Buckling, post-buckling and collapse analysis of stiffened composite panels with debonding damage

A strength analysis model was presented to study the buckling and post-buckling analysis of stiffened composite panels subjected to compressive loading by using the nonlinear finite element method. In the model, the debond failure of the adhesive between the skin and stiffener was considered by adding cohesive elements between the shell elements. Quads failure criteria and Hashin failure criteria were 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 equilibrium paths, propagation and catastrophic failure of the structure were simulated in details. The calculated values by the model were well agreed with the measured values. Numerical results show the effectiveness of the model. Parametric studies were conducted to study the effects of geometric parameters of stiffeners, adhesive strength and stacking sequences on the buckling load and compressive strength of stiffened composite panels. The results indicate that the increased sectional moment of inertia and number of stiffeners can improve the buckling load and compressive strength. The transition from instability failure to compression failure exists when the especial number of stiffeners is obtained. Interfacial strength and fiber orientation significantly influence the compressive strength. The debonding damage is an important factor leading to the eventually failure.