预浸料贮存时间对MT700/603复合材料力学性能的影响

以碳纤维增强环氧树脂热熔预浸料MT700/603为研究对象，开展室温贮存时间与预固化度的关联性分析，研究预浸料预固化度对复合材料成型质量和关键力学性能的影响机制，建立预浸料贮存时间-预固化度-制品性能三者之间的内在联系。结果表明:随着室温贮存时间的延长，60 d后603环氧树脂的最低黏度增加了4.6倍，玻璃化转变温度增加了17.9 ℃，预固化度为11.2%；MT700/603预浸料贮存时间小于30 d时，制备的复合材料内部质量良好，纤维分布较为均匀，孔隙率较低，树脂的预固化度在5.3%以内，孔隙率低于0.03%；复合材料更倾向依赖于树脂基体破坏的纵向压缩强度和压缩模量对孔隙率的敏感度，要高于倾向依赖于纤维增强体破坏的纵向拉伸强度和拉伸模量；预浸料在室温贮存时树脂预固化度增加，黏度增大，加压时机与树脂黏度变化不匹配是导致复合材料构件关键力学性能下降的根本原因；根据产品的力学性能指标要求，结合不同贮存时间的关键力学性能数据，可反推出预浸料的最长室温贮存时间，实现了预浸料可用性的定量化评估。 

Effects of prepreg ambient-temperature storage life on mechanical properties of MT700/603 composites

A hot-melt prepreg MT700/603 was prepared. The correlation between ambient-temperature storage life and the degree of pre-curing, and effects of pre-curing degree on composite quality and mechanical properties were investigated and discussed. The relationship among prepreg storage life, pre-curing degree and composite properties was established. The results show that the minimum viscosity is increased by 4.6 times after 60 days' storage at room temperature. Meanwhile, the glass transition temperature is increased by 17.9 ℃ and the pre-curing degree is increased to 11.2%. When storage life is less than 30 days, the composites show good internal quality, uniform fiber distribution and low porosity (≤0.03%), and the pre-curing degree is less than 5.3%. The longitudinal compression strength and modulus of composites tendentiously dependent on the failure of resin matrix are more sensitive to porosity than the longitudinal tensile strength and modulus dependent on the failure of fiber reinforcement. With the extension of storage life, the pre-curing degree and the viscosity of resin increases, and there is a mismatch between the pressurized moment and the resin gel point, which is the fundamental reason for the decrease of mechanical properties in composites. The maximum ambient-temperature storage life can be deduced according to the design requirement and mechanical properties data in different storage periods, realizing the quantitative evaluation of the prepreg availability.