ON THE VALIDITY OF NONLINEAR SHEAR DEFORMATION THEORIES FOR LAMINATEDPLATES AND SHELLS

This paper addresses the validity of the recently introduced so-called nonlinear shear deformation theories for laminated composite plates a nd shells. The finite element method is used to determine the maximum stresses for a wide range of statically loaded plate and shell panels. Various thickness ratios are included. This paper concludes that for the vast majority of composite materials and for moderately thick plat es and shells, stresses normally reach the maximum allowable stress be fore nonlinear terms can become important. This has been demonstrated by showing that for the limiting case of shear deformation theories (i n which the minimum span length (or radius) to thickness ratio is 20), the material usually fails before the maximum deflection reaches the magnitude of the thickness (where nonlinear terms start to become sign ificant). Therefore, the nonlinear shear deformation theories, which a re considerably more complicated than linear ones, have limited applic ations.