Abstract
Debonding in a skin-stringer panel is one of the main problems in actual application of carbon fiber reinforced plastic (CFRP) composite. Although an ultrasonic structural health monitoring technique using mode conversions of Lamb waves can evaluate this defect effectively in infinite-width CFRP laminates, this method cannot be applied directly to the bonded structure with a finite-width stringer. Hence, in this research, the mode conversion behavior in a simple finite-width CFRP laminate with an artificial delamination was investigated as a basic study. The theoretical dispersion curves of Lamb waves in the finite-width laminate were calculated by a semi-analytical finite element method. Then, the experiments were conducted at various frequencies with an acousto-ultrasonic system based on macro fiber composite actuators and fiber Bragg grating sensors for the investigation of Lamb wave propagation behavior in the finite-width laminate. The results indicated that mode conversion occurs in the delaminated area of the finite-width CFRP laminate. Therefore, the mode conversion of Lamb waves has a possibility to detect delamination damage in finite-width composite structures.
