Since 2012 there has been a rapid rise in the development of triboelectric nanogenerators due to their potential applications in the field of energy harvesting and self-powered sensors for vibrations, accelerations, touches, pressures and other mechanical motions. This study suggests a novel triboelectric nanogenerator based on the interaction between polyvinylidene fluoride and polyvinylpyrrolidone submicron fibers. Polyvinylpyrrolidone is introduced as a new material for the TENG because of its tendency of losing electrons easily, while polyvinylidene fluoride is selected for its strongelectron attracting ability. Electrospinning is suggested as a fabrication method for the nanofibers due to its simplicity, versatility and low-cost. Furthermore, the paper explores the possibility to use this triboelectric nanogenerator as a self-powered pressure sensor. For this purpose, the nanogenerator is subjected to dynamic mechanic analysis which produces controlled pressure forces applied with a certain frequency. This is the first work to suggest the use of dynamic mechanical analyzer to study the relation between the applied mechanical stimulus and the electric responses of the triboelectric nanogenerator. Eventually the sensitivity of the nanogenerator to different pressures is analysed. A directly proportional relationship is found between the pressure applied and the resultant voltage and current amplitudes. The developed nanogenerator reacts to pressure in real time and as a sensor it exhibits a very high sensitivity and low experimental error for repeated measurements. The main contributions of this study are the development of a novel nanogenerator based on the triboelectric effect between polyvinylidene fluoride and polyvinylpyrrolidone electrospun fibers and the investigation for its potential use as a selfpower pressure sensor. Eventually, the paper explores the advantages of dynamic mechanical analyzer for pressure analysis.

In this article, the effect of polycaprolactone nanofibers on the dynamic behavior of glass fiber reinforced polymer composites is investigated. The vibratory behavior of composite beams in their pristine state (without any nano modification) and the same beams modified with polycaprolactone fibers is considered experimentally. The experimental results show that the incorporation of polycaprolactone nanofibers increases the damping; however, it does not significantly affect the natural frequencies. Additionally, the paper analyses the effect of polycaprolactone nanofibers on the impact behavior of glass fiber/epoxy composites. This has already been analyzed experimentally in a previous study. In this work, we developed a finite element model to simulate the impact behavior of such composite laminates. Our results confirm the conclusions done experimentally and prove that composites reinforced with polycaprolactone nanofibers are more resistant to damage and experience less damage when subjected to the same impact as the pristine composites. This study contributes to the knowledge about the dynamic behavior and the impact resistance of glass fiber reinforced polymer composites reinforced with polycaprolactone nanofibers. The findings of this study show that interleaving with polycaprolactone nanofibers can be used to control the vibrations and improve the impact damage resistance of structures made of composite mats as aircrafts or wind turbines.

This version is available at https://strathprints.strath.ac.uk/61788/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. 1 Vibratory behaviour of glass fibre reinforced polymer (GFRP) interleaved with Nylon NanofibersCristobal Garcia AbstractThe main purpose of this study is to investigate the influence of the inclusion of nylon nanofibers on the global dynamic behaviour of GFRP composite laminates. The vibration behaviour of GFRP composites reinforced with nylon nano-fibres is considered experimentally and numerically using a finite element model. The present analysis of clamped-clamped beams investigates the natural frequencies, the damping and the stiffness of virgin and nano-interleaved composite laminates. The numerical modelling uses ANSYS Workbench 16.2. Experimental and numerical results showed a significant effect of the nylon nanofibers on the dynamic behaviour of the composites. Nano-modified composites demonstrated a consistent increase in the damping ratio and inter-laminar strength. However, the variation in natural frequencies and stiffness due to the nanofibers was very small. This study contributes to the knowledge about the macro dynamic properties of nylon interleaved GFRP composites. It demonstrates that a simple FE model can be used to accurately predict the dynamic behaviour of such nano-composites.

Highlights This study investigates the potential of triboelectric sensors for detection and measurement of impacts in composites structures for the first time. The triboelectric sensor presents a very large energy detection range (140 times wider as compared other impact triboelectric sensors). The voltage and current outputs show good sensitivity, high linearity and fast response time. Great potential for impact monitoring in composites structures as aircrafts or wind turbines. The performance of a triboelectric and commercial sensor for monitoring of impacts is compared.

Recently, triboelectric nanogenerators (TENGs) are generating increasing interest due to their important applications as energy harvesters and self-powered active sensors for pressures, vibrations and other mechanical motions. However, there is still little research within the research community on their potential as selfpowered impact sensors. This paper considers the development of a novel triboelectric nanogenerator, which is prepared using a simple and economic fabrication process based on electrospinning. Furthermore, the paper studies the changes in the generated electric response caused by small energy impacts. For the purpose, the TENG electric outputs generated by the impact of a free-falling ball dropped from different heights are investigated. The idea is to investigate the relation between the electric responses of the nanogenerator and the energy of the impact.The experimental results demonstrate that the voltage and current outputs increase linearly with the increase of the impact energy. Moreover, the electric responses of the triboelectric nanogenerator show a very high sensitivity (14 V/J) to the changes in the impact energy and good repeatability. The main achievements of this paper are in the development of novel triboelectric nanogenerator composed of polyvinylidene fluoride nanofibers and a thin film of polypropylene, and its successful application as an impact sensor for real-time assessment of small energy impacts. 2 1 Introduction An impact sensor plays a critical role in vehicle safety, fast medical assistance of elderlies and structural health monitoring. For example, in the event of a car crash an impact sensor detects the collision to release an air-bag for the protection of the passengers. In the case of falls in the elderly, an impact sensor can be used to inform about the accident and provide a fast-medical assistance. Other practical examples could be detection of impacts in hail storms, where impacts are responsible for a considerable number of accidents in aircrafts, wind turbines and other civil infrastructures. Therefore, the sensing and the quantification of impacts is of vital importance for a number of applications as impacts can seriously affect the health and safety of humans. Recently, various approaches have been developed and applied for detection and measurement of impacts in environment as for example piezoelectric sensors [1, 2], capacitive sensors [3], optical sensors [4], acoustic sensors [5] and vibration sensors [6]. Special attention deserves the works of Yang's group [7, 8] which investigates the applications of flexible piezoelectric sensors for detection and measurement of pressures, which can be used for important applications as sleeping monitoring, tactile measurements, or sensing of human heartbeats. Additionally, other authors as [9]investigated the potential of piezoelectric nanogenerators as acceleration sensors for real-time collision monitoring, which has important applications as vehicle safety monitoring. However, most of these technologies require...