Research On Delamination Damage Monitoring Of CFRP Drilling Based On Acoustic Emission And Axial Force Signals

Carbon fiber reinforced resin matrix composites(CFRP)have the advantages of high specific modulus,high specific strength and low density,which are far superior to traditional metal materials.However,due to the anisotropy of CFRP mechanical properties,poor thermal conductivity and low interface bonding strength.In the process of drilling,the workpiece is prone to interface delamination,burr,tear and hole wall scratch,among which the interface delamination damage has the most serious effect on the material performance.In order to intelligently control the drilling process of CFRP and improve the machining quality,it is necessary to conduct on-line monitoring research on the stratified damage state of CFRP drilling.Therefore,destructive delamination experiment and all-factor drilling experiment were carried out in this paper to study time-frequency characteristics of acoustic force monitoring signal,drilling delamination damage identification and delamination damage size prediction of CFRP delamination damage.The main research contents are as follows:(1)A delamination damage monitoring platform of CFRP based on vertical machining center was built.Based on the delamination damage mechanism of CFRP,stratified acoustic emission and axial force monitoring signals were collected by destructive delamination experiments,and the time-frequency analysis method was used to analyze and process the acoustic and force monitoring signals.The variation law of axial force and time-frequency characteristics of acoustic emission signals during the formation and expansion of delamination damage at the outlet of CFRP holes were obtained.(2)In all factors drilling experiment acquisition,power monitoring signal,using wavelet packet threshold de-noising technology to collected,force signal noise reduction processing,integrated signal time-frequency analysis technology to extract the drilling monitoring signal time-frequency characteristic,implements the CFRP drilling delamination damage identification,and use the industrial CT scanner to measure the drilling delamination crack length,The delamination identification results were verified by combining with the actual delamination damage morphology,and the relationship between the delamination crack length and drilling parameters was analyzed.(3)Based on support vector regression machine technology,extraction and quantitative processing drilling CFRP delamination damage acoustic emission,axial force monitoring signal characteristics as the model input,with drilling stratification factor as the model output,CFRP delamination damage crack size prediction model is constructed,after training and testing found that the prediction model has higher accuracy and reliability,Based on acoustic emission and axial force signals,the delamination damage of CFRP drilling can be predicted accurately.