Symmetric laminate regular

However, a simple cascade of two-input two-output mixers results in an asymmetric lamination. Symmetric lamination can be obtained with a modification of the first mixer into a three-input two-output mixer which builds up a (7//4, Hjl, HjA) type of laminate. This initial mixer can be followed by as many regular two-input two-output mixers as desired for the particular application. 

Stiffnesses for single-layered configurations are treated first to provide a baseline for subsequent discussion. Such stiffnesses should be recognizable in terms of concepts previously encountered by the reader in his study of plates and shells. Next, laminates that are symmetric about their middle surface are discussed and classified. Then, laminates with laminae that are antisymmetrically arranged about their middle surface are described. Finally, laminates with complete lack of middle-surface symmetry, i.e., unsymmetric laminates, are discussed. For all laminates, the question of laminae thicknesses arises. Regular laminates have equal-thickness laminae, and irregular laminates have non-equal-thickness laminae. 

Derive the bending stiffnesses for regular symmetric special cross-ply laminates, that is, derive Equation (4.80) for the special case in which t = t = VN. 

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