The influence of the substrate’s stiffness on the liquid shim effect in composite-to-titanium hybrid bolted joints
The influence of the substrate’s stiffness on the liquid shim effect in composite-to-titanium hybrid bolted joints
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DOI：
10.1177/0954410013476612
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发表时间：
2014-03
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影响因子：
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通讯作者：
L. Liu
中科院分区：
文献类型：
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作者：
L. Liu
现场铸造液体垫片通常用于修复大型飞机结构组装过程中出现的间隙/失配问题。液体垫片对组装结构性能的影响不仅受到垫片厚度和力学性能的影响，而且还受到垫片使用位置的影响，也就是说基材的刚度可能会影响垫片的效果。为了研究垫片在复合材料-钛螺栓连接中的应用，引入了三维有限元方法，该方法综合了复合材料的渐进损伤、钛合金的弹塑性、液体垫片的超弹性、接头单元之间的接触关系以及机械接头的真实装配条件。通过与试验结果对比验证后，采用建模方法模拟垫片螺栓接头的拉伸响应。此外，还详细研究了液体垫片层厚度对复合材料钛螺栓接头力学行为的影响以及基底刚度对液体垫片效果的影响。通过对结果的分析可以看出，随着液体垫片层厚度的增加，接头的最大载荷、初始接头刚度和设计载荷均减小；液体垫片层的效果很大程度上依赖于基材的刚度，当基材变硬时，液体垫片层的效果会降低。
Cast in place liquid shim is usually used to fix the gap/mismatch problems, which occur during assembly process of large aircraft structures. The effect of liquid shim on performances of the assembled structures is influenced not only by thickness and mechanical properties of the shim, but also by the location where the shim is used, that is to say the stiffness of the substrates may have impact on the shim’s effect. To study the usage of shim in composite-to-titanium bolted joints, a three-dimensional finite element method is introduced, and the method incorporates the progressive damage of composite materials, elastic-plastic property of the titanium alloy, super-elastic property of the liquid shim, contact relationships between the joint elements, and real assembly conditions of the mechanical joints. After validating through comparing with the experimental results, the modeling method is adopted to simulate the tensile response of the bolted joints with shims. Furthermore, both the influence of liquid shim layer thickness on the mechanical behaviors of composite-to-titanium bolted joints and the influence of the substrate stiffness on the liquid shim effect are studied in detail. Based on the analysis of the results, it can be concluded that the maximum load, initial joint stiffness and design load of the joints decrease with the increase of liquid shim layer’s thickness; and the effect of liquid shim layer relies heavily on the stiffnesses of the substrates and will reduce when the substrates become stiffer.