Design Of Sandwich Panels Research Articles

Optimal design of a honeycomb core composite sandwich panel using evolutionary optimization algorithms

The present paper deals with the optimal design of a composite sandwich panel with honeycomb core structure using particle swarm optimization (PSO) technique. The face sheets of sandwich panel are considered to be thin and the sandwich panel is subjected to a uniformly distributed normal load. The Navier type solution and the closed-form expressions for the macroscopic in-plane elastic constants of the honeycombs are used to predict the deflection of the panel. Also, the maximum stress in the composite sandwich panel is determined using the macroscopic stress–strain relation of the honeycomb core and the plate. Niching Memetic PSO (NMPSO) and Locally Informed Particle Swarm (LIPS) variants of PSO are examined to minimize the weight of the panel. Numerical results showed that the optimal geometry of the honeycomb cell has this property that its radius and thickness converge to their lower bounds while its length converges to its upper bound. This means that to have an optimal panel, each cell should have the allowable minimum cross section (highest number of cells) and maximum allowable length. Moreover the effects of panel aspect ratio, cell width and applied load were examined. Also, the numerical results confirm the efficiency and effectiveness of the NMPSO in finding optimal solution on the constrained and unconstrained objective functions.

Localized damage response of carbon fiber reinforced polymer composite sandwich panel after thermal exposure

An experimental study was conducted to investigate the effect of thermal exposure on indentation behavior of carbon fiber reinforced polymer composite sandwich panel (CFRPCSP) with pyramidal truss cores. Composite sandwich panels were fabricated by the hot press molding method. Subsequently, composite sandwich panels were exposed to different temperatures for 6 h. After thermal exposure, quasi-static indentation tests were carried out at room temperature. Then, the effect of thermal exposure on the failure mechanism, indentation load and energy absorption were analyzed and discussed. The results showed that the indentation load and energy absorption decreased as exposure temperature increased, which was caused by the degradation of the matrix properties and fiber-matrix interface properties at high temperature. In addition to the decrease of the indentation load and energy absorption, the failure modes also changed with exposure temperature. It is expected that this study can provide useful information for the design and application of composite sandwich panel with pyramidal truss cores at high temperature.

Design of Cellular Composite Sandwich Panels for Maximum Blast Resistance Via Energy Absorption

This paper presents a design methodology for optimizing the energy absorption under blast loads of cellular composite sandwich panels. A combination of dynamic finite element analysis (FEA) and simplified analytical modeling techniques are used. The analytical modeling calculates both the loading effects and structural response resulting from user-input charge sizes and standoff distances and offers the advantage of expediting iterative design processes. The FEA and the analytical model results are compared and contrasted then used to compare the energy response of various cellular composite sandwich panels under blast loads, where various core shapes and dimensions are the focus. As a result, it is concluded that the optimum shape consists of vertically-oriented webs while the optimum dimensions can be generally described as those which cause the most inelasticity without failure of the webs. These dimensions are also specifically quantified for select situations. This guidance is employed, along with the analytical method developed by the authors and considerations of the influences of material properties, to suggest a general design procedure that is a simple yet sufficiently accurate method for design. The suggested design approach is also demonstrated through a design example.

Design and Evaluation of Thin-Walled Hollow-Core Wood-Strand Sandwich Panels

Design and Evaluation of Thin-Walled Hollow-Core Wood-Strand Sandwich Panels

The Main Factors that Influence the Mechanical Properties of Honeycomb Board

It’s very important to select appropriate dimensions for manufacture of honeycomb sandwich. In this paper, the experimental and theoretical methods were compared. The results are proved that the theoretical formula can be applied to engineering design. The impact factor of staties mechanical properties of honeycomb panels also was studied. And a theoretical basis for the design of honeycomb sandwich panels is provided.

Cost optimization of load carrying thin-walled precast high performance concrete sandwich panels

The paper describes a procedure to find the structurally and thermally efficient design of load-carrying thin-walled precast High Performance Concrete Sandwich Panels (HPCSP) with an optimal economical solution. A systematic optimization approach is based on the selection of material's performances and HPCSP's geometrical parameters as well as on material cost function in the HPCSP design. Cost functions are presented for High Performance Concrete (HPC), insulation layer, reinforcement and include labour-related costs. The present study reports the economic data corresponding to specific manufacturing process and actual financial parameters for the Danish prefabrication industry. The strength based design of HPCSP is in competence with the format of Eurocode 2 and takes into account failure modes related to flexure, shear, HPCSP buckling/slenderness, local HPC plate buckling and maximum deflections. The solution of the optimization problem is performed in the computer package software Matlab® with SQPlab package and integrates the processes of HPCSP design, quantity take-off and cost estimation. The proposed optimization process outcomes in complex HPCSP design proposals to achieve minimum cost of HPCSP.

Design of auxetic sandwich panel faceplates comprising cellular networks with high stiffness and negative Poisson’s ratio

In the present work, a novel design is presented for producing auxetic laminated faceplates for structures that contain auxetic cores in order to produce fully auxetic sandwich structures. The design is based on the use of periodic cellular networks that are embedded in a fibre-reinforced polymer matrix. These networks have a high in-plane negative Poisson’s ratio and a high in-plane stiffness. Two auxetic networks were chosen for this purpose: a classical re-entrant hexagonal network and an anti-tetra chiral auxetic network. The finite elements method was used to model the auxetic network and the faceplate. For the auxetic network, the relative modulus (Es/Em) was investigated to determine its effect on the behaviour of the faceplate. The auxetic behaviour of the faceplate occurs when the auxetic network has a high relative modulus. For example, for a classical re-entrant hexagonal network faceplate, the auxetic behaviour starts to appear when Es/Em > 33, while for an anti-tetra chiral auxetic network faceplate, the auxetic behaviour starts to appear when Es/Em > 24. Analytical expressions for the elastic constants of the faceplates were developed using the representative volume element model (RVE) and a semi-empirical formula of the rule of mixtures (ROMs). The results of the analytical expressions were compared with the finite elements results for various values of the relative density parameter ρ*. The relative density had a significant effect on the elastic constants of the faceplate. The model produced with the representative volume element method had higher values for the elastic constants than did that created with the finite elements model, but the semi-empirical rule of mixtures gave more accurate results for both types of faceplates. A modified design for the classical re-entrant hexagonal network that increases the in-plane stiffness of the auxetic network is presented since it has been found that it plays a major role in producing a high negative Poisson’s ratio. The modified networks are an oval re-entered and a stiffened re-entered network. Experiments were carried out on the oval re-entered faceplates to obtain the in-plane moduli and the Poisson’s ratios. The tested faceplate samples clearly showed auxetic behaviour. A good agreement between the finite elements results and the experimental data was obtained.

The low velocity impact response of sandwich panels with lattice core reinforcement

This study presents the experimental and simulation results for the low velocity impact response of sandwich panels reinforced with a lattice core structure. Two different core material and architecture combinations are investigated; a UV-cured photopolymer lattice, produced from a network of self-propagating waveguides, and an aluminum alloy lattice cast from an initial polymer template. For each of these sandwich panel configurations, impact tests were performed with a drop-weight hemispherical impactor under four different energy levels. The applied impact force, impactor velocity and residual damage in the sandwich panel were all measured and used for comparison against finite element simulations of the impact tests. These simulations employed a homogenized continuum constitutive model, designed to replicate the deformation response of the lattice core without requiring explicit representation of the geometric features of the lattice. For both sandwich panel designs at all impact energy levels, excellent correlation was observed between the experimental measurements and impact simulations. Additionally, each sandwich design was shown to be effective at absorbing the kinetic energy of the impactor with minimal damage to the back (non-impacted) face of the panel. Implementation of these lattice core sandwich panels and extension of the homogenized constitutive model to other sandwich applications are also discussed.

Aeroelastic tailoring of composite sandwich panel with lamination parameters

For sandwich panel with a thick core, stiffness matrix of composite sandwich panel can be formulated as function of membrane lamination parameters of the composite facesheet. In this paper, the flutter speed of a cantilevered sandwich panel is studied using lamination parameters of composite facesheet, with influence of transverse shear on sandwich panel considered. The results show that the flutter mode switch is not only related to the bending stiffness change, and also the transverse shear effect can result in switch of flutter mode. A minimum weight design of composite sandwich panel is conducted by using master-slave parallel real-coded genetic algorithm, with lamination parameters of facesheet and transverse shear modulus of foam core as design variables. The constraints considered include the flutter and divergence velocity constraints, the bound constraints of thicknesses of the facesheet and foam core. The feasible region constraints of membrane lamination parameters are also considered.

Integrated design of aluminum foam processing parameters and sandwich panels under uncertainty

Aluminum foam is a useful material for lightweight structural and impact attenuation applications due to its excellent energy-absorbing characteristics. The aim of this study is to further enhance the performance of closed-cell aluminum foam-cored sandwich panels while satisfying given design requirements. A new design approach is employed, whereby the materials and product design are integrated, and which incorporates multilevel design optimization under various types of uncertainty in the analysis and manufacturing processes. Sandwich panels are designed by controlling the processing parameters for the foam core and panel geometry according to the design methods being used. The design variables are optimized through traditional multilevel optimization and analytical target cascading method. Inductive design exploration method is introduced to identify the feasible regions for the design variable in a design hierarchy to be insensitive to uncertainty. This work presents an in-depth examination of the design results and the efficiency of the design methods for pursuing robust design solutions.

Composite and non-composite behaviors of foam-insulated concrete sandwich panels

The structural behaviors of foam-insulated concrete sandwich panels subjected to uniform pressure have been evaluated. This study showed that the interface conditions such as composite and non-composite had a significant effect on the response of foam-insulated concrete sandwich panels, indicating that the simulated shear tie resistance should indeed be incorporated in numerical analyses. Finite element models were developed to simulate the detailed shear resistance of connectors and the nonlinear behaviors of concrete, foam and rebar components. The models were then validated using data from static tests performed at the University of Missouri. The modeling approach used here was compatible with the American Concrete Institute (ACI) Code and existing design practices. The results of this study will therefore provide improved methodology for the analysis and design of foam-insulated sandwich panels under both static and blast loadings.

Response of aluminium foam-cored sandwich panels to bending load

The response of aluminium sandwich panels comprising thin foam cores and thin face sheets of low and high yield strength was investigated under three-point bending load. The effect of skin strength, bending span and core thickness on the failure modes and loads was investigated. While the lower strength face sheet is associated with lower failure loads, that decrease is not proportional to the yield strength due to the additional failure mode of face yielding. Theoretical models enabled prediction of the failure loads and elucidated the contribution of each failure mode. Failure maps were subsequently constructed which can be used for the design of foam-cored sandwich panels with very thin face sheets.

Optimal Design of Sandwich Panels Using Multi-Objective Genetic Algorithm and Finite Element Method

Low weight and high load capacity are remarkable advantages of sandwich panels with corrugated core, which make them more considerable by engineering structure designers. It is important to consider the limitations such as yielding and buckling as design constraints for optimal design of these panels. In this paper, multi-objective optimization of sandwich panels with corrugated core is carried out by minimizing two supposed objective functions, the structure’s weight and deflection. The finite element model of structure is created using the commercial software ANSYS, which is employed to calculate the deflection of panel in different problem conditions. A NSGA-II code prepared in MATLAB, is used to perform the optimization process in a gradual evolution trend, which leads to obtain the Pareto front consisting a set of design vectors and optimal objective function vectors. Two conventional methods are then used to select the trade-off optimal point among the Pareto nondominant optimal set.

New European Recommendations for the design and application of sandwich panels – Results of the work of the Joint Committee on Sandwich Constructions

AbstractThe design and manufacture of factory‐made self‐supporting sandwich panels are covered by European standard EN 14509. Two new European Recommendations extend the potential applications for the standard, providing information about the influence of openings on the loadbearing behaviour of the panels and about the possibility of supporting beams, purlins and cladding rails against stability failures. The new European Recommendations were prepared by the European Joint Committee on Sandwich Constructions.

Testing and Acceptance Criteria for Fiber-Reinforced Composite Grid Connectors Used in Concrete Sandwich Panels

Precast concrete sandwich panels have been used in building construction since the 1960s. These sandwich wall panels are constructed with two wythes of concrete separated by a layer of thermal foam plastic insulation and a shear connector mechanism between concrete wythes. Recently, more research is focused on fiber-reinforced composite grids as shear connectors due to their superior thermal performance compared to other connectors such as steel or solid concrete. However, while there are guidelines for design of concrete sandwich panels, there is no standardized guidance that provides testing and capacity determination for composite shear connectors. Therefore, testing and acceptance criteria were developed to evaluate the shear transfer capacities of fiber-reinforced composite grid connectors used in combination with rigid insulation in concrete sandwich panel construction. The criteria are intended to standardize testing and evaluation of the interaction between concrete and composite shear connectors so manufacturers can provide consistent results, and the data pool generated by standardized testing can support the formulation of design assumptions.

NUMERICAL STUDY OF BLAST-RESISTANT SANDWICH PANELS WITH ROTATIONAL FRICTION DAMPERS

Blast-resistant structures are traditionally designed with solid materials of huge weight to resist blast loads. This not only increases the construction costs, but also undermines the operational performance. To overcome these problems, many researchers develop new designs with either new materials or new structural forms, or both to resist the blast loads. Friction damper, as a passive energy absorber, has been used in earthquake-resistant design to absorb vibration energy from cyclic loading. The use of friction damper in blast-resistant design to absorb high-rate impact and blast energy, however, has not been well explored. This study introduces a new sandwich panel equipped with rotational friction hinge device with spring (RFHDS) between the outer and inner plates to resist the blast loading. This device RFHDS, as a special sandwich core and energy absorber, consists of rotational friction hinge device (RFHD) and spring. The RFHD is used to absorb blast energy while the spring is used to restore the original shape of the panel. This paper studies the mechanism of RFHD by using theoretical derivation and numerical simulations to derive its equivalent force–displacement relation and study its energy absorption capacity. In addition, the energy absorption and blast loading resistance capacities of the sandwich panel equipped with RFHDS are numerically investigated by using Ls-Dyna. It is found that the proposed sandwich panel can recover, at least partially its original configuration after the loading and thus maintain its operational and blast-resistance capability after a blasting event. In order to maximize the performance of the proposed sandwich panel, parametric calculations are carried out to study the performance of RFHDS and the sandwich panels with RFHDS. The best performing sandwich panel with RFHDS in resisting blast loadings is identified. This sandwich panel configuration might be employed to mitigate blast loading effects in structural sandwich panel design.

Research on Crushing Performance of Sandwich Panel with V-Type Corrugated Core under Shock Load

Sandwich panels with a V-type corrugated core are developed to investigate their crushing performance under lateral load based on the numerical method. The validity and feasibility of the calculation method is qualified by comparing numerical results with experiment results. Based on that, finite element software is applied to analyze the effects of structural parameters on the crushing performance of sandwich structure. Then inspecific energy increases as the core thickness and inclination angle are increased, but it will induce as the core height is raised. Additionally, the average crushing strength is increased with the increasing thickness, but it will decrease as the core height and inclination angle are raised. The results of this research may help the practical design and optimization of sandwich panel with corrugated core.

The impact of sand slugs against beams and plates: Coupled discrete particle/finite element simulations

The impact of a slug of dry sand particles against a metallic sandwich beam or circular sandwich plate is analysed in order to aid the design of sandwich panels for shock mitigation. The sand particles interact via a combined linear-spring-and-dashpot law whereas the face sheets and compressible core of the sandwich beam and plate are treated as rate-sensitive, elastic–plastic solids. The majority of the calculations are performed in two dimensions and entail the transverse impact of end-clamped monolithic and sandwich beams, with plane strain conditions imposed. The sand slug is of rectangular shape and comprises a random loose packing of identical, circular cylindrical particles. These calculations reveal that loading due to the sand is primarily inertial in nature with negligible fluid–structure interaction: the momentum transmitted to the beam is approximately equal to that of the incoming sand slug. For a slug of given incoming momentum, the dynamic deflection of the beam increases with decreasing duration of sand-loading until the impulsive limit is attained. Sandwich beams with thick, strong cores significantly outperform monolithic beams of equal areal mass. This performance enhancement is traced to the “sandwich effect” whereby the sandwich beams have a higher bending strength than that of the monolithic beams. Three-dimensional (3D) calculations are also performed such that the sand slug has the shape of a circular cylindrical column of finite height, and contains spherical sand particles. The 3D slug impacts a circular monolithic plate or sandwich plate and we show that sandwich plates with thick strong cores again outperform monolithic plates of equal areal mass. Finally, we demonstrate that impact by sand particles is equivalent to impact by a crushable foam projectile. The calculations on the equivalent projectile are significantly less intensive computationally, yet give predictions to within 5% of the full discrete particle calculations for the monolithic and sandwich beams and plates. These foam projectile calculations suggest that metallic foam projectiles can be used to simulate the loading by sand particles within a laboratory setting.

Sensitivity analysis of sandwich beams and plates accounting for variable support conditions

Abstract The paper addresses the problems of the sensitivity analysis and optimal design of multi-span sandwich panels with a soft core and flat thin steel facings. The response functional is formulated in a general form allowing wide practical applications. Sensitivity gradients of this functional with respect to dimensional, material and support parameters are derived using adjoint variable method. These operators account for the jump of the slope of a Timoshenko beam or a Reissner plate at the position of concentrated active load or reaction, thus extending the sensitivity operators known in literature. The jump of slope is the effect of shear deformation of the core. Special attention is focussed on sensitivity and optimisation allowing for variable support position and stiffness, because local phenomena observed in supporting area of sandwich plates often initiate failure mechanisms. Introducing optimally located elastic supports allows to reduce the unfavourable influence of temperature on the state of stress. Several examples illustrate the application of derived sensitivity operators and demonstrate their exactness

Multi-objective optimization of laser-welded steel sandwich panels for static loads using a genetic algorithm

We present a methodology for the multi-objective optimization of steel sandwich panels for prescribed quasi-static loads. The steel sandwich panels consist of prismatic V-cores that are bonded to the facings using laser stake welds. Candidate sandwich panel designs are analyzed using geometrically nonlinear finite element analysis. The finite element model is validated by comparing the deflection and stresses for a representative sandwich panel with published experimental and numerical results. Sandwich panels are optimized for multiple, conflicting objectives using an integer-coded non-dominated sorting genetic algorithm. The methodology is illustrated through two optimization case studies. In the first study, we consider a rectangular steel sandwich panel configuration in which the facing segments are bonded to the core segments using double welds and optimize the panel geometry to minimize its deflection and mass. The second optimization study concerns a square steel sandwich panel in which the facings are bonded to the core segments using a single weld. The results demonstrate that the proposed methodology can be used to design lightweight laser-welded steel sandwich panels with superior structural performance.