Behavior Of Sandwich Panels Research Articles

The bending of 3D-printed bio-inspired sandwich panels with wavy cylinder cores

Beetle Elytron Plates (BEPs) represent a new class of biomimetic sandwich cores with excellent mechanical properties inspired by the microstructure of the beetle elytra. The cores have a hexagonal centre-symmetric configuration with through-thickness cylinders in the unit cell. In this work, we describe the behaviour of sandwich panels with novel BEP core configurations possessing wavy cylinders under four-point bending tests. Full-scale simulations are also carried out to validate the experimental data. The results show that all the sandwich panels produced with face skins adhesively bonded have material failure earlier than the adhesive bond failure. BEPs with wavy cylinders have larger peak loads compared to those with straight cylinders, and all BEPs show higher peak loads than those of sandwich panels with classical hexagonal honeycombs. Additionally, all the BEPs exhibit an enhanced ductility compared to honeycomb sandwich panels.

Low-velocity impact response of sandwich plates with corrugation star-shaped honeycomb hybrid core

Compared with traditional lightweight corrugation and honeycomb cores, the novel cellular structure exhibiting a negative Poisson's ratio possesses distinctive mechanical deformation features, making it suitable for modeling lightweight sandwich structures. Therefore, the concept of combining the auxetic honeycomb core with folded corrugations is proposed to construct a new type of corrugation star-shaped honeycomb (SSH) hybrid core for studying the dynamic behavior of sandwich panels subjected to low-velocity impact. Integrate Hertz elasticity theory and first-order shear deformation theory (FSDT) to develop an equivalent analytical model, and derive the equations of motion through Hamilton principle. To model contact force interactions during dynamic processes, a spring-mass model is utilized. Analytical solutions are derived for predicting transverse displacement with Duhamel's principle and Navier's method. Numerical simulations are conducted using the Abaqus commercial software, and the validity of the results is confirmed by comparing them with findings in the existing literature. Based on this, effective strategies for enhancing the sandwich panel's resistance to low-velocity impacts are proposed by examining the influence of different side length ratios, thickness ratios, and cell concave angles. In comparison to the corrugation re-entrant hexagonal honeycomb hybrid core sandwich panel structure, the corrugation SSH hybrid core sandwich panel structure reduces transverse displacement by 33.6 % at the same impact velocity.

Designing a Stiffener Layout that Resists the Wrinkling Behaviors of Sandwich Panels

Designing a Stiffener Layout that Resists the Wrinkling Behaviors of Sandwich Panels

Mechanical behavior of GFRP-Polymer sandwich composites with montmorillonite nanoclay

Abstract A sandwich composite consists of high stiffness and high strength outer layers called face sheets and low-density inner layers called core. In the present study, the sandwich composites comprising glass fabric/epoxy face sheets and epoxy modified with montmorillonite (MMT) nanoclay core are fabricated by a co-curing method. The sandwich panels show higher static tensile and three-point flexural properties such as ultimate strength, elastic modulus, and failure strain on adding up to 3 wt.% of MMT nanoclay contents than pristine sample. The former properties reduce at 4 and 5 wt.% of nanoclay contents owing to the formation of clustering of clay particles within the matrix. The stress-strain behavior of sandwich panels with 0–5 wt.% of MMT nanoclays obtained by laminated plate model follows experiments. The maximum lateral deflection of sandwich panels with nanoclays predicted by assuming them to be a simply supported beam is in-line with experimental results. For low-velocity single impact perforation load, the maximum force of sandwich panels improves on the infusion of up to 3 wt.% of clay while maximum displacement decreases. The ballistic limit velocity and energy absorption of panels improve on adding up to 3 wt.% of clay. Beyond the ballistic limit at different initial velocities, the residual velocity of sandwich panels decreases on addition of up to 3 wt.% of clay and energy absorption increases.

Buckling behavior of rotor blade sandwich panels with spatially distributed material uncertainties

The study evaluates the impact of material uncertainties on the buckling behavior of sandwich panels in wind turbine rotor blades. The analysis is limited to linear buckling and is performed using stochastic finite element Monte Carlo simulation on a rectangular and flat submodel of the rotor blade’s trailing edge panel. The finite element model of the panels is simply supported on all edges. To generate the spatial material property distributions, the Karhunen-Loève expansion is used in combination with Latin hypercube sampling. The results compare the effects of various correlation lengths of the spatial distributions. The buckling loads vary in correlation to the average panel stiffness caused by the random distributions. The spatial distribution has a less dominant effect, reducing the mean value of the buckling load results. The amount of reduction in buckling load is highest when the correlation length of the distribution is close to the harmonic half-wave of the dominant buckling shape.

Mechanical Analysis of Sandwich Plates with Lattice Metal Composite Cores

This study investigates the modal and static behaviour of sandwich panels with lattice core structures, comparing the real cellular solid structures’ response with an equivalent homogenised model. The mechanical model has been described through the Finite Element Method (FEM), and 3D elements with reduced integration have been employed to guarantee an accurate description of skins and the lattice geometry. Different Body Centred Cubic (BCC) cell configurations have been considered: standard metal BCC cell, metal BCC cell with waved struts, standard metal composite BCC cell. Depending on the configuration, the homogenised materials showed isotropic or orthotropic properties. The composite core has been modelled using two different materials, namely an Aluminium matrix with an AlSiC filler, which is enclosed inside the other hence constituting the BCC cell’s strut. A free-vibration and static analysis parametric study has been conducted varying the strut’s diameter, the strut’s waviness and the thickness ratio of the composite struts. For the static analysis, a multiscale approach has been adopted; a first step considering the whole homogenised sandwich panel and a second step comparing the multiscale results of the homogenised model and those of real structure considering a small portion of the panel. Results reveal insights into the effects of core structure parameters on the mechanical response of sandwich panels, aiding in design optimisation and structural enhancement.

Aeroelastic analysis of a lightweight topology-optimized sandwich panel

Sandwich structures with lattice cores are novel, lightweight composite structures and are widely used in the aerospace industry. Besides, the aeroelastic behavior of sandwich panels in a supersonic flow regime still needs to be thoroughly studied. This work investigates the supersonic flutter of a sandwich panel whose core is topology-optimized. A finite element model of a sandwich panel based on the layerwise theory, coupled with the first-order piston theory, is presented. The sandwich panel core is assessed using a topology optimization approach with flutter loading constraints. The subsequent analytical homogenization scheme is developed to provide the equivalent mechanical properties of the topology-optimized panel. The modeling approach is fully validated, and the results demonstrate that the sandwich panel is capable of enlarging the flutter-free operational flight range when compared with other conventional panel designs. A parametric analysis of the topology-optimized sandwich panel regarding the critical flutter conditions is performed.

Effects of various parameters on the mechanical properties of composite lozenge‐shaped core sandwich panels subjected to flat‐wise compression test

AbstractThis paper studied the compressive behavior of a composite sandwich panel with a lozenge‐shaped core reinforced with graphene nanoparticles (GNPs) under different conditions. The fabrication process involves the utilization of Kevlar fibers and epoxy resin to construct the sandwich panels, followed by introducing polyurethane (PU) foam through vacuum‐assisted resin transfer molding (VARTM). Flat‐wise compression testing is conducted to assess the mechanical properties and behavior of the sandwich panels. The study investigates the effect of various parameters, including core angle, core height, weight percentage (wt%) of GNPs, and PU foam, on the compressive strength of the structure. The experimental results are validated through finite element simulation using ABAQUS software, and a satisfactory agreement is observed between the simulated and experimental data. The research findings indicate that the inclusion of 3 wt% of GNPs in the structure leads to a notable 25% enhancement in the compressive strength of the sandwich panel. However, when the GNP content was further increased to 0.4 wt%, a contrasting trend was observed and the strength of the structure decreased by about 12%. Furthermore, an increase in the core angle is associated with a substantial 46% improvement in the sandwich panel's strength. Conversely, an increase in the core height is found to cause an 18% reduction in the sandwich panel's strength. Also, the addition of PU foam results in a significant increase of approximately 42% and 58% in the strength and energy absorption of the sandwich panel, respectively. This comprehensive parametric study offers valuable insights to engineers and designers seeking to construct sandwich panels with optimal strength against compressive loads.Highlights Adding GNPs modifies the mechanical properties of the sandwich panel. Adding 0.4% of GNPs leads to the reduction of the structure's strength. Increasing the core angle increases the sandwich panel's strength. Increasing the core height decreases the sandwich panel's strength. PU foam significantly increases the sandwich panel's strength.

Dynamic behaviors of sandwich panels with 3D-printed gradient auxetic cores subjected to blast load

This study experimentally and numerically investigated the blast resistance of sandwich panels composed of steel face sheets and 3D-printed gradient auxetic chiral core. Five gradient strategies were utilized in the design of auxetic core, including uniform gradient, positive gradient, negative gradient, center positive gradient and center negative gradient. Varying blast loadings were applied by adjusting the masses of explosive charges. The deformation/failure modes of sandwich panels were obtained in the experiments, in terms of the face sheets and gradient auxetic core. The effects of impulse and gradient type of auxetic core on dynamic responses of specimens were examined. In addition, the numerical simulation was employed to clarify the deformation process of sandwich panel, and to analyze the deformation mode of auxetic cores under sufficient compression. It was shown that higher impulse was associated with increased plastic deformation in the face sheet and more serious shear and tensile tearing within the auxetic core. The auxetic cores of varying gradient types displayed distinct compress deformation behaviors. Among them, the negative gradient variant exhibited the least permanent deflection, and the superior negative Poisson's ratio effect, indicating enhanced blast resistance. This work not only contributes to a strategy for designing gradient auxetic cores with enhanced blast resistance, but also provides valuable insights into experimentally understanding the response of complex auxetic configurations under blast loads.

Sandwich panel behavior under low-velocity impact with polyurethane core

In this article, the aim is to numerically and experimentally investigate the energy absorption of sandwich panels composed of polyurethane foam cores and composite facesheets consisting of epoxy resin reinforced with Kevlar® 29 fibers with different numbers of layers under low-velocity impact. Therefore, factors influencing energy absorption in sandwich panels, such as the density of foams, the arrangement of foam layers, core thickness, and the number of composite layers in the skins, were investigated. Additionally, the damage modes occurring in the composite facesheets were examined. Damage initiation in the composite facesheets is predicted using the three-dimensional Hashin criterion with VUMAT coding, and cohesive elements model interlayer delamination. The results show strong agreement between numerical simulations and experiments. Key parameters such as contact force–time curves, the maximum force needed to initiate damage in composite layers, energy absorption, and SEA are analyzed. Among the experimental samples, increasing the number of composite layers had a greater effect on the overall energy absorption of sandwich panels compared to increasing the thickness of foam cores. However, increasing the number of composite layers in the facesheets performed poorly in terms of improving the SEA parameter. Notably, panels with integrated cores at a density of 75 kg/m³ exhibit the highest energy absorption at 11.7868 J. Moreover, increasing the number of composite layers on the back facesheet results in a 4.94% and 6.96% energy absorption increase compared to panels with more composite layers on the upper facesheet or an equal distribution between the upper and lower facesheets.

Material Behavior of PIR Rigid Foam in Sandwich Panels: Studies beyond Construction Industry Standard.

A deep understanding of the material parameters and the behavior of sandwich panels, which are used in the construction industry as roof and façade cladding, is important for the design of these construction components. Due to the constant changes in the polyurethane (PU) foams used as a core material, the experimental database for the current foams is small. Nowadays, there is an increasing number of failures of façade and roof panels after installation. This article presents a variety of experimental investigations on sandwich panels from two manufacturers with a core of polyisocyanurate (PIR) rigid foam (density: 40 kg/m3). As part of this study, compression, tension, shear, and bending tests were performed in several spatial directions and over the range required by the standard. The results of the tests showed the orthotropy of the core material and the dependence of the material on the direction and type of load. The stress-strain curves showed linear and non-linear areas. Using the data from this experimental study, a numerical model was implemented which utilized the Hill yield criterion to represent the orthotropy of the core material. The present investigation suggests that the classical von Mises failure criterion, used in many studies, is not suitable for the foam system applied in these sandwich panels. Instead, the Tsai-Wu criterion is more appropriate for defining the failure stresses.

Experimental and numerical investigation of impact behavior in honeycomb sandwich composites

This paper presents an experimental and numerical study on the low-energy impact fatigue and bending behavior of sandwich panels reinforced with composite laminate glass and carbon fabric facesheets, supported by a honeycomb core made of Nomex. The crushing behavior of honeycomb sandwich specimens subjected to the impact test was compared and discussed. Our results indicate that the carbon composite facesheets have a significant effect on the impact, resulting in an increase in impact resistance and a 157.14% increase in crack depth in the elastic region compared to glass facesheets reinforcement. This increase serves as an indicator of the laminate's ability to resist damage initiation and impact fracture mechanisms. Also, an increasing in flexural strength about 45.72% was observed in carbon facesheets honeycomb specimens compared to glass facesheets reinforcement. Microscopic illustration of the damaged honeycomb sandwich specimens was conducted to evaluate the interfacial characteristics and describe the damage mechanics of the composite facesheets and core adhesion under the impact test. The numerical approach proves to be efficient in terms of accuracy and simplicity compared to existing methods for predicting the damage mechanisms of honeycomb sandwich structures. It was noted that results of numerical study show best agreements with experiment results and the model can be used to predict the low-energy impact fatigue.

Evaluation of corrugated core configuration effects on low-velocity impact response in metallic sandwich panels

Abstract Sandwich panels are used as body components of vehicles in many sectors, such as defense, aircraft, and aviation, due to their advanced mechanical properties and lightness. This study aims to investigate the effect of core configurations on mechanical performance and deformation behavior of metallic sandwich panels under low-velocity impact loading. For this purpose, metallic sandwich panels having monolithic and sliced core configurations were first produced. Low-velocity impact tests were carried out using varying energy levels (20, 40, 60 J) to examine how the intensity of influence affects the deformation of the sandwich panel. The perforation and deformation behavior on the upper surface plates of sandwich panels were evaluated. Experimental results showed that the core design significantly affects the impact behavior of sandwich panel samples. The sliced core configuration produced approximately 10 % more maximum contact force and absorbed 14 % more impact energy at high-impact energy levels. Additionally, the sliced core configuration delayed core collapse of the core in deformation situations where complete perforation does not occur.

Deformation behavior of super-austenitic stainless steel sandwich panels subjected to air blast and underwater explosion

Super-austenitic stainless steel is a class of high alloy steels with enhanced toughness, outstanding strength, and corrosion resistance. In this article, the structural integrity of super-austenitic stainless steel square sandwich panels subjected to surface and underwater explosions is investigated through numerical simulations, and the results are validated with experiments. Abaqus Explicit Solver is used to predict the face deformation and core crushing failure modes of the sandwich panels. Simulations are performed for three levels of impulse load by varying the explosive quantity. The fluid-structure interaction is established by CONWEP and UNDEX algorithms for air blasts and underwater explosions respectively. The dynamic deformation behavior of the sandwich panel is modeled using the Johnson-Cook (JC) plasticity model incorporating strain rate and temperature effects. Good agreement is witnessed between the numerical predictions and experimental observations. An increment in deformation of the face sheet, cell wall buckling, and core compaction is observed with the increase in the impulse. From a series of air and underwater explosion simulations, the advantage of using sandwich structures for blast mitigation is demonstrated. In addition, the significance of numerical simulations to limit experiments and predict the deformation of the sandwich panels is presented.

Experimental and Numerical Assessment of Flatwise Compression Behaviors of Sandwich Panels: Comparison Between Aluminum, Innegra Fiber and Glass/Epoxy New Symmetric Lattice Cores

Experimental and Numerical Assessment of Flatwise Compression Behaviors of Sandwich Panels: Comparison Between Aluminum, Innegra Fiber and Glass/Epoxy New Symmetric Lattice Cores

Optimization of mechanical behavior of sandwich panel with prismatic core based on yield and buckling constraints using the teaching-learning-based optimization algorithm

Optimization of mechanical behavior of sandwich panel with prismatic core based on yield and buckling constraints using the teaching-learning-based optimization algorithm

Influence of Temperature on the Behavior of Sandwich Panels

AbstractSandwich panels in the construction industry are used as roof and facade elements and usually consist of two thin face layers of steel and a thicker core of polyurethane (PU) or mineral wool in between. The PU core material is constantly being further developed. In addition to improvements in the physical properties, this further development also leads to changes in the mechanical properties. As a result, the design rules that were established for older foam systems must be reviewed at regular intervals. There is a great need for research into the temperature‐dependent behavior of the foam system. As these elements are used as roof and facade elements, they are directly exposed to climatic conditions. High temperatures are generated on the cover sheets due to solar radiation. The PU rigid foam changes its mechanical properties in this temperature range. Tests on small parts and components show a change in the stiffnesses and strengths, as well as the load‐bearing behavior under elevated temperature. Consideration of the temperature in the design is therefore of great importance. In view of the continuous further development of the foam system, statements regarding the core material from older research must be reconsidered.

Investigations on the stability behaviour of axially loaded sandwich panels with integrated longitudinal profiles

AbstractThis paper presents investigations on the load‐bearing behaviour of sandwich panels under bending load and axial load. The sandwich panels investigated here have the special feature that they consist of two face sheets, a polyurethane core and two integrated reinforcement profiles. These integrated profiles allow the stiffness of the panels to be significantly increased, resulting in a delayed wrinkling failure and thus opening up new fields of application. Experimental results from bending tests are presented. From these results, analytical approaches are then described that can be used to predict the load‐bearing behaviour under axial loading. In addition, the test setup is described, which will be used in the future for the experimental investigation of the panels under axially loading.

Influence of core topology on blast mitigation application of multi-layered honeycomb core sandwich panel

In the past years, the aluminium honeycomb core sandwich panel has emerged as a promising blast mitigation solution owing to its high energy absorbing capacity under impulsive loading. To enhance its performance against the blast load, it is important to understand the mechanical behaviour of honeycomb core sandwich panel with varying core configurations. The present study investigates the difference in load mitigation behaviour of sandwich panel under blast loading with different honeycomb core topologies. Three types of honeycomb core topology i.e., square, circular, and hexagonal are considered in the present study. The performance of the sandwich panels under blast loading is compared for two criteria i.e., constant mass (or aerial density) and constant cell size. The influence of a multi-layered core along with the intermediate sheets on the blast resistance of sandwich panel is further examined under blast load. It is observed that the multi-layered core and intermediate sheets not only strengthen the sandwich panel but also make it significantly stronger under the blast loading in comparison to the single layer sandwich panel. The role of intermediate sheets in energy dissipation is observed to be insignificant in multi-layered sandwich panel for the parameters considered in this investigation. Further, it is observed that the difference in energy dissipated by front face sheet and back face sheet is increased with increase in the number of layers of cores.

Numerical and Experimental Study on Loading Behavior of Facade Sandwich Panels

This paper focuses on the study of the strength of facade sandwich panels used in building construction. The paper describes the results of experimental and numerical research on the behavior of sandwich panels made of polyisocyanurate core (PIR) and their structural connections when exposed to tensile and compressive loads. In the initial phase of this study, laboratory tests were performed to determine the physical and mechanical characteristics of the material from which the sandwich panels are made. Laboratory tensile and compression tests were performed on small samples of sandwich facade panels. In order to verify the obtained results, they were compared with the numerical analysis performed in the ANSYS software. The numerical model was found to accurately predict the results of the laboratory tests, suggesting that the model can be used to predict the behavior of these panels under different loads in service. The study showed that the foam core sandwich panel exhibits excellent mechanical properties. The results indicate the suitability of foam-based composite structures in the construction industry for various applications, such as roof and wall structures. The findings of this study may help in the development of lightweight and durable construction materials for the industry.