The Acoustic Emission Technique In The Performance Testing Of Three-dimensional Braided Composites

The acoustic emission technology (AE) was used to investigate the damage mechanism of C fiber 3-D braiding composite material under tensile test. AE characteristic parameters and waveforms were collected over the entire stress/strain curve. AE characteristic of C fiber 3-D braiding composite material damage evolution was analyzed using multi-parameters analytical method. Features of C fiber 3-D braiding composite material damage evolution were also found. Spectrum analysis was performed to determine the micro-mechanism of damage evolution of C fiber 3-D braiding composite material.The special structure of C fiber 3-D braiding composite material result in its own AE characters. AE accumulative relative energy is related to the damage evolution of C fiber 3-D braiding composite material closely. Damage process includes two main stages: Damage initiate period and badly damage period. The spectrum analysis of C fiber 3-D braiding composite material shows that the main cause for ultimately damage is break of the fiber, the frequency is in 0.45 HZ probably. And through all the damage process, many damage modes co-exit, never in a pure mode. The noise was eliminated by wavelet analysis better and composite material inner damage characteristic was described by frequency spectrum. It would lay foundation for analyzing the mechanical properties of composite material and improving compound process.