The Bearing Capacity Of Composite Stiffened Laminated Panels

Composite materials, wihch have much more specific strengh,specific stiffness and designalbility, are widely used in aviation, aerospace and other fields. A large number of composite laminates were used in modern aviation structure. The rib web of the plane wings, the skins between purlins and ribs, can be deal with as a composite material. When bearing pulldown or shear load,they may be instable, or even cause damage, resulting in disastrous consequences. In fact, being not immediately destroyed after buckling, the structure still has great bearing capacity, that is, the post-buckling strength. So in order to use the post-buckling strength to raise carrying capacity, It is necessary to study buckling and post-buckling of reinforced thin-wall structure. This article focus on post-buckling capacity of stiffener panels as part of the aircraft.In this paper, by the finite element method, ABAQUS software was used to analysis stability of composite laminated stiffened thin-wall structure under axial compression, calculate the critical load factor and buckling mode, and the empirical formula was used to simplify the structure of buckling load. Comparing the results of the two ways, The results proved that the finite element analysis has enough accuracy.Second, considering non-linear geometry, ABAQUS was used to simulate the carrying capacity of post-buckling of stiffened panels. Discussed the displacement constraints, the initial imperfections, stiffefer geometry, the strengthen border, load and other factors on the impact of buckling and post-buckling.The instability and destruction process of composite laminated structure are very complicated. Its destruction does not occur in whole, but layer by layer. In this paper, with ABAQUS secondary development, progressive failure mode based on Tsai-Wu theory will be introduced into the nonlinear finite element calculations, The post-buckling balance path and process of destruction of the composite thin-wall structure under axial compression, shear and combination load were obtained.The adhesive strength between the long purlin and wall panels is very important for the carrying capacity of a structure and the structural safety. The quadratic traction-interaction failure criterion is chosen for damage initiation in the cohesive elements; and a mixed-mode, energy-based damage evolution law based on the Benzeggagh-Kenane criterion is used for damage propagation. The cohesive element was used to simulate the debonding' occurrence and expansion between the stiffener and the skin of the reinforcement plate during post-buckling, providing the basis for the control of adhesive strength and the interface cracking.