Focal Law Optimization and Acoustic Field Simulation of PAUT on CFRP Radii

The focal law and ultrasonic field of phased array ultrasonic testing (PAUT) on carbon fiber reinforced plastic (CFRP) laminates radii were studied based on numerical modeling. The geometrical and elastic anisotropy factors were taken into account respectively and the corresponding focal laws were calculated. Comparing with the results of the elastically isotropic flat plate, the results show that the original delay times of the linear array elements presented parabolic distribution and the focusing effect in the elastically isotropic radii was obvious. The actual focal point, however, was 1.6mm ahead of the preset focus depth of 3 mm. Under the same focus law, the focusing in the radii of CFRP laminates deteriorated significantly, and the structural noise was evident. After the optimization of focus law considering geometric shape, the energy of focusing beam was increased, but it was quite local in the subsurface. With further consideration of the elastic anisotropy, the incident acoustic energy was increased from the both sides, and the focusing was significantly improved.