Electret behavior of carbon fiber structural composites with carbon and polymer matrices, and its application in self-sensing and self-powering

摘要

Continuous carbon fiber carbon-matrix (C/C) and polymer-matrix (CFRP) structural composites without poling are electrets. Their DC electric field E (hence the volumetric power density P-v for structural self-powering) increases linearly with increasing inter-electrode distance l (more significantly for C/C). Shortcircuit discharge and open-circuit self-charge occur reversibly. The fraction of carriers that participate is 1.6 x 10(-3) and 2.8 x 10(-3) for CFRP and C/C, respectively. At l = 140 mm, E = 1.2 x 10(-4) V/m, and Pv is 5.0 x 10(-5) and 2.5 x 10(-4) W/m(3) for CFRP and C/C, respectively. The participating carrier density is 2.4 x 10(21) and 2.6 x 10(22) m(-3), and the discharge time per unit participating charge is 6.7 x 10(6) and 8.9 x 10(4) s/C for CFRP and C/C, respectively. The C/C gives higher power density, whereas CFRP discharges more slowly. The polarization-induced apparent resistance increase upon DC current polarity reversal is asymmetrical. Elastic tension affects E, relative permittivity kappa and resistivity rho essentially reversibly and linearly (more significantly for C/C), enabling piezoelectret/piezoresistive self-sensing and piezoelectretbased energy harvesting. The strain causes CFRP to increase in E, kappa and rho, and C/C to decrease in E and rho and increase in kappa. Increasing the temperature from 20 -degrees C to 70 - degrees C increases E reversibly by 1900% and increases the volumetric power density by 40000%, as shown for C/C. (C) 2020 Elsevier Ltd. All rights reserved.