混元胶接单搭接头的应力与刚度分析

STRESS AND STIFFNESS ANALYSIS OF BI-ADHESIVE BONDED SINGLE-LAP JOINTS

拉剪胶接接头的峰值应力常发生在搭接区端头,而中间区的应力非常小,为降低应力集中,提高接头强度和连接效率,系统研究胶层变刚度的混元胶接技术,将高弹性模量的脆性胶置于中间区,而低模量的韧性胶置于搭接区边缘。以胶接理论为基础,考虑被粘物剪切应变,建立单搭拉剪混元胶接接头的线弹性应力和刚度解析模型。理论模型中的正应力和剪应力与有限元模型吻合得较好,证实理论模型的正确性。有限元和解析解均表明,混元胶接接头在搭接区端头的峰值剪应力分别较单一刚性胶和柔性胶胶接时下降了52.1%和24.4%,参数研究中确定了影响混元胶接接头应力和刚度分布特征的关键耦合参数。

The stresses in adhesive-bonded single-lap joints peak at the edges, where failure usually begins, while the center adhesive stress is almost zero. To reduce the stress concentrations, and improve joint strength and efficieney, the mixed-modulus adhesive-bonded technology of variable the adhesive stiffness along the overlap was presented. A high-modulus brittle adhesive was applied in the central region of the bondline, while a ductile adhesive carried the strain in the outer regions prone to stress concentrations. The stress and stiffness analytical models of a single-lap joint based on the linear elasticity theory was developed, including the adherend shear deformations. The adhesive shear stress and longitudinal normal stress of the upper adherend in the analytical models were obtained and compared with the numerical solutions determined by the two-dimensional finite element analysis. The theoretical and FEA（finite element analysis） results show a 52.1% or 24.4% decrease in the peak adhesive stress at the edges in the bi-adhesive bonded joints compared with those in which single stiff or flexible adhesives were used over the full length of the bondline. The numerical experiment shows that the results of the theoretieal and the FEA model agree with closely. Finally, the relevant key parameters are identified and discussed.