Isogeometric-based Asymptotic Analysis on Multi-layered Thin Shells

Shell structures are generally modeled based on kinematic hypotheses, where certain involved parameters have to be evaluated phenomenologically. In this article, we propose an isogeometric-based asymptotic analysis scheme aimed at achieving a rational modeling and interpretation about the deformation behaviors of multi-layered thin shells (MTSs). Asymptotic analysis of the three-dimensional governing elasticity equations allows us to gain a deeper insight over shell theories in three aspects. Firstly, the intrinsic hierarchy lying in the displacement field, stress components, constitutive law, and momentum conservation, resulting from the shell thinness, is naturally suggested through asymptotic analysis, and not only the overall stiffness but also the key stress components can be formulated in a fully rational manner. Secondly, through detailed discussion on the order of non-dimensional maximum principal curvature, it is shown that a shell must deform in one of the following two deformation modes. One regime exhibits a mode resembling that of thin plates, while the other corresponds to a piecewise linear distribution of local transverse shear stresses along the thickness. And the specific orders of the key quantities are determined for both cases. Thirdly, in contrast with the existing arguments where an applied shear load on the shell surface necessitates the inclusion of transverse shear stresses for analysis, it is demonstrated that a leading-order shell theory derived from asymptotic analysis should suffice to output satisfactory predictions over the shell stiffness, as well as its internal stress distribution. Numerical examples of the deformation and strength analysis for the MTS are also presented to show the reliability of the proposed method for shell modeling.