The Initial Post-buckling Behavior of Face-Sheet Delaminations in Sandwich Composites

2003 ◽  
Vol 70 (2) ◽  
pp. 191-199 ◽  
Author(s):  
G. A. Kardomateas ◽  
H. Huang
Keyword(s):  
Interface Crack ◽  
Transverse Shear ◽  
Compressive Strain ◽  
Sandwich Beam ◽  
Local Buckling ◽  
Face Sheet ◽  
Material System ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Composite Face

Should an interface crack between the layers of the composite face-sheet or between the core and the composite face-sheet of a sandwich beam/plate exists, local buckling and possible subsequent growth of this interface crack (delamination) may occur under compression. In this study, the buckling, and initial post-buckling behavior is studied through a perturbation procedure that is based on the nonlinear beam equations with transverse shear included. Closed-form solutions for the load and midpoint delamination deflection versus applied compressive strain during the initial postbuckling phase are derived. Illustrative results are presented for several sandwich construction configurations, in particular with regard to the effect of material system and transverse shear.

Postbuckling and Growth Behavior of Face-Sheet Delaminations in Sandwich Composites

1999 ◽  
Author(s):  
George A. Kadomateas
Keyword(s):  
Interface Crack ◽  
Tensile Force ◽  
Sandwich Beam ◽  
Local Buckling ◽  
Compressive Force ◽  
Growth Behavior ◽  
Face Sheet ◽  
Large Deflections ◽  
Bending Load ◽  
Composite Face

Abstract A bending load on a sandwich beam consisting of two fiber-reinforced sheets (skins) separated by a low stiffness core is equivalent to a compressive force on one face and a tensile force on the other. Should an interface crack between the layers of the composite face-sheet or between the core and the composite face-sheet exists on the compressively loaded face, local buckling and subsequently growth of this interface crack (delamination) may occur. This may also naturally occur under pure compression. In this study, the buckling, postbuckling and delamination growth behavior is studied through a procedure that is based on the large deflections of the delaminated layer. First, the solution is derived for the postbuckled states by using the elastica theory to model the large deflections of the thin delaminated layer and the sandwich beam theory (for unsymmetric sections) that includes transverse shear, to model the (relatively modest) deflections of the rest of the structure. This postbuckling solution is subsequently used to study the growth of the mixed mode interface crack through an energy release rate approach. The consequences of the elastic mismatch between core and face sheet are discussed and illustrative results are presented for several sandwich construction configurations.

Local Buckling Behavior of 48″, X80 High-Strain Line Pipes

2010 ◽  
Author(s):  
Nobuhisa Suzuki ◽  
Hisakazu Tajika ◽  
Satoshi Igi ◽  
Mitsuru Okatsu ◽  
Joe Kondo ◽  
...  
Keyword(s):  
High Strain ◽  
Compressive Strain ◽  
Local Buckling ◽  
Bending Test ◽  
Test Results ◽  
Geometric Properties ◽  
Pipe Surface ◽  
Bending Tests ◽  
Buckling Behavior ◽  
Post Buckling

Two bending tests of X80-grade, 48″ high-strain line pipes pressurized to 60% SMYS were conducted to investigate local buckling behavior. The thickness and D/t ratio of the line pipes were 22.0 mm and 55.4, respectively. The mean Y/T ratio of the high-strain pipes was 0.82. A full-scale bending test apparatus was constructed to conduct the bending tests. The bending test results clarified that the pipes have the 2D average critical compressive strain of 1.51 and 1.67%, which satisfy the strain demand of 1.35%. Validation of FEA is conducted taking into account geometric properties of the pipes in terms of outside diameter and thickness and longitudinal flatness. The FEA results coincide with the test results with respect to peak load, critical displacement, critical rotation and critical compressive strain. The FEA results about the load and displacement relationship also show good agreement with the test results during post-buckling deformation. One developed wrinkle and some small wrinkles were observed on the pipe surface during post-buckling deformation, whose cross sections were fairly captured considering the geometric properties.

Delamination Suppression in Sandwich Beams Using Translaminar Reinforcements

1999 ◽  
Author(s):  
Brian T. Wallace ◽  
Bhavani V. Sankar ◽  
Peter G. Ifju
Keyword(s):  
Axial Compression ◽  
Sandwich Beam ◽  
Sandwich Beams ◽  
Thickness Direction ◽  
Compression Tests ◽  
Honeycomb Core ◽  
Element Analysis ◽  
Buckling Loads ◽  
Buckling Behavior ◽  
Post Buckling

Abstract The present study is concerned with translaminar reinforcement in a sandwich beam for preventing buckling of a delaminated face-sheet under axial compression. Graphite/epoxy pins are used as reinforcement in the thickness direction of sandwich beams consisting of graphite/epoxy face-sheets and a Aramid honeycomb core. Compression tests are performed to understand the effects of the diameter of the reinforcing pins and reinforcement spacing on the ultimate compressive strength of the delaminated beams. A finite element analysis is performed to understand the effects of translaminar reinforcement on the critical buckling loads and post-buckling behavior of the sandwich beam under axial compression.

Experimental and numerical study of buckling behavior of foam-filled honeycomb core sandwich panels considering viscoelastic effects

2020 ◽  
pp. 109963622097516
Author(s):  
M Safarabadi ◽  
M Haghighi-Yazdi ◽  
MA Sorkhi ◽  
A Yousefi
Keyword(s):  
Energy Absorption ◽  
Viscoelastic Properties ◽  
Sandwich Panel ◽  
Sandwich Panels ◽  
Face Sheet ◽  
Honeycomb Core ◽  
Buckling Behavior ◽  
Foam Filling ◽  
Foam Filled ◽  
Composite Face

Honeycomb sandwich panels are widely used in marine, aerospace, automotive and shipbuilding industries. High strength to weight and excellent energy absorption are features that make these structures unique. Foam filling the honeycomb core enhances the mechanical properties of sandwich panels considerably. In the present study, the buckling behavior of Nomex honeycomb core/glass-epoxy face sheet sandwich panel for both bare and foam-filled honeycomb core is investigated numerically and experimentally, considering the viscoelastic properties of the sandwich panel. Indeed, the viscoelastic properties of the composite face sheet and foam are determined by relaxation test and are implemented in ABAQUS using VUmat code. The finite element method is also performed using ABAQUS to model the buckling behavior of the sandwich panel incorporating both elastic and viscoelastic material behaviour. The effects of composite face sheet lay-up, core thickness, core cell size, and foam filling are also evaluated. The experimental and numerical results show that the foam increases the critical buckling load and energy absorption.

Investigations on the Local Buckling Response of High Strength Linepipe

2008 ◽  
Author(s):  
Ali Fatemi ◽  
Shawn Kenny ◽  
Millan Sen ◽  
Joe Zhou ◽  
Farid Taheri ◽  
...  
Keyword(s):  
Large Scale ◽  
Local Buckling ◽  
High Strength ◽  
Order Effects ◽  
Geometric Imperfections ◽  
Mesh Topology ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Element Simulator ◽  
Experimental Response

A numerical modeling procedure was developed, using the finite-element simulator ABAQUS/Standard, to predict the local buckling and post-buckling response of high strength pipelines subject to combined state of loading. The numerical procedures were calibrated using test data from large-scale experiments examining the local buckling of high strength linepipe. The numerical model’s response was consistent with the measured experimental response for predicting the local buckling behavior well into the post-yield range. A parametric study was conducted that examined element selection, mesh topology, second-order effects, geometric imperfections and material properties. The results from this study are presented.

End Boundary Effects on Local Buckling Response of High Strength Linepipe

2010 ◽  
Author(s):  
Ali Fatemi ◽  
Shawn Kenny ◽  
Farid Taheri ◽  
Da-Ming Duan ◽  
Joe Zhou
Keyword(s):  
Finite Element ◽  
Yield Stress ◽  
Large Scale ◽  
Stress Ratio ◽  
Compressive Strain ◽  
Local Buckling ◽  
High Strength ◽  
End Effects ◽  
Industry Practice ◽  
Post Buckling

In this paper, the significance of the length to diameter ratio (L/D) on the local buckling response was evaluated using continuum finite element modelling procedures. A numerical model was developed, using the finite-element simulator ABAQUS/Standard, to predict the local buckling and post-buckling response of high strength pipelines subject to combined state of loading. The numerical procedures were calibrated using test data from large-scale experiments examining the local buckling of high strength linepipe. The numerical model’s response was consistent with the measured experimental response for predicting the local buckling behavior well into the post-yield range. A parametric study was conducted to examine the significance of the linepipe L/D ratio with respect to the yield stress to ultimate stress ratio (Y/T) and hoop yield stress to longitudinal yield stress ratio or anisotropy factor (R). As the models with high L/D ratio exhibit global Euler-type response, a numerical algorithm was developed to calculate the local section moment response for the FE analysis. The analysis conducted provides insight on the significance of end effects on the local buckling response. There are questions on the approach taken by current industry practice with respect to establishing compressive strain limits for local buckling when using shorter linepipe segment lengths. The results from this study suggest end effects require assessment and potential mitigation.

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.

Full-Scale Tests of Cold Bend Pipes

2004 ◽  
Author(s):  
M. Sen ◽  
J. J. R. Cheng ◽  
D. W. Murray ◽  
J. Zhou ◽  
K. Adams ◽  
...  
Keyword(s):  
Compressive Strain ◽  
Local Buckling ◽  
Full Scale ◽  
Combined Loading ◽  
Experimental Program ◽  
Test Procedures ◽  
Buckling Behavior ◽  
Residual Strains ◽  
Full Scale Tests ◽  
Bend Angles

An experimental program sponsored jointly by SNAM Rete Gas, Tokyo Gas Co., Ltd. and TransCanada Pipelines Ltd. was conducted on cold bend pipes under combined loading. These tests were designed to study the local buckling behavior and to develop the critical compressive strain criteria for cold bend pipes under combined loading. The test program includes eight full-scale specimens of NPS24 and NPS30 pipes with pipe thickness up to 14.3 mm. The test parameters include different D/t ratios (44, 69, and 93), material grades (X60, X65, and X80), bend angles (1.0 to 1.5 degree/diameter), and operation pressures (0%, 40%, 60%, and 80% of SMYS). In addition to full-scale tests, initial imperfections and residual strains due to cold bend processes were also measured. This paper describes the test specimens, test setup, instrumentation, and test procedures used in the program. A brief discussion of the test results is also covered in the paper.

Stability Analysis of Floating-Roof Tanks under Differential Settlement

2010 ◽  
Vol 163-167 ◽  
pp. 55-60
Author(s):  
Yang Zhao ◽  
Xiang Lei ◽  
Xing Zhang
Keyword(s):  
Local Buckling ◽  
Structural Response ◽  
Nonlinear Behavior ◽  
Differential Settlement ◽  
Tank Wall ◽  
Buckling Behavior ◽  
Steel Tanks ◽  
Post Buckling ◽  
Cylindrical Steel Tanks ◽  
Cylindrical Steel

Vertical cylindrical steel tanks are sensitive to differential settlement beneath the tank wall. Most previous studies were based on idealized harmonic settlement, however, for thin shell structures of high nonlinear behavior, it is obviously inappropriate to obtain the results under real settlement by simple summation of harmonic solutions. Real settlement of steel tanks can be grouped into two types - global differential settlement and local differential settlement. This paper examines the nonlinear response and stability behavior of floating-roof steel tanks under both types of settlement. It is shown that, for tanks under global differential settlement, local buckling occurs at the eave ring, followed by a stable post-buckling behavior, and final failure is by overall buckling of the tank shell; while for tanks under local differential settlement, the structural response is related to the degree of localization. At highly localized settlement, local snap-through buckling occurs at the tank wall, but it does not lead to a serious consequence, and the post-buckling behavior can also be utilized in design.

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