Fibre reinforced polymer (FRP) composites have been prone to damages such as delamination, debonding, matrix cracking and fibre breakage. In this paper, detailed study has been carried out on determining the presence of small delamination in sub layers of carbon fibre composite beam using various non-destructive tests (NDT) and vibration signal analysis. We have concluded that ultrasonic and X-Ray Diffraction (XRD) tests have found to be more effective in detecting small delamination than X-Ray radiography and thermography tests. In the vibration test, we have observed that the natural frequency decreases and the rate of damping increases in delaminated carbon fibre composite beam as compared to composite beam without delamination. Besides, the fast fourier transform (FFT) results of vibration signal of delaminated beam have clearly shown higher harmonics and side bands. Finally, we have concluded that online vibration test can also be used effectively to detect presence of small delamination in FRP composites.

中文翻译：

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碳纤维增强聚合物复合材料梁无损检测的小分层检测及振动分析

纤维增强聚合物（FRP）复合材料易于损坏，例如分层，脱胶，基体开裂和纤维断裂。在本文中，已经进行了详细的研究，以使用各种无损检测（NDT）和振动信号分析来确定碳纤维复合材料梁子层中是否存在小分层。我们已经得出结论，发现超声波和X射线衍射（XRD）测试比X射线射线照相和热成像测试在检测小分层方面更有效。在振动测试中，我们观察到与没有分层的复合梁相比，分层的碳纤维复合梁的固有频率降低，阻尼速率增加。除了，分层梁振动信号的快速傅立叶变换（FFT）结果清楚地显示出更高的谐波和边带。最后，我们得出的结论是，在线振动测试也可以有效地用于检测FRP复合材料中是否存在小分层。