A contact extended isogeometric layerwise approach for the buckling analysis of delaminated composites

Buckling of composite laminates with delaminations is studied based on a proposed isogeometric layerwise approach. The isogeometric approach employs the NURBS basis functions of the geometry’s description to approximate the physical response in an isoparametric sense. Layerwise theories provide an accurate prediction of the three-dimensional structural responses of composite laminates while maintaining a two-dimensional data structure. Usually, to model the delaminations through thickness, the displacement field is enriched with a unit step Heaviside function which allows for discontinuities at the delamination interfaces. An improved implementation of a displacement-based layerwise theory based on the isogeometric paradigm is proposed. The delaminated and undelaminated regions of the laminate are modeled as separate patches. For the undelaminated and delaminated patches respectively, the C0C0-continuity and discontinuity conditions of the displacement field at the ply interfaces can be easily facilitated within the isogeometric framework. More reliable and accurate buckling loads are obtained by considering a contact analysis across the delamination interfaces to avoid physically inadmissible buckling modes. The proposed model is verified using laminated composite beam plates. The results are compared to a classical layerwise approach. The numerical results confirm the accuracy of the proposed isogeometric model.