【作者】 乔海霞；

【导师】 曾竟成；

【作者基本信息】 国防科学技术大学 ， 材料科学与工程， 2006， 硕士

【摘要】 本文研究了实验室模拟环境(湿热、化学介质、盐雾、紫外光)下,玻璃纤维/碳纤维混杂增强环氧树脂复合材料电缆芯的环境老化行为,测定了复合材料电缆芯在多种化学介质中的吸湿特性,分析了环境因素对其静态、动态力学性能的影响以及该复合材料在不同介质中的老化机理,并基于湿热老化对复合材料电缆芯进行了寿命预估。通过测量吸湿率研究了复合材料电缆芯在不同介质中的吸湿特性。结果表明,在蒸馏水和10wt% NaCl水溶液中,复合材料电缆芯在吸湿初期符合Fick扩散定律,吸湿后期偏离了Fick扩散定律;在10wt% H2SO4水溶液中,浸泡前期复合材料电缆芯的吸湿与Fick扩散相似,但后期表观吸水率稍有下降;在5wt% NaOH水溶液中,复合材料电缆芯的表观吸水率先线性增加,而后略有下降,最后又随浸泡时间的增加而单调增加;另外,升高温度加快了水在复合材料电缆芯中的扩散速率,增大了复合材料电缆芯的饱和吸水率。通过动态机械热分析(DMA)考察了湿热老化对复合材料电缆芯动态力学性能的影响。结果表明,复合材料电缆芯的储能模量( )随老化时间的推移而下降,力学损耗因子(taE’nδ)随老化时间的推移而增大,且温度越高影响越大;水的增塑作用使复合材料电缆芯的玻璃化转变温度(Tg)下降,且随吸湿达到饱和,Tg趋于一定值;由未吸湿试样和吸湿后又重新干燥试样的DMA结果得知,复合材料电缆芯在湿热老化过程中未发生明显的水解反应。采用万能试验机测定了复合材料电缆芯的弯曲强度和剪切强度,考察了环境条件对其静态力学的影响。结果表明,环境条件造成了复合材料电缆芯弯曲、剪切强度的下降,但性能降低的幅度逐渐减小;在不同温度下,复合材料电缆芯的力学性能下降趋势基本相同,只是性能下降的速率和幅度不同,温度高的下降快幅度大。扫描电镜(SEM)和红外光谱(IR)分析结果表明,在蒸馏水和10wt% NaCl水溶液中复合材料电缆芯有着相同的老化机理,即复合材料的性能变化是由树脂基体的溶胀塑化、界面脱粘及基体、界面的形貌变化引起的,未发生化学反应;而在10wt% H2SO4和5wt% NaOH水溶液中,除上述物理老化外,复合材料还发生了化学老化。基于加速湿热老化,采用B基值方程得到了混杂复合材料电缆芯加速老化的高置信度、高可靠度寿命预测方程及相关参数,确定了环境当量,预测了混杂复合材料电缆芯的工作寿命。更多还原

【Abstract】 Aging behaviors of glass/carbon hybrid fibers reinforced epoxy resin composite cable core were studied in various simulated environments respectively. Absorption characteristics of the composites in distilled water, 10wt% NaCl aqueous solution, 10wt% H2SO4 aqueous solution and 5wt% NaOH aqueous solution were investigated. Moreover, effects of the environments on static and dynamic mechanical properties and aging mechanisms were analyzed. The service life of the cable core was also predicted on the basis of experimental hygrothermal aging data.The experimental results of moisture absorption ratio show that the absorption characteristics of the hybrid composite cable core obey the Fick’s law in the early period, however, large deviations arise for the cable core in distilled water and 10wt% NaCl aqueous solution in the following time of the experiment. In 10wt% H2SO4 aqueous solution, the absorption behavior agrees with the Fick’s law at the early stage, while the nominal moisture content decreases a little at the later stage. The moisture content of the cable core in 5wt% NaOH aqueous solution increases linearly at first and thereafter decreases, and then increases with the prolongation of immersion time. Moreover, the increase of environmental temperature leads to a faster diffusion of water in the composites and a higher equilibrium moisture content.Effects of the hygrothermal aging on the dynamic mechanical properties of the hybrid composite cable core were studied by dynamic mechanical analysis (DMA). The results show that the storage modulus ( ) of the composites decreases with increasing immersion time, while the loss factor (tanE’δ) increases simultaneously. Furthermore, the higher the temperature the more remarkable the effects. The glass transition temperature (Tg) of the composite is relative to the moisture content.The flexural and shear properties of the hybrid composite cable core were measured on an universal testing instrument to study effects of the environments on the static mechanical properties of the composites. Results indicate that environmental aging results in the decrease in the flexural and shear properties of the hybrid composite cable core. The decrease amplitude minishs gradually. Under different temperatures, the decrease of mechanical properties of the composites was uniform, and higher temperature accelerates the composites aging.Results of infrared spectrometer (IR) and scanning electron microscope (SEM) show that the composites in distilled water and 10wt% NaCl aqueous solution have the same aging mechanisms, which consists of the swelling and plasticization of matrix, interfacial debonding and resultant microstructure changes of matrix and interface. No chemical reactions can be observed. While in 10wt% H2SO4 aqueous solution and 5wt% NaOH aqueous solution, chemical aging is found.Based on accelerated hygrothermal aging test of the hybrid composite cable core, a service-life prediction equation for the composite cable core with high confidence and reliability was developed in the paper. Furthermore, the service life of the cable core was estimated according to the environment equivalence.更多还原