Delaminated multilayered plates under uniaxial extension. Part I: Analytical analysis using a layerwise stress approach

The aim of this two-part paper is to propose an efficient and accurate alternative to the computationally expensive three-dimensional finite element method (3D-FEM), for analyzing delaminated multilayered plates under uniaxial extension. Many of the existing models deal with the analysis of multilayered structures only in the non-delaminated state. The first part of the present study extends the application of a layerwise stress model, called the LS1 model, to delaminated multilayered plates subjected to uniaxial extension. The analytical LS1 solutions are derived for general non-delaminated and delaminated multilayers and compared to 3D finite element solutions. The comparison gives a good agreement between the LS1 and 3D-FE models except near singularities (free edges, crack tips, ...). In order to overcome this drawback, a refinement approach, called the refined LS1, is presented in Part II and applied to angle-ply rectangular composite laminates. The comparison between the refined LS1 and 3D-FE models reveals an excellent agreement, even in the vicinity of singularities, in terms of interlaminar stresses and strain energy release rate. The main conclusion of the second part is that the proposed refined LS1 model can be used as an accurate and very efficient model for evaluating the interfacial stress fields as well as the strain energy release rate in multi-delamination problems.