基于相移光纤光栅传感器的碳纤维增强树脂复合材料基体裂纹超声探伤

复合材料内部的微小裂纹常会引起后续严重的破坏，因此需要对其进行检测。然而超声探伤复合材料基体裂纹非常困难。本文搭建了一个具有高灵敏度、大带宽的相移光纤光栅超声传感系统，利用此系统探测了在正交铺层碳纤维增强树脂复合材料板中传播的Lamb波。对Lamb波进行数据处理发现，随着三点弯曲实验产生的基体裂纹个数增加，Lamb波的幅值和频谱峰值线性减少。通过和传统压电传感器比较表明，相移光纤光栅传感器测得的Lamb波信号随复合材料基体裂纹数的增加其幅值具有更高的下降速率，表明相移光纤光栅传感器更适合于复合材料基体裂纹的超声探伤。研究表明，新开发的传感系统能够探测到中心频率为300 kHz的微弱超声信号，并能够对碳纤维增强树脂复合材料板中微小基体裂纹个数进行精确评估。 

Ultrasonic damage detection of matrix cracks in carbon fiber reinforced polymer composites using phase-shifted fiber Bragg grating sensor

Micro damage in composites usually leads to catastrophic failures in the following applications and therefore needs to be detected.However,it is difficult to detect transverse cracks in composite laminates by using ultrasonic nondestructive testing.In this research,a highly-sensitive and broad bandwidth phase-shifted fiber Bragg grating ultrasonic sensing system was developed and applied to detect Lamb wave propagating in a cross-ply carbon fiber reinforced polymer composites.After conducting data process on the detected Lamb wave,it is found that along the increase of crack numbers induced by the standard three-point bending test,the amplitude of the waveform and the peak value of the spectrum both linearly decrease.After compared with conventional lead-zirconate-titanate sensor,all research results demonstrate that the Lamb wave detected by phase-shifted fiber Bragg grating sensor shows a higher declining rate when the number of matrix cracks increase.Thus,the novel optical-fiber-based sensor succeeds in detection of weak ultrasonic signals with middle frequency of 300 kHz,and can precisely evaluate the micro transverse cracks in composite laminate.