Lateral Buckling Behavior of Pneumatically Stiffened, Reinforced Composite Beams in Bending

Abstract

The use of inflatable structures has often been proposed for aerospace applications. The advantages of such structures include low weight, easy assembly, and storage. The aim of this study is to investigate the effects of finite inflation on the subsequent buckling response of a carbon-fiber-reinforced composite beam (RCB) in bending. A finite element solution for three incremental beam configurations is developed. The first lateral buckling mode is used to determine the structural efficacy of the inflated beam. For each beam, the bending moment required to induce lateral buckling was determined. A nonlinear material and geometrically nonlinear finite element solution is obtained for the inflation load. A Rik method solution was then obtained to examine the postbuckling response of the RCBs. In addition, an eigenvalue extraction was performed to study the intrinsic influence of air pressure on the structural stability of RCBs. Finally, experimental data were obtained to verify the theoretical results. It is found that a simple eigenvalue extraction provides a conservative estimate of the critical buckling moment for preliminary design purposes. Furthermore, there is good correlation between theory and experiment and there exists noticeable interaction between the beam and pressurized air prior to final buckling for this type of reinforced composite beam.