Influence of out-of-plane ply waviness on elastic properties of composite laminates under uniaxial loading

In this paper the influence of out-of-plane ply waviness on elastic properties of composite laminates subjected to uniaxial loading is investigated. A three-dimensional analytical method based on the classical lamination theory is developed to quantitatively determine the effective elastic constants of thick composite laminates with ply waviness. Various influential factors associated with ply waviness, such as the waviness geometry, the off-axis angle, the extent of wavy region, and the waviness pattern, are incorporated in the multi-parameter model. Analytical results for the Young’s moduli, the shear moduli and the Poisson’s ratios of wavy fiber composite laminates are obtained and discussed for a specific range of fiber volume fractions and two different lay-ups. Negative Poisson’s ratios are found for unidirectional laminates nested wavy ply/plies. The present method provides a useful and effective tool to evaluate the effects of out-of-plane ply waviness on three-dimensional elastic properties of composite laminates.