环氧树脂胶的太赫兹光谱特性研究

Terahertz Spectroscopic Study on the Property of Epoxy Resin Adhesive

环氧树脂是纤维增强复合材料加工中的一种重要的胶粘剂,太赫兹时域光谱技术已成为纤维增强复合材料无损检测的有力补充手段。固化温度是环氧树脂的重要参数之一,不同的固化温度会影响环氧树脂胶的性能,因此采用太赫兹时域光谱技术分别对室温和高温下固化的环氧树脂胶的太赫兹透射光谱特性进行了系统研究,计算得到了不同温度下固化的环氧树脂胶的折射率和吸收系数,并进行了对比分析。研究表明,由于室温下固化的环氧树脂样本基本没有气泡,而高温下固化的样本存在微量气泡,气泡的存在降低了样品的密度,因此室温下固化的环氧树脂胶样品的折射率和吸收系数均大于高温下固化的样品。在同种固化条件下制备的不同样品间折射率差别较小,同时,室温下固化不同样品间的吸收系数差别亦较小,但高温下固化样品间的吸收系数在0.6～1.5THz差别逐渐变大,这主要是因为高温下制备的不同样本间的气泡分布不均匀,即密度分布存在差异。室温和高温下固化样品的吸收系数在整体上均随着频率的增加而增加,并且没有明显的吸收峰。此外,由于法布里-珀罗干涉效应的存在,导致有些厚环氧树脂样本的能量透过率在共振峰处要远大于薄样本。该研究对纤维增强复合材料的太赫兹无损检测具有重要的研究意义。

Epoxy resin is an important adhesive applied in the manufacturing processes of fiber reinforced polymer（FRP）composites.Terahertz（THz）time-domain spectroscopy（TDS）technology is an effective supplementary method for nondestructive evaluation（NDE）of FRP composites.As one of the most important parameters for epoxy resin,different curing temperature can affect the properties of epoxy resin.In this paper,we carry out systematic investigations on THz transmission properties of epoxy resin cured respectively under room temperature and high temperature with THz TDS technology.At the same time,the authors extract the refractive indices and absorption coefficients of epoxy resin,and make comparisons d.As shown in the experiments,the epoxy resin samples cured under room temperature have no bubble,whereas there are some micro-bubbles in the samples cured under high temperature,which reduce the sample density.Hence,the refractive index and absorption coefficient of epoxy resin cured under room temperature are both greater than those cured under high temperature.The difference of refractive index of different samples cured under the same condition is not significant.In addition,the difference of absorption coefficient of different samples cured under room temperature is also slight.However,the difference of absorption coefficient of different samples cured under high temperature gradually increase within the frequency from 0.6to 1.5THz,which is mainly due to the heterogeneous distribution of the bubbles in the different samples cured under high temperature.Moreover,the absorption coefficient of epoxy resin prepared under both curing temperatures gradually increases with the frequency,and there is no obvious absorption peak.Finally,because of the existence of Fabry-Pérot interference,the power transmission ratio of thicker epoxy resin samples may be greater than thinner samples at the resonant frequency.This research is of great significance for the THz NDE of FRP composites.