Measurement of impact characteristics in a string using electrospun PVDF nanofibers strain sensors

Mechanical behaviour of solid structures upon the action of an impact force is an important indicator of the structures' performance. The location of an impact force and the subsequent dynamic characteristics of strain and deflection on a string are important parameters for applications such as musical instruments and sports rackets. This paper proposes a flexible, lightweight and self-powered polyvinylidene fluoride (PVDF) strain sensor for attachment on a string. PVDF nanofibers with a high fraction of beta-phase and crystallinity are prepared using the electrospinning process. A linear relationship between the voltage output of the sensor and the input strain is observed. The variation of the output voltage of the sensor with the location of hit and the velocity of a ball is obtained with the help of a high-speed camera. A new strain-input based theoretical model formulation has been derived. The theoretical model and strain inputs from the developed PVDF strain sensors are used to measure the location of the force of impact and the corresponding deflection in the string. The results are compared to the high-speed camera recordings and show that the current method can accurately measure the impact location and deflection in a single string. (C) 2020 Elsevier B.V. All rights reserved.