The response of composite cylindrical shells with cutouts and subjected to internal pressure and axial compression loads

Abstract

Results from an analytical study of the response of composite shells with cutouts and subjected to internal pressure and axial compression are presented. The analytical results are obtained using a geometrically nonlinear finite element code. Results for axial compression and combined internal pressure and axial compression are presented. The effects of varying internal pressure and cutout size on the prebuckling, buckling, and postbuckling responses of the shell are described. Results indicate that the nonlinear interaction between the inplane load distribution and the out-of-plane displacements near the cutout can significantly influence the structural response of the shell. The results also indicate that these local load distributions and displacements can be affected by the size of the cutout and the internal pressure load. Introduction Many modern aerospace shell structures are designed to support combinations of internal pressure and mechanical loads during their service life. With the increasing need to produce lighter weight aerospace structures, the use of advanced composite materials has become more common in the design of these structures. During operation, flight loads and internal cabin pressure are present in all commercial transport aircraft. Some of these loads may be compressive loads and, thus, it is necessary to investigate the buckling characteristics of these structures. In addition, designers will *Ph.D. Candidate, Composite Structures Laboratory, Department of Aerospace Engineering. Student Member, AIAA. tHead, Structural Mechanics Branch. Fellow, AIAA. ^ Associate Professor, Composite Structures Laboratory, Dept. of Aerospace Engineering. Member AIAA. Copyright ©1998 by Mark W. Hilburger. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission. often need to incorporate cutouts or openings in the structure to serve as doors, windows, or access ports. It has been shown by a number of authors that a cutout in a shell structure subjected to axial compression can cause a significant reduction in the buckling load of the shell (e.g., Ref. 1-4). The local response near the cutout in a compression-loaded shell is strongly influenced by the local displacement gradients and the internal load distribution. These local displacements and internal load distribution can be affected by the size of the cutout. Recent studies of the response of cylindrical shells with longitudinal cracks and subjected to internal pressure and axial compression loads (e.g., Ref. 5) indicate that the interaction between the internal pressure load and the axial compression load can have a significant effect on the local response of the structure. The results of an analytical study of the response of composite cylindrical shells with cutouts and subjected to internal pressure and axial compression are presented. First, the governing parameters for the buckling of cylindrical shells with a cutout will be defined. The governing parameters will be used to develop the results of a parametric study presented in the paper. These parameters will help provide insight into the effects of changing geometric and laminate parameters on the buckling response of shells. The parametric study will include three cutout sizes and five internal pressure levels to determine the effects of varying the cutout size and internal pressure loads on the compression response. The predicted results are characterized by load-shortening response curves and contour plots of shell displacements and stress resultants. Finally, design curves based on classical parameters for the buckling of shells with cutouts and subjected to internal pressure and axial compression are presented.