An equivalent micromechanical multi-unit cell model carried by macromechanical full layerwise theory for flexural analysis of 3D braided composite and thick plates

摘要

3D braided composite plates and shells seem much more complicated for structural analysis than 2D laminated composite structures. In this article, a rather simpler and novel micro-/macromechanical theory is proposed for flexural analysis of 3D rectangular braided plates subjected to lateral loads. This theory is based on a novel micromechanically equivalent layerwised multi-unit cell, combined with the conventional macromechanical full layerwise theory, so-called here equivalent full layerwise/multi-unit cell theory. A 3D braided composite is considered as a cell system, where elastic properties of each cell depend on the position of cell along the thickness of cross section. Instead of acquiring global elastic constants of the 3D braided composite, three equivalent layers are established and the elastic constants for each layer are acquired separately. This micromechanical procedure makes this model consistent with macromechanical full layerwise theory. Based on this theory, the governing differential equations are derived for flexural analysis of rectangular 3D braided plate subjected to lateral loads. The problem is solved with Galerkin and finite element methods. The stress distributions in 3D braided composite plates seem quite different from those of geometrically equivalent homogeneous and isotropic plates. The differences are discussed in this article.