Phase coherence weighted ultrasound total focusing method towards the improved imaging of CFRP defects

Defect imaging in carbon fiber reinforced polymer (CFRP) combining the phase coherence imaging (PCI) and the total focusing method (TFM) is investigated in this study, in order to overcome the adverse influence on defect imaging from wave propagation anisotropy, inter-ply reflection, and high attenuation. Three kinds of coherence factors are proposed first to be combined with the wave velocity corrected TFM for defect imaging in CFRP. Then, the much stronger phase coherence (PC) from the signals scattered from the defect than those from the inter-ply is discovered experimentally. Finally, with the proposed PC-weighted-TFM, the noise of imaging from the inter-ply reflection is largely suppressed, resulting in largely improved signal-to-noise ratios of imaging with defects at different depths and close to each other. The findings demonstrate that the proposed PC-weighted-TFM is of great application potential in nondestructive testing of CFRP.