Layered Shells Research Articles

Analytical study on sandwich shells considering partial degree of composite action

This paper is focused on a new structural type - sandwich shell, which includes inner and outer shells connected by hoop connectors to achieve composite action; and a functional layer in the middle. Considering that the hoop connectors are not completely rigid, there will be limited slip between the inner and outer shells, which will lead to partial Degree of Composite Action (DCA). Due to the existence of the hoop connectors and shear lag effect, the stress distribution along the width direction of the shell is uneven, which can be described by effective width. Considering all these factors, this paper first develops an analytical model for sandwich shells with different configurations of connectors; and uses finite element analysis results to verify the analytical model. Next, a parametric study is conducted using the analytical model to study the effects of material strength, the ratio of the thickness of the functional layer to the thickness of the single layer shell, and the ratio of the arc length to the width of the sandwich shell on the effective width. It is found that DCA can significantly affect the stress and strain distributions of the sandwich shell. The effective width for 100% DCA can be used as a conservative value to represent those of other DCAs. Finally, a simplified calculation formula, which can be used in practical design, is derived based on the effective width for 100% DCA.

Synthesis and Investigation of Mechanical Properties of the Acrylonitrile Butadiene Styrene Fiber Composites Using Fused Deposition Modeling.

Additive manufacturing is becoming a global phenomenon due to its versatile properties and numerous benefits, which is not possible by conventional machining processes. Fused deposition modeling (FDM) shows a huge potential of shift from rapid prototyping toward the rapid manufacturing. Nowadays, the strength of the FDM-printed parts is very important to consider along with all the printing parameters, which affect the strength of these parts. This study includes the investigation of printing parameters (infill density, layer thickness, and shell count) on the strength of FDM-printed parts of acrylonitrile butadiene styrene (ABS) and carbon fiber-reinforced ABS (ABS-CF). These printing parameters directly affect the quality as well as the strength of the 3D-printed parts through FDM. Tensile tests were performed on the universal testing machine on both types of printed parts. The optimized parameters for the 3D-printed samples of the pristine ABS are found to be 0.1045 mm of layer thickness, 57.72% of infill density, and 7.63 numbers of shell count, while the optimum parameters obtained for ABS-CF are 0.2780 mm of layer thickness, 28.37% of infill density, and 9.88 numbers of shell count. The results show that the layer thickness and shell count have a significant effect on the ultimate tensile strength of the 3D-printed parts.

A soy protein-based adhesive with improved mechanical and electromagnetic shielding properties by employment of core@double-shell BT@PDA@PANI fillers

Resolving indoor electromagnetic interference (EMI) and radiation pollution caused by electromagnetic waves have become paramount. Plywood is broadly used in interior decoration and give them EMI shielding function will be significant for addressing these issues. Herein, inspired by the mussel underwater bonding strategy and oyster, polydopamine (PDA) graft transition layer was introduced between inorganic BaTiO3 (BT) core layer and organic polyaniline (PANI) shell layer to construct controllable core@double-shell BT@PDA@PANI nanoparticles. The epoxide polymer and aldehyde-decorated carbon dots (CDs) were used as crosslinkers to form the covalent bonds and dynamic covalent bonds within the adhesive network. The core@double-shell nanoparticles were used as a reinforcing element and crosslinker to construct an organic–inorganic hybrid protein adhesive. This as-prepared protein adhesive exhibits remarkable improvements in wet shear strength (1.16 MPa), dry shear strength (1.97 MPa), and water resistance. Encouragingly, the plywood with in-situ formulated adhesives is an absorption dominated EMI shielding material and reveals an excellent EMI SET of 38.04 dB EMI in the X-band, significantly outperforming most of the reported synthetic materials. This outstanding performance is attributable to its superior conductivity and unique hierarchical structure of plywood. Therefore, this study offers a facile, environmentally-friendly, and economically feasible strategy for preparing high-performance adhesives to address indoor EMI problems.

Selective Oxygen Activation to Reactive Oxygen Species on a Carbon Layer-Encapsulated CuxO Electrocatalyst for Water Purification.

In situ synthesis of reactive oxygen species (ROS) on demand via oxygen activation (OA) is significant in biological, chemical, and environmental fields. Thus, the design of OA catalysts with adequate reactivity, durability, and selectivity is critical but challenging. Here, we report a CuxO@C core@shell photoelectrode prepared by encapsulating Cu/Cu2O/CuO into a carbon layer through anodic electropolymerization (electrophoresis-coupled self-assembly of carbon quantum dots). Theoretical prediction and experiments indicate that the carbon layer can effectively facilitate optical trapping and charge transfer, thus promoting photoelectric conversion and anti-photocorrosion performance of CuxO@C. The inner CuxO core acts as an electron reservoir and continuously injects electrons into the outer carbon layer shell, and the carbon atoms adjacent to oxygen-enriched functional groups (C-O-C and -COOH) in the electron-rich carbon layer work as the reactive sites to adsorb O2 and donate electrons to the antibonding orbital [lowest unoccupied molecular orbital (π*)] of dioxygen. Optimized adsorption and hydrogenation of the critical intermediates (*O2, *OOH, and *H2O2) and thermodynamically tunable O-O bond cleavage enable O2 being selectively reduced to the superoxide anion and hydroxyl radical via the mixed multielectron processes consisting of one- and three-electron pathways. Sulfamethoxazole, an emerging refractory organic contaminant widely present in the environment, can be effectively degraded (∼100% removal) in such an electrochemical platform, benefiting from the abundant ROS generated in situ. Our findings demonstrate an innovative strategy to develop highly efficient and selective OA catalysts for practical water purification.

Producing Soft Magnetic Composites by Spark Plasma Sintering of Pseudo Core-Shell Ni-Fe Alloy@Mn0.5Zn0.5Fe2O4 Powders.

Soft magnetic composite (SMC) cores have been obtained by Spark Plasma Sintering (SPS) using pseudo core-shell powders. Pseudo core-shell powders are formed by a core of soft magnetic particle (nanocrystalline permalloy or supermalloy) surrounded by a thin layer (shell) of nanosized soft ferrite (Mn0.5Zn0.5Fe2O4). Three compositions of pseudo core-shell powders were prepared, with 1, 2 and 3 wt.% of manganese-zinc mixt ferrite. The pseudo core-shell powders were compacted by SPS at temperatures between 500 and 700 °C, with a holding time ranging from 0 to 10 min. Several techniques have been used for characterization of the samples, both, powders and compacts X-ray diffraction (XRD, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), magnetic hysteresis measurements (DC and AC) and electrical resistivity. The electrical resistivity is in the order of 1 × 10-2 Ωm, 3-4 orders of magnitude higher than supermalloy electrical resistivity. The SPS at lower temperatures (500 °C) conserves the initial phases of the composite, but increasing the sintering temperature and/or sintering time produces a solid-state reaction between the alloy and ferrite phases, with negative consequence on the magnetic properties of the compacts. The initial relative permeability is around 40 and remains constant until to 2000 Hz. The power losses are lower than 2 W/kg until to 2000 Hz.

Determination and analysis of the thermoelastic state of layered orthotropic cylindrical shells

The fundamental relations of the quasi-static problem of thermoelasticity are written for a finite layered orthotropic cylindrical shell of an antisymmetric structure. Under convective heat transfer on the surfaces of this shell and under a linear dependence of temperature on the transverse coordinate, the basic system of equations for the integral characteristics of temperature is given. The method is proposed for solving the formulated problems of thermoelasticity and thermal conductivity, using the double finite integral Fourier transform with respect to the corresponding coordinates of the transformation and Laplace transform with respect to the time. The results of a numerical analysis of temperature, deflections, and stresses for the considered two-layer shell hinged at the edges under local heating by the initially specified temperature field are presented.

Тонкие наноструктурированные пленки n-WSe2 и их применение в полупроводниковых фотокатодах p-Si для получения водорода расщеплением воды

The possibilities of modification of the structure and type of conductivity of WSe2 films formed on p-type silicon by thermal treatment of a thin-film precursor, which was preliminarily created by pulsed laser deposition, are studied. Pulsed laser ablation of WSe2 and rhenium targets made it possible to obtain amorphous films WSex (x > 2) containing rhenium atoms and inclusions of β-W nanoparticles. Heat treatment at 450 °C caused the crystallization of the amorphous matrix and the formation of a layered 2H-WSe2 shell surrounded the metal nanoparticles. Doping with rhenium led to the production of n-type WSe2 semiconductor films, which, in terms of their properties (band gap ~ 1.2 eV, high catalytic activity, low resistance to current transport), represent a promising material for creating p-Si photocathodes for efficient light-activated hydrogen evolution in acid solution. Theoretical calculations are carried out, which make it possible to identify local areas on the surface of the formed WSe2 films with enhanced catalytic activity in hydrogen evolution reaction.

Quasi-static problem of thermoelasticity for layered shallow cylindrical shells of irregular structure

For rectangular layered shallow cylindrical shells of irregular structure, the quasi-static problem of unbound thermoelasticity is formulated. As a mathematical model, the equations of the shear theory of shallow shells of Timoshenko type are used. The closed solution for the formulated problem is found by the methods of integral transformations. The distribution of temperature, displacements, forces and moments in a two-layer cylindrical shell under local convective heating is analyzed numerically.

Стійкість нетонких анізотропних циліндричних оболонок в просторовій постановці під розподіленим боковим тиском

A three-dimensional approach to solving the problem of stability of non-thin cylindrical anisotropic layered shells under distributed lateral pressure is proposed. Based on the modified Hu-Washizu variational principle, a three-dimensional system of homogeneous differential stability equations is obtained for the calculation of shells, the anisotropy of which is characterized by a material with one plane of elastic symmetry. The solution of the three-dimensional system was carried out using the Bubnov-Galerkin methods and numerical discrete orthogonalization. The influence of an increase in the number of cross-laid layers of the same thickness on the stability of an anisotropic cylindrical shell is studied. The results of the solution are presented by graphs and their analysis is given.

Gigantic supramolecular assemblies built from dynamic hierarchical organization between inorganic nanospheres and porphyrins.

Noncovalent ionic interactions between nanosized Keplerate-type capsules {Mo132} and tetra-cationic porphyrins have been investigated in aqueous solution using small-angle X-ray scattering, 1H NMR and photophysical methods. These complementary multiscale methods reveal the formation of large hybrid oligomers built from a short-range organization in which the cationic porphyrin is glued onto the large POM surface. The local structuring appears to be strongly dependent on the dye : {Mo132} ratio changing the morphology of the oligomers from linear to dense aggregates.

Побудова критерію довготривалого руйнування втоми для тонкостінних шаруватих оболонок

A model and criterion of long-term fatigue failure for thin-walled layered shells is built, taking into account the influence of the type of stress state. The problem of calculating the number of cycles to failure under combined loading is considered. Solutions are built on the basis of the concept of equivalent stresses. The problem of determining local stresses in composites of random structure is formulated within the framework of the second-order nonlinear theory. The solution of the stochastic boundary value problem on determining the stress concentration in a unidirectional composite with a metal matrix (MMC) was obtained. To build a complete system of equations of the second order, the method of successive approximations is used. The parameters of the stress concentration at the boundary of the components are determined. The given examples show the importance of the influence of nonlinear properties on the redistribution of stresses near the fibers. The possibility of predicting the long-term strength of the material is shown. The necessary information about the material for the formulation of failure criteria is the S-N curves for individual components of the combined stresses.

Microstructural heterogeneity of the buffer layer of TRISO nuclear fuel particles

Tristructural isotropic (TRISO) nuclear fuel particles contain a layered spherical shell designed to retain fission products; however, failure occurs in rare cases—commonly initiated in the porous pyrocarbon buffer layer. Achieving a comprehensive understanding of the buffer-initiated failure mechanisms requires detailed characterization of the buffer porosity and its heterogeneous distribution across multiple length scales. We performed FIB-SEM tomography across the buffer layer thickness (∼100 µm) to produce 3D reconstructions of the buffer microstructure with 50 nm spatial resolution. We found an average overall porosity of ∼14%, which does not solely account for the low density of the buffer (50% of the theoretical density). Additionally, the local porosity and its fluctuation increase from the kernel interface towards the inner pyrocarbon (IPyC) layer, which we attribute to the chemical vapor deposition process conditions during the TRISO particle fabrication. Detailed characterization of the porous microstructure—including analysis of the pore size, distribution, shape, and orientation—provides insight into the process-structure-property-performance relations of TRISO nuclear fuel particles and will inform multiscale models designed to predict the failure of TRISO particles under irradiation.

Medium/High‐Entropy Amalgamated Core/Shell Nanoplate Achieves Efficient Formic Acid Catalysis for Direct Formic Acid Fuel Cell

AbstractHigh‐entropy alloys (HEAs) have been attracting extensive research interests in designing advanced nanomaterials, while their precise control is still in the infancy stage. Herein, we have reported a well‐defined PtBiPbNiCo hexagonal nanoplates (HEA HPs) as high‐performance electrocatalysts. Structure analysis decodes that the HEA HP is constructed with PtBiPb medium‐entropy core and PtBiNiCo high‐entropy shell. Significantly, the HEA HPs can reach the specific and mass activities of 27.2 mA cm−2 and 7.1 A mgPt−1 for formic acid oxidation reaction (FAOR), being the record catalyst ever achieved in Pt‐based catalysts, and can realize the membrane electrode assembly (MEA) power density (321.2 mW cm−2) in fuel cell. Further experimental and theoretical analyses collectively evidence that the hexagonal intermetallic core/atomic layer shell structure and multi‐element synergy greatly promote the direct dehydrogenation pathway of formic acid molecule and suppress the formation of CO*.

Medium/High-Entropy Amalgamated Core/Shell Nanoplate Achieves Efficient Formic Acid Catalysis for Direct Formic Acid Fuel Cell.

High-entropy alloys (HEAs) have been attracting extensive research interests in designing advanced nanomaterials, while their precise control is still in the infancy stage. Herein, we have reported a well-defined PtBiPbNiCo hexagonal nanoplates (HEA HPs) as high-performance electrocatalysts. Structure analysis decodes that the HEA HP is constructed with PtBiPb medium-entropy core and PtBiNiCo high-entropy shell. Significantly, the HEA HPs can reach the specific and mass activities of 27.2 mA cm-2 and 7.1 A mgPt -1 for formic acid oxidation reaction (FAOR), being the record catalyst ever achieved in Pt-based catalysts, and can realize the membrane electrode assembly (MEA) power density (321.2 mW cm-2 ) in fuel cell. Further experimental and theoretical analyses collectively evidence that the hexagonal intermetallic core/atomic layer shell structure and multi-element synergy greatly promote the direct dehydrogenation pathway of formic acid molecule and suppress the formation of CO*.

Analysis of confined masonry with strengthening around the opening

Analysing confined masonry (CM) with strengthening around the opening (analytical model) was conducted numerically. The opening variations were centric and eccentric opening doors with an opening ratio of 16.93% and 31.75%; centric and eccentric opening windows with opening ratios of 10.16% and 19.05%. This analysis aims to apply the procedure for analysing the CM models by using layered shell elements and also comparing the behaviour and performance of each model. The masonry and frames were modelled using layered shell elements in SAP2000 software and analysis were done by using nonlinear static pushover analysis. This analysis starts by making a validation model based on other experimental work and comparing the behaviour of the structure modelled in the form of CM without openings and CM with openings. The results show that both models have load-displacement diagrams similar to the experimental results. By using the same modelling method applied to the analytical model, it was found that CM with large opening ratios have less strength than small opening ratios, and CM with centric openings was more robust than the eccentric openings.

Shape Memory Effect in a Composite Layered Shell of Complex Shape

Shape Memory Effect in a Composite Layered Shell of Complex Shape

Experimental and numerical research of ultrahigh performance concrete layered shell element based on a two-dimensional fixed crack model

Ultrahigh performance concrete (UHPC) is a cement-based material with superior characteristics including tension strain-hardening and multi-cracking, which is attractive for application in the field of assembled structures. However, a reliable method for simulating the mechanical behaviour of UHPC structures is lacking. Thus, this study proposes a two-dimensional fixed crack constitutive model for UHPC using the MSC.MARC software based on the experimental results, which is expected to offer high reliability. The stirrup restraint effect, tensile strength hardening, stiffness degradation, and the tension–compression softening of UHPC were considered in the constitutive model. To calibrate the relevant parameters of the constitutive model, UHPC prism and dog-bone specimens with different steel fibre contents were fabricated. Through uniaxial compressive and tensile tests with different loading regimes, the effects of steel fibre content, maintenance mode, and the loading regime on the uniaxial mechanical properties of UHPC were analysed. The test results showed that the peak compressive strain of the specimen with 2% steel fibre content was significantly higher than those of the specimens with 1% and 3% steel fibre content. Furthermore, UHPC exhibits strain hardening and ductility in the tensile experiments. The steel fibre content and steam curing significantly improved the tensile strength of the UHPC specimens. Based on the test data, the skeleton curves and hysteresis criteria of UHPC under compression and tension were proposed, and the formulae describing the process of unloading and reloading, which can be used for the basic constitutive model of UHPC, were fitted. Finally, five UHPC shear wall specimens were designed and simulated through the proposed model. The numerical results obtained using the proposed constitutive model and modelling methodology, including the skeleton curves, failure modes, ductility, and the deformation capacity of the UHPC shear walls, agreed significantly with the experimental results, confirming the reliability and high accuracy of the proposed UHPC constitutive model, thereby increasing the applicability of UHPC.

Hierarchical gallium-modified ZSM-5@SBA-15 for the catalytic pyrolysis of biomass into hydrocarbons

The catalytic pyrolysis of biomass is a sustainable approach for biofuel production, contributing to replacing fossil resources with renewable resources. The ZSM-5 zeolite remains an attractive catalyst in the catalytic pyrolysis of biomass, and how to reduce the product diffusion resistance and regulate the surface acidity of ZSM-5 should be explored more deeply. Herein, a hierarchical gallium-modified ZSM-5@SBA-15 catalyst is fabricated through coating a mesoporous layered SBA-15 shell on a hollow ZSM-5 core with gallium modified on the surface, which is effective for increasing hydrocarbon production during the catalytic pyrolysis of biomass process. The synergistic effect of hollowness, mesoporosity, and activity in the hierarchical gallium-modified ZSM-5@SBA-15 catalysts is found to affect the yield and quality of bio-oil. Accordingly, the hierarchical gallium-modified ZSM-5@SBA-15 catalyst with 11 wt% Ga loading exhibits a superior deoxygenation ability, and the relative content of hydrocarbons in bio-oil reach to 49.76 area% which is much higher than that of ZSM-5 (35.30 area%). Furthermore, a possible catalytic pyrolysis mechanism of biomass was also proposed to clarify the potential application of hierarchical gallium-modified ZSM-5@SBA-15 catalysts.

Tunable Drug Release from Fused Deposition Modelling (FDM) 3D-Printed Tablets Fabricated Using a Novel Extrudable Polymer.

Three-dimensional (3D) printing is proving to be a pivotal technology for developing personalized dosage forms with bench to bedside feasibility. Fused deposition modelling (FDM) 3D printing has emerged as the most used technique wherein molten drug-loaded polymer filaments are deposited layer-by-layer to fabricate a predefined shape and internal geometry. However, for precise FDM 3D printing, it is imperative for the filaments to have peculiar mechanical/physicochemical properties, which the majority of the FDA/GRAS approved polymers lack. In the current study, a novel water-soluble polymer, Poly(2-ethyl-tetra-oxazoline) [PETOx] has been investigated as an extrudable and printable polymer with two different types of drug molecule—dextromethorphan hydrobromide (DXM) and hydrochlorothiazide (HCTZ). Hot-stage microscopy experiments of drug:polymer (1:1 w/w) and filaments were carried out at 25–275 °C. HCTZ-loaded filament showed higher toughness of 17 ± 3.25 × 106 J/m3 compared with DXM and drug-free filament. Moisture sorption and flexural analysis was performed to understand the correlation of mechanical properties and storage humidity to printability. Varying the number of outer perimeters of each layer (shell number) was observed to affect the drug release pattern from the printlets. The DXM one-shell printlet showed >80%, whereas the DXM five-shell printlet showed >60% of the drug release within 60 min. PETOx could prove to be a high-performance and versatile 3D printable polymer.

Flexural Modulus Enhancement and Minimization of Printing Time and Part Weight for PET-G, Using Taguchi-GRA-TOPSIS Techniques

Fused deposition modeling (FDM) is becoming the most promised additive manufacturing (AM) process in recent years due to the evident benefits, such as high design flexibility, low cost, friendly and economically use. The current study considers an optimization of four different FDM parameters varied in three levels, as layer thickness (0.17 mm, 0.25 mm and 0.33 mm), infill density (25, 50 and 75%), shell thickness (0.8 mm, 1.2 mm and 1.6 mm) and raster angle (0o, 30o and 60o) with an objective to reduce printing time, part weight and to enhance flexural modulus using Polyethylene Terepthalate - glycol modified (PET-G) material. Mono optimization of FDM input parameters has been done using signal to noise ratio method obtained from Taguchi�s L9Orthogonal Array (OA) and multi response optimization is applied through Grey Relational Analysis (GRA) and technique of order preference similar to ideal solution (TOPSIS) techniques. The response or its criteria weightages are calculated using Shanon�s entropy and CRITIC method which gives different weightages for the considered responses. Printing time ranks top with 37% from entropy method followed by flexural modulus with 36% and part weight ranks last with 28%. Flexural modulus ranks tops with 43% followed by part weight with 29% and printing time takes last position with 28% weightage.The ranking of alternatives from GRA- entropy and GRA- CRITIC methods are similar by recommending A1B1C1D1 (0.17 mm layer thickness, 25% infill density, 0.8 mm shell thickness and 0� raster angle) but TOPSIS-entropy and TOPSIS - CRITIC methods suggested different parameter combination A2B3C1D2 (0.25 mm layer thickness,75% infill density, 0.8 mm shell thickness and 30� raster angle). From all the four different methods adopted for optimization, the parameter setting obtained from level total suggests A2B1C1D2 (0.25 mm layer thickness, 25% infill density, 0.8mm shell thickness and 30� raster angle) and completely opposite to the ranking of alternatives. The carried - out confirmation trials carried out validated the optimized settings resulted from different methods. Infill density is found to be the most significant factor as compared to other input factors over the output assessed parameters.