Comparison of Flexural Loading Frequency Analysis Methods of Carbon Fiber / Epoxy Composite by Acoustic

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 and etc. has high consumption in different industries such as aerospace industry. Therefor loading monitoring of this type of composite is important. In order to determine various failure mechanisms, acoustic emission method has more performance than other non-destructive methods. In this research acoustic emission method was used to study carbon/epoxy composite and evaluate frequency range of flexural loading. For this purpose bending behavior of composite and relation between acoustic signals had studied. Using both fast Fourier transform and wavelet transform analysis methods in this research, led to the same result with margin of 5%. By using FFT analysis, maximum frequency of 135 KHZ was determined while using wavelet transform, this amount led to 142 KHz. Time limits that events was occurred on the specimen, monitored by online diagrams that obtained from acoustical system. Energy distribution at failure mechanisms was obtained as 17%, 29% and 48% related to matrix fracture, debonding and fiber breakage respectively. Finally failure mechanisms of composite were confirmed by SEM images. Energy distribution amounts, time limits and ascending progress of diagrams validate bending diagram.