Properties Of Composite Structures Research Articles

Characterization of thermoplastic nonwovens of copolyamide hot melt adhesives filled with carbon nanotubes produced by melt-blowing method

Thermoplastic nonwovens containing 2.5 wt% of multi-walled carbon nanotubes were manufactured by half-industrial melt-blowing process from two copolyamides belonging to the group of hot melt adhesives having different melt-viscosities. The initial masterbatches have been analyzed by their rheological and thermal properties to adjust the appropriate conditions of melt-blowing process which allowed to manufacture the nonwovens without structural defects. It was found using a scanning electron microscope that in 10 wt% masterbatches fewer agglomerates of the multi-walled carbon nanotubes occurred in less viscous coPA2 and their average diameter measured by ImageJ was 60 µm. For more viscous coPA1 some oval agglomerates with even 270 µm diameters have been detected but during the extrusion they were destroyed. Microstructural observations of the nonwovens showed that fibers occur in the entangled state and their average diameter is around 45 µm for each type of the copolyamides. Analysis of the electrostatic properties of the nonwovens with low and high areal weight showed that electrical surface resistivity is slightly higher for the nonwovens based on coPA2 and those with higher areal weight. Using high-resolution microscope, it was possible to ascertain that in the nonwovens made of coPA1 + 2.5 wt% the carbon nanotubes are well-dispersed with their visible alignment along the fiber axis, unlike those in the nonwovens made of coPA2 + 2.5 wt% which occur mainly as lightly connected bundles without any specific orientation. The developed nonwovens can be used as interlayers to increase the electrical and mechanical properties of composite structures in the aerospace and automotive sectors.

Magneto-optical properties of plasmonic hyperbolic metamaterials

The results of the experimental studies and numerical simulation of optical and magneto-optical properties of composite structures containing gold nanorods in porous anodic alumina templates and coated by a continuous nickel film are presented. We reveal two features in the Faraday rotation spectra of the structures in the vicinity of the wavelengths of 540 nm and 810 nm, which correspond to the epsilon-near-pole and epsilon-near-zero regions, respectively. Experimentally observed distinct enhancement of magneto-optical effects in the structures in the spectral vicinity of these points are consistent with the simulation results and open up novel opportunities for magnetic-field-assisted light manipulation.

A hierarchical asymptotic homogenization approach for viscoelastic composites

Effective properties of non-aging linear viscoelastic and hierarchical composites are investigated via a three-scale asymptotic homogenization method. In this approach, we consider the assumption of a generalized periodicity in the different structural levels and their characterization through the so-called stratified functions. The expressions for the associated local and homogenized problems, and the effective coefficients are derived at each level of organization by using the correspondence principle and the Laplace-Carson transform. Considering isotropic components and a perfect contact at the interfaces between the constituents, analytical solutions, in the Laplace-Carson space, are found for the local problems and the effective coefficients are computed. An interconversion procedure between the effective relaxation modulus and the effective creep compliance is carried out for obtaining information about both viscoelastic properties. The numerical inversion to the original temporal space is also performed. Finally, we exploit the potential of the approach and study the overall properties of a hierarchical viscoelastic composite structure representing the dermis.

Effect of sintering temperature on pore ratio and mechanical properties of composite structure in nano graphene reinforced ZA27 based composites

Nano graphene platelet (Gr) reinforced nano composites with a zinc-aluminum alloy (ZA27) matrix were produced by powder metallurgy at four different mass ratios (0.5wt%, 1.0wt%, 2.0wt% and 4.0wt%) and three different sintering temperatures (425, 450, and 475°C). In order to investigate the effect of sintering temperatures and nano graphene reinforcement materials on the composite structure, the microstructures of the composite samples were investigated and their densities were determined with a scanning electron microscope. Hardness, transverse rupture, and abrasion wear tests were performed to determine the mechanical properties. According to the test results, the porosity increased and the mechanical strength of the nano composites decreased as the amount of nano graphene reinforcement in ZA27 increased. However, when the composites produced in different reinforcement ratios were evaluated, the increase in sintering temperature increased the mechanical structure by positively affecting the composite structure.

Compression properties of multifunctional composite structures with embedded lithium-ion polymer batteries

Multifunctional light-weight composite structures that combine high load-bearing properties with electrical energy storage capacity have potential application in energy intensive systems such as electric cars. This paper examines the effect of compression loading on the mechanical and electrical responses of light-weight carbon fibre laminates containing embedded lithium ion polymer (LiPo) batteries. The mechanical and electrical responses of the LiPo battery itself to compression loading are also examined. Embedding batteries has a significant adverse effect on the compressive stiffness, failure stress and fatigue life of laminates. The property reductions are attributed to several factors; namely the compressive properties of the battery being much lower than the composite material, the geometric stress concentration created by the battery, discontinuities in the carbon fibres, and the soft polymer layer at the battery-composite interface that effects load transfer. Experimental testing and finite element analysis reveal that the reduction to the compression properties is dependent on the number and arrangement of the batteries.

Comparison of Shear Rigidity of Epoxy and Vinyl Ester Reinforced Hybrid Honeycomb Core

Abstract In this study, the dynamic shear properties of a composite honeycomb core material made of glass fiber reinforced (epoxy resin and vinyl ester) polymers without and with reinforcement of carbon nanotubes are investigated. The carboxylic acid functionalized multi-walled CNTs were randomly dispersed into an organic solvent (extra pure acetone) to split and add homogeneously into the vinyl ester resin by using the ultra-sonication technique®. The honeycomb composite test materials were made through the high carbon- chromium corrugation honeycomb die using the vacuum-assisted hand-layup technique. The vibration analysis of honeycomb materials was performed experimentally to obtain the shear moduli along the corrugation (Gxz) and joining (Gyz) directions based on the dynamic approach. The results showed that the reinforcement of CNTs in the composite honeycomb materials would enhance the shear moduli significantly without any modifications in the mass of the honeycomb structure. The strong interfacial bonding and random addition of CNTs in the composites improve the shear properties considerably than that of honeycomb without CNT reinforcement. This result provides the guidelines for the modern designer on increasing the shear properties of the honeycomb composite structures using the CNT reinforcement

Comparison between honeycomb and composite corrugated cores in sandwich panels under compression loading

The study is to evaluate the compression properties of the polymeric composite corrugated-core sandwich structure against the honeycomb-core structure. The skin facings are from the prepreg carbon fibre composite laminate, while the core is made of different materials. Four core types are suggested; carbon fibre corrugated-core, fibreglass corrugated-core, Nomex honeycomb-core, and Kevlar honeycomb-core. The study is based on an experimental work of edgewise compression testing, and the comparison between alternatives are based on the specific properties-to-weight ratio. The analysed results prove there is superior compression capacity of the polymeric composite corrugated-core sandwich members to the honeycomb-core members, in particular in the nonlinear stage of compression test. The bonded surface between the honeycomb structure and the skins is often less than that of the corrugated profile for the same sandwich panel sizes. This contact area between the core and skin facings plays an important role in carrying load mechanism.

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.