碳纤维增强碳基复合材料的介电性能对应力的自感知

Self-Sensing Behavior of Carbon Fiber Reinforced Carbon Matrix Composite Based on Dielectric Behavior

碳纤维增强碳基复合材料(C/C)具有优异的力学和导电性能,但其介电性能的报道较为罕见。文中采用LCR测量仪测量C/C的相对介电常数,采用电流源和纳伏表通过四电极法测量C/C的电阻率,研究了C/C的相对介电常数和电阻率随压应变的变化规律。研究表明,单位应变下相对介电常数的变化率(528±8)是电阻率变化率(111±5)的4.7倍,说明C/C复合材料的介电性能对其微观结构的改变更敏感。此外,压应变下C/C介电性能的增强归因于应变诱导的微缺陷提供了部分电子和空穴参与空间电荷极化的场所,以及压应变改善了极化连续性。单位压应变下增加的参与极化的电子或空穴的数量为(1.37±0.02)×10^(10)。C/C的相对介电常数低于碳纤维和石墨,可归因于碳基体中较高的孔隙率及较多的界面。

Carbon fiber reinforced carbon matrix composites(C/C)are popular due to their excellent mechanical and conductive properties,while their dielectric behavior has received little attention.The LCR meter was used to measure the relative permittivity of C/C.The resistivity was measured by current source and nano-voltage meter combined with four-probe method.The results show that the fractional change in relative permittivity per unit strain is 528±8,which is 375%higher than the fractional change in resistivity per unit strain,indicating that the dielectric behavior is more sensitive to changes in microstructures.In addition,the enhancement of dielectric behavior of C/C is due to compressive strain inducing micro defects,such as grain boundaries,interfaces,etc.,that provide sites for space polarization involving a fraction of electrons and holes;on the other hand,the polarization continuity of C/C is enhanced by compression.The increase in the number of electrons and holes that participate in polarization per unit compressive strain is(1.37±0.02)×10^(10).The relative permittivity of C/C is lower than both carbon fiber and graphite due to high porosity and interfaces.