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In this paper, a sandwich structure metamaterial was designed, in which the substrate is radio frequency (RF) F4B, and the metal pattern of copper is prepared by the substrate on both sides. Analyzed the transmission of the structure, and the quad-band and reciprocal electromagnetically induced transparency (EIT)-like phenomena of the structure were obtained. The physical mechanism of the EIT-like phenomenon was explained by the electric field distribution. Discussing the size of the structure, the influence of structure parameters on EIT-like phenomena was further illustrated. By comparing the measured results with the calculated results in a microwave anechoic chamber, the results are in good agreement. This structure has potential applications in multi-band filtering, sensing, and other fields. [ABSTRACT FROM AUTHOR]

We investigate the quantum interference of the electron–hole conversions from the two interfaces in a Weyl semimetal (WSM)-based hybrid structure, in which a superconducting WSM is sandwiched in between two normal ones. The quantum interference is characterized by the chirality-anomaly-manipulation (CAM). It is found that only low energy is in favor for s -wave BCS pairing states. The Andreev reflection (AR) chirality blockade can be tuned by the stagger angle α for the relative orientation of paired Weyl points, accompanied by an AR bipolar chirality diode. Thus, a strong CAM is indicated for the electron–hole conversion. However, the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) pairing states have no energy preference, with the weak and strong CAMs being near and far away from the zero energy, respectively. More interestingly, a perfect AR with the normal reflection suppressed thoroughly can be obtained at any α as a result of the FFLO paring with the same chirality. In addition, the conductance or noise power, which incorporates the contributions of the two paired Weyl nodes, not only, in turn, embodies the respective features of their contributions but also can be experimentally measured to discern between the BCS and FFLO paring states. [ABSTRACT FROM AUTHOR]

The article is dedicated to the numerical simulations of thin-layer structures based on CdTe semiconductors, which can be fabricated by using low-cost technologies. Structures Mo/Au/CdS/CdTe/Au, and their modifications, with different thicknesses of the main layers are investigated. The possibility of creating a detector of ionizing radiation based on these structures, which has selective properties with respect to the radiation type, and very low operation voltage, is shown. The detection efficiencies of α -, β -, and γ -radiation in different energy ranges were calculated based on the obtained values of energy losses of ionizing particles, which are proportional to the output signal of the detector. The use of such detectors, together with a solid-state converter made of boron carbide containing either natural boron nat B or boron enriched with the 10 B isotope up to 95 % , for the detection of thermal neutrons was also studied. It was shown that the structures could be used to create α -particle spectrometers, given that the CdTe thickness is tailored to the highest expected α -particle energy. Detectors with thin CdTe (1–5 μ m) can be successfully used in the counting mode. For neutron detection, stacking multiple single structures into sandwich structures was proposed and investigated. In such a configuration, the detector qualities were markedly improved: the efficiency of neutron detection reached ∼ 60 % , while the sensitivity to the background γ - and β -radiation was ∼ 100 times lower than that for neutrons. The very low sensitivity of the simulated neutron detectors to the neutron incidence angle was shown. [ABSTRACT FROM AUTHOR]

This paper elaborates on the wave propagation characteristics of a smart sandwich plate consisting of smart piezo composite layers on a plate's upper and lower borders via an auxetic core. This study's equation of motion was derived using a refined version of the Shear-deformation theory at a higher order, or HSDT. Additionally, detecting the properties of the auxetic core and piezoelectric composite layers employs a micromechanical model. The fundamental equations of the smart sandwich plates were formulated utilizing the Hamiltonian principle and Maxwell's law. Then, the governing equations of a sandwich plate are solved using an exponential form and an analytical method. Furthermore, the phase velocity of the intelligent sandwich plate is provided based on the layer thicknesses of the auxetic core and thicknesses of intelligent piezoelectric composite layers. In addition, each figure calculates and presents the weight of the Winkler–Pasternak coefficient, the viscoelastic substances factor, the source of the outside electricity, and the volume percent of reinforcement in the matrix on the phase velocity. [ABSTRACT FROM AUTHOR]

Hybrid NUS-8/BNs with a sandwich-like structure were synthesized by layered h-BNs and MOF-NUS-8 via assembly. Thanks to the more abundant exposed binding sites and partial ionic bonding properties of BN, the NUS-8/BN exhibits greatly improved H2 adsorption capacity, which is 1.7 times that of h-BN nanosheets. [ABSTRACT FROM AUTHOR]

First-principles calculations were carried out to investigate the stability of two dimensional (2D) MB2 monolayers (TiB2-I, VB2-I, MnB2-I, TiB2-II, ScB2-II, NiB2-II) with an inverse sandwich configuration and their potential as efficient gas sensors to detect toxic gas molecules. We first identified six stable 2D MB2 configurations, based on stability evaluation covering thermodynamical, dynamical, and thermal aspects. To investigate the performance of these novel structures as gas sensors, the adsorption behavior of five toxic gas molecules (CO, NO, NO2, NH3, SO2) on MB2 has been explored, and the charge transfer and magnetic changes of these adsorption systems were analyzed. It is found that five gases are all chemisorbed on 2D MB2. Particularly, when CO is adsorbed on TiB2-II, the magnetism of the system undergoes a significant change from non-magnetism to antiferromagnetism, showing selectivity for CO. Furthermore, the current−voltage characteristics obtained from simulations confirm gas sensing performance. The TiB2-II is expected to be a candidate material for CO gas sensor with short recovery time (7.50 × 10−10 s). Our theoretical study provides new ideas for designing gas sensor nanomaterials with magnetism alteration as the indicator featuring easy measurement and fast response. [ABSTRACT FROM AUTHOR]

This research proposes a novel sustainable composite using basalt (B), hemp (H) and polyurethane rubber (Pu) reinforced in nano clay functionalised epoxy matrix for sacrificial structural applications prone to low‐velocity impact (LVI). To this end, symmetric and asymmetric laminates such as HHHH, BBBB, BHHB, BHPuHB, BBPuHH and BPuBPuHPuH are fabricated using compression molding techniques and subjected to LVI at three different impact energies of 19.66, 39.39, and 59.05 J. The hemp fibers were treated with NaOH solution before fabrication. Material characterization such as X‐ray diffraction, Raman spectroscopy and morphological studies has been carried out. The impact and post‐impact properties of the proposed composites are experimentally evaluated and validated with the finite element (FE) results. The effect on the residual tensile strength degradation of laminates at different interlayers and energy levels is also investigated using the Caprino analytical model. The barely visible impact damages (BVID) are investigated through non‐destructive dye‐penetration tests, which facilitate easy identification of the prominent LVI damages like "Plateau" and "Cliff‐drop" impressions. Based on the impact energy absorption and residual tensile strength, proposed laminates followed BHPuHB > BBBB > BHHB > HHHH. The experimentation suggests that Polyurethane core laminates support maximum impact energy absorption by favoring a structural change in interlayers. Also, the residual tensile strength decreases as impact velocity increases. Highlights: Low‐velocity impact behavior of sustainable composites is experimented.Basalt, hemp and polyurethane rubber are reinforced in nano clay epoxy matrix.A FE framework to validate the experimentation is proposed.Dye penetrant NDT is adopted to investigate the damages.Morphological studies are conducted to understand LVI responses. [ABSTRACT FROM AUTHOR]

This paper presents an analytical approach for buckling and postbuckling analysis for functionally graded graphene‐reinforced composite (FG‐GRC) toroidal shell segments with the trapezoidal or round corrugated core under the axial tension and compression. The considered shells are placed in a thermal environment and surrounded by an elastic foundation. Based on the von Kármán‐Donnell shell theory with geometrical nonlinearities, Stein and McElman approximation, and a homogenization technique for corrugated shells, the basic equations of shells are established. The previous homogenization technique is improved by adding the thermal forces in the internal force expressions. The shell‐foundation interaction is expressed using the model of the Pasternak assumption. The Ritz energy method is used to obtain the pre‐buckling and postbuckling behaviors of the shells, from which the critical buckling tensions and compressions can be investigated. The influences of FG‐GRC face sheets, corrugated core, and foundation on the buckling behavior of sandwich shells can be shown in the numerical analysis. Highlights: Postbuckling of toroidal shell segments with the corrugated core is analyzed.A homogenization technique is improved for the thermal forces in the core.The shells are made of functionally graded graphene‐reinforced composite.The nonlinear Kármán‐Donnell shell theory and Ritz energy method are applied.Special effects of input parameters on the buckling behavior are investigated. [ABSTRACT FROM AUTHOR]

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. Highlights: 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]

Carbon fiber‐reinforced composite materials exhibit excellent mechanical and electromagnetic shielding capabilities. However, they have some drawbacks, such as high cost and significant reflection losses. In order to address these shortcomings, this study set out to design a sandwich‐structured composite material and produce a composite material designed for electromagnetic shielding using Vacuum Assisted Resin Transfer Molding (VARTM) technology. This composite material promotes the "absorption‐reflection‐reabsorption" process of electromagnetic waves, significantly enhancing its shielding effectiveness, achieving up to 59.4 dB of shielding effect in the 8.2–12.4 GHz (X‐band) range. The study also employed carbon nanotubes (CNTs) matrix doping to modify the composite material, significantly reducing reflection losses. When the amount of carbon nanotubes added reaches 0.6 wt%, the overall SE can be increased by 18%. Additionally, the introduction of CNTs significantly improves the flexural strength and tensile strength of the composite material; at a 0.6 wt% CNT content, the average tensile strength increased from 526.4 to 600.9 MPa, indicating good interfacial interactions between CNTs and epoxy resin. This work provides valuable insights for the preparation of high‐performance electromagnetic shielding materials, with profound theoretical and practical significance. Highlights: Observations through SEM and CT scanning techniques reveal that Vacuum Assisted Resin Transfer Molding (VARTM) technology facilitates strong interlayer bonding between carbon fibers, glass fibers, and copper wires, alongside effective epoxy resin adhesion, thus enhancing the mechanical properties.The sandwich structure's impedance mismatch characteristic facilitates an efficient "absorption‐reflection‐reabsorption" process of electromagnetic waves. Additionally, the incorporation of Carbon Nanotubes (CNTs) enhances the absorption mechanism, reducing reflection losses.Incorporating CNTs further boosts both flexural and tensile strengths, attributed to improved interfacial interactions inhibiting crack formation. [ABSTRACT FROM AUTHOR]

This work created a fireproof sandwich structure in which the face sheets were made of expanded vermiculite and expanded perlite‐filled geopolymer composites and embedded basalt fiber mats and the core material was rock wool in designing the lightweight and cost‐effective fire‐resistant structure for steel bridges with excellent retardant and heat‐insulating performance. The effects of adding 5%, 10%, 15%, and 20% expanded vermiculite and expanded perlite to the geopolymer on mechanical properties and the thermal conductivity were investigated to obtain the optimized material mixtures for preparing the face‐sheets material of the sandwich panel. Then, the fireproof sandwich structures were fabricated and exposed to 800°C for 3 h to study the structural integrity, backfire side temperature, and mass loss ratio. The results indicated that adding 10 wt% expanded vermiculite and 10 wt% expanded perlite to the geopolymer achieved the retention of compressive strength of 66.5% after being exposed to 800°C, and the geopolymer mixtures showed a low thermal conductivity of 0.1942 W/(mK). The TOPSIS evaluation analysis reveals that the proposed fireproof sandwich panel had the highest integrated performance considering the structural weight, insulation properties, and cost. The findings of this work may provide some insights into fireproof and insulating applications in bridge engineering. [ABSTRACT FROM AUTHOR]

AbstractThis study introduces a reinforced star-shaped auxetic honeycomb (RSSAH) sandwich beam, enhanced with hollow thin-walled tubes to improve bending resistance and energy absorption performance. The bending performance of the RSSAH is systematically investigated through quasi-static three-point bending tests and finite element numerical simulations. The findings suggest that when subjected to mid-span stress, the RSSAH displays both localized indentation and overall bending deformation, accompanied by notable negative Poisson’s ratio (NPR) impact under bending loads. Parametric studies are undertaken by numerical simulations to investigate the impact of compression position, auxetic angle, and face sheet thickness on the bending mode of the auxetic honeycomb sandwich beam. The analysis shows that the RSSAH can exhibit excellent bending performance and, at one of the compression positions, displays double-plateau stress characteristics. It is also found that altering key geometric parameters, such as the auxetic angle and panel thickness ratio, can greatly improve the bending capabilities of the RSSAH, achieving stable plastic deformation and high energy absorption. Finally, compared to star-triangle honeycomb (STH) sandwich beam, traditional reentrant honeycomb (RH) sandwich beam and star-shaped auxetic honeycomb (SSAH) sandwich beam, the RSSAH demonstrates superior bending performance and energy absorption capacity. This study offers insights and references for the development of innovative reinforced auxetic honeycomb sandwich beams. [ABSTRACT FROM AUTHOR]

ABSTRACT Encouraged by the emerging infrared thermography (IT)–based technique for determining fatigue limit of composite materials, this study introduces a novel approach for the quick fatigue limit determination based on acoustic emission (AE) technology. The AE‐based method expands fatigue testing capabilities beyond the IT‐based methods. Fatigue experiments were conducted for the composite laminates and composite sandwich panels subjected to stepwise increasing cyclic loads. For composite laminate specimens subjected to tension–tension and tension–compression fatigue loads, the fatigue limits obtained by the AE‐based method are in good correlation with those acquired from the IT‐based method as well as the conventional up‐and‐down test procedure. In the tests for out‐of‐plane shearing fatigue limits of composite sandwich panel specimens, where the IT‐based method did not work properly, the AE‐based method performed well and obtained the fatigue limit estimation, which is in line with that derived from the S–N curve data, thereby demonstrating its high adaptability. [ABSTRACT FROM AUTHOR]

Highlights To address the challenges of achieving strong adhesion between aluminum face sheets and composite cores (3D carbon felts) in sandwich structures, this work presents a novel approach that prioritizes safety, environmental sustainability, and ease of processing. The 3D CFs/Epoxy core was modified with Triton X‐100 in amounts from 0 to 10 wt% of the epoxy resin. The aluminum alloy face sheets were anodized at voltages from 0 to 11 V, using a NaCl‐based anodizing process. The technique of anodizing can enhance the bond between the aluminum face sheets and the 3D CFs/epoxy core, resulting in improved mechanical performance of the composite, including flexural and compressive testing, as well as dynamic mechanical analysis. The composite, embedding 3D CFs foam in epoxy resin, has a storage modulus 65.1% higher than pure epoxy at 2070 MPa. In addition, increasing Triton X‐100 content (1–10 wt%) decreases the storage modulus from 1886 to 1314 MPa and the glass transition temperature from 68.3 to 62.8 °C. Additionally, with Triton X‐100 concentrations of 1 to 10 wt%, the flexural modulus of the epoxy reinforced by 3D CFs drops from 3951.8 to 2400 MPa, and the flexural strength decreases by 55.3% from 174 to 112 MPa, indicating reduced structural rigidity. For sandwich composites with anodized aluminum face sheets, a 7 V anodizing voltage boosts the flexural modulus from 17.8 GPa (0 V) to 36.2 GPa. At 7 V, compressive strength and strain rise by 346.9% and 995.5%, respectively. Flexural toughness peaks at 11239 KJ/m3 with 5 wt% Triton X‐100. Developed new sandwich epoxy composites consisting of anodized aluminum sheet treated with NaCl and modified 3D carbon felts epoxy composites using Triton X‐100. Aluminum face sheets underwent an anodization at different voltages (0, 5, 7, 9, and 11 volts), aiming to enhance the bonding between the aluminum sheets and the 3D CFs/epoxy core. Triton X‐100 was utilized to modify the epoxy matrix at various concentrations (0 to 10 wt%) for improving the flexibility of the sandwich core. The sandwich composites incorporating the un‐anodized face sheet have shown flexural modulus of about 17.8 GPa. The modulus achieves its maximum value of 36.2 GPa when anodized at 7 V, indicating a 103% increase. The flexural strength of sandwich composites increases by 13% (272 MPa) when the Triton X‐100 concentration is raised to 5 wt%, compared to the 240 MPa flexural strength of the Al face sheet anodized at 7 V. [ABSTRACT FROM AUTHOR]

This study investigates free vibration analysis of a microplate featuring a honeycomb (HC) core and incorporates two nanocomposite piezoelectric (NP) layers. Carbon nanotubes (CNTs) are hired to enhance the electro-mechanical performance of the piezoelectric patches, which are subjected to an externally applied electric voltage. All layers are tightly bonded together and are supported by an elastic substrate according to the Pasternak model, capable of withstanding both normal and shear loads. To establish the kinematic relations, a trigonometric plate theory is employed. The governing equations of motion are deduced through the application of Hamilton's principle and variational technique. The modified strain gradient theory, which includes three material length-scale parameters (MLSPs), is used to account for the scale effect. An analytical approach based on Fourier series functions is employed to solve the differential equations of motion. Subsequently, the impact of various factors, such as the geometrical characteristics of the HC core, distribution patterns of CNTs, and other significant parameters, on the normalized frequencies of the model is assessed after validating the accuracy of the results. The outcomes of this research have the potential to facilitate the advancement and production of lightweight and intelligent structures and devices, ultimately enhancing their efficiency. [ABSTRACT FROM AUTHOR]

Due to its superior reliability and performance, thick film technology is extensively employed in various applications, including automotive electronics, consumer electronics, communication engineering, and aerospace. However, a challenge arises from the mutual diffusion during the electronic paste production process, which leads to a decline in insulation performance and hinders the production of three-dimensional equipment. Inspired by the principles of low-temperature co-fired ceramic technology, a multi-layered ceramic structure has been successfully bonded using thick film technology by introducing a borosilicate glass-ceramics layer. To further enhance the properties of this multi-layered ceramic structure, approximately 8 wt% SiO 2 was incorporated into the borosilicate glass-ceramics. This addition effectively inhibits silver diffusion and reduces the diffusion depth within the glass-ceramic film. The key mechanisms behind this improvement are the increased activation energy for crystallization, resulting in a slower crystallization rate due to the addition of SiO 2. Moreover, the multi-layered ceramic with a sandwich structure exhibits remarkable properties. Notably, the dielectric strength of this system has been significantly enhanced to 13.9 kV/mm, accompanied by a high adhesion strength of 790 N. These enhanced properties of the optimized system indicate promising characteristics for multi-layer circuit applications. [ABSTRACT FROM AUTHOR]

This study analyzes the low-velocity impact response of cantilever sandwich beams with foam cores and carbon nanotube (CNT) reinforced facesheets. Using the fifth-order shear and normal deformation theory, we explore three CNT distribution types through the thickness of the facesheets: uniformly distributed UD, functionally graded-V FG-V, and functionally graded-Λ FG- Λ. The contact force during impact is calculated according to Hertz contact law. Our findings indicate that the FG-V distribution offers the highest contact stiffness, resulting in reduced deflection compared to UD and FG- Λ distributions. Additionally, an increase in the core-to-face thickness ratio leads to decreased deflection and increased contact force, attributed to enhanced beam stiffness. The volumetric fraction of CNTs also plays a critical role, increased CNT content raises beam stiffness, decreasing deflection and enhancing contact force. Furthermore, the impactor's initial velocity directly influences the deflection and contact force, with higher velocities leading to greater deflections due to increased kinetic energy. This comprehensive analysis underscores the significant effects of CNT distribution, volumetric fraction, and geometrical parameters on the dynamic response of sandwich beams under impact conditions. [ABSTRACT FROM AUTHOR]

AbstractIn this work, a higher order thickness stretched model is employed for electro-magneto-elastic results of a shear deformable baseball bat as a sandwich beam. The formulation is performed using the two dimensional constitutive relations as well as electric potential and magnetic induction relations for a shear deformable baseball bat. The proposed model can be used as a baseball bat in sport equipment. The principle of virtual work is employed to derive governing equations in the presence of thermal, electrical and magnetic loads. The physical model is a sandwich baseball bat beam composed of graphene origami reinforced copper matric core integrated with two piezoelectric/piezomagnetic face-sheets in thermal environment excited by electric and magnetic potentials. [ABSTRACT FROM AUTHOR]

Highlights Developing sustainable composites for engineering applications is essential for minimizing environmental impacts and ensuring the long‐term viability of infrastructure and technological advancements. In this context, this work focuses on the manufacture and evaluation of the structural integrity of a sandwich structure composed of aluminum faces and egg‐box‐shaped, sisal fiber‐reinforced epoxy (SFE) or castor‐oil polyurethane (SFC‐O) composites. The sandwich panel is filled with a biobased foam and subjected to dynamic load (drop‐tower) test. For comparison, the base materials SFE and SFC‐O molded into the egg‐box‐shaped cores are also evaluated using Charpy impact tests to establish a potential correlation between their Charpy performance and the drop‐tower behavior of egg‐box sandwich structures. The findings reveal that SFC‐O laminates demonstrate superior Charpy impact resistance (~49%) compared to SFE laminates. Similarly, sandwich structures composed of egg‐box‐castor‐oil composite cores absorb approximately 42.5% more energy than those made with egg‐box‐epoxy cores. The impact behavior of the sandwich structures correlates directly with the impact resistance of the sisal fiber laminates. Overall, the results indicate that the castor‐oil polymer can effectively replace the epoxy polymer matrix phase, enhancing impact absorption and providing an environmentally correct and sustainable solution for fabricating sandwich panels. Castor‐oil polymer provides laminates with lower density relative to epoxy. Sisal‐castor‐oil‐based laminates possess higher impact resistance than those based on epoxy. Sisal‐castor‐oil‐based panels achieve higher absolute and specific drop‐tower impact properties. Panels subjected to drop‐tower impact tests reveal skin delamination, wrinkling and indentation. Debonding between the foam and egg‐box core is a typical failure mode for epoxy sandwich panels. [ABSTRACT FROM AUTHOR]

The woven lattice sandwich composites (WLSCs) are susceptible to damage during service, which leads to a decline in their mechanical properties. Therefore, it is crucial to develop repair methods that specifically target the mechanical properties of WLSCs. In this study, repair techniques for the common types of skin and core damage in WLSCs were propose. The repair process begins with identifying the type of structural damage and removing the damaged section. Subsequently, the skin and core layers are repaired accordingly. The mechanical properties before and after repair are then compared through experimental evaluations. The results demonstrate that the carrying capacity of the repaired WLSCs is 85% higher than that of the original, unrepaired structure using the selected repair method. Highlights: Typical damage modes of woven lattice sandwich composites were classified.Repairing methods are proposed for woven lattice panels based on damage modes.Core‐foaming and skin patch adhering perfectly rehabilitate the damaged sandwich.Bearing capacity of the repaired sandwich slightly surpasses its original structure. [ABSTRACT FROM AUTHOR]

This study investigates the influence of nano clay reinforcement on the mechanical behavior of Kevlar/epoxy composite laminates and sandwich structures subjected to quasi‐static punch shear loading. Three types of composite face sheets were fabricated using hand lay‐up technique: Kevlar/epoxy neat, 0.5, and 1 wt. % of nano clay. The mechanical properties of these composites were characterized through compression, shear, and tensile tests. Sandwich structures were then constructed using the fabricated face sheets and an aluminum honeycomb core. Quasi‐static punch shear tests were performed on the composite laminates and sandwich specimens using hemispherical impactors. Numerical simulations of the punch shear tests were conducted in LS‐Dyna, employing appropriate material models and contact definitions for the constituent materials. Furthermore, to further investigate the failure mechanisms, scanning electron microscopy (SEM) analysis was conducted on the fractured Kevlar/epoxy composite plate specimens. The comparison between the experimental outcomes and numerical data demonstrated a strong correspondence, indicating consistency between the two methodologies. In conclusion, the incorporation of 0.5 wt. % nano clay into the Kevlar/epoxy composite resulted in a 5.09% increase in shear strength and an 11.29% increase in maximum reaction force. The study provides insights into the effect of nano clay reinforcement on the punch shear resistance and energy absorption capabilities of Kevlar/epoxy composites and sandwich structures. Highlights: Proper alignment of the nano clay within the epoxy was achieved.The most efficient rate of nano clay was observed to be 0.5% by weight.The mechanical properties of nano clay‐containing composites were improved.Quasi‐static punch shear tests were performed numerically and experimentally.Numerical results were in close agreement with experimental results. [ABSTRACT FROM AUTHOR]

The assessment of energy absorption behavior has a vital role in determining suitability of lightweight composites for impact protection applications. This study focuses on evaluating the energy absorption characteristics of cenosphere reinforced epoxy syntactic foam core and jute epoxy facesheet sandwich composite subjected to low velocity impact. The syntactic foam is composed of lightweight cenospheres embedded within an epoxy matrix, resulting in a high‐strength and lightweight composite material. Low velocity impact tests were conducted using a drop tower apparatus to simulate realistic impact conditions. The impact force, energy absorption and damage mitigation of the syntactic foam specimens with varied weight percentage of Cenosphere (0%, 10%, 20% and 30%) were measured and analyzed to assess the energy absorption behavior. The gradation revealed that the weight of top layer when compared to bottom layer is 50.49%, 70.23% and 95.74% less in syntactic foam core with 10, 20 and 30 wt% Cenosphere respectively, indicating gradation. The study demonstrates that the addition of Cenosphere up to 20 wt% enhances the energy absorption capacity of the sandwich composites by 59.37%–93.44% compared to sandwich without Cenosphere reinforced core. However, beyond this threshold, a decline in energy absorption is observed when subjected to low‐velocity impact (LVI). Fractography analysis demonstrates that the incorporation of Cenosphere induces a rough fracture surface with deep river‐like topography, indicative of greater energy absorption during impact loading. This substantiates the conclusion that Cenosphere‐reinforced syntactic foams exhibit enhanced impact resistance, making them promising materials for structures subjected to low‐velocity impact events. Highlights: Development of functionally graded core sandwich composite for low velocity impact applications.Assessing the performance of developed composites under low velocity impact loading.Determining the optimal weight percentage of cenospshere in functionally graded core.Studying the fractography of developed sandwich composites.Corelation between experimental and finite element studies. [ABSTRACT FROM AUTHOR]

AbstractThis article investigates the free vibration and damping characteristics of cylindrical sandwich shells with cutouts using both experimental and numerical approaches. The effects of cutout shape, size, and position on the dynamic response of cylindrical sandwich shells are explored. Moreover, Artificial Neural Network (ANN) models are constructed to predict the dynamic behavior of the sandwich shell with a cutout. A user-friendly application, Sandwich Shell Vibration Analysis (SSVibA), is developed, incorporating the ANN models to predict the non-dimensionalized natural frequencies and modal loss factors of the sandwich shell under different shell geometries, boundary conditions and cutout configurations. The objective of the present research is to advance the understanding of the dynamic behavior of sandwich structures by integrating experimental investigations, numerical analyses, and ANN modeling. [ABSTRACT FROM AUTHOR]

The composite material has been widely used in vehicle interiors, particularly in applications such as the wall-side panels of railways. The sandwich honeycomb composite, which combines two composite skins with a metal honeycomb, is the preferred structure in aerospace and railway applications due to its rigidity at minimal weight. As a functional composite material that provides heat flux to passengers, a multilayer sandwich Nomex honeycomb core composite with heating elements has been developed. In this design, the heating element is inserted into the inner composite material as a heat generation component, producing heat transferred to the other side of the panel. The thermal and structural behaviors of the sandwich composite with heating elements are orthotropic and require careful assessment to understand the material characteristics of the developed composite parts. In this study, conduction heat transfer in the functional honeycomb composite is simulated using the Finite Element Method (FEM) and validated with experimental results. The study proposes three steps to solve the problem: determining the heat-transfer parameters, simplifying the Nomex honeycomb core, and conducting a full-scale heat-transfer simulation. This research aids operating systems in controlling the heat generator input to prevent dangerous conditions. The results indicate that the simulation trends closely align with the experimental results. [ABSTRACT FROM AUTHOR]

Sandwich structures with functionally graded (FG) cores have gained interest in vibroacoustic applications. This article considers the vibroacoustic properties of double-walled sandwich magneto-electro-elastic (MEE) plates with a functionally graded carbon nanotube-reinforced composite (FG-CNTRC) core layer in a thermal environment. A coupled multiphysics model is developed based on third-order shear deformation theory (TSDT) and acoustic-structure interaction. Special attention is paid to the transmission loss of this arrangement for simply supported and clamped boundaries for four different kinds of CNT distributions, namely, UD, FG-V, FG-O, and FG-X. Sound velocity potential, normal velocity continuity conditions, and Hamilton's principle are used to generate the coupled vibroacoustic equations, which are then solved using the Galerkin method. The effects of boundary conditions, CNT distributions, cavity depth, multiphysics coupling fields, and temperature on the STL are comprehensively studied. The results provide guidelines for tailoring the dynamic response of these materials to achieve enhanced acoustic insulation performance. It enhances fundamental understanding and enables the engineering design of multilayered composite panels with optimized vibration and noise control capabilities. [ABSTRACT FROM AUTHOR]

To investigate the effect of different thickness ratios of the upper and lower panels on the foam aluminum sandwich panels, this paper conducts three-point bending tests. And use micro-CT technology to perform phased scans of the bending process in the experiment. The results show that, the collapse, splitting, and lateral extrusion of each cell are simultaneously present in three different forms of damage. At a span of 100mm, cell collapse dominates the damage deformation. At spans of 80mm and 60mm, splitting becomes the dominant factor. When the intrusion depth of the loading roller significantly increases, lateral extrusion damage becomes dominant. [ABSTRACT FROM AUTHOR]

Attaching viscoelastic materials (VEMs) to structures has been widely used to improve structural dynamic properties. Nevertheless, the adhesion of VEMs inevitably leads to the increase in overall structural mass. Topology optimization is one of the most effective methods to tackle this contradiction. In the traditional topology optimization, VEMs damping cores in constrain layer damping (CLD) sandwich structures are often simplified into linear elastic materials with constant parameters, usually ignoring their frequency-dependent and temperature-dependent dynamic characteristics, which will cause the distortion of the optimization results. Therefore, we propose a topology optimization method for CLD sandwich panels with a frequency-dependent VEM damping core considering steady-state free vibration in this study, where the anelastic displacement fields (ADF) model is adopted to combine the derived frequency-dependent complex constitutive relationship with the layerwise finite element (LFE) model, and the iterative modal strain energy (IMSE) method is used to determine the modal parameters of the CLD sandwich panels. The results of numerical examples show that the proposed method in this study not only has the advantages of simple and intuitive model, high calculation efficiency, and accuracy but also can achieve relatively good dynamic properties of the CLD sandwich structures. [ABSTRACT FROM AUTHOR]

Employing piezoelectrically activated beam-like structures is extending in numerous applications for instance energy harvesters and sensors. On the other hand, advanced materials such as carbon nanotube-reinforced nanocomposites are widely implemented in making passive structures with the aim of using their advantages. For the first time, a study is established on the critical temperature of a piezoelectric sandwich aggregated CNTRC beam regarding the pyroelectricity. The stabilization contribution of pyroelectricity against the thermal buckling incidence of sandwich beams has been demonstrated specifically. It is found that the pyroelectricity develops the critical point for the temperature of a clamped-clamped piezoelectric sandwich non-reinforced beam. [ABSTRACT FROM AUTHOR]

Functionally graded (FG) sandwich structures stand as one of the most representative composite structures owing to the thermal resistance and the energy absorption property in non-unfiorm thermal environment. Additionally, accurately estimating thermoelastic damping (TED) is of great importance for the design of high-performance micro/nano-resonators. Nevertheless, the classical TED models fail on the micro/nano-scale structures due to without considering the influences of the spatial size-dependent effects related to heat transfer and elastic deformation. The nonlocal heat conduction model and modified coupled stress theory are responsible for the size-dependent effects. To address this issue, present study aims to conduct the size-dependent TED model of FG sandwich microbeam resonators for TED analysis by incorporating the nonlocal dual-phase-lag (NDPL) heat conduction model and the modified coupled stress theory (MCST). It is assumed that the FG sandwich microbeam resonators consist of a ceramic core and FG surfaces. The energy equation and the transverse motion equation are formulated, and then, the analytical solution is solved by complex frequency method. Exact and closed-form expressions for TED can be obtained through the complex frequency method. The results are validated, and the parameter effects of the nonlocal thermal parameter, the material length-scale parameter, the power-law index and the vibration modes on the TED are analyzed. The results show that the energy dissipation can be reduced by the size-dependent effects resulting in improving the quality factor of microstructures. It is expected that these results may provide a theoretical basis for predicating TED in the design of FG sandwich micro/nano-resonators with high quality factor in extreme heat transfer environment. [ABSTRACT FROM AUTHOR]

The efficiency of a repair strategy applied to a honeycomb/carbon-epoxy sandwich beam was analyzed in this work. Experimental tests were performed considering three-point bending loading of undamaged, damaged and repaired specimens. In the damaged case, the central part of the core and of one of the skins were removed. The repair scheme consists of bonding a plug of honeycomb into the core and repairing the carbon-epoxy skin considering a scarf patch. A finite element analysis incorporating cohesive zone mixed-mode I + II analysis was performed. The resultant load-displacement numerical curves were compared with the experimental ones. It was verified that the repair procedure is efficient regarding recovery of the initial stiffness and strength of the undamaged case, and it was concluded that the proposed numerical model is a valid tool to deal with repair of sandwich beams. [ABSTRACT FROM AUTHOR]

Water electrolysis is considered the cleanest method for hydrogen production. However, the widespread popularization of water splitting is limited by the high cost and scarce resources of efficient platinum group metals. Hence, it is imperative to develop an economical and high‐performance electrocatalyst to improve the efficiency of hydrogen evolution reaction (HER). In this study, a hierarchical porous sandwich structure is fabricated through dealloying FeCoNiCuAl2Mn high‐entropy alloy (HEA). This free‐standing electrocatalyst shows outstanding HER performance with a very small overpotential of 9.7 mV at 10 mA cm−2 and a low Tafel slope of 56.9 mV dec−1 in 1 M KOH solution, outperforming commercial Pt/C. Furthermore, this electrocatalytic system recorded excellent reaction stability over 100 h with a constant current density of 100 mA cm−2. The enhanced electrochemical activity in high‐entropy alloys results from the cocktail effect, which is detected by density functional theory (DFT) calculation. Additionally, micron‐ and nano‐sized pores formed during etching boost mass transfer, ensuring sustained electrocatalyst performance even at high current densities. This work provides a new insight for development in the commercial electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

This paper presents analysis and comparison of test methods for determining transverse shear strength and shear modulus of steel-faced sandwich panels commonly used in construction. The test methods are taken from the governing European standard EN 14509:2013. Two-point loading and four-point loading test methods as well as a full-scale test method are examined. Based on extensive experimental work on sandwich panels with varying core thickness, comprising mineral wool (MW) and polyisocyanurate (PIR) and encompassing both roof and wall panels, this study provides details of the test setup for the four-point loading and vacuum box methods with which a pure shear failure is obtained. Such details are missing from EN 14509. This paper highlights that the two-point loading method fails to consistently produce shear failure, especially in thicker panels, indicating it does not accurately measure transverse shear strength. The results of the experiments conducted in this study indicate that the four-point loading and full-scale test methods provide consistent shear failure for thicker panels while yielding greater transverse shear strength than the two-point loading test in general. [ABSTRACT FROM AUTHOR]

Auxetic structures possess negative Poisson's ratio (NPR). They exhibit enhanced indentation resistance, synclastic deformation, high fracture toughness and high energy absorption. Several sorts of auxetic structures exist, such as re-entrant, arrowhead, chiral, etc. The re-entrant structure is the most common sort of auxetic structures. This paper investigates the mechanical behavior of the re-entrant auxetic structure using experimental and numerical methods. Two modified re-entrant topologies are proposed based on the original (conventional) re-entrant topology. Using these modified topologies, two re-entrant auxetic sandwich structures are designed and 3D printed using fused deposition modeling (FDM) out of polylactic acid (PLA). Conducting compression, three and four-point bending tests, the compressive and flexural performance of the two new re-entrant auxetic sandwich structures is studied and compared with the original (conventional) re-entrant structure. More specifically, Poisson's ratio, compressive modulus, flexural stiffness and maximum loads of the structures are focused and studied. The mechanical properties of auxetic sandwich structures are improved using modified topologies. The new re-entrant auxetic sandwich structures show 11% higher normalized compressive modulus and 9% higher normalized flexural stiffness than the original re-entrant structure. [ABSTRACT FROM AUTHOR]

The article establishes a finite element (FE) model of sandwich panel (referred to as CSC FE model) using shell structure core and solid structure face sheet and provides a detailed derivation of the data transfer process between the shell structure and the solid structure in the FE model. In order to explore the application of CSC FE model in the curved surface sandwich panel forming, this paper studies the single curvature and double curvature sandwich panel forming in detail. Based on the maturity of the three-point bending theory, in order to facilitate theoretical verification, the article chooses the three-point bending process to study the single curvature sandwich panels forming. It is proved that the CSC FE model can be effectively applied to single curvature sandwich panel forming through three-point bending theory, numerical simulations and experiments of brazed aluminum honeycomb panel (BAHP). Low cost and efficient multi-point forming (MPF) process is used to analyze the double curvature sandwich panel forming. By MPF experiments and numerical simulations of saddle-shaped and spherical BAHPs, and with the help of 3D laser scanning technology, it is proved that the CSC FE model can accurately predict the curved surface shape of double curvature sandwich panel forming. [ABSTRACT FROM AUTHOR]

Owing to the ability of negative Poisson's ratio (NPR) structures in enhancing the stiffening effectof shear stiffening gels (SSG), combining the two in cushioning applications has attracted much attention. This paper presents the design of NPR flexible cushioning sandwich composites featuring a double-arrow structure (DAS). The DAS is optimized using a modified genetic algorithm, and the cohesive property is leveraged to reinforce the stiffening effect of SSG, thereby improving the material's cushioning efficiency. The synergistic effect of the DAS and SSG and the law of SSG arrangement on the energy absorption efficiency of cushioning were revealed using the finite element method and experiment. It can be found that the size effect of the DAS significantly contributed to the enhancement of the energy-absorption efficiency of the SSG stiffening. In double-arrow sandwich composite (DASC), the larger reversed-triangle deformation and the increased number of reversed-triangle configurations, amplified the shear stiffening of the SSG, improving the impact load dissipation and energy absorption efficiency of sandwich composite. The energy absorption efficiency of the DASC was improved owing to the synergistic effect of the DAS cohesive effect and the SSG stiffening properties, with the energy absorption ratio and mass specific energy absorption increased by 83.02% and 136% compared to neat polyurethane. The DASC optimized in this study has good flexibility and energy absorption capacity and is promising for application in the field of flexible protection. [ABSTRACT FROM AUTHOR]

3D Kagome lattice sandwich structure is recognized as the most excellent lattice configuration. However, the preparation method of 3D Kagome is complicated and the raw materials for its preparation are limited to materials with high plasticity. In this study, we developed a wood-based 3D Kagome lattice structure that combines discrete rods into a continuous core using reinforcement. Orthogonal tests, theoretical analysis, and finite element simulations were performed to investigate the correlation between the dimensional parameters, the mechanical properties, and the energy absorption capacity. The damage modes were found to be mainly bending fracture, core shear, and panel rupture, with the use of reinforcement affecting the damage modes. Compressive properties of the 3D Kagome lattice structure are increased by increasing core diameter and inclination degree, decreasing core in-cut diameter, and using high-strength reinforcements. Finite element simulations further confirm that the use of high-strength reinforcements changes the stress distribution of the lattice structure. The 3D Kagome lattice structure with an inclination degree of 65°, a core diameter of 10 mm, a reinforcement wall thickness of 2 mm, and a core in-cut diameter of 2 mm has the optimal compression performance and energy absorption capacity. [ABSTRACT FROM AUTHOR]

Sandwich pipes are widely used in various piping applications owing to their exceptional pressure resistance and thermal insulation properties. In this paper, the mechanical properties and loading performance of sandwich pipes made of polypropylene material have been investigated under different loading conditions including lateral and axial compression, as well as hydrostatic internal and external pressures. For this purpose, finite element models of sandwich pipes with various designs have been developed. Material properties have been determined through standard experimental tests, and the finite element models have been validated using lateral compression experiments. The results indicate that incorporating annular cores with thinner thickness and greater numbers, along with using a thicker inner pipe in the sandwich pipe structure, improves its properties and performance. [ABSTRACT FROM AUTHOR]

Hail presents a significant threat to the structural integrity of aircraft, particularly with the extensive use of foam sandwich structures in aerospace applications. Therefore, it is crucial to consider the effects of hail impact on foam sandwich structures. This paper aims to investigate the impact of ice projectiles on carbon Fiber/PMI foam sandwich structures, using both experimental and numerical simulation approaches. The gas cannon was employed to launch ice projectiles, which were then directed towards the carbon Fiber/PMI foam sandwich structures. Additionally, a numerical simulation model was developed using ANSYS/LS-DYNA software to analyse the impact of these ice projectiles. Moreover, the validity of the finite element model was confirmed through experimental verification. The study involves simulations of single-point continuous impacts of ice projectiles and multi-point simultaneous impacts on carbon Fiber/PMI foam sandwich structures, while maintaining the same total impact energy. By varying the distribution of ice projectiles, the dynamic response and damage characteristics of the target plate are analysed. Specifically, the research aims to investigative the deformation characteristics of the target plate and the energy absorption of the structure. The research results underscore the importance of considering the distribution of ice projectiles in mitigating structural damage caused by hail impact. [ABSTRACT FROM AUTHOR]

Highlights The engineering structures with cutouts should consider both buckling and stiffness. Inspired by the multi‐level leaf veins, in this paper, the skeleton of the grid‐honeycomb sandwich structure was designed in the hierarchical form, and combined with the cutout characteristics of the side walls of the railway vehicle body, the multi‐objective stiffness and mass optimization of the skeleton layout under buckling constraints was achieved. The cutout honeycomb sandwich structure was designed with orthogonal grids in the stiffness design area and curved grids based on the quadratic polynomial in the buckling design area. The optimization model also included the linear angle hierarchical grid, the constant angle hierarchical grid, and the single‐level orthogonal grid. The multi‐objective optimization framework based on the Radial Basis Function (RBF) surrogate model and the Non‐dominated Sorting Genetic Algorithm (NSGA‐II) was developed. The optimization results indicated that the hierarchical grid provided the more extensive design space. The optimal solution of the quadratic polynomial hierarchical grid had the highest stiffness and stiffness per unit mass compared to the rest of the grid layouts, which were 23.28% and 30.47% higher than the single‐level orthogonal grid, respectively. Finally, the multi‐order eigenvalue buckling was analyzed based on the optimal structure. Layout of hierarchical grids proposed inspired by multi‐level leaf veins. Orthogonal grids ensure stiffness and curved grids inhibit buckling at cutouts. Apply the hierarchical grids as skeletons to honeycomb sandwich structures. Stiffness and mass optimization subject to buckling constraints is performed. [ABSTRACT FROM AUTHOR]

Curved shells are increasingly utilized in applied engineering due to their shared characteristics with other sandwich structures, flexibility, and attractive appearance. However, the inability of controlling and regulating vibrations and destroying them afterward is a challenge to scientists. In this paper, the curve shell equations and a linear quadratic regulator are adopted for the state feedback design to manage the structure vibrations in state space forms. A five-layer sandwich doubly curved micro-composite shell, comprising two piezoelectric layers for the sensor and actuator, is modeled by the fourth-order shear deformation theory. The core (honeycomb, truss, and corrugated) is analyzed for the bearing of transverse shear forces. The results show that the honeycomb core has a greater effect on the vibrations. When the parameters related to the core and the weight percentage of graphene increase, the frequency increases. The uniform distribution of graphene platelets results in the lowest natural frequency while the natural frequency increases. Furthermore, without taking into account the piezoelectric layers, the third-order shear deformation theory (TSDT) and fourth-order shear deformation theory (FOSDT) align closely. However, when the piezoelectric layers are incorporated, these two theories diverge significantly, with the frequencies in the FOSDT being lower than those in the TSDT. [ABSTRACT FROM AUTHOR]

A multi-layer structure by sandwiching rigid cellular PVC (polyvinyl chloride) foam between two GFRP (glass-fibre reinforced plastic) faces is studied in order to investigate the sample edge effects on fatigue life of the sandwich structure. Therefore, a new geometry of specimen is developed based on numerical simulation approach. Compared to the results given by the ASTM C393 standard, the experimental study was confirmed that edge effects are leading to early failures as the shear stresses concentration was shifted from the new geometry. An optimal prediction of fatigue life of foam-based sandwich has been established during bending fatigue test. The different failure modes were followed by microstructural analyses to better explain the global behaviour of the structure. [ABSTRACT FROM AUTHOR]

In this study, recycled Ti6Al4V alloy powder was utilized as a reinforcement to enhance the mechanical and modal properties of polyurethane foam (PUF) core-based sandwich composites. Sandwich composite having carbon fiber reinforced polymer (CFRP) composite face sheets and Ti6Al4V powder-reinforced PUF cores were manufactured. The PUF cores were reinforced with two different variants of Ti6Al4V powder based on particle sizes from 1 to 3 wt.%. The dispersion quality was investigated using scanning electron microscopy (SEM). A detailed experimental modal analysis was conducted to evaluate the modal properties in terms of the natural frequencies and damping ratios of the sandwich specimens. A comprehensive mechanical study was also conducted in terms of compression, buckling, flexural, and impact tests according to the relative ASTM standards. The experimental results demonstrated that the Ti6Al4V reinforced sandwich specimens exhibited superior mechanical and modal properties with enhanced PUF cores. Improvements in excess of 21%, 37%, and 24% were recorded in the compression, buckling, and flexural response of the reinforced specimens, respectively, compared to those of their neat counterparts. Similarly, remarkable improvements were also observed in the experimental modal and impact properties of the Ti6Al4V alloy powder-reinforced sandwich composites. [ABSTRACT FROM AUTHOR]

Composite materials are often exposed to repeated impact in their industrial applications, which can have serious consequences on their mechanical performance. Therefore, the key purpose of this investigation is to study experimentally and numerically the response of laminated composites and sandwich composites. This involves evaluating their mechanical response and the damage accumulation under repeated impacts. The numerical models developed using the ABAQUS/Explicit software were validated against experimental data obtained through a modified Charpy test, where initial impact energies of 30 J, 40 J, and 50 J were applied to the two composite types under investigation. This was achieved by comparing commonly used parameters such as absorbed energy and induced energy. The results confirm that the first impact is responsible for the damage and that the repetition of the impact has no fundamental effect on the shape of the damage, but slightly increases its surface area. The numerical results made it possible to accurately predict the absorbed energy values and traces of damaged areas observed experimentally. [ABSTRACT FROM AUTHOR]

Highlights This study examines the effects of multilayering in sandwich panel composite structures with different corrugated core configurations under quasi‐static indentation loading. The panels were fabricated using woven glass fibers and epoxy resin via the Vacuum Infusion Process. Experiments were conducted using two hemispherical cylindrical indenters with a diameter of 20 mm (ID = 20 mm) and 10 mm (ID = 10 mm) and the behavior of the composite structure in terms of contact force and fracture mechanisms for different core corrugations (square and butterfly) were investigated in two ways with foam and without foam. The experimental results demonstrate that, among corrugated core geometries without foam, butterfly cores outperform square cores in terms of structural strength, maximum force, moment force, energy absorption, specific energy absorption, and displacement until full indentation. Moreover, the butterfly core shows a higher peak load and different failure mechanisms compared to the square core. Under loading with a 10 mm indenter, the butterfly core without foam only experienced perforation in the loading area, without fracture completely. Also, adding foam did not change failure mechanisms and mechanical behavior in the butterfly geometry. However, in the square geometry, foam filled gaps between the core, preventing fracture completely and leading to only perforation in the loading area, unlike the specimen without foam. The visual analysis during the quasi‐static indentation process revealed several significant damage mechanisms, including matrix cracking, fiber breakage, delamination, buckling and crushing of cell walls, damage to top sheets, core separation, and complete indentation of the samples. Delamination and indentation failure mechanisms were seen on the butterfly core. Skin indentation and rib fracture failure mechanisms were seen on the square core. Butterfly corrugated cores revealed the best performance without/with foam. The core shape was more effective on the strength than the foam addition. [ABSTRACT FROM AUTHOR]

A refined hyperbolic shear deformation theory is presented to analyze the mechanical behavior of isotropic and sandwich functionally graded material (FGM) beams under various boundary conditions. The material properties are considered to be isotropic at each point and change across the thickness direction. The volume fraction gradation follows a power law distribution with respect to the FGM core or skins of the beam. The solution is attained by minimizing the total potential energy. This recent theory is a new type of third-order shear deformation theory that includes undetermined integral variables. The recent theory describes the variation of transverse shear strains throughout the thickness of a beam. It shows how these strains satisfy the zero traction boundary conditions on the top and bottom surfaces, all without the need for shear correction factors. An analytical solution based on trigonometric series is developed to solve the problem while satisfying various boundary conditions. Comparative studies are conducted to validate the accuracy and efficiency of this method. The current model can accurately predict the static responses of functionally graded isotropic and sandwich beams with arbitrary boundary conditions. [ABSTRACT FROM AUTHOR]

This article discusses the impact of hybrid nanoparticle reinforcements on the mechanical properties of Epoxy-Polylactic Acid (PLA) composites. The researchers conducted experiments and numerical analysis to investigate the effects of adding different fillers on the tensile and bending strength of the composites. The results showed that the addition of nanofillers, such as SiO2, graphene nanoplatelets (GNPs), and multi-walled carbon nanotubes (MWCNTs), improved the mechanical properties of the composites. The study provides valuable insights for researchers and engineers working with epoxy-PLA composites. Additionally, the article references two related articles that provide further insights into the mechanical behavior of composite materials. [Extracted from the article]

The present study is done to perform the optimal design of the structural components of the buildings against the unwanted wind load exerted on their outer face. To this end, the case study of the research is the outer wall made of a one-floor building modeled as a rectangular plate with only one free edge and three clamped ones. It is assumed that the wall is a sandwich plate whose core is made of auxetic material and dace-sheets are reinforced with nanoparticles of graphene platelets (GPL). Differential equations governing the system's motion are obtained within the background of the plate's shear-deformation theories. The stability analysis of the sandwich wall is performed based on the application of artificial intelligence (AI) methods optimized with an innovative optimization approach to gain a high level of accuracy. To determine the stability information of the system at the train points, the differential quadrature approach (DQA) is applied as the solver of differential equations of motion. The accuracy of the methods used in this paper is examined and verified by comparing the results with those acquired in the articles published previously. The results obtained in this study provide very useful information about the stability response of lightweight building components through AI-based solutions. [ABSTRACT FROM AUTHOR]

Compared with traditional honeycomb and stiffened sandwich structures, lattice-based structures are considered an ideal substitute for traditional core structures due to their high stiffness and other potential multifunctional application characteristics. Based on that, the sound radiation characteristics of the sandwich plate with different truss cores under structure borne excitation were investigated in the current paper, wherein three truss cores, including pyramidal, tetrahedral and 3D-kagome cores types, are considered. The governing equations for the vibration and sound radiation analysis of the sandwich plate structure are carried out using the static equilibrium method, and then solved via the Navier approach and Rayleigh integral. By comparing the experimental results, the validity of the proposed theoretical model is verified. The theoretical model is subsequently used to investigate the influences of truss core geometric parameters and types, face sheet-core face sheet thickness ratio and aspect ratio on sandwich plate sound radiation characteristics. The results indicate that, in the range [ 5 ∘ ≤ θ ≤ 52 ∘ ] and [ 52 ∘ < θ ≤ 85 ∘ ] , the tetrahedral and 3D-Kagome core types have the maximum natural frequency values, respectively, while the resonance peaks of sound pressure level curves move to lower frequency region with the increase in truss core radius and face sheet-core face sheet thickness ratio, and the sandwich plate with the 3D-kagome core shows better sound radiation characteristics in the wide frequency range. [ABSTRACT FROM AUTHOR]

This paper describes the in-plane impact behavior of 3D woven honeycomb sandwich composites comprising glass fiber reinforced epoxy composite. In this study, 3D woven honeycomb structures with similar cell shapes were developed with different cell geometry by varying the cell size, free wall length, bonded wall length, opening angle, and the number of honeycomb layers keeping the overall thickness of the composite constant. The variation of cell geometry was carried out by changing the number of picks in the honeycomb walls. Composite samples were made using VARIM (vacuum-assisted resin infusion method) process. The behavior of the force-displacement curve and the energy-time relationship under impact loading of 100 J were analyzed. The total energy absorption was determined for different cell geometry and the number of layers of the honeycomb composites. The results showed that structural changes in honeycomb composite significantly affect the specific energy absorption. The specific energy absorption increases with a large cell size, less opening angle, higher wall length, and a greater number of layers. [ABSTRACT FROM AUTHOR]