[3B1] Experimental trials using the RAPID algorithm for structural health monitoring of aerospace carbon composites
T Bertenshaw
GKN Aerospace Services Ltd, UK
Within the ASCEND project consortium, an Aerospace Technology Institute (ATI)-funded multi-partner project, GKN has carried out some research developing structural health monitoring (SHM) of carbon composite structures. This is to assist with the qualification of secondary-bonded structures in civil aerospace. The technique uses Lamb waves with a sparse array of piezo transducers, where the data is reconstructed using the RAPID algorithm. This study includes the initial equipment downselection, acquisition of piezo transducers and manufacture of composite test panels. It also covers the methods for bonding piezos onto the composite, which includes initially bonding with cyanoacrylate, then later with a low-temperature (100°C) curing epoxy film adhesive. It considered various bonding strategies to ensure good coupling, but there was also an analysis of signals acquired from the equipment from specific transducer pairs. The results showed that disbonds produced from a polytetrafluoroethylene (PTFE) insert (20 mm × 20 mm) can be detected, especially in central locations, but factors such as thickness variation, panel homogeneity and the pulse generator equipment itself can all effect the reconstruction and accuracy of the RAPID algorithm. The RAPID algorithm was modified during the course of the project with the assistance of the Centre for Modelling and Simulation (CFMS).
