Through transmission ultrasonic inspection of fiber waviness for thickness-tapered composites using ultrasound non-reciprocity: Simulation and experiment

This study proposed the use of ultrasound non-reciprocity in periodic structures to inspect fiber waviness in thickness-tapered composites. Ultrasound propagation in plain and thickness-tapered composites with complex microstructure were precisely modelled using TexGen® and OnScale® simulation software. Ultrasound non-reciprocity and attenuation was comparatively calculated to inspect fiber waviness through both simulation and experiment. After comparison, energy of transmitted waves was found to be sensitive to the presence of fiber waviness in plain composites, however, thickness-dependent ultrasound attenuation introduces difficulties in determining the diagnosis baseline for thickness-tapered composites. On the other hand, fiber waviness introduces direction-dependent nonlinearity in the wavy region, which introduces a disparity between the two transmitted signals when the propagation direction is reversed. Ultrasound non-reciprocity, defined by the time-of-flight difference between the two transmitted signals, demonstrated its efficiency for fiber waviness inspection in both plain and thickness-tapered composites regardless of variations in the thickness.