Showing papers on "Sandwich panel published in 2010"
TL;DR: In this paper, the authors presented a new in situ Structural Health Monitoring (SHM) system able to identify the location of acoustic emission (AE) sources due to low-velocity impacts and to determine the group velocity in complex composite structures with unknown lay-up and thickness.
Abstract: This paper presents a new in situ Structural Health Monitoring (SHM) system able to identify the location of acoustic emission (AE) sources due to low-velocity impacts and to determine the group velocity in complex composite structures with unknown lay-up and thickness. The proposed algorithm is based on the differences of stress waves measured by six piezoelectric sensors surface bonded. The magnitude of the Continuous Wavelet Transform (CWT) squared modulus was employed for the identification of the time of arrivals (TOA) of the flexural Lamb mode ( A 0 ). Then, the coordinates of the impact location and the flexural wave velocity were obtained by solving a set of non-linear equations through a combination of global Line Search and backtracking techniques associated to a local Newton’s iterative method. To validate this algorithm, experimental tests were conducted on two different composite structures, a quasi-isotropic CFRP and a sandwich panel. The results showed that the impact source location and the group speed were predicted with reasonable accuracy (maximum error in estimation of the impact location was approximately 2% for quasi-isotropic CFRP panel and nearly 1% for sandwich plate), requiring little computational time (less than 2 s).
175 citations
TL;DR: In this article, the perforation of composite sandwich structures subjected to high-velocity impact was analyzed, and the contribution of failure mechanisms to the energy-absorption of the projectile kinetic energy was determined.
157 citations
TL;DR: In this paper, the authors describe a numerical and experimental investigation on the flexural wave propagation properties of a novel class of negative Poisson's ratio honeycombs with tetrachiral topology.
Abstract: This paper describes a numerical and experimental investigation on the flexural wave propagation properties of a novel class of negative Poisson's ratio honeycombs with tetrachiral topology. Tetrachiral honeycombs are structures defined by cylinders connected by four tangent ligaments, leading to a negative Poisson's ratio (auxetic) behavior in the plane due to combined cylinder rotation and bending of the ribs. A Bloch wave approach is applied to the representative unit cell of the honeycomb to calculate the dispersion characteristics and phase constant surfaces varying the geometric parameters of the unit cell. The modal density of the tetrachiral lattice and of a sandwich panel having the tetrachiral as core is extracted from the integration of the phase constant surfaces, and compared with the experimental ones obtained from measurements using scanning laser vibrometers.
140 citations
TL;DR: In this article, a curved sandwich panel with two aluminium face sheets and an aluminium foam core under air blast loadings was investigated experimentally, and the experimental data showed that the initial curvature of a curved panel may change the deformation/collapse mode with an extended range for bending dominated deformation, which suggests that the performance of the sandwich shell structures may exceed that of both their equivalent solid counterpart and a flat sandwich plate.
118 citations
TL;DR: In this article, the feasibility of fabrication and flexural performance of panels composed of low-density polyurethane foam core sandwiched between two GFRP skins was explored and compared to a panel without ribs.
116 citations
TL;DR: In this article, the feasibility of using micro-encapsulated PCM (Micronal BASF) in sandwich panels to increase their thermal inertia and to reduce the energy demand of the final buildings was demonstrated.
99 citations
TL;DR: In this paper, the compressive response of rigidly supported stainless steel sandwich panels subject to a planar impulsive load in water is investigated, and the essential aspects of the dynamic response, such as the transmitted momentum and the degree of core compression, are captured with surprising fidelity by modeling the cores as equivalent metal foams having plateau strengths represented by the quasi-static peak strength.
Abstract: The compressive response of rigidly supported stainless steel sandwich panels subject to a planar impulsive load in water is investigated. Five core topologies that spanned a wide range of crush strengths and strain-dependencies were investigated. They included a (i) square-honeycomb, (ii) triangular honeycomb, (iii) multi-layer pyramidal truss, (iv) triangular corrugation and (v) diamond corrugation, all with a core relative density of approximately 5%. Quasi-statically, the honeycombs had the highest peak strength, but exhibited strong softening beyond the peak strength. The truss and corrugated cores had significantly lower strength, but a post yield plateau that extended to beyond a plastic strain of 60% similar to metal foams. Dynamically, the transmitted pressures scale with the quasi-static strength. The final transmitted momentum increased slowly with core strength (provided the cores were not fully crushed). It is shown that the essential aspects of the dynamic response, such as the transmitted momentum and the degree of core compression, are captured with surprising fidelity by modeling the cores as equivalent metal foams having plateau strengths represented by the quasi-static peak strength. The implication is that, despite considerable differences in core topology and dynamic deformation modes, a simple foam-like model replicates the dynamic response of rigidly supported sandwich panels subject to planar impulsive loads. It remains to ascertain whether such foam-like models capture more nuanced aspects of sandwich panel behavior when locally loaded in edge clamped configurations.
95 citations
TL;DR: In this article, air-blast tests are conducted on sandwich panels composed steel face sheets with unbonded aluminium foam (Alporas, Cymat) or hexagonal honeycomb cores.
84 citations
TL;DR: In this article, the free vibration analysis of composite sandwich cylindrical shell with a flexible core using a higher order sandwich panel theory is presented. But the analysis is restricted to the case of composite shells.
83 citations
TL;DR: In this article, an ant colony optimisation (ACO) algorithm was used to search a design space that was defined by sandwich theory and a material database in order to identify constructions that were optimal with respect to low mass and low cost.
82 citations
TL;DR: In this paper, the flexural behavior of a new sandwich panel proposed for cladding of buildings is studied, which is fabricated by laminating two glass fiber-reinforced polymer skins to a prefabricated polyurethane foam core.
Abstract: The flexural behavior of a new sandwich panel proposed for cladding of buildings is studied. The panel is fabricated by laminating two glass fiber-reinforced polymer skins to a prefabricated polyurethane foam core. Two different densities for the core are explored, namely; a 0.31 kN/m3, referred to herein as ‘soft’ foam, and a 0.63 kN/m3, referred to as ‘hard’ foam. Ten 1500 × 300 × 76 mm3 panels were tested in flexure. For each core density, three similar panels were tested to establish the reproducibility of test results as a measure of quality control of fabrication. The panels were tested in three-point and four-point bending as well as under uniform load. The effect of wind pressure and suction was simulated for some panels by applying cyclic bending. It was shown that flexural strength and stiffness increased substantially, by 165% and 113%, respectively, as the core density was doubled. The contributions of shear deformation of the soft and hard cores to mid-span deflection were 75% and 50%, respec...
TL;DR: In this paper, a theoretical solution is obtained to predict the dynamic response of peripherally clamped square metallic sandwich panels with either honeycomb core or aluminium foam core under blast loading, where the deformation of sandwich structures is separated into three phases, corresponding to the transfer of impulse to the front face velocity, core crushing and overall structural bending/stretching, respectively.
TL;DR: In this paper, a solution methodology to predict the residual velocity of a hemispherical-nose cylindrical projectile impacting a composite sandwich panel at high velocity is presented, where the term high velocity impact is used to describe impact scenarios where the projectile perforates the panel and exits with a residual velocity.
TL;DR: In this article, the authors measured the underwater blast response of free-standing sandwich plates with a square honeycomb core and a corrugated core, and the total momentum imparted to the sandwich plate and the degree of core compaction were measured as a function of core strength, mass of the front face sheet (that is, the wet face) and time constant of the blast pulse.
TL;DR: In this article, a finite element model was used to compare the deformation and stress of a composite battery with a real battery, and the model's performance was compared with real battery cells.
TL;DR: In this article, the effect of replacing honeycomb sandwich panel structures with metallic open-cell foam structures on MMOD shielding performance is assessed for an MLM-representative configuration, and a number of hypervelocity impact tests have been performed on both the baseline honeycomb configuration and upgraded foam configuration.
TL;DR: In this article, the free vibration of doubly curved sandwich shell with flexible core based on a refined general-purpose sandwich panel theory was analyzed and the obtained results were validated by the analytical and numerical results published in the literatures.
TL;DR: In this paper, a statistical energy analysis (SEA) approach is used to predict the sound transmission loss (STL) of sandwich panels numerically, which accounts for both antisymmetric and symmetric (dilatational) motions.
Abstract: A statistical energy analysis (SEA) approach is used to predict the sound transmission loss (STL) of sandwich panels numerically. Unlike conventional SEA studies of the STL of sandwich panels, which consider only the antisymmetric (bending) motion of the sandwich panel, the present approach accounts for both antisymmetric and symmetric (dilatational) motions. Using the consistent higher-order sandwich plate theory, the wave numbers of the waves propagating in the sandwich panel were calculated. Using these wave numbers, the wave speed of the propagating waves, the modal density, and the radiation efficiency of the sandwich panels were determined. Finally, the sound transmission losses of two sandwich panels were calculated and compared with the experimentally measured values, as well as with conventional SEA predictions. The comparisons with the experimental data showed good agreement, and the superiority of the present approach relative to other approaches is discussed and analyzed.
TL;DR: In this article, a micromechanical method was developed to homogenize a corrugated-core sandwich panel as an equivalent orthotropic plate and calculate the equivalent thermal forces and moments for a given temperature distribution.
Abstract: This paper is concerned with homogenization of a corrugated-core sandwich panel, which is a candidate structure for integral thermal protection systems for space vehicles. The focus was on determination of thermal stresses in the face sheets and the web caused by through-the-thickness temperature variation. A micromechanical method was developed to homogenize the sandwich panel as an equivalent orthotropic plate and calculate the equivalent thermal forces and moments for a given temperature distribution. The same method was again used to calculate the stresses in the face sheets and the core. The method was demonstrated by calculating stresses in a sandwich panel subjected to a temperature distribution described by a quartic polynomial in the thickness direction. Both constrained and unconstrained boundary conditions were considered. In the constrained case the plate boundaries are constrained such that there are no deformations in the macroscale sense. The unconstrained case assumes that there are no force and moment resultants in the macroscale. The results for stresses are compared with that from a three-dimensional finite element analysis of the representative volume element of the sandwich structure, and the comparison was found to be within 5 % difference. The micromechanical analysis, which is less time consuming, will be useful in the design and optimization of integral thermal protection system structures.
TL;DR: In this paper, a rational analytical model is presented and used to evaluate the effective elastic modulus, shear modulus and degree of composite interaction of the panels to resist one-way bending.
Abstract: This paper presents the findings of a research program that was undertaken to evaluate the static and fatigue characteristics of an innovative 3-D glass fiber reinforced polymer (GFRP) sandwich panel proposed for civil infrastructure and transportation applications. The research consists of analytical modeling verified by experimental results. A rational analytical model is presented and used to evaluate the effective elastic modulus, shear modulus and degree of composite interaction of the panels to resist one-way bending. The experimental program was conducted in two phases to study the static and fatigue behavior of the panels. In the first phase a total of 730 sandwich beams were tested to evaluate the effect of different parameters on the fundamental behavior of the panel. The parameters considered include the pattern and density of through-thickness fiber insertions, the overall thickness of the panels, and the number of FRP plies in the face skins. The study indicates that the shear behavior and degree of composite interaction of the panels is sensitive to the configuration of the panel core. The second phase of the experimental program included testing of 24 additional sandwich panels to evaluate the fatigue behavior. The results of the experimental program indicate that the panels with stiffer cores generally exhibited a higher degree of degradation than panels with more flexible cores. The findings of this study indicate that the proposed panels represent a versatile construction system which can be configured to achieve the specific design demands for civil engineering infrastructure applications.
TL;DR: In this paper, the authors developed a system of empirical equations that can be used to predict the trajectories and spread of the debris clouds that exit the rear facesheet following a high speed perforating impact of a honeycomb sandwich panel (HC/SP).
TL;DR: In this paper, a theoretical study on the sound transmission loss (STL) characteristics of unbounded orthotropic sandwich panels considering the transverse shear deformation is presented, where the authors derived the governing equation of bending vibration for unbounded ORS panels and implemented it to sound transmission problem.
TL;DR: A semi-analytical method for bending, global buckling, and free vibration analyses of sandwich panels with square-honeycomb cores is presented in this paper, where the core sheets are treated as thin beams and the sandwich panel as composite structure of plates and beams with proper displacement compatibility.
Abstract: A semi-analytical method for bending, global buckling, and free vibration analyses of sandwich panels with square-honeycomb cores is presented. The discrete geometric nature of the square-honeycomb core is taken into account by treating the core sheets as thin beams and the sandwich panel as composite structure of plates and beams with proper displacement compatibility. Based on the classical model of sandwich panels, the governing equations of motion of the discrete structure are derived using Hamilton's principle. Closed-form solutions are developed for bending, global buckling, and free vibration of simply supported square-honeycomb sandwich panels by employing Fourier series and the Galerkin approach. Results from the proposed method agree well with available results in the literature and those from detailed finite element analysis. The effects of various geometric parameters of the sandwich panel on its behavior are investigated. The present method provides an efficient way of analysis and optimization of sandwich panels with square-honeycomb cores.
Patent•
09 Feb 2010TL;DR: In this article, an integrated aerodynamic energy storage and rear suspension assembly includes a rear fuel tank/suspension module, a battery support assembly and a structural joining plate, with a propulsion battery mounted on a front sandwich plate.
Abstract: An integrated aerodynamic energy storage and rear suspension assembly includes a rear fuel tank/suspension module, a battery support assembly and a structural joining plate. The rear fuel tank/suspension module includes a rear sandwich panel, a fuel tank assembly mounted on the rear sandwich panel, with the rear fuel tank/suspension module sliding into a rear body cavity. The battery support assembly includes a propulsion battery mounted on a front sandwich plate, with the front sandwich plate having an upper face sheet adjacent to the propulsion battery, a lower face sheet spaced from the upper face sheet and a core connecting the upper face sheet to the lower face sheet, and with the lower face sheet having a smooth lower surface.
TL;DR: In this article, a monocoque satellite structure composed of many composite sandwich panels, which consist of two carbon fiber/epoxy composite faces and an aluminum honeycomb core, was designed to reduce structural mass and to improve static and dynamic structural rigidity.
TL;DR: In this paper, an exact solution for the buckling problem of a sandwich panel (wide beam) in uniaxial compression is presented, which correspond to the use of different pairs of energetically conjugate stress and strain measures for the infinitesimal elastic stability of the sandwich panel.
Abstract: This paper is concerned with the elastic stability of a sandwich beam panel using classical elasticity. An exact solution for the buckling problem of a sandwich panel (wide beam) in uniaxial compression is presented. Various formulations that correspond to the use of different pairs of energetically conjugate stress and strain measures for the infinitesimal elastic stability of the sandwich panel are discussed. Results from the present two-dimensional analyses to predict the global and local buckling of a sandwich panel are compared with previous theoretical and experimental results. A new finite element formulation for the bifurcation buckling problem is also introduced. In this new formulation, terms that influence the buckling load, which have been omitted in popular commercial codes are pointed out and their significance in influencing the buckling load is identified. The formulation and results presented here can be used as a benchmark solution to establish the accuracy of numerical methods for computing the buckling behavior of thick, orthotropic solids.
TL;DR: In this article, an experimental evaluation of the energy absorption of constrained triggered sandwich structures is presented, where four configurations of embedded ply-drop triggering mechanisms were analysed and compared, and a composite pi-joint was developed to provide a constraint fixture that is representative of an in-service integrated energy absorbing structure.
Abstract: An experimental evaluation of the energy absorption of constrained triggered sandwich structures is presented. Four configurations of embedded ply-drop triggering mechanisms were analysed and compared. A composite pi-joint was then developed to provide a constraint fixture that is representative of an in-service integrated energy absorbing structure. The specimens tested within the pi-joints obtained slightly lower specific energy absorption compared to the equivalent specimens tested in a rigid test fixture. The potential of an integrated energy absorbing triggered sandwich structure contained within a composite pi-joint was demonstrated. The interface between the sandwich panel and the pi-joint was not bonded, and further research will focus on the development of a bonded joint configuration suitable for structural applications.
TL;DR: In this paper, the design and weight optimization of a multi-functional vehicle body panel in an automotive context is discussed, where an existing vehicle design has provided functional design requirements and the body panel is optimized.
Abstract: This article deals with the design and weight optimization of a multi-functional vehicle body panel in an automotive context. An existing vehicle design has provided functional design requirements ...
TL;DR: In this article, an innovative fiber composite sandwich panel made of glass fibre reinforced polymer skins and a modified phenolic core material was developed for building and other structural applications, and the behavior of this new generation sandwich panel was studied with reference to the main fibre orientation in floor applications, so that the effect due to erroneous installation could be evaluated.
Journal Article•
TL;DR: In this paper, a precast lightweight Foamed Concrete Sandwich Panel (PLFP) is proposed as a new affordable building system, which consists of two foamed concrete wythes and a polystyrene insulation layer in between them.
Abstract: Affordable quality housing is vital in developing countries to meet its growing population. Development of a new cost effective system is crucial to fulfill these demands. In view of this, a study is carried out to develope a Precast Lightweight Foamed Concrete Sandwich Panel (PLFP), as a new affordable building system. Experimental investigation and finite element analysis to study the structural behaviour of the PLFP panel under axial load is undertaken. The panel consists of two foamed concrete wythes and a polystyrene insulation layer in between the wythes. The wythes are reinforced with high tensile steel bars and tied up to each other through the polystyrene layer by steel shear connectors bent at an angle of 45o. The panels are loaded with axial load until failure. The ultimate load carrying capacity, load-lateral deflection profile, strain distributions, and the failure mode are recorded. Partial composite behaviour is observed in all specimens when the cracking load is achieved. Finite element analysis is also carried out to study the effect of slenderness ratio and shear connectors which are the major parameters that affect the strength and behaviour of the panels. An empirical equation to predict the maximum load carrying capacity of the panels is proposed. The PLFP system proposed in this research is able to achieve the intended strength for use in low rise building. Considering its lightweight and precast construction method, it is feasible to be developed further as a competitive IBS building system.