Effect of core and face sheet anisotropy on the natural frequencies of sandwich shells with composite faces

The objective of the present study is the analysis of the effect of core and face sheet anisotropy on the natural frequencies of plane and doubly curved sandwich structures with laminated composite face sheets and an anisotropic core. For the analysis, a higher-order sandwich shell theory is adopted. For the special case of a sandwich shell with rectangular projection, an analytical solution is obtained by means of an extended Galerkin procedure. Assuming a harmonic time-dependent response, the problem is transformed into an eigenvalue problem, which can be solved in a numerically rather efficient manner. The numerical scheme is applied to an analysis of the effect of the face sheet anisotropy induced by fibre angle variations in laminated face sheets consisting of unidirectionally infinite fibre reinforced carbon epoxy plies. Further anisotropy effects derive from the use of honeycomb cores with anisotropy transverse shear moduli. It is observed that anisotropy of core and face sheets may have distinct effects on the lower natural frequencies.