Guided Wave Propagation and Damage Detection in Composite Pipes Using Piezoelectric Sensors

Composite materials have many attractive properties, e.g. light-weight combined with high mechanical strength, and are recognized as an enabling technology for deep-water high pressure high temperature (HPHT) and corrosive environment applications. However, composite still has a barrier to entry in relation to steel due to limited field experience and lack of systematic failure prediction and assurance of in-service performance. Advances in such areas would enable the use of composites in a wider range of applications. Evaluation of in-service prototypes offers a partial solution but is costly. Thus a method that allows constant health monitoring of the composite in real-time and in-situ would be extremely useful. Ultrasonic guided wave-based structural health monitoring (SHM) technology is one of the most prominent options in non-destructive evaluation and testing (NDE/NDT) techniques. To investigate the feasibility of guided wave-based SHM for composite pipes, propagation characteristics of guided waves in an epoxy hybrid carbon/glass fibres pipe are systematically studied using finite element (FE) simulation and experiments. Both axisymmetric modes of propagation, the longitudinal L(0,n) and torsional T(0,n) modes are considered in the simulation process, however only the longitudinal modes can be captured by the piezoelectric sensors. Additionally, the tuning curves experimentally plotted are used to obtain the frequency with the maximum amplitude of each guided mode. Finally, guided waves in the composite pipe are tested with artificial defects (gel coupled coins) to understand the behaviour of guided waves after interaction with the defects. The different condition of artificial defects, e.g., the defect size and defect location are studied to find out the proper condition and limitation of using guided waves to monitor and inspect composite pipes.