Buckling Behavior And Load-carrying Capacity Of Composite Stiffened Pannel With Cutout Under Shear Load

Since the composite material has very good material properties such as high strength-to-weight ratio,high specific modulus and good fatigue resistance performance,it is more and more widely used in flight vehicle structures,and the applied technology of advanced composite is under rapid development.Advanced carbon fiber resin matrix composite stiffened panels have a large-scale application in aerospace and other industrial areas,but normally,it will lead to structural instability which can cause failure when the structure is subjected to shear or compress load.At the meantime,the cutout structure in stiffened panels and the bonding defects between skin and stiffeners seriously impact on the structure stability,so the study of buckling behavior of composite stiffened panel with cutout under shear load is of great significance.In this dissertation,the "Z" section stringer and the "C" section frame are selected which are bonded to the flat skin.The nonlinear finite element analysis model for the composite stiffened panel with cutout is built by the usage of commercial software ABAQUS,and the cohesive element has been used to analyze the debonding load.In the analysis model,the Hashin's criteria is adopted for skin,frame and stringer failure identification and Quards criteria adopted to identify debonding failure.By using a degradation constitutive model,the buckling mode and the post-buckling strength capacity of the composite stiffened panel are predicted.Then the static tests under shear load for stiffened panels with and without preset debonding were investigated,by observations of the test phenomenon and the data acquisition,the following conclusions can be obtained:1 The composite stiffened panel with cutout does not fail immediately under buckling,which still has a reasonable load-carrying capacity.The final failure load can be approximately above 2.9 times the buckling load.2 The cutout and the reinforcement structure significantly changed the shear buckling mode.3 The bonding quality has remarkable influence on the post-buckling strength capacity,improvement of the bonding quality and strength can improve the load-carrying capacity.The failure of the two test articles were caused by structural instability,but the failure process is different.4 By observation of the analytical and test results,the method adopted can accurately predict buckling load,failure mode and failure process of the structure.