Effect of Curing State on Time-Temperature Dependence of Mechanical Properties for Epoxy Composites

在研究中，我们研究了固化状态对双酚A型环氧树脂和二氧化硅颗粒填充环氧复合材料长时间、宽温度范围内力学性能的影响。样品为双酚A型环氧树脂，在多种温度和时间组合下固化。玻璃化转变温度和脆性由热粘弹性的结果得出。拉曼光谱分析表明，玻璃化转变温度与环氧树脂的交联度反应有直接关系。当玻璃化转变温度达到饱和时，表征非均相组织的脆性降低。测定了不同环氧树脂的弹性模量和室温断裂韧性。在饱和玻璃化转变温度下，环氧树脂的弹性模量近似恒定。断裂韧性与固化条件密切相关。当玻璃化转变温度在400 K左右达到饱和时，环氧树脂的脆性降低。对熔融二氧化硅颗粒填充双酚A型环氧树脂进行了类似的实验。结果表明，高玻璃化转变温度和低脆性提高了复合材料的断裂韧性。因此，证实了玻璃化转变温度和脆性是评价环氧树脂及其复合材料力学性能的有效参数。测定了环氧树脂和硅颗粒填充环氧复合材料断裂韧性的时间-温度关系。断裂韧性遵循由热粘弹性特性决定的时间-温度等效原理。当玻璃化转变温度约为400 K时，脆性较小的材料的断裂韧性比脆性较大的材料的断裂韧性在较低温度到脆-韧转变温度时有所增加。最后，基于断裂韧性的时间-温度依赖关系，对含裂纹圆柱体的断裂进行了数学预测。在发现玻璃化转变温度和脆性是评价环氧树脂及其复合材料力学性能的重要参数的基础上，提出了这两个参数作为环氧树脂及其复合材料固化条件的设定参数。少

In the research, we studied effect of curing state on mechanical properties of bisphenol A type epoxy resin and silica particulate-filled epoxy composite for long time and wide temperature ranges.Specimens were bisphenol A type epoxy resin cured under several combinations of temperature and time. Glass transition temperatures and fragilities were derived from the results of thermo-viscoelasticity. By Raman spectroscopic analysis, it was clear that the glass transition temperature is directly related to cross-linking degree reaction of epoxy resin. The fragility which denotes heterogeneous microstructure decreased when the glass transition temperature was saturated.Elastic moduli and fracture toughness at room temperature were measured for each epoxy resin. The elastic moduli were approximately constant for epoxy resin with saturated glass transition temperature. The fracture toughness was strongly dependent on curing conditions. The fracture toughness of the epoxy resin increased as th … More e fragility decreased when the glass transition temperature was saturated at approximately 400 K.Similar experiments were conducted for fused silica particle-filled bisphenol A type epoxy. As the results, the fracture toughness of composites increased for high glass transition temperature and low fragility. Therefore, it was confirmed that the glass transition temperature and the fragility are effective parameters for estimating mechanical properties of epoxy resin and its composite.Time-temperature dependences of fracture toughnesses for epoxy resin and silica particulate-filled epoxy composite were measured. The fracture toughnesses follow time-temperature equivalent principle determined by thermo-viscoelatic properties. The fracture toughness with a smaller fragility increased from lower temperature to the brittle-ductile transition temperature than that with a larger fragility when the glass transition temperature was approximately 400 K. Finally fracture of a cylinder with a crack was predicted mathematically based on time-temperature dependence of fracture toughness.Based on finding that glass transition temperature and fragility are very useful in estimating mechanical properties, these parameters were proposed as the parameters for setting the curing conditions of epoxy resin and its composite. Less