Novel Multi-Functional sensors:
Through the technology innovations in inkjet printing, our group has designed and developed “tailor-to-order” multi-functional sensors which can be used for monitoring the quality and integrity of bondlines. This is in particular of high interest for composite bonded structures such as repair patch as well as lap joints and bonded interfaces (i.e. skin/stringer) where the quality of the curing affects the integrity of the joint. The sensor can be used for cure monitoring as well as the integrity of bondline through the life-cycle of the structure. The cure process of the bondline is assessed via Impedance spectroscopy measurements while the integrity checks are carried out via electrical resistance.
Our group has worked with a variety of piezoelectric transducers for both actuation and sensing. Piezo ceramic transducers are ideal as both sensors and actuators, since they require very little power, allow for multimode excitation, are very small and light. However, they are brittle and they require wiring and shielding.
PVDF (Polyvinylidene fluoride) is a piezo-polymer (thin films) which has very low density, is flexible i.e. it is ideal for curved or complex surfaces, it is chemically inert, tough and has a very low dielectric permittivity resulting in a very high voltage coefficient making it ideal as a sensor but due to low dielectric constant they are not ideal as actuator. We have also designed interdigitated electrode (IDE) patterning, resulting in a complex distribution of the electric field in the material is that enables modal selectivity. This will result in selecting particular wave modes which are most sensitive to a certain type of damage, e.g. debonding.