Flexural monitoring of carbon fiber/epoxy composite by acoustic emission

Carbon / epoxy composite is one of the most useful polymer matrix composites that has special properties such as high strength-to-weight ratio, high hardness, high corrosion resistance, Resistance to nuclear radiation has high consumption in different industries such as aerospace industry. Therefor monitoring of loading of this type of composite is important. In order to determine failure mechanisms, acoustic emission method has more performance than other non-destructive methods. In this research acoustic emission method was used to evaluate and monitoring of the carbon epoxy composite three point bending load. For this purpose bending behavior of composite and relationship between acoustic signals studied. Using both fast Fourier transform and wavelet transform method in this research, which led to the same result. Using FFT maximum frequency 140 KHZ was determined, that wavelet transform confirmed this result too. Time limits that events was occurred on the under load specimen, was monitored by online diagrams that obtained from acoustic system. Finally failure mechanisms of composite were confirmed by SEM pictures. Time limits and ascending progress of diagrams validates bending diagram.