DESIGN AND ANALYSIS OF THERMOPLASTIC WELDED STIFFENED PANELS IN POST-BUCKLING

2021 ◽  
Author(s):  
KEVIN S. VAN DOOREN ◽  
CHIARA BISAGNI
Keyword(s):  
Boundary Conditions ◽  
Lower Half ◽  
Aerospace Engineering ◽  
Structural Behavior ◽  
Next Generation ◽  
Stiffened Panels ◽  
University Of Technology ◽  
Post Buckling ◽  
Manufacturing Techniques ◽  
Separation Behavior

The Clean Sky 2 “SmarT mUlti-fuNctioNal and INtegrated TP fuselaGe" STUNNING project focusses on the next generation composite fuselage with emphasis on manufacturing techniques such as thermoplastic welding. Welded multi-stringer panels are investigated in this paper, with emphasis on the buckling and skin-stringer separation behavior. The multi-stringer panels are designed to approximate the structural behavior of the lower half of the MultiFunctional Fuselage Demonstrator of the STUNNING project. In particular, a section of the fuselage is analyzed using Abaqus with a dynamic implicit analysis, and the results of this analysis are used for the design of the multi-stringer panels, taking manufacturing considerations also into account. The panels have three omega stringers and a length of 500 mm. The three stringer configuration allows to study the middle stringer in pristine and damaged configuration with minimal influence of the free edges and boundary conditions. It is seen that the multi-stringer test panels show very similar buckling and skin-stringer separation behavior compared to the fuselage section. The first panels have been manufactured by project partners NLR and GKN Aerospace Fokker and will be tested at the Faculty of Aerospace Engineering at Delft University of Technology.

The Effect of Stitching on Compression Behavior of Stiffened Composite Panels

2001 ◽  
Author(s):  
Sung S. Suh ◽  
H. Thomas Hahn ◽  
Nanlin Han ◽  
Jenn-Ming Yang
Keyword(s):  
Beneficial Effect ◽  
Compression Behavior ◽  
Stiffened Panels ◽  
Shell Elements ◽  
Stitch Density ◽  
Stiffened Composite Panels ◽  
Out Of Plane ◽  
Post Buckling ◽  
Post Impact ◽  
Good Agreement

Abstract Failure of stiffened panels under compression is preceded by buckling of their skin and hence is affected by the presence of out-of-plane stresses. One of the promising methods of preventing premature delamination is stitching. The present paper discusses the effect of such stitching on compression behavior of blade-stiffened panels that were fabricated from plain weave AS4/3501-6 through resin film infusion process. Kevlar 29 yarn was used at a stitch density of 9.92 stitches per cm2. Some of the panels were damaged by drop-weight impact before compression testing. For comparison purposes unstitched panels with the same materials and dimensions were also tested under the same loading conditions. Stitching resulted in a 10% improvement in strength in the absence of any intentional damage. The beneficial effect of stitching was most obvious when the panels were impacted on a flange: a 50% improvement was observed in post-impact strength. However, stitching could not prevent stiffener from failure when impacted directly. Thus stitching had no beneficial effect when impact occurred on a stiffener. A buckling and post-buckling analysis was carried out using 3-D shell elements on the Abaqus. Predictions were in fairly good agreement with the experimental data.

Standardization of Three Efficient Footbridges: Von Mises, Monocontentio and Bicontentio Prototypes.

2021 ◽  
Author(s):  
Mario Guisasola
Keyword(s):  
Boundary Conditions ◽  
Structural Characteristics ◽  
Structural Behavior ◽  
Bending Moments ◽  
Variable Depth ◽  
Constant Depth ◽  
Simply Supported ◽  
Vertical Walls ◽  
Basic Concepts ◽  
Von Mises

<p>The Von Mises, Monocontentio and Bicontentio footbridges are three parameterized metal bridge whose main structural characteristics are their variable depth depending on the applied stress and the embedding of abutments. Its use is considered suitable for symmetrical or asymmetrical topographies with slopes or vertical walls on one or both edges. The footbridges include spans spaced apart by 20 to 66 meters, and are between 2 to 4.5 meters wide.</p><p>Its design is based on five basic concepts: integration in the geometry of the environment; continuous search for simplicity; design based on a geometry that emanates from structural behavior; unitary and round forms; and long- lasting details.</p><p>The structural behavior of these prototypes has been compared with three types of constant-depth metal beams: the bridge simply supported, and the bridge embedded on one or both sides.</p><p>The embedding of abutments, and the adoption of a variation of depth adapted to the bending moments diagrams, allow for more efficient and elegant forms which are well-adapted to the boundary conditions.</p>

Numerical Study of the Effect of Geometry and Boundary Conditions on the Collapse Behaviour of Stocky Stiffened Panels

2012 ◽  
Vol 154 (A2) ◽  
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Ultimate Strength ◽  
Material Properties ◽  
Finite Element Modelling ◽  
Numerical Study ◽  
Fe Analysis ◽  
Stiffened Panels ◽  
Element Modelling ◽  
Geometric Configurations

This study aims at studying different configurations of the stiffened panels in order to identify robust configurations that would not be much sensitive to the imprecision in boundary conditions that can exist in experimental set ups. A numerical study is conducted to analyze the influence of the stiffener’s geometry and boundary conditions on the ultimate strength of stiffened panels under uniaxial compression. The stiffened panels with different combinations of mechanical material properties and geometric configurations are considered. The four types of stiffened panels analysed are made of mild or high tensile steel and have bar, ‘L’ and ‘U’ stiffeners. To understand the effect of finite element modelling on the ultimate strength of the stiffened panels, four types of FE models are investigated in FE analysis including 3 bays, 1/2+1+1/2 bays, 1+1 bays and 1 bay with different boundary conditions.

Post-Buckling Analysis of Heavy Columns with Application to Marine Risers

1985 ◽  
Vol 29 (03) ◽  
pp. 162-169
Author(s):  
Theodore Kokkinis ◽  
Michael M. Bernitsas
Keyword(s):  
Boundary Conditions ◽  
Small Strain ◽  
Equilibrium Path ◽  
Drilling Mud ◽  
Tubular Columns ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Combined Action ◽  
Raphson Iteration ◽  
Good Agreement

The post-buckling behavior of heavy tubular columns following static instability under the combined action of weight, tension/compression at the top, and fluid static pressure forces in the gravity field is studied. A two-dimensional nonlinear small-strain large-deflection model of the column is derived, consisting of an integrodifferential equilibrium equation and two end rotation conditions. The equation of equilibrium is discretized using a finite-element method. An approximate solution valid in the neighborhood of the bifurcation point and an incremental solution are used to determine the secondary equilibrium path. The results of both methods are corrected by Newton-Raphson iteration. Conditions for unstable initial post-buckling behavior and existence of limit points on the secondary equilibrium path are presented. The numerical solution is applied to the problem of the elastica and is found to be in good agreement with the analytical solution. The secondary equilibrium path for a 500-m-long (1640 ft) marine drilling riser is calculated for two sets of boundary conditions and various values of the drilling mud density. The effect of the drilling mud density and the boundary conditions on the riser's post-buckling behavior is discussed.

scholarly journals Modified Fourier–Galerkin Solution for Aerospace Skin-Stiffener Panels Subjected to Interface Force and Mixed Boundary Conditions

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2794
Author(s):  
Renluan Hou ◽  
Qing Wang ◽  
Jiangxiong Li ◽  
Yinglin Ke
Keyword(s):  
Boundary Conditions ◽  
Mixed Boundary ◽  
Beam Theory ◽  
Mixed Boundary Conditions ◽  
Combined Loading ◽  
Maximum Deviation ◽  
Concentrated Force ◽  
Stiffened Panels ◽  
Deformation Equation ◽  
Functional Boundary

Aeronautical stiffened panels composed of thin shells and beams are prone to deformation or buckling due to the combined loading, functional boundary conditions and interface forces between joined parts in the assembly processes. In this paper, a mechanical prediction model of the multi-component panel is presented to investigate the deformation propagation, which has a significant effect on the fatigue life of built-up structures. Governing equations of Kirchhoff–Love shell are established, of which displacement expressions are transformed into Fourier series expansions of several introduced potential functions by applying the Galerkin approach. This paper presents an intermediate quantity, concentrated force at the joining interface, to describe mechanical interactions between the coupled components. Based on the Euler–Bernoulli beam theory, unknown intermediate quantity is calculated by solving a 3D stringer deformation equation with static boundary conditions specified on joining points. Compared with the finite element simulation and integrated model, the proposed method can substantially reduce grid number without jeopardizing the prediction accuracy. Practical experiment of the aircraft panel assembly is also performed to obtain the measured data. Maximum deviation between the experimental and predicted clearance values is 0.193 mm, which is enough to meet the requirement for predicting dimensional variations of the aircraft panel assembly.

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