Global-local model coupling for composite shell structures in the framework of isogeometric analysis

Nitsche's method had recently demonstrated its potential for a seamless and continuity-preserving coupling of NURBS patches in isogeometric shell analysis. Trimmed and non-conforming patches and even blended models including classical thin-shell and solid-shell formulations can be coupled successfully while preserving a continuous flux along the coupling interfaces. In this paper, we take advantage of the method's modeling flexibility for an extension to NURBS-based laminate composite shell structures. We introduce a global-local model coupling approach to enrich laminate composite thin-shell Kirchhoff-Love models locally with a full three-dimensional continuum solution. The approach provides a reliable coupling of the classical lamina theory with a layerwise formulation revealing the full interlaminar stress state at reduced computational cost. The layerwise shell model is based purely on a mid-surface NURBS description of the shell body thus supporting the direct application of a surface-defined CAD data representation of shells. We apply a refined finite cell approach to handle efficiently trimmed geometries, as common in CAD models. We demonstrate reliability, accuracy of the coupling approach and efficiency in terms of numerical costs and modeling effort of our approach with several examples.