Multilayered Plates Research Articles

Static response of functionally graded multilayered two-dimensional quasicrystal plates with mixed boundary conditions

Static response of functionally graded multilayered two-dimensional quasicrystal plates with mixed boundary conditions

Kevlar fabric reinforced polybenzoxazine composites filled with silane treated microcrystalline cellulose in the interlayers: The next generation of multi-layered armor panels

The design of astonishing combinations of benzoxazine resins with various fillers is nowadays of great interest for high quality products, especially in ballistic armors. The objective of this study is to investigate a new hybrid material prepared as multi-layered composite plate by hand lay-up technique. Different composites were manufactured from Kevlar fabrics reinforced polybenzoxazine, which was filled with silane treated microcrystalline cellulose (MCC Si) at various amounts in the interlayers. The developed materials were tested for their flexural, dynamic mechanical and ballistic performance. The aim was to highlight the effect of adding different amounts of MCC Si on the behavior of the different plates. Compared to the baseline, the dynamic mechanical and bending tests revealed an obvious decrease of the glass transition of 21 °C and a notable increase in storage modulus and flexural strength of about 180 %and17%, respectively, upon adding 1% MMC Si as filler. Similarly, the ballistic test exhibited an enhancement in kinetic energy absorption for which the composite supplemented with 1% MCC Si had the maximal energy absorption of 166.60 J. These results indicated that the developed panels, with interesting mechanical and ballistic features, are suitable to be employed as raw materials to produce body armor.

Research progress of target resistance model of cavity expansion theory and its application

The cavity expansion theory is one of the main basic theories for the theoretical analysis of penetration problems. It is mainly used to analyze the failure response characteristics of typical target materials under impact load, and then to determine the penetration resistance of the target. It is widely used in the analysis of high-speed impact penetration and failure problems. Domestic and foreign scholars have made abundant research achievements on plastic and (quasi) brittle materials based on the theory of cylindrical and spherical cavity expansion. Starting from the theoretical system of the static/dynamic cavity expansion model, the results of the cavity expansion model in different directions are introduced, mainly involving the cavity expansion pressure theoretical calculation model and numerical simulation method under ideal penetration conditions, and the application of cavity expansion model to typical penetration problems and complex missile target conditions. The theoretical calculation model under ideal penetration conditions based on cavity expansion theory mainly discusses the influence aspects of target material, yield criterion and equation of state on target resistance and the applicability of the cavity expansion model. According to the different initial conditions in the numerical simulation, two numerical simulation methods of cavity surface constant velocity/constant pressure are introduced, and the reliability of the numerical simulation method is proved. The basic assumptions, application scope and engineering application characteristics of the cavity expansion model are summarized, and its applications in typical penetration problems and complex missile targets such as multilayer composite target plate, constrained target, projectile grooves and projectile body with special cross-section are listed. Based on the current status of the cavity expansion model, we summarized the current cavity expansion model application direction in the field of impact dynamics, and the problems existing in the application of the cavity expansion model, as well as the key development direction in the cavity expansion model.

Nondestructive evaluation of adhesively bonded plate-like structures through local wavenumber estimation

Nondestructive testing (NDT) of adhesively bonded plate-like structures using traditional ultrasonic (US) testing modalities can be challenging and time-consuming. Faster inspection can be achieved with the use of full-field techniques based on guided waves. In particular, the local wavenumber estimation (LWE) of Lamb waves has been proven effective for damage detection in various plate-like structures. However, the effectiveness of LWE depends on multiple parameters, such as the excitation frequency, the choice of a Lamb wave mode, or the inspection side, among others. This is especially significant in the case of multilayer plates, where different types of damage result in a nontrivial behavior of Lamb waves. In this work, we present a framework for the evaluation of disbonds in adhesively bonded multilayer plates through local wavenumber estimation. We demonstrate theoretically and experimentally that the proposed methodology allows obtaining clear images of defects and determining their through-thickness locations in multilayer plate-like structures.

Thermo-mechanical stability analysis of angle-ply plates using meshless method

Present paper deals with the investigation of stability under thermo-mechanical inplane loadings of a multilayered angle-ply rectangular plate utilizing Meshless method. A new Higher-order hypothesis is used in displacement fields to acquire the differential equations of the plate. These equtations are descritized with radial basis function (RBF) based meshless method. A MATLAB code is created to acquire the solutions and mode shapes. Convergence study has been led to check the current problem adequacy. Parametric examination is directed for buckling behaviour under the span to-thickness proportion, cover plot, impact of the number of layers and impact of length to width proportion. New results for rectangular plates made up of angle-ply overlay is presented.

A five-variable model and experiments for dynamic analysis of sandwich plates with holes

Due to their simplification and efficiency, five-variable higher-order models have been widely developed for static and dynamic analysis of multilayered composite and sandwich plates. Nevertheless, the existing five-variable higher-order models will encounter difficulty to produce accurately natural frequencies of sandwich plates. Thereby, this paper proposes a five-variable sine-type higher-order model, which can predict reasonably natural frequencies of sandwich plates. To broaden the scope of application, the finite element formulation in the light of the proposed model is presented. In order to verify the reliability of the proposed model, experiments including two groups of samples have been carried out to test natural frequencies of sandwich plates with diverse holes. After the proposed model is evaluated by experiments, natural frequencies of sandwich plates with different boundary conditions and cutout shapes have been investigated in detail by utilizing the proposed model, which will be further assessed by employing the three-dimensional finite element method (3D-FEM). In addition, the typical five-variable higher-order models published from 1980s to 2020s have been also selected to assess the proposed model. Numerical results show that the proposed model can yield more accurate results than the previous five-variable models. Furthermore, variation of natural frequencies of sandwich plates is also explored by changing the material properties of face sheets, which can provide a consultation for design of dynamic characteristics of sandwich plates.

Investigation of the effect of cutout shape on thermal stresses in perforated multilayer composites subjected to heat flux using an analytical method

In the engineering design of perforated composite laminates, understanding the effect of geometrical and material parameters on stress concentration is of vital importance. In this paper, the effect of the cutout shape on the thermal stresses induced in perforated multilayer composite plates under uniform heat flux was studied. The thermal stress concentration was investigated using an analytical method based on the two-dimensional thermo-elastic theory, the Lekhnitskii method and conformal mapping by varying the laminate material and the aspect ratio, the bluntness and the rotation angle of the 3- to 6-sided polygonal cutouts. It was found out that the desirable cutout angular position for which the minimum thermal stress concentration was obtained was dependent on the order of the polygonal cutout, whereas the desirable cutout aspect ratio was unity irrespective of the cutout shape. The analytical results were in a reasonable correlation with the finite element results.

Analysis of guided wave propagation in functionally graded magneto-electro elastic composite

In the present work, the general stiffness matrix method is extended in the case of a functionally graded magneto-electro-elastic plate to analyze the free vibration response of a functionally graded composite plate. The material properties are assumed to be continuously graded in the thickness direction. The novelty of this paper is to utilize this efficient method to the dynamic analysis of a wide range of composite (multilayer) plates, with linear or non-linear thickness profiles, and functionally graded in the thickness, without any limitation. The convergence of this method is thoroughly discussed. Here, the converged results are obtained when the number of sub-layer is N ≤ 11 . A parametric study was also conducted to show the effect of gradation of mechanical properties of the composite on the phase velocity and the modal shape. The dynamic model developed here can be used in the graded material design of the functionally graded piezoelectric-piezomagnetic (noted FGPPM) composite plate for achieving specified dynamic characteristics.

Identification of Magnetorheological Layer Properties by Using Refined Plate Theory

In this paper, the dynamic characteristics of sandwich plates with external rigid layers and an upper layer with magnetorheological properties (MR) are investigated. An analysis of the effect of the magnetic field on frequency and loss factor is presented. Vibration can be controlled by a magnetic-rheological viscoelastomer (MRVE), when used in sandwich plates. During vibration, MRVE exhibits an inhomogeneous complex module, which is controlled by an applied magnetic field and depends on the oscillation frequency. Using the dynamic equilibrium conditions, physical and kinematic relationships, and the partial differential equations for the conjugate transverse and longitudinal oscillations of a sandwich plate, are derived. This paper presents a new method for stress analysis that provides accurate stress distributions for multilayer plates subject to cylindrical bending. It uses an adaptive method that does not make strict assumptions about the plate model. Based on the depicted theoretical model, the deformations of each layer of the plate are accounted for, including both transverse shear deformations and transverse normal deformations where the thickness is concerned, and nonlinear displacement changes. The magnetorheological (MR) identification of an inner layer is carried out using refined plate theory and sandwich bending tests. Using combined methods, the possibility of determining the MRVE parameters robustly, is examined.

Optimization design and simulation of a light broadband multilayer composite absorber

A multilayer plate structure is an effective way to design an absorbing coating with excellent performance. Based on the analysis of the electromagnetic (EM) absorption principle of multilayer structures, this paper selects magnetic loss and resistance loss type materials to establish a database of EM parameters. A genetic algorithm is used to optimize the design of the multilayer structure. Finally, COMSOL Multiphysics and the finite element method (FEM) are used for simulation verification. The results show that the multilayer materials prepared by different types of EM loss materials have a large absorption bandwidth and strong absorption capacity. When optimizing for different frequency bands with a thickness limited to 5 mm, the absorption band can be adjusted freely between 5 and 15 GHz by selecting the materials and thickness of each layer, which solves the limitation of a single material that only meets the requirements in a specific frequency band. When optimizing for absorption intensity, the minimum reflection loss (RLmin) can reach −30.7 dB and an effective absorption bandwidth (EAB) of 3.3 GHz (13.1–16.4 GHz) is achieved with only 2.44 mm. This design method provides the possibility to design multilayer composite materials with high absorption and low reflection in a wider frequency band range.

A Mating Procedure for Genetic Transfer of Integrative and Conjugative Elements (ICEs) of Streptococci and Enterococci.

DNA sequencing of whole bacterial genomes has revealed that the entire set of mobile genes (mobilome) represents as much as 25% of the bacterial genome. Despite the huge availability of sequence data, the functional analysis of the mobile genetic elements (MGEs) is rarely reported. Therefore, established laboratory protocols are needed to investigate the biology of this important part of the bacterial genome. Conjugation is a mechanism of horizontal gene transfer which allows the exchange of MGEs among strains of the same or different bacterial species. In streptococci and enterococci, integrative and conjugative elements (ICEs) represent a large part of the mobilome. Here, we describe an efficient and easy-to-perform plate mating protocol for in vitro conjugative transfer of ICEs in streptococci (Streptococcus pneumoniae, Streptococcus agalactiae, Streptococcus gordonii, Streptococcus pyogenes), Enterococcus faecalis, and Bacillus subtilis. Conjugative transfer is carried out on solid media and selection of transconjugants is performed with a multilayer plating. This protocol allows the transfer of large genetic elements with a size up to 81 kb, and a transfer frequency up to 6.7 × 10−3 transconjugants/donor cells.

The effect of the addition of nanopowders on the strength of multilayer composite materials

Modification of polymers with fillers provides the possibility of changing their physical and mechanical properties. The goal of the study is a comprehensive analysis of the effect of nanodispersed additives and other powdery substances on the strength of multilayer composite materials (CM). A series of multilayer composite specimens based on fiberglass and carbon fabric was made with the addition of fillers in a concentration of 1 and 3 wt.% to an epoxy polymer matrix. Nanopowders of silicon dioxide Tarkosil (T20, T50, T80, T110), fine powders of copper, collagen and cellulose fibers were used as fillers. Two types of tests, i.e., for compression and for impact were carried out. The introduction of nanopowders into CM changes their strength properties: the samples added with T110 nanomaterial withstand the maximum compressive load at a concentration of 1 and 3 wt.%. The results of impact tests of the samples with fillers and computer simulation of the impact and punching of the samples using the ANSYS/LS-DYNA software product, are presented. A method for numerical simulation of the impact process has been developed, which provides studying the dynamics of deformation and fracture of multilayer samples. Impact tests of the samples carried out at different values of the impact velocity (from 380 to 450 m/sec) revealed either puncture of the CM plates or damage such as delamination and splitting. In the impact test of multilayer specimens of composite materials with fillers added to the epoxy polymer matrix, the interlayer defects appeared in the form of delamination; samples without additives were pierced through under the impact. The experimental data on the degree of damage to multilayer plates after the impact matched the results of computer simulation.

Modeling of thermal stresses in thin-walled composite structures with phase transformation

An asymptotic theory modified version for calculating thin elastic multilayer plates made of high-temperature composites with multistage phase transformations, considering the composites shear characteristics finite values has been developed. Proposed in this work method version does not contain any assumptions about the kind of the unknown functions and allows ones to find all 6 stress tensor components while ensuring the high mathematical accuracy that symbolic for asymptotic method. Using the developed model, it became possible to calculate temperature non-stationary field and thermal stresses in thin multilayer plates of fabric composite materials on an inorganic binder. For material properties calculation were used multiscale averaging method and finite element modeling for periodical cells. Some change stresses numerical simulation results for composite plate during heating and loading are given.

A new analytical solution for elastic flexure of thick multi-layered composite hybrid plates resting on Winkler elastic foundation in air and water

A new analytical flexural solution based on double finite integral Fourier transform and trigonometric series differentiation procedures was developed for thick multi-layered composite hybrid rectangular plates resting on Winkler elastic foundation in air and water. The effect of material anisotropy, coupled hydro-mechanical loads, and underwater floor inclination angle,which were overlooked in the literature, is considered in this study. Furthermore, the predetermination of the shape deformation function is not required in our proposed analytical solution, which offers more accurate results. For the particular cases where the plate made of isotropic material is in air, the analytical results are compared with, and verified by the literature. Literature is lacking to investigate thick multi-layered composite hybrid rectangular plates with free edges and under hydro-mechanical load; hence our analytical results are compared with, and verified by,numerical analysis employing finite element method (FEM). The analytical results provide excellent agreement with both literature and the proposed FEM. FEM is shown to be time-intensive since the results converge after 60 seconds runtime with definition of 12159 elements during mesh refinement, yet the proposed analytical method demonstrates that the convergence can easily be achieved after 5 seconds runtime through selecting small values for Fourier terms.

High Damping Passive Launch Vibration Isolation System Using Superelastic SMA with Multilayered Viscous Lamina

Whole-spacecraft launch-vibration isolation systems are attractive for achieving the goal of better, faster, cheaper, and lighter small satellites by reducing the design-load and vibration-test specifications for on-board components. In this study, a three-axis passive launch-vibration isolation system, based on superelastic shape memory alloy (SMA) technology, was developed to significantly attenuate the dynamic launch loads transmitted to a small satellite. This provides a superior damping characteristic, achieved by superelastic SMA blades stiffened by multilayered thin plates with viscous lamina adhesive layers of acrylic tape. The basic characteristics of the proposed isolation system with various numbers of viscoelastic multilayers were obtained through a static load test. In addition, the effectiveness of the design was validated through a launch environment simulating sine and random vibration tests.

Off-axis multilayer zone plate with 16 nm × 28 nm focus for high-resolution X-ray beam induced current imaging.

Using multilayer zone plates (MZPs) as two-dimensional optics, focal spot sizes of less than 10 nm can be achieved, as we show here with a focus of 8.4 nm × 9.6 nm, but the need for order-sorting apertures prohibits practical working distances. To overcome this issue, here an off-axis illumination of a circular MZP is introduced to trade off between working distance and focal spot size. By this, the working distance between order-sorting aperture and sample can be more than doubled. Exploiting a 2D focus of 16 nm × 28 nm, real-space 2D mapping of local electric fields and charge carrier recombination using X-ray beam induced current in a single InP nanowire is demonstrated. Simulations show that a dedicated off-axis MZP can reach sub-10 nm focusing combined with reasonable working distances and low background, which could be used for inoperando imaging of composition, carrier collection and strain in nanostructured devices.

Идентификация кристаллического продукта жидкофазного окисления α-пинена кислородом воздуха в присутствии стеарата кобальта (II)

One of the possible directions of liquid-phase oxidation of α-pinene by atmospheric oxygen leads to the formation of a mixture of terpene oxygen-containing compounds (epoxides, alcohols, ketones, etc.). The problem of this direction is the formation of a large amount of 2,3-epoxypinane which over time turns into trans-sobrerol, campholene aldehyde, trans-pinocarveol, trans-carveol, and trans-3-pinen-2-ol as a result of hydrolysis. One of the abovementioned substances with a solid crystalline structure is trans-sobrerol. Sobrerol is widely used in perfumery for synthesis of synthetically fragrant substances and pharmaceutical industry, in particular, it is a part of medicines with mucolytic action, as well as in the treatment of headaches and diseases such as rhinorrhea and chronic bronchitis. The aim of this work is to identify a crystalline product produced by liquid-phase oxidation of α-pinene with atmospheric oxygen in the presence of cobalt (II) stearate. The process of liquid-phase oxidation was carried out in the following conditions: temperature – 70 °С, air consumption – 16.67 cm3/s, duration – 5 h, amount of catalyst – 0.2–0.5 wt.%. Then the mixture was exposed to steam distillation in order to separate monomers (they contain terpene oxygen-containing compounds and hydrocarbons) from polymers. As a result of settling and storage of the mixture, crystals were found and isolated from the mother liquor solution. Their identification was carried out using IR and 13C NMR spectroscopy as well as scanning electron microscopy. It was found that the spatial organization of the isolated crystals and the standard sample (Sigma Aldrich) is represented by multilayer rectangular plates. Analysis of the IR spectra of the crystals showed that the absorption band at a wave number of 3318 cm–1 corresponds to intramolecular and intermolecular hydrogen bonds in hydroxyl groups, at wave numbers of 2887, 2935, 2975 cm–1 it corresponds to methyl groups. The results obtained are comparable with the results of the IR-spectrum of the standard sample. Given the results of previous studies of 1H NMR spectrum [15] and 13C NMR spectrum, it was determined that the resulting crystalline product of liquid-phase oxidation of α-pinene is trans-sobrerol.

Dichotomy property of dispersion equation of guided waves propagating in anisotropic composite plates

Accurate prediction of dispersion curves for ultrasonic guided waves propagation in multi-layered composite laminates is crucial for the deployment of nondestructive testing procedures and structural health monitoring algorithms dedicated to aerospace composite materials. However, existing efforts mainly focused on finding ways to build complex-valued dispersion equations for guided waves (see transfer matrix method (TMM), global matrix method (GMM) and stiffness matrix method (SMM) for example) with little focus on developing efficient and stable numerical solving methods associated with the derived complex-valued equations. In this paper, the conditions under which complex-valued dispersion equations are either real- or purely imaginary-valued equations (termed as dichotomy property) are derived for both single- and multi-layered composite plates. With such a property, the complex-valued dispersion equations can be efficiently numerically solved within the real number field via the standard bisection method or the corrected phase change method. It is thus now possible to overcome numerical issues frequently reported in literature. Besides, a parallel computing technique is proposed in this paper to improve the computational efficiency of the traditional GMM. The proposed methodology provides a new standard framework to solve the dispersion equations which is stable, multipurpose, and numerically efficient.

Multi-layered parallel plate waveguide with electrically and magnetically biased graphene sheets

The performance of a multi-layered parallel plate waveguide, supported by graphene plates, is evaluated here. The graphene layers were biased with both magnetic and electric fields. The graphene plates weremodelled as an anisotropic surface derived from the Kubo formula. Maxwell's equations were solved for these waveguides; and it is shown when both magnetic and electric biases were applied to the graphene, hybrid modes propagated inside the waveguides. The intensity of each TM and TE mode could be adjusted with an applied external field bias. This study of wave confinement has shown that, by varying the bias, full control can be exerted over the wave's propagation within a waveguide; whereby, increasing the bias causes added phase changes over the propagation length, while increasing the waveguide's attenuation. It must be emphasized that the presented procedure is also applicable to other guiding structures that have boundary with isotropic or anisotropic conductivities.

Static response and free vibration analysis for cubic quasicrystal laminates with imperfect interfaces

Quasicrystals have attracted the tremendous attention of researchers for their unusual properties. In this paper, an analytical treatment is presented for the static response and free vibration of a multilayered three-dimensional, cubic quasicrystal rectangular simply supported plate with bonding imperfections. Based on the basic elasticity equation of three-dimensional quasicrystals, we construct the linear eigenvalue system in terms of the pseudo-Stroh formalism, from which the general solutions of the extended displacements and stresses in any homogeneous layer can be obtained. Furthermore, these solutions along the thickness direction can be utilized to solve any physical variables under given boundary conditions. For multilayered plates, the propagator matrices are employed to connect the field variables at the upper interface to those at the lower interface of each layer. The special spring model, which describes the discontinuity of the physical quantities across the interface, is introduced into the overall propagator relationship of the structure. Compared with the conventional propagator matrix method, a new propagator relation is established to resolve numerical instabilities of the case of large aspect ratio and high-order frequencies for QC laminates with imperfect interface. In addition, the traction-free boundary condition on the top and bottom surfaces of the layered plate is considered to investigate the free vibration characteristics of the laminates. Finally, typical numerical examples are presented to illustrate the influence of imperfect interfaces on static response and free vibration of cubic quasicrystal plates.