| Carbon fiber composite is an important component for ensuring structural integrity of airplane and airworthiness safety.In the process of usage and maintenance,it is often subject to impact of external forces,which can decrease its structural performance,and even makes it destroyed.Consequently,damage detection is a crucial means to ensure structural security of composite.Based on the damage characteristics and acoustic emission signal characteristics of carbon fiber composite,a set of acoustic emission detection system consist of TMS320F28335 chip is designed to collect,manage,store and display acoustic emission signal.In the treatment of signal,relevant signal characteristic parameter pick-up algorithm is adopted to obtain ringing count,peak value,rise-time,energy and other parameters to evaluate the acoustic emission source.In the system,in order to analyze the acoustic emission signal in time domain and frequency domain,radix 2 decimation in time fast Fourier transform is adopted to transform the collected signal to frequency domain,which result in an easy analysis of acoustic emission signal.Digital oscilloscope is used to confirm the validity of sampling,parameters extraction,data storage and display function,as well MATLAB is utilized to confirm the validity of frequency domain transformation function,and the results confirmed that the theory of system development,DSP algorithm and program are all right.Electronic universal testing machine is used to finish tensile failure test of carbon fiber composite,acoustic emission signal produced in the test is collected.Based on the damage characteristics of carbon fiber composite,the time domain waveform and frequency domain characteristics of collected signal are analyzed.Consequently,three key frequency bands of acoustic emission signal in carbon fiber composite and its corresponding basic damage models are confirmed,and the rule of signal in wavelet analysis is found. |
