湿热老化对BFRP粘接接头横向冲击力学性能的影响

为了给车辆粘接结构的碰撞安全提供参考, 选取玄武岩纤维复合材料(BFRP)制作了单搭接接头; 根据车辆服役环境, 选取温度/湿度为80℃/30%和80℃/95%两种环境(GWCS和GWGS), 对接头分别进行了0、5、10和15 d的老化, 通过准静态拉伸测试了失效载荷和失效形式随时间的变化规律; 利用差示扫描量热法分析了BFRP和粘接剂在老化前、后的玻璃态转变温度; 对未老化和老化15 d后的接头进行了冲击能量为0、20、40和60 J的横向冲击试验, 分析了能量吸收、最大冲击载荷和最大变形随冲击能量的变化规律, 同时测试了接头失效载荷和失效形式的变化规律。分析结果表明: GWCS环境下, 老化后接头失效载荷下降比较小, 粘接剂发生后固化反应, BFRP发生分子链断裂, 接头更容易发生基体开裂或者纤维撕裂; GWGS环境下, 老化能明显加速接头性能的退化, 容易造成粘接剂与BFRP界面发生水解和膨胀, 老化15 d后失效载荷下降了54.99%, 失效断面为界面与内聚为主的混合失效; GWCS环境下, 老化后接头具有较好的承受冲击载荷和抵抗变形的能力, 冲击后失效载荷变化不大; GWGS环境下, 老化后接头受横向冲击影响明显, 承受冲击载荷和抵抗变形的能力较差, 在60 J冲击后接头表面损伤严重, 失效载荷下降明显, 下降幅度为58.71%, 失效断面为界面与内聚为主的混合失效, 损伤裂纹较为明显。可见, 车辆服役过程中, 粘接结构需尽量避免受高温高湿环境的作用, 尤其注意横向冲击对老化后粘接结构的影响。 

Effect of hygrothermal aging on transverse impact mechanical properties of BFRP adhesive joints

In order to provide a reference for crash safety of vehicle adhesive structure, the BFRP was selected to make single lap joints. According to the service environment of vehicle, the joints were aged for 0, 5, 10 and 15 d in two environments with the temperatures and humidities of 80 ℃/30%(GWCS) and 80 ℃/95%(GWGS), respectively. The change rules of failure load and failure mode with time were tested by using the quasi-static tensile test. The glass transition temperatures of BFRP and adhesive before and after aging were analyzed by using the differential scanning calorimetry. The transverse impact tests with the impact energies of 0, 20, 40 and 60 J were carried out for the joints which were unaged or aged for 15 d. The variation rules of energy absorption, the maximum impact load and the maximum deformation with the impact energy were analyzed, and the change rules of joint failure load and failure mode were also tested. Analysis result shows that after aging in the GWCS environment, the failure loads of joints decrease slightly, and the post-curing reaction of adhesive and the molecular chain fracture of BFRP occur, which makes the joints more prone to the matrix cracking or fiber tearing. In the GWGS environment, aging can obviously accelerate the degradation of joint performance, and easily cause hydrolysis and expansion of the interface between adhesive and BFRP. After 15 d of aging, the failure loads decrease by 54.99%, and the mixed failure of interface and cohesion occurs. After aging in the GWCS environment, the joints have good resistance to the impact load and deformation, and the failure loads change little after impact. After aging in the GWGS environment, the joint is obviously affected by the transverse impact, and its ability to bear the impact load and resist deformation is poor. After the impact of 60 J, the joint surface damages seriously, and the failure load decreases significantly, with the decrement rate of 58.71%. The mixed failure of interface and cohesion occurs, and the damage crack is obvious. It can be seen that in the process of vehicle service, the adhesive structure should avoid the effect of high-temperature and high-humidity environment, especially the influence of transverse impact on the aging adhesive structure.