In-situ monitoring of glass fiber/epoxy composites by the embedded multi-walled carbon nanotube coated glass fiber sensor: From fabrication to application

Monitoring the curing defects as well as damages that occur in the fabrication and application process is important for ensuring the safety of composite structures. In this paper, a highly sensitive 1-D line sensor is designed to achieve self-sensing and diagnosing functionalities in both the fabrication and application of glass fiber reinforced epoxy (GF/epoxy) composites. The sensor consists of multi-walled carbon nanotube coated glass fiber (MWCNT@GF), which is sensing the damage by the principle of resistance change. Due to the vacuum-assisted resin infusion process, the MWCNT@GF sensor is embedded into GF/epoxy composite laminates, and hence, it can monitor the resin frontal flow, curing, and especially the flow defects. In the subsequent application, the tensile performance of a GF/epoxy composite joint is evaluated by not only the force-displacement curve but also the displacement-dependent resistance change of the sensor. Tensile damage modes are distinguished, which is for the first time to be reported. The MWCNT@GF sensor is mechanically stable and highly sensitive; hence, it can be used to follow the composite performance from fabrication until the end of life.