Research On Ultrasonic Attenuation Caused By Voids In CFRP Based On Real Morphology Void Model

The research on porosity in Carbon Fibre Reinforced Plastics (CFRP) determined by ultrasonic inspection is one of the hot topics in non-destructive testing. Regular and random void model(RVM) are two main types of ultrasonic attenuation method. However theoretical results calculated from the former model have large deviation with experimental results for the hypothesis of regular void geometry and fixed distribution function. And diviation between theoretical results simulated by RVM and experimental results obviously decreases for the comprehensive consideration of the complex and random void morphology. Nevertheless voids constructed by mathematics are different from reality and specimens with large void length dispersion show unsatisfactory modeling results. Real morphology void model (RMVM) is proposed to investigate the complex relationship among porosity, void morphology and ultrasonic attenuation coefficient.The investigated subject is CFRP laminar with 16-layer unidirectional prepregs. Median filter and binarization processing are introduced into 441 CFRP metallographs made by serial sections. So that real void morphology can be obtained and then RMVM, which has the porosity range of 0.58% -3.49%, is established. The finite difference time domain(FDTD) method is used to simulate ultrasonic propagation in RMVM. Results show that attenuation coefficient(α) increases as the porosity(P) grows and the relationship between them is a=0.905+1.053P+0.039P2. Besides the attenuation coefficient of RMVM at the same porosity distributes in a range and the range grows as porosity increases, namely the attenuation coefficient and porosity present zonal distribution. Experimental results show good conformity with the simulated results. So it’s feasible to do simulation with RMVM. In addition the attenuation coefficient variations caused by area, width and height of voids are investigated.The RMVM established here factually describes the complex and random void morphology in CFRP. So it provides a good model foundation to investigate ultrasonic scattering mechanism caused by voids in CFRP.