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We present a complex variable method to evaluate the transverse effective transport properties of composites with a doubly-periodic array of fibers. The obtained complex variable solution is derived in a unified form for arbitrary doubly-periodic fiber arrays and different fiber-matrix interfaces i.e. perfect interface contact resistance interface and coating. The present method can be seen as an extension of the method originated by Rayleigh only for symmetric fiber arrays. The limitation of Rayleigh's method is overcome by introducing a supplementary equation. Explicit formulae of the effective transport properties approximated to finite orders are obtained which are written in a regular form for different fiber arrays and reveal the reciprocal relations for symmetric fiber arrays. The validity and accuracy of the solution are verified by numerical examples and comparisons with existing methods. (c) 2016 WILEY-VCH Verlag GmbH & Co. KGaA Weinheim

This paper presents results on a detailed comparative study of 2–2 relaxor-ferroelectric single crystal / polymer composites. Examples of the hydrostatic piezoelectric performance are discussed for 2–2 composites based on [011]-poled Mn-modified 0.26Pb(In1/2Nb1/2)·O3−0.42Pb(Mg1/3Nb2/3)O3−0.32PbTiO3 single crystals at a molar Mn concentration in the range of 1–5 mol. %. The high piezoelectric activity of these single crystals and rotations of the main crystallographic axes in the single-crystal layers of the composite lead to large values of hydrostatic piezoelectric coefficients , and , squared figure of merit , and electromechanical coupling factor . A rotation mode that leads to a weakening the piezoelectric activity related to the piezoelectric coefficient d32 < 0 is important to achieve composites with a range of large hydrostatic parameters, e.g., ≈ (300–350) pC / N, ∼ 100 mV·m / N, ≈ (21–23) C / m2, ∼ (24–30)·10−12 Pa−1, and ≈ 0.30. In contrast to , higher values of ∼ 10−10 Pa−1 are achieved due to the longitudinal piezoelectric effect. The results obtained in this piezoelectric composite system are interpreted by taking into account the orientation of 71° ferroelectric domains in the single-crystal layers and provide a route to form novel high-performance piezoelectric composites.

The results of investigations directed at improving the operational properties of composite materials of the diamond–(Fe–Cu–Ni–Sn) system have been presented. The computational procedure of optimal structural parameters of the diamond–metallic binder transient zone at which maximal mechanical and tribological properties of composites formed by sintering in hot molds with the subsequent additional hot pressing has been presented. Regularities of varying the structure of the transient zone diamond–metallic binder in compositions after sintering depending on parameters of hot pressing and their influence on mechanical and tribological properties of prepared composites have been revealed by X-ray structural analysis, scanning electron microscopy, and transmission electron microscopy. Ways of controlling structure formation processes for improving mechanical properties and wear resistance of composites have been shown.

The influence of introduction of particles of detonation-synthesized nanodiamonds into composites and aluminum-base light alloys on their physical and mechanical properties is analyzed. The data on microstructure and physical and mechanical properties of composites and cast aluminum alloys reinforced with diamond nanoparticles are presented. The introduction of nanoparticles is shown to result in a significant improvement of the material properties.

An investigation was made of the structure and thermophysical properties of composites based on polyethylene terephthalate (PET) and montmorillonite clay modified with organomodifiers of different nature. A study was made of the effect of organoclays on the morphology and crystallisation processes of PET. It was established that the introduction of small quantities of organoclay leads to an increase in the crystallisation rate, and also in the heat resistance of PET.

Automated fiber placement (AFP) has been widely used as an advanced manufacturing technology for large and complex composite parts and the trajectory planning of the laying path is the primary task of AFP technology. Proposed in this paper is an experimental study on the effect of several different path planning placements on the mechanical behavior of laminated materials. The prepreg selected for the experiment was high-strength toughened epoxy resin T300 carbon fiber prepreg UH3033-150. The composite laminates with variable angles were prepared by an eight-tow seven-axis linkage laying machine. After the curing process, the composite laminates were conducted by tensile and bending test separately. The test results show that there exists an optimal planning path among these for which the tensile strength of the laminated specimens decreases slightly by only 3.889%, while the bending strength increases greatly by 16.68%. It can be found that for the specific planning path placement, the bending strength of the composite laminates is significantly improved regardless of the little difference in tensile strength, which shows the importance of path planning and this may be used as a guideline for future AFP process.

A novel sequential homogenization scheme based on a multi-coated model was proposed to investigate viscoelastic properties of composite with functionally graded interphase. After investigating strain disturbance within the multi-coated model, the established sequential homogenization scheme contains two steps: Virtual adding by Self-Consistency scheme and Sequentially homogenization by Mori-Tanaka scheme. During homogenization, matrix was assumed to obey General Maxwell viscoelastic constitutive law and interphase is related to the matrix. Effectiveness of the present method was verified by the available experimental results and finite element simulations. Furthermore, effects of the reinforcement and the functionally graded interphase on storage and loss modulus with various load frequencies were studied. It was found that thickness and properties of the interphase influences loss factor in middle frequency ranges. In the end, responses under stress relaxation and constant strain rate were explored.

The use of materials in cars has changed significantly over the last few decades. Polypropylene is the top choice for automotive industry players because it has unparalleled flexibility, affordable cost and performance balance that successfully replace steel and other plastics as the material for the manufacture of motor vehicles. However, since the raw material of polypropylene is derived entirely from petroleum and natural gas which can be discharged at any time. Also, its use is not environmentally friendly which need an action to overcome one of them by developing composite technology. The purpose of this study was to know the relation of mass fraction of corncob fiber into polypropylene composites on tensile strength and composite morphology. Corncobs reinforce in polypropylene are 10, 20, 30 and 40% by weight. XRD analysis investigated at 2θ the crystalline part of corncob at 21°. The functional group of Si-OH and Si-O-Si were analyzed at wavelength 1030 and 1100 cm−1. The fracture surface of composite shows the crack effect of particle loading. Polypropylene composites filled with corncob increased in tensile strength and decrease in elongation at break with the increase of corncob particle loading.

In order to improve the utilization rate of kapok fiber, flame-retardant and sound-absorption composites were prepared by the hot pressing method with kapok fiber as the reinforced material, poly&epsilon, caprolactone as the matrix material, and magnesium hydroxide as the flame retardant. Then, the effects of hot pressing temperature, hot pressing time, density of composites, mass fraction of kapok fiber, thickness of composites, and air layer thickness on the sound-absorption properties of composites were analyzed, with the average sound absorption coefficient as the index. Under the optimal process parameters, the maximum sound absorption coefficient reached 0.830, the average sound absorption coefficient was 0.520, and the sound-absorption band was wide. Thus, the composites belonged to high-efficiency sound-absorbing material. The flame-retardant effect of magnesium hydroxide on the composites was investigated, and the limiting oxygen index could reach 31.5%. Finally, multifunctional composites based on kapok fiber with flame retardant properties, and sound-absorption properties were obtained.

The continuous increase in the demand for electricity causes the need to search for new energy sources and to look for savings during its transmission. One of the areas of interest are materials dedicated to low loss transformer cores. Due to good magnetic properties, amorphous and nanocrystalline iron-based alloys are used in this area. The limited dimensions of these materials make their application difficult. Magnetic composites based on ferromagnetic amorphous alloys are a new direction of research. Usually, composites are made using a non-magnetic binder. However, the separation of magnetic particles worsens the magnetic properties. The solution to this problem may be production of composites coated with high temperature varnish. As part of the work, the results of research on the structure and magnetic properties of composites based on amorphous iron alloys are presented. Composites were made with 0.5% resin by mass and without resin covered with high temperature varnish. Material produced without the use of resin had a lower coercive field value.

Three-dimensional (3D) printing is an additive manufacturing process that creates novel shapes or adds functionalities to other objects, such as textile fabrics. Especially with fused deposition modeling technology, multimaterial items can be created by printing onto existing objects or including other materials during the printing process. In this way, composites with new mechanical properties can be formed. This chapter shows the possibilities of including textile materials into 3D printed objects created from diverse polymers and discusses the influence of physical and chemical modifications of both materials' surfaces. It shows how the interface adhesion changes the mechanical properties of composites from textile materials and one or more 3D printed polymers.

The effective elastic properties of composites reinforced by spatially randomly distributed short cylindrical fibers with certain aspect ratio are investigated using the numerical homogenization method. A modified RSA algorithm is proposed to generate the periodic RVEs. The periodic boundary conditions are introduced and the periodic RVEs thus created are analyzed to obtain the mechanical properties of composites by using the FE package ABAQUS. The ABAQUS Python Interface is used to introduce the periodic boundary conditions and to obtain the average stresses and strains of RVEs. The simulation results show that the periodic boundary conditions guarantee the continuity of strain and stress fields on the boundaries of RVEs. In the case of the fiber aspect ratio of 15 and fiber volume fraction of 10%, it is sufficient to consider the size of RVE as L / l = 2.5 , in which an approximately random fiber orientation exists. The effective elastic properties of composites obtained by the numerical homogenization agreeing well with those obtained from the traditional equations for composites based on the Halpin–Tsai estimation and with those measured from the uniaxial tensile experiments shows the validation of the numerical homogenization for effective elastic properties of composites reinforced by spatially randomly distributed short fibers.

The correlation between MWCNT aspect ratio and the quasi-static and dynamic mechanical properties of composites of MWCNTs and PMMA was studied for relatively long MWCNT lengths, in the range 0.3 mm to 5 mm (aspect ratios up to 5 × 105) and at low loading (0.15 wt%). The height of the MWCNTs prepared were modulated by controlling the amount of water vapour introduced in the reactor limiting Ostwald ripening of the catalyst, the formation of amorphous carbon and any increase in CNT diameter. The Tg of PMMA increased by up to 4 °C on addition of the longest tubes as they have the ability to form physical junctions with the polymer chains which lead to enhanced PMMA-MWCNTs interactions and increased mechanical properties, Young's modulus by 20% on addition of 5 mm long MWCNTs. Predictions of the Young's modulus of the composites of PMMA and MWCNT with the Mori-Tanaka theory show that future micromechanical models should account for MWCNT agglomeration and polymer-nanotube interactions as a function of CNT length.

International audience; The present work deals with the estimation of the linear viscoelastic effective properties for composites with periodic structure and rectangular cross-section fibers, using the two-scale asymptotic homogenization method (AHM). As a particular case, the effective properties for a layered medium with transversely isotropic properties are obtained. Two times the homogenization method, in different directions, according to the geometrical configuration of the composite material is applied for deriving the analytical expressions of the viscoelastic effective properties for a composite material with rectangular cross-section fibers, periodically distributed along one axis. In addition to that, models with different creep kernels, in particular, the Rabotnov’s kernel are analyzed. Finally, the numerical computation of the effective viscoelastic properties is developed for the analysis of the results. Moreover, a numerical algorithm using FEM is developed in the present work. Comparisons with other approaches are given as a validation of the present model.

We have studied the influence of inorganic particles on the photoluminescent properties of the nematic liquid crystal 5CB in composites based on carbon nanotubes (CNTs) and hybrid nanoparticles consisting of carbon nanotubes and platelets of the organically modified mineral montmorillonite (MMT). We show that the photoluminescence (PL) of 5CB + CNT composites is characterized by excimer emission of the 5CB molecules. Adding carbon nanotubes to the liquid crystal medium leads to a considerable decrease in the photoluminescence intensity, but has practically no effect on the bulk structural alignment in the organic matrix. Hybrid CNT–MMT particles form a uniform coagulation network in the composite with 5CB and significantly disrupt the nematic structure of the liquid crystal. Bent conformations of the 5CB molecules appear which are typical of the liquid crystal monomers. The presence of the indicated 5CB conformers in the system and also the weaker interaction between the liquid crystal and the inorganic filler explain the increase in the photoluminescence intensity for the composite 5CB + CNT–MMT compared with the emission characteristics for the original liquid crystal.

This study focuses on the development and characterization of polyurethane/bamboo fiber composites foams which have the specific properties to participate both in the thermal insulation and regulation of the humidity inside the building. The polyurethane foam reinforced by bamboo fibers (5–20 wt%) were produced to investigate the mechanical test, the morphological characterization and thermal properties. The result from mechanical test showed that the compressive strength was increased at 5 wt % of bamboo fiber. Likewise, the effects of the fibre diameter and nature of bamboo fibers on some properties (compressive test, thermal analyses, surface morphology) of bamboo fibre reinforced rigid polyurethane foam were studied. The bamboo Gai and Luong fibres result in composites with better mechanical strength than the other fiber composites.

A comb-like copolymer poly (styrene-co-maleic anhydride)-graft-poly (ε-caprolacton) (SMA-g-PCL, SP) with carboxyl group as an anchoring group and polycaprolactone as a solvent chain was used as an effective dispersant for CaCO3 in the polypropylene (PP) matrix. The effects of CaCO3 concentration on crystallization behaviors, mechanical properties, and thermal stabilities were studied systematically. The results revealed that the dispersion of CaCO3 in the PP matrix was markedly improved owing to the steric hindrance effect caused by PCL, and the SP-coated CaCO3 was a very effective nucleating agent for PP. Proper CaCO3 concentration corresponded to the improvement of crystallization temperature, crystallinity, and crystallization rate of PP. There was only a slight improvement in yield stress but great improvement in Young’s modulus, flexural modulus, and impact strength. However, the excessive CaCO3 filler deteriorated the mechanical properties. The good dispersion of SP-coated CaCO3 in the PP matrix also accounted for the improvement of thermal stability. The initial decomposition temperature of the PP/CaCO3 composite with 7.4 wt.% CaCO3 increased 35°C compared with neat PP.

We propose an innovative numerical scheme (based on complex variable techniques) for the calculation of the effective properties of a composite containing unidirectional periodic fibers in which we additionally incorporate the separate contribution of the ‘interface effect’ between the fibers and the surrounding material. The incorporation of interface effect into the model of deformation allows our model to accommodate the general class of nanocomposite materials, a fast growing area of research and our primary focus in this paper. The composite is loaded by a constant normal strain along the direction parallel to the fibers and by a uniform remote loading in the plane perpendicular to the fibers. Our method is based on the analysis of a representative unit cell with periodic boundary conditions imposed on its edge. Several examples are presented to study the influence of the interface and the volume fraction of the fibers on the effective properties of the composite and the interfacial stress field. We show that when the volume fraction falls below roughly 9%, the interfacial stress distribution recovers effectively to that corresponding to a single fiber with the same interface parameters embedded within an infinite matrix. We find also that if the shear modulus of the fibers exceeds approximately two and a half times that of the matrix, the interface effect is negligible in the determination of the effective properties of the corresponding nanocomposites. Finally, we show that the use of traditional effective medium theories may induce significant errors in the determination of transverse effective properties (in the plane perpendicular to the fibers) of the composite, in particular when the fibers are significantly softer than the matrix.

The acid–base balance of the surface of silica filler (SF) particles of different grades was determined, and its influence on the structure and properties of mixes based on nitrile butadiene rubber (NBR) was investigated. A near-linear correlation was found between the proneness of the SF particles to flocculate and the concentration of acid centres (ACs) on their surface, in the absence of any pronounced influence on this index of the degree of dispersion of the filler particles. Of all the SF grades investigated, the greatest capacity to form flocculation structures is exhibited by a filler characterised by a higher SF concentration. Increase in the SF concentration leads to an increase in the relative content of physical and covalent bonds in binary mixes of NBR and SF. It is shown that, to reduce the negative effects associated with the formation of flocculation structures, including in the induction period of vulcanisation, it is necessary to select a filler with a lower concentration of these centres.

In order to study the microwave properties of suspensions including lightweight core–shell ellipsoids, the calculation formula was obtained by substituting an equivalent ellipsoid for the original core–shell ellipsoid. Simulations for Fe-coated diatomite/paraffin suspensions were performed. Results reveal that the calculated results fitted the measured results very well when the inclusion concentration was no more than 15 vol%, but there was an obvious deviation when the inclusion concentration reached 24 vol%. By comparisons, the formula for less diluted suspensions was more suitable for calculating the electromagnetic parameter of suspensions especially when the ratio was smaller between the electromagnetic parameter of the inclusion and that of the host medium.

Composites Al/Al2O3 (lamellar cermet matrix)–filler (discrete metallic fibers, duralumin chips, graphite particles, fused corundum grains, and technical alumina spherulites) are fabricated. To form the lamellar cermet matrix, industrially produced PAP-2 aluminum powder was used. This powder consists of scaled particles with stearin coating (the specific surface of the powder is 4.1322 m2/g, and its particle size varies from 0.03 to 10 μm). In order to form the composites, the following main process operations were used: heat treatment of the PAP-2 powder in air to burn out stearin from the particle surface and replace it with a passivating alumina film, mixing of the thus formed powder product with a filler, and compaction and reaction sintering of powder billets in the filtration burning mode in air. To fabricate the Al/Al2O3–C composite, a new approach based on the saponification chemical reaction of stearin is proposed. This reaction runs between stearin on the surface of aluminum particles and caustic soda, which is the product of hydrolysis of the diluted liquid glass introduced into initial powder. The reaction products (sodium stearate and glycerol) are decomposed during the subsequent heat treatment in air with the formation of a coke residue on the particle surface. The physicochemical properties of the composites were determined using standard and conventional procedures.

Computational micro-mechanics is employed in this work to evaluate effects of fiber-matrix interface damage on the elastic properties of polymer matrix composites with continuous glass fibers. It is assumed that damage affects local zones along the fiber and a sector on the perimeter around the fiber. Elastic modulii are evaluated using Finite Element analysis, for a range of values in damage parameters considered. The occurrence of bi-modular behavior, with differences in Young’s modulus under tension and compression, has been represented by contact without friction. Based on extensive parametric results, a Least Squares Method is employed to derive analytical expressions for each material property as a function of damage parameters. In most cases the elastic modulus has a nonlinear relation with the damage parameter in the length of the fiber, with the exception of the transverse elastic modulus under tension. The analytical expressions are used to couple micro and macro scales in an off-line scheme, without the need to perform in-time micro-scale computations.

Composites with photoelectrical, nonlinear optical, and photorefractive properties have been prepared. The composites consist of polyvinyl alcohol, single-wall carbon nanotubes, and fullerene C60. Addition of C60 with a long wavelength boundary near 630 nm resulted in an eight- to tenfold increase in both the quantum efficiency of generation of mobile hole charges and the photorefractive two beam gain coefficient measured at wavelengths exceeding 1000 nm (over an area of optical absorption of nanotubes). This is attributed to electron trapping by acceptor fullerene, which limits the regeneration of photogenerated charges and provides an increase in mobile hole charges.

Biodegradable polymers based on the renewable resources are a good alternative to raw petrochemical-based materials as they are environmentally safe and rapidly degradable in natural conditions, have no discharge of harmful substances to the environment. However, the reason hampering the widespread use of biodegradable polymers in the production of materials is their high cost. In this regard the technology of obtaining of wood-filled biodegradable composites based on the binder biodegradable polymer polylactide was considered. The thermally modified wood fibers are offered to use as the filler. In the course of the research the samples of wood-plastic composites, which were subsequently tested for strength and water absorption were obtained. It is established that with the increase of temperature of processing of a wood filler there is an increase in the strength characteristics of the resulting composite, the sorption performance of the composite is, on the contrary, reduced. Hence, the proposed composite material may be applied as a solid packaging material.

The paper investigates new composites fully based on wastes of polyethylene terephthalate, rubber, high-density polyethylene, and wood, aiming at multifunctional, environmental-friendly materials, for indoor and outdoor applications. The rubber: polyethylene terephthalate: high-density polyethylene: wood ratio and compression molding temperatures are optimized considering the output mechanical properties, focusing on increasing the waste polyethylene terephthalate content. To investigate the durability in the working conditions, the water-stable composites, with good tensile and compression strengths were exposed to surfactant systems, saline aerosols, and ultraviolet radiations. The results prove that surfactant immersion improves the interfaces and the mechanical properties and a pre-conditioning step involving the dodecyltrimethylammonium bromide surfactant is recommended, prior application. The interfaces and the bulk composites were investigated by X-ray diffraction, Fourier-transform infrared, differential scanning calorimetry, contact angle measurements, scanning electron microscopy, atomic force microscopy, to identify the properties that influence the mechanical behavior and durability. The composites containing 30% of polyethylene terephthalate, obtained at 160℃ and 190℃ have a good combination of mechanical properties and durability that is enhanced by the plasticizing effect of water and surfactants. The compressive strength of the composite processed at 190℃ was 51.2 MPa and the value increased to 58.4 MPa after water immersion. The ultraviolet and saline exposure slightly diminished this effect; however, long time testing (120 h) ended up with values higher than those corresponding to the pristine composite: 55.3 MPa after ultraviolet and 57.1 MPa after saline exposure.

Optical and electrical properties of cyanoethyl ether of polyvinyl alcohol with filling of barium titanate BaTiO3 modified by shungite carbon nanoparticles are studied. It is found that the modification affects the diffuse reflectance spectra and dispersion characteristics of the impedance components due to a change in the nature of interfacial interactions in the system. The values of the forbidden band width for various modifier and filler concentrations are determined.

On the base of Lihtenecker equation analytical expressions for temperature dependencies of the dielectric constant and of the dielectric loss tangent for metal-polymer composites are obtained. The results of an experimental study of the temperature properties of these materials are given. The experimental results are in the good agreement with theoretical data. References 7, figures 3.

In this work, volcanic basalt rocks, which were collected from different parts of Van city located in Eastern Anatolia, have been discussed in the context of impedance properties. The real and imaginary components of dielectric constants, dielectric dissipation factor, dielectric strength, AC conductivity and s frequency exponent parameter have been determined. According to AC conductivity results, it has been determined referring to s parameters' values, correlated barrier hopping (CBH) model is valid for all volcanic basalt rock samples at high frequency region. Moreover, the critical frequency that corresponds to the change of conductivity characteristic of all basalt volcanic rocks has been determined. Furthermore, due to their low conductivities Sample-1 and Sample-2 have been suggested as promising materials for electromagnetic radiation shielding applications for the high and low frequency regions, respectively.

The aim of this work was to determine the impact the plasticizing agent has got on hydrolytic degradation of polylactide-based composites in the form of films. The research involved polylactide composites where Nanofil2 or Montmorillonite K10 were used as nanoclays and (poly(e-caprolactone)) was introduced into the polymer matrix as plasticizer. Hydrolysis was carried out in phosphate buffer solution (pH 7.40) at 37 °C. Degradation process of polylactide-based composites was studied by incubating samples in 100 ml solution for a maximum of 180 days. In order to determine the influence of the plasticizer on hydrolysis, the materials were investigated by various analytical techniques. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) were used in order to investigate the thermal properties of samples during the degradation process. Gel permeation chromatography (GPC) was used to observe the decomposition of the polyesters. Morphology and structural changes during controlled hydrolysis were studied by atomic force microscopy (AFM). The results suggest that introduction of plasticizer into pure polymer as well as into PLA-montmorillonite system accelerates decompositions of investigated materials.

Dependences of the transmittance, absorbance, and reflectance of the composite based on a transparent matrix and copper spherical nanoparticles on the sample thickness and the mass fraction of particles are calculated for radiation of the first and second harmonics of a neodymium laser using the Mie theory and the stationary radiation transfer equation. Distributions of the luminance gain are calculated at different distances from the sample surface. It is shown that the luminance gain increases with nanoparticle radius and radiation wavelength due to multiple scattering. In the limit of a small sample thickness, the luminance gain has a threshold value due to the effect of the total internal reflection. Results obtained are needed for optimization of an optical detonator capsule based on a transparent explosive material and copper nanoparticles.

The present work on the mechanical properties of ≤10 wt% fly ash additions in 2.5 wt% increments to recycled high-density polyethylene (RHDPE) synthesizes experimental data from three similar published reports. The present work shows, as a function of increasing fly ash addition level, maxima at the initial fly ash addition level of 2.5 wt% for the tensile elastic modulus (+25%) and tensile strength (+10%); a slight general increase in the yield stress (+6%); and significant general decreases in the yield strain (−61%), elongation at break (−92%), and Charpy impact strength (−55%). Combining these data with data for higher-level additions of fly ash (≤40 wt%/23 vol%) and cenospheres (≤39 vol%) to HDPE or RHDPE provides the basis for design parameters and a generalized model for the interpretation of failure of composites of hard brittle spherical dispersant additions in ductile polymeric matrices. The relevant load-extension plots are characterized by three behavioral regions: ductile deformation (dispersion strengthening and stress concentration), crazing (debonding and cavitation), and brittle failure (fibril failure). The locations of these regions and their transitions are a function of five dependent variables: dispersant volume, dispersant particle size, intrinsic flaw size (viz., dispersant size), generated flaw size (viz., void size), and interfacial bond strength and associated load transfer. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

This study explored the use of J-integral approach for characterizing mode I, mode II and mixed-mode I/II interlaminar fracture toughness of composites materials. Delamination tests were conducted to measure the fracture toughness and the resistance curve (R-curve) for double cantilever beam, end-notched flexure and mixed-mode bending specimens. The J-integral approach and the well-established ASTM standard methods based on LEFM were compared in this work. The results obtained from both methods are in very good agreement. However, the J-integral method has the advantages of being applicable to materials with large fracture process zone (e.g., composites with fiber bridging) and provides a simpler experimental procedure with fewer inputs. More importantly, the presented method avoids the ambiguity in visual measurements of delamination length required by the ASTM standard methods. In this study, an image-processing program based on Hough transform was developed to obtain the rotation angles of the specimen. The method provides good accuracy and has lower requirements for image resolution, light and material surface compared to previous methods.

Thick films of composites of iron–aluminium oxide (FeAl2O3) were prepared by mixing paraffin wax with a powder of aluminium oxide (Al2O3) and iron granular (Fe) (600 μm in size). The current–voltage (I-V) characteristic was measured at different temperatures (293– 328 K). The electrical conductivity was also measured at those temperature levels. It was noted that an increase in temperature leads to an increase in electrical conductivity. The activation energies (Ea) were determined to be 0.357–0.125 ev; the electrical conductivity mechanism was identified as the Schottky and Poole–Frenkel effects.

Composites of wood waste and high-density polyethylene (HDPE) resins and different melt flow index (MFIs) was development in this work. Therefore, it was possible to assess their effect on the mechanical, thermal, and morphologic properties of these composites. The formulations were prepared using a twin-screw extruder, and the MFI, tensile strength, flexural strength, and impact strength of the composites were analyzed. Additionally, the thermal properties were evaluated by differential scanning calorimetry (DSC). Finally, structural analyses using optical microscopy (OM) and scanning electron microscopy (SEM) were performed to assess the particles’ dispersion, distribution, and adhesion to the polymer matrix. The results indicated that composites from HDPE resins with a lower MFI yielded a better dispersion of the wood waste. During processing was observed, reduce the MFI and better dispersion of the polymer matrix, which positively influenced some of the mechanical properties analyzed in the study.

In this study, mesoporous manganese oxide-titanium dioxide (Mn2O3/TiO2) nanocomposites have been synthesized following sol-gel method. Different molar ratios of Mn/Ti were evaluated and MT2 (5:1) showed the best photoactivity as well as carrier transport properties. The Langmuir–Hinshelwood model was delineated to calculate the reaction rate which was found to be highest for MT2 (min-1). Several parameters including pore size distribution, pore volume, adsorption isotherms have been analyzed as per Brunauer–Emmett–Teller (BET) method. That was attributed to the high surface area (121.81 m2/g). The space charge limited current (SCLC) theory was employed to calculate the mobility and transit time. MT2 showed the highest carrier mobility (326×10–7 m2 V-1s-1) and lowest transit time (0.08×10–5 s) which are desirable for efficient photoactivity.

The paper presents the results of tribotechnical tests of polymer composite materials based on polytetrafluoroethylene (PTFE) and carbon fibrous activated material UVIS-AK-P (SPC UVIKOM LLC) depending on the contact pressure in dry and boundary friction modes in various oils. I-20A industrial oil, Siboil TAD-17u transmission oil, and Rosneft Gidrotec HLP 46 hydraulic oil were used as liquid lubricants for the friction of polymeric materials. For tribotesting, a polymer composite with a content of 5 % wt. UVIS-AK-P, obtained using sequential mixing of filler with PTFE and the technology of joint activation of components in a planetary mill, is the most wear-resistant material according to the results of previous studies. It has been established that despite the heavy wear at increased bearing pressure during dry friction, unfilled PTFE does not undergo plastic deformation and maintains a low coefficient of friction practically unchanged. It has been found that the friction coefficient passes through a minimum during dry friction of a composite with CF at a load of 350 N. It is associated with the transition of the elastic contact of the interacting elements of the surfaces of the metal-polymer tribosystem to the plastic one with increasing load. During friction of PTFE in a lubricating oil environment, a significant decrease in mass wear, friction coefficient and temperature in the contact zone are observed due to the formation of secondary structures on the friction surfaces and the significant flexibility of PTFE. This increases the actual area of the tribocontact, which reduces the value of real normal contact stresses. During friction of polymer composite materials in the environment of lubricating oils, a decrease in the friction coefficient and the area of the friction track by 1.7-2.7 times was recorded as well. Deformations, groove formation and mass wear were not observed. It has been revealed that the greatest effect of increasing the wear resistance and permissible friction load and lowering the temperature in the friction zone of PTFE and composite is observed when using Siboil TAD-17u transmission oil. This is due to the presence of special antifriction additives in this oil brand and a decrease in the actual contact of the working surface of the polymer material with the lubricant, which helps to reduce the intensity of the destructive process in the surface layer while contacting with the lubricant.

This study focuses on the evaluation of the effects of incorporating a thin layer (‘paper’) of Graphene nanoplatelets (GnP) between the lamina on the processability and out-of-plane performance of glass fiber composites for EMI shielding applications. Various thicknesses of GnP paper (50, 120, and 240 µm) were embedded within layers of glass fabric for subsequent resin infusion. The out-of-plane failure surfaces were evaluated using a purpose-built fixture. In all experiments, the separation was observed within the graphene layers of the GnP paper rather than at composite/GnP interface. In comparison to pristine samples, decreases of 252%, 305%, and 386% respectively were recorded in the out-of-plane strength of embedded GnP papers. Numerical simulations were completed using a bilinear traction separation law based on the cohesive zone modeling approach. All composites were tested for electromagnetic interference (EMI) shielding properties. The EMI shielding was improved significantly by embedding GnP paper within glass fiber composites.

A novel theoretical approach, which yields a nonlinear differential equation for the mechanical properties of fiber‐filled composites as a function of the volume fraction of the filler and the fiber orientation, is shown. Furthermore, the transfer to polymer solutions is shown and gives a physical explanation for various well‐known empirical relations and numerical values including the Huggins constant and the exponent of power–law molar mass dependence of the polymer melt viscosity.

The saturation magnetization of composites of carbon nanotubes and CoFe2O4 (CFO) magnetic nanoparticles synthesized through a novel one-step process in the presence of a surfactant (sodium dodecyl-benzene-sulfonate) show significant increase, to 208 emu/g. This value of saturation magnetization of the composite is a factor of 3.3 higher than pristine CFO nanoparticles. This is the first time such a remarkable magnetic behavior of CFO/ carbon nanotubes composite is presented. The increased magnetism is attributed to the proximity effect between uniformly distributed ferromagnetic CFO nanoparticles on the surface of carbon nanotubes and hybridization of the π -electronic states of carbon and the 3d-bands of CFO. Scanning electron microscopy images confirm uniform and dense distribution of CFO nanoparticles on carbon nanotubes. Magnetic force microscopy images confirm the formation of uniformly distributed magnetic stripe domains. The sample was characterized at ambient using X-ray diffraction, Raman Spectroscopy, atomic force microscopy, scanning electron microscopy, scanning transmission electron microscopy, and high-resolution transmission electron microscopy. Magnetic properties were characterized by magnetic force microscopy and magnetometry using vibrating sample magnetometer.

Dense ceramic samples based on SiC were obtained by hot pressing. We used the Use of silicon carbide powder as the initial components of SHS, due to the spherical shape of the particles, allows obtaining a denser workpiece. The reinforcing component in the form of silicon carbide fibers is obtained by siliconizing carbon fabric with SiO vapours. The phase composition of SiC fibers obtained by silicification by SiO vapour was determined. The properties of the obtained SiC/SiCf composites were studied: density 3.20 g/cm3, strength 520 MPa (for monolithic ceramics 390 MPa), the value of the crack resistance coefficient 5.9 MPa-m1/2.

Effective methods are proposed for approximating the kinetic processes of formation of physical and mechanical characteristics of composite materials for solving problems of both single-criterion and multi-criteria optimization of their structure and properties. The approximation of kinetic processes on a given interval with the definition of partial intervals of the maximum length approximation is considered in detail. An approximation algorithm on cubic splines is given. To determine the transfer functions of composites, as dynamic systems with many inputs and outputs, it is recommended to use Laguerre polynomials. The possibility of a cognitive approach is also not excluded with the direct selection of the form of the approximating function.