Damage detection in laminated composites using pure SH guided wave excited by angle beam transducer

Carbon fiber reinforced polymer (CFRP) composites have been widely used in aerospace structures due to their high specific strength and stiffness, resistance to corrosion, and lightweight. However, it has posed new challenges for implementing guided wave-based structural health monitoring (SHM) techniques due to the general anisotropic behavior and complicated wave-damage interaction scenarios in composites. This paper presents a new methodology for detecting various types of composite damage such as simulated delamination and actual impact damage using pure shear horizontal (SH) wave generated by adjustable angle beam transducers. For the first time, angle beam transducers were successfully applied to excite pure SH0 wave in a 2-mm quasi-isotropic composite plate. The pure SH0 wave excitation was verified by a three-dimensional (3D) finite element (FE) simulation. SH0 wave propagation and interaction with the delamination were further investigated numerically and strong trapped waves within the delamination region were observed. Experimental validations were conducted to detect simulated delamination by Teflon insert using pure SH0 wave. A good match between the FE simulation and the experiment was achieved. Pure SH0 wave was also utilized to detect actual impact damage in the quasi-isotropic CFRP composite plate. It can be found that the SH0 wave is sensitive to both delamination and impact damage, and a significant amplitude drop is observed due to the presence of different types of damage. Both numerical and experimental results demonstrated the effectiveness of pure SH0-wave detection of various damage types in composites using angle beam transducers.