单向CF/PA6复合材料性能劣化及老化寿命预测

Property degradation and life prediction of unidirectional CF/PA6 composites

利用热压成型工艺制备出碳纤维(CF)/尼龙6(PA6)复合材料单向板,并将复合材料试样置于蒸馏水热水浴中,分别在25,60,80℃下进行不同时间的湿热老化,再对湿热老化后复合材料试样进行吸湿测试、三点弯曲测试、微观形貌表征,探究复合材料的吸湿规律、力学性能劣化规律和微观形貌变化,并对复合材料的长期寿命进行预测。结果发现,复合材料在25,60℃下的吸湿行为基本符合Fick扩散定律,而80℃下在老化最后阶段出现了背离Fick扩散定律现象。复合材料的弯曲强度随老化温度、老化时间的增加呈下降趋势,分别在25,60,80℃下老化120 d后,试样弯曲强度分别下降了22.78%,25.0%,26.25%。但是老化温度、老化时间对弯曲弹性模量无显著影响,且CF与PA6树脂之间的界面黏合性能随着温度、时间的增加逐渐变差。以绍兴2021年平均温度作为服役温度,基于加速老化测试模型和阿伦尼乌斯理论建立了CF/PA6复合材料在服役环境下剩余弯曲强度的预测模型,可预测到1 400 d后,CF/PA6复合材料的弯曲强度保留率在64.8%左右。

Unidirectional CF/PA6 composite plates were fabricated by the hot-compression molding technique,and the composite specimens were immersed in distilled water bath at 25,60,80 ℃ for different hydrothermal aging periods,then moisture absorption test,three-point bending test,microscopic morphology characterization were carried out to investigate the moisture absorption behavior,degradation of mechanical properties,and microscopic morphological changes.Furthermore,the long-term life of composite specimens was predicted.The results show that the moisture absorption behavior of the composites at 25 and 60 ℃ is basically consistent with Fick's diffusion law,while the deviation from the Fick's diffusion law occurs at the last stage of aging at 80 ℃.The flexural strength of composites decreases with the increase of aging temperature and aging time,after 120 days of aging at temperatures of 25,60,80 ℃,the flexural strength of the samples decreases by 22.78%,25.0%,26.25% respectively.However,the aging temperature and aging time have no significant impact on the flexural modulus,and the interfacial bonding strength between carbon fiber and resin gradually deteriorates with the increase of temperature and time.This experiment takes the average temperature in Shaoxing in 2021 as the service temperature.Based on the accelerated aging test model and the Arrhenius theory,a predictive model for the residual bending strength of CF/PA6 composite materials in service environment was established.It can be predicted that after 1 400 days,the bending strength retention rate of CF/PA6 composites will be around 64.8%.