Theoretical characteristics of the vibration of sandwich plates with in-plane negative Poisson's ratio values

This paper is concerned with re-entrant cell honeycombs which show in-plane negative Poisson's ratio values, in which their anisotropic mechanical pro perties are described using the cellular material theory. Out-of-plane shea r moduli are affected by the unit cell geometric parameters and, for some r anges of the latter, it is possible to obtain higher values of the shear mo duli compared to those of a regular hexagonal honeycomb, in particular for cell geometries with a negative Poisson's ratio. A first order sandwich pla te theory is applied in order to obtain the fundamental frequencies of sand wich laminates in cylindrical bending and for the simply supported case. Se nsitivities of the frequencies per unit mass versus the geometric cell para meters are also calculated. The results suggest that the dynamic performanc e of a sandwich structure could be significantly improved with a proper des ign of the unit cell shape of the honeycomb. In particular, re-entrant cell cores offer improvements in bending stiffness capabilities for particular cell parameter ranges. (C) 2000 Academic Press.