Research on Acoustic Emission Signal of Three Dimensional Braided Composite Material
Authors: Li Yi , Wan Zhen Kai , Li Jia Lu 
Published: February 2011

This paper discusses the application and experimental method of acoustic emission for the three-dimensional (3D) braided composite material under flexural testing. It describes the feature of acoustic emission when applied to three-dimensional braided composite material under flexural testing. In order to know the materials damage position precisely, it is very important to collect the signal of acoustic emission source. The results of flexural experiment show that it is precise on the research of acoustic emission source location by the method of wave form analysis .During the collecting signal of acoustic emission , it is compared between parameter analysis and wave form analysis. According to the attenution degree of signal, it is selected signal of acoustic emission source exactly. It is the method to extract the precise acoustic emission signal by the different algorithm of wavelet analysis. We know that humans have been using materials by testing activities support, these tests have developed several centuries. From the traditional rough test to support materials and materials used in all aspects of science and technology, modern, scientific program, at present, there are mutual dependencies between the progress of scientific knowledge and the development of test methods. The 3D braided composite material is a kind of complex structure. Because of the many components and weaving material preparation process characteristic, material mechanics behavior is very complicated. It is characteristics of the 3D braided composite material, that the application on composites is widely more and more. The 3d braided composites have been used widely in aerospace, aviation, transportation, chemical, sports, medical care and other fields, so it is extremely vital significance for research on mechanics performance analysis of 3D braided composite material. Current studies of damage fracture behavior of composite materials are used in homogeneous materials research methods, namely the mechanical test and microscopic observation, but the research cannot distinguish and identify different damage fracture source, due to the combination of mechanical test parameters of the complex fracture micro-mechanism not sensitive. Microscopic observation is in fact observation later, local fracture surface morphology research, so can not observe the interaction of numerous fracture source and micro behavior, and can not study in the character of fracture source of composite materials, therefore the source faults already can not adapt to the traditional methods of composite material damage fracture process. From external or internal force effect material and structure produced deformation or fracture with elastic wave form, the strain energy release phenomenon called acoustic emission or stress wave [1]. Acoustic emission testing method is a kind of material internal defects or potential defects in the dynamic changes in movement, the damage detection method is real-time monitoring and can reflect the characteristics of acoustic emission sources in the load of the dynamic response. The AE information can directly reflect defects and changes [2, 3].