Impact of finite element idealisation on the prediction of welded fuselage stiffened panel buckling

Abstract

Abstract:Lap joints are widely used in the manufacture of stiffened panels and influence local panel sub-component stability, defining buckling unit dimensions and boundary conditions. Using the Finite Element method it is possible to model joints in great detail and predict panel buckling behaviour with accuracy. However, when modelling large panel structures such detailed analysis becomes computationally expensive. Moreover, the impact of local behaviour on global panel performance may reduce as the scale of the modelled structure increases. Thus this study presents coupled computational and experimental analysis, aimed at developing relationships between modelling fidelity and the size of the modelled structure, when the global static load to cause initial buckling is the required analysis output. Small, medium and large specimens representing welded lap-joined fuselage panel structure are examined. Two element types, shell and solid-shell, are employed to model each specimen, highlighting the impact of idealisation on the prediction of welded stiffened panel initial skin buckling.

Mechanical response of a panel section with a hexagonally tessellated stiffener grid

“…22 Analytical validation, Flugge. Stress results from the finite element model of the OGSP are compared with Flugge's analytical expressions (7). The stress data are sampled at select locations in the longitudinal and circumferential directions shown in Figure 9.…”

“…The longitudinal and tangential stresses in the skin collected at select locations are compared with those predicted from Flugge's equation (7); the percent error levels ranged from 0.09% to 8% with a median value of 6.2%. The model predicts the tangential components of the stress with low error levels; a comparison of the finite element results with theory is presented in the chart of Figure 10 for the axial and tangential components of the stress in the skin at the selected locations; it can be seen that the errors are within acceptable limits.…”

“…Examples of grid stiffened designs include isogrids, anisogrids, regular hexagonal grid, etc. 3,6,7 The study of buckling of grid stiffened shells is well established; recently, Boni and Fanteria developed an analytical method for fuselage design validated through finite element models. 8,9 Vasiliev et al [3][4][5] conducted several experimental studies and designs of operative anisogrid structures in composite materials.…”