Study on shear postbuckling failure of composite sandwich plates by a quasi-conforming finite element method

A quasi-conforming triangular sandwich plate element with 7 degrees of freedom (DOF) per node is established based on a simplified Zig-Zag model and a transverse shear deformation theory. The accuracy of the proposed element has been validated to be equivalent to the element based on the complete Zig-Zag model (11 DOF per note). The path-following method, proposed by Huang and Atluri, is improved and applied to follow complex postbuckling paths with secondary bifurcation points and progressive failure. A finite element (FE) modeling is completed to study the shear postbuckling behavior and failure of composite sandwich plates, based on the energy criterion of stability and the strength criterion of each layer. The basic characteristics of the shear postbuckling and failure are illustrated. The complexity and computation difficulty caused by secondary bifurcations and multi-paths are discussed. Numerical examples show that the proposed method is efficient in improving the convergence of iterations.