CFRP复合材料电热损伤的电学表征方法研究

发布时间：2018-07-04 12:37

  本文选题：碳纤维 + 复合材料　； 参考：《中国民航大学》2017年硕士论文

【摘要】：本文研究了两种航空碳纤维增强树脂基复合材料(Carbon Fiber Reinforced Polymer,简称CFRP)的电热作用机理及相关的电学表征方法。通过温度场、纵向体积电阻以及介电性能测试分析了CFRP的电热特性,完成了电热损伤特征参量的提取。采用傅里叶变换红外光谱仪(FT-IR)和差示扫描量热仪(DSC)研究了电热作用前后CFRP中环氧树脂基体的物理及化学变化。深入探讨了电热作用前后CFRP的静态力学性能以及动态力学性能变化规律。利用激光共焦显微镜和扫描电镜分别观察了电热作用前后的CFRP的表面形貌和断口形貌,分析其失效特征并总结了电热损伤机理。电热特性研究结果表明,电热作用下T300/E52和T300/970两种复合材料的温度场随时间均呈现先迅速上升后稳态平衡趋势。对于T300/E52复合材料,电流密度小于0.125A·mm-2的电热作用使其表面温度场分布均匀,纵向体积电阻降低以及介电性能提升;大于0.125A·mm-2的电热作用在中间区域形成较高温度场,纵向体积电阻升高以及介电性能下降。介电频谱测试表明,介电常数和损耗角正切值随测试频率增加而降低,AC电导率随频率增加先恒定后迅速上升。对T300/970复合材料,玻璃化转变温度附近的电热作用(电流密度范围为0.25~0.31A·mm-2)基本上使其导电性能下降,介电性能提升。损耗角正切值由于对基体、界面损伤较为敏感,且电热作用对其影响较大,可作为特征参量。电热作用后T300/970复合材料的FT-IR图谱中没有出现明显的新峰,羟基峰整体上在增强,这与环氧树脂发生后固化有关。羰基峰的略微增强表明环氧树脂发生了氧化反应。电热作用后复合材料的DSC曲线表明,环氧树脂的玻璃化转变温度明显上升,这也说明环氧树脂发生后固化反应。电热作用后T300/970复合材料的动态力学分析发现,试样的玻璃化转变温度最大上升25℃,储能模量也有明显提升,说明电热作用不仅使复合材料发生后固化,还对其有物理老化效果。三点弯测试表明,低于0.125A·mm-2的电热累积作用使T300/E52复合材料的弯曲强度和弯曲模量最大分别提升11.8%和7.32%;高于0.125A·mm-2时,弯曲强度和弯曲模量最大降低8.26%和6.52%。对于T300/970复合材料,8~9A的电热作用对其造成微损伤,使其弯曲性能最大降低13%;9.5~10A电热作用下,后固化和物理老化速率加快,使试样的弯曲性能有一定回升。表面形貌观测发现,电热作用使T300/970复合材料发生层间基体微开裂,这主要是由纤维和基体的热膨胀系数不匹配,在试样中产生的残余热应力导致的。断口形貌分析表明,电热作用使试样断口粗糙,分层明显,纤维/基体界面粘结性能恶化,引起界面微开裂,并且界面损伤的出现要早于基体微开裂损伤。
[Abstract]:In this paper, the electrothermal mechanism of two kinds of aeronautical carbon fiber reinforced polymer (CFRP) composites and their electrical characterization methods are studied. The electrothermal properties of CFRP were analyzed by temperature field, longitudinal volume resistance and dielectric properties, and the characteristic parameters of electrothermal damage were extracted. The physical and chemical changes of epoxy resin matrix in CFRP before and after electrothermal treatment were studied by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimeter (DSC). The static and dynamic mechanical properties of CFRP before and after electrothermal action were discussed. The surface morphology and fracture morphology of CFRP before and after electrothermal action were observed by laser confocal microscope and scanning electron microscope respectively. The failure characteristics of CFRP were analyzed and the mechanism of electrothermal damage was summarized. The results of electrothermal properties show that the temperature field of T300 / E52 and T300 / 970 composites increases rapidly with time and then shows a steady equilibrium trend. For the T300 / E52 composite, the electrothermal effect of current density less than 0.125A mm-2 makes the surface temperature field uniform, the longitudinal volume resistance decreases, and the dielectric property is improved, and the electrothermal action greater than 0.125A mm-2 forms a higher temperature field in the middle region. The longitudinal volume resistance increases and the dielectric property decreases. The dielectric constant and the tangent value of loss angle decrease with the increase of the frequency, and the conductivity of AC decreases with the increase of the frequency, and then increases rapidly. For T300 / 970 composites, the electrothermal action near the glass transition temperature (current density range of 0.25 ~ 0.31A mm-2) makes the electrical conductivity decrease and the dielectric property increase. The tangent value of loss angle is sensitive to the matrix, and the electrothermal effect is great, so it can be used as the characteristic parameter. The FT-IR spectra of T300 / 970 composites after electrothermal treatment showed no obvious new peaks, but the hydroxyl peaks were strengthened as a whole, which was related to the curing of epoxy resin. The slight enhancement of the carbonyl peak indicates that the epoxy resin is oxidized. The DSC curves of the composites show that the glass transition temperature of epoxy resin increases obviously, which also indicates the curing reaction of epoxy resin. The dynamic mechanical analysis of the T300 / 970 composite after electrothermal treatment showed that the glass transition temperature of the sample increased by 25 鈩，

本文编号：2096105