ABSTRACT
Most composite structures are built as assemblies of plates and shells. This is because the structure is more efficient when it carries membrane loads. Another important reason is that thick laminates are difficult to produce. Deformation and stress analysis of laminated composites can be done at different levels. In most cases, stress and strains need to be calculated for every lamina in the laminate. Then, the actual laminate stacking sequence must be input to the program. Standard shell elements, even if they are not laminated, can be used to model a unidirectional laminate and obtain correct results of displacements, strains, and stress. The apparent laminate properties represent the stiffness of an equivalent orthotropic plate that behaves like the actual laminate under in-plane loads. Care must be taken for unbalanced laminates that the A and H matrix are formulated in a coordinate system coinciding with the axes of orthotropy of the laminate.
