Showing papers in "Journal of Sandwich Structures and Materials in 2006"
TL;DR: In this article, closed-form formulations of two-dimensional higher-order shear deformation theories (HOSTs) for the free vibration analysis of simply supported cross-ply laminated composite and sandwich doubly curved shells are presented.
Abstract: Closed-form formulations of two-dimensional (2D) higher-order shear deformation theories (HOSTs) for the free vibration analysis of simply supported cross-ply laminated composite and sandwich doubly curved shells are presented. The formulation includes the Sander’s theory for doubly curved shells. Two of the HOSTs account for the effects of both transverse shear strains/stresses and the transverse normal strain/stress, while the third includes only the effects of transverse shear deformation. In these developments a realistic parabolic distribution of transverse shear strains through the shell thickness is assumed. The equations of motion are obtained using Hamilton’s principle. Solutions are obtained in closed-form using Navier’s technique and by solving the eigenvalue equations. Numerical results are presented for the natural frequencies of laminated composite and sandwich shallow shells. The closed-form solutions presented herein for laminated composite plates and shells are compared with the available...
95 citations
TL;DR: In this paper, a tutorial on the subject of fatigue of foam and honeycomb core composite sandwich structures is presented, where several different analytical models for predicting the fatigue life of sandwich composites are presented.
Abstract: This article is intended to be a tutorial on the subject of fatigue of foam and honeycomb core composite sandwich structures. First, several different analytical models for predicting the fatigue life of sandwich composites are presented. Then representative publications which have reported on the major failure modes in sandwich beams under dynamic fatigue loading are summarized, along with several related publications dealing with static and impact loading. Papers dealing with the effects of loading frequency, environmental factors, and block loading on the fatigue life of sandwich composites are discussed. Finally, recent research on different types of non-destruction evaluation (NDE) techniques employed for failure investigations during fatigue testing of sandwich structures is reviewed. Conclusions and generalizations that can be drawn from the literature are presented along with discussions of areas in which further research is needed.
70 citations
TL;DR: In this paper, a simple Co isoparametric finite element model based on a higher-order shear deformation theory is presented for the free vibration analysis of isotropic, orthotropic, and layered anisotropic composite and sandwich skew laminates.
Abstract: A simple Co isoparametric finite element model, based on a higher-order shear deformation theory is presented for the free vibration analysis of isotropic, orthotropic, and layered anisotropic composite and sandwich skew laminates. This theory incorporates a realistic nonlinear variation of displacements through the laminate thickness, and eliminates the use of shear correction coefficients. The boundary conditions on the skew edges are imposed through the suitable transformation of element matrices. The accuracy of the present model is demonstrated by comparing with alternative solutions available in the literature. Extensive numerical results are presented for natural frequencies of cross-ply and angle-ply skew laminates with various lamination parameters, skew angles, boundary conditions, and width-to-thickness ratios. New results on skew sandwiches are obtained for different lamination parameters and skew angles.
58 citations
TL;DR: In this paper, the authors investigated the damage characteristics of composite-skinned honeycomb sandwich panels in bending with both hemispherical (HS) and flat-ended (FE) indenters.
Abstract: Damage characteristics of composite-skinned honeycomb sandwich panels in bending are investigated with both hemispherical (HS) and flat-ended (FE) indenters. The thickness of the cross-ply skins va...
57 citations
TL;DR: In this paper, the tension-tension fatigue of closed cell closed cell foams is investigated using a few simple tests to predict the fatigue properties of closed-cell foams.
Abstract: This paper deals with fatigue of closed cell foams. The main idea is to use a few simple tests to predict the tension-tension fatigue properties of foams. The required testing consists of crack propagation rate measurements and one tension-tension fatigue test performed at yield stress for the foam. This data can then be combined to construct a synthetic S-N curve for the foam. Tests on three densities of Divinycell H-grade foam are performed and the results support this approach. Some preliminary results from two densities of Rohacell WF-grade are given as well. Static properties of foams scale with relative density and once this scaling can be obtained through various static tests and the same scaling appears to be valid for both crack propagation rates and fatigue properties of foams. The implication of this is that once the fatigue behaviour of one relative density foam is established, one can predict the fatigue behaviour of all other relative density foams within the same class of materials.
50 citations
TL;DR: In this paper, the energy absorption of an aluminum foam sandwich and a conventional polymer foam sandwich structure is similar for impacts ranging from 5 to 25 J. The polymer foam-based samples exhibit localized damage in the form of skin fracture and core crushing, but with negligible permanent out-of-plane deformation.
Abstract: The energy absorption of an aluminum foam sandwich structure and a conventional polymer foam sandwich structure is similar for impacts ranging from 5 to 25 J. The polymer foam-based samples exhibit localized damage in the form of skin fracture and core crushing, but with negligible permanent out-of-plane deformation. In contrast, the aluminum foam-based samples show little fracture but exhibit extensive out-of-plane deformation radiating from the impact point. This deformation suggests that the impact damage could be more easily detectable in the aluminum foam sandwich structure. Surface strains are lower in the aluminum foam sandwich samples during post-impact loading in a single cantilever beam test, suggesting improved damage tolerance.
45 citations
TL;DR: In this article, a meshless discretization method based on global multiquadric radial basis functions is used for free vibration analysis of composite and sandwich plates, and the results are then compared with analytical and numerical solutions.
Abstract: In this study trigonometric layerwise deformation theory is used for the analysis of free vibration of symmetric composite plates. A meshless discretization method based on global multiquadric radial basis functions is used. The equations of motion and the boundary conditions are derived and interpolated by radial basis functions. This method is applied to the free vibration analysis of composite and sandwich plates. The results are then compared with analytical and numerical solutions. The results show that the use of trigonometric layerwise deformation theory discretized with multiquadrics provides very good solutions for the free vibration of composite and sandwich plates.
40 citations
TL;DR: In this paper, the out-of-plane performance of honeycomb materials for sandwich panels was evaluated. But, the performance was not as good as that of other core materials, such as graphite.
Abstract: Compared to other core materials, honeycomb materials provide impressive mechanical performance for sandwich panels, but with less weight added to the structures. In this article, the out-of-plane ...
40 citations
TL;DR: In this paper, an experimental study of the in-plane compression failure of sandwich panels consisting of glass/epoxy face sheets over a range of PVC foam cores (H45, H100, and H200) and a balsa wood core containing one or two circular or square interfacial debonds is conducted.
Abstract: An experimental study of the in-plane compression failure of sandwich panels consisting of glass/epoxy face sheets over a range of PVC foam cores (H45, H100, and H200) and a balsa wood core containing one or two circular or square interfacial debonds is conducted. For the great majority of the specimens, failure occurred by local buckling of the debonded face sheet followed by rapid debond growth towards the panel edges, perpendicular to the applied load. Panels with the largest debond (10 cm diameter or 9 cm length) displayed some post-buckling strength. Examination of the face and core failure surfaces after total separation showed that the tendency for interface (core/resin) failure increases with increasing core density. It was found that the compression strength strongly decreases with decreasing core stiffness and increasing debond size. The compression strength of panels with H45 core decreased with reduced core thickness. Failure loads for panels with symmetric debonds at both face/core interfaces...
39 citations
TL;DR: In this paper, a comparative study with a finite element based solution free of any kinematic assumptions as well as a qualitative and quantitative assessment of displacement, stress fields, and modal parameters (natural frequency and loss factor) are conducted.
Abstract: For efficiently simulating static and dynamic behaviors of sandwich structures, an accurate kinematic model is essential. This study presents analytical and numerical evaluations of kinematics and theories proposed in the literature. Several types of assumed displacement fields are considered. This article compares and addresses the efficiency, the applicability, and the limits of classical models, higher order models (CLT, FSDT, and HSDT), and zig-zag theories. To achieve this, a comparative study with a finite element based solution free of any kinematic assumptions as well as a qualitative and quantitative assessment of displacement, stress fields, and modal parameters (natural frequency and loss factor) are conducted. The results are presented and discussed for several sandwich beam configurations where the faces and the cores are both isotropic. For these purposes, static (three-point bending test) and dynamic (free vibration) problems are considered.
33 citations
TL;DR: In this paper, the authors present an approach to facilitate comparison and optimization of sandwich material combinations by comparing and optimizing equivalent homogenized sandwich material properties (bending stiffness, density, and c...
Abstract: This article presents an approach to facilitate comparison and optimization of sandwich material combinations. Equivalent homogenized sandwich material properties (bending stiffness, density, and c...
TL;DR: In this article, the face/core debond fracture resistance of sandwich panels consisting of glass fiber/vinylester face sheets over a 155 kg/m 3 end-grain balsa wood core and a 200 kg /m 3 PVC foam core has been examined.
Abstract: The face/core debond fracture resistance of sandwich panels consisting of glass fiber/vinylester face sheets over a 155 kg/m 3 end-grain balsa wood core and a 200 kg/m 3 PVC foam core has been exam
TL;DR: In this paper, a fracture mechanics approach is proposed to determine the residual strength of debonded honeycomb core composite sandwich panels, and asymmetric double cantilever beam sandwich specimens are tested in an asymptotic manner.
Abstract: A fracture mechanics approach is proposed to determine the residual strength of debonded honeycomb core composite sandwich panels. Asymmetric double cantilever beam sandwich specimens are tested in...
TL;DR: In this article, the degenerate shell element is formulated using total Lagrangian and von Karman hypotheses, and the higher-order shear deformation theory is used in the formulation.
Abstract: This article presents the large deformation analysis of piezolaminated smart structures. The degenerate shell element is formulated using total Lagrangian and von Karman hypotheses. Higher-order shear deformation theory is used in the formulation. The finite element equations are derived using energy principles. The electromechanical coupling linear constitutive model given by Tierstien is used in the formulation. The nonlinear equilibrium equations are solved using the Newton–Raphson iterative technique. Numerical studies on the thin and sandwich plates are presented using different boundary and loading conditions. The comparison between the first-order shear deformation theory (FOST) and higher-order shear deformation theory (HOST) has shown that for sandwich plates the HOST model predicts a better response.
TL;DR: In this paper, the authors evaluated the possibility of using modified lower order methods, such as the Bernoulli-Euler or Timoshenko beam theories with frequency dependent parameters, to calculate the response of sandwich beams subject to different end conditions.
Abstract: The purpose of this study is to evaluate the possibility of using modified lower order methods - such as the Bernoulli-Euler or Timoshenko beam theories with frequency dependent parameters - to calculate the response of sandwich beams subject to different end conditions. The models have been verified by measurements on a freely suspended asymmetric sandwich beam with aluminum laminates and a plastic foam core, indicating good agreement.
TL;DR: In this article, the impactor and the panel were modeled with the help of the system having three-degrees-of-freedom (TDOF) consisting of springs-masses-dashpot (SMD) or springsmasses (SM).
Abstract: The problem of transverse low-velocity impact on a linearly in-plane prestressed sandwich panel has been considered in this article. The panel may be subjected to initial in-plane biaxial normal and shear stresses along the edges of the panel. Impact is assumed to occur normally over the top or the bottom face-sheets, at arbitrary location. The boundary conditions of the top and the bottom face-sheets are independent. The interaction between the impactor and the panel is modeled with the help of the system having three-degrees-of-freedom (TDOF) consisting of springs-masses-dashpot (SMD) or springs-masses (SM). The effects of initial biaxial stresses and transverse flexibility of the core are considered analytically. In order to determine all components of the displacements, stresses and strains in the face-sheets and the core, a numerical procedure based on improved higher-order sandwich plate theory (IHSAPT) and Galerkin’s method, are employed. The deflections and the corresponding stresses in the panel ...
TL;DR: In this article, the linear static and buckling analysis of an asymmetric square sandwich plate with orthotropic stiffness properties in the face layers is presented, and two analytical formulations related to the analysis are presented.
Abstract: This article deals with the linear static and buckling analysis of an asymmetric square sandwich plate with orthotropic stiffness properties in the face layers. Two analytical formulations related ...
TL;DR: In this paper, experimental and analytical analysis of the mechanical behavior of crushed foam cores is presented, where three rigid cellular core materials are tested in a uniaxial compression-tension cycle and an analytical model is proposed describing the stressstrain curve in tension and secondary compression.
Abstract: This article deals with experimental and analytical analysis of the mechanical behavior of crushed foam cores. Three rigid cellular core materials are tested in a uniaxial compression-tension cycle. An analytical model is proposed describing the stress-strain curve in tension and secondary compression. A special emphasis is laid on the relaxation behavior of a crushed foam core in tension.
TL;DR: In this article, the shape of the core junction is investigated using finite element analysis and the results are compared with experimental data, which shows that the shape is similar to the one in this paper.
Abstract: In practical sandwich constructions it is often necessary to reinforce the core with high strength inserts to facilitate concentrated loads. The junction between the main core and the core insert is a potential weak spot of the sandwich structure. This section of the sandwich structure is investigated using finite element analysis and the results are compared with experimental data. Furthermore, parameters concerning the shape of the core junction are investigated using finite element analysis.
TL;DR: In this paper, the role of localized effects in the vicinity of junctions between core materials of different stiffness when these joints are non-vertical and may take any shape is investigated.
Abstract: The article investigates the role of localized effects in the vicinity of junctions between core materials of different stiffness when these joints are non-vertical and may take any shape. The mathematical formulation uses a variational approach, and the proposed analysis incorporates the effects of the vertical flexibility of the core following the high-order sandwich panel theory (HSAPT) approach. The proposed analysis is geometrically non-linear. The presented study examines various joint types in the vicinity of the boundaries between cores of different stiffness in the load introduction zone, including: straight vertical (traditional ‘butt’ junction), straight non-vertical with different inclination angles, a double line joint, and finally a double line joint with extremely large difference between the stiffness properties of the joined cores. The response is described in terms of deflections and stress resultants in the face sheets, as well as in terms of the interfacial stresses at the upper and lo...
TL;DR: In this paper, the authors investigated the role of localized effects in the geometrically nonlinear response of modern sandwich panels made of a soft core when subjected to distributed loads.
Abstract: The article presents the results of an investigation on the role of the localized effects in the geometrically nonlinear response of modern sandwich panels made of a ‘soft’ core when subjected to distributed loads. The adopted nonlinear analysis approach incorporates the effects of the vertical flexibility of the core, and it is based on the approach of the high-order sandwich panel theory (HSAPT). The nonlinear governing equations are solved using the multipoint shooting method along with parametric and arc-length continuation procedures. The nonlinear response of the distributed loads is described in terms of deflections and stress resultants in the face sheets, as well as in terms of the interfacial stress components at the upper and lower face-core interfaces. In addition, the equilibrium curves of the load versus the extreme absolute values of the aforementioned structural quantities are presented. The numerical study investigates the localized effects involved in the case of a panel made of a core w...
TL;DR: In this article, the first-order shear theory (Mindlin-Reissner Plate) was applied to analyze the vibration of circular sandwich panels with free, simply supported, and clamped edges.
Abstract: Axisymmetric and non-axisymmetric modes of vibration of circular sandwich panels are investigated by applying first-order shear theory (Mindlin-Reissner Plate). Solutions are obtained for boundary conditions with free, simply supported, and clamped edges. Numerical finite element method (FEM) simulation using ABAQUS is applied to validate the analytical modeling. Both analytical and numerical calculations are compared with experimental measurements of the first few modes of vibration; the frequency differences are less than 4%.