温度对玻璃纤维/环氧复合材料吸湿扩散行为的影响

Effects of temperature on moisture absorption and diffusion behavior of glass fiber/epoxy composites

为研究温度对复合材料吸湿扩散行为的影响,开展单向玻璃纤维/环氧复合材料板在35℃、50℃、70℃下的吸湿实验,并用DMA分析复合材料的储能模量和玻璃化转变温度(T_(g))变化,用FTIR分析复合材料官能团变化。结果表明:温度为35℃和50℃时,复合材料的吸湿扩散行为可用Fick模型描述,采用Fick三维公式可拟合得到复合材料的三维扩散系数。温度为70℃时,复合材料的吸湿扩散行为可用Fick-松弛耦合模型描述。饱和吸湿复合材料的T_(g)随吸湿实验温度的升高而增大,在70℃时复合材料出现降解和物理老化,导致质量损失。不同吸湿实验温度下复合材料在垂直于纤维方向的扩散系数满足Arrhenius方程,活化能为78.15 kJ·K^(-1)·mol^(-1)。沿纤维方向的扩散系数在温度为70℃时显著增大,其原因是高温显著增强了水分在纤维/基体界面沿该方向的扩散性能。

In order to investigate the effects of temperature on the moisture absorption and diffusion behavior of composites,the moisture absorption tests for unidirectional glass fiber/epoxy composites under 35℃、50℃ and 70℃ were carried out.The storage modulus and glass transition temperature(T_(g))of composites were studied by DMA,and functional group changes were study by FTIR.The results show that when the temperature is 35℃and 50℃,the moisture absorption and diffusion behavior of the composite can be described by Fick model,and the three-dimensional diffusion coefficient of the composite can be fitted by Fick formula.When the temperature is 70℃,the moisture absorption and diffusion behavior of the composite can be described by Fick-relaxation coupled model.T_(g) of saturated composites increases with the increase of moisture absorption test temperature,and degradation and physical aging of the composites occur when the temperature is 70℃,resulting in mass loss.The moisture diffusion coefficients of the composites perpendicular to the fiber direction at different moisture absorption test temperatures satisfy the Arrhenius equation,and the activation energy is 78.15 kJ·K^(-1)·mol^(-1).The diffusion coefficient along the fiber direction increases significantly at the moisture absorption test temperature of 70℃.The reason is that the high temperature significantly enhances the water diffusion in the fiber/matrix interface along fiber direction.