三维角联锁复合材料弯曲性能的热老化特征

研究了三维角联锁碳纤维复合材料未老化及90℃、110℃、180℃老化16 d的弯曲力学性能。对比三维角联锁复合材料弯曲-挠度曲线、破坏形态及SEM纤维特征,分析老化温度对复合材料弯曲性能的影响。通过环氧树脂DSC分析、红外光谱分析说明老化温度对树脂热学性质、后固化现象及分子结构变化的影响。结果表明:环氧树脂老化过程存在后固化和热降解两种竞争机制,90℃老化16 d的复合材料后固化作用突出,与未老化复合材料相比其弯曲强度增大;110℃老化16 d的复合材料热降解作用占优势,材料起始破坏弯曲强度略有下降;上述两者弯曲模量基本不变,而180℃老化16 d的复合材料热降解剧烈,树脂与纤维之间严重脱粘,材料弯曲强度明显下降,弯曲模量减小。

CHARACTERISTICS OF THERMAL AGING ON BENDING PROPERTIES OF 3-D INTERLOCK COMPOSITE MATERIAL

In this paper,the bending properties of 3-D carbon/epoxy interlock composite unaged and aged for 16-days at different temperature (90 ℃,110 ℃,180 ℃) were studied by quasi-static loading.The influences of aging temperature on bending properties were observed by macroscopic observation and SEM as well.The influences of aging temperature on epoxy properties,post-curing,heat flow and chemical structure were studied by differential scanning calorimetry (DSC) and infrared spectrum (IR Spectrum),respectively.The result indicated as follows.The post-curing and thermal degradation can be found in epoxy aging at the same time.For Composite aged for 16 days,the bending strength of composite aged at 90 ℃ increased obviously because the post-curing of epoxy play an important role in aging.When composite aged at 110 ℃,the bending strength decreased unobviously which were caused by slightly thermal degradation.For composite aged at 180 ℃,the bending strength declined distinctly and the flexural modulus decreased as well due to the strong thermal degradation of the epoxy resin and the fiber/resin interface crack which were observed by SEM.In addition,less damage area on top of composite aged at 90 ℃ than others could be found form the damage photographs.These were consistent with the strength characteristics which indicated in above situation that composite aged at 90 ℃ had better bending properties.