Washable, wearable triboelectric sensors

Bird strikes, hailstone impacts, and other type of mechanical collisions are quite frequent for a number of crucial and important structures, including aircrafts, wind turbines, bridges and other composites structures. These impacts harm the integrity of the composite laminates used in their structures which results in delamination and other failures which reduces their overall lifetime. Hence, the prediction of the damage induced by these impacts is of vital importance to assess the integrity of the composite structures. This paper suggests a triboelectric sensor based on polyvinyl fluoride nanofibers which is used to measure the velocity of the impacts and predict the structural integrity of the composites. For the purpose an experiment is designed where composite plates are subjected to controlled velocity impacts using a drop-weight impact machine. During the experiment, the fabricated triboelectric sensor is adhered to the composite specimens with the aim to investigate the effect of the velocity of the impacts on the sensor electric responses. Our results show that the sensor electric response increases with the increase of the impact velocity. Additionally, the produced voltage and current outputs show a linear directly proportional relationship to the measured impact velocity, which facilitates greatly the estimation of the impact velocity from the measured electric response. Furthermore, the paper also proves that the sensor electrical responses can be also used to estimate the size of the delamination caused by the impacts. The findings of this research demonstrate the potential of triboelectric sensors for impact velocity monitoring and propose a new approach to predict the damage caused by impacts in composite structures. These results are of a great interest for the industry as the delamination caused by impacts is very difficult to detect by visual inspections.