基于介电性能研究碳纤维/环氧复合材料单向板电热作用机制

采用复合材料电热试验机对碳纤维/环氧复合材料(CF/EP)单向板进行0.05~0.2A·mm~(-2)直流电流通电处理,每次通电1.5h,同时对其电热作用下的表面温度场进行测量;分析电热作用后CF/EP试样的纵向体积电阻和介电性能变化;通过三点弯曲测试表征电热作用前后的弯曲性能。结果表明:试样的温度场随通电时间均呈现先迅速上升后稳态平衡的趋势。低于0.125A·mm~(-2)的电热作用使温度场分布均匀,纵向体积电阻降低以及介电性能提升;高于0.125A·mm~(-2)的电热作用使中间区域温度场高于两边区域,纵向体积电阻上升以及介电性能下降。介电常数和损耗角正切随测试频率增大而降低,交流电导率随频率增大先稳定后上升。受电热作用影响最大的损耗角正切可作为特征参量。弯曲性能测试表明,低于0.125A·mm~(-2)的电热作用使CF/EP试样的弯曲强度和弯曲模量最大提升11.8%和7.32%,而高于0.125A·mm~(-2)的电热作用使试样的弯曲强度和弯曲模量最大降低8.26%和6.52%。

Electro-thermal influencing mechanism of carbon fiber/epoxy unidirectional laminated composites based on dielectric properties

Direct currents(DC)ranged from 0.05 A·mm-2 to 0.2 A·mm-2 were subjected through carbon fiber/epoxy(CF/EP)unidirectional composites with a 1.5 h duration by the electro-thermal tester,meanwhile the tem-perature fields were measured on the surface of samples under different electro-thermal treatments.Changes in the longitudinal volume resistance and dielectric properties were analyzed respectively after electro-thermal treatments. In order to characterize the flexural property,the three-point flexure test was conducted before and after electro-thermal treatments.Preliminary experimental results show that temperature fields of all samples are rising rapidly with the duration before steady-state equilibrium.Treatments at less than 0.125 A · mm-2 lead to a uniform temperature field,and make the longitudinal volume resistance decrease and enhance dielectric properties.Treatments at more than 0.1 2 5 A · mm-2 come to a contrary result.The dielectric constant and loss tangent increase with the increment of test frequency,whereas the AC conductivity remains unchanged and then rises.The loss tangent affected mostly by electro-thermal treatments can be used as characteristic parameter of electro-thermal influence.The flexural property test demonstrates that treatments less than 0.125 A·mm-2 make flexural strength and modulus increase by 11.8% and 7.32% mostly,but they reduce by 8.26% and 6.52% maximally after treating more than 0.125 A·mm-2 .