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Title: The effect of nanofibers for improving the dynamic and mechanical properties of composite laminates and their application as self-powered sensors
Author: Pariente, Cristobal García
ISNI:       0000 0004 8502 8343
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2018
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One of the main objectives of this thesis is to investigate the effect of the inclusion of nanofibers on the global dynamical and mechanical properties of composite laminates. For this aim, the natural frequencies, damping, interlaminar strength and impact response of pristine and nanomodified composites are determined experimentally and numerically using a finite element model. Experimental and numerical results showed a significant effect of the nanofibers on the mechanical and dynamic properties of the composites. Nanomodified composites demonstrated a consistent increase in the damping, interlaminar strength and impact resistance. However, the variation in the natural frequencies was very small. This study expands the knowledge about the macro mechanical and dynamical properties of composites reinforced with nanofibers. Furthermore, it proposes finite element models to simulate with high accuracy the mechanical and vibratory behaviour of pristine and nanomodified composites. These findings are of great interest for the research community and for industry as composite laminates reinforced with nanofibers could be potentially used to improve the properties of the composite structures used in aircrafts, wind turbines and other civil structures. The other major objective of the thesis is to investigate the potential applications of nanofibers as self-powered triboelectric sensors. The first triboelectric sensor was invented in 2012 and it has become one of the most important innovations in the field of self-powered sensing technologies. As compared to traditional sensors, triboelectric sensors are self-powered and do not require and external power supply or battery to sense the mechanical stimulus. As a result, they are maintenance free and energy independent, which results in important cost-savings. In this work, the potential of two new classes of triboelectric sensors for monitoring of pressures and impacts is demonstrated. To carry out this investigation, the developed triboelectric sensors are subjected to controlled pressures and impacts using the techniques of dynamic mechanical analysis and drop weight impact tests, respectively. The experimental results proved that the sensors generated electric responses are affected by the magnitude of the mechanical stimulus and their amplitude increases linearly under stronger pressures/impacts. Furthermore, the sensor electric responses show a large detection range, high sensitivity, good reproducibility, and fast response time, which is essential for the practical applications of the sensor. The main contributions of this study are the development of two novel triboelectric nanogenerators and active sensors based on polyvinyl fluoride nanofibers and their investigation for its potential use for monitoring of pressures and impacts. The results of this work successfully demonstrated that the developed triboelectric sensor measure dynamic pressures and impacts in real time, which has important applications in monitoring systems, vehicle safety, and touch screens. These findings are the utmost importance as the new developed sensors could be utilized as sustainable and maintenance free sensors with the advantages of easy fabrication and low-cost processing technology. In conclusion, this thesis contributes to the knowledge about nanofibers in terms of their applications to improve material and structural properties of composite laminates and their use as two novel nanostructured sensors for detection and measurement of pressures and impacts.
Supervisor: Trendafilova, Irina Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral