Buckling, Post-buckling And Load-carrying Capacity Analysis Of Stiffened Composite Panels

Stiffened composite panels as a typical engineering structure, in aviation, aerospace, machinery and many other fields has been more and more applications. In actual use, the stiffened composite panels are often subject to compression, shear and combination of compression and shear loads, buckling instability is the most common failure mode. And stiffened composite panels have a high post-buckling strength capacity, which is needed for a reasonable use in design. And in the compressive and shear tests, the debonding between the stiffeners and the skin often occurs. Therefore, with consideration of debonding damage, how to accurately determine the critical buckling load and the post-buckling strength capacity of stiffened composite panels is one of the key problems demanding prompt solution in the composite material structure design.In ABAQUS/CAE platform, based on a first-order shear theory, a strength analysis model is presented to study the buckling and post-buckling behaviour of stiffened composite panels under compressive, shear, and combination of compression and shear loads using the nonlinear finite element method. In the model,the debond failure of the adhesive between the skin and stiffeners is considered by adding cohesive elements between the continuum shell elements and introducing penalty stiffness for the cohesive elements. The buckling load and post-buckling strength capacity of stiffened composite panels are well predicted, and the debonding failure is effectively simulated. Quads failure criteria and Hashin's failure criteria are adopted to identify the occurring of damage events of the cohesive elements and the composite panels,respectively. By using a degradation constitutive model of the mechanical properties,the failure and propagation of kinds of typical damage of the structure is simulated in detail. Numerical results show the effectiveness of the model. Parametric studies are conducted to study the effects of geometric parameters of stiffeners,adhesive strength,etc,and stacking sequences on buckling load and ultimate strength of stiffened composite panels are obtained. The results indicate that the increased height, thickness and number of stiffeners to some extent improving the buckling load and ultimate strength, the transition from instability failure to strength failure existing when the especial number of stiffeners is obtained, interfacial strength and fiber orientation having influence on ultimate strength, and debonding damage being an important factor causing eventually failure.