Properties Of Composite Structures Research Articles

Effects of Different Interface Forms on Mechanical Properties of Steel Self‐Compacting Concrete Composite Beams

In the water resources allocation project in Pearl River Delta, in order to optimize the structural design, the deep buried tunnel adopts the composite lining structure. However, the weakest link in a complex structure is the connection between two different interfaces. This paper reports the findings of an experimental study that was undertaken to investigate the interface mechanical performance of steel self‐compacting concrete composite structure subjected to cyclic loads. In this study, different shear connectors are considered, and six different specimens were designed and tested, respectively. The test is used to research the effect of the different shear connectors on the bearing capacity and interface mechanical properties of composite structure in an experimental study. According to these test results, a detailed analysis was carried out on the relationships, such as the stress‐strain and load‐displacement relationships for the specimen. These tests show that the shear connectors will significantly enhance the bearing capacity and interface mechanical properties of the composite structure. Among them, the comprehensive performance of the specimens using the stud‐longitudinal ribs shear connectors is the best. Additionally, a finite element analysis (FEA) model was developed. The comparison of the simulation results with the experimental results shows that this FEA is applicable for this type of experiment.

Temperature Effect on Mechanical Properties of Top Neck Mollusk Shells Nano-Composite by Molecular Dynamics Simulations and Nano-Indentation Experiments

Discovering the mechanical properties of biological composite structures at the Nano-scale is much interesting today. Top Neck mollusk shells are amongst biomaterials Nano-Composite that their layered structures are composed of organic and inorganic materials. Since the Nano indentation process is known as an efficient method to determine mechanical properties like elastic modulus and hardness in small-scale, so, due to some limitation of considering all peripheral parameters; particular simulations of temperature effect on the atomic scale are considerable. The present paper provides a molecular dynamics approach for modeling the Nano-Indentation mechanism with three types of pyramids, cubic and spherical indenters at different temperatures of 173, 273, 300 and 373K. Based on load-indentation depth diagrams and Oliver-Far equations, the findings of the study indicate that results in the weakening bond among the bilateral atoms lead to reduced corresponding harnesses. Whenever, the temperature increases the elastic modulus decrease as well as the related hardness. Moreover, within determining the elastic modulus and hardness, the results obtained from the spherical indenter will have the better consistency with experimental data. This study can be regarded as a novel benchmark study for further researches which tend to consider structural responses of the various Bio-inspired Nano-Composites.

Transferability of interatomic potentials with insights into the structure–property relationship of SiO2–CaO–MgO–Al2O3 melts

ABSTRACTMolecular dynamics (MD) simulations were carried out to validate the transferability of Matsui, Kawamura, Miyake, and Guillot potentials on the composition–structure–property relationship of liquid SiO2–CaO–MgO–Al2O3 (CMAS) melts in a wide range of chemical compositions at 1773K. Results revealed that Matsui, Miyake, and Guillot potentials were able to reproduce experimentally observed local atomic structures and properties while Kawamura potential cannot. Even though an accurate trend can be obtained, the values of properties obtained with Miyake, Matsui and Guillot potentials varied obviously with each other. Viscosity obtained using Einstein–Stokes method is about one magnitude lower than experimental viscosity, while viscosities obtained with Green–Kubo and reverse nonequilibrium molecular dynamics methods underestimate the viscosity by about two magnitudes. The increase in CaO/SiO2 ratio under fixed MgO/Al2O3 ratio and the increase in MgO/Al2O3 ratio under fixed CaO/SiO2 ratio can both decrease the polymerisation degree of system, which finally decreases the viscosity. The influence of adding a Morse term to BMH potential is very slightly. This paper provides the foundation to further simulate the atomic structure of CMAS system and further optimise the Born–Mayer–Higgins potential for various oxide systems.

Crowd-sourcing materials-science challenges with the NOMAD 2018 Kaggle competition

A public data-analytics competition was organized by the Novel Materials Discovery (NOMAD) Centre of Excellence and hosted by the online platform Kaggle by using a dataset of 3,000 (AlxGayIn1–x–y)2O3 compounds. Its aim was to identify the best machine-learning (ML) model for the prediction of two key physical properties that are relevant for optoelectronic applications: the electronic bandgap energy and the crystalline formation energy. Here, we present a summary of the top-three ranked ML approaches. The first-place solution was based on a crystal-graph representation that is novel for the ML of properties of materials. The second-place model combined many candidate descriptors from a set of compositional, atomic-environment-based, and average structural properties with the light gradient-boosting machine regression model. The third-place model employed the smooth overlap of atomic position representation with a neural network. The Pearson correlation among the prediction errors of nine ML models (obtained by combining the top-three ranked representations with all three employed regression models) was examined by using the Pearson correlation to gain insight into whether the representation or the regression model determines the overall model performance. Ensembling relatively decorrelated models (based on the Pearson correlation) leads to an even higher prediction accuracy.

Bend-free design of ellipsoids of revolution using variable stiffness composites

Shells are commonly used in many structural applications due to their high specific load carrying capabilities. One of the most interesting features of shell structures is that they can resist external transverse loads by developing membrane stresses in the small deformation regime yet, in general, also generate inefficient bending deformations and stresses. In this study, a composite ellipsoid shell of revolution, under internal pressure, is designed for zero bending and curvature change. To this end, the stiffness properties of elliptical composite shell structures are tailored by fibre steering. A new definition for a bend-free state, independent of internal pressure, is presented. Based on this definition, the internal pressure-induced bending state of an isotropic ellipsoidal shell of revolution is compared with its tailored composite counterpart. Results show that up to a specific level of ellipticity, a bend-free state is achievable by fibre steering in elliptical composite shells of revolution. Finally, a failure study is performed to assess the potential improvement of the maximum allowable internal pressure by bend-free design.

One-step fabrication of SnO2 porous nanofiber gas sensors for sub-ppm H2S detection

SnO2 porous nanofibers (NFs) were deposited on-chip by using a facile electrospinning method followed by heat treatment at 600 °C and used to detect H2S concentrations at sub-parts per million level. Morphological, compositional, crystal, and atomic structural properties of the as-spun and calcined SnO2 NFs were investigated by field emission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy, respectively. SnO2 porous NFs with an average diameter of 150 nm and consisting of many nanograins were successfully fabricated by on-chip electrospinning. The NFs were crystallized as the tetragonal structure of SnO2 with an average crystallite size and dislocation density of approximately 13.5 nm and 5.615 × 1015 lines/m2, respectively. The sensing characteristics of the SnO2 NF sensors were tested with 0.1–1 ppm H2S from 150 °C to 450 °C. The sensor achieved the optimal performance at 350 °C and exhibited gas response of 15.2 with fast response/recovery times of 15 s/230 s. The H2S gas sensing mechanisms of the SnO2 porous NF sensors were due to the modulation of the resistance along the surface depletion layer and the grain boundaries. The fabricated sensor also indicated a good selectivity to H2S, short-term stability, and the low detection limit of 1.6 ppb. The influence of humidity on the sensor’s performance in a low temperature range is also discussed.

Enhancement of corrosion protection of low nickel austenitic stainless steel by electroactive polyimide-CuO composites coating in chloride environment

Purpose The purpose of this study is to improve the anticorrosion performance of low nickel stainless steel (AISI 201) in 3.5% NaCl by electroactive polyimide/copper oxide (EPI/CuO) composites coating. Design/methodology/approach Electroactive polyimide/copper oxide (EPI/CuO) composites were prepared by oxidative coupling polymerization followed by thermal imidization method. Findings The functional and structural properties of composites were characterized by X-ray diffraction, Fourier transmission infra-red and ultra violet-visible spectroscopy and the surface topography was characterized by field emission scanning electron microscope analysis and anticorrosion performance in 3.5 Wt.% NaCl was evaluated by electrochemical techniques. The obtained results of electrochemical techniques measurement indicated that the composites coated samples give better corrosion protection against attacking electrolyte. Originality/value The ever-increasing price of nickel (Ni) is driving the industries to use low-Ni austenitic stainless steels (ASSs). However, it exhibits relatively poor corrosion resistance as compared with conventional Cr-Ni ASSs. Nonetheless, its corrosion resistance can be enhanced by polymeric (electroactive polyimide [EPI]) coating. CuO particles exhibit the hydrophobic properties and can be used as inorganic filler to incorporate in EPI to further enhance the corrosion protection. The present research paper is beneficial for industries to use low-cost AISI 201, enhance its corrosion resistance and replace the use of costly conventional Cr-Ni ASSs.

Sustainable biocomposites from Nylon 6 and polypropylene blends and biocarbon – Studies on tailored morphologies and complex composite structures

The ability of irregular and polydisperse sustainable biocarbon (BC) particles to deform a binary immiscible blend in composites formulations was investigated at different particle polarity. Herein, up to 40 wt% of biocarbon particles with size of ~1.80–2.00 µm were melt-compounded with polyamide 6 (PA6) and polypropylene (PP) at 80/20 and 20/80 (w/w). A high affinity of biocarbon for the PA6 phase over the PP phase was observed and was not affected by the polarity. A critical filling ratio (φBC in PA6 or φPA6+BC in PP) marking the formation of a 3-dimensional percolated network between the particles was estimated at ~0.26–0.31, yielding a fractal network of dimension df ~1.7–2.0. This critical ratio was assessed by measuring the droplet size, material viscosity, and yield stress. In addition, a transition from a droplet suspension to funicular morphology was observed at φPA6+BC ~0.36 in PP. It was furthermore found that solid- or liquid-like behavior in such morphologies was induced by a high or low biocarbon surface functionality as a result of low or high biocarbon pyrolysis temperature. As such this work gives new insight on morphology development and properties of complex composite structures with heterogeneous particles.

Review on fabrication and mechanical characterization of shape memory alloy hybrid composites

Metals are replaced by composites in various structural applications as composite possesses unique properties such as low weight, high specific strength, and stiffness. However, there is a need to enhance mechanical properties of composite structure. Therefore, hybridization of composite is required that can improve mechanical properties in different testing conditions. One method of fabricating hybrid composite is by reinforcing the shape memory alloy (SMA) in composite laminates. In spite of various advantages offered by the SMA, there is always a challenge in an integration of SMA with the composite for the hybridization. Mainly, these challenges offered during the fabrication process due to their incompatibility of matrix fiber, lack of bonding between SMA and polymer matrix, location of SMA in the composite, and curing temperature of composites. Different methods have been proposed by various researchers for reinforcing SMA into composite. The current review emphasizes the fabrication process of SMA hybrid composite (SMAHC), fractographic study using scanning electron microscopy (SEM) to detect interfacial bonding of SMA and polymer matrix and also the effect of SMA reinforcement on mechanical properties such as tensile, flexural, and impact.

Highly Multifunctional Dopamine-Functionalized Reduced Graphene Oxide Supercapacitors

Summary Batteries and supercapacitors that possess the mechanical properties of structural composites are desirable for electric vehicles and aerospace applications, as energy may be stored within structural panels to realize significant mass and volume savings. However, current electrode materials suffer from poor mechanical performance, as described by a low multifunctional efficiency parameter (

Optimization of the Production Process and Product Quality of Titanate Nanotube-Drug Composites.

Recently, there has been an increasing interest in the application of nanotubular structures for drug delivery. There are several promising results with carbon nanotubes; however, in light of some toxicity issues, the search for alternative materials has come into focus. The objective of the present study was to investigate the influence of the applied solvent on the composite formation of titanate nanotubes (TNTs) with various drugs in order to improve their pharmacokinetics, such as solubility, stability, and bioavailability. Composites were formed by the dissolution of atenolol (ATN) and hydrochlorothiazide (HCT) in ethanol, methanol, 0.01 M hydrochloric acid or in ethanol, 1M sodium hydroxide, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), respectively, and then they were mixed with a suspension of TNTs under sonication for 30 min and vacuum-dried for 24 h. The structural properties of composites were characterized by SEM, TEM, FT-IR, differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, and optical contact angle (OCA) measurements. Drug release was determined from the fast disintegrating tablets using a dissolution tester coupled with a UV–Vis spectrometer. The results revealed that not only the good solubility of the drug in the applied solvent, but also the high volatility of the solvent, is necessary for an optimal composite-formation process.

Assessment of dynamic properties of hybrid ribbon reinforced multifunctional composite sandwich plates: Numerical and experimental investigation

Abstract This study investigates numerically and experimentally the effect of longitudinal ribbon reinforcement in conventional honeycomb structure on the various dynamic characteristics of a hybrid composite sandwich plate. Longitudinal strips are considered to be embedded along the transverse directions at various locations of a honeycomb core material without and with carbon nanotubes (CNT) reinforcement in a composite sandwich plate. The governing differential equations of motion of the various hybrid honeycomb composite sandwich plate configurations with strips inserted in conventional honeycomb structures as core layer having top and bottom face composite layers are derived using higher order shear deformation theory (HSDT) and solved numerically using a four noded rectangular finite element. Further, experimental investigations are performed by fabricating the various strips embedded hybrid honeycomb core material with and without CNT reinforcement to evaluate the shear and loss moduli using the alternative dynamic approach. The efficacy of the developed finite element formulation is demonstrated by comparing the experimental and numerical results obtained in terms of natural frequencies and loss factors for the various prototypes of honeycomb composite sandwich plates. Also, the effect of variation in CNT content and thickness of longitudinal ribbon reinforcement in conventional honeycomb core material and ply orientation of the face sheets on the various dynamic properties of hybrid composite structures are studied under various end conditions. This study proposes that the ribbon reinforcement location and the addition of CNTs in honeycomb core materials strongly influence the stiffness, damping and transverse vibration displacements of the ribbon reinforced hybrid composite sandwich plates.

Analytical design of flat-top transmission filters composed of several resonant structures.

Resonant properties of composite structures consisting of several identical resonant structures (e.g. multilayer thin-film structures or guided-mode resonance gratings) separated by phase-shift layers are investigated theoretically. Using the scattering matrix formalism, we analytically demonstrate that, at properly chosen thicknesses of the phase-shift layers, the composite structures comprising two or four resonant diffractive structures with a Lorentzian transmittance profile optically implement the Butterworth filters of the order two or three, respectively, and enable achieving flat-top transmission spectra with steep slopes and low sidebands. In addition, we show that the composite structures consisting of three or four second-order Butterworth filters can accurately approximate the fourth- or fifth-order Butterworth filters, respectively. The presented theoretical results are confirmed by rigorous numerical simulations of composite structures consisting of the so-called W-structures (simple three-layer resonant structures comprising a high-index core layer and two low-index cladding layers in a high-index dielectric environment). The simulation results confirm the formation of flat-top transmittance peaks, the shape of which fully agrees with the derived theoretical description. Moreover, we demonstrate an exceptionally simple mechanism of controlling the transmittance peak width, which consists in changing the thicknesses of the cladding layers of the initial W-structure and enables generating flat-top transmission peaks with a significantly subnanometer width.

Modal Diagnostics of Lathe Designs with Composite Bases

The basic damping properties of composite lathe structures are analyzed by modal diagnostics. New experimental results and literature data from non-Russian research are employed. The damping properties of cast-iron and composite lathe structures are compared. The composites considered are ferrocement, polymer concrete, and metal concrete.

Resonant properties of composite structures consisting of several resonant diffraction gratings.

We theoretically and numerically investigate resonant optical properties of composite structures consisting of several subwavelength resonant diffraction gratings separated by homogeneous layers. Using the scattering matrix formalism, we demonstrate that the composite structure comprising N gratings has a multiple transmittance zero of the order N. We show that at the distance between the gratings satisfying the Fabry-Pérot resonance condition, an (N - 1)-degenerate bound state in the continuum (BIC) is formed. The results of rigorous numerical simulations fully confirm the theoretically predicted formation of multiple zeros and BICs in the composite structures. Near the BICs, an effect very similar to the electromagnetically induced transparency is observed. We show that by making the proper choice of the thicknesses of the layers separating the gratings, nearly rectangular reflectance or transmittance peaks with steep slopes and virtually no sidelobes can be obtained. In particular, one of the presented examples demonstrates the possibility of obtaining an approximately rectangular transmittance peak with a significantly subnanometer width. The presented results may find application in the design of optical filters, sensors and devices for optical differentiation and transformation of optical signals.

Composition–Structure–Property Correlations in Rare-Earth-Doped Heavy Metal Oxyfluoride Glasses

Structure–property correlations in oxyfluoride glasses have been explored in a series of lead fluoroborate and lead fluorogermanate glasses with nominal compositions (50 – x – y – z)B2O3–40PbO–y(Al...

Damage Analysis and Experimental Study of Composite Structures with Initial Delamination

Composite laminates are prone to delamination during hot pressing and cooling, this delamination is one of the most important defects that affect the properties of composite structures, the formation and propagation of delamination in composite materials can significantly reduce the structural strength of composite materials and even lead to catastrophic failure. In this paper, the two parameters of the initial stratified position and the initial stratified diameter are selected to research the effects of these two parameters on the mechanical properties of composite laminates through numerical simulation and experiment, and concludes that the influence of initial delamination along the thickness direction on the average compression modulus and strain of the linear segment is small; the influence of delamination on the ultimate bearing capacity increases with the decrease of the distance between the delamination and the center plane. When the diameter of the delamination is in the range of 8%~20% of the effective area(18~44 mm), the influence on the average compression modulus, ultimate bearing capacity and strain of the linear segment is not obvious. When the diameter is increased to 27% of the effective length(60 mm), the above properties have changed greatly. And then, this paper introduces the bilinear controlled cohesive elements into the progressive failure method to calculate the ultimate load capacity of composite laminates, and demonstrate the accuracy of the simulation method by experiments.

Impact of PVDF/PEO blend composition on the β-phase crystallization and dielectric properties of silica nanoparticles incorporated polymer nanocomposites

Polymer nanocomposite (PNC) films consisted of varying weight composition polymer blends of poly(vinylidene fluoride) (PVDF) and poly(ethylene oxide) (PEO) as host organic matrices incorporated with 5 wt% amorphous silica (SiO2) nanoparticles as inorganic nanofiller have been prepared by solution casting method. The alterations in morphology, PVDF polymorphism and relative fraction of β-phase crystals, degree of crystallinity, and the polymer-polymer and polymer-nanoparticle interactions with change of polymer blend compositional weight ratio (i.e., PVDF/PEO = 100/0, 75/25, 50/50, 25/75, and 0/100) have been investigated by the SEM, EDX, XRD, and FTIR measurements. The frequency dependent complex dielectric permittivity, ac electrical conductivity, and electric modulus of the PNC films are studied at room temperature by employing the DRS technique. The SEM images reveal that the spherulite morphology of PVDF/PEO blend structures incorporated with SiO2 nanoparticles is altered enormously with the change of polymers blend compositions in the PNC films. The XRD results of these PNC films confirm that the β-phase crystallization is considerably enhanced in the PVDF-rich PNC film but it decreases almost linearly with the increase of PEO amount in the host matrices of these films, and remains higher for the PNC films in comparison to that of the pristine polymer blend films. The degree of crystallinity of these PNC films enhances non-linearly with the increase of PEO concentration but it is found low as compared to that of the PVDF/PEO blend films without nanofiller. Dielectric dispersion in the frequency range from 20 Hz to1 MHz reveals that the interfacial polarization significantly contributed to the enhancement of dielectric permittivity in the audio frequency range of dielectric spectra of these PNC films. The addition of 5 wt% amount of SiO2 nanoparticles in the pristine PVDF and PEO matrices reduces the dielectric permittivity over the entire frequency range, whereas the presence of these nanofiller particles in the PVDF/PEO blend matrices based PNC films increases at radio frequencies which is predominantly due to enhancement of the β-phase crystals. The relaxation time values determined from the relaxation peaks exhibited in the loss part of electric modulus spectra confirm that there is an increase in hindrance to the PEO chain segmental dynamics with the increase of PVDF amount in the polymer blend compositions of these PNC films, whereas the dc electrical conductivity is found independent of the blend composition. The polymer blend compositional ratio dependent promising structural, dielectric, and electrical properties of these PNC films offer their suitability as tunable novel nanodielectric materials of multifunctionality for the flexible electronic devices.

Determination and monitoring of strength properties of aircraft composite structures by magnetic microwires

The submitted paper deals with the application of magnetic microwires as sensors. The aim is to summarize the engineering view of the given issue and to inform about necessary steps for practical application of such a new sensor in the aircraft industry. The paper talks about the formation of composite samples necessary for tensile strength tests, the aim of which is to obtain material properties of composite materials. The obtained material properties of fiberglass samples are processed into graphical and tabular form. Subsequently, the material properties are used in the strength calculations of the prismatic beam, in which magnetic microwires are applied in the experimental part of the work. There are described in the submitted article two application of magnetic microwires as a stress monitoring sensors.

Computational analysis of composition-structure-property-relationships in NZP-type materials for Li-ion batteries

Compounds crystallizing in the structure of NaZr2(PO4)3 (NZP) are considered as promising materials for solid state electrolytes in Li-ion batteries. Using density functional theory (DFT), a systematic computational screening of 18 NZP compounds, namely, LiX2(LO4)3 with X=Ti, V, Fe, Zr, Nb, Ru, Hf, Ta, Os, and L=P, Mn, is performed with respect to their activation energies for vacancy-mediated Li migration. It is shown how the different ionic radii of the cationic substitutions influence structural characteristics such as the octahedron volumes around Li ions on the initial-state and transition-state sites, which affect the activation energies (“composition–structure–property” relationships). The prevalent assumption that structural bottlenecks formed by triangularly arranged oxygen atoms at a certain location along the migration path determine the energy barriers for Li migration is not supported by the DFT results. Instead, the ionic neighborhood of the migrating ion in the initial and in the transition state needs to be taken into account to relate the structure to the activation energies. This conclusion applies to Na-containing NZP compounds as well.