Research On Carrying Capacity Of Negative-Curved Stiffened Composite Panels

With the increasing demand of the aerodynamic shape and the stealth performance of the modern aircraft, stiffened panels containing the complex surface has been widely applied to aircraft design. In this paper, the research of the buckling and post-buckling of the negative-curved stiffened composite panels has been carried out. This type of structure is widely used in the design of aircraft inlet. The common load type of negative curved stiffened composite panels is compressive loading and shear loading, so buckling is the main form of the instability. After buckling, the structure still has a high post buckling carrying capacity. Therefore, the analysis included the post-buckling characteristics, the damage process and failure mode of the negative curved stiffened composite panels has important practical value.In this paper, the models of the negative-curved stiffened composite panels were established by the finite element software Abaqus. The model is based on the first-order shear deformation theory, and uses the cohesive element to simulate the adhesive layer between the panels and the stiffeners. Firstly, linear buckling analysis of the negative-curved stiffened composite panels is carried out. The first order buckling mode is introduced into the post-buckling analysis as the initial injury of the structure. The Quads failure criteria and the Hashin failure criteria were adopted to predict the damage of cohesive elements and composite laminates, respectively. With the use of the stiffness reduction, an user material subroutine was wrote to simulate the damage process and failure mode of the model. Studies have shown that in the limit load, the mainly damage form of the model is the substrate tensile failure and the adhesive layer damage.Based on the study above, the influence on the carrying capacity of the two principle curvatures Kx and Ky that controls the shape of the model had been reserched. Effects of height, configuration and number of stiffeners on buckling and damage loads of negative-curved stiffened composite panels had been investigated. The results indicated that the buckling and damage loads increased as increasing the height and number of stiffeners.