高温老化对三维角联锁机织复合材料低速冲击性能影响

发布时间：2018-09-08 14:38

【摘要】：三维角联锁机织复合材料,具有结构整体性和高抗分层性特点,被广泛应用耐冲击工程结构设计。复合材料工程结构高温老化后冲击性质是实际应用中经常遇到的问题。本文研究三维角联锁碳纤维/环氧树脂复合材料在90℃、180℃高温大气环境下老化不同时间后准静态压陷和低速冲击性质。采用扫描电镜观察复合材料高温老化后横截面形态及实验后纤维抽拔情况;通过树脂热重分析(TGA)、差示扫描量热分析(DSC)、红外光谱分析(IR)等方法表征环氧树脂基体热老化性质。结论如下:(1)环氧树脂DSC及IR分析:环氧树脂高温老化后,DSC曲线上一个后固化放热峰,及红外谱图上一个环氧峰(波峰数916cm-1)消失,表明树脂发生后固化。环氧树脂TGA、DSC及IR分析:树脂180℃时热分解速率约为90℃的2.5倍;随温度及时间增加,树脂热降解质量比率增大;在90℃及180℃老化,树脂发生热氧化,且180℃老化时树脂热降解严重。环氧树脂老化过程存在后固化和热氧降解两种机制。90℃老化前期环氧树脂因后固化交联度增加,树脂静态压缩强度及模量增大,老化16天时,分别增加约9.4%、8.4%;因热氧降解作用,32天老化树脂压缩强度及模量略微减小;在180℃老化时,环氧树脂因热氧降解作用突出,树脂压缩强度及模量在老化32天时分别降低约9.0%、35.5%。(2)90℃老化复合材料基本没有颜色变化,横切面没有裂纹。在180℃时,老化时间增加,复合材料因严重热氧降解,表面树脂失重收缩,碳纤维暴露,颜色逐渐由灰黑变为褐黄,最后呈现黑褐色。扫描电镜观察复合材料横切面发现:在180℃老化温度下碳纤维与树脂间会脱粘,且脱粘程度随老化时间增加增大,出现大裂纹,90℃时没有脱粘。扫描电镜观察复合材料冲断面纤维抽拔。180℃老化纤维抽拔数量及长度随时间增加增大。(3)90℃老化时,因后固化作用,准静态压陷强度及模量随时间增加增大,在16天时达到最大,分别增加约5.4%、1.8%;180℃时,因热氧降解作用,树脂与纤维间脱粘,复合材料最大强度及模量随老化时间增大而减小,在32天时分别减小约20.5%、6.9%。(4)复合材料低速冲击最大强度及模量随老化时间变化趋势与准静态一致。90℃老化时,复合材料最大强度及模量随时间增加而增加,持续到老化16天,此时分别增加约6.4%、4.9%。因剧烈热氧降解,180℃老化复合材料最大强度及模量随老化时间增加而减小,在32天时分别减小约24.2%、6.5%。(5)在90℃时,随老化时间增加,复合材料弹性吸收能增加,在32天时增加约29.1%。180℃老化复合材料弹性吸收能随时间增加先减小,在老化16天时减小约19.3%;老化32天时,复合材料因弹性阶段持续到大量纤维断裂,弹性吸收能比老化16天略增大。大气环境中三维角联锁机织复合材料老化性质是实际应用的重要课题,该项工作可进一步扩展出不同环境温度服役时间三维纺织复合材料工程结构设计,为目前普遍采用的单一环境条件参数设计扩充新内容。
[Abstract]:Three-dimensional angular interlocking woven composites are widely used in impact resistant engineering structures because of their structural integrity and high delamination resistance. The impact properties of composite structures after high temperature aging are often encountered in practical applications. Quasi-static indentation and low-speed impact properties of composites after aging at different time in gas environment were observed by scanning electron microscopy (SEM), and the thermal aging properties of epoxy resin matrix were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and infrared spectroscopy (IR). The conclusions are as follows: (1) DSC and IR analysis of epoxy resin: after aging at high temperature, a post-curing exothermic peak on DSC curve and an epoxy peak on infrared spectrum (wave number 916 cm-1) disappeared, indicating that the resin cured after occurring. TGA, DSC and IR analysis of epoxy resin: the thermal decomposition rate of epoxy resin at 180 C was about 2.5 times of 90 C; with temperature and time increasing; In addition, the thermal degradation mass ratio of epoxy resin increases, and the thermal oxidation of the resin occurs when the resin is aged at 90 and 180 degrees, and the thermal degradation of the resin is serious when the resin is aged at 180 degrees. The compressive strength and modulus of the resin increased by 9.4% and 8.4%, respectively; the compressive strength and modulus of the resin decreased slightly after 32 days of aging due to thermo-oxidative degradation; the compressive strength and modulus of the resin decreased by 9.0% and 35.5% respectively after 32 days of aging due to the prominent thermo-oxidative degradation of the epoxy resin at 180 (?) Cracks. At 180 C, the aging time increases, the composite surface resin shrinkage due to severe thermal oxygen degradation, carbon fiber exposure, color gradually from grey black to brown, and finally brown. SEM observation of the cross section of the composite material found that at 180 C aging temperature, carbon fiber and resin will be debonded, and the degree of debonding with aging. Scanning electron microscopy showed that the number and length of fiber pulled out at 180 C increased with time. (3) When aging at 90 C, the quasi-static compressive strength and modulus increased with time, reaching the maximum at 16 days and increasing about 5.4% respectively. The maximum strength and modulus of the composites decreased with the aging time increasing, and decreased about 20.5% and 6.9% respectively at 32 days. 4) The variation trend of the maximum strength and modulus of the composites with aging time was consistent with that of the quasi-static composites. The maximum strength and modulus of composites decreases with the increase of aging time, and decreases by 24.2% and 6.5% at 32 days, respectively. (5) The elastic absorption energy of composites increases with the increase of aging time at 90 degrees centigrade, and increases at 32 days. The elastic absorption energy of the composites decreases firstly with the increase of time, and decreases about 19.3% at 16 days of aging. At 32 days of aging, the elastic absorption energy of the composites increases slightly compared with that of the composites after 16 days of aging. This work can further expand the design of three-dimensional textile composite engineering structures with different service time at different ambient temperatures, and expand the new content for the design of single environmental parameters commonly used at present.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332

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