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Honeycombs are commonly used as core materials in sandwich panels, and the core geometry significantly impacts the bending behaviour of these structures. Understanding how core characteristics influence the mechanical properties of sandwich panels is essential. The comparison between different honeycomb sandwich panel configurations is quite complex. This study delves into the intricate comparison between various honeycomb sandwich panel configurations, serving as a benchmark for integral 3D printed panels featuring hexagonal cores in both L- and W-directions, and circular cores. Notably, wrinkling phenomena are observed in the L-direction of the hexagonal cores. Circular cell panels exhibit increased load capacity, flexural modulus, and toughness. Additionally, hexagonal L-core panels demonstrate a higher toughness modulus than their W-core counterparts, making them less rigid yet stronger. Furthermore, L-cell core panels possess a lower density than circular cores, whereas W-cell cores exhibit higher density, compromising their specific mechanical properties. [ABSTRACT FROM AUTHOR]

AbstractThe in-plane auxetic honeycomb sandwich panels (AHSPs) with polyurea-metal laminate (PML) as faceplates were proposed, and their vibration and acoustic properties were investigated. The natural frequency, damping loss factor, sound transmission loss (STL), and sound field pressure distribution were simulated by the finite element, which was then compared with the AHSP without a polyurea layer. The sound insulation properties of the AHSPs with PML faceplates were significantly enhanced due to the viscoelastic energy consumption of the polyurea layer. By changing the thickness of the polyurea layer and adopting different honeycomb geometries, the sound insulation ability of the sandwich plate could be further enhanced. The average STL rose by 2.3–4.7 dB when the polyurea layer thickness was increased, hence significantly improving the noise suppression ability of the AHSPs. When the geometric tilt angle θ of the honeycomb core is −45°, the sandwich panel exhibits superior sound insulation performance. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) offers new possibilities to fabricate and design lightweight lattice materials. Due to the superior mechanical properties of these lattice structures, they have the potential to replace honeycombs as cores in sandwich panels. In addition to the advantage of the integral fabrication thanks to AM, additively manufactured lattice core sandwich panels may be also used as heat exchangers, enabling a multifunctional use of the core. To ensure a reliable and safe structure, the mechanical response of lattice core sandwich panels under given load conditions must be predictable. In conventional sandwich panels subjected to compressive loads, the sandwich's global buckling and the face sheets' local buckling are the dominant failure modes. In constrast, core strut buckling may be the critical failure mode in lattice core sandwich panels. Therefore, an analytical 2D model to predict the local buckling of lattice core struts is considered in this study. Furthermore, the critical load for global buckling is obtained based on the first-order shear deformation theory. Thus, the transition from local buckling to global buckling depending on the length-to-thickness ratio is captured by the presented model. The comparison with finite element modeling of the sandwich model with truss cores has proved the accuracy of the derived model. [ABSTRACT FROM AUTHOR]

Material-extrusion-based 3D printing with polylactic acid (PLA) has transformed the production of lightweight lattice structures with a high strength-to-weight ratio for various industries. While PLA offers advantages such as eco-friendliness, affordability, and printability, its mechanical properties degrade due to environmental factors. This study investigated the impact resistance of PLA lattice structures subjected to material degradation under room temperature, humidity, and natural light exposure. Four lattice core types (auxetic, negative-to-positive (NTP) gradient in terms of Poisson's ratio, positive-to-negative (PTN) gradient in terms of Poisson's ratio, and honeycomb) were analyzed for variations in mechanical properties due to declines in yield stress and failure strain. Mechanical testing and numerical simulations at various yield stress and failure strain levels evaluated the degradation effect, using undegraded material as a reference. The results showed that structures with a negative Poisson's ratio exhibited superior resistance to local crushing despite material weakening. Reducing the material's brittleness (failure strain) had a greater impact on impact response compared to reducing its yield stress. This study also revealed the potential of gradient cores, which exhibited a balance between strength (maintaining similar peak force to auxetic cores around 800 N) and energy absorption (up to 40% higher than auxetic cores) under moderate degradation (yield strength and failure strain at 60% and 80% of reference values). These findings suggest that gradient structures with varying Poisson's ratios employing auxetic designs are valuable choices for AM parts requiring both strength and resilience in variable environmental conditions. [ABSTRACT FROM AUTHOR]

This study investigates lightweight and efficient candidates for sound absorption to address the growing demand for sustainable and eco-friendly materials in noise attenuation. Juncus effusus (JE) is a natural fiber known for its unique three-dimensional network, providing a viable and sustainable filler for enhanced sound absorption in honeycomb panels. Microperforated-panel (MPP) honeycomb absorbers incorporating JE fillers were fabricated and designed, focusing on optimizing the absorber designs by varying JE filler densities, geometrical arrangements, and MPP parameters. At optimal filling densities, the MPP-type honeycomb structures filled with JE fibers achieved high noise reduction coefficients (NRC) of 0.5 and 0.7 at 20 mm and 50 mm thicknesses, respectively. Using an analytical model and an artificial neural network (ANN) model, the sound absorption characteristics of these absorbers were successfully predicted. This study demonstrates the potential of JE fibers in improving noise mitigation strategies across different industries, offering more sustainable and efficient solutions for construction and transportation. [ABSTRACT FROM AUTHOR]

Highlights Novel Stitched Foam‐filled Honeycomb Sandwich (SFHS) panels have been fabricated using vacuum‐assisted resin transfer molding to address the weak interfaces between the face sheets and the core in the Foam‐filled Honeycomb Sandwich (FHS) panel. The SFHS panels have shown better load‐bearing capacity and performance characteristics compared to FHS panel after Low‐Velocity Impact (LVI) tests. After the LVI test, MATLAB image processing was used to analyze the impact damage areas and failure mechanisms. In addition, Machine Learning regression algorithms were employed to predict the optimal amount of energy absorbed during low‐velocity impact testing of fabricated panels with a maximum impactor drop height of 700 mm. The results indicated that nylon yarn stitching significantly improved energy absorption and interfacial behavior compared to unstitched honeycomb panels. This research also revealed that SFHS1 panels with adjacent honeycomb cell stitching are more impact resistant, provide increased load carrying capacity, and are cost‐effective. These panels can be utilized by modern engineers to increase economy, durability, and functionality in industrial, automotive, and construction applications. Stitched Foam Filled Honeycomb Sandwich (SFHS) panels, manufactured via resin transfer molding, and eliminates weak interfaces between the face sheets and core. SFHS panels outperformed unstitched panels in load‐bearing and energy absorption during low‐velocity impact, as confirmed by MATLAB image analysis showing reduced damage and failure. Machine learning algorithms particularly polynomial regression model predicted maximum absorption energy precisely with 99.9% accuracy, close to experimental results. SFHS panels can be used in automotive and industrial applications due to their through‐thickness stitching. [ABSTRACT FROM AUTHOR]

Composite sandwich structures are widely used for their mechanical properties combined to lightweight. However, damage area quantification caused by low velocity impacts represents generally a crucial task in sandwich composites. In the last years, recent advantages of thermographic devices offer new promising and different real-time industrial and engineering applications where lower computation time, accuracy of results and convenient cost are required. The present research deals with the comparison of standard or latest image-processing methods proposed for pulsed thermography regarding their suitability for determining the impact damage area in sandwich materials made of Aluminium core an a GFRP laminated skins. The Infra-Red processed results are compared with the advanced ultrasonic Phased array method commonly employed in the industrial Non-Destructive Testing. Specifically, the damage area quantification is performed by means of an appropriate MATLAB binarization algorithm for the post-processing of acquired thermal and ultrasonic maps. The data results verify the effectiveness of the image-processing thermographic technique combined to advanced processing approaches for the quantitative assessment of impact damage in sandwich component. [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. [ABSTRACT FROM AUTHOR]

This paper presents an analysis for the dynamic stability of sandwich beams/wide plates subjected to periodic axial loads. The formulation of the problem is done by use of the Extended High-order Sandwich Panel Theory (EHSAPT). The equations of motion are derived from Hamilton's principle and are expressed in terms of seven generalized displacements. A sandwich panel with simply supported edges is studied as an example, and the equations of motion for a given harmonic n are further derived. Two time-variations for the axial forces, namely, harmonic axial forces and step-wise periodic axial forces, are considered in this work. By considering the features of these two periodic load profiles, Floquet theory and Bolotin's method are adopted to perform the dynamic stability analysis. Sandwich panels with different face-to-core thickness ratios are studied. Stability maps for varying frequency and amplitude of the forces are presented. Numerical examples show that when a sandwich panel is subjected to periodic loads, it is possible that it can experience dynamic instability even when the dynamic loads are much lower than the static critical loads. [ABSTRACT FROM AUTHOR]

This research study the energy absorption performance of aluminum core honeycomb sandwich panel (ACHSP) with filled and empty cores subjected to low-velocity impact testing, with diverse skins; (i) aluminum sheets, (ii) 5-ply epoxy glass composite, and (iii) 5-ply shear thickening fluid (STF)-impregnated glass fabrics. The prepared STF was 35 wt% and the impactor heights was selected at 100 and 500 mm to assess the effect of different impact velocities on the energy absorption capability of STF. The specific energy absorption (SEA) of the STF-filled ACHSP with 5-ply STF-impregnated fabrics skin (height of 500 mm) compared to STF-filled ACHSP with aluminum sheets skin and 5-ply epoxy glass composite skin have increased by 28.38 and 21.79%, respectively. In a fact of truth, when the external force is applied to the STF-filled ACHSP, the fluid transitions from a low-velocity to a high-velocity state instantly. This transition exerts forces on the suspended particles within the fluid. Actually, during the impact, the particles come into close contact and form temporary particle networks or chains. These networks increase the viscosity of the fluid, making it resistant to flow. The energy of the impact is then absorbed by the formation and reformation of these particles' networks. However, the SEA of STF-filled ACHSP at the height of 500 mm to empty ACHSP at the height of 100 mm have decreased significantly, and the energy absorption of STF-filled ACHSPs to corresponding empty ACHSPs have increased remarkably. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Honeycomb panels manufactured from wood and paper materials promote a high-value utilization of wood resources. However, the poor mechanical properties and uncommon thicknesses (32 and 40 mm) of paper honeycomb panels limit their application and promotion in the panel furniture industry. Hence, numerous attempts have been made to develop high-strength and low-density wood sandwich composites for the frames and partitions of cabinet furniture. This paper describes a method for manufacturing lightweight sandwich panels (18 mm thickness) with auxetic cores, made of fast-growing poplar. The mechanical properties of the panels and the negative Poisson's ratio of the perforated sheet cores were determined by three-point bending and uniaxial compression tests. The lower density, higher modulus of elasticity, and bending strength suggest that the developed panel is a good substitute for traditional wood-based panels. A numerical model for panels in bending tests is proposed and validated against the experimental analysis results. These investigations facilitate further research into optimizing the sandwich panel structure and its applicability in the architectural and furniture industry. Graphical Abstract [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

On the flexural buckling of sandwich panels Sandwich panels are one of the leading systems for building envelopes in industrial and commercial construction. Other areas of applications are cold storage rooms, which are realized exclusively from sandwich panels without any substructure or primary structure. Thereby, the sandwich panels, which are used as wall panels, are subjected to axial loads. A design concept of sandwich panels under axial loading based on stress verifications can be found in the draft of the new Eurocode 3 standard EN 1993‐7 "Design of steel structures – sandwich panels". A design concept based on the geometrical and structural imperfections and the actual load‐bearing capacity of the panels is neither included in the literature nor in the draft of the new standard. In the present work, investigations on flexural buckling of sandwich panels are presented. A method is presented which can be used in the future for the development of buckling curves of sandwich panels. [ABSTRACT FROM AUTHOR]

Tests on sandwich façades as a basis for seismic design As part of an ongoing research project, the performance of lightweight metal façade elements under in‐plane loading was investigated to assess their cyclic behavior, dissipation capacity and functionality during seismic events. As preliminary investigations showed, metal wall and roof elements contribute to the stiffening of the overall structure, and thus to the change of the eigen period compared to the primary structure, which can lead to increased seismic loads to be applied acc. to the response spectrum method. Based on this, a new behavior‐based approach considering the contribution of lightweight metal building envelopes can be developed to determine the improved resilience of structures and the effect of a damaging earthquake on the building envelope performance. This paper includes: (i) a brief state of the art, (ii) a presentation of the research project, (iii) the experimental program, (iv) the detailed experimental setup, (v) the system response under monotonic and cyclic loading, (vi) the main results, (vii) an overview of the numerical investigations and ongoing and future research activities. [ABSTRACT FROM AUTHOR]

Cold stores with sandwich panels Cold stores are indoor constructions, which are indispensable for the storage of foods. The rising demand for larger storage‐spaces in the distribution centers of the food‐retailers lead to steel‐lightweight cold stores with dimensions of L × W × H = 50 m × 20 m × 16 m, which require a proper structural design. Because of their excellent insulating properties, mainly sandwich panels are used for the construction of cold stores. The detailed designs are demanding, as they require comprehensive thermal and executional optimization. Hence, they often need to be considered in the design and calculation process. The ceiling and wall panels may be considered as diaphragms for the spatial stiffening if the corresponding design and execution rules are respected. If in addition, the wall elements, transferring the ceiling loads, are designed regarding the additional stresses due to second order theory, cold rooms made of sandwich panels, may be carried out without any substructure. The draft of the new standard – prEN 1993‐7 "Design of steel structures – sandwich panels" – provides a corresponding design method. Proven execution details and calculation examples for panels as diaphragms and compression supports are explained below. [ABSTRACT FROM AUTHOR]

Lightweight building steel envelop systems with bio‐based insulation – conservation of resources and reduction of CO2 emissions The aim of the research project presented below is to develop five building envelope systems made of low‐carbon steel and innovative use of wood fibre insulation. Three sandwich panels (pitched roof, flat roof, façade), a double‐skin façade and a façade cladding (cassettes) will be developed. The project includes a series of tests to investigate all relevant properties of the systems: load‐bearing behavior, fire behavior, thermal insulation, acoustics, air‐, water‐ and vapor‐permeability. In addition, two full‐scale prototypes were built to study the behavior of the systems under real conditions. The determination of LCA indicators and a comparison in terms of carbon footprint (GWP) with conventional systems using an existing office building as a reference will also be carried out. An economic comparison between the expected delivery and installation price of the five innovative systems and that of the existing conventional systems is planned. The production of the sandwich panels can be easily integrated into the current production lines. [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. [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]

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]

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]

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]

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]

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]

Determination of the shear properties of sandwich core materials A comparison of the core materials of sandwich panels has revealed inconsistent relationships between their stiffness moduli at different core thicknesses. Therefore, two test methods for determining the shear properties of the core material of sandwich panels were assessed theoretically and experimentally. The results show that for the shear beam test according to EN 14509 a more precise definition of the load distribution plates is necessary and that the usual neglect of the indentation at the support is only justified for thin and medium panel thicknesses. The investigations on the square shear test have shown the influence of the eccentricity between the joint plane and the top edge of the specimen and resulted in the development of a new test setup. The findings from the investigations provide the basis for more realistic modelling of the load‐bearing behavior of sandwich panels in the future. [ABSTRACT FROM AUTHOR]

The problem of local instability in the compressed facing of a sandwich panel is considered in the paper. The case of a facing resting on an infinite core is examined, but the validity of such a simplification has been discussed in detail. An energy approach is used to solve the problem. The general procedure for considering the influence of the core parameter variability on the value of stress causing the facing instability is presented. Expressions allowing us to calculate the wrinkling stress were derived, which was the main aim of the research. The heterogeneity of the core material is taken into account by using continuous functions describing the variability of the core material parameters. In the examples illustrating the theory, the exponential and polynomial functions were used. The examples are based on the actually measured elastic modules of the core. The presented considerations were extended to the analysis of strain energies, which confirmed that the properties of the layer adjacent to the facing (up to 2 cm thick) determine the value of the wrinkling stress. The paper presents an example of the optimization of core material parameters in which a change in the distribution of the core parameters led to an approximately threefold increase in the wrinkling strength of the sandwich panel. [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. Wpracy przedstawiono wyniki badan eksperymentalnych układów konstrukcyjnych składajacych sie z płyt warstwowych i belek cienkosciennych o przekroju Z ułozonych niesymetrycznie wzgledem siebie. W oparciu o europejskie rekomendacje oraz wczesniejsze badania autorów zakłada sie, ze w analizowanym układzie belki sa stabilizowane bocznie przez płyty warstwowe. Wykonano 11 badan laboratoryjnych, które rózniły sie miedzy soba liczba łaczników oraz sposobem przyłozenia obciazenia. W celu połaczenia płyt warstwowych z belka cienkoscienna uzyto 0, 4 lub 8 łaczników. Obciazenie przypadajace na układ było przyłozone równolegle do belek cienkosciennych powodujac obciazenie równomiernie rozłozone a prostopadle do belek cienkosciennych powodujac obciazenie punktowe. Przeprowadzone badania wykazały znaczaca wrazliwosc układu na sposób przyłozenia obciazenia wzgledem analizowanych układów konstrukcyjnych. Wykazano, ze obciazenie realizowane jako równoległe do długosci belki podpierajacej płyte pozwala analizowanemu układowi na przeniesienie ponad dwukrotnie wiekszego obciazenia niz w przypadku obciazenia realizowanego w sposób prostopadły do długosci belki. Dodatkowo omówiono w pracy mechanizmy zniszczenia układu w zaleznosci od sposobu jego obciazenia. Zbadano równiez wpływ liczby łaczników na całkowita nosnosc analizowanego układu. Wykazano znaczacy wzrost nosnosci układu przy zwiekszajacej sie liczbie łaczników. Zwiekszenie liczby łaczników łaczacych belki cienkoscienne z płytami warstwowymi wiazało sie równiez z powstaniem złozonym mechanizmami zniszczenia układu. Uzupełnieniem przeprowadzonych badan eksperymentalnych było wykonanie symulacji numerycznych belek cienkosciennych niestezonych poszyciem. Belki zamodelowane zostały jako elementy powłokowe obciazone na dwa sposoby: obciazeniem równomiernie rozłozonym na pasie górnym belki oraz siła skupiona w srodku rozpietosci belki. Otrzymane wyniki oraz mechanizmy zniszczenia porównano z wynikami laboratoryjnymi belki stezonej płyta warstwowa. Wykazano, ze belka niestezona płyta warstwowa wykazuje prawie dwukrotnie nizsza nosnosc niz belka stezona. [ABSTRACT FROM AUTHOR]

Rainwater may penetrate through the cladding, enter the wall assembly, and cause damage to the façade components and interior finishes, which are moisture sensitive, most of the time. In the current paper, the performance assessment of a skylight with a full-scale mock-up has been evaluated. The mock-up was erected for an actual project to verify the acceptance criteria for the skylight's technical, functional, and architectural details. The test was conducted at the Aluminum Technology Auxiliary Ind. (ALUTEC) facility in the Industrial Zone, Doha, Qatar. The fabricated full-scale mock-up has a rectangular plane configuration of 6.625 m (length) by 3.315 m (width) that belongs to a skylight measuring 36 m by 18 m. The ASTM E283, ASTM E331, and ASTM E330 standards were followed during the experiment. Air infiltration/exfiltration, static water penetration, structural performance, post-structural static water penetration, and structural proof loading tests were performed in an airtight chamber. After recording the residual displacements, the test findings for all the make-up components, namely steel tubes, glass, and aluminum sandwich panels, were determined and found within acceptable limits. [ABSTRACT FROM AUTHOR]

Textile reinforced concrete (TRC) is a combination of a cementitious matrix and a textile reinforcement that has good mechanical properties. This makes a highly promising composite material for a wide range of construction practices. One notable application of this innovative composite deals with the production of thin sandwich panels. Hence it is noteworthy to examine the control parameters (depth & number of layers) that affect the mechanical properties of TRC sandwich panels with chosen fibre meshes and core material.Initially, 24 different TRC panels were cast and modelled with varying depths (45 mm, 55 mm and 65 mm) and layers (3, 4, 5 and 6), incorporating two different fibre mesh reinforcements. The flexural behavior of these panels was studied both experimentally and numerically using ABAQUS software. The optimized control parameters was obtained from the results was TRC panel of 5 layers of Aramid fibre mesh having 55 mm depth.Further exploration focused on the effect of overall depth variation on the flexural behavior of TRC sandwich panels. A panel with Aramid fibre reinforcement and a calcium silicate board core, featuring a 55 mm overall depth, exhibited a remarkable 69.49 % increase in bending stress compared to a panel with a depth of 118 mm. These findings underscore the significance of optimized control parameters, showcasing the potential for enhancing the mechanical performance of TRC sandwich panels in construction practices. [Display omitted] • The flexural behavior of TRC sandwich panels with aramid fibre mesh as a reinforcement and calcium silicate board as a core was investigated both experimentally and numerically. • The impact of the type of fibre meshes, number of layers and depth (control parameters) on TRC sandwich panels was analyzed. • Optimized control parameters were identified, with a TRC panel consisting of 5 layers of Aramid fibre mesh and a depth of 55 mm showing superior performance. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and analytical study about the sound insulation of innovative sandwich panels - named EasyFloor – for the rehabilitation of degraded timber floors in old buildings. Two types of panels were developed: (i) an all-composite sandwich panel, made of glass fibre reinforced polymer (GFRP) face sheets and webs, and polyurethane (PUR) foam; (ii) and a hybrid sandwich panel, where the top face sheet comprises a thin layer of concrete. The study included the comparative analysis of the airborne sound reduction and impact sound pressure level of both types of panels based on experimental tests on full-scale specimens, including a typical floor covering. The acoustic insulation properties determined experimentally were compared with predictions from different analytical models typically applied to sandwich panels, and also with performance requirements defined in building regulation. Among the different analytical models that were assessed, Sharp's model provided the most accurate predictions when considering the natural and dilatation frequencies as the critical frequency. The comparison of the normalized airborne and impact sound indices determined experimentally with requirements set in building regulation shows that the use of GFRP-PUR panels in the rehabilitation of lightweight timber floors and in new construction, where building comfort requirements are stricter, require mitigation measures to improve sound insulation. • Acoustic behaviour of web-core all-composite and hybrid sandwich panels. • Airborne and impact sound insulation tests. • Influence of panel architecture and effects of resilient floor covering. • Assessment of different analytical models for sound reduction prediction. • Comparison with building comfort requirements. [ABSTRACT FROM AUTHOR]

The paper presents failure scenarios for various types of connections between a thin-walled beam and a sandwich panel. In addition to standard connections used in civil engineering applications, that is, self-drilling fasteners for sandwich panels, the study examined the use of bolts, blind rivets, and double-sided acrylic tape applied linearly and pointwise. The connections were subjected to the horizontal load applied with constant eccentricity with respect to the plane of the connection surface. This load arrangement simulates the behaviour of a free flange of the thin-walled beam in bending while lateral-torsional buckling occurs. In this way, the research covers the determination of the lateral stiffness of the thin-walled beam-free flange, while the other flange is connected to the sandwich panel using various connection systems. [ABSTRACT FROM AUTHOR]

The object of this study is to investigate the influence of different fabrics' configurations, of faced polyester-sisal fiber composites, on the mechanical behavior of a vacuum infused polyethylene terephthalate-foam core sandwich panel. Sisal-unidirectional (yarn and combed yarn fabrics) and plain weave fabrics were fabricated and the sandwiches' performances were compared to faced polyester-unidirectional glass fabric. Comparisons about the morphological aspects and relations with mechanical behavior (flatwise and edgewise compression and 3-point bending) were performed. Different face sheets' thickness was used for this purpose, aiming to correlate the results found for those sisal and glass sandwich panels. The main results showed that faced sisal fabrics/polyester present competitive performance and sometimes higher than those glass/polyester, due to differences on failure mechanisms of the panels. [ABSTRACT FROM AUTHOR]

The energy efficiency of buildings drives the replacement of traditional construction materials with lightweight insulating materials. However, energy-efficient but combustible insulation might contribute to the building's fire load. Therefore, it is necessary to analyse the reaction-to-fire properties of various insulating materials to provide a better understanding of designing a fire-safe structure. In this study, reaction-to-fire tests were carried out to assess the fire behaviour of lightweight polystyrene insulating panels commonly employed in high-rise buildings. The flammability characteristics of expanded polystyrene (EPS) and extruded polystyrene (XPS) were determined using a cone calorimeter under two distinct external irradiance regimes, 35 kW/m2 and 50 kW/m2, to approximate small to medium fire exposure situations. To investigate the effect of a fire-rated (FR) foil layer on a sandwich panel, three distinct test configurations were used: (i) sample without FR layer (standard sample), (ii) sample with FR layer (FR foil), and (iii) damaged layer (foil and vent) for EPS. Except for the smoke toxicity index (STI), the overall fire performance of EPS is superior to that of XPS. The findings of this study are useful in analysing fire performance and fire safety design for lightweight insulation panels. [ABSTRACT FROM AUTHOR]

Introduction: Three-layer structures with a polyurethane foam filler are widely used in construction as roofing and wall panels. The purpose of this work is to develop a method for calculating the bending of three-layer plates with a polyurethane foam filler, taking into account the nonlinear creep of the middle layer. The non-linear Maxwell–Gurevich equation is used as the polyurethane foam creep law. Methods: In the article, the system of resolving the equations is obtained, and the solution is carried out numerically by the finite difference method in combination with the Euler method in a MATLAB environment. An analytical solution is also obtained for a plate hinged along the contour. Results: The developed model and calculation algorithms are verified by comparison with the calculation in the ANSYS software package. A comparison with the calculation according to the linear theory is also carried out, and the effects caused by the non-linear creep of polyurethane foam are revealed. Conclusion: It has been established that when nonlinear creep is taken into account, in contrast to the linear law, the stresses in the plate are not constant in time. In the faces, at the initial stage, the stresses increase with a subsequent return to the initial values, and in the filler, on the contrary, the stresses at the initial stage decrease. These results indicate the need to take into account the nonlinear creep of polyurethane foam in the calculation of sandwich panels. [ABSTRACT FROM AUTHOR]

In this study, carbon fiber/thermoplastic (Elium®) honeycombs were manufactured using the resin infusion process in a customized metallic mold. Honeycomb cores, based on different carbon fiber layers, were manufactured to achieve four different fiber weight fraction composites. Two different types of specimens, based on a single honeycomb cell and five honeycomb cells, were prepared and subjected to compression loading. The results of these tests were compared with data from similar honeycomb structures based on carbon fiber–reinforced epoxy composite. It has been shown that the compressive strength and the specific energy absorption capacity of the honeycombs increase rapidly with increasing fiber weight fraction. The specific energy absorption capability of the novel thermoplastic honeycomb structures has been shown to be as high as 50 kJ/kg which compares favorably with other energy-absorbing core materials. The thermoplastic honeycomb specimens exhibited a similar specific energy absorption capability and an improved compressive strength compared to their epoxy counterparts. Furthermore, the CF/thermoplastic honeycombs exhibited enhanced structural stability and displayed a more uniform and progressive core failure mode than the longitudinal splitting observed in the CF/epoxy honeycombs. The honeycomb core that exhibited the best performance was then used to manufacture thermoplastic sandwich specimens based on CF/thermoplastic face sheets. Three point bend tests were conducted to determine the flexural strength of the sandwich samples and to identify the failure modes. Optical micrographs revealed that the flexural damage was primarily due to the core crushing and adhesive failure between the core and the composite skins. [ABSTRACT FROM AUTHOR]

Additive manufacturing such as vat photopolymerization allows to fabricate intricate geometric structures than conventional manufacturing techniques. However, the manufacturing of lightweight sandwich structures with integrated core and facesheet is rarely fabricated using this process. In this study, photoactivatable liquid resin was used to fabricate sandwich structures with various intricate core topologies including the honeycomb, re-entrant honeycomb, diamond, and square by a vat photopolymerization technique. Uniaxial compression tests were performed to investigate the compressive modulus and strength of these lightweight structures. Sandwich cores with the diamond structure exhibited superior compressive and weight-saving properties whereas the re-entrant structures showed high energy absorption capacity. The fractured regions of the cellular cores were visualized by scanning electron microscopy. Elastoplastic finite element analyses showed the stress distribution of the sandwich structures under compressive loading, which are found to be in good agreement with the experimental results. Dynamic mechanical analysis was performed to compare the behavior of these structures under varying temperatures. All the sandwich structures exhibited more stable thermomechanical properties than the solid materials at elevated temperatures. The findings of this study offer insights into the superior structural and thermal properties of sandwich structures printed by a vat photopolymerization technique, which can benefit a wide range of engineering applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• 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 nonlinear stochastic behavior of soft-core sandwich panels and the evolution of uncertainty along the nonlinear path are investigated. The paper focuses on the way the geometrically nonlinear and unstable behavior is affected by uncertainty and considers, for the first time, the evolution of uncertainty along the unstable structural response. The structural modeling relies on the EHSAPT and its integration into the geometrically nonlinear stochastic regime. A tailored nonlinear FE model that is based on a variational formulation and an arc-length solution scheme are developed. The stochastic analysis adopts the Perturbation-based SFEM and its generalization for the evolution of uncertainty along the process axis. A numerical study demonstrates the stochastic methodology and explores the impact of uncertainty on the nonlinear structural behavior. The evolution of the stochastic stress resultants at the displaced end is studied along the two axes of evolution. The differences between the two representations and their physical and engineering significance are highlighted revealing significant changes to the uncertainty evolution pattern with the shift from global buckling to localized wrinkling instabilities. The representation of the stochastic results along the process axis also quantifies the level of uncertainty near critical and singular points where conventional analyses diverge. [ABSTRACT FROM AUTHOR]

• Stressed-skin full scale test on steel monopitch portal frame was conducted. • Comparison of test data provided clear influence of the cladding on the horizontal structure stiffness. • FE numerical model was created, validated based on the test data. • The approach for taking into account the cladding horizontal shear stiffness was derived and compared. This paper presents a study on the influence of sandwich panel roof cladding on the horizontal stiffness of load-bearing steel structures (stressed skin action). A full-scale test was carried out on a steel monopitch portal frame structure made in two stages – without (bare steel structure) and with roof sandwich panel cladding. Data obtained from both stages of the test are presented and are used to demonstrate the significant increase in horizontal stiffness caused by the cladding system. The test data were then used to validate an FE numerical model. A roof cladding made of composite panels is relatively stiff in its own plane. However, the critical detail is the connection of the panels to the sub-structure (e.g. purlins or rafters), i.e. the screw bearing capacity. Even within the serviceability limits, the internal sheet of the composite panel suffers a certain level of permanent bearing damage. Based on the test data, the results of the FE numerical model and the analytical approach for calculating the shear stiffness of the sandwich panels, the approach for taking into account the influence of the cladding on the horizontal stiffness was derived and compared. This approach is believed to be safe and simple for practical use, and it leads to load-bearing structure members with more slender cross-sections. In addition, the data and results that are obtained expand the limited amount of available data related to stressed skin action. [ABSTRACT FROM AUTHOR]

• The novel honeycomb core sandwich structures were fabricated by combinations of solid-state joining and adhesive bonding processes. • The combined friction stir spot welded, with disc inserts and adhesive bonded, demonstrated exceptional peak load-to-weight ratio and fracture energy. • The peak load of the hybrid bonding specimen with disc insert improved by 705 % and 854 % in the peel and shear test compared to the conventional adhesive bonded specimen. • The stiffness and peak load results of FEA of three-point bending were in good agreement with the experimental results for all types of adhesive-bonded specimens. In the present work, the novel sandwich structures with honeycomb core are fabricated by a solid-state joining process — friction stir spot welding (FSSW), without and with disc inserts (abbreviated as FSSW and FSSW_D) and hybrid joints without and with disc inserts (abbreviated as FSSW_AB and FSSW_D_AB). Their mechanical performance was compared with adhesive-bonded (AB) joints through the lap-shear, peel, bend, and scaled-up forming tests. Further, numerical simulations of a few FSSW strategies and AB joints are performed in Abaqus to predict the load-displacement response and Mises stress during bending. Proposing the fabrication stretegies, implementation and testing, along with numerical prediction of behavior of such joints, are the novel contributions. The peel tests showed substantial improvement in load capacity from 232 % to 705 % for FSSW, FSSW_AB, FSSW_D, and FSSW_D_AB joints, compared to AB joints. In the lap-shear tests, all joint types displayed significantly enhanced peak load over AB joints, ranging from 568 % to 1015 %. The hybrid joints, such as FSSW_AB and FSSW_D_AB, consistently outperformed the corresponding spot-welded joints, FSSW and FSSW_D, due to the sharing of load between the AB and metallurgical bonding. The FSSW_D_AB joints demonstrated exceptional peak load-to-weight ratio and fracture energy. The failure modes were consistent, with disc-inserted structures showing failure at the front-side welds for lap-shear and peel tests. During bending, the numerical modelling results were in good agreement up to the peak load. Bending panels made by FSSW_D_AB demonstrated improvement in specific stiffness and peak load by 46 % and 6.12 %, respectively, compared to the AB panel. Lastly, the scaled-up hybrid sandwich panel (FSSW_D_AB) showed significant improvement in deliverables when compared with the AB panel. [ABSTRACT FROM AUTHOR]