scholarly journals Geometric Nonlinearity Effects in the Response of Sandwich Wide Panels

2016 ◽  
Vol 83 (9) ◽  
Author(s):  
Zhangxian Yuan ◽  
George A. Kardomateas ◽  
Yeoshua Frostig
Keyword(s):  
Geometric Nonlinearity ◽  
Sandwich Panel ◽  
Hard Core ◽  
Order Theory ◽  
High Order ◽  
Three Point Bending ◽  
The Core ◽  
Nonlinear Version ◽  
Simplifying Assumptions ◽  
Nonlinear High Order

In the literature, there are various simplifying assumptions adopted in the kinematic relations of the faces and the core when considering a geometrically nonlinear problem in sandwich structures. Most commonly, only one nonlinear term is included in the faces and the core nonlinearities are neglected. A critical assessment of these assumptions, as well as the effects of including the other nonlinear terms in the faces and the core, is the scope of this paper. The comprehensive investigation of all the nonlinear terms is accomplished by deriving and employing an advanced nonlinear high-order theory, namely, the recently developed “extended high-order sandwich panel theory” (EHSAPT). This theory, which was derived as a linear theory, is first formulated in this paper in its full nonlinear version for the simpler one-dimensional case of sandwich wide panels/beams. Large displacements and moderate rotations are taken into account in both faces and core. In addition, a nonlinear EHSAPT-based finite element (FE) is developed. A series of simplified models with various nonlinear terms included are derived accordingly to check the validity of each of these assumptions. Two sandwich panel configurations, one with a “soft” and one with a “hard” core, loaded in three-point bending, are analyzed. The geometric nonlinearity effects and the relative merits of the corresponding simplifications are analyzed with these two numerical examples. In addition to a relative comparison among all these different assumptions, the results are also compared to the corresponding ones from a commercial FE code.

scholarly journals Extended High-Order Theory for Curved Sandwich Panels and Comparison With Elasticity

2017 ◽  
Vol 84 (8) ◽  
Author(s):  
Nunthadech Rodcheuy ◽  
Yeoshua Frostig ◽  
George A. Kardomateas
Keyword(s):  
Sandwich Panel ◽  
Order Theory ◽  
Theory Of Elasticity ◽  
High Order ◽  
Transverse Load ◽  
Radial Coordinate ◽  
Elasticity Solution ◽  
Displacement Fields ◽  
The Core ◽  
Curved Panels

A new one-dimensional high-order sandwich panel theory for curved panels is presented and compared with the theory of elasticity. The theory accounts for the sandwich core compressibility in the radial direction as well as the core circumferential rigidity. Two distinct core displacement fields are proposed and investigated. One is a logarithmic (it includes terms that are linear, inverse, and logarithmic functions of the radial coordinate). The other is a polynomial (it consists of second and third-order polynomials of the radial coordinate), and it is an extension of the corresponding field for the flat panel. In both formulations, the two thin curved face sheets are assumed to be perfectly bonded to the core and follow the classical Euler–Bernoulli beam assumptions. The relative merits of these two approaches are assessed by comparing the results to an elasticity solution. The case examined is a simply supported curved sandwich panel subjected to a distributed transverse load, for which a closed-form elasticity solution can be formulated. It is shown that the logarithmic formulation is more accurate than the polynomial especially for the stiffer cores and for curved panels of smaller radius.

Blast Response of a Sandwich Beam/Wide Plate Based on the Extended High-Order Sandwich Panel Theory and Comparison With Elasticity

2013 ◽  
Vol 80 (6) ◽  
Author(s):  
Catherine N. Phan ◽  
George A. Kardomateas ◽  
Yeoshua Frostig
Keyword(s):  
Sandwich Panel ◽  
Linear Problem ◽  
Sandwich Beam ◽  
Solution Procedure ◽  
High Order ◽  
The Core ◽  
Blast Response ◽  
Nonlinear Version ◽  
Dynamic Version ◽  
Dynamic Phenomena

This paper presents a one-dimensional analysis for the blast response of a sandwich beam/wide plate with a compressible core. The dynamic version of the recently developed extended high-order sandwich panel theory (EHSAPT) is first formulated. Material, geometric, and loading parameters are taken from blast experiments reported in literature. The novelty of EHSAPT is that it includes axial rigidity of the core and allows for three generalized coordinates in the core (the axial and transverse displacements at the centroid of the core and the rotation at the centroid of the core) instead of just one (shear stress in the core) of the earlier high-order sandwich panel theory (HSAPT). The solution procedure to determine the dynamic response to a general load applied on the top face sheet of a general asymmetric simply supported configuration is outlined. Although the dynamic EHSAPT is formulated in its full nonlinear version, the solution is for the linear problem so the accuracy of EHSAPT, along with the other theories, can be assessed by comparison to an available dynamic elasticity solution. Results show that the EHSAPT is very accurate and can capture the complex dynamic phenomena observed during the initial, transient phase of blast loading.

Shear-Lag Effect in Sandwich Panels With Stiffeners Under Three-Point Bending

1980 ◽  
Vol 47 (2) ◽  
pp. 383-388 ◽  
Author(s):  
K. Kemmochi ◽  
T. Akasaka ◽  
R. Hayashi ◽  
K. Ishiwata
Keyword(s):  
Strain Distribution ◽  
Sandwich Panel ◽  
Sandwich Panels ◽  
Bending Rigidity ◽  
Shear Lag ◽  
Shear Lag Effect ◽  
Three Point Bending ◽  
The Core ◽  
Lag Effect ◽  
Modified Theory

In this paper, a modified theory based upon Reissner’s procedure for the shear-lag effect of the sandwich panel is presented, which includes the effects of the anisotropy of the faces and the shearing rigidity of the core. In order to verify this theory, bending experiments were performed with sandwich panels composed of a soft core, stiffeners, and orthotropic faces. It was found that the effective bending rigidity calculated from this theory was lower than that derived from the classical bending theory and that the theoretical strain distribution on the faces agreed well with the experimental results.

Geometrical nonlinear thermal response of sandwich panels with temperature dependent mechanical properties—Extended high-order approach

2019 ◽  
Vol 21 (5) ◽  
pp. 1700-1725 ◽  
Author(s):  
Yeoshua Frostig ◽  
George Kardomateas
Keyword(s):  
Mechanical Properties ◽  
Sandwich Panel ◽  
Mechanical Response ◽  
Numerical Study ◽  
Thermal Response ◽  
High Order ◽  
Theory Approach ◽  
Temperature Dependent ◽  
The Core ◽  
Compressive Loads

The thermal and the thermo-mechanical responses of a sandwich panel with a compliant core are investigated within the framework of the extended high-order approach where the core properties are temperature dependent or independent. Loads schemes include thermal field within temperature working range simultaneous with in-plane compressive loads applied to the core only and to the face sheets and core in the form of the uniform end—shortening of edge of panel. The mathematical formulations use the extended high-order sandwich panel theory approach that takes into account the in-plane rigidity of the core and uses the deformation patterns of the high-order sandwich panel theory. The linear and nonlinear field equations along with the appropriate boundary conditions are presented. A numerical study is conducted, and it investigates the thermal response with temperature independent and temperature dependent mechanical properties of the core as well as the thermo-mechanical response due to in-plane compressive loads. The results include displacements, stress resultants, and stress at critical locations along the panel as well as equilibria curves. They reveal that, in general, the panel with temperature independent properties response remains almost linear while with temperature dependent ones it takes a general nonlinear response. The addition of an external mechanical load changes the response from a linear/nonlinear one that may be allowable stress controlled to a case where loss of stability occurs.

Dynamic pulse buckling and failure analysis of the single curved composite sandwich panel using the core high-order theory

2020 ◽  
Vol 234 (10) ◽  
pp. 1990-2011
Author(s):  
Seyed Ali Ahmadi ◽  
Mohammad Hadi Pashaei ◽  
Ramazan-Ali Jafari-Talookolaei
Keyword(s):  
Sandwich Panel ◽  
Failure Modes ◽  
Viscoelastic Model ◽  
Sandwich Panels ◽  
High Order ◽  
Foam Core ◽  
Composite Sandwich ◽  
The Core ◽  
Pulse Buckling ◽  
Dynamic Pulse

The current study aims to investigate the facesheet dynamic pulse buckling of simply supported, cylindrical composite sandwich panels using the Budiansky–Roth buckling criterion. The foam core has been modeled with isotropic elastic-perfectly plastic properties and various failure modes of the sandwich panel like facesheet fracture, foam shear fracture, and foam yield are investigated. The extended high-order sandwich panel core theory was used to model the compressibility of the core. To study the mechanical properties of the viscoelastic foam core, the Kelvin–Voigt linear viscoelastic model was applied. The transient responses and stress components obtained from the present method are compared with finite element solutions using commercial software ANSYS and those reported in the literature. Accordingly, reasonable agreement is observed. It was shown that the pulse local buckling strength of the panel increases with a decrease in the panel radius or an increase in the thickness of the panel, and facesheet fracture is considered more a likely failure mode of these sandwich panels.

Analysis of Sandwich Beams With a Compliant Core and With In-Plane Rigidity—Extended High-Order Sandwich Panel Theory Versus Elasticity

2012 ◽  
Vol 79 (4) ◽  
Author(s):  
Catherine N. Phan ◽  
Yeoshua Frostig ◽  
George A. Kardomateas
Keyword(s):  
Sandwich Panel ◽  
High Order ◽  
Numerical Results ◽  
The Other ◽  
Transverse Displacement ◽  
Sandwich Beams ◽  
Elasticity Solution ◽  
Transverse Coordinate ◽  
The Core ◽  
Wide Range

A new one-dimensional high-order theory for orthotropic elastic sandwich beams is formulated. This new theory is an extension of the high-order sandwich panel theory (HSAPT) and includes the in-plane rigidity of the core. In this theory, in which the compressibility of the soft core in the transverse direction is also considered, the displacement field of the core has the same functional structure as in the high-order sandwich panel theory. Hence, the transverse displacement in the core is of second order in the transverse coordinate and the in-plane displacements are of third order in the transverse coordinate. The novelty of this theory is that it allows for three generalized coordinates in the core (the axial and transverse displacements at the centroid of the core and the rotation at the centroid of the core) instead of just one (midpoint transverse displacement) commonly adopted in other available theories. It is proven, by comparison to the elasticity solution, that this approach results in superior accuracy, especially for the cases of stiffer cores, for which cases the other available sandwich computational models cannot predict correctly the stress fields involved. Thus, this theory, referred to as the “extended high-order sandwich panel theory” (EHSAPT), can be used with any combinations of core and face sheets and not only the very “soft” cores that the other theories demand. The theory is derived so that all core/face sheet displacement continuity conditions are fulfilled. The governing equations as well as the boundary conditions are derived via a variational principle. The solution procedure is outlined and numerical results for the simply supported case of transverse distributed loading are produced for several typical sandwich configurations. These results are compared with the corresponding ones from the elasticity solution. Furthermore, the results using the classical sandwich model without shear, the first-order shear, and the earlier HSAPT are also presented for completeness. The comparison among these numerical results shows that the solution from the current theory is very close to that of the elasticity in terms of both the displacements and stress or strains, especially the shear stress distributions in the core for a wide range of cores. Finally, it should be noted that the theory is formulated for sandwich panels with a generally asymmetric geometric layout.

Static mechanical response of sandwich panels with bilinear core

2018 ◽  
Vol 22 (7) ◽  
pp. 2421-2444
Author(s):  
Guangtao Wei ◽  
Lijia Feng ◽  
Linzhi Wu
Keyword(s):  
Theoretical Model ◽  
Sandwich Structure ◽  
Sandwich Panel ◽  
Mechanical Response ◽  
Constitutive Relations ◽  
Plastic Region ◽  
Sandwich Panels ◽  
High Order ◽  
Isotropic Hardening ◽  
The Core

A new theoretical model based on the extended high order sandwich panel theory is established to predict the mechanical response of sandwich panels under static loads with the bilinear constitutive stress–strain relation in the core. The constitutive relations of normal stresses related to the longitudinal and vertical normal strains in the bilinear isotropic hardening core are first formulated. The influence of the in-plane rigidity on the elastoplastic response of sandwich structures is analyzed. An in-plane loaded sandwich structure with the bilinear core is first studied based on extended high order sandwich panel theory, and the effect of the bilinear ratio on the mechanical response is evaluated. The governing equations are derived from the principle of minimum potential energy, and a Ritz-based half-analytical method is applied to get the solutions. The plastic response is acquired by an iterative procedure along with the convergence criteria. The results reveal that the local effect can be captured when the axial rigidity of the core is considered. The bilinear characteristic of the core decreases the maximum normal stress with an increase of the average value. The equivalent plastic region extends with the increase of the bilinear ratio when the sandwich structure is loaded in plane. By comparison with open literatures and finite element results, the present theoretical model is proved to be effective and efficient.

An Extended Higher-Order Free Vibration Analysis of Composite Sandwich Beam With Viscoelastic Core

2012 ◽  
Author(s):  
Soroush Sadeghnejad ◽  
Mojtaba Sadighi ◽  
Abdolreza Ohadi Hamedani
Keyword(s):  
Free Vibration ◽  
Vibration Analysis ◽  
Sandwich Panel ◽  
Sandwich Beam ◽  
Free Vibration Analysis ◽  
High Order ◽  
Theory Approach ◽  
Composite Sandwich ◽  
The Core ◽  
Viscoelastic Core

Free vibration analysis of sandwich beam with a viscoelastic core based on the extended high-order sandwich panel theory approach is presented. The effects of transverse shear and core compressibility are of high importance in sandwich structures, having an influence on the entire structural behavior especially in vibrations. For applications involving stiffer cores, the high-order sandwich panel theory (HSAPT) cannot accurately predict the shear and axial stress distributions in the core. Thus, by using the “Extended High-Order Sandwich Panel Theory” (EHSAPT), the in-plane rigidity of the core is considered in addition to the compressibility of the core in the transverse direction. The novelty of this theory is that it allows for three generalized coordinates in the core (the axial and transverse displacements at the centroid of the core, and the rotation at the centroid of the core) instead of just one (mid-point transverse displacement) commonly adopted in other available theories. The mathematical formulation uses the Hamilton principle and includes derivation of the governing equations along with the appropriate boundary conditions. The formulation uses the classical thin plate theory for the face sheets and a two-dimensional elasticity theory or equivalent one for the core. In addition, Young modulus, rotational inertia, and kinetic energy of the core are considered and core is assumed as an orthotropic viscoelastic material. The analysis is applicable for any types of loading scheme, localized as well as distributed, and distinguish between loads applied at the upper or the lower face. The obtained results are compared with recent research published by the present authors which was done numerically by using FEM on viscoelastic sandwich beam and the corresponding results of other previous researches. The influence of material properties, face layup and geometry effect on natural frequencies of composite sandwich beams are investigated.

Effect of Strain-Rate on Flexural Behavior of Composite Sandwich Panel

2012 ◽  
Vol 229-231 ◽  
pp. 766-770 ◽  
Author(s):  
Behzad Abdi ◽  
S.S.R. Koloor ◽  
M.R. Abdullah ◽  
Ayob Amran ◽  
Mohd Yazid bin Yahya
Keyword(s):  
Strain Rate ◽  
High Performance ◽  
Sandwich Panel ◽  
Flexural Behavior ◽  
Bending Test ◽  
Complex Deformation ◽  
Three Point Bending ◽  
Composite Sandwich ◽  
The Core ◽  
Important Concern

In the past few decades, Composite Sandwich Panel (CSP) technology significantly influenced the design and manufacturing of high performance structures. Although using CSP increases the reliability of structure, the important concern is to understand the complex deformation and damage evolution process. This study is focused on the mechanical behaviour of CSP under flexural loading condition. A setup of three-point bending test is prepared using three support span of 40, 60 and 80 mm. The loading was controlled by three different displacement rates of 1, 10 and 100 mm per minute to examine the effects of strain-rate on bending behaviour of CSP material. The beam span significantly affects the flexural stiffness of CSP panel. The load-deflection response of the panel shows two different portions, that representing equivalent elastic and plastic regions in both the core and facesheets components of CSP. The non-combustible mineral-filled core appears to be nonlinear in the elastic region, at high loading rate. Consequently the failure occurs as the core/facesheets interface suffers debonding.

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