T700碳纤维增强环氧树脂基复合材料自然老化性能与机制

为验证复合材料的耐久性，对T700碳纤维增强环氧树脂基复合材料经自然老化后的微观形貌、表面元素含量、热性能与力学性能等进行了研究。结果表明: 在光氧老化与热氧老化的共同作用下，T700碳纤维增强EP-A环氧树脂基（T700/EP-A）复合材料表层树脂将发生老化降解，并且随自然老化时间的延长，T700/EP-A复合材料的玻璃化转变温度逐渐降低，未老化试样的玻璃化转变温度为207℃，经过自然老化处理3年后，其玻璃化转变温度降低为180℃，延长自然老化时间至5年时，其玻璃化转变温度进一步降低至172℃。而自然老化过程对复合材料力学性能可能同时存在着增强效应与损伤效应，因此造成了T700/EP-A与T700/EP-B复合材料的不同力学性能表现出相异的变化趋势。随自然老化时间延长，T700/EP-A与T700/EP-B复合材料纵向拉伸强度表现出先升高后降低的趋势，纵向弯曲强度表现出逐渐升高的趋势，纵向压缩强度与层间剪切强度存在波动，未呈现出明显变化。 

Environmental aging performance and mechanism of T700 carbon fiber reinforced epoxy resin matrix composites

In order to verify the durability of composites,the microscopic morphology,surface element content, thermal properties and mechanical properties of T700 carbon fiber reinforced epoxy resin matrix composites were studied after environmental aging.The results show that the coaction of photo-oxidative degradation and thermo-ox-idative degradation cause the T700 carbon fiber reinforced EP-A epoxy resin matrix (T700/EP-A)composites sur-face resin aging degradation.With the extension of environmental aging time,the glass transition temperature of T700/EP-A composites decreases gradually.After 3 years of environmental aging treatment,glass transition tem-perature of T700/EP-A composites decreases from 207 ℃(un-aged specimen)to 180 ℃,and to 172 ℃ after exten-ding environmental aging of 5 years.Enhancing effects and damaging effects of the environmental aging process may coexist in the mechanical properties of the composites,thus resulting in different mechanical properties of T700/EP-A and T700/EP-B composites showing disparate trends.With the extension of environmental aging time,the longi-tudinal tensile strength of T700/EP-A and T700/EP-B composites first increases then decreases,the longitudinal flexural strength gradually increases,fluctuant longitudinal compress strength and interlaminar shear strength show no significant variation tendency.