The goal of this work is to investigate the piezoelectricity of composite laminates embedded with layers of zinc oxide (ZnO) nanowires. ZnO nanowire embedded composites have the potential to sense and actuate giving the potential for these smart composites to serve the function of being load bearing structures and monitoring the integrity of the structure. This work examines the piezoelectric characteristics of composite beams by investigating their electromechanical coupling in the form of vibration under the presence of electrical excitation. With the help of a mathematical model, piezoelectric constants are estimated for these samples. A layer of ZnO nanowires were grown on plane woven fiberglass fabric that was incorporated into a carbon fiber epoxy composite. The beam deflection velocity was measured as a varying voltage was applied to the composite. Using Hamilton's Principle and Galerkin's method of weighted residuals, a mathematical model was derived to estimate piezoelectric constants for the composites from the experimental data. Piezoelectric properties were determined using vibrational testing and a mathematical model. Piezoelectric constants h31, g31, and d31 were estimated to be 9.138 E7 V/m, 6.092 E-4 Vm/N, and 2.46 E-14 respectively. To demonstrate the electromechanical coupling, ZnO nanowire composites were bonded to Al beams that were progressively damaged to determine if a change in electrical impedance could be observed to correspond to the change in structural impedance of the host beam. Changes in impedance were detected by a change in root mean squared deviation damage metric M. A significant correlation was shown between increasing damage in the host beam and an increase in damage metric M. / Master of Science / A major problem facing both commercial and military aircraft fleets is aircraft grounded time due to inspection. Inspection times tend to be lengthy since visual inspection cannot detect all types of incurred damage an aircraft may face. In the case of composite aircraft structures, a special type of damage known as delamination (when layers of the composite structure become un-bonded) can occur. Since delamination is not always visible from the surface, and composite structures cannot be taken apart since they are made in one piece; additional damage detection methods are necessary. Impedance-based structural health monitoring (IBSHM) is one technique of nondestructive evaluation (NDE) that examines changes in vibrational response of the structure in order to detect damage. A novel approach to IBSHM is incorporating zinc oxide, a type of piezoelectric material, inside the composites due to its ability to deform in the presence of an electric field or generate a voltage when stressed. The goal of this research is to determine piezoelectric properties of composites with ZnO nanowires grown on inner layers of the laminates. Piezoelectric properties were determined using vibrational testing and a mathematical model. To demonstrate the electromechanical coupling, ZnO nanowire composites were bonded to Al beams that were progressively damaged to determine if a change in electrical impedance could be observed to correspond to the change in structural impedance of the host beam. Changes in impedance were detected by a change in root mean squared deviation damage metric M. A significant correlation was shown between increasing damage in the host beam and an increase in damage metric M.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/82502 |
| Date | 14 March 2018 |
| Creators | Offenberger, Sean Alan |
| Contributors | Aerospace and Ocean Engineering, Philen, Michael K., Patil, Mayuresh J., Seidel, Gary D. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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