Damage Detection of Cross-Plied CFRP Laminates Based on Rectangular Differential Pulse Eddy Current Sensors

ABSTRACT Carbon fiber reinforced polymer (CFRP) laminates are extensively used in aviation due to their excellent material properties. Damages resulted from manufacturing or usage seriously undermine the safety of aircraft structures. Therefore, the efficient detection of the damage in CFRP laminates is important. In this paper, three kinds of common damages including impact damage, crack damage and delamination damage are detected based on pulsed eddy current (PEC) with rectangular differential sensors. Firstly, to overcome shortcomings of traditional PEC sensors, an optimized rectangular differential sensor is proposed in the study. Then, a normalization method is introduced to process the differential signal obtained with the sensor. Finally, the relationship between the size of the damage and the normalized differential signal is investigated. The investigation results show that the rectangular differential sensor can detect the three types of damages. When a new damage object is detected, the measurement step of a reference signal is omitted. The peak value of the normalized differential signal increases with the increase in damage size. The new PEC method has been proved in the study.