Effect Of Composite Structure Research Articles

A physics-informed machine learning model for global-local stress prediction of open holes with finite-width effects in composite structures

Fast and accurate methods are required to predict stresses in the vicinity of open and closed holes in composite structures, especially in a global-local modelling context as applied during the design of airframe structures. Fast analytical solutions for infinite-width anisotropic plates with open holes do not consider finite-width effects. Heuristic methods and semi-analytical solutions can be used to towards addressing such effects. To improve the accuracy and speed of these respective methods, we use machine learning (ML) methods trained on high-fidelity finite element analyses to make finite-width corrections. However, such methods require large amounts of training data to reduce errors to satisfactory levels. Therefore, in this study, the fusion of analytical solutions with machine learning is performed. We develop an analytical solution-informed ML model that is as fast as an analytical solution and superior in accuracy to analytical solutions with heuristic finite-width scaling. Our informed ML model offers accuracies equal to analytical solutions for the infinite-width case, and it is capable for use in a global-local modelling context, under uniaxial and biaxial loading. Our informed ML model outperforms prediction accuracy across all cases compared to uninformed ML models and requires a significantly lower size training dataset size.

Effect of composite structure on titanium alloy for infrared antireflection performance

Infrared reconnaissance and detection systems pose a major threat to aerial targets, and improving the infrared antireflection of aircraft surfaces has become a key problem to be solved urgently. Most researchers have fabricated a single structure and achieved good infrared antireflection performance. However, a single structure's improvement of infrared antireflection performance is limited. Therefore, this study prepared a novel composite antireflective structure with slotted holes using FDTD simulation combined with femtosecond laser design to further improve the infrared anti-reflective performance. The results show that the antireflection performance of the simulated groove-hole composite structure is better than that of the individual groove and hole structures, and the nanoparticle structures can further improve the antireflection performance in the infrared region. The composite structure fabricated by femtosecond laser had an average infrared reflectance of about 7.8% in the range of 8–14 µm and hydrophobicity. After sandpaper abrasion and tape peeling tests, it still has good anti-reflective properties, indicating the structure has excellent resistance to impact and abrasion. The surface roughness of the micro-nano-composite structures made by a femtosecond laser is much higher, and they have not only the properties of geometrically trapped light, but also the resonance absorption and scattering of unexcited elements such as metal nanoparticles, which gives them excellent infrared antireflection properties.

Fabrication, sound absorption simulation and performance optimization of multi‐layer gradient fiber‐based composites

AbstractNoise reduction with materials of finite thickness has been a hot research topic. In this study, multi‐layer gradient fiber‐based composites integrating porous, resonant and damping structures were prepared for efficient sound absorption. Here, the effects of composite structure, fiber‐based thickness and micro‐perforated membrane fabric (MPMF) structure on the sound absorption of the composites were investigated. From the results, the sound absorption band of the composite can be effectively tuned by adjusting the structure of the MPMF or the thickness of the fiber‐based. In addition, the established acoustic model can accurately predict the sound absorption performance of the structure. It is worth mentioning that the gradient structure optimized by the algorithm exhibits broadband sound absorption (noise reduction coefficient of 0.42) and thin feature (thickness of 0.9 cm). Moreover, the medium and low frequency sound waves can be propagated and absorbed more easily by optimizing the structure of the composite. This work provides a reference for the preparation of multi‐layer gradient sound‐absorbing structures and the design of acoustic products in a specific frequency range.

Modeling of Magnetoelectric Effects in Composite Structures by FEM–BEM Coupling

In this paper, a coupling of the Finite Element Method (FEM) and the Boundary Element Method (BEM) is used to model the behavior of magnetoelectric effects in composite structures. This coupling of numerical methods makes it possible not to have to consider a free space domain, and thus to use a single mesh for the magnetic, mechanical and electrical problems. This results in a consequent reduction of the number of unknowns which is accompanied by shorter computation times compared to a classical FEM approach. A mixed magnetic vector potential, reduced magnetic scalar potential formulation is used for the magnetic problem, and classical FEM formulations are used for electrical and mechanical problems. The resulting global algebraic system is solved by a block Gauss-Seidel solver.

A FEM-BEM coupling strategy for the modeling of magnetoelectric effects in composite structures

This paper deals with the numerical modeling of devices based on magnetoelectric composite materials. These heterogeneous structures made of the mechanical association of piezoelectric and magnetostrictive materials display magneto-electric effects exceeding by several orders of magnitude the response of single-phase multiferroic materials. A coupling of the Finite Element Method (FEM) and the Boundary Element Method (BEM) is used to model the behavior of magnetic effects, while classical FEM formulations are used for the electrical and mechanical problems. This coupling of numerical methods allows avoiding considering a free space domain around the active domain, and thus to use a single mesh for the magnetic, mechanical and electrical problems. This results in a consequent reduction of the number of unknowns, which is accompanied by shorter computation times compared to a pure FEM approach. The final system of equations is solved by a block Gauss–Seidel type solver.

Методы увеличения магнитоэлектрического эффекта в композитных структурах: обзор

The article provides a review of various methods that can be used to increase the magnetoelectric (ME) effect in composite structures based on magnetostrictive and piezoelectric materials. It is shown that the use of adhesive technology and gradient structure, as well as thermal and thermomagnetic treatment of a magnetostrictive amorphous alloy of an ME structure make it possible to achieve a significant increase in the ME effect. To date, great efforts have been made to optimize the strain amplitude in the piezoelectric and magnetostrictive phases of multilayer ME materials. The use of various technologies in the manufacture of ME composites makes it possible, for example, to increase the sensitivity of magnetic field sensors for biomedical applications. Also, an increase in the ME effect opens up great prospects for further research.

Comprehensive noise reduction performance of polyurethane/ferroferric oxide/activated carbon fiber felt coated flexible composites

Aiming at poor noise reduction performance of light and thin fiber aggregate materials, the polyurethane/ferroferric oxide/activated carbon fiber felt coated flexible composite materials were prepared by coating composite method. The effects of composite structure, ferroferric oxide particle content (10–25%), and coating thickness (0.25–1 mm) on the composites' sound absorption and sound insulation properties were systematically studied. The results show that with the increase of coating thickness and ferroferric oxide particle content, the sound absorption curve of the composite obviously moves to low frequency, and the resonance frequency decreases. When the particle content increased from 0% to 20%, the resonance frequency shifted 967 Hz. When the ferroferric oxide content is 25%, the maximum sound absorption coefficient and maximum transmission loss of the composite are 3.5 times and 25 times of that of the fiber felt, respectively. When the polyurethane/ferroferric oxide film thickness is only 0.1 mm, the maximum sound absorption coefficient and the average sound absorption coefficient of the composite are 3.5 times and 2.3 times of those of activated carbon fiber felt, respectively. Compared with single fiber felt, the composite material has better sound absorption, sound insulation, and mechanical properties while maintaining the thin and soft characteristics of the fiber felt.

Towards Fabrication of Planar Magnetoelectric Devices: Coil-Free Excitation of Ferromagnet-Piezoelectric Heterostructures

Magnetoelectric (ME) effects in composite ferromagnet-piezoelectric (FM/PE) heterostructures realize the mutual transformation of alternating magnetic and electric fields, and are used to create magnetic field sensors, actuators, inductors, gyrators, and transformers. The ME effect in composite structures is excited by an alternating magnetic field, which is created using volumetric electromagnetic coils. The coil increases the size, limits the operating frequencies, and complicates the manufacture of devices. In this work, we propose to excite the ME effect in composite heterostructures using a new coil-free excitation system, similar to a “magnetic capacitor”. The system consists of parallel electrodes integrated into the heterostructure, through which an alternating current flows. Modeling and measurements have shown that the excitation magnetic field is localized mainly between the electrodes of the magnetic capacitor and has a fairly uniform spatial distribution. Monolithic FM/PE heterostructures of various designs with FM layers of amorphous Metglas alloy or nickel-zinc ferrite and PE layers of lead zirconate titanate piezoceramic were fabricated and investigated. The magnitude of the ME effect in such structures is comparable to the magnitude of the ME effect in structures excited by volumetric coils. However, the low impedance of the coil-free excitation system makes it possible to increase the operating frequency, reducing the size of ME devices and the power consumption. The use of coil-free excitation opens up the possibility of creating planar ME devices, and accelerates their integration into modern electronics and microsystem technology.

Resonant optical effects in composite Co/opal-based magnetoplasmonic structures.

Plasmonic structures are extremely attractive for the light flow manipulation. In turn, the spectrum of the plasmon excitations can be controlled by external magnetic field, thus giving rise to magnetoplasmonics. However, in the case of traditional magnetoplasmonic structures, the enhancement of magneto-optical (MO) effects is often accompanied by the transmission damp, which constricts the area of their applications. This paper examines resonant optical effects in composite structures based on artificial opal films covered by a thin cobalt layer, which forms a 2D hexagonal lattice of nanoholes in the metal film. Such periodic structure exhibits surface plasmon polariton-assisted extraordinary transmission along with the increase of odd in magnetization intensity magnetooptical effect in the Voigt geometry. Local field enhancement accompanying the surface plasmon polaritons excitation in composite Co/opal structure provides a distinct enhancement of the magnetization-induced second harmonic generation (SHG) and relevant MO effects at the SHG wavelength that appear as Fano-type resonances. High transmission along with resonantly-high MO effects make Co/opal films promising in plasmonic applications.

Natural fibre thermoplastic tapes to enhance reinforcing effects in composite structures

Semi-consolidated thermoplastic tapes were produced by spreading flax and polypropylene matrix fibres using a newly developed technology. This lightweight tape was structurally stable and contained 38% flax fibres by volume. The tapes were processed in unidirectional and woven fabric format for composite fabrication. We found that the flax/PP tape-based composites had 60–110% higher flexural modulus and 35–65% higher tensile modulus compared to flax/PP yarn based thermoplastics. Thermoanalytical results showed that the heating conditions used in the tape-making process did not degrade the flax fibres and PP matrix. We conclude that such semi-consolidated flax/PP tapes enable the achievement of properties not seen before for yarn-based composites, and therefore are an important step forward in optimising the reinforcing effect of natural fibres in composite applications.

Controlling the Characteristics of the Magnetoelectric Effect in Composite Resonators through External Actions

The possibility of controlling the characteristics of the low-frequency resonant magnetoelectric effect in composite structures using external effects is demonstrated. These composite structures contain ganged ferromagnetic and piezoelectric layers. The magnitude of the magnetoelectric effect in planar structures with layers of nickel and lead zirconate titanate changes by tens of percent, and the frequency of acoustic resonance is altered to ten percent under the action of a constant magnetic field or a constant electric field when the temperature changes or mechanical stresses are created in the structure.

Effect of composite structure on capacity instability of SnO2-Coated multiwalled carbon nanotube composite anode

In this study, a multiwalled carbon nanotube (MWCNT) composite anode with SnO2 coated on the inner and outer surfaces of the surface-treated MWCNT was fabricated using a simple wet synthesis method. According to the X-ray diffraction and transmission electron microscope diffraction patterns, the SnO2 particles on the inner and outer surfaces of the MWCNT were a mixture of crystalline and amorphous phases. The peak separation of X-ray photoelectron spectra showed that 93.17 wt % Sn4+ and 6.83 wt % Sn2+ coexist, indicating that the Sn compound in the synthesized composites was composed of SnO2 and SnO. The cycle voltage profile showed a typical SnO2 oxidation/reduction reaction and reversible Sn-Li alloying and de-alloying reactions. Although the Sn compounds have a high Li-charging capacity, the capacity of the prepared composite anode decreased rapidly after several cycles. In addition, a repeated decreasing/increasing behavior of the capacity was observed after 20 cycles of charge/discharge. This rapid decrease and repeated capacity increase/decrease behaviors are attributed to the formation of coarse Sn particles through the re-agglomeration on the surface of MWCNT after grinding because of their charging and discharging. These results suggest that it is very important to avoid the presence of Sn compounds on the surface of MWCNTs when preparing a composite anode of Sn compounds and MWCNT as a power source for wearable devices.

Electrical field control of magnetoelectric effect in composite structures with single crystal piezoelectrics

The influence of constant electric field on the characteristics of the direct magnetoelectric effect in composite structures with single crystal piezoelectric layers was observed. The effect was measured in the structures with langatate and catangasite piezoelectric layers and amorphous magnetic alloy metglas as a ferromagnetic layer. The value of magnetoelectric voltage coefficient of 146 V/(Oe·cm) was obtained for the langatate-based structure and value of 1.35 V/(Oe·cm) for the catangasite-based structure. For the langatate-metglas structure, electrical field of 20 kV/cm resulted in a change in the generated voltage up to 63%, in the quality factor Q up to 76%, and provided linear variation of the resonance frequency up to 16 Hz. Electrical field control of magnetoelectric effect characteristics can be used to design new magnetoelectric devices.

PEG-PE/clay composite carriers for doxorubicin: Effect of composite structure on release, cell interaction and cytotoxicity.

DOX PEG-PE/clay formulations were design as an efficient drug delivery system. The main aim was to develop PEG-PE/clay formulations of different structures based on various PEG-PE/clay ratios in order to achieve tunable release rates, to control the external surface characteristics and formulation stability. The formulations showed significantly higher toxicity in comparison to "free" DOX, explained by formulation internalization. For each cell line tested, sensitive and ADR resistant, a different formulation structure was found most efficient. The potential of PEG-PE/clay-DOX formulations to improve DOX administration efficacy was demonstrated and should be further explored and implemented for other cancer drugs and cells.

Correlation Between Magnetoelectric and Magnetic Properties of Ferromagnetic–Piezoelectric Structures

The magnetoelectric (ME) effect in composite structures consisting of ferromagnetic (FM) and piezoelectric (PE) layers arises due to combination of magnetostriction and piezoelectricity by means of mechanical coupling between the layers [1]. The structures generate ac voltage u being placed in an external dc bias magnetic field H and ac magnetic field h. Amplitude of the voltage is u ∼qd 31 h, where q = dλ/dH is the piezomagnetic coefficient and λ(H) in the magnetostriction of the FM layer, d 31 is the piezoelectric module of the PE layer, and h is the field amplitude. It has been shown that the magnetostriction is related to the FM layer magnetization as λ ∼ M 2. It follows, that field dependence of the ME voltage u(H) can be explained or predicted by measuring the field dependence of magnetization M(H). The aim of the present work is to demonstrate a correlation between magnetoelectric and magnetic properties of the FM-PE composite structures.

Regulation Mechanism of Novel Thermomechanical Treatment for Microstructure and Properties of 2E12 Aluminum Alloy

Abstract The effects of a novel thermo-mechanical treatment (TMT) on the mechanical properties and the microstructure of 2E12 aluminum alloy were investigated by tensile test and fatigue crack propagation test, as well as scanning electron microscope and transmission electron microscope (TEM). Results show that a good combination of strength and plasticity can be achieved for 2E12 aluminum alloy by the new TMT, the yield strength increases by ∼28% over that of T3, and the ultimate tensile strength also increases by 17%, while the high elongation of T3 condition (over 16%) is maintained. The fatigue crack growth rate of the TMT is lower than those of the T3 and T6 peak aged samples. A high density of tangled dislocation is contained in the TMT 2E12 aluminum alloy, and dislocation cell substructure is formed. The mechanism of the new TMT technique, by which the mechanical properties of the alloy is greatly increased, is the synergistic effect of composite structures, including dislocation cell substructures, the complex of Mg/Cu/vacancies, as well as GPB zones.

Preparation and magnetic properties of NiFe2O4–Fe2O3@SnO2 heterostructures

NiFe2O4–Fe2O3@SnO2 heterostructures were successfully synthesized by a multi-step method using nonstoichiometric Ni ferrite as a precursor. Through adjusting the sequence of solvothermal treatment and thermal calcination, core–shell and yolk–shell NiFe2O4–Fe2O3@SnO2 porous spheres can be obtained. Using NiFe2O4–Fe2O3 composite as a core, NiFe2O4–Fe2O3@SnO2 core–shell spheres can be synthesized by the solvothermal growth of SnO2. NiFe2O4–Fe2O3@SnO2 yolk–shell spheres have been prepared by using nonstoichiometric Ni ferrite as a core followed by the solvothermal growth of SnO2 and thermal calcination. The effects of composite structure and composition on magnetic properties were investigated. Because of subsequent deposition of SnO2, magnetization saturation of NiFe2O4–Fe2O3 porous spheres is higher than that of NiFe2O4–Fe2O3@SnO2. Magnetization saturation of core–shell NiFe2O4–Fe2O3@SnO2 composite is higher than that of yolk–shell NiFe2O4–Fe2O3@SnO2 composite.

Graphene reinforced nanocomposites: 3D simulation of damage and fracture

3D computational model of graphene reinforced polymer composites is developed and applied to the analysis of damage and fracture mechanisms in the composites. The graphene/polymer interface properties are determined using the inverse modeling approach. The effect of composite structure, in particular, of the aspect ratio, shape, clustering, orientation and volume fraction of graphene platelets on the mechanical behavior and damage mechanisms of nanocomposites are studied in computational experiments. It was shown that the Young modulus of the nanocomposites increases with increasing aspect ratio, volume content, elastic properties of graphene/polymer interface layer, and decreasing the degree of intercalation. The tensile strength follows similar tendencies, except for the aspect ratio and clustering degree, where the opposite effects are observed. Nanocomposites with randomly oriented sheets of graphene demonstrate much lower Young modulus and strength as compared with the composites with the aligned graphene sheet reinforcement. It was further concluded that the structural imperfections of graphene reinforcement (like crumpling shape or random misalignment) have considerable effect on the composite performances.

Numerical Analysis on Protective Effectiveness of Composite Blast Walls against Blast Wave

For the comparative analysis of composite blast walls on the protective effects of blast wave, Overpressure protective effectiveness coefficient was put forward to analyze protective effectiveness and . It was studied that Protective effectiveness of composite blast walls under blast waves using 3D numerical simulation method and analysis of the amount of drugs, explosive distance, height and other structural parameters on protective effect of composite structures. The influence of several factors on forecasting formula was analyzed, such as scaled blast distance and scaled height of wall. Via fitting the simulation results overpressure formula of the back of composite blast walls was obtained. The result indicate that protective effectiveness of composite structure increases when walls height increases or scaled blast distance decreases.

Experimental identification of smart material coupling effects in composite structures

Smart composite structures have an enormous potential for industrial applications, in terms of mass reduction, high material resistance and flexibility. The correct characterization of these complex structures is essential for active vibration control or structural health monitoring applications. The identification process generally calls for the determination of a generalized electromechanical coupling coefficient. As this process can in practice be difficult to implement, an original approach, presented in this paper, has been developed for the identification of the coupling effects of a smart material used in a composite curved beam. The accuracy of the proposed identification technique is tested by applying active modal control to the beam, using a reduced model based on this identification. The studied structure was as close to reality as possible, and made use of integrated transducers, low-cost sensors, clamped boundary conditions and substantial, complex excitation sources. PVDF (polyvinylidene fluoride) and MFC (macrofiber composite) transducers were integrated into the composite structure, to ensure their protection from environmental damage. The experimental identification described here was based on a curve fitting approach combined with the reduced model. It allowed a reliable, powerful modal control system to be built, controlling two modes of the structure. A linear quadratic Gaussian algorithm was used to determine the modal controller–observer gains. The selected modes were found to have an attenuation as strong as −13 dB in experiments, revealing the effectiveness of this method. In this study a generalized approach is proposed, which can be extended to most complex or composite industrial structures when they are subjected to vibration.