Статьи на перевод PVDF_P(VDF-TrFE) / 2012-Dodds,J-Thesis (Development of Piezoelectric Zinc Oxide Nanoparticle-Poly(Vinylidene Fluoride))
.pdfDevelopment of Piezoelectric Zinc Oxide Nanoparticle-Poly(Vinylidene Fluoride) Nanocomposites for Sensing and Actuation
By
JOHN STEVEN DODDS
B. S. (California State Polytechnic University, San Luis Obispo) 2010
THESIS
Submitted in partial satisfaction of the requirements for the degree of
MASTER OF SCIENCE
in
Civil and Environmental Engineering
in the
OFFICE OF GRADUATE STUDIES
of the
UNIVERSITY OF CALIFORNIA
DAVIS
Approved:
________________________
Kenneth J. Loh, Chair
________________________
Lijuan Cheng
________________________
Sashi K. Kunnath
Committee in Charge
2012
i
Acknowledgements
I would like to thank Prof. Kenneth Loh for his continual mentoring and support. His initial suggestion of the topic was vital, along with his assistance throughout the process to keep me motivated and guide me. Fellow lab members also provided important assistance and training, along with a positive and encouraging work environment. Also, I would like to thank my committee members, Prof. Sashi Kunnath and Prof. Lijuan Cheng, for serving on my thesis committee and for their guidance throughout my graduate studies.
I would like to express my sincere gratitude to the UC-MEXUS-CONACYT program and the College of Engineering, University of California, Davis, for their financial support of this research. I would also like to thank the entire staff of the Northern California Nanotechnology Center (NC2), especially Michael Irving and Corey Wolin, for their assistance with film thickness measurements, e-beam deposition, and photolithography. I would especially like to thank my family, Fred Meyers, and Tomiko Oden, without whom I would not have been able to finish this thesis.
ii
Abstract
Structural health monitoring (SHM) is vital for detecting the onset of damage and for preventing catastrophic failure of civil infrastructure systems. In particular, piezoelectric transducers have the ability to excite and actively interrogate structures (e.g., using surface waves) while measuring their response for damage detection. In fact, piezoelectric transducers such as lead zirconate titanate (PZT) and poly(vinylidene fluoride) (PVDF) have been used for various laboratory and field tests and have demonstrated significant advantages as compared to visual inspection and vibrationbased methods, to name a few. However, PZTs are inherently brittle, and PVDF films do not possess high piezoelectricity, thereby limiting each of these devices to certain specific applications. Piezoelectric nanocomposites, which enjoy a combination of the best properties of these material types, are at the forefront of emerging SHM technologies.
The objective of this study is to design, characterize, and validate piezoelectric nanocomposites consisting of zinc oxide (ZnO) nanoparticles assembled in a PVDF copolymer matrix for sensing and actuation. It will be shown that these films provide greater mechanical flexibility as compared to PZTs, yet possess enhanced piezoelectricity as compared to pristine PVDF copolymers. The results obtained from this research will be crucial for future SHM applications using these piezoelectric nanocomposites.
This study began with spin coating dispersed ZnO-based solutions for piezoelectric nanocomposite fabrication. The concentration of ZnO nanoparticles was varied from 0 to 20 wt.% (in 5% increments) to determine their influence on bulk film piezoelectricity. Second, their electric polarization responses were obtained for quantifying thin film remnant polarization, which is directly correlated to piezoelectricity.
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Based on these results, the films were poled at 50 MV-m-1 to permanently align film electrical domains and to enhance bulk film piezoelectricity.
Next, a series of sensing validation tests was performed. The voltage generated by poled ZnO-based thin films was compared to commercially poled PVDF copolymer thin films. The hammer impact tests employed showed comparable results between the PVDF-TrFE/ZnO films and commercial samples. It was concluded that increasing ZnO content enhanced bulk film piezoelectricity. The films have been further validated for sensing using different energy levels of hammer impact, different distances between the impact locations and the film electrodes, cantilever free vibration testing for dynamic strain sensing, and load frame testing for sensitivity and linearity measurements.
Actuators were also constructed by integrating fingered electrodes with PVDFTrFE/ZnO films. Actuation tests using the pitch-catch methodology were performed on a test pipe structure. The presence of guided waves was first confirmed by measuring pipe vibrations using commercial Macro Fiber Composite (MFC) sensors. Additionally, damage detection was validated using a pitch-catch setup. Overall, a piezoelectric nanocomposite transducer was successfully fabricated and demonstrated for use as both a sensor and an actuator for SHM.
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Table of Contents |
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Acknowledgements ......................................................................................................... |
ii |
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Abstract .......................................................................................................................... |
iii |
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Table of Contents ............................................................................................................ |
v |
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List of Figures............................................................................................................... |
viii |
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List of Tables ................................................................................................................... |
x |
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List of Equations............................................................................................................. |
xi |
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Nomenclature ................................................................................................................ |
xii |
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Chapter 1: Introduction ................................................................................................... |
1 |
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1.1 |
Structural Health Monitoring Motivation ................................................................ |
1 |
1.2 |
Thesis Goal and Outline ....................................................................................... |
2 |
Chapter 2: A Review of Structural Health Monitoring ...................................................... |
4 |
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2.1 |
Introduction........................................................................................................... |
4 |
2.2 |
Structural Health Monitoring Solutions .................................................................. |
4 |
2.3 |
Piezoelectric Material Theory................................................................................ |
8 |
2.4 |
Piezoelectric Material Applications....................................................................... |
13 |
2.4.1 Piezoelectric Sensors.................................................................................... |
14 |
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2.4.2 Piezoceramic Actuators ................................................................................ |
15 |
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2.4.3 Piezoelectric Composites.............................................................................. |
18 |
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Chapter 3: Material Fabrication and Ferroelectric Testing.............................................. |
21 |
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3.1 |
Introduction.......................................................................................................... |
21 |
3.2 |
Nanocomposite Fabrication ................................................................................. |
21 |
3.3 |
Ferroelectric Testing ............................................................................................ |
26 |
3.3.1 Ferroelectric Setup........................................................................................ |
26 |
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3.3.2 Ferroelectric Results ..................................................................................... |
28 |
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v |
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3.4 |
High Electric Field Poling ..................................................................................... |
32 |
Chapter 4: Sensing........................................................................................................ |
34 |
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4.1 Introduction.......................................................................................................... |
34 |
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4.2 |
Hammer Impact Sensing Testing ......................................................................... |
34 |
4.2.1 Hammer Impact Sensing Setup .................................................................... |
35 |
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4.2.2 Hammer Impact Sensing Results .................................................................. |
38 |
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4.3 |
Free Vibration Sensing Testing............................................................................ |
43 |
4.3.1 Free Vibration Sensing Setup ....................................................................... |
43 |
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4.3.2 Free Vibration Sensing Results..................................................................... |
44 |
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4.4 |
Load Frame Sensing Testing ............................................................................... |
48 |
4.4.1 Load Frame Sensing Setup .......................................................................... |
48 |
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4.4.2 Load Frame Sensing Results ........................................................................ |
49 |
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4.5 |
Sensor Performance Assessment and Comparison............................................. |
50 |
Chapter 5: Actuation and Guided Wave Testing ............................................................ |
51 |
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5.1 Introduction.......................................................................................................... |
51 |
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5.2 |
Piezoelectric Guided Wave Methodology............................................................. |
51 |
5.3 |
Piezopolymer Actuators ....................................................................................... |
56 |
5.4 |
Actuator Fabrication and Characteristics ............................................................. |
59 |
5.4.1 Piezopolymer Actuator Design ...................................................................... |
59 |
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5.4.2 Piezopolymer Actuator Fabrication ............................................................... |
61 |
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5.5 |
Pitch-Catch Active Sensing Experimental Setup .................................................. |
65 |
5.6 |
Active Sensing Results and Discussions ............................................................. |
69 |
5.6.1 Pitch-Catch Results, Time-Domain Response .............................................. |
69 |
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5.6.2 Damage Detection ........................................................................................ |
70 |
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5.7 |
Actuator Performance Assessment and Comparison ........................................... |
74 |
Chapter 6: Conclusions ................................................................................................. |
76 |
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vi |
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Appendix A: Works Cited............................................................................................... |
78 |
vii
List of Figures
Figure 1: Piezoelectric Effect Schematic |
9 |
Figure 2: Material Classification Breakdown |
11 |
Figure 3: Fabrication Flowchart |
23 |
Figure 4: SEM Images of Films |
25 |
Figure 5: Ferroelectric Setup |
28 |
Figure 6: Hysteresis Output, Increasing Voltage |
29 |
Figure 7: Hysteresis Output, Changing ZnO Content |
30 |
Figure 8: Hammer Validation Setup |
36 |
Figure 9: Hammer Impact Time Results |
38 |
Figure 10: Relative Maximum Voltage Response by ZnO wt.% |
39 |
Figure 11: Maximum Voltage Compared with Impact Energy |
41 |
Figure 12: Maximum Voltage Compared with Impact Distance |
42 |
Figure 13: Free Vibration Setup |
44 |
Figure 14: Free Vibration: Dynamic Strain Time Response |
45 |
Figure 15: Free Vibration: Voltage Response vs. Dynamic Strain |
47 |
Figure 16: TestResources Load Frame |
48 |
Figure 17: Load Frame: Voltage Response vs. Dynamic Strain |
50 |
Figure 18: Guided Wave Propagation |
54 |
Figure 19: Fingered Electrodes: Comb and IDT |
57 |
Figure 20: Fringing Field Effect |
58 |
Figure 21: Actuator Construction |
61 |
Figure 22: Photolithography |
63 |
Figure 23: Final Actuator Product |
64 |
Figure 24: Pitch-Catch Physical Setup |
66 |
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Figure 25: Voltage Impulse on the PVDF-TrFE/ZnO Actuator |
67 |
Figure 26: Non-Permanent Damage |
68 |
Figure 27: Typical Time-Domain Pitch-Catch Result |
69 |
Figure 28: Aluminum Pipe Pitch-Catch Results: Pristine vs. Damaged |
71 |
Figure 29: Pitch-Catch on Pipe: Difference Comparison |
72 |
ix
List of Tables |
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Table 1: Remnant Polarization, Changing ZnO Content ................................................ |
32 |
Table 2: Maximum Voltages for Pristine and Damaged Specimens ............................... |
74 |
x