Showing papers in "Journal of Sandwich Structures and Materials in 2011"
TL;DR: In this paper, a theoretical analysis for predicting the initial stiffness E*, and plastic collapse strength σ*pl of BCC micro-lattice blocks under compressive loading is presented, based on the observed deformation mechanisms, and can, in principle, be developed to predict the elastic properties of other micro lattice structures.
Abstract: This article presents a theoretical analysis for predicting the initial stiffness E*, and plastic collapse strength σ*pl of BCC micro-lattice blocks under compressive loading. This theoretical analysis is based on the observed deformation mechanisms, and can, in principle, be developed to predict the elastic properties of other micro-lattice structures. The analytical solutions are verified by comparing the predictions with FEM data using 1D beam and 3D solid elements and uniaxial compression tests on samples fabricated by selective laser melting. The FEM predictions using the 3D solid elements agree well with the experimental data for a wide range of strut aspect ratios, d/L. In addition, the range of applicability of the analytical model and the FEM predictions using beam elements are clarified.
164 citations
TL;DR: In this article, the compressive properties of lattice structures based on a body-centered cubic and a similar structure with vertical pillars were investigated at quasi-static rates of strain.
Abstract: Lattice structures based on two simple architectures have been manufactured from 316L stainless steel using the selective laser melting process. The compressive properties of structures based on a body-centered cubic (BCC) and a similar structure with vertical pillars (BCC-Z) were initially investigated at quasi-static rates of strain. Blast tests were subsequently performed on the lattice structures as well as on lattice sandwich structures with CFRP skins. When subjected to quasi-static compression loading, the BCC structure exhibited a progressive mode of failure, whereas the BCC-Z lattice deformed in a buckling-dominated mode of collapse. The blast response of the lattice cubes exhibited a linear dependency on the applied impulse up to the threshold for material densification. Relationships between the blast resistance and both the yield stress and energy absorption characteristics of the lattices have been established and an examination of the failed samples indicated that the collapse modes were sim...
89 citations
TL;DR: Sandwich materials have been widely used in weight sensitive structures in many fields, especially in the transport industry as mentioned in this paper, and there are different classes of sandwiches with a wide range of material properties.
Abstract: Sandwich materials have been widely used in weight-sensitive structures in many fields, especially in the transport industry. There are different classes of sandwiches with a wide range of material...
43 citations
TL;DR: In this paper, the authors present numerical simulation studies on the vibration and acoustic response characteristics of a multilayered viscoelastic sandwich plate in a thermal environment, where the critical buckling temperature and vibration response were obtained using finite element method while sound radiation characteristics are obtained using boundary element method.
Abstract: This article presents numerical simulation studies on the vibration and acoustic response characteristics of a multilayered viscoelastic sandwich plate in a thermal environment. Initially the critical buckling temperature is obtained followed by free and forced vibration analyses considering the pre-stress due to the imposed thermal environment in the plate. The vibration response predicted is then used to compute the sound radiation. The critical buckling temperature and vibration response are obtained using finite element method while sound radiation characteristics are obtained using boundary element method. It is found that resonant amplitude of both the vibration and acoustic response decreases with increase in temperature. The influence of core thickness, number of layers, type of thermal field, and type of viscoelastic core material on vibration response sound radiation characteristics are studied in detail.
38 citations
TL;DR: In this article, the behavior of sandwich panels with TRC faces is studied and several models are used in a finite element analysis and their advantages and disadvantages are discussed, and the calculated nonlinear behavior of the panels is compared to experimental observations.
Abstract: Textile-reinforced concrete (TRC) is a composite material that recently gained renewed interest. Due to an improved durability, the usage of this composite in lightweight constructions becomes possible. In this article, the behavior of sandwich panels with TRC faces is studied. In the first part, several models are used in a finite element analysis and their advantages and disadvantages are discussed. In the second part, the calculated nonlinear behavior of the panels is compared to experimental observations.
37 citations
TL;DR: In this article, the authors presented a three-dimensional elasticity solution for composite laminates in cylindrical bending, which is based on the three dimensional elasticity model presented in this paper.
Abstract: In an earlier paper, Pagano (1969) [Pagano NJ. Exact solutions for composite laminates in cylindrical bending. J Compos. Mater. 1969; 3: 398–411] presented the three-dimensional elasticity solution...
36 citations
TL;DR: In this paper, two continuum Timoshenko beam models were employed to model the sandwich beam and the resonators were treated as continuously distribable rectilinear units, which is similar to our model.
Abstract: A sandwich beam with embedded internal resonators was studied. Two continuum Timoshenko beam models were employed to model the sandwich beam. One model treats the resonators as continuously distrib...
32 citations
TL;DR: In this article, a sandwich system of two steel faces and a polyurethane core was used as a renovation system for orthotropic steel bridge decks, and an experimental program was carried out aiming to better preserve the structural integrity of the bridge deck.
Abstract: A sandwich system of two steel faces and a polyurethane core is studied as a renovation system for orthotropic steel bridge decks. An experimental program has been carried out aiming to better unde...
32 citations
TL;DR: In this article, vibration and damping analysis of cylindrical sandwich panels containing a viscoelastic flexible core based on the high-order theory of sandwich structures is investigated.
Abstract: In the present study, vibration and damping analysis of cylindrical sandwich panels containing a viscoelastic flexible core based on the high-order theory of sandwich structures is investigated. A ...
31 citations
TL;DR: In this paper, foam core and web core panels are designed for residential roofs and a design procedure is developed that considers R-value, panel deflection, core shear failure, bearing failure, and buckling of the face sheets and webs.
Abstract: Panelized construction of residential buildings is gaining popularity due to the architectural and energy efficiency benefits that can be achieved. An important challenge to the design of panel structures for buildings is the balance between long-term structural performance and the thermal insulating requirement. In this study, foam core and web core panels are designed for residential roofs. Both panels are comprised of two face sheets and an insulating foam core. In the web core panel, thin metal webs that connect the face sheets are added to improve panel shear stiffness and enable longer spans. A design procedure is developed that considers R-value, panel deflection, core shear failure, bearing failure, and buckling of the face sheets and webs. The buckling model includes the ability of the foam core stiffness to restrain the buckling deformation. Panel designs are presented that provide R-5.3 m2 K/W for roof loads of 1500, 2000, and 3000 N/m2, corresponding to climate zones in the US. It is demonstra...
25 citations
TL;DR: In this paper, the structural performance of inserts within honeycomb sandwich panels is investigated and the results show that the cold-bonded inserts outperformed the hot-bundled inserts in terms of load carrying capability.
Abstract: An investigation on the structural performance of inserts within honeycomb sandwich panels is presented. The investigation considers metallic inserts in all aluminum sandwich panels and emphasis is placed on the structural performance difference between hot bonded and cold bonded inserts. The former are introduced during panel manufacture while the latter are potted into existing panels. The investigation focuses on the static performance of the two insert systems subject to loads in the normal direction to the facing plane. The experimental part of the work presented involved carrying out pullout tests on hot bonded and cold bonded reference samples by loading them at a centrally located insert. The experimental results were compared with results from an analytical model and results from a finite element model. Contrary to what was expected it was found from the experiments that the cold bonded inserts outperformed the hot bonded inserts in terms of load carrying capability. From the finite element study...
TL;DR: In this paper, a simplified mechanics of materials equations for predicting both flexural and shear components of transverse deflections in composite sandwich beams are developed and validated by comparison with experimental measurements and finite element numerical predictions.
Abstract: Simplified mechanics of materials equations for predicting both flexural and shear components of transverse deflections in composite sandwich beams are developed and validated by comparison with experimental measurements and finite element numerical predictions. Results are presented and compared for loading point deflections of two types of sandwich beams loaded in four-point bending; one having unidirectional carbon/ epoxy face sheets and a polymethacrylimide (PMI) foam core, and another having woven E-glass/epoxy face sheets and a PMI foam core. In both cases, shear deflections are greater than flexural deflections. The fraction of total deflection due to shear is greater for the beam with unidirectional carbon/epoxy face sheet than for the beam with woven E-glass/epoxy face sheets. Agreement between the current model predictions, experimental results, and finite element results is very good for the beams with unidirectional carbon/epoxy face sheets, and reasonably good for the beams with woven E-glass...
TL;DR: In this article, the mechanical properties of sandwich panels employing E-glass/polyester face sheets bonded to a perforated foam core are evaluated and compared to sandwich panels fabricated with conventional plain sh...
Abstract: Mechanical properties of sandwich panels employing E-glass/polyester face sheets bonded to a perforated foam core are evaluated and compared to sandwich panels fabricated with conventional plain sh...
TL;DR: In this paper, the debonding and buckling failure modes are often the cause of low energy absorption in composite sandwich panels under edgewise compression loading, and to control the failure mode and initial...
Abstract: Facesheet debonding and buckling failure modes are often the cause of low energy absorption in composite sandwich panels under edgewise compression loading. To control the failure mode and initial ...
TL;DR: In this paper, the nonlinear response of a unidirectional sandwich panel that is associated with wrinkling of the face sheets, due to a self-equilibrated loading scheme is presented.
Abstract: The nonlinear response of a unidirectional sandwich panel that is associated with wrinkling of the face sheets, due to a self-equilibrated loading scheme is presented. This loading scheme may be a results of a manufacturing process where the core is tensioned first and the sandwich panel is formed through bonding of the face sheets to the tensioned core while wrinkling occurs as a result of the release of the tensile force of the core, i.e. similar to the manufacturing of electroactive polymers (EAPs) [Wantanaba et al. (2002)] or due to prestressing of the core which is associated with the pre-strain the edge of the core only. These self-equilibrated loads yield compression in the face sheets as well as in the core which may be associated with loss of stability as a result of overall buckling of the entire panel or wrinkling of the face sheets. Thus, for such loading scheme the longitudinal rigidity of the core must be considered although it is small as compared with that of the face sheets. The governing...
TL;DR: In this paper, the linear transient response of composite plates using radial basis functions and collocation method was studied using the Kansa method and Radial Basis Function (RBF).
Abstract: This article presents a study of the linear transient response of composite plates using radial basis functions and collocation method. We use the Kansa method and radial basis functions in a pseud...
TL;DR: In this article, micro-tomography has been used to provide unique information on the quality of honeycomb sandwich structures, information on damage mechanisms and internal details of through thickness reinforcement in pinned foam cores.
Abstract: Although X-radiography has been widely used in studies of damage in composite materials, micro-tomography has received less attention, due to the high cost and limited availability of equipment. However, micro-tomographic analysis is a powerful tool, allowing 3D images of sections through sandwich materials to be obtained without specimen preparation. Four examples from a recent study are presented here, which show how micro-tomography can provide unique information on the quality of honeycomb sandwich structures, information on damage mechanisms and internal details of through thickness reinforcement in pinned foam cores.
TL;DR: In this article, an elementary laminated beam theory and linear elastic fracture mechanics have been used to analyze initial core shear failure and corresponding initial crack sizes in foam core sandwich beams.
Abstract: An elementary laminated beam theory and linear elastic fracture mechanics have been used to analyze initial core shear failure and corresponding initial crack sizes in foam core sandwich beams. The...
TL;DR: In this paper, the authors deal with theoretical modeling of the local buckling in foam-core sandwich panels, mainly in the periodic (unbounded wrinkle wave) and linearly elastic formulation, which can be applied with a good precision for many finite-size panels, as well as for many sandwiches having honeycomb cores.
Abstract: This article deals with theoretical modeling of the local buckling in foam-core sandwich panels. This phenomenon is considered mainly in the periodic (unbounded wrinkle wave) and linearly elastic formulation. The analytical solutions are in agreement with results of finite element analysis and can be applied with a good precision for many finite-size panels, as well as for many sandwiches having honeycomb cores.
TL;DR: In this article, the authors used the model that takes into account compressive and shear stiffnesses, and nonlinear distribution of transverse normal displacements over the core thickness.
Abstract: This article is concerned with the modeling and analysis of symmetrical vibrations of composite sandwich panels. The vibration problem is solved for the sandwich plate with identical composite facings and orthotropic core. The solution is based on the use of the model that takes into account compressive and shear stiffnesses, and nonlinear distribution of transverse normal displacements over the core thickness. The equation is obtained for the calculation of symmetric vibration frequency of the sandwich plate with simply supported facings. The effects of elastic, geometric, and inertia parameters on the frequencies of symmetric vibrations are investigated.
TL;DR: In this paper, a generalized analytical approach to investigate the indentation of sandwich beams under concentrated loads is presented, based on the Winkler foundation theory, and a segment-wise model is implemented.
Abstract: A generalized analytical approach to investigate the indentation of sandwich beams under concentrated loads is presented, based on the Winkler foundation theory. A segment-wise model is implemented...
TL;DR: In this article, a simplified closed-form analytical model is developed to predict critical stresses through a complete range of damage sizes and depths, where the critical load is controlled by the depth and size of damage, both of which control the foundation support and resistance to wrinkles forming.
Abstract: Previous works [1] used nonlinear finite element models to investigate the effects of barely visible impact damage (BVID) in sandwich structures. Through a comprehensive numerical study it was found that sandwich honeycomb panels with BVID fail due to wrinkling or core crushing at significantly lower loads than undamaged panels. The critical load is controlled by the depth and size of damage, both of which control the foundation support and the resistance to wrinkles forming. In this article a simplified, closed-form analytical model is developed to predict critical stresses through a complete range of damage sizes and depths. This model extends previous work [1] by finding an expression for the critical wrinkling wavelength in a closed-form solution. A further expression is developed to account for rotational support at the edge of the damage site, as the wrinkle approaches the critical wrinkling wavelength. This article concludes by comparing numerical and analytical models against experimental values. ...
TL;DR: In this article, the authors elucidate potential advantages of so-called "stepped" facings with geometry modified to locally enhance the strength and stiffness at strategically important locations with a minimum effect on the weight.
Abstract: Sandwich panels have been developed to either produce lighter structures capable of carrying prescribed loads or to increase the load-carrying capacity subject to limitations on the weight. The major load-carrying elements of a sandwich structure are its facings, while the core primarily serves to resist transverse shear loads, enhance local strength and stability of the facings, and combine two facings into a single structural system. The facings being subject to in-plane tensile/compressive loads and to in-plane shear, their strength and stiffness are paramount to the sandwich structure. In this article we elucidate potential advantages of so-called ‘stepped’ facings with geometry modified to locally enhance the strength and stiffness at strategically important locations with a minimum effect on the weight. Numerous examples presented in the article validate our suggestion that a combination of a relatively simple manufacturing process and improved structural response of sandwich panels with stepped facings may present a designer with an attractive alternative to conventional sandwich structures.
TL;DR: In this article, a self-propagating high temperature synthesis (SHS) was used to synthesize metal foam sandwich panels, where a powder mixture of metallic aluminum and copper oxide was placed in core-sheet interface, and then sandwich panel was heated under static pressure.
Abstract: In this study, a novel method for manufacturing metal foam sandwich panels via self-propagating high temperature synthesis (SHS) has been introduced. In this method, a powder mixture of metallic aluminum and copper oxide was placed in core—sheet interface, and then sandwich panel was heated under static pressure. During heating, SHS reaction (3CuO + 2Al = + 3Cu, ΔH < 0) occurred in the interface. The generated heat from this exothermic reaction caused sheets to join the core by melting the interface and nearby. In order to evaluate the shear strength of the interface, the shear test was applied to the manufactured sandwich panels and its results were compared with sandwich panels, which were produced by diffusion and adhesive bonding processes. Furthermore, by the aid of energy dispersive spectrometer and X-ray diffraction analyses, the formation of copper in the core—sheet interface and its diffusion into the sheets and the core were investigated. The results showed that metal foam sandwich panels produc...
TL;DR: In this article, a finite element model consisting of three layers, made of standard CQUAD4 and CHEXA8 elements for facings and core, respectively, was developed, accurately predicting beam bending behavior.
Abstract: Three-point bending tests in the elastic domain were carried out on sandwich specimens with the facings made of unidirectional T800H/3900-2 laminates, and the core of a soft and thin viscoelastic layer, varying the slenderness ratio. A closed-form formula available in the literature, developed for sandwich beams with thick facings, was used to predict the rigidities in flexure, adopting three different methods for the calculation of the shear rigidity. The best results were obtained by the classical sandwich theory, which provided reasonably good correlation with the experimental results, slightly overestimating the actual values. A finite element model consisting of three layers, made of standard CQUAD4 and CHEXA8 elements for facings and core, respectively, was developed, accurately predicting beam bending behavior. From the numerical results, the inability of classical sandwich theory to correctly estimate the bending rigidity is correlated with the through-the-thickness shear deformation of facings, n...
TL;DR: In this article, the authors dealt with fatigue of closed-cell foams under compression loading and tested three densities of Divinycell H-grade and three density of Rohacell WF-grade foam under compression load.
Abstract: This article deals with fatigue of closed-cell foams under compression loading. Testing is performed on three densities of Divinycell H-grade and three densities of Rohacell WF-grade foam under cyc ...
TL;DR: In this paper, three population-based optimization techniques, particle swarm optimization, ant colony optimization, and simulated annealing, are applied to the multi-objective design of sandwich materials.
Abstract: Three population-based optimization techniques — particle swarm optimization, ant colony optimization, and simulated annealing — are applied to the multi-objective design of sandwich materials. The formulation of the algorithms is described, along with metrics for quantifying their performance. For the case study considered of a sandwich beam in bending, it is shown that the ant colony technique out-performs the other two algorithms with respect to identifying optimal geometries, materials, and lay-ups for a stiff sandwich in which low mass and low cost are the design objectives. The particle swarm and simulated annealing algorithms were found to have particular difficulties in handling the optimization of multi-ply oriented fiber-reinforced polymer facing laminates.
TL;DR: In this article, a mild steel sheared dimple core was fabricated by the sectional forming process and then bonded with DP590 face sheets by multi-point resistance welding, where the effect of frictional work on the peak load and energy absorption increases as the bending angle increases.
Abstract: In this study, the bending responses of metallic sandwich plates with a sheared dimple core were investigated through the 3-point bending tests and dynamic plane bending tests. It was experimentally shown from the uniaxial tensile tests that the yield and tensile strengths of the brazed face sheet were weaker than those of the welded face sheet. A mild steel sheared dimple core was fabricated by the sectional forming process and then bonded with DP590 face sheets by multi-point resistance welding. Analysis for large deformation of a sandwich plate subject to 3-point bending was carried out, where frictional work was considered and a face sheet was treated as a rigid-plastic material based on Hollomon’s flow rule. Load—deflection curves and the deformed shapes of the finite element method computations and the experiments were efficiently predicted by the proposed analysis. The effect of frictional work on the peak load and energy absorption increases as the bending angle increases. The dynamic bending resp...
TL;DR: In this article, the bending response of the sandwich panel with functionally graded (FG) skins under thermal and/or mechanical loading is studied, and the results of analytical and FEM solutions are indicative of robustness of analytical solution for prediction of in-plane and out-of-plane stresses.
Abstract: In this article bending response of the sandwich panel with functionally graded (FG) skins under thermal and/or mechanical loading is studied. Higher order sandwich plate theory has been exploited. In addition, by using Fourier conduction equation and obtaining temperature distribution, thermo-elastic behavior of such structure is investigated. Comparison between the results of analytical and FEM solutions is indicative of robustness of the analytical solution for prediction of in-plane and out-of-plane stresses. It is shown a wise selection for FG skin materials is helpful to have better conditions under thermo-mechanical loading and to decrease the delamination failure possibility.
TL;DR: A comparison of the numerical results for aluminum and Kevlar sandwich circular panels and their corresponding monolithic solid circular plates having similar mass shows that under the shock tube blast loadings considered in this study, the peak values of the transmitted overpressure, particle acceleration, and deflection of the back face measured from gauges as mentioned in this paper.
Abstract: Sandwich panels with a cellular core are being widely considered for blast mitigation applications, including armor systems, because of their capability to carry transverse loads with minimal weight penalty and absorb plastic energy. In this study, several finite element models are generated and used in simulating the performance of sandwich circular panels against shock tube blast loadings. A comparison of the numerical results for aluminum and Kevlar sandwich circular panels and their corresponding monolithic solid circular plates having similar mass shows that under the shock tube blast loadings considered in this study, the peak values of the transmitted overpressure, particle acceleration, and deflection of the back face measured from gauges are less for the sandwich circular panels than for the monolithic solid circular plates. The findings are consistent with those reported by other researchers. A parametric study is conducted in investigating the influence of sandwich panel material property, conf...