Nonlinear Stability Analysis of Sandwich Wide Panels—Part I: Buckling Behavior

2018 ◽  
Vol 85 (8) ◽  
Author(s):  
Zhangxian Yuan ◽  
George A. Kardomateas
Keyword(s):  
Critical Load ◽  
Nonlinear Stability ◽  
Sandwich Panels ◽  
Weak Form ◽  
Nonlinear Static Analysis ◽  
Nonlinear Stability Analysis ◽  
Buckling Mode ◽  
The Core ◽  
Buckling Behavior ◽  
Global Buckling

This is a series of two papers in which the nonlinear stability behavior of sandwich panels is investigated. This part presents the buckling behavior and focuses on the critical load and the buckling mode. The buckling analysis is based on the extended high-order sandwich panel theory (EHSAPT) which takes transverse compressibility and axial rigidity of the core into account. It allows for the interaction between the faces and the core. The geometric nonlinearity, i.e., large displacement with moderate rotation, is considered in both faces and core. The weak form governing equations are derived based on the EHSAPT-based element. Detailed formulations and analysis procedures are provided. It presents a general approach for arbitrary buckling type without decoupling it into isolated global buckling and wrinkling. There are no additional assumptions made about the prebuckling state and buckling mode shape, which are commonly presumed in the literature. In addition, edge effects which are also commonly neglected are included. The prebuckling state is determined via a nonlinear static analysis. Solving an eigenvalue problem yields the critical load and the corresponding eigenvector gives the buckling mode. Sandwich panels with different lengths are studied as examples. Both global buckling and wrinkling are observed. It shows that the axial rigidity of the core has a pronounced effect on both the critical load and the buckling mode.

Nonlinear Stability Analysis of Sandwich Wide Panels—Part II: Postbuckling Response

2018 ◽  
Vol 85 (8) ◽  
Author(s):  
Zhangxian Yuan ◽  
George A. Kardomateas
Keyword(s):  
Continuation Method ◽  
Weak Form ◽  
Arc Length ◽  
Nonlinear Stability Analysis ◽  
Governing Equations ◽  
Buckling Mode ◽  
The Core ◽  
Global Buckling ◽  
Post Buckling ◽  
Branch Switching

The nonlinear post-buckling response of sandwich panels based on the extended high-order sandwich panel theory (EHSAPT) is presented. The model includes the transverse compressibility, the axial rigidity, and the shear effect of the core. Both faces and core are considered undergoing large displacements with moderate rotations. Based on the nonlinear weak form governing equations, the post-buckling response is obtained by the arc-length continuation method together with the branch switching technique. Also, the post-buckling response with imperfections is studied. The numerical examples discuss the post-buckling response corresponding to global buckling and wrinkling. It is found that due to the interaction between faces and core, localized effects may be easily initiated by imperfections after the sandwich structure has buckled globally. Furthermore, this could destabilize the post-buckling response. The post-buckling response verifies the critical load and buckling mode given by the buckling analysis in part I. The axial rigidity of the core, although it is very small compared to that of the faces, has a significant effect on the post-buckling response.

Numerical Analysis of Debonded Honeycomb Sandwich Structure under Compressive Load

2013 ◽  
Vol 658 ◽  
pp. 227-231
Author(s):  
Tao Zhu ◽  
Jin Long Chen ◽  
Wen Ran Gong
Keyword(s):  
Finite Element ◽  
Local Buckling ◽  
Compressive Load ◽  
Sandwich Panels ◽  
Element Model ◽  
Damage Propagation ◽  
Buckling Behavior ◽  
Honeycomb Sandwich ◽  
Global Buckling ◽  
Honeycomb Sandwich Structure

In this paper, the finite element method (FEM) was applied to predict the local buckling behavior and the debond propagation in honeycomb sandwich panels with face-core debond under in-plane compressive load. The finite element model of the sandwich panel was built, the cohesive element was used to model the adhesive between faces and core, the influence of the debond shape and size on the failure mode, critical buckling load and residual compressive strength of the sandwich panels was investigated, the rule of the damage propagation was summarized. The compression strength of the sandwich panels with through-width face-core debond decreases with increasing debond length. For the panels with central circular debond, when the diameter is less than 15mm, the panels will failure by global buckling and the debond will not grow. When the diameter is greater than 15mm, the panels will failure by local buckling and the critical load strongly decreases with increasing debond diameter. In addition, the direction of debond growth is predominantly perpendicular to the applied load.

scholarly journals Buckling Behavior of Non-Retrofitted and FRP-Retrofitted Steel CHS T-Joints

2021 ◽  
Vol 11 (7) ◽  
pp. 3098
Author(s):  
Amin Yazdi ◽  
Maria Rashidi ◽  
Mohammad Alembagheri ◽  
Bijan Samali
Keyword(s):  
Compressive Loading ◽  
Local Buckling ◽  
Buckling Mode ◽  
T Joints ◽  
Hollow Section ◽  
Frp Composite ◽  
Buckling Behavior ◽  
Global Buckling ◽  
Post Buckling ◽  
Circular Hollow Section

This paper aims to investigate the buckling behavior of circular hollow section (CHS) T-joints in retrofitted and non-retrofitted states under axial brace compressive loading. For this purpose, two types of analysis are carried out. The first one is evaluating the critical buckling load in various tubular joints, and the other one is investigating the post-buckling behavior after each buckling mode. More than 180 CHS T-joints with various normalized geometric properties were numerically modeled in non-retrofitted state to compute their governing buckling mode, i.e., chord ovalization, brace local, or global buckling. Then three joints with different buckling modes were selected to be retrofitted by fiber-reinforced polymer (FRP) patches to illustrate the improving effect of the FRP wrapping on the post-buckling performance of the retrofitted joints. In addition, FRP composite failures were investigated. The results indicate that the FRP retrofitting is able to prevent the brace local buckling, and that matrix failure is the most common composite failure in the retrofitted joints.

An Experimental on Honeycomb Core in the Axial Direction under the Quasi-Static Loading

2014 ◽  
Vol 699 ◽  
pp. 405-410
Author(s):  
Alif Zulfakar bin Pokaad ◽  
Md Radzai bin Said ◽  
Fauzi bin Ahmad ◽  
Mohd Nazeri bin Kamaruddin
Keyword(s):  
Elastic Characteristic ◽  
Axial Direction ◽  
Static Response ◽  
Honeycomb Core ◽  
Buckling Mode ◽  
Linear Elastic ◽  
The Core ◽  
Out Of Plane ◽  
Global Buckling ◽  
Aluminum Honeycomb

This paper focuses on the quasi-static response of the aluminum honeycomb core based on an experimental work. The load-compression and energy absorb characteristics of the out-of-plane aluminium honeycomb core are studied for three varieties of the core cell sizes which are 0.01905, 0.0127 and 0.00635 m. The crushing tests were conducted on the Instron machine with a displacement control of 5 mm/min. The initial part in the load-displacement graph shows linear elastic characteristic, followed by a non-linear elastic-plastic regime before it collapses. Based on the observation, the cell sized 0.01905 m shows the global buckling collapse, but the cell sized 0.0127 and 0.00635 m collapse as progressive buckling mode. The cell size 0.00635 m shows highest energy absorption due to it has the highest density and it collapses like the progressive buckling mode compared with the others specimen.

Dynamic Buckling of Cylindrical Shells under Axial Impact in Hamiltonian System

2012 ◽  
Vol 13 (1) ◽  
Author(s):  
Jia-Bin Sun ◽  
Xin-Sheng Xu ◽  
Chee-Wah Lim
Keyword(s):  
Hamiltonian System ◽  
Critical Load ◽  
Impact Load ◽  
Dynamic Buckling ◽  
Inertia Force ◽  
Elastic Cylindrical Shell ◽  
Symplectic Method ◽  
Buckling Mode ◽  
Axial Impact ◽  
Dual Variables

AbstractIn this paper, the dynamic buckling of an elastic cylindrical shell subjected to an axial impact load is analyzed in Hamiltonian system. By employing a symplectic method, the traditional governing equations are transformed into Hamiltonian canonical equations in dual variables. In this system, the critical load and buckling mode are reduced to solving symplectic eigenvalues and eigensolutions respectively. The result shows that the critical load relates with boundary conditions, thickness of the shell and radial inertia force. And the corresponding buckling modes present some local shapes. Besides, the process of dynamic buckling is related to the stress wave, the critical load and buckling mode depend upon the impacted time. This paper gives analytically and numerically some new rules of the buckling problem, which is useful for designing shell structures.

scholarly journals A numerical study of the impact perforation of sandwich panels with graded hollow sphere cores

2021 ◽  
Vol 13 (4) ◽  
pp. 168781402110094
Author(s):  
Ibrahim Elnasri ◽  
Han Zhao
Keyword(s):  
Boundary Conditions ◽  
Hollow Sphere ◽  
Sandwich Panel ◽  
Numerical Study ◽  
Sandwich Panels ◽  
Hopkinson Bar ◽  
Core Density ◽  
The Core ◽  
The Impact ◽  
Force Displacement

In this study, we numerically investigate the impact perforation of sandwich panels made of 0.8 mm 2024-T3 aluminum alloy skin sheets and graded polymeric hollow sphere cores with four different gradient profiles. A suitable numerical model was conducted using the LS-DYNA code, calibrated with an inverse perforation test, instrumented with a Hopkinson bar, and validated using experimental data from the literature. Moreover, the effects of quasi-static loading, landing rates, and boundary conditions on the perforation resistance of the studied graded core sandwich panels were discussed. The simulation results showed that the piercing force–displacement response of the graded core sandwich panels is affected by the core density gradient profiles. Besides, the energy absorption capability can be effectively enhanced by modifying the arrangement of the core layers with unclumping boundary conditions in the graded core sandwich panel, which is rather too hard to achieve with clumping boundary conditions.

scholarly journals Optimal Stability Thresholds in Rotating Fully Anisotropic Porous Medium with LTNE

2021 ◽  
Author(s):  
Florinda Capone ◽  
Maurizio Gentile ◽  
Jacopo A. Gianfrani
Keyword(s):  
Porous Layer ◽  
Nonlinear Stability ◽  
Steady Motion ◽  
Vertical Axis ◽  
Linear Instability ◽  
List Type ◽  
Nonlinear Stability Analysis ◽  
Onset Of Convection ◽  
Anisotropic Porous Medium ◽  
Necessary And Sufficient

Abstract The onset of thermal convection in an anisotropic horizontal porous layer heated from below and rotating about vertical axis, under local thermal non-equilibrium hypothesis is studied. Linear and nonlinear stability analysis of the conduction solution is performed. Coincidence between the linear instability and the global nonlinear stability thresholds with respect to the L2—norm is proved. Article Highlights A necessary and sufficient condition for the onset of convection in a rotating anisotropic porous layer has been obtained. It has been proved that convection can occur only through a steady motion. A detailed proof is reported thoroughly. Numerical analysis shows that permeability promotes convection, while thermal conductivities and rotation stabilize conduction.

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