Three-dimensional Braided Composite Acoustic Emission Testing Technology

Acoustic emission (AE) is the phenomenon that materials or construction release energy via elastic wave when they suffer the function of outside dint or inside dint producing transforming or rupture. Source location is one of main task of AE inspection. It is used to address the defect of material. We can clear know the location of defect via AE source location technique. Especially for early period destruction, if the location of defects is clear, the dynamic monitor for materials can be carried on.When the defects or potential defects of solid (material or parts) status changes, the instantaneous elastic wave will be released under external condition processing. AE wave of three-dimension braided composite material is multi-frequency and multi-model wave and each mode has many frequencies that propagate with the different velocity in any plate like material. When the same AE wave reaches different sensors, there will be great difference for their velocity because that different wave attenuation degree and different wave change degree causes different modes of received wave by the sensor in the same array. The traditional localization method is not suitable for the complicated signal.By using modal acoustic emission (MAE) theory and the method of wavelet transform, this paper manages to analyze the mechanical features when applies to three-dimension braided composite material under tensile and compressive test process, and research the method how to locate the defects. AE technology is established for internal microstructure changes of three-dimension braided composite material under the outside forces, which can provide the theoretical basis of the mechanical feature. Through the analysis, this paper concludes that the number of AE events has good relationship with the damage evolution of C-fiber composite material, and braided angle and mechanical feature of three-dimension braided composite material are closely related. It is valuable for the application of three-dimension braided composite material. In order to locate the AE source, this paper picks up the AE signal in the same mode and eliminates the interference between different frequencies, which makes use of MRA and signal decomposition and reconstruction in wavelet transform. Compared with the traditional localization method, this method is independent of threshold. The precision is enhanced.