低速冲击下纤维金属层合板的损伤模式研究

Study on damage mode and damage evolution of fibre metal laminates subjected to low-velocity impact

为研究低速冲击下纤维金属层合板(FMLs)的损伤特点,对由玻璃纤维和2024-T3铝合金交替层压而成的层合板进行了落锤低速冲击试验,并将试验结果与2024-T3铝板进行了对比;分析了FMLs的动态冲击响应并根据各能量下的损伤情况总结了其损伤规律。结果表明:冲击后裂纹长度、凹坑深度等随冲击能量的变化关系曲线上存在裂纹产生、裂纹分叉和完全穿透三个转折点。为研究冲击过程中层间相互作用,采用有限元方法分析了FMLs的低速冲击后动态响应,讨论了FMLs中铝层和纤维层之间的分层等情况,各分层大致呈椭圆状,其长轴与轧制方向垂直。同时将冲击能量为15J和45J下的模拟载荷-时间曲线与试验结果进行了对比,其最大载荷误差分别为10.2%和5.6%,从而验证了该数值方法的可靠性。

In order to improve fatigue property and impact resistance of aircraft structure, people design one new kind material called fibre metal laminates(FMLs) which consist of 2024-T3 aluminium alloy sheets bonded together with glass fiber prepreg. In order to study damage features of FMLs during impact, drop-weighted low velocity impact tests are performed and the results are compared with those of monolithic 2024-T3 sheets. Dynamic responses of FMLs are analyzed and damage modes are summarized according to damages at different impact energy. There are three inflection points in the curve of crack length and indentation depth versus impact energy: crack initiation, crack branching, and fully perforation. Finite element calculations are used to simulate the impact responses of FMLs to study the interaction between different layers. Damage evolution of delamination between aluminium and fibre layers is discussed, and the shape of delamination is almost elliptical with the major axis perpendicular to the rolling direction. Meanwhile, simulation results of force-time curves at 15 J and 45 J energy are compared with the experimental results and the differences of maximum force are 10.2% and 5.6%, respectively, which verifies that the finite element calculations can be used to study dynamic response of FMLs under low velocity impact.