Interlaminar stress calculation in composite and sandwich plates in NURBS Isogeometric finite element analysis

This research paper describes the development of NURBS Isogeometric finite element analysis and post-processor for interlaminar stress calculation in composite and sandwich plates. First-order, shear-deformable laminate composite plate theory is utilized in deriving the governing equations using a variational formulation. Linear, quadratic, higher order and k-refined NURBS elements are constructed and numerical validation is performed for laminated composite and sandwich plates. Lagrange finite element suffers from higher order stress gradient oscillations due to Gibbs phenomenon and require alternative stress recovery procedures for accurate interlaminar stress calculations, especially interlaminar normal stress. In this paper, direct post-processing is performed which computes interlaminar shear and normal stresses from higher order gradients of NURBS basis in a single step procedure. Interlaminar stresses are found to be in an excellent agreement with 3D elasticity solution and FSDT along with k-refinement procedure of NURBS basis is found to compute equivalent or better interlaminar normal stress than higher-order shear deformation theory.