单向碳纤维增强树脂基复合材料的超低温力学性能

摘要

采用真空袋-热压罐工艺制备单向碳纤维增强树脂基复合材料(CFs/EP)层合板,并将高低温试验箱与万能试验机相结合,通过合理使用低温胶和低温引伸计,并在降温过程中实施应力-应变实时调零等关键技术,在室温和液氧超低温度(-183℃)下对单向CFs/EP层合板进行拉伸和弯曲试验,研究了其超低温力学性能,并根据室温和超低温试验后试样的微观和宏观特征,揭示了超低温环境下复合材料力学性能变化机制.结果表明,与室温力学性能相比,单向CFs/EP层合板超低温拉伸强度下降约为9.5%,而拉伸模量上升约为6.2%,主要是由于超低温环境下,树脂的收缩使绝大部分碳纤维与树脂间形成了强界面,拉伸后试样呈"劈裂式"破坏形式,无法使每根纤维都充分发挥其强度,拉伸强度下降,同时超低温也限制了树脂大分子链的运动,所以导致单向CFs/EP层合板拉伸模量上升;单向CFs/EP层合板超低温弯曲强度和弯曲模量分别提高约54.75%和11.64%,这是由于单向CFs/EP层合板的常温和超低温的弯曲破坏形式均为分层剪切破坏,超低温下复合材料的界面增强,提高了单向CFs/EP层合板抵抗剪切分层的能力,进而使CFs/EP的弯曲性能得到提高.%Unidirectional carbon fiber reinforced epoxy (CFs/EP)laminate was prepared by vacuum bag molding process.By the combination of high-low temperature test box and universal testing machine,and rational use of low temperature adhesive and low temperature extensometer,cryogenic (liquid oxygen temperature,-183℃)tensile and flexural tests were conducted.During the cooling process,the stress and strain were set to zero timely.Accord-ing to the microscopic and macroscopic characteristics of samples,the cryogenic mechanical properties change mech-anisms of unidirectional CFs/EP laminate were revealed.The results show that,compared with the mechanical properties at room temperature,the cryogenic tensile strength of unidirectional CFs/EP laminates decreases about 9.5%,while the tensile modulus increases by about 6.2%.It is mainly due to that the resin shrinkage between car-bon fibers and resin forms a strong interface at low temperature.The "split"failure mode forms in the cryogenic tensile specimen,which means that not every fiber of unidirectional CFs/EP laminate develop its full strength,and leads to the tensile strength decreasing.While the low temperature limits resin molecular chain movement,which results in the tensile modulus of unidirectional CFs/EP laminates increasing.The cryogenic flexural strength and flexural modulus of CFs/EP laminates are increased to about 54.75% and 11.64%,respectively.It is because the bending failure mode of unidirectional CFs/EP laminates at room temperature and low temperature both are delami-nation shear failure.The cryogenic strong interface of unidirectional CFs/EP laminates improves interlamination shear resistance and makes the cryogenic flexural properties of unidirectional CFs/EP laminates improved.