A Study on Frequency Analysis of Acoustic Emission in Composite Materials

对复合材料的微观断裂机制进行分类，如基体微裂纹、纤维断裂、分层和基体开裂等，在实际应用中具有重要意义。利用与声发射波参数最吻合的频谱分析了CFRP的微断裂机理，并利用模型CFRP研究了常规CFRP的微断裂机理。模型CFRP中基体微裂纹、基体开裂、基体与纤维脱粘、基体与纤维摩擦或纤维断裂的频谱分别为260、50-100、150-250和270-390 KHz。常规CFRP层合板和单向CFRP层合板中基体开裂、脱粘、基体与纤维间摩擦或纤维断裂的频谱分别为50-100、150-250和270-390 KHz。常规和三向CFRP层合板的频谱中含有630 KHz的频率，而模型CFRP层合板中不含有630 KHz的频率，该频率是由分层处纤维之间的摩擦产生的。其次，在A类SMC复合材料中，基体开裂、碳酸钙开裂或基体与碳酸钙之间的脱粘频率，复合材料在80-180、240-450、180-250和250-400 KHz的频率范围内发生了纤维与基体的脱粘或纤维拔出和纤维断裂。

It is important to classfy the microfracture mechanisms of composite materials such as the micro-cracking in matrix, the fiber breaking, the delamination and the matrix cracking in pratical use. The microfracture mechanisms are studied by the frequency spectrum, which is most fitted in the AE wave parameters.The microfracture mechanisms of convential CFRP is studied by using model CFRP. The frequency spectra of the micro-cracking in matrix, the matrix cracking, the debonding between matrix and fibers, and the friction between matrix and fiber or the fiber breaking in model CFRP are 260, 50-100, 150-250 and 270-390 KHz, respectively. The frequency spectra of the matrix cracking, the debonding, and the friction between matrix and fibers or the fiber breaking in the conventional and unidirectional CFRP laminates are 50-100, 150-250, and 270-390 KHz, respectively. The frequency spectrum of conventional and three directional CFRP laminates contains the frequency of 630 KHz, which the model CFRP does not contain and it is generated by the friction between fibers at the delamination.Next, in the class A-SMC composite material, the frequencies of matrix cracking, the calcium carbonate cracking or the debonding between matrix and calcium carbonate, the debonding between matrix and fibers or the fiber pulling out, and the fiber breaking are 80-180, 240-450, 180-250 and 250-400 KHz, respectively.It is found that the fracture mechanisms of composite materials can be clarified by the frequency analysis.