Center for Composite Materials - University of Delaware

Research Summary

Challenges in Nano-Composite Piezoelectric Composites

Authors: Cedric Jacob (PhD Candidate), Erik Thostenson

INTRODUCTION

• The goal is to build a multi-scale piezoelectric polymer-polymer composite which is reinforced by carbon nanotubes.
• The carbon nanotubes selectively alter the electrical potential topography and selectively areas of higher electric field
• The piezoelectric effect means that strain is linearly related to electric field so this will produce larger net strains.

THE PROCESS

• Electrospinning is used to generate multiple phases of sub micron fibers, some of which are reinforced with carbon nanotubes
• Consolidation is done by either re-infusing or re-dissolving the electrospun matrix.
• Electrodes are placed by sputter-coating the films after the poling process has completed.

CRYSTAL STRUCTURE

• The crystal structure is determined using wide-angle x-ray diffraction (WAXRD)
• Diffraction patterns are integrated and peaks represent differing crystal structures

SAMPLE REQUIREMENTS

• The crystal structure of the polymorphic polymer has to be of the right type.
• The dielectric breakdown strength of the composite has to be high enough to support electrical poling
• The ratio of sample size to active area has to be large enough to prevent electrical tracking
• The electrodes must be engineered to prevent corona discharge

POLING

1. Corona discharge occurs without any sample interaction. The arc forms through the air.
2. Electrical tracking occurs across the surface of the sample.
3. Dielectric breakdown occurs when the electric field is strong enough to break through the composite.

ELECTRODES AND MEASUREMENTS

Experimental technique for measuring electrical tracking, dielectric breakdown, and corona discharge
• Modular test-stand
• Measure current, voltage, separation distance

CONCLUSIONS AND FUTURE WORK

• Ability to create the proper crystal structure has been shown.
• Studying of the dielectric breakdown strength, electrical tracking, and corona discharge is in progress

ACKNOWLEDGEMENTS

• David Young (Electrical Engineering)
• Bruker-AXS
• University of Delaware Fellows Program
Research is partially funded by the Air Force Office of Scientific Research (AFOSR) Young Investigator Grant (FA9550-09-1-0218), Dr. Byung-Lip Lee, Program Director

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