电热处理对湿热环境作用下碳纤维环氧复合材料的损伤机制

Damage Mechanism of Electrothermal Treatment on Carbon Fiber Epoxy Composites under Hygrothermal Environment

对T300/E51复合材料进行电热处理、湿热老化以及电热吸湿处理,从弯曲性能、吸湿率、基体化学结构、玻璃化转变温度、弯曲断口等方面揭示电热处理对湿热老化的影响机制。研究结果表明:原始试样经湿热处理后发生部分水解,4 A电热+湿热处理试样的后固化比较明显,6 A电热+湿热处理试样没有发生明显的变化。后固化作用引起的界面裂纹尺寸减小导致4 A电热试样的吸湿率下降;玻璃化转变温度的变化规律与弯曲性能的变化规律类似。详细的分析表明,T300/E51复合材料经电热处理后其损伤机制与传统的吸湿损伤机制有所不同,玻璃化转变温度代替吸湿率成为衡量复合材料性能变化的重要因素。微观结构分析显示电热处理产生的温度梯度和压缩应力使得基体微裂纹增多,再经湿热处理后,溶胀广泛存在于整个基体中,进而导致弯曲性能降低。

The T300/E51 composites are treated by electrothermal treatment, hygrothermal ageing and electrothermal moisture treatment. The effect of electrothermal treatment on the hygrothermal ageing is revealed from bending properties, moisture absorption rate, chemical structure of the matrix, glass transition temperature, bending fracture and etc. The results show that the original sample is hydrolyzed partially after the hydrothermal treatment, and the samples processed with 4 A electro-thermal and hydrothermal treatment have an obvious postcure effect, while there is no significant change in the samples after 6 A electro-thermal and hydrothermal treatment. The moisture absorption rate of 4 A heated sample is decreased due to the decrease of the size of interface cracks caused by postcure effect. The variation of glass transition temperature is similar to that of bending behavior. The detailed analysis reveals that, the damage mechanism of T300/E51 composites after electrothermal treatment is different from that of traditional moisture. The glass transition temperature becomes a primary factor to measure the performance of composite materials, instead of moisture absorption. Microstructure observations show that the micro-cracks are increased owing to the temperature gradient and compressive stress generated by the effect of electrothermal treatment. Additionally, the swelling occurs throughout the matrix after the subsequent hydrothermal treatment, which eventually leads to the decrease of the bending property.