A critical evaluation of mechanical models for sandwich beams

2012 ◽  
Vol 14 (6) ◽  
pp. 629-654 ◽  
Author(s):  
Daniele Tonelli ◽  
Lorenzo Bardella ◽  
Michele Minelli
Keyword(s):  
Critical Evaluation ◽  
Sandwich Beam ◽  
Order Theory ◽  
Limited Range ◽  
Geometrical Parameters ◽  
Sandwich Beams ◽  
The Core ◽  
Mechanical Models ◽  
Higher Order Theory ◽  
Definition Of

We focus on the description of the stress state of sandwich beams under bending and shear, a non-trivial task if Saint-Venant's principle does not hold, as it is the case if the skins are somewhat stiffer than the core. Each of the analytical structural models available in literature turns out to be accurate for a limited range of relative stiffness between core and skins, or sandwich heterogeneity. For a simply supported sandwich beam subject to uniform transversal load, we evaluate the stress by means of (a) the classical theory relying on the linear cross-section kinematics, appropriate if Saint-Venant's principle holds, (b) the structural theory based on the zig-zag warping (e.g. Krajcinovic D. Sandwich beam analysis. J Appl Mech, Trans ASME 1972; 39(3): 773–778), and (c) the higher-order theory of Frostig et al. (Frostig Y, Baruch M, Vilnay O, et al. High-order theory for sandwich-beam behavior with transversely flexible core. J Eng Mech, Trans ASCE 1992; 118(5): 1026–1043), the latter usually appropriate when the core is much softer than the skins. The results are compared, for several combinations of material and geometrical parameters, with those of finite element simulations in which the sandwich is modelled as a plane stress continuum. This comparison allows us to provide some graphs which can help in selecting the model appropriate for each sandwich heterogeneity. This is accomplished in terms of non-dimensional material and geometrical parameters the sandwich heterogeneity depends on. We identify and discuss two levels of heterogeneity at which one should switch analytical model: one level is related to the validity of Saint-Venant's principle, while the other level is concerned with the definition of antiplane sandwich.

Free Vibration Analysis of Symmetric Sandwich Beams

2017 ◽  
Vol 872 ◽  
pp. 399-404
Author(s):  
Zakaria Ibnorachid ◽  
Khalid El Bikri ◽  
Lhoucine Boutahar
Keyword(s):  
Sandwich Beam ◽  
Free Vibration Analysis ◽  
Core Layer ◽  
Equation Of Motion ◽  
Geometrical Parameters ◽  
Symmetric Vibration ◽  
Materials Properties ◽  
The Core ◽  
Validation Of Results ◽  
Good Agreement

The aim of the present work is to study the linear free symmetric vibration of three-layer sandwich beam using the energy method. The zigzag model is used to describe the displacement field. The theoretical model is based on the top and bottom layers behave as Euler-Bernoulli beams while the core layer as a Timoshenko beam. Based on Hamilton’s principle, the governing equation of motion sandwich beam is obtained in order to calculate the linear frequency parameters. Two types of boundary conditions simple supported-simple-supported (SS-SS) and clamped-clamped (C-C) under the influence of materials properties and geometrical parameters are studied. The validation of results is done by comparing with another studies, which available in the literature and found good agreement between the studies.

Buckling and Postbuckling of Sandwich Beams With Delaminated Faces Based on Higher Order Core Theory

1999 ◽  
Author(s):  
R. F. Li ◽  
Y. Frostig ◽  
G. A. Kardomateas
Keyword(s):  
Nonlinear Distortion ◽  
Variational Principles ◽  
Vertical Direction ◽  
Initial Imperfection ◽  
Order Theory ◽  
Sandwich Beams ◽  
Postbuckling Behavior ◽  
The Core ◽  
Core Theory ◽  
The Face

Abstract Delaminations within the face sheets are often observed when a sandwich structure is exposed to impact loads. The buckling and postbuckling behavior of sandwich beams with delaminated faces is investigated in this work. The governing nonlinear equations, boundary conditions, and continuity conditions are formulated through variational principles. The beam construction consists of upper and lower, metallic or composite laminated symmetric skins, and a soft core of a foam or low strength honeycomb type. A high order theory is used for the core that accounts for the nonlinear distortion of the plane of section of the core and the compressibility in the vertical direction. The delamination considered is an interface crack, in which the substrate includes the transversely flexible core. The case of a debond at one of the skin-core interfaces is also included. The effects of the delamination length and location on the overall and local behavior are examined with an arbitrary initial imperfection.

The effect of interface debonding on flexural behaviour of composite sandwich beams

2018 ◽  
Vol 22 (4) ◽  
pp. 1132-1156 ◽  
Author(s):  
Mohsen Mansourinik ◽  
Fathollah Taheri-Behrooz
Keyword(s):  
Cohesive Zone Model ◽  
Sandwich Beam ◽  
Interface Debonding ◽  
Zone Model ◽  
Nonlinear Behaviour ◽  
Loading Capacity ◽  
Sandwich Beams ◽  
Failure Initiation ◽  
The Core ◽  
Composite Skins

In the current article, the behaviour of sandwich beams with and without initial core–skin debonding is studied under flexural loads through numerical and experimental procedures. Sandwich beams with three different lengths of 100, 180 and 280 mm and two types of composite skin layups of [0/90]2 and [45/–45]2 are fabricated. An initial artificial debonding is created between core and face sheets during manufacturing the flawed sandwich beams. Numerical simulations and experiments of the short- and medium-sized intact beams revealed that the dominant failure mode is foam yielding and crushing. Thus, the composite skins layup sequence has almost no effect on the failure initiation and growth of those beams. However, in the long-sized sandwich beams, the layup sequence changed the load–displacement response of the beams. Moreover, ignoring the nonlinear behaviour of the composite skins caused a remarkable deviation from the experiment. It is shown that sandwich beams with initial debonding placed in tension side had a negligible effect on the loading capacity of the beams, while those on the compression side had remarkable effects. For instance, the ultimate load of the long-sized beam decreased by 56% compared to the intact sandwich beam. Similarly, in the medium-sized beam, the core–skin debonding in the compressive side caused near 20% reduction in the loading capacity compared to the corresponding intact beam. The cohesive zone model and the extended finite element method were utilized successfully to capture crack initiation and propagation between the core–skin interfaces as well as inside the foam core. Acceptable agreement was observed between the experiment and numerical results.

Temperature-Dependent Vibration of Various Types of Sandwich Beams with Porous FGM Layers

2020 ◽  
pp. 2150016
Author(s):  
Mohsen Rahmani ◽  
Sajjad Dehghanpour
Keyword(s):  
Thermal Stresses ◽  
Equations Of Motion ◽  
Functionally Graded ◽  
Geometrical Parameters ◽  
Type I ◽  
Sandwich Beams ◽  
Temperature Dependent ◽  
The Core ◽  
Graded Layers ◽  
Lagrange Strain

By using a high order sandwich beams theory which is modified by considering the transverse flexibility of the core, free vibration characteristics of two models of sandwich beams are studied in this paper. In type-I, functionally graded layers coat a homogeneous core, and in type-II, an FG core is covered by homogeneous face sheets. To increase the accuracy of the model of the FGM properties, even and uneven porosity distributions are applied, and all materials are considered temperature-dependent. Nonlinear Lagrange strain and thermal stresses of the face sheets and in-plane strain of the core are considered. To obtain the governing equations of motion, Hamilton’s principle is used and a Galerkin method is used to solve them for simply supported and clamped boundary conditions. To verify the results of this study, they are compared with the results of literatures. Also, the effect of variation of temperature, some geometrical parameters and porosities on the frequency are studied.

scholarly journals Fundamental Frequency Analysis of Sandwich Beams with Functionally Graded Face and Metallic Foam Core

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Lin Mu ◽  
Guiping Zhao
Keyword(s):  
Fundamental Frequency ◽  
Plate Theory ◽  
Order Theory ◽  
Functionally Graded ◽  
Face Sheet ◽  
Metallic Foam ◽  
Sandwich Beams ◽  
Classical Plate Theory ◽  
The Core ◽  
The Face

This study is interested in assessing a way to analyze fundamental frequency of sandwich beams with functionally graded face sheet and homogeneous core. The face sheet, which is an exponentially graded material (EGM) varying smoothly in the thickness direction only, is composed of a mixture of metal and ceramic. The core which is made of foam metal is homogeneous. The classical plate theory (CPT) is used to analyze the face sheet and a higher-order theory (HOT) is used to analyze the core of sandwich beams, in which both the transverse normal and shear strains of the core are considered. The extended Galerkin method is used to solve the governing equations to obtain the vibration equations of the sandwich beams suitable for numerical analysis. The fundamental frequency obtained by the theoretical model is validated by using the finite element code ABAQUS and comparison with earlier works. The influences of material and geometric properties on the fundamental frequency of the sandwich beams are analyzed.

Navigating an Immersive Narratology

2021 ◽  
pp. 125-141
Author(s):  
Bradley E. Wiggins
Keyword(s):  
News Media ◽  
Critical Evaluation ◽  
Fake News ◽  
Direct Response ◽  
White House ◽  
Objective Truth ◽  
The Core ◽  
Definition Of ◽  
Historical Antecedents

In direct response to the rise in fake news as a socio-cultural and political phenomenon, this article presents an analysis of the factors that may help to explain the reception of fake news. In addition, recent pronouncements made by the Trump White House seem to challenge the nature of an objective truth. An immersive narratology emphasizes that different universes of discourse can intermingle and overlap, with fact and fiction becoming difficult to distinguish in our increasingly mediated lives. A tenable definition of fake news is offered prior to exploring historical antecedents of fake news. Persuasion, construction, immersion, distribution, and polarization represent the core factors that demystify the reception of fake news regardless as to whether an individual believes a story. A concluding discussion offers a critical evaluation of the potential of fake news to augment the news media landscape in the coming years.

scholarly journals Simplified analytical model for tapered sandwich beams using variable stiffness materials

2016 ◽  
Vol 19 (1) ◽  
pp. 3-25 ◽  
Author(s):  
Qing Ai ◽  
Paul M Weaver
Keyword(s):  
Sandwich Beam ◽  
Shear Deformation Theory ◽  
Variable Stiffness ◽  
Axial Stiffness ◽  
Beam Model ◽  
Sandwich Beams ◽  
Element Analysis ◽  
The Core ◽  
The Face ◽  
Potential Energy Method

A simplified layer-wise sandwich beam model to capture the effects of a combination of geometric taper and variable stiffness of the core on the static response of a sandwich beam is developed. In the present model, the face sheets are assumed to behave as Euler beams and the core is modelled with a first-order shear deformation theory. With geometrical compatibility enforced at both upper and lower skin/core interfaces, the beam’s field functions are reduced to only three, namely the extensional, transverse and rotational displacements at the mid-plane of the core. The minimum total potential energy method is used in combination with the Ritz technique to obtain an approximate solution. Geometrically nonlinear effects are considered in the present formulation by introducing von Kármán strains into the face sheets and core. Two types of sandwich beams, uniform and tapered, with different boundary conditions are studied. Results show that the proposed model provides accurate prediction of displacements and stresses, compared to three-dimensional finite element analysis. It is found that due to the axial stiffness variation in the core, displacements of beams and stresses of face sheets and core are significantly affected. The potential design space is shown to be expanded by utilizing variable stiffness materials in sandwich constructions.

Navigating an Immersive Narratology

2017 ◽  
Vol 8 (3) ◽  
pp. 16-29 ◽  
Author(s):  
Bradley E. Wiggins
Keyword(s):  
News Media ◽  
Critical Evaluation ◽  
Fake News ◽  
Direct Response ◽  
White House ◽  
Objective Truth ◽  
The Core ◽  
Definition Of ◽  
Historical Antecedents

In direct response to the rise in fake news as a socio-cultural and political phenomenon, this article presents an analysis of the factors that may help to explain the reception of fake news. In addition, recent pronouncements made by the Trump White House seem to challenge the nature of an objective truth. An immersive narratology emphasizes that different universes of discourse can intermingle and overlap, with fact and fiction becoming difficult to distinguish in our increasingly mediated lives. A tenable definition of fake news is offered prior to exploring historical antecedents of fake news. Persuasion, construction, immersion, distribution, and polarization represent the core factors that demystify the reception of fake news regardless as to whether an individual believes a story. A concluding discussion offers a critical evaluation of the potential of fake news to augment the news media landscape in the coming years.

Static Response of Stiff-Cored Unsymmetric Sandwich Beams

1976 ◽  
Vol 98 (2) ◽  
pp. 391-396 ◽  
Author(s):  
D. K. Rao
Keyword(s):  
Variational Method ◽  
Flexural Rigidity ◽  
Sandwich Beam ◽  
Sandwich Beams ◽  
Static Response ◽  
Simply Supported ◽  
The Core ◽  
Distributed Load ◽  
Very High ◽  
Maximum Stresses

Improved equations governing the deflection of an unsymmetric sandwich beam (which include the effect of extensional and bending rigidities of its stiff core) are derived using a variational method. The effect of face-thickness ratio on the contribution of the core to the overall flexural rigidity is studied. Numerical results for simply supported and fixed-fixed beams subjected to a uniformly distributed load are obtained by using Laplace transforms. These results show that ignoring the bending and extensional effects of a stiff core can cause errors in maximum deflections as high as 20 percent. The corresponding errors in stresses are very high, and they vary from 10 to 150 percent. Hence, it is suggested that the extensional and bending effects of the core should be taken into account when one is interested in calculating the maximum stresses in stiff-cored beams.

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