Shin Chow-Shing, Chen Liang-Wei
Department of Mechanical Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan.
Polymers (Basel). 2023 Mar 22;15(6):1575. doi: 10.3390/polym15061575.
Adhesive joints possess a number of advantages over traditional joining methods and are widely used in composite structures. Conventional non-destructive examination techniques do not readily reveal joint degradation before the formation of explicit defects. Embedded fiber Bragg grating (FBG) sensors and the resistance of carbon nanotube (CNT)-doped conductive joints have been proposed to monitor the structural integrity of adhesive joints. Both techniques will be employed and compared in the current work to monitor damage development in adhesive joints under tensile and cyclic fatigue loading. Most of the previous works took measurements under an applied load, which by itself will affect the monitoring signals without the presence of any damage. Moreover, most FBG works primarily relied on the peak shifting phenomenon for sensing. Degradation of adhesive and inter-facial defects will lead to non-uniform strain that may chirp the FBG spectrum, causing complications in the peak shifting measurement. In view of the above shortfalls, measurements are made at some low and fixed loads to preclude any unwanted effect due to the applied load. The whole FBG spectrum, instead of a single peak, will be used, and a quantitative parameter to describe spectrum changes is proposed for monitoring purposes. The extent of damage is revealed by a fluorescent penetrant and correlated with the monitoring signals. With these refined techniques, we hope to shed some light on the relative merits and limitations of the two techniques.
与传统连接方法相比，胶接接头具有许多优点，并且在复合结构中得到广泛应用。传统的无损检测技术在明显缺陷形成之前不易揭示接头的退化情况。已经提出了嵌入式光纤布拉格光栅（FBG）传感器和碳纳米管（CNT）掺杂导电接头的电阻来监测胶接接头的结构完整性。在当前工作中，将采用这两种技术并进行比较，以监测拉伸和循环疲劳载荷下胶接接头的损伤发展情况。以前的大多数工作都是在施加载荷下进行测量的，而施加的载荷本身会在没有任何损伤的情况下影响监测信号。此外，大多数FBG工作主要依靠峰值移动现象进行传感。胶粘剂的降解和界面缺陷会导致应变不均匀，这可能会使FBG光谱产生啁啾，从而在峰值移动测量中引起复杂性。鉴于上述不足，在一些低且固定的载荷下进行测量，以排除由于施加的载荷产生的任何有害影响。将使用整个FBG光谱，而不是单个峰值，并提出一个用于描述光谱变化的定量参数用于监测目的。通过荧光渗透剂揭示损伤程度，并将其与监测信号相关联。通过这些改进的技术，我们希望能够阐明这两种技术的相对优点和局限性。
