Acoustic Emission Signals Of Damage And Fracture In Fiber Reinforced Composites And Clustering Analysis

With the extensive application of fiber reinforced polymer,the nondestructive testing technique has drawn much attention.Due to the advantages of activeness,insensitivity to geometry of samples,immediacy and characteristic,the application of acoustic emission technology on composite has become a hot research topic.Clustering analysis,which can be adopted by signal processing,has significant separation effect on random,irregular and mixed data and has been widely used in various fields.In this paper,damage and failure mechanism of typical laminated Carbon Fiber Reinforced Polymer(CFRP)are investigated by feature parameter decision method,clustering analysis and experiments.The main research contents include:(1)Peak frequency distribution of acoustic emission signals corresponding to five typical failure modes of CFRP laminates with prefabricated damage were obtained by tensile test.Acoustic emission signals of resin matrix crack,resin matrix fracture,fiber broken,fiber-matrix debonding and delamination were successfully separated and identified.Overlap of peak frequency range between the fiber-matrix debonding and delamination can be observed.(2)The k-means clustering analysis algorithm and the fuzzy C-means clustering analysis algorithm were adopted to separate the mixed fiber-matrix debonding signal and delamination signals.The result show that,energy of fiber-matrix debonding signal is lower(10~2aJ level),while the energy of delamination signal is at 10~5aJ level.The difference between two clustering analysis results is about 9.27%.The results obtained by employing the two clustering analysis were evaluated by the Silhoutte coefficient.The results show that FCM algorithm has better accuracy comparing with the k-means.(3)Based on the characteristic parameter of acoustic emission signal corresponding to different fracture mode and the results of clustering analysis,damage and failure mechanism of typical CFRP laminates during the tensile test were identified.The signal analysis results show that,compared to 0~o unidirectional laminates,quasi-isotropic laminates have more obvious interlaminar slide under tension.