Ultrasonic inspection of hybrid polymer matrix composites

Polymer-matrix composite (PMC) materials used for a wide variety of engineering applications are often manufactured as hybrid carbon- and glass-fibre-reinforced laminates to exploit the respective properties of each material. From the exterior, hybrid PMCs are visually deceptively similar to monolithic laminates, but just as their mechanical, electrical and thermal properties differ, so their acoustic properties vary due to hybridisation. In this article, the mechanical and structural properties of hybrid PMC laminates pertinent to acoustic measurements and that affect sound propagation, such as: material density, stiffness, and laminate layup sequence, and their influence on ultrasonic defect detection, are explained via a detailed analysis of the ultrasonic waveforms, experimental inspection data, and analytical modelling.