in terms of flexural strength.