ENFORCING OF AN THEORETICAL SOLUTION OF THREE ADHESIVE JOINTS INTO SIMPLIFIED FINITE ELEMENT FORMULATIONS FOR STIFFNESS PREDICTION

A general displacement theory is proposed for unsymmetrical adhesive joints, for which the two adherends could have different thicknesses and consist of different materials. Hence this analysis is more general than that of the joints with similar adherends. This approach is capable of satisfying all the boundary conditions of stress equilibrium in the joint, including the zero shear stress condition at the ends of the bondline. Then, through the use of particular boundary displacement conditions on the basis of the displacement theory developed, the stiffness matrices of three simplified finite elements are obtained for structural adhesive joints, including the T-type, L-type and single-lap joints. The adhesive joint elements can consider the continuous nature of load transfer between two adherends, reduce the number of degree-of-freedom dramatically and prevent the modeling deficiency in previous adhesive elements that an adhesive layer was modeled much thicker than its actual size due to offset nodes. The three simplified finite elements were verified in the numerical experiments, respectively. A fairly good agreement is observed between the simple and refined model results. The adhesive joint models have potential to be applied in the large-scale finite element models such as automotive and aircraft structures.