A simple analysis using two-dimensional lamination theory combined with the ap propriate three-dimensional anisotropic constitutive equation is presented to show some rather surprising results for the range of values of the through-the-thickness ef fective poisson's ratio vxz for angle-ply laminates. Results for graphite-epoxy show that the through-the-thickness effective poisson's ratio can range from a high of 0.49 for a [90] laminate to a low of -0.21 for a [±25]S laminate. It is shown that negative values of vxz are also possible for other laminates.

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This paper presents the results of a zeroth-order solution for edge effects in angle-ply composite laminates obtained using perturbation tech niques and a limiting free body approach. The general solution for [±θ] laminates is applied to the special case of a [±45]s graphite/epoxy lamin ate. Interlaminar stress distributions are obtained as a function of the laminate thickness-to-width ratio h/b and compared to finite difference results. The solution predicts stable, continuous stress distributions, determines finite maximum tensile interlaminar normal stress σz, and provides mathe matical evidence for singular interlaminar shear stresses τ xz and τyz in [±45] graphite/epoxy laminates.

The dispersion of harmonic waves propagating in an arbitrary direction in a layered orthotropic elastic composite is studied. The full three-dimensional field equations of elasticity are considered, and the corresponding twelfth order characteristic determinant is examined. Numerical results are obtained and compared with the corresponding estimates of the new quotient method of Nemat-Nasser.

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