Characterization of fibre orientation in FRP using pitch-catch ultrasonic technique

This paper presents a non-destructive ultrasonic testing method to examine the fiber orientation of Fiber-Reinforced Polymer (FRP) composite laminates prior to and/or in service. A one-sided pitch-catch setup was used in the detection and evaluation of ultrasonic wave behavior and fiber orientation in the FRP composite laminates. Two ultrasonic transducers were joined side-by-side with an oblique angle between and used in the pitch–catch mode on the surface of the composites. The pitch–catch signal was found sensitive to the fiber orientation in the composites. Based on models of wave propagation in fibrous materials, a simple empirical relationship between the angle of ultrasonic wave propagation with respect to the fibers and the amplitude ratio of the reflected and incident ultrasonic wave is proposed. The experimental data show that this relationship fits the experimental results very well.