Surface Adaptive Ultrasonic Testing Of CFRP Radius With Phased Array

Nondestructive testing of carbon fiber reinforced resin matrix composite(CFRP)radius is an important part of quality control of CFRP compone nt.In the ultrasonic testing of the CFRP radius,the curved surface makes the wave difficult to normally incident.When the wave incident obliquely,the layered structure and the elastic anisotropy of the material make it difficult to detect the defects quantitatively.In order to solve the above problems,the surface adaptive ultrasound(SAUL)method based on phased array ultrasonic acquisition was researched.Inspection of CFRP radius in T shaped T700/ epoxy resin component with SAUL method was researched.Combined with the microstructure characteristics and the accurate measurement of elastic constants of materials,ultrasonic phased array testing model of CFRP radius was established to study quantitative detection of delamination in radius with SAUL.Through the parameters selection and elementary directivity correction,the sizing and locating of defects in CFRP radius was realized with SAUL method.Besides,the ability of SAUL method to detect defects at different angle and detect multi-defects was researched.For restraining artifacts in image when defect multi-defects in radius,a scheme that combines SAUL with receiving focusing was proposed,thus improved the testing results.The main research contents are as follows:1.Elastic constants of unidirectional T700/Epoxy resin plate were measured based on wave propagation theory of anisotropic media.A rotation setup was built and the cross-correlation technique was utilized for velocity measurement and calculation in different directions.The simulated annealing algorithm was implemented to inverse the velocity data and five independent elastic constants C11,C13,C33,C44 and C66 was determined to be 12.88 GPa,6.39 GPa,126.83 GPa,4.85 GPa and 2.97 GPa.The phased array ultrasonic testing model of L shaped CFRP specimen was established based on metallograph of T shaped component and elastic constants matrix transformation.2.The model above was applied to simulate the surface adaptive ultrasound testing of a delamination which has a depth of 1.5 mm and circumferential length of 4.5 mm in radius.Compared with electronic scanning results,normal incident ultrasonic wave on curved surface was realized thus avoid not only the front surface echo and flaw echo bending but also the artifacts in B scan image.Besides,the image obtained with SAUL has a higher signal-to-noise ratio(SNR)for that the SNR of defects calculated from time domain signal improving to 29.3 dB from 8.9 dB.3.The straight part surface echo and interface echo was strong because that SAUL detection parameters were not properly selected,thus makes quantitative testing difficult.By adjusting the detection frequency or the distance from the probe the center of the R region,the effects of the interferential reflected echo was restrained,and the detection accuracy of the defect was improved by correcting the incident acoustic pressure according to elementary acoustic field directivity.The SAUL method was then used to inspection the actual CFRP specimens by applying the parameters selected and directivity correction.Experimental results show that The depth quantitative error is less than 1% and the quantitative error of circumferential length was less than 6%.4.The ability of SAUL to detect defects at different angle was researched by simulation.Results show that with the deflection angle of delamination increasing from 5° to 20°,the sizing error of circumferential length was from 0.45% up to 6.26% and the deflection angle sizing error from 0.24 ° to 3.36°.