AN EVALUATION OF GEOMETRICAL NONLINEAR EFFECTS OF THIN AND MODERATELYTHICK MULTILAYERED COMPOSITE SHELLS

This paper, which deals with geometrically nonlinear analysis of multi layered shell structures, presents an evaluation of the approximations made when simplified models are introduced. To this purpose, a transv erse shear deformable shell finite element formulation including finit e rotations and large displacements is employed and von Karman, as wel l as moderate and small rotation theories, are obtained as particular cases. Classical shear deformation type-results have been improved in moderately thick shell analysis by using modified multilayered shear s tiffnesses. These stiffnesses have been calculated through a variation al technique which accounts for parabolic interlaminar continuous tran sverse shear stress fields and zig-zag form of the in-plane displaceme nts along the shell thickness. Stability problems of several flat and cylindrical thin and thick geometries, different multilayered lay-outs (cross-ply, angle-ply symmetrically and unsymmetrically laminated, in cluding sandwich) and loading conditions are considered in the numeric al investigations. It has been concluded that geometrical nonlinear ef fects are problem dependent, furthermore such effects become more sign ificant in thick shell analysis with respect to thin structures. (C) 1 998 Elsevier Science Ltd. All rights reserved.