Keywords: laminated composites, finite element analysis, layer lumping, unbalanced laminate.

Laminated composite structures have been widely used in the aviation and construction fields because of their high specific stiffness, high specific strength and anisotropic material properties. When using the finite element method to analyze these structures, special attention to modelling is required because of their anisotropic characteristics. This paper addresses the effect of layer stress and displacements of a laminate under loading due to element meshing, boundary constraints and material properties used in the modelling of composite structures.

In using the materials properties in a one-dimensional element, the conventional method of obtaining the equivalent modulus is based on the lamination theory. This expression is an inherent one with a non-zero initial curvature. An expression for the equivalent modulus that satisfies the initial zero curvature requirement is presented. Lumping a group of layers into a single layer is often used in thick laminate analysis. The expression of equivalent moduli and Poisson's ratio for the lumped layer is also reviewed.

The stress effects due to boundary constraints between two and three-dimensional modelling depending on a laminate configuration, when using a quarter-model instead of a full-model will result in a significant error in displacements for unbalanced laminates under tension. This also gives a significant difference in the maximum stress concentration between the quarter- and full- models for an angle ply in symmetrical laminates with a hole.

The meshing used in composite modelling may affect the structural deformation. Applying geometrically anisotropic meshes should be avoided.

It is learned that extending the experience from modelling isotropic structures to the laminated composite structures should be undertaken with care. It is concluded that modelling a composite structure requires a thorough understanding the structural characteristics of composites.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £145 +P&P)