Reliability Analysis of an Ultrasonic Guided Wave Based Structural Health Monitoring System for a Carbon Fibre Reinforced Thermoplastic Torsion-box

Certification is the key step towards the implementation of structural health monitoring (SHM) as part of condition based maintenance programmes of aircraft fleets. That can only be accomplished by demonstration of system performance in multiple scenarios and in a statistically relevant way. This paper describes a fully computational approach for reliability assessment of an ultrasonic guided wave (GW) based SHM system for a full-scale stiffened panel of a horizontal stabilizer torsion-box entirely made of carbon fibre reinforced thermoplastic. A pseudo-stochastic nature is attributed to the damage index values calculated from the finite-element signals, allowing hit-miss data to be generated. That data is in turn employed for the computation of probability of detection curves and relative operating characteristics. The results of this research show that detailed damage diagnostics in full-scale complex composite structures can be achieved by using ultrasonic GWs under the hotspot monitoring philosophy. Moreover, it is demonstrated that properly validated models of the monitoring environment can be used for reliability analysis of GW based SHM systems for full-scale complex composite structures, thereby reducing the need for extensive and costly experimental test campaigns, which in turn can contribute to an acceleration of the establishment of a certification framework for SHM systems.