Papers by Keyword: Stiffened Panels

Abstract: In this paper, a numerical study, on the compressive behaviour of stiffened composite panels with skin-stringer debonding has been carried out. The analysis has been performed by adopting a novel robust (mesh and time step independent) finite elements based numerical model on a single stiffener panel with an artificial debonding. In order to prove the effectiveness of the proposed numerical tool, the results in terms of debonded area growth and compressive load versus applied displacement, have been compared with experimental data available in literature.

Abstract: Stiffened panels are usually the basic structural building blocks of airplanes, vessels and other structures with high requirements of strength-to-weight ratio. They typically consist of a plate with equally spaced longitudinal stiffeners on one side, often with intermediate transverse stiffeners. Large aeronautical and naval parts are primarily designed based on their longitudinal compressive strength. The structural stability of such thin-walled structures, when subjected to compressive loads, is highly dependent on the buckling strength of the structure as a whole and of each structural member. In the present work, a number of modelling and numerical calculations, based on the Finite Element Method (FEM), is carried out in order to predict the ultimate load level when stiffened panels are subjected to compressive solicitations. The simulation models account not only for the elasto-plastic nonlinear behaviour, but also for the residual stresses, material properties modifications and geometrical distortions that arise from Friction Stir Welding (FSW) operations. To construct the model considering residual stresses, their distribution in FSW butt joints are obtained by means of a numerical-experimental procedure, namely the contour method, which allows for the evaluation of the normal residual stress distribution on a specimen section. FSW samples have been sectioned orthogonally to the welding line by wire electrical discharge machining (WEDM). Displacements of the relaxed surfaces are then recorded using a Coordinate Measuring Machine and processed in a MATLAB environment. Finally, the residual stress distribution is evaluated by means of an elastic FE model of the cut sample, using the measured and digitalized out-of-plane displacements as input nodal boundary conditions. With these considerations, the main goal of the present work will then be related to the evaluation of the effect of FSW operations, in the ultimate load of stiffened panels with complex cross-section shapes, by means of realist numerical simulation models.

Abstract: Composite stiffened panels are widely used in the modern aircraft structure with the advantages of light weight, structural efficiency and good crack performance. But the stiffened panels have poor performance at thickness direction, especially for low-velocity impact. First of all, compressive tests were investigated and analyzed for two types of composite stiffened panels, which are integrated specimens and post-impact specimens. And the effect of low-velocity impact to the supporting capacity of composite stiffened panels was researched. Secondly，the finite element model was established to simulate the CAI (Compression After Impact)strength with the equivalent hole method. It is found that the analyze results match the experimental results well. According to the experimental results, structural damage and the maximum load caused by impact energy are scattering. Then the imperfect factors were introduced to reflect the initial imperfection, namely the initial deflection at thickness direction. The effect of different imperfect factors to the maximum load was discussed.

Abstract: Structural design of ships against collision requires prediction of the extent of damage to stiffened plates subjected to impact. In ship structures, stiffened plates are furnished with vertical or horizontal stiffeners to sustain conventional loads such as shearing, bending and local buckling. The consideration of collision in ship structural design is especially important for tankers where accidents may cause serious environmental pollution. In predicting the extent of collision damage, FE modeling of stiffened plates using ABAQUS software is applied to demonstrate different collision scenario. Typical stiffened plates of tankers in service with different configurations of stiffeners are used to examine absorbed energy in each case. The aim of this paper is to examine the stiffener shape that absorbs more deformation energy.