液体垫片对复合材料单搭接螺栓接头力学性能的影响

复合材料构件由于存在制造误差，装配时常常产生间隙，消除间隙的一种基本手段是向其中填充液体垫片。以复合材料单搭接螺栓连接接头为研究对象，设计了拉伸实验，选取一种改进的失效准则与对应的材料退化准则建立了渐进损伤有限元分析（FEA）模型，在此基础上研究了液体垫片对复合材料单搭接接头强度、刚度等力学性能的影响及复合材料孔内损伤演化的过程，此外还研究了液体垫片孔边的应力-应变状态。由实验与有限元结果可以得出：随着液体垫片厚度的增加，接头的拉伸刚度与峰值载荷均有所降低；相同载荷下复合材料孔内损伤加剧，孔内单元产生初始损伤时对应的载荷降低；但液体垫片厚度的增加可以降低垫片孔边的应力与塑性应变峰值，并使其分布更加均匀化，改善液体垫片孔边受力状态。

Influences of the liquid shim on the mechanical properties of single-lap composite bolted joint

Composite material components may produce gaps during assembly due to their manufacturing errors. It is a basic method to use the liquid shim to fill the gaps. The tensile experiment was designed for composite single-lap bolted joint. An improved three-dimensional failure criterion and the corresponding degradation of the material were chosen in the finite element analysis(FEA) modeling. On this basis, the influences of the liquid shim on the mechanical properties of single-lap composite bolted joint were studied, such as strength and stiffness. The damage evolution process around the hole in composite and the state of stress and strain around the hole in shim were also studied. From the experiment and finite element results, it can be concluded that with the increase of liquid shim thickness, the tensile stiffness and peak load of the joints are reduced. It can also make the hole in composite have more serious damage under the same load and decrease the load when the initial damage appears. But the increase of the liquid shim thickness can decrease the peak stress and the plastic strain of the hole in the liquid shim and make their distribution more uniform, which can improve the stress condition around the shim's hole.