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This 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. [ABSTRACT FROM AUTHOR]

Strong earthquake loads can cause significant damage to buildings, but even moderate earthquakes with higher return periods are socially relevant as they may cause both infrastructure and economic failures. In an ongoing German nationally funded research project, the behavior of facade elements in lightweight metal construction under in‐plane deformation is currently being investigated with the aim to assess the response and the energy dissipation capacity in the case of seismic events. As past research results indicate the contribution of wall and roof elements to the stiffening of buildings, with the possible consequence of increased earthquake loads due to the natural frequency change, a novel approach for increased resilience of structures with building envelopes in lightweight metal construction may be developed. On the basis of a series of experimental tests, under monotonic and cyclic loading, the effects of in‐plane deformation were studied separately from external influences such as wind and thermal loads. This paper presents: (i) a brief state of the art; (ii) a description of the research framework; (iii) the experimental program; (iv) the specimen configuration, test set‐up, loading protocol and instrumentation; (v) the response under monotonic and cyclic loading; (vi) the main conclusions, as well as the ongoing and future research activities. [ABSTRACT FROM AUTHOR]

The total shear force induced on a profiled sandwich panel by an external load is distributed between the profiled face and core. Sandwich panel with a discrete core material such as mineral wool consists of multiple transverse lamella joints across the full width of the panel, affecting the overall shear performance of the panel as these joints have negligible resistance to shear. Additionally, in some cases the core material is partially bonded only to the lower flange of the profiled face which increase the concentration of stresses in the bonded area leading to the crushing of the core on the support. This work studies the distribution of shear force in mineral wool core sandwich panels with one profiled face utilizing a shear beam test on a specimen cut from the panel including the profiled part. Based on the results and failure modes obtained, this work investigates the behavior and role of the profiled face on the shear resistance of profiled sandwich panels. The distributed shear force between the core and profiled part obtained from the shear beam tests are compared with full‐scale tests suggested by the European Standard EN 14509:2013, thus, exploring the applicability of the devised shear beam test method for assessing the shear properties of profiled sandwich panel. [ABSTRACT FROM AUTHOR]

Lightweight steel constructions made of sandwich panels are an economical solution for wall and roof claddings, especially in industrial construction. The panels consist of two thin sheets of steel and a core with thermal insulating properties. In the mounted state and at high temperatures on the outer face of the panel, damage to the components may occur due to blister formation. In a current research project, the influence of defects in sandwich panels with a PIR‐foam core is examined. This article presents the results of experimental tests regarding the influence of various parameters, such as face temperature, production defects and design of the longitudinal joint on blistering in sandwich wall panels with a PIR‐core. The aim is to identify the necessary conditions for the occurrence of blisters. Using an optical strain measuring method (Digital Image Correlation), the temperature‐induced deformations and strains in the covering nose of sandwich wall panels with hidden fastening are measured and will be analyzed with regard to blistering. First results reveal a significant dependence on the geometry and design of the covering nose. [ABSTRACT FROM AUTHOR]

Sandwich 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. [ABSTRACT FROM AUTHOR]

The paper presents results of a research on robustness of sandwich panels subjected to the accidental load – impact blast wave. The accidental design situation is understood as an unexpected explosion of gas cylinders located in the neighbourhood of the building. Full‐size sandwich panels with lightly profiled, thin‐walled, steel facings and thick softcore were used in the experiments. The conducted field tests allowed for FE model validation in Abaqus/CEA environment. During the experiments, the two high‐speed cameras have been used to record the behavior of the sandwich panel. Furthermore, the failure mechanisms of the sandwich panels and fasteners were also revealed. The research outcomes are based on both field experiments and numerical simulations. [ABSTRACT FROM AUTHOR]

The paper presents theoretical, experimental and numerical studies on the thermal behavior of mineral wool used in sandwich panels. The aim of this study is to investigate the thermal properties of mineral wool at elevated temperatures and provide a simple model that would allow us to determine the heat propagation in sandwich panels during a fire. The paper proposes a new method to experimentally evaluate thermal diffusivity, derived from theoretical premises. Experiments are conducted in a laboratory furnace where specimens are placed and temperatures inside specimens are measured. Different methods are used to process the test results and calculate the thermal diffusivity of mineral wool. Finally, a numerical analysis of heat transfer using the finite element method (FEM) is performed to validate the obtained thermal properties. [ABSTRACT FROM AUTHOR]

Shape memory alloys, especially in the form of wire, can provide structures with magnificent improvements in buckling and frequency responses. The SMA's ability to recover its original shape can produce a sizable amount of recovery stress, resulting in enhancing natural frequency and critical temperature and lowering the maximum deflection of structures. In this study, in addition to considering the effects of SMA presence in double-curved sandwich plate on the aforementioned characteristics, the influences of heat treatment of curing SMAs on their properties, calculated by differential scanning calorimetry (DSC) and tensile testing, and sandwich structures will be considered. Furthermore, the effects of recovery stress, the volume fraction, and the position of SMA wires on thermal and mechanical stability will be studied. The Boyd & Lagoudas SMA constitutive model is utilized in the ABAQUS UMAT subroutine.

The explosion products, such as shock waves, fragments and heat energy formed by explosion, act on the plate structure, which may cause structural damage, material failure and even phase transformation of material. In this paper, the damage mechanism and protective effect of near-field blast load on sandwich structure based on foam-nickel core material were studied. Firstly, the near-field explosion test was conducted to investigate the blast response of the foam-nickel sandwich structure subjected to blast shock from 8701 explosive at near-field position. The deformation characteristics and stress history of the sandwich structure on the acting location of blast load were carefully investigated via experimental methods. A finite element model of near-field explosion was established for effective numerical modelling of the dynamic behaviour of the sandwich structure using the explicit dynamics software ANSYS/LS-DYNA for more comprehensive investigations of the blast shock response of the sandwich structure. The finite element model is reasonable and validated by mesh independence verification and comparing the simulated response behaviour to that from the experimental results for the sandwich structure subjected to near-field blast load. On this basis, the damage mechanism and protection effect of the near-field explosion impact on foam-nickel cores with different density and porosity are simulated more systematically. The investigated results from the experiments and a series of numerical simulations show the large deformation effect due to the extensive energy absorption, which suggests that the sandwich structure based on foam-nickel core material may be expected to become a new choice of protective structure under near-field blast load. [ABSTRACT FROM AUTHOR]

Additive manufacturing enables the fabrication of strut-based lattices that consist of periodic representative volume elements (RVE) and can be used as cores in sandwich panels. Due to the design freedom provided by additive manufacturing, the lattice strut diameter may vary through the lattice. Thus, the diameter distribution can be adapted to the stress variation in the sandwich core to achieve an efficient core design and avoid oversizing the core. Such grading approaches are required when the core is subjected to localized loads, e.g., near support points and load application areas. In this work, an analytical model is derived to determine stresses and deformations in lattice struts of RVE-based graded lattice cores in elastic sandwich panels using homogenization and dehomogenization methods. In contrast to already available models, the analytical model presented in this work allows grading the lattice strut diameter both along the sandwich length and through the core thickness. Furthermore, local stresses in the lattice struts caused by concentrated load application can be captured adequately by the present model. To highlight the benefits of graded cores, the strut stress distribution in graded cores is compared to the stress distribution in homogeneous cores. [ABSTRACT FROM AUTHOR]

Origami foldcore structures can be used in thin-walled sandwich panels to provide unique advantages over traditional honeycomb structures. For instance, their continuously connected space is available for flowing through cooling liquid or compact pipeline placement. However, origami foldcores suffer from relatively low-energy absorption. This paper proposes a new design of energy-absorbing foldcore structures for sandwich panels, including the geometric design, experimental tests, numerical parametric study, and theoretical estimation of energy absorption. Origami initiators are introduced to the Miura foldcores to induce a failure mode with more transverse folds, which is not common for regular foldcore structures. As a result, 60% higher energy absorption and tunable load uniformity can be achieved. [ABSTRACT FROM AUTHOR]

The paper presents the basic principles of static calculations of plates with discrete filling–ribs; the method is based on the analytical solution of the problem of the stress state of a ribbed plate. The bottom line is to use special discontinuous functions at the stage of writing the initial assumptions of differential equations, as well as in the process of solving them due to the nature and physical meaning of the problem. [ABSTRACT FROM AUTHOR]

The present paper has experimentally determined the flexural strength of a glass fiber reinforced polymer sandwich panel with a novel M-shaped lattice core reinforced by nano-silica (nano-SiO2). For this purpose, a polymer composite sandwich panel with an M-shaped core made of glass-epoxy fiber has been fabricated in this experiment using the vacuum-assisted resin transfer molding method. Afterward, polyurethane foam (PU) was injected into the empty space of the sandwich panel. In order to determine the flexural strength of the sandwich panels, they have been subjected to three-point bending and compressive loads. From the results of the study, it was figured out that: (a) Adding 1–3 wt% of nano-silica into the glass fiber had the most desirable effects on the enhancement of flexural strength of the sandwich panels (b) PU has improved the flexural strength of sandwich panels (c) The new M-shaped core can well postpone the buckling and failure of the composite sandwich structures. [ABSTRACT FROM AUTHOR]

A homogenization method for the vibration analysis of periodic sandwich panels is presented. Periodic boundary conditions are applied to a representative volume element (RVE) of the structures. The complex responses of the RVE under eight sinusoidal excitations are calculated and the complex stiffness matrix of the sandwich panels is obtained by the direct-solution steady-state dynamic analysis (DSDA) using the finite element method (FEM) in the frequency domain. Based on equivalent single-layer (ESL) theory and finite element-modal strain energy (FE-MSE) method, the natural frequencies, the mode shapes and the loss factors of the structures are obtained by shell models. The effectiveness of the homogenization method is validated by using pyramidal lattice truss sandwich panels made of carbon fiber reinforced plastics (CFRP). The results obtained by the homogenization method are compared with those obtained by experiments and solid models. The effects of the number of cells and damping layers are discussed. [ABSTRACT FROM AUTHOR]

In the paper there the laboratory tests of interaction between thin-walled beams of the Z crosssection and the sandwich panels with PIR foam core are presented. The different numbers of connectors (0, 4, and 8) were used to connect the sandwich panels with the thin-walled beams. Furthermore, the parallel and perpendicular to the longitudinal axis of the thin-walled beam load arrangement was analysed. The research provides a qualitative and quantitative comparison of the mentioned experiments using the ultimate capacity, the deformation capacity, and the stiffness. In the second part of the paper, the numerical analysis of the thin-walled beam was also performed. The beam was modelled as a shell element and loaded in two ways, which corresponded to the loading scenario during laboratory tests (uniformly distributed and concentrated loads). The results of the numerical calculations of the beam without lateral stabilization were compared with the laboratory results of the beam stabilized by the sandwich panels.

Sandwich panels have wide applicability in blast- and impact-resistant design of structures due to their phenomenal energy absorption capacity, albeit being considerably light in weight. A sandwich panel consists of core(s) and facesheets, wherein the core contributes majorly to the energy absorption capacity and the facesheets contribute the stiffness of the sandwich panel. The dynamic response of sandwich panel subjected to blast and/or impact loads can be obtained with the help of analytical solutions, experiments/tests, and finite element analyses. In this article, the influence of the variations in the geometry and material of the different components of a sandwich panel, on the overall dynamic response of the panel is reported extensively based on the studies conducted so far. Moreover, a comprehensive review is conducted on the behavior of sandwich panels with respect to the various shapes of cores and facesheets, different types of core grading, and the use of stiffeners. This state-of-the-art review also gives a clear insight on the various available and widely used experiment/test setups and finite element tools for conducting blast and impact test/analysis on sandwich panels. [ABSTRACT FROM AUTHOR]

With the rising demand for lightweight and high-performance shielding systems, sandwich panels made of thin rigid face sheets and cellular material cores have recently received much attention. The present study aims to investigate the perforation behaviour of lightweight sandwich panels made of fibre reinforced composite face sheets and aluminium foam core under quasi-static and dynamic testing conditions. A particular focus is made on the fibre hybridization effect on the overall panel behaviour. Impact perforation tests were conducted using an inverse perforation technique. Instead of conventional free-flying projectile impact tests, studied samples are fixed in a hollow projectile. Then, this assembly is accelerated toward an instrumented steel perforator replacing the incident bar of a split Hopkinson pressure bar. Consequently, this modified split Hopkinson pressure bar system can be used as both a perforator and a measuring device. Therefore, the piercing force-displacement curves, the energy absorption capability as well as the penetration and damage mechanisms of the tested panels was analysed and compared to quasi-static perforating tests. To better assess the testing results, quasi-static tensile and bending tests were carried out on the face sheets materials. Moreover, quasi-static and dynamic compression tests were performed on the aluminium foam core using conventional test methods and direct split Hopkinson pressure bar. Unlike the aluminium alloy face sheets, the experimental findings revealed that the sandwich panels with composite face sheets demonstrated higher rate sensitivity, better perforation resistance and specific energy absorption capability. Results have also shown that the hybridization of carbon and glass fabrics combined their best tension and bending properties as well as their higher dynamic strength, which has increased the sandwich panel's perforation resistance. [ABSTRACT FROM AUTHOR]

Sandwich panels have the potential to serve as plastically deforming sacrificial structures that can absorb blast or impact energies. Auxetic sandwich panels with welded or bolted corrugated layers have, as far as the author is aware, had their blast behaviour thoroughly addressed in the literature. Therefore, the objective of this numerical analysis was to create a novel, low-cost, simple-to-build graded sandwich panel with detached corrugated layers that may be employed as a multi-purpose sacrificial protective structure against a wide range of blast threats. The suggested sandwich panel has overall dimensions of 330x330x150mm and is made of six detached aluminium (AL6063-T4) layers enclosed in a steel (Weldox 460E) frame. With different stepwise plate thicknesses of 0.4, 0.8, and 1.2mm for each pair of layers, the six layers all have the same re-entrant auxetic geometry. Utilising the Abaqus/Explicit solver, the numerical analysis was carried out. A wide variety of blast intensities (4, 7, 11, 13, and 16 MPa peak reflected overpressures) were tested on the suggested auxetic sandwich panel, and the results showed uniform progressive collapse, a superior decrease in reaction forces, and greater energy dissipation compared to comparable non-auxetic topologies. The innovative sandwich panel design has potential uses for both military and civic structures that need to be protected. [ABSTRACT FROM AUTHOR]

To protect the airframe and the payload of hypersonic cruise vehicles from aerothermal heating and aerodynamic loading, metallic thermal protection systems (MTPS) are intended to be used. MTPS are composite structures containing a combination of insulating material and two sandwich panels placed on top and bottom of it. There are numerous design factors influencing the (a) thermal performance and (b) density of these sandwich panels (SP). In the current study, the effect of six important geometric design parameters of nickel alloy C263 sandwich panel viz., (A) core cell shape, (B) core cell size, (C) core cell height (D) core sheet thickness, (E) top and (F) bottom face sheet thickness were evaluated and analysed using Taguchi-based design of experiments (DOE) approach. The results obtained were analysed using standard statistical analysis techniques in order to identify the optimum combination of design parameters and to ascertain the influence of each aforementioned design parameters on the performance of C263 sandwich panels. Further, the optimum combination of sandwich-panel design parameters that provides the best thermal performance with lowest density has been identified using an algebraic model and validated. The results obtained are presented and discussed here. [ABSTRACT FROM AUTHOR]

Sandwich panels are one form of composite structures that are widely used. The objective of this study was to investigate the effect of three types of resin: urea formaldehyde (UF), melamine formaldehyde (MF) and the combination of urea formaldehyde + melamine formaldehyde (UF + MF) and two core layer densities (400 and 500 kg/m³) on physical and mechanical properties of sandwich panels made of date palm leaves waste. Press pressure, temperature, and time for all panels were 175°C, 35 kg /cm² and 9 minutes, respectively. The final thickness of all panels was selected as 25 mm. Physical and mechanical properties including water absorption (WA), thickness swelling (TS), modulus of rupture (MOR), modulus of elasticity (MOE), impact bending strength (IBS) and internal bonding (IB) of the samples were measured. The results showed that there was a significant difference between the values of different treatments. Physical properties (except thickness swelling) and mechanical properties of panels with a density of 500 kg/m³ was improved. The use of MF and UF + MF resins significantly improved the physical and mechanical properties of sandwich panels. [ABSTRACT FROM AUTHOR]

In this work dynamic response of trapezoidal corrugated core sandwich panels subjected to oblique blast loading are studied both numerically and experimentally. The stand-off distance which has been determined from sandwich panel to center of the nearest face of the explosive cylinder is considered 300 mm. the experiments was performed at Four blast tube with different included angles of 0°, 15°, 30° and 45° respect to sandwich target plate. The results of numerical simulation, obtained using coupled Eulerian - Lagrangian (CEL) method at ABAQUS/Explicit software. Maximum mid- point deflection of back and front faces are compared with experiment results. The results show that with increasing angle of tilt of explosive the amount of back face deflection at angles of tilt 15°, 30° and 45° respect to the case of 0°, 4.68%, 5.86% and 9.77% decreases respectively. It is found that at the z direction, deformation profile is completely dome-shaped while the profile in the x direction is almost conical. The achieved results can be used to optimization designing of military vehicles and employed for civil infrastructure. [ABSTRACT FROM AUTHOR]

The design of graded and multifunctional lattice cores is driven by the increasing demand for high-performance components in lightweight engineering. This trend benefits from significant achievements in additive manufacturing, where the lattice core and the face sheets are fabricated simultaneously in a single print job. This work systematically compares the mechanical performance of sandwich panels comprising various graded lattice cores subjected to concentrated loads. In addition to graded lattice cores, uniform lattices and conventional honeycomb cores are analyzed. To obtain an optimized graded lattice core, a fully stressed design method is applied. Stresses and displacements are determined using a linear elastic analytical model that allows grading the core properties in a layerwise manner through the core thickness. The analysis indicates the superior performance of graded lattice cores compared to homogeneous lattice cores. However, conventional honeycombs outperform graded lattice cores in terms of load-to-weight ratio and stiffness-to-weight ratio. This study provides valuable insights for the design of lattice core sandwich panels and the advantages of several design approaches.

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.

Recently, there has been a growing interest in the use of sandwich panels that, beyond handling well-known bending stress, can withstand torsional stresses. This is particularly relevant for wall applications when the panels are equipped with photovoltaic or supplemental curtain wall modules. This research article presents a detailed exploration of the structural behavior of eccentrically loaded sandwich panels, with a specific focus on warping torsion. Experimental and numerical studies were conducted on polyisocyanurate (PU) core sandwich panels, commonly employed in building envelopes. These studies involved various dimensions and material properties, while omitting longitudinal joints. The experimental study provided essential insights and validated the numerical model in ANSYS. Enabling parametric variation, the numerical analysis extends the analysis beyond the experimental scope. Results revealed a high degree of correlation between experimental, numerical, and analytical solutions, regarding the rotation, as well as the normal and shear stress of the panel. Confirming the general applicability of warping torsion in sandwich panels with certain limitations, the study contributes valuable data for applications and design of eccentrically loaded sandwich panels, laying the foundation for potential engineering calculation methods.

The utilization of the vegetal fabric-reinforced cementitious matrix (FRCM) represents an innovative approach to composite materials, offering distinct sustainable advantages when compared to traditional steel-reinforced concrete and conventional FRCM composites employing synthetic fibers. This article introduces a design for sandwich solutions based on a core of extruded polystyrene and composite skins combining mortar as a matrix and diverse vegetal fabrics as fabrics such as hemp and sisal. The structural behavior of the resulting sandwich panel is predominantly driven by the interaction between materials (mortar and polyurethane) and the influence of shear connectors penetrating the insulation layer. This study encompasses an experimental campaign involving double-shear tests, accompanied by heuristic bond-slip models for the potential design of sandwich solutions. The analysis extends to the examination of various connector types, including hemp, sisal, and steel, and their impact on the shear performance of the sandwich specimens. The results obtained emphasize the competitiveness of vegetal fabrics in achieving an effective composite strength comparable to other synthetic fabrics like glass fiber. Nevertheless, this study reveals that the stiffness of steel connectors outperforms vegetal connectors, contributing to an enhanced improvement in both stiffness and shear strength of the sandwich solutions.

This study prepares composite panels with three Polylactic acid (PLA)-based materials via the multi-material fused filament fabrication method. The influences of four processing parameters on the mechanical properties of 3D-printed samples are investigated employing the Taguchi method. These parameters include the relative volume ratio, material printing order, filling pattern, and filling density. A “larger is better” signal-to-noise analysis is performed to identify the optimal combination of printing parameters that yield maximum bending strength and bending modulus of elasticity. The results reveal that the optimal combination of printing parameters that maximizes the bending strength involves a volume ratio of 1:1:2, a material sequence of PLA/foam-agent-modified eco-friendly PLA (ePLA-LW)/glass fiber-reinforced eco-friendly PLA (ePLA-GF), a Gyroid filling pattern, and a filling density of 80%, and the optimal combination of printing parameters for maximum bending modulus involves a volume ratio of 1:2:1 with a material sequence of PLA/ePLA-LW/ePLA-GF, a Grid filling pattern, and 80% filling density. The Taguchi prediction method is utilized to determine an optimal combination of processing parameters for achieving optimal flexural performances, and predicted outcomes are validated through related experiments. The experimental values of strength and modulus are 43.91 MPa and 1.23 GPa, respectively, both very close to the predicted values of 46.87 MPa and 1.2 GPa for strength and modulus. The Taguchi experiments indicate that the material sequence is the most crucial factor influencing the flexural strength of the composite panels. The experiment result demonstrates that the flexural strength and modulus of the first material sequence are 67.72 MPa and 1.53 GPa, while the flexural strength and modulus of the third material sequence are reduced to 27.09 MPa and 0.72 GPa, respectively, only 42% and 47% of the first material sequence. The above findings provide an important reference for improving the performance of multi-material 3D-printed products.

Sandwich panels are used in various industries due to their high special strength. It is used in ultra-light aerospace structures. In this paper the protective effect of sandwich structures used in ultralight space structures against gamma rays is investigated. Eight structures of the most widely used structures used in space structures such as telecommunication antennas and satellite bodies are exposed to radioisotopic sources of gamma rays (Amercium barium and cesium) with energies of 60 kV, 80 kV, 382 and 66 kV, have been compared to each other. Surface material (aluminum and carbon), surface thicknesses and honeycomb cell dimensions are the most important evaluation parameters. In this paper, different structures have been compared using the "special protection" parameter and the best structure from a protection perspective has been identified and reported.

The production of wood-based materials is currently being expanded by the furniture industry and civil construction sector. In order to find new alternatives for the panel market, new configuration possibilities (geometry) of panels and the use of renewable raw materials must be explored. In this scope, the objective of this research was to evaluate OSB sandwich panels with an undulated core and flat faces (OSBUC panels) made of Balsa wood waste strands (Ochroma pyramidale) bonded with two-component castor oil polyurethane resin for use in civil construction. Two types of panels were produced with 13 % resin and varying the density of the core (OSBUC-T1 - faces 550 kg/m³ and core 400 kg/m³) and (OSBUC-T2 - faces 550 kg/m³ and core 500 kg/m³). The water absorption and thickness swelling of the face panels were determined based on the Brazilian standard NBR 14810 and the bending test properties of the OSBUC panels determined by the recommendations of the ASTM C393 standard. The results obtained were compared with the specifications of the PS-2-10 –“Performance Standard for Wood-Based Structural-Use Panels” that provides bending stiffness (EI) values and maximum bending moment (FbS) requirements for OSB panels according to different classes of use. The sandwich panels had maximum values of EI 6,48 x 106 N·mm²/mm and FbS 3065 N·mm/mm. The OSBUC-T1 treatment proved to be the most efficient, as it has mechanical properties that meet the normative recommendations for structural use and as flooring, with lower material consumption (lower density).

In this paper, the critical buckling temperature of a lattice sandwich panel was investigated using FE analysis. In the previous study[Sebata, Y., Ushijima, K., Study on thermal buckling temperature of a lattice sandwich panel, Transaction of the JSME (in Japanese), Vol. 88, No. 905 (2022)], a Pyramid-shaped core unit was selected and the effects of unit-cell height and width on the buckling temperature were investigated. In the present study, two kinds of lattice core, BCC and f2BCC were added for investigation, and the effects of the core stiffness and micro-architecture on the buckling temperature were discussed. It was revealed from this study that the constraint of rotational angle at the connection point between the face sheet and the core strands could enhance the local buckling temperature. Also, enlarging the core stiffness could enhance the local buckling temperature. Moreover, the local buckling temperature can be predicted theoretically based on the thick shell theory by considering the effective width of the face sheet for one unit-cell reflected by the cross-sectional area for a strut.

Half monocoque structures – space‐forming load‐bearing structures made of sandwich panels In the process of the research project called, "Half Monocoque Structures – Space‐forming and load‐bearing structures made of sandwich panels ", theoretical and experimental investigations were carried out into the load‐bearing behavior of self‐supporting structures made of sandwich panels under axial compressive loading. The aim of the research project was to validate and, if necessary, further develop existing calculation approaches for load‐bearing and serviceability and design detailed solutions for load introduction and distribution areas. A self‐supporting structure made of sandwich panels was first designed as an example object. For this purpose, all necessary design drawings and detailed solutions for the formation of the load application points and impact points were worked out and defined for this application. In addition, an economic and ecological analysis of the construction method was carried out on the basis of the example object. The results gained from the holistic consideration of the construction method is then to serve as the basis for the acquisition of a building authority approval. In this article, the main research results are presented and the advantages of the construction method of self‐supporting sandwich panels structures without a supporting substructure are presented. [ABSTRACT FROM AUTHOR]

In this study, sandwich panels are presented with polylactic acid (PLA) core made through the FDM method. The face sheets of the panels are made out of aluminum 3105 alloy. The mechanical properties of the proposed samples were investigated under flexural quasi-static load. Different panels were tested by a three-point flexural test to determine their collapse properties; moreover, cubic specimens were exposed to quasi-static compression load. The results confirmed the effective role of layering type in the FDM method on the collapse properties of the sandwich panel. Results showed that type of the main pattern extension can affect the collapse properties. A comparison of the cubic samples under three different quasi-static compressive loading indicated that the collapse properties and absorbed energy of the samples depend on the loading direction. The proposed lightweight structures absorb high energy in comparison with ordinary one which was investigated in this paper; thus they can be an ideal structure for industries. Numerical modeling was another part of the study which was done by LS-DYNA and good agreement between numerical and experimental results was observed. [ABSTRACT FROM AUTHOR]

Extensive research is conducted on enhancing the blast mitigation performance of the sandwich panels by examining different design parameters, and core geometries. Nevertheless, there is no direct comparison between those alternatives to evaluate their contribution to maximizing energy absorption. In this research, three core designs honeycomb, mushroom, and tubular were compared to determine the influence of core shape on the panel's impact resistance against blast load. In addition to varying core shapes, the effect of plate thickness and the spacing between the core shapes are also examined. Finite element analysis was used to evaluate the performance of these designs. Twenty-seven numerical experiments were performed and then analyzed using regression analysis. Results reveal that the tubular sandwich panel exhibited minimum deformation, and least damage and contributed to the highest kinetic energy dissipation. On the other hand, honeycomb core structures recorded the highest internal energy dissipation, largest deformation, and damage. Despite those differences, core shape and core spacing were not as influential in resisting blast load compared to plate thickness. Facade plate thickness was the most significant factor. Results suggest that more research needs to be targeted toward enhancing façade plate stiffness for better mitigation of blast load. [ABSTRACT FROM AUTHOR]

The production of wood-based materials is currently being expanded by the furniture industry and civil construction sector. In order to find new alternatives for the panel market, new configuration possibilities (geometry) of panels and the use of renewable raw materials must be explored. In this scope, the objective of this research was to evaluate OSB sandwich panels with an undulated core and flat faces (OSBUC panels) made of Balsa wood waste strands (Ochroma pyramidale) bonded with two-component castor oil polyurethane resin for use in civil construction. Two types of panels were produced with 13 % resin and varying the density of the core (OSBUC-T1 - faces 550 kg/m2 and core 400 kg/m2) and (OSBUC-T2 - faces 550 kg/m2 and core 500 kg/m2). The water absorption and thickness swelling of the face panels were determined based on the Brazilian standard NBR 14810 and the bending test properties of the OSBUC panels determined by the recommendations of the ASTM C393 standard. The results obtained were compared with the specifications of the PS-2-10 - "Performance Standard for Wood-Based Structural-Use Panels" that provides bending stiffness (EI) values and maximum bending moment (FbS) requirements for OSB panels according to different classes of use. The sandwich panels had maximum values of EI 6,48 x 106 N·mm²/mm and FbS 3065 N·mm/mm. The OSBUC-T1 treatment proved to be the most efficient, as it has mechanical properties that meet the normative recommendations for structural use and as flooring, with lower material consumption (lower density). [ABSTRACT FROM AUTHOR]

Sandwich panels (SP) are very promising components for structures as they ally high levels of specific stiffness and strength. Civil, marine and automotive industries are some examples of the sectors that use SPs frequently. This work demonstrates the potential of manufacturing Z-pin-reinforced foam core SPs, using a design strategy that indicated optimal values for both pin position and angle, keeping the same pin diameter as determined in a previous study. A simple search algorithm was applied to optimize each design, ensuring maximum flexural stiffness. Designs using optimal pin position, optimal pin angle and optimal values for both parameters are herein investigated using numerical and experimental approaches. The optimal pin position yielded an increase in flexural stiffness of around 8.0% when compared to the non-optimized design. In this same comparison, the optimal pin angle by itself increased the flexural stiffness by about 63.0%. Besides, the highest increase in the maximum load was found for those composites, molded with optimized levels of pin position and pin angle, which synergistically contributed to this result. All results were demonstrated with numerical and experimental results and there was a good agreement between them. [ABSTRACT FROM AUTHOR]

Biobased products promote efficient industrial use of natural resources, directly contributing to circular economy principles and sustainable development. This work investigates biocomposites made from Hay Tifton 85 grass fibers (i.e., Cynodon spp.) combined with castor oil polyurethane or epoxy matrices and their evaluation as core materials for novel fiber metal laminates (FMLs). A full factorial design is used to identify the effects of polymer type and fiber length on the tensile, flexural, compression and impact properties of composites. A cold pressing technique is used to manufacture random‐fiber composites and FMLs made of aluminum skins. The castor oil matrix shows promise for dynamic applications, while the epoxy matrix provides better performance under static loads. Composites achieved improved mechanical properties attributed to their lower porosity. The mechanical properties of FMLs under tensile flexural and impact (Charpy and drop tower) are also considerably higher than those of fiber‐reinforced polymers. Fully biobased laminates offer potential advantages compared to epoxy polymer composites. Their use as cores in FMLs can be extended to applications related to the automotive, civil construction and aeronautical sectors, fostering sustainable industrial designs. [ABSTRACT FROM AUTHOR]

The research and development of novel protective structures with excellent mechanical load-bearing and energy-absorbing characteristics are one of the current interests in aerospace, marine, and automobile industries. In this research, we fabricate foam-filled multi-layered hybrid composite graded lattice sandwich panels (MHCGLSPs) with different configurations and investigate their dynamic response characteristics experimentally and numerically. The influences of strain rate, relative density, filled foam, and graded arrangement on the crushing behavior of the present panels are depicted, and three main failure modes including core buckling (CB), facesheet breakage (FB), and polyurethane foam breakage (PB) are revealed. Furthermore, the numerical results obtained by finite element models based on the Hashin failure criterion and Johnson–Cook model are in good agreement with the experimental results. It is shown that all the present MHCGLSPs possess excellent energy absorption performance, and the non-graded specimens and gradually weaker specimens possess better ultimate load-bearing capacity under the premise of equal relative density, which can provide guideline for further studies on the novel multi-layered protective structures. [ABSTRACT FROM AUTHOR]

An efficient finite element model based on conventional shell elements available in ABAQUS software has been developed for free vibration analysis of FGM monolayer and sandwich flat panels. Applications to sandwich plates with an FGM layer embedded as either a core or face sheets with different through-the-thickness material gradations in the form of power (P-FGM), sigmoid (S-FGM), and exponential (E-FGM) distributions are considered. A user-defined material subroutine UMAT was used to implement functionally graded properties of the constitutive FGM layer. Numerical studies are given for free vibrations of monolayer and sandwich plates subjected to various boundary conditions and with different structural parameters such as span-to-thickness, face sheet-core-face sheet thickness and aspect ratios, and volume fraction index. The studies showed very good agreement between the present results and those existing in the literature that confirmed the accuracy of the developed model at minimal computational costs. This emphasizes the efficiency of the shell-based modeling strategy proposed for the calculations. A series of numerical solutions obtained in the research extends the results of known testing examples and may serve as additional benchmark data for other analysts. [ABSTRACT FROM AUTHOR]

This investigation aims to assess the mechanical behavior and energy absorption properties of the light sandwich panels made of open‐cell polymer and nickel/polymer foam. A portion of the ultralightweight foam sandwich panels (14.23 g) is produced by 3D printing and electrodeposition methods with 35, 45, and 55 seeds numbers, which lead to 4, 5, and 6 pores per inch (PPI); then a uniaxial compression test is applied to measure maximum compressive strength, strength‐to‐weight ratio, energy absorption density, efficiency, and complementary energy. The results indicate that compared with typical open‐cell nickel foams and polymer precursors when the thickness of the nickel layer is about 50 micrometers, the aforementioned properties of the sandwich panel shows a significant improvement. Improvement of properties changes by increasing PPI and CAD seed numbers. In a nickel/polymer sandwich panel with 6 PPI, the first maximum compressive strength, specific energy absorption, and energy absorption efficiency reach 0.93 (MPa), 0.93 (J.g−1), and 60%, respectively. 3D‐RP‐Ni‐6 improves 3D‐RP‐6 first maximum compressive strength and specific energy absorption by six times and two times, respectively. These significant improvements in the properties of these sandwich panels make these advanced materials a suitable candidate for the high strength applications. [ABSTRACT FROM AUTHOR]

Nowadays grid structures are considered as one of the most useful composites because of their various applications. Since grid structures are vulnerable to impact loads, they should be investigated under such loadings. The present paper studies the low-velocity impact loading of sandwich panels with grid-stiffened cores using both experimental and numerical simulations. In addition to the impact behaviour and the resultant damage of the sandwich panels, the behaviour of these structures under three-point bending was studied before and after the impact loading. The results were provided for impact and bending loadings separately. Then the effect of impact loadings on bending strength was investigated and it was found that the impact loading decreases the bending strength. A consistency between numerical and experimental results was also observed, which confirms the applicability of the Finite Element Method (FEM) in simulating the behaviour of such structures under impact and bending loads, while saving lots of time, efforts and costs.

This work presents an innovative honeycomb cell geometry design with enhanced in-plane energy absorption under quasi-static lateral loads. Numerical and experimental compression tests results under axial and lateral loads are analyzed. The proposed cell geometry was designed to overcome the limitations posed by standard hexagonal honeycombs, which show relatively low stiffness and energy absorption under loads that have a significant lateral component. To achieve this, the new cell geometry was designed with internal diagonal walls to support the external walls, increasing its stiffness and impact energy absorption in comparison with the hexagonal cell. 3D-printed unit-cell specimens made from ABS thermoplastic material were subjected to experimental quasi-static compression tests, in both lateral and axial directions. Energy absorption was compared to that of the standard hexagonal cell, with the same mass and height. Finite element models were developed and validated using experimental data. Results show that the innovative geometry absorbs approximately 15% more energy under lateral compression, while maintaining the same level of energy absorption of the standard hexagonal cell in the axial direction. The present study demonstrates that the proposed cell geometry has the potential to substitute the standard hexagonal honeycomb in applications where significant lateral loads are present.

Concerning energy improvement of existing façades, a favourable system involves prefabricated multilayer panels, made of internal insulation core and outer textile reinforced concrete layers. It is a convincing alternative to external thermal insulation composite systems (ETICS) and ventilated façades, and it meets all the requirements for façade systems. The main advantage is the possibility to apply the panel using a crane, without any scaffolding. The paper considers two solutions: the former uses expanded polystyrene (EPS) as insulating material; the latter substitutes EPS with an innovative green insulation material made of inorganic diatomite. The paper aims at comparing the solutions in terms of mechanical properties of the components and behaviour of the composite sandwich at lab-scale level. Numerical models, previously calibrated, will be instrumental for the discussion.

• An integrated 3D printing of fiber-reinforced sandwich panels is proposed. • The epoxy resin pre-impregnated fibers are employed to print overhanging structure. • The integrated 3D printed sandwich panels excel in lightweight properties. • The Schwarz Primitive core structure has the maximum energy absorption. • FE model is developed to analyze the damage mechanism of printed samples. Sandwich panel structures have widespread applications in various components, owing to their excellent lightweight properties. However, conventional manufacturing methods involve multiple steps, which limits the exploration of innovative sandwich panel structure. In this study, an integrated 3D printing method for continuous fibers reinforced sandwich panel with Triply Periodic Minimal Surface (TPMS) core structure is proposed via Fused Deposition Modelling (FDM). A bridging layer and a continuous basalt fiber pre-impregnated by stiff thermoset epoxy resin are utilized to address the issue of overhanging printing for the upper face sheet. Two kinds of TPMS are employed as the core, as well as two kinds of honeycomb. Multi-step printed samples using a bonding process and counterpart samples without fiber were prepared for the comparison. 3-point bending tests were conducted and a finite element model which can represent the structure characteristic is proposed to investigate the mechanical properties. The results show that the integrated printed sample exhibits better performance in terms of printing quality, flexural modulus, strength and energy absorption (EA) compared with the multi-step printed sample. It has an excellent ability to avoid the catastrophic damage which is usually encountered in the multi-step printed sample due to the introduction of brittle epoxy resin, showing a notable 162.88 % augmentation in specific energy absorption (SEA). The significant improvement lies in that it uses the reinforcement of fiber and the energy absorption capacity of core to full advantage via the strong binding. In addition, as one kind of TPMS, Schwarz Primary structure exhibits the maximum flexural modulus, strength and energy absorption among the four cores. The proposed design and fabrication methodology pave the way for the creation of high-performance sandwich panels with different core structures. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigates the potential of developing corrugated panels from tea oil camellia shell (TOCS), an abundant agricultural waste in the southern provinces of China, with an annual production of approximately 4 million tons, using experimental and computational methods. Hence, various corrugated geometries were designed using AutoCAD software, and finite element analysis (FEA) was conducted using Ansys Mechanical software to optimize the panel geometry based on TOCS engineering data. Bending performance simulations revealed that a trapezoidal geometry with a 3 mm edge radius exhibited superior bending performance. Therefore, this geometry was selected to fabricate corrugated panels of different densities to assess the impact of density variation. Mechanical characterization included evaluation of bending stiffness, maximum moment, total deflection, compression strength, ultimate strength, dowel bearing strength, and face screw resistance of the panels was performed. Furthermore, specific energy absorption and failure mechanisms of mechanical tests were analyzed. The results indicate that TOCS-based sandwich panels, characterized by their lightweight and sustainable nature, not only meet, or exceed the criteria specified in APA PS 2–10 for use as structural materials but also mitigate the environmental hazards associated with landfill disposal or burning of agricultural waste. • Developing a light-weight and eco-friendly sandwich panel based on agricultural waste. • Increased surface layer density enhances mechanical properties, meeting ANSI A208. • Density variations enhance energy absorption and failure resistance. • Trapezoidal geometry is optimized for superior load-bearing and stress distribution. [ABSTRACT FROM AUTHOR]

The research presented in this paper is about the mechanical properties of fiber-reinforced alkali-activated slag cementitious sandwich panels with different types and amounts of admixtures. The mechanical properties, drying shrinkage properties, and micro-morphology were used to determine the optimal ratio of the admixtures. The results show that the alkali-activated slag sandwich panels have the characteristics of light weight, high strength and excellent thermal insulation, and the factors such as magnesium oxide, expansion agent and solution temperature have significant influence on their mechanical properties and dry shrinkage. This paper provides a theoretical basis and experimental data for the preparation process and application of alkali-activated slag sandwich panels.