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In order to improve the mechanical properties of sisal fiber-reinforced polypropylene composites, the sisal fibers were grafted with poly(amidoamine) dendrimer and the effects of grafting generations on the mechanical properties of composites were studied. The results reveal that the tensile, flexural, and impact strength of the composites are improved considerably with the poly(amidoamine) dendrimer grafting treatment. For the 2.0 generation treatment with the poly(amidoamine) dendrimer, the tensile, flexural, and impact strength of the composites at 30 wt% fiber loading increase by 29%, 13%, and 54%, respectively. However, the thermal and mechanical properties of the sisal fibers decrease after prolonged grafting treatment.

This paper presents a complex variable solution for the effective transport properties of composites with a doubly-periodic array of fiber pairs. By using the centrosymmetry of the problem, the method of Rayleigh and Natanzon-Filshtinsky's approach can be simply extended to the problems with two fibers per unit cell. The infinite system constructed in this paper only slightly complicates Rayleigh's system for the problems with one fiber per unit cell. Approximate analytical formulae of the effective transport properties for different fiber-pair arrays are obtained. The influence of pairwise interaction in fiber pairs on the effective transport properties is discussed in the numerical examples. As a special case of a doubly-periodic array of fiber pairs, effective transport property of composites with a triangular array of fibers is obtained. The obtained approximate analytical formulae are written in a concise form with good accuracy, thus are convenient for engineering application in most cases, except for those approaching the limit case of percolation when the perfectly conducting fibers become touching. Besides the square array and hexagonal array, the triangular fiber array (similar to carbon atom arrangement in graphene) is another special symmetric fiber array which results into transversely isotropic effective property. Therefore, the present solution for the triangular array is an extension of those for the square array and hexagonal array. The comparison of the results for the three symmetric fiber arrays reveals that the triangular fiber array has the highest conductivity. In addition, accuracy of the present solution is analyzed in the numerical examples.

Demand for lightweight and strong structures made of composite materials has increased tremendously over the past few years. This necessitates to fully exploit the properties of composite materials. It is important to understand the behavior of composites under different environmental conditions in order to take full advantage of its properties as their behavior is different from conventional materials (metals, nonmetals etc.). Glass fiber reinforced polymer composites are being used in multiple machines from bicycles to aircraft and to space ships. However, certain factors like environmental exposure and moisture absorption effects the mechanical properties of composites, like tensile and flexural strength, which require a thorough investigation. Therefore, in this paper moisture absorption effects on mechanical properties (tensile and flexural) of two categories of glass fiber (9 oz, 18 oz) epoxy laminate composites are analyzed. Fickian model has been used to find out moisture absorption rate and diffusion coefficient. Both configurations were put to three different environmental conditions, which are open environment, water, and kerosene oil, for a specified set time period. One set of specimen of both configurations was tested right after fabrication, and served as benchmark for rest of the specimens, which were put to environmental exposure. After completion of exposure period, specimens were tested and change in mechanical properties (tensile and flexural) were compared with benchmark, and after analysis it was found that 18 OZ glass fiber is less effected in term of environmental exposure and moisture interaction as compared to 9 OZ glass fiber.

The application of natural fibers as reinforcement material in composites can make an important contribution toward a more sustainable bio-based economy. To use these natural fibers, they need to be released from the stem. Traditionally, this is realized by dew retting. However, there are some disadvantages to this retting procedure. Due to changing weather conditions, it is quite difficult to guarantee a good and consistent fiber quality. Replacing the traditional retting process by a biocatalytic process may resolve these issues through application of a combination of pectinase and hemicellulase activities. In this context, several strategic pectinase and hemicellulase activities were blended. Flax fiber fineness and mechanical properties of resulting unidirectional fiber–epoxy composites were studied after treatment of flax stems with these strategic enzyme combinations. Characterization of fiber fineness showed a higher percentage of fiber widths smaller than 100 µm after combined treatment with two enzymes (44.7%), and the percentage was even higher after some combinations with three enzymes (51.2%). Assessment of mechanical properties of composites showed no significant differences in tensile or transverse properties for combined enzymatic treatments. Fiber properties were back-calculated from unidirectional flax fiber–epoxy composites and a Young’s modulus of 88 GPa and a tensile strength of 865 MPa were observed. Enzymatic extraction resulted in the achievement of similar results as dew retting concerning mechanical composite performance and fiber fineness.

The procedure for obtaining of composites based on unsaturated polyester resin (UPR), synthe-sized from waste poly(ethylene terephthalate) (PET), and zirconium carbide with improved dynamical-mechanical and thermal properties is shown in this study. UPR resin, which is synthesized by catalytic depolymerization of waste PET using propylene glycol, is used as matrix for composite production. To improving the mechanical and thermal properties of UPR matrix, the nano-scaled ZrC is added in 10 wt% amounts. Homogenization of added ingredients is done using mechanical stirrer, afterwards the resulting slurry is poured into the specially prepared teflonic mold with standard dimensions. Struc-tural characteristics of UPR resin and ZrC particles are confirmed via Furier Transform-Infrared (FT-IR) Spectroscopy. Examination of mechanical and rheological characteristics of composites is per-formed using tensile test measurements, Shore A hardness as well as dynamical-mechanical analysis (DMA). Thermal properties of composites are determined using UL-94 vertical test.

The research is devoted to composites based on magnesium binders, which is very perspective building material in the modern construction industry. Magnesium based binders have better compatibility with organic fillers comparing to traditionally lime binder cement [1]. In this investigation two magnesium-based binders are used, such as magnesium chloride and magnesium sulphate. The aim of this study is to investigate the physical, mechanical and durability properties of composites based on magnesium binders, such as density, compressive strength, thermal conductivity and capillary water absorption, and to obtain magnesium binder that could be used to produce foamed concrete. This can be done by improving the composition of the mixture. In this framework properties of magnesium binders are analysed and how these binders can affect to the properties of magnesium based composites.

The goal of this research project was to evaluate and compare the effect of fabric architecture on the processing and properties of composites made by Vacuum Assisted Resin Transfer Molding (VARTM). The fabric architectures investigated included plain weave, satin weave, and warp-knit unidirectional. The fiber types included E-glass and standard modulus carbon fiber. Flat panels were fabricated with a lab scale VARTM process using an epoxy resin system. Fabric plies were cut to 45 cm x 30 cm (18 in. x 12 in.), and the number of plies used depended on the fiber areal weight of each fabric to produce panels of similar final thickness. The speed of resin infusion was recorded by visually monitoring the flow front which was visible through the bag. Fiber volume fraction was evaluated using thickness measurements, and porosity was investigated via optical microscopy. Mechanical testing was performed via tensile and 3-point flexure. The results showed the fabric type had minimal effect on the infusion speed with the exception of the plain weave and satin weave fiberglass. From the mechanical testing results, there are many comparisons made of the modulus, strength, and strain-to-failure results, for example carbon vs. glass, unidirectional vs. woven, tensile vs. flexure. The rule of mixtures was able to predict some but not all of these properties. The results, which are discussed in detail herein, illustrate the main advantage of selecting carbon vs. glass in stiffness driven applications.

The mechanical and physical properties of wood-plastic composites (WPCs) were determined as function of different contents of nanoclay, talcum, and calcium carbonate as filler. It appears that the specimens made with 7 wt% calcium carbonate content resulted in the highest strength values. The modulus of rupture of the samples linearly increased with increasing amount of filler. The WPCs specimens having 9 wt% nanoclay showed the lowest dimensional stability in the form of water absorption and thickness swelling. An addition of 3 wt% talcum content also presented the highest cooling temperature and crystallization. Content of 7 wt% of calcium carbonate was determined as optimum level of filler regarding overall mechanical and physical properties of WPCs specimens.

Y-zeolite was first modified by means of ions exchange with Al, Ca and Na, respectively. The modified materials were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma optical emission spectrometry (ICP-OES). Gas sensors were fabricated by SnO2 and coating Y-zeolites on the outside of SnO2 surface, respectively. It was found that the responses of the composites of all types of zeolite- and SnO2-based sensors became lower comparing with that of the pure SnO2-based one response of SnO2 sensor to ethanol vapor. It indicates a suppression effect of zeolites on the response to ethanol vapor. In contrast, the response of the composite-sensing materials of the modified Y-zeolite/SnO2-based sensors except the Ca-modified one to acetone indicates a significantly improved response, 2–3 times higher than that of pure SnO2-based sensor which is smaller than the one of SnO2 sensor. The possible mechanism of the effects of the Y-zeolites on the response of the sensors has been discussed.

The dependence of the impact toughness of composite materials on various parameters, such as density, type of weaving, width of fibers and the number of layers of fiberglass and basalt fabric in the composite has been studied. The change of impact toughness of composite materials at introduction into a matrix of polymer of carbon nanotubes (CNT) in various concentrations is investigated. The increase of impact toughness at concentration of dispersed unoriented CNT in the composite matrix of the order of 3% was found.

Hyperbranched polyester is effective for enhancing molecular bond strength and improving the mechanical behavior of nanofilled polymers. This study examines the dielectric and polarization relaxation characteristics of epoxy resin composites filled with nanosilica 30 nm in diameter, which is treated by terminal carboxyl hyperbranched polyester. TEM and SEM analysis indicate that the nanosilica surface is grafted with a functional polymer layer ranging in thickness from several to tens of nanometers, and the nanosilica agglomeration in epoxy resin is remarkably inhibited. Measurements of thermally stimulated depolarization current and differential scanning calorimetry show that, deep traps with an energy of 1.09 eV are present in the nanocomposites, and the glass transition temperature (Tg) is increased by 11 °C at most at filler concentrations from 1 to 7 wt%. Moreover, the room-temperature relative permittivity and dielectric loss factor of the composites at 50 Hz are decreased by 0.22 and 1.3‰, respectively. Conductivity at 10 mHz to 1 kHz and dc conductivity are also significantly decreased when the operating temperature is below Tg. The polarization relaxation process of the nanocomposite is dominated by regional carrier migration, interfacial and dipole polarization. The relaxation frequency of dipole polarization at high temperature (>Tg) is transformed to satisfy the Vogel–Tammann–Fulcher law. This research suggests that both the dielectric and the polarization relaxation properties of the epoxy resin composites can be modified by filling hyperbranched-polyester-treated nanosilica, because it enhances the bond strength of the inorganic–organic interface and enlarges the molecular scale of the composites via cross-linking reactions.

Polyethylene m-Y2O3:Eu3+ composites (PECs) containing 0.32, 0.77, and 1.79 wt% of well-dispersed sphere-like m-Y2O3:Eu3+ nanoparticles were obtained by in situ polymerization in the presence of a titanium-magnesium catalyst (TMC). TMC was synthesized by sequential deposition of organic magnesium and TiCl4 on m-Y2O3:Eu3+ that had been previously dehydroxylated at 650 °C. Detailed photoluminescence properties of the obtained composites as a function of m-Y2O3:Eu3+ content were investigated in combination with UV–Vis and IR spectroscopy data. It was shown that Eu3+ ions in monoclinic Y2O3 lattice are responsible for the high red emission of the composites. The effect of the РЕС host on the luminescence properties of m-Y2O3:Eu3+ was revealed. The obtained chromaticity coordinates with improved red color (0.653, 0.347) and high absolute luminescence quantum yield up to 23% make РЕСs potential promising materials for luminescent applications.

The importance of nonlinear dielectric and magnetic materials for developing nonlinear transmission lines for high power microwave applications necessitates characterization of the behavior of composites containing these inclusions at microwave frequencies. Here, we apply commercial finite element software and various effective medium theories (EMTs) to predict the effective permittivity and permeability of composites containing inclusions with volume fractions of up to 25 % barium strontium titanate (Ba2/3Sr1/3TiO3, BST) and/or nickel zinc ferrite (Ni1/2Zn1/2 Fe2O4, NZF) in a silicon-based host from 1 to 4 GHz. The modelling results suggest that limited agglomerations of high dielectric contrast BST inclusions may create effective higher aspect ratio inclusions that may enhance the effective dielectric properties of BST composites. For the three-phase composites containing BST and NZF in polydimethylsiloxane (PDMS), we first treated the NZF and PDMS as an intermediate “host,” which we subsequently mixed with BST inclusions to construct an effective two-phase EMT. The modelling results agree with the measured permittivity and permeability of the two- and three-phase composites in the linear region and may be used as predictive tools to guide composite design.

A novel inter-fiber failure criterion of composites based on micro-scale failure mechanism is proposed in this paper. The composites failure is determined by the failure of constituents near interface, where the micro-scale stress is “risk”. A cross-scale stress calculation formula is derived according to inclusion theory, and proved precise by comparing with the micro-scale simulation results. The accuracy of the failure criterion is verified through the experimental results and simulation results of micro-scale model under biaxial stress . The failure criterion considers the micro-scale stress distribution, fiber volume fraction and elastic properties of constituents, and can give precise predictions on the strength and failure angle of fiber reinforced polymer composite .

In order to solve the problems of heavy overload, poor buffer performance of cushion and low reliability of fuze in high-speed penetration process of the projectile, this paper proposes a composite structural cushion using foamed aluminum and rubber. Through the establishment of the projectile model with different material cushions, the Ls-dyna software is used to simulate the high-speed penetration process and analyze the fuze acceleration curve. The results show that the composite cushion has a significant buffering effect in the process of high-speed penetration, which can reduce the impact overload of fuze and improve the reliability of fuze.

Проблематика. Виникнення міжфазової взаємодії, геометричні обмеження простору полімеризації полімеру, зростання вільного об’єму полімеру при додаванні неорганічного компонента – все це впливає на фізико-хімічні та механічні властивості композитів. Однак взаємозв’язок вихідних компонентів із властивостями композита має індивідуальний характер і потребує екс­периментального вивчення. Мета досліджень. Дослідження впливу складу гібридних органо-неорганічних композитів (ГОНК) на основі системи a,w-диметакрилоїл (тридиетиленоксидтерефталат) (МГФ-9)–тетраетоксисилан (ТЕОС) на їх термомеханічні і деформаційні властивості та молекулярну структуру. Методика реалізації . Полімер-кремнеземні композити отримували методом фотоініційованої полімеризації у блоці з використанням лазерного інтерферометра та золь-гель-методом. Термомеханічний аналіз проводили на приладі для визначення теплостійкості полімерних матеріалів “Heckert” і розраховували значення характеристичних параметрів досліджених композитів системи МГФ-9–ТЕОС. Деформаційні властивості композитів визначали на консистометрі Хепплера, розраховуючи параметр поверхневої мікротвердості (конічної точки текучості). Результати дослідження . Підтверджено залежність деформаційних і термомеханічних властивостей композитів від співвідношення органічної та неорганічної складових системи . Висновки. Введення неорганічного наповнювача в матрицю полімеру сприяє покращенню термомеханічних і дефор­маційних властивостей композитів. Максимальні термомеханічну стійкість і міцність має композит МГФ-9:ТЕОС = 90:10 % об.

In this work, graphene was modified by the grafting of poly(vinylidene fluoride) (PVDF) using Friedel-Crafts reaction to form PVDF-grafted graphene (PGG) filler, which was confirmed by transmission...

New foaming method, enhanced by microwave irradiation, was elaborated and applied to obtain porous poly(vinyl chloride) and its composites with fine cell structure. The so called “thermal runaway” effect was observed during the heating of poly(vinyl chloride) under microwave irradiation. The temperature of this effect decreases as a result of additives incorporation into polymer matrix. Microwave irradiation allowed effective heating of extruded poly(vinyl chloride) and its composites with carbon black (CB) filler, behind the extruder head and decomposing azodicarbonamide (ADC) to obtain porous products. The use of CB additive to poly(vinyl chloride) significantly increased its ability to be heated under microwave irradiation as well as improved the cell structure and decreased the apparent density of final products. Among additionally used fillers (1 wt%) the montmorillonite caused the apparent density decrease of foamed materials ca. 10%, however beneficially influenced on the quality of cells structure, giving the products with isotropic cells and the highest cell density as well as keeping the tensile strength on similar level as in the case of the materials with CB and ADC only.

Hydroxyapatite (HA), obtained from bovine bones, was successfully reinforced with hexagonal boron nitrite (h-BN). h-BN/HA composites, with BN content up to 1.5 wt %, were sintered at various temperatures between 1000 and 1300°C, in air. Well-sintered samples were obtained after sintering at 1200 and 1300°C. The presence of h-BN contributed to dense, fine, and well-crystallized microstructure. The results of X-ray diffraction analysis and FT-IR spectroscopy showed that the produced composites comprised biphasic β-TCP/HCA (HCA: carbonate partially substituted HA). High values of mechanical properties were achieved, namely compression strength 155 MPa for the sample 0.5% h-BN/HA and Vickers microhardness of 716 HV for the samples 1.5% h-BN/HA, both sintered at 1300°C. U2OS human bone osteosarcoma proliferation and cell viability showed no adverse effect in the presence of h-BN/HA, suggesting the potential use of the produced materials as safe biomaterials in bone tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2384-2392, 2018.

This study investigated the effect of milk packet waste (Tetra Pak™) and maleic anhydride–grafted polyethylene (MAPE) on the physical and mechanical properties of wood–plastic composites. Tetra Pak was used in four levels (0, 10, 20, and 30%) and MAPE was applied in two levels (0 and 3%). The morphology of the samples was characterized using the scanning electron microscope technique. The results showed that adding Tetra Pak and MAPE to samples increased the flexural strength and modulus of elasticity and reduced 24-h water absorption and thickness swelling. The results were also confirmed by electron microscopy images.

Microstructure and mechanical properties of the 316L steel composite reinforced with TiB2phase were examined. The test materials were obtained by SPS technique from powders. From testing of the mechanical properties it follows that the optimum temperature for the fabrication of 316Lsteel-TiB2composites by SPS is 1100°C. Studies have also proved that the critical content of TiB2phase in steel matrix should not exceed 6vol%. Above this level, the plastic properties of the composite become unstable and strongly dependent on the time of sintering.

The carbon fiber based composites: carbon fiber reinforced plastic and 3D carbon fiber reinforced carbon composites were exposed to the Nd3+: YAG laser beams (1064 nm). Experimental parameters for the interaction of the laser beam with 1.5 Hz pulse frequency and with pulse duration 0.7 ms varied: energy density between 128 and 1915 J cm(-2), pulse energy from 1 to 3 J and mean power in the range between 0.4 and 6.5 kW. Apparently, the energy absorbed by the composite samples was mainly converted into thermal energy, causing a range of damages, from instantaneous evaporation to cracking and melting, which resulted in a crater-like damage. Program ImageJ was executed for quantitative analysis of generated damages based on micrographs obtained by SEM and light microscopes. Obtaied results enable identification of the laser induced changes in the material. (C) 2017 Elsevier Ltd. All rights reserved.

Structural, mechanical, and thermal properties of polyphenylene sulfide (PPS) filled with Al-Cu-Fe quasicrystals particles were studied. It was shown that the introducing of quasicrystalline fillers into the polymer matrix results in the increase in Young’s modulus, hardness, and toughness of the polymer. Quasicrystalline fillers can improve thermal properties of PPS, including heat resistance index, Vicat softening temperature, thermal diffusivity, and thermal conductivity.

Poly(lactic acid) (PLA)/polypropylene (PP) blends composites were prepared by incorporating 3 wt.% of copper modified montmorillonite (MMT-Cu2+), obtained using cation exchange in a CuSO4 solution, and 10 wt.% of polypropylene-graft-maleic anhydride (PP-g-MA) as a compatibilizer then varying the PLA content until 50 wt.%. These materials were subjected to several investigations such as X-rays diffraction, dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and tensile and environmental tests. The DMTA analysis showed that the glassy PLA high stiffness and the PP crystalline phase compensate the decrease in the storage modulus occurring during the PP and PLA glass transitions, respectively. The variations of tan δ revealed no changes on the PP and PLA phases glass transitions temperatures which indicate the immiscibility of the two polymers, as supported by DSC analysis. Blends composites SEM micrographs stated the immiscibility of...

Contributions of 15 convex polyhedral particle shapes to the overall elastic properties of particle-reinforced composites are predicted using micromechanical homogenization and direct finite element analysis approaches. The micromechanical approach is based on the combination of the stiffness contribution tensor (N-tensor) formalism with Mori–Tanaka and Maxwell homogenization schemes. The second approach involves FEA simulations performed on artificial periodic representative volume elements containing randomly oriented particles of the same shape. The results of the two approaches are in good agreement for volume fractions up to 30%. Applicability of the replacement relation interrelating N-tensors of the particles having the same shape but different elastic constants is investigated and a shape parameter correlated with the accuracy of the relation is proposed. It is concluded that combination of the N-tensor components of the 15 shapes presented for three values of matrix Poisson's ratios with the replacement relation allows extending the results of this paper to matrix/particle material combinations not discussed here.

In this work, the effect of moisture absorption on the mechanical properties of particulate composite materials is studied. Moisture absorption constitutes a main parameter affecting the thermomechanical behaviour of composites, since it causes plasticization of the polymer matrix with a concurrent swelling. In the present work, the influence of water absorption on the flexural properties of particle-reinforced composites was thoroughly investigated. It was found that during the process of moisture absorption there exists a variation of the flexural properties closely related to the degradation of the mechanical behaviour of the composite, as well as the percentage amount of moisture absorbed. Experiments were carried out with composite made of epoxy resin reinforced with low-content iron particles. The variation of ultimate stress, breaking strain, deflection, elastic modulus and Poisson ratio due to water absorption was examined.

3D printing is the process where layers of materials are deposited to make structures of complex geometries. 4D printing is a process that combines 3D printing with the application of some activating agent in order to change the shape of the manufactured part after the process, e.g. the flat structure will change its shape to take up the desired complicated shape such as “curved” or “S” shaped. As such the 3D printing process does not have to spend time to print the intricate parts, and the process can be faster. The requirement for 4D printing is that materials with special characteristics that are responsive to an activating agent need to be used. 4D printing of composites utilizes the same concept of 4D printing, except that the materials used are long fiber composite materials. 4D printing of composites utilizes the shrinkage of the matrix resin, and the difference in coefficients of thermal contraction of layers with different fiber orientations to activate the change in shape upon curing and cooling. This behavior can be used to make parts with curved geometries without the need for a complex mold. As such manufacturing of pieces of curved shapes can be fast and economical. However, the degree of shape changing depends on the material properties, the fiber orientation, the lay up sequence and the manufacturing process. This paper presents the results obtained from a study on the effects of these aspects on the shape of the curved parts.

Aiming to systematically convert post-consumer plastics in building materials, we compounded recycled high-density polyethylene and sugarcane bagasse. We ranged the polymer/filler ratio from 100/0 to 60/40, and assessed the properties using optical microscopy, water absorption test, adhesion by tape test, low-field nuclear magnetic resonance, dynamic-mechanical analysis, and wide-angle X-ray diffractometry. The optical microscopy of the triturated bagasse showed the reduced and heterogeneous fiber sizes. The absorption and adhesion test showed that the polymer more heavily filled with bagasse can better absorb and anchor paint with organic solvent base. The dynamic-mechanical analysis and wide-angle X-ray diffractometry led us to believe that the bagasse fibers somehow structured the amorphous region amongst the crystallized lamellae of the polymeric matrix. We concluded that these composites have interesting properties to produce building materials.

Composites of polypropylene (PP) and PP blended with maleic anhydride-grafted polypropylene (MAPP) reinforced with short glass fibers were prepared via extrusion compounding and injection molding techniques. The fiber length did not significantly change irrespective of the presence of MAPP after compounding and injection molding. However, the tensile strength of PP/fiber showed significant improvement after MAPP addition. The interfacial shear strength between PP and fiber increased with the addition of MAPP. Examination of the failure surface of a dumbbell specimen after tensile testing confirmed that the fiber highly orientated in the flow direction in the PP/MAPP matrix. The tensile strength enhancement was attributed to the improvement of the interfacial shear strength between PP and fiber. Moreover, in the injection molding process, there was high orientation of the fiber in the flow direction when there was MAPP. We concluded that the presence of MAPP causes increased orientation of the fiber.

While grain conductivity of lithium titanium phosphate materials (LTP) is high, the total conductivity is relatively low due to high resistant grain boundary phase. The work demonstrates that this resistance can be substantially reduced by helps of LiI. For this purpose a series of the LTP–LiI composites were formed employing mechanical ball–milling. X–ray diffractometry, thermogravimetry, impedance spectroscopy, scanning electron microscopy and density methods were used to characterize obtained materials. A maximum enhancement of total ionic conductivity at 30 °C was recorded for the LTP containing 8 wt.% of LiI (7.3 × 10 − 6 S·cm − 1 comparing to 1.5 × 10 − 8 S·cm − 1 for pure LTP).

In the current research a statistical micromechanical approach for the determination of the mechanical properties of composite materials is proposed. The proposed method is mainly based on the well-known periodic homogenization scheme. The methodology implements multi-step multiscale approach to calculate the mechanical properties of composite materials where the statistical characteristics (e.g. size, aspect ratio, orientation) of the reinforcing phase are known as probability distribution functions (PDF). The calculations start from Unit Cell I which resembles the microstructure of material at the lowest length scale and continue until the largest fiber is considered in the final unit cell setting. The results of the presented theory are compared with experimental data on composite materials which show that good estimates of the elastic moduli can be achieved by using statistical multi step homogenization technique.

The possibility of reinforcing the Al/Al2O3 laminated cermet matrix with metal rapidly solidified alloy fibers (steel, titanium, and aluminum), as well as discrete duralumin chips, is shown. The maximal reinforcing effect was attained when using titanium and steel fibers with their content of 20 and 10 vol %, respectively, due to the implementation of several energy-intensive destruction mechanisms. Reinforced composites are characterized by the following properties: ρ = 2.30–2.85 g/cm3, σbend = 180–250 MPa, K 1c = 7.5–15 MPa m1/2, and KCU = (18–35) × 103 J/m2. The Al/Al2O3–Ccoke.residue has ρ = 2.21–2.23 g/cm3 at a very low sliding friction coefficient of 0.17 (the counterbody is a ball made of steel ShKh-15 under a load of 1 N). The oxide-adhesion bond type, which makes it possible to remove spent grains from the grinding work zone and implement the self-sharpening mode, is formed for the “Al/Al2O3–fused alumina grains” composite. The material that contains kaolin fibers is ultra-light-weight ceramic insulation (0.25–0.5 g/cm3), λ = 0.07–0.2 W/(m K) in the 20–1000°C range. The material including alumina spherulites combines rather high hardness (σbend = 10–50 MPa) and porosity (42–52%) and has increased thermal stability due to the rapid elimination of the temperature gradient on structural elements having a micrometer-size cross section.

Samples of composites, in which ethylene-tetrafluoroethylene copolymer is used as a matrix and quasicrystalline Al−Cu−Fe powder as a filler with 0, 1, 2, 4 and 8 vol % concentrations, are prepared. Electron microscopy studies of the sample structure are carried out. The influence of the filler on the crystallinity and temperatures of sample melting and destruction is investigated. The mechanical and tribological properties of the samples are tested. It is found that an increase in the filler content changes neither the mechanical nor thermodynamic characteristics of the material but significantly improves the tribological characteristics. The friction coefficient decreases twice at 1 vol % of the filler and the wear resistance increases by 40 times at 8 vol %. Experimental data indicate the probability of good adhesion of the filler particles to the fluoropolymer matrix. The composites under investigation may be of interest as promising materials for polymer friction bearings.

Bioactive glass (BAG)/Poly (Lactic Acid) (PLA) composites have great potential for bone tissue engineering. The interest in these materials is to obtain a scaffold with tailorable properties bringing together the advantages of the composites’ constituents such as the biodegradability, bioactivity and osteoinduction. The materials studied are PLA/13–93 and PLA/13-93B20 (20% of SiO2 is replaced with B2O3 in the 13–93 composition). To characterize them, they were dissolved in TRIS buffer and Simulated Body Fluid (SBF) in vitro. Over the 10 weeks of immersion in TRIS, the ion release from the composites was constant. Following immersion in SBF for 2 weeks, the hydroxyapatite (HA) layer was found to precipitate at the composites surface. By adding Boron, both these reactions were accelerated, as the borosilicate glass dissolves faster than pure silicate glass alone. Polymer degradation was studied and showed that during immersion, the pure PLA rods maintained their molecular weight whereby the composites decreased with time, but despite this the mechanical properties remained stable for at least 10 weeks. Their ability to induce osteogenic differentiation of myoblastic cells was also demonstrated with cell experiments showing that C2C12 cells were able to proliferate and spread on the composites. The Myosin Heavy Chain and Osteopontin were tracked by immunostaining the cells and showed a suppression of the myosin signal and the presence of osteopontin, when seeded onto the composites. This proves osteoinduction occurred. In studying the mineralization of the cells, it was found that BAG presence conditions the synthesizing of mineral matter in the cells. The results show that these composites have a potential for bone tissue engineering.

The features of changes in the real and imaginary parts of the complex permittivity of the samples with CdZnTe crystallites in the frequency range 10–103 Hz of the electric field in the absence of exposure to electromagnetic radiation are obtained. It has been shown that composites without these crystals have a higher diffuse reflection coefficient. Under the influence of non-monochromatic light, an increase in the changes in the complex permittivity of the samples with increasing frequency of the measuring field was detected. Moreover, the changes are larger for the samples with the largest crystallite size. The low inertia of changes in the dielectric parameters of the samples under the influence of non-monochromatic illumination is established. Samples with ZnSe (Al) crystallites are characterized by significant changes in the complex permittivity under the influence of non-monochromatic illumination in the frequency range 103–104 Hz. Negative changes of this parameter are especially unusual. The peculiarities of the spectral dependences of the constituents \( \Delta\upvarepsilon_{\text{ef}}^{'} \) and \( \Delta\upvarepsilon_{\text{ef}}^{''} \) complex permittivity of the structures, measured at a light intensity of 10 mW/cm2, have been established. The changes in the magnitudes of the increments of the real and imaginary components of the complex permittivity under the action of X-Ray radiation with a dose rate of 200 mR/h at different frequencies of the electric field are investigated and their characteristic features are determined. An analysis of the results from the point of view of non-equilibrium electronic processes in semiconductors is presented.

The rapid progress of nanotechnology triggers the development of nanomedicine. As the antimicrobial properties of nanosilver are well known, there is a huge interest in the synthesis of silver nanoparticles using environmentally-friendly methods. In this study we described the functional (rheological, mechanical, surface, structural) properties of gels and foils containing silver nanoparticles embedded in hyaluronan and hyaluronan-lecithin matrix prepared using the methods of green chemistry. The study showed that the addition of silver strengthened the structure of Hyal foil, but reduced the stretch of the sample and that lecithin weakened the mechanical properties of the composites. Also, the presence of nanosilver made the studied foils partially hydrophilic, while these with lecithin were more hydrophobic. The results of the study are significant for the adaptation of the investigated materials to their potential applications.

The life cycle of a product depends to a great extent on its reuse and ease of recycling. This work had developed of composite materials of reprocessed polypropylene composites with rice husk ash (RHA) and sugarcane bagasse ash (SBA) through the coextrusion and injection processes as main purpose. The polymeric matrix was reprocesed until six generations by the injection technique. The reprocessed PP was mixed in 80:20 proportions with respect to filler mineral, using maleic anhydride as coupling agent in a coextrusion machine. The new series of composite materials were analyzed thermal, mechanical, rheological and morphologically. The incorporation of ashes in the PP matrix achieved characteristics of improved tensile strength, conserving the thermal properties. For this reason, this work presents an alternative for the manufacture of composite materials from post-industrial waste.

Annotation This article presents an algorithm for finding the constants in the model of changing the thermoelastic properties of polymer composites. The calculation of the constants is based on the processing of the experimentally obtained data. Optimization methods are applied to minimize the discrepancy between the experimental data and the analytical dependence on the constants that need to be found. Also, a method was proposed for determining the constants in the model of density change during destruction. The paper analyzes the effect of high temperatures on the change in density and elastic modulus of composite materials. On the basis of this, an algorithm was constructed for calculating the change in elastic properties up to temperatures of thermal destruction and during thermal destruction. The error between theoretical modeling and experimental data did not exceed 5%.

The main objective of this work was to investigate the effect of natural additives with an animal and vegetable source in the form of (short fibers and particle) on the mechanical and thermal properties for epoxy. (wood dust, date palm fiber, cow bones and sheep wool) were selected as natural additives with different weight ratios such as (%5,%15,%25) reinforcements for the epoxy matrix based composites, which were produced by the hand lay-up technique. mechanical test such compression strength and thermal properties such thermal conductivity were carried out according to ASTM standards to characterized these composites. It was found that the mechanical and thermal properties can be increased or decreased depending on the type of material additives, its origin, as well as the weight percentage used.

In this study, two bio-based benzoxazines, PH-f and SA-f, were synthesized and used to prepare benzoxazine/chitosan (CS) composites of PH-f/CS and SA-f/CS and their corresponding curing products poly(PH-f)/CS and poly(SA-f)/CS. Differential scanning calorimeter (DSC) and Fourier-transform infrared spectroscopy (FTIR) spectra show that, compared with poly(PH-f)/CS, the formation of imine-linkages (C=N) between SA-f and CS accelerates the benzoxazine ring-opening reaction and lowers the curing temperature of SA-f/CS. Although poly(PH-f)/CS and poly(SA-f)/CS have lower thermal stability than corresponding pure polybenzoxazine, it is still high and their LOI values are >35, indicative of good flame retardancy. Due to the formation of C N bonds between SA-f and CS, the poly(SA-f)/CS composite has more regular surfaces and a more uniform pore distribution than poly(PH-f)/CS, with a specific area of 1.135 m2/g and porosity of 97.5%. The unique pore structure of the poly(SA-f)/CS composite gives it high adsorption capacity (reaching 95% for rhodamine B within 48 h), suggesting that it is a promising adsorption material.

After the transition of particles size from the micro to the nanoscale, the polymeric composites started to be produced by different types of nanomaterials and show better physical-chemical properties with multifunctional characteristics when compared to their conventional derivatives. In this context, nanocomposites based on carbon nanomaterials (CNMs) such as carbon nanotubes and graphene feature as cases of attractive unconventional materials for technological applications. An impressive number of works have been published, therefore the recent advances in polymeric nanocomposites based on epoxy and CNMs need to be addressed. Thus, this brief review is a useful guide to significantly update the state-of-the-art of these different composite systems, reporting their relevant improvements in thermal and mechanical properties over the past 10 years or more.