Taking three-layer composite beams as the research object, the finite element analysis method considering the geometric nonlinearity of double interface slip is studied. Firstly, the displacement governing differential equation of the three-layer composite beam is established based on the basic equations of elasticity, namely equilibrium, geometry and physics equations. The geometric linear element stiffness matrix with “precise” characteristics in local coordinate system (co-rotation coordinate system) is derived by direct stiffness method. Secondly, the transformation matrix between the structural coordinate system and the local coordinate system is derived by the co-rotation coordinate method of geometric nonlinear analysis, and the geometric nonlinear tangential stiffness matrix of the three-layer composite beam element under the structural coordinate system is established, and the corresponding equivalent node force matrix can be obtained simultaneously. Finally, the rigid arm and force equivalence principle are used to consider the eccentricity effect caused by the inconsistency between the point of concentrated force applied to the three-layer composite beam & the boundary constraint point and the node of the finite element model. Based on the above results, a finite element analysis method for three-layer composite beams considering geometric nonlinearity of double-interface slip is established, and the corresponding program is developed. Three typical examples of three-layer composite beams are analyzed, and the correctness and reliability of the proposed method and the developed program are verified by comparing with the calculation and test results of existing literatures.

three-layer composite beam  /  geometric nonlinearity  /  double interface slip  /  co-rotational coordinate method  /  precise element stiffness matrix