The influence of tensile stress on inductively coupled piezoceramic sensors embedded in fibre-reinforced plastics

This article demonstrates that embedded piezoelectric sensors can survive loads much higher than predicted by their material properties. It shows the potential for piezoceramic sensors to estimate structural loads when embedded in composites. To show this, embedded sensors were subjected to stresses and strains which were significantly greater than the recommended operating limits of their piezoceramic constituents. A novel data acquisition method enabled ultrasonic guided wave measurements to be recorded wirelessly from the embedded transducers, key to minimising the impact of embedded transducers. The data recorded by the piezoceramic transducers exhibited a reversible load dependence, with the measurements returning to the stress-free values upon removal of the applied load. The guided wave measurements recorded by transducers embedded in glass fibre–reinforced composites showed no degradation after being subjected to tensile strains of 1.07%. When embedded in a carbon fibre–reinforced plastic sample which was loaded to failure, the transducers remained operational; however, sensor performance was shown to be degraded after being subjected to tensile stresses as high as 606 MPa. This offers the potential to build sensors to characterise overload in a component.