Health monitoring of composite materials based on BP sensors under complex environments

In this study, the air thermal cycle test and the relative humidity (RH) cycle test were carried out to buckypaper (BP) co-cured with glass fibre prepreg together in order to verify the practicality and stability of the sensor in complex environment. The BP bonded with composite laminate were subjected to tension and tension–tension fatigue up to 1000 cycles when the sensor is subjected to temperature changed from 20 to 120°C and different RH from 0 to 85%, respectively, and the electrical–mechanical response shows that the resistance of sensor increases as the humidity increases, and ultimately the change rate tends to be stable. Tensile experiments shows that gauge factor (GF) changes by 327 and 306%, respectively. The authors finished the fatigue experiment to specimen of the longest environmental treatment in order to further verify the practicality of the sensors, in the fatigue test, the resistance change rate varies with the number of cycles, and it tends to be stable after a period of time. The authors draw the curve of GF and fatigue cycle number so that the stability of the sensors are better reflected, the result is consistent with the fatigue result. Therefore, BP sensors can be applied to the health monitoring of aerospace composites.