A study of transverse normal stress effect on vibration of multilayered plates and shells

This paper evaluates transverse normal stress sigma(zz) effect on vibration of multilayered structures. To this purpose a mixed plate model initially introduced by Toledano and Murakami has been extended to dynamics analysis of double curved shells. These models allow both continuous interlaminar tr ansverse shear and normal stresses as well as the zigzag form of the displa cement distribution in the shell thickness directions to be modelled. Gover ning equations have been derived by employing a Reissner's mixed theorem. C lassical models on the basis of standard displacement formulations have bee n considered for comparison purposes. The evaluations of transverse stress effects have been conducted by comparing constant, linear and higher order distributions of transverse displacement components in the plate thickness directions. Free vibrational response of layered, simply supported plates, cylindrical and spherical shells made of isotropic as well as orthotropic l ayers has been analyzed. The numerical investigation carried out and compar ison with earlier results has concluded that: 1. The possibility of describing a priori interlaminar continuous transvers e normal stress sigma(zz) makes the mixed theories more attractive with res pect to other available modelling. 2. Any refinements of classical models are meaningless, unless the effects of interlaminar continuous transverse shear and normal stresses are both ta ken into account in a multilayered shell theory. (C) 1999 Academic Press.