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This paper describes the abrasive wear mechanism of dispersed-filler epoxy-based composites, which includes the removal of anti-abrasive filler particles from the total mass of the substance as the matrix wears out. The disturbance of their equilibrium occurs through separation, shear, and rotation, depending on the parameters of the power loading circuit. At the same time, the force required to remove particles from the matrix is determined by their size, shape, spatial arrangement, internal adhesive strength of the particle–matrix system, area of contact with the matrix ("adhesion"), and physical, mechanical, and tribotechnical properties. [ABSTRACT FROM AUTHOR]

The adhesion strength of epoxy-binder—steel-fiber joints and the change of binder mechanical properties under multiple cyclic curing have been studied. It has been shown that the adhesion strength monotonically decreases with an increase in the number of cycles when the curing temperature is much higher than the binder vitrification point. In this case, the mechanical properties of the matrix are also decreased. Some possible mechanisms of the observed changes are also discussed. [ABSTRACT FROM AUTHOR]

In this work, the analysis of the formation processes of fiber composites with an epoxy matrix is carried out. Methods of their formation and arrangement of fibers are considered. The kinetics of curing of an epoxy binder is discussed in terms of the effect of the filler on it leading to the development of internal stresses in the composite. The mechanisms of volume relaxation and pore formation are outlined. Particular attention is paid to the impact of processing on the properties of fiber composites with an epoxy matrix. Problems and directions for further research of fiber composites with an epoxy matrix are outlined. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) functionalized curaua fiber (CF) has been shown to improve the mechanical properties and ballistic performance of epoxy matrix (EM) nanocomposites with 30 vol% fiber. However, the possibility of further improvement in the property and performance of nanocomposites with a greater percentage of GO functionalized CF is still a challenging endeavor. In the present work, a novel epoxy composite reinforced with 40 vol% CF coated with 0.1 wt% GO (40GOCF/EM), was subjected to Izod and ballistic impact tests as well as corresponding fractographic analysis in comparison with a GO-free composite (40CF/EM). One important achievement of this work was to determine the characteristics of the GO by means of FE-SEM and TEM. A zeta potential of −21.46 mV disclosed a relatively low stability of the applied GO, which was attributed to more multilayered structures rather than mono- or few-layer flakes. FE-SEM images revealed GO deposition, with thickness around 30 nm, onto the CF. Izod impact-absorbed energy of 813 J/m for the 40GOCF/EM was not only higher than that of 620 J/m for the 40CF/EM but also higher than other values reported for fiber composites in the literature. The GO-functionalized nanocomposite was more optimized for ballistic application against a 7.62 mm projectile, with a lower depth of penetration (24.80 mm) as compared with the 30 vol% GO-functionalized CF/epoxy nanocomposite previously reported (27.43 mm). Fractographic analysis identified five main events in the ballistic-tested 40GOCF/EM composed of multilayered armor: CF rupture, epoxy matrix rupture, CF/matrix delamination, CF fibril split, and capture of ceramic fragments by the CF. Microcracks were associated with the morphological aspects of the CF surface. A brief cost-effective analysis confirmed that 40GOCF/EM may be one of the most promising materials for personal multilayered ballistic armor. [ABSTRACT FROM AUTHOR]

• The coating resistance of EP-GCN/AEPS-Nb 2 O 5 nanocomposite was found to be 8.99E9 Ω.cm2. • The EP-GCN/AEPS-Nb 2 O 5 showed greater flame retardancy with PHRR (81 %) and 69 % (THR) reductions. • The EP-GCN/AEPS-Nb 2 O 5 coatings on steel controlled the dissolution of Fe to Fe2+ ions. • The superior hydrophobic behavior of EP-GCN/AEPS-Nb 2 O 5 coating was confirmed by its WCA of 161º. • The EP-GCN/AEPS-Nb 2 O 5 film displayed the enhanced adhesive strength (17.8 MPa). The inorganic nanofiller niobium pentoxide (Nb 2 O 5) was altered with [3-(2-aminoethylamino)propyl]trimethoxysilane (AEPS) and the resulting AEPS/Nb 2 O 5 was encased with graphitic carbon nitride (GCN) in pure epoxy resin (EP). The protection performance of mild steel coated with epoxy in the presence of various concentrations of GCN encapsulated in silanized Nb 2 O 5 was investigated using electrochemical techniques in a marine environment. A limiting oxygen index (LOI) test showed that GCN/AEPS-Nb 2 O 5 considerably enhanced the flame retardancy properties of the epoxy coating. The PHRR and THR values for EP-GCN/AEPS-Nb 2 O 5 significantly decreased by 81 % and 69 %, respectively, compared to those of pure EP, showing that the material is more flame-retardant. The results of salt spray tests showed that the addition of GCN/AEPS-Nb 2 O 5 enhanced corrosion protection and reduced water absorption. Even after 960 h of exposure to seawater, epoxy-GCN/AEPS-Nb 2 O 5 exhibited increased coating resistance of 8.99E9 Ω.cm2, according to the EIS measurements. According to SECM research, coated steel made of the EP-GCN/AEPS-Nb 2 O 5 nanocomposite has the lowest degree of ferrous ion dissipation (1.0 I/nA). According to the FE-SEM/EDX results, the decomposition products of silanized GCN were enhanced, generating a sturdy inert nanolayered coating. To prevent ions from penetrating the specimen, EP-GCN/AEPS-Nb 2 O 5 crystallizes into a strong, inert coating, has greater adhesive strength, and can endure prolonged immersion without losing its integrity. Therefore, the EP-GCN/AEPS-Nb 2 O 5 nanocomposite could act as a viable coating component in the automobile industry. [Display omitted] [ABSTRACT FROM AUTHOR]

The widespread use of polymer composite materials (PCM) leads to an increase in non-recyclable waste. This paper discusses the feasibility of recycling fiberglass with an epoxy matrix by solvolysis in ethanol under supercritical conditions. The solvolysis process completes successfully within four hours in an environment of a pure solvent containing 10% water at a temperature of 280 °C when the solvent passes into the supercritical state. The treatment time increases up to 10 h at a process temperature of 250 °C. When using a coordination compound of copper(II) chloride with organic chloride salt having 2,3,5-triphenyltetrazolium as the counterion, having the composition of (2,3,5-triphenyltetrazolium)2[CuCl4], the treatment time is reduced. The addition of the complex of 5% by weight makes it possible to completely remove the epoxy matrix at a temperature of 250 °C for two hours. The products separated from the solvolysis liquid were studied by infrared spectroscopy. The resulting fibers were examined by thermogravimetric analysis and scanning electron microscopy. The residual strength of the recovered fibers is 98%. Thus, the resulting fibers can be reused in the composite industry. Including both for the production of decorative products and for the production of structural products made of polymer composite materials.

In the present work, two types of composites were produced, both reinforced with 30 vol% of curaua fibers (CF). In the first type, only the fiber was functionalized with graphene oxide (GO), producing the GOCF/EM composite. While in the second, only the epoxy matrix (EM) was functionalized, producing the CF/GOEM composite. The objective of the work was to investigate the influence of functionalization with GO on the tensile properties of these produced composites. In comparison with the non GO-functionalized composite, as control CF/EM, the results revealed an increase in yield strength (64%), tensile strength (40%), Young's modulus (60%) and toughness (28%) of the CF/GOEM composite. The GOCF/EM composites for which the fibers were functionalized with GO also performed better than the CF/EM composite. The ANOVA and Tukey tests confirm this increase. As for ductility, within the standard deviation, no change was observed between samples functionalized by GO and those from the control. For the first time, comparing the results of the composites, it was demonstrated that a polymer matrix functionalized by GO offers superior tensile performance compared to the other types, keeping the same GO concentration in the composite. This fact is corroborated by the analysis of the corresponding fracture mechanisms. Preliminary results of composite with simultaneous functionalization of both fiber and epoxy matrix failed to present superior properties. This might be attributed to high amount of GO, which is apparently not a good reinforcement as the curaua fiber.

The article is devoted to the analysis of the structure and properties of fiber composites with an epoxy matrix. The issues of the formation of interphase layers, including those containing a skin layer made of polymer fibers, methods of their measurement and modification of the interfacial layer (coating, nanoparticle coating, grafting) are discussed. Mechanical properties are analyzed in detail, including the interfacial effect and the role of the matrix (the formation of a microphase structure during the curing of the matrix, the effect of the microphase structure on the mechanical properties of the cured matrix and application of nanoparticles). Thermal and tribological properties of composites are considered. It is proposed to use nanoparticles to modify the structure and properties of fiber composites. The problems and prospects for the development of research on fiber composites with an epoxy matrix are underlined. [ABSTRACT FROM AUTHOR]

The mechanical properties of carbon fiber-reinforced epoxy composites were identified by adding carbon-based nano-reinforcements, such as multi-wall carbon nanotubes (CNTs) and graphene platelets (GP), into the epoxy matrix by conducting suitable experiments. The main focus of this study is to compare the tensile modulus, tensile strength, flexural modulus, flexural strength, and thermal conductivity of carbon fiber-reinforced epoxy composites with nanoparticle reinforcement. The results revealed that adding CNTs and GP nanoparticles improved the mechanical properties compared to a pure carbon fiber-reinforced plastic composite. However, compared to CNTs, the GP’s addition has increased the mechanical properties of the CFRP composite. In addition, scanning electron microscopy (SEM) images were presented to explore the microstructural characterization of carbon fiber-reinforced nanoparticle-reinforced composites. Further, using numerical studies, the transverse modulus, major and minor Poisson’s ratio of the carbon fibre reinforced with CNT and GP particle reinforcement were estimated. The current study is applied to the efficient design of nanoparticle reinforced carbon fibre reinforced composites.

[Display omitted] Polysiloxanes are becoming new trend in self-cleaning (oil- and water‐repellent) applications due to their low-cost and environmentally friendly nature. Lower phase separation of polysiloxanes in coating matrix is critical to obtain excellent self-cleaning properties. We hypothesize that telechelic polysiloxanes can bind to coating matrix at both ends and thus will suppress phase separation of polysiloxane as compared to hemi-telechelic analog and thus will offer excellent self-cleaning properties. Eight PDMS additives were prepared via the free-radical polymerization of telechelic and hemi-telechelic methacryloxypropyl-based PDMS precursors with methylmethacrylate (MMA) and glycidylmethacrylate (GMA). The compositions of the prepared polysiloxane additives were optimized to obtain excellent self-cleaning performance. Our breakthrough development confirms that telechelic polysiloxanes (PDMS-T) incorporated into epoxy-based anti-smudge coatings outperform hemi-telechelic polysiloxanes (PDMS-HT) by offering excellent repellency against difficult to repel liquids. These breakthrough findings will vertically advance Science and innovations in the self-cleaning field by offering robust guidelines for choosing suitable polysiloxane for self-cleaning applications. [ABSTRACT FROM AUTHOR]

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In this work, Copper oxide nanofiller with different contents (0.05, 0.5, 1, and 2 wt% CuO) were embedded in DGEBA epoxy matrix using ultrasonic wave and casting processing technique. This study deals to assess and investigate the CuO fillers impact on various properties of CuO/DGEBA hybrid polymer nanocomposites (CuO/DGEBA-HPNCs). The structural modifications were tracked using X-ray diffraction (XRD) patterns and Fourier transform infrared spectra. XRD profiles demonstrated that the crystallinity of samples increases with an increase of CuO nanoparticles (CuO NPs) contents, which improved the crystallinity of CuO/DGEBA-HPNCs. The interplanar distance, particle size, and the average inter-crystalline separation were also calculated and investigated. Interactions between CuO NPs and DGEBA polymer matrix were reported using the correlated FTIR analysis and XRD results, which was related to the formation of new absorption bands for the 1 wt% and 2 wt% CuO NPs samples. The UV–Vis investigation showed that the absorption edge values exhibited a red-shift with the rise in CuO NPs, due to interactions between the doping and the DGEBA matrix owing to the formation of charge transfer. Furthermore, the dielectric characteristics such as dielectric permittivity (ɛ′, ɛ″), electrical modulus (M′, M″), and dielectric AC impedance (Z′, Z″) of the CuO/DGEBA-HPNCs were performed at room temperature as a function of CuO nanofiller contents and frequency. Experimental modulus data were successfully fitted to Havriliak–Negami model. AC impedance spectroscopy was carried out to disclose the CuO/DGEBA-HPNCs as a function of various CuO NPs fillers. The obtained dielectric parameters, using fitting curves, were altered by the CuO NPs filler concentration. The results showed the ability to use the samples in optoelectronic devices. [ABSTRACT FROM AUTHOR]

This article deals with the thermal oxidation mechanisms and kinetics of epoxy-diamine (EPO-DA) networks used as composite matrices reinforced with carbon fibers in the aeronautical field. The first part of this article is devoted to a detailed presentation of the new analytical kinetic model. The so-called “closed-loop” mechanistic scheme, developed in the last 3 decades in our laboratory in order to accurately describe the thermal oxidation kinetics of saturated hydrocarbon polymers, is recalled. Its main characteristics are also briefly recalled. Then, the system of differential equations derived from this oxidation mechanism is analytically solved without resorting to the usual simplifying assumptions that seriously degrade the reliability of all kinetic models. On the contrary, the generalization of the proportionalities observed between the steady concentrations of the different reactive species (i.e., hydroperoxides and alkyl and peroxy radicals) to the entire course of thermal oxidation gives a series of much sounder equations. From this basis, the kinetic model is completed by considering new structure/property relationships in order to predict the consequences of thermal oxidation on the thermomechanical properties, in particular on the glass transition temperature (Tg). To reach this second objective, the two main mechanisms responsible for the alteration of the macromolecular network structure are recalled: chain scissions and crosslinking. Like any other chemical species, their kinetics are directly expressed from the oxidation mechanistic scheme using the classical concepts of chemical kinetics. The second part of this article is devoted to the checking of the kinetic model reliability. It is shown that this latter accurately simulates the experimental curves of carbonyl build-up and Tg decrease versus time of exposure determined in our laboratory for three EPO-DA networks under study, exposed in a wide variety of thermal oxidative environments. The values determined by inverse solving method for the different model parameters are discussed and their temperature dependence are elucidated. Finally, an end-of-life criterion is proposed for predicting the lifetime of EPO-DA networks involving a predominant chain scission process.

“Green” thermally stable hardener was synthesized from a PET waste. The rigid molecular linear structure of the new hardener suggests that it will provide the polymer matrix with the necessary physical and mechanical characteristics. It also allows the expectation that cured matrix based on this hardener can provide increased toughness. New hardener was used as a curing agent for three epoxy resins—tetraglycidyl methylenedianiline (TGDMA, 111–117 EEW), diglycidylether of bisphenol A (DGEBA, 170-192 EEW) and solid epoxy resin (SER)—with a medium molecular weight (860–930 EEW) based on DGEBA. The mixtures were found to have the highest Tg for the DGEBA resin, and high of that for TGDMA and SER. According to the DMA analysis for two cured matrices, the hardener proved to be no worse than the standard ones, and made it possible to obtain cured matrices with excellent mechanical properties, which allows us to hope for further application of new hardener cured epoxy matrices in appropriate composite materials at high temperatures.

Polymeric hybrid nanocomposites, due to improved mechanical, thermal, and electrical properties, are key factors in recent technologies. Because of anisotropic characteristics of polymeric hybrid nanocomposites, mechanical properties and their behavior are very difficult to predict. If they are fabricated with complicated woven fabric patterns, it becomes more difficult to predict. This review discusses in detail the properties and manufacturing methods of various fibers, focuses on different manufacturing, processing, and characterization techniques used for polymeric hybrid nanocomposites. Theoretical composite models and some recent advances in modeling and simulation techniques for polymer nanoparticle composites are discussed and thus this review can provide significant guidelines for the development of manufacturing, characterization, testing, modeling, and simulation techniques for high performance hybrid polymer nanocomposites as current state of art. [ABSTRACT FROM AUTHOR]

The strength and wettability of polyacrylonitrile technical cord and of hydrated cellulose and basalt technical threads, treated with organosilicon dressing agents, were evaluated. The modified threads show enhanced surface activity. The kinetic features of epoxy binder curing in the presence of the modified threads were studied. Introduction of the fibrous fillers under consideration improves the operation characteristics of the epoxy composites. [ABSTRACT FROM AUTHOR]

The change in the abrasive resistance under testing composites based on an epoxy matrix filled with sludge originating from cutting tool sharpening exhibits the same character for all compositions, which reflects the process of wear self-organization. A composite filled with abrasive particles originating from grinding wheels has the maximum abrasive wear resistance. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) functionalized curaua fiber (CF) has been shown to improve the mechanical properties and ballistic performance of epoxy matrix (EM) nanocomposites with 30 vol% fiber. However, the possibility of further improvement in the property and performance of nanocomposites with a greater percentage of GO functionalized CF is still a challenging endeavor. In the present work, a novel epoxy composite reinforced with 40 vol% CF coated with 0.1 wt% GO (40GOCF/EM), was subjected to Izod and ballistic impact tests as well as corresponding fractographic analysis in comparison with a GO-free composite (40CF/EM). One important achievement of this work was to determine the characteristics of the GO by means of FE-SEM and TEM. A zeta potential of −21.46 mV disclosed a relatively low stability of the applied GO, which was attributed to more multilayered structures rather than mono- or few-layer flakes. FE-SEM images revealed GO deposition, with thickness around 30 nm, onto the CF. Izod impact-absorbed energy of 813 J/m for the 40GOCF/EM was not only higher than that of 620 J/m for the 40CF/EM but also higher than other values reported for fiber composites in the literature. The GO-functionalized nanocomposite was more optimized for ballistic application against a 7.62 mm projectile, with a lower depth of penetration (24.80 mm) as compared with the 30 vol% GO-functionalized CF/epoxy nanocomposite previously reported (27.43 mm). Fractographic analysis identified five main events in the ballistic-tested 40GOCF/EM composed of multilayered armor: CF rupture, epoxy matrix rupture, CF/matrix delamination, CF fibril split, and capture of ceramic fragments by the CF. Microcracks were associated with the morphological aspects of the CF surface. A brief cost-effective analysis confirmed that 40GOCF/EM may be one of the most promising materials for personal multilayered ballistic armor.

Abstract In this work, the functional graphene oxide (bGO) was facilely synthesized through a grafted reaction between graphene oxide (GO) and bio-based bis-furan di-epoxide (BFDE). The structure of bGO was confirmed by FTIR spectra and Raman spectra. The properties of polymer composite materials depend on the distribution of the nanofiller in the matrix and due to the presence of polymer chains our bGO sheets exhibit a better dispersibility in solvents and polymer matrix, which provides a potential opportunity for the preparation of BFDE composites with excellent performance. Bio-based BFDE composites containing 0.05–0.5 wt.% of bGO exhibit superior mechanical and thermal properties. The addition of just 0.5 wt% such bGO to an BFDE causes 80%, 49%, 21%, 69% and 97% enhancement in tensile strength, flexural strength, flexural modulus, critical stress intensity factor and critical strain energy release rate, respectively. The thermal decomposition temperature T d of bGO/BFDE composites was increased about ~17 °C compared to blank BFDE sample. In addition, we found that introducing unmodified GO to epoxy matrix lead to an insignificant increase of the thermal property of the resulting GO/BFDE composites. The enhanced mechanical properties and thermal properties of bGO/BFDE composites could be attributed to strong interfacial interactions and high affinity between bGO and epoxy matrix.

It is proved that in order to increase the operational characteristics of parts of the river and sea transport, including their physical and mechanical properties, it is advisable to use the protective polymeric composite coatings.The effect of fillers on the flexural stresses of the developed epoxy composite was analyzed. The critical content of components was determined by the method of mathematical planning of the experiment: the synthesized powder mixture - 0.05 pts.wt., discrete fibers - 0.10 to 0.15 pts.wt. per 100 pts.wt. of epoxy oligomer ED-20. Introduction of such ingredients into the epoxy binder allows to increase the flexural stresses to σ f=77.4…78.6 MPa. The obtained results allow to create materials with improved values of physical and mechanical properties.

It is proved that in order to increase the operational characteristics of parts of the river and sea transport, including their physical and mechanical properties, it is advisable to use the protective polymeric composite coatings. The effect of fillers on the flexural stresses of the developed epoxy composite was analyzed. The critical content of components was determined by the method of mathematical planning of the experiment: the synthesized powder mixture - 0.05 pts.wt., discrete fibers - 0.10 to 0.15 pts.wt. per 100 pts.wt. of epoxy oligomer ED-20. Introduction of such ingredients into the epoxy binder allows to increase the flexural stresses to sf=77.4...78.6 MPa. The obtained results allow to create materials with improved values of physical and mechanical properties. [ABSTRACT FROM AUTHOR]

In the current research, the effect of cyclic temperature variation on the mechanical and thermal properties of woven carbon-fiber-reinforced polymer (CFRP) composites was investigated. To this, carbon fiber textiles in twill 2/2 pattern were used as reinforced phase in epoxy, and CFRPs were fabricated by vacuum-assisted resin-infusion molding (VARIM) method. Thermal cycling process was carried out between −40 and +120 °C for 20, 40, 60 and 80 cycles, in order to evaluate the effect of thermal cycling on mechanical and thermal properties of CFRP specimens. In this regard, tensile, bending and short beam shear (SBS) experiments were carried out, to obtain modulus of elasticity, tensile strength, flexural modulus, flexural strength and inter-laminar shear strength (ILSS) at room temperature (RT), and then thermal treated composites were compared. A dynamic mechanical analysis (DMA) test was carried out to obtain thermal properties, and viscoelastic properties, such as storage modulus (E’), loss modulus (E”) and loss factors (tan δ), were evaluated. It was observed that the characteristics of composites were affected by thermal cycling due to post-curing at a high temperature. This process worked to crosslink and improve the composite behavior or degrade it due to the different coefficients of thermal expansion (CTEs) of composite components. The response of composites to the thermal cycling process was determined by the interaction of these phenomena. Based on SEM observations, the delamination, fiber pull-out and bundle breakage were the dominant fracture modes in tensile-tested specimens. [ABSTRACT FROM AUTHOR]

The effect of additional heat treatment at elevated temperatures on the physicomechanical characteristics of unidirectional epoxy organoplastics has been studied. It has been shown that long exposure (24 h) at temperatures of 120 and 180°C leads to a significant decrease in crack resistance, as well as in the bending and shear characteristics of the composites under study. Infrared spectroscopy has revealed a tendency towards the formation of carbonyl groups after holding at 120°C. Possible reasons for the observed changes are discussed. [ABSTRACT FROM AUTHOR]

The main objective of this study was to investigate the efficiency of the sonication process and of multi-walled carbon nanotubes (MWCNTs) content on the mechanical and thermal properties of an epoxy matrix. Three different sonication powers (25, 50 and 75 W) were used to disperse the MWCNTs (0.2%, 0.4% and 0.6% wt.) in the epoxy matrix. Tensile tests were performed to determine the mechanical properties of the nanocomposites, while the thermal properties were determined by the thermogravimetric analysis (TGA) and the Differential Exploratory Calorimetry (DSC). Finally, a SEM analysis was used to investigate the morphology of the tensile fractured surface and the dispersion of the nanotubes in the polymeric matrix, since the quality of dispersion influences the mechanical and thermal properties of nanocomposites. It was found that the addition of carbon nanotubes to the epoxy matrix and the parameters of the sonication process affect the mechanical and thermal properties of nanocomposites. An increase of approx. 14% in tensile strength and 15% of Young's modulus, when compared to the pure epoxy matrix was found for 75 W sonication power output and 0.6% MWCNTs weight percentage. The thermal analysis indicated that the presence of MWCNTs increased the T onset of the nanocomposites when compared to pure epoxy resin. Finally, increasing the sonication power output leads to higher T g of the nanocomposites studied here. [ABSTRACT FROM AUTHOR]

The performance of fiber-reinforced composites significantly relies on the microstructure and properties of the fiber–matrix interface. Escalating the aspect ratio of the fiber surface by coating with nanoparticles is a proven technique for improving the fiber/matrix adhesion. Subsequently, improved adhesion between epoxy and fiber, which is ascribed due to improved interfacial friction, chemical bonding, and resin toughening would enhance the interfacial strength of such laminated composites. Here, graphite nanoparticles were oxidized, and these charged particles were coated onto the carbon fibers (CFs) surface using ultrasonically assisted direct current electrophoretic deposition. Functionalization of the graphite nanoparticle upon oxidation was confirmed through dispersion analysis, Fourier transformed infrared spectroscope, thermogravimetric analysis, and field emission scanning electron microscope. The CFs fabrics were grafted with different sets of samples prepared by varying voltage and deposition time. The deposition of oxidized graphite nanoparticle over the CFs was authenticated through field emission scanning electron microscope. A transverse fiber bundle test was carried out to assess interfacial strength between CF and epoxy matrix. The transverse fiber bundle test strength is found 113% higher for CF coated with oxidized graphite nanoparticles at 50 V for 5 min compared to that of as-received sized CF composites. Field emission scanning electron microscopy analysis of transverse fiber bundle test fractures samples identified multiple crack propagation zone owing to the presence of graphite nanoparticle on CF. [ABSTRACT FROM AUTHOR]

In this investigation, the fabrication of thermal conductive epoxy composite with the assimilation of synthesized expanded graphite (EG) decorated with copper compound nanoparticles [copper (Cu), copper(II) oxide (CuO) and copper(I) oxide (Cu2O) nanoparticles], has been reported wherein, Cu-compound was attached to EG surface by solid-state pyrolysis of copper(II) acetate (CA) monohydrate. The prepared hybrid filler was characterized by an x-ray diffraction technique and the Cu-compound nanoparticles size was 40.8 ± 17.67 nm. The microstructure and morphology of the distributed Cu-compound nanoparticles over the EG surface were characterized by transmission electron microscopy (TEM) and scanning electron microscopy. The Cu-compound nanoparticles decorated EG hybrid filler at 10 wt.% loading ((EG-CA (4)/Ep)10) demonstrated the thermal conductivity (TC) which is 11.8 times higher than the neat epoxy due to the formation 3D percolation heat-conducting networks. Further, decoration of Cu-compound on the EG surface resulted in higher TC as measured using a guarded heat flow meter technique. Lap shear strength of (EG-CA (4)/Ep)10 composite was tuned to 5.93 ± 0.27 MPa as characterized by a universal testing machine. The porosity of fabricated composites was decreased as Cu-compound attachment increases on the EG substrate. The thermo-gravimetric analysis revealed enhanced thermal stability of (EG-CA (4)/Ep)10 composite to 407°C at 50% weight loss consideration. The electrical resistivity of the composite was reduced with the addition of the EG filler system as confirmed from the super megaohmmeter. [ABSTRACT FROM AUTHOR]

The potential of carbon nanotubes (CNT) as multifunctional filler in poly(epoxy)-based structural composites has been investigated. In a first step the reinforcement effect of CNT has been studied by tensile and three points bending tests, which evidenced significant improvements of stress and strain at break (respectively +17% and +30% for tensile tests on unidirectional carbon fibre-epoxy composites). Moreover, fracture experiments have also revealed a positive effect of CNT on the toughness (G1c) of carbon fibres-epoxy composites (+105% of improvement at the initial stage). In a second step, the health monitoring capability quantum resistive strain sensors (sQRS) made of CNT filled epoxy nanocomposite, incorporated in the core of glass fibres-epoxy composites has been studied. It was shown that during cyclic tensile tests, following the evolution of the relative resistance amplitude (Ar) of sQRS with strain gives a pertinent information on non-reversible phenomena such as plastic deformation and cracks' development within the composite. In particular, the evolution of the sQRS sensitivity (gauge factor GF) under and over the elastic limit, allows to track damage accumulation throughout the composite. These results suggest a possible use of sQRS for the structural health monitoring (SHM) of composites in fields such as boating, wind energy, aeronautics and automotive. [ABSTRACT FROM AUTHOR]

The role of carbon nanotube purification treatment as a means to improve the thermal properties of polymer matrix composites was investigated. Particular emphasis was placed on clarifying the processing‐property relationship in polymer composites for thermal management applications. The results indicated that purification treatment is critical to the thermal properties of derived polymer composites. Purification treatment can yield a twofold increase in composite thermal conductivity because of improved effectiveness in interfacial interaction and increased chemical purity of the filler. However, there is a trade‐off between the benefits and disadvantages associated with purification treatment, particularly when thermal and electrical properties are both concerned. Purification treatment gives rise to a sharp decrease in composite electrical conductivity by at least two orders of magnitude because of the lack of an effective percolating network. The effect of purification treatment on composite electrical properties is more significant than on its thermal properties. [ABSTRACT FROM AUTHOR]

This study places emphasis on investigating the impact of integrating Sterculia foetida fiber and natural fillers into an epoxy matrix. An experimental investigation was conducted to examine the impact of incorporating natural fillers on the physical, mechanical, and thermal properties of a novel series of epoxy-based composites reinforced with fibers. The physical and mechanical properties of the composites produced in this study exhibited a higher level of concordance with the previously developed composites that incorporated natural fibers. It was determined that the composites containing 5% fillers and Sterculia foetida fiber exhibited low percentage error and moisture absorption. The composite manufactured with a 5% filler content exhibited superior mechanical qualities in terms of tensile strength, impact resistance, and Rockwell hardness compared to the other composites investigated in this study. The results of thermogravimetric analysis indicate that the incorporation of Sterculia bark and rice husk filler into the composites leads to an enhancement in thermal stability, specifically in relation to the Sterculia foetida content. The cellulose fiber utilized in this study exhibited thermal stability, indicating its appropriateness for usage in applications involving moderate temperatures. [ABSTRACT FROM AUTHOR]

The European steel industry produces about 70 million tons/year of steel by the electric arc furnace (EAF). The slag consists of about 15% by weight of the produced steel, thus from the perspective of the circular economy, it has a high potential as a co-product. This research aims to assess an innovative reuse of EAF slag as filler in different polymer matrixes: thermoplastic (polypropylene), thermosetting (epoxy resin), elastomeric (nitrile butadiene rubber), and recycled end of life rubber tire. A comparison between neat polymer and polymer filled with a certain amount of EAF slag has been carried out by tensile (or flexural), compression, and hardness tests. Experimental results show that slag as a filler increases the composites’ hardness and elastic modulus at the expense of toughness. For a safe reuse of the slag, the leaching of hazardous elements must comply with current legislation. It was found that, although the used EAF slag releases small amounts of Cr, Mo, and V, incorporating it into a polymer matrix reduces the leaching. The EAF slag particles distribution has been observed by scanning electron microscopy (SEM) images. The obtained results show good technical feasibility of this innovative slag application so that it could pave the way to a new industrial symbiosis between dissimilar sectors, bringing economic and environmental benefits.

The fique is a plant typical of the Colombian Andes, from which relatively common items are fabricated. One of these is woven fabric extensively applied in sackcloths. The mechanical strength of fique fabric have motivated recent investigations on possible reinforcement of polymer matrix composites. For this purpose its thermo-mechanical behavior was unveiled. In particular, dynamic mechanical analysis (DMA) of fique fabric reinforced polyester matrix composites disclosed improved viscoelastic behavior in association with change in the glass transition temperature. The present work extends this investigation to epoxy matrix, which is one of the most employed thermoset polymer for composite matrix. Fique fabric volumetric fractions of up to 50% are for the first time incorporated into epoxy composites. It was found that these incorporations significantly increased the viscoelastic stiffness of the composite, given by the storage modulus (E’), in the temperature interval from -50 to 170°C. An accentuated softening in viscoelastic stiffness was revealed for all composites above 75°C. Peaks in both the loss modulus (E”) and tangent delta (tan δ), respectively associated with the lower and upper limits of the glass transition temperature, were shifted towards higher temperatures with increasing amount of fique fabric.

It is substantiated that for improving the performance characteristics of vehicle parts, including their corrosion and wear resistance, it is advisable to use protective polymeric composite coatings. It is shown that in order to increase the indexes of physical and mechanical and thermophysical properties in the epoxy binder, it is necessary to introduce additives: modifiers, plasticizers, dispersed and fiber fillers. The introduction of modifiers into the epoxy binder is relevant, and effectively use them in the complex. The influence of modifier and hardener on the adhesion strength and destructive stresses during bending of the developed epoxy composite has been analyzed. The critical content of the components: the MBMA modifier is 0.25 ... 0.50 pts.wt., hardener PEPA - 8 ... 10 wt. per 100 pts.wt. of epoxy oligomer ED - 20 was found by the method of mathematical planning of the experiment. The introduction of such ingredients into the epoxy binder increases the adhesion strength of matrix to σa = 28.9 ... 31.3 MPa and the fracture stresses during the flexion to σfl = 51.2 ... 54.4 MPa. The obtained results allow to create materials with improved physical and mechanical properties in the complex.

The Amazonian region of South America is known for its diversified number of plants from which food, medicine, wood and fibers have, since long time, been produced by local natives. A typical example is the guarumã (“guaruman”as suggested English spelling) scientifically identified as Ischinosiphon koem, an abundant plant found in the low lands alongside rivers of the state of Para in Brazil. Fibers extracted from the stem of the guaruman are used in ropes and baskets owing to their strength. In the present work, the possibility of applying guaruman fibers as reinforcement of polymer matrix composites is, for the first time, investigated. Amounts up to 30 vol% of continuous and aligned fibers were incorporates into epoxy matrix composites. Density measurements disclosed the guaruman to be one of the lightest natural fibers. Tensile tests indicate that the guaruman fiber addition was able to improve the composite elastic modulus. However, no significant change was found in the ultimate strength, total strain and resilience. On the other hand, a cost-effective analysis revealed a substantial reduction of ~29% in the epoxy composite price due to the incorporation of fibers. Preliminary ballistic evaluation disclosed a potential for application of guaruman epoxy composites in multilayered armor.

It is proved, that for improving the performance characteristics of vehicle parts, including their corrosion resistance and wear resistance, it is advisable to use protective polymeric composite coatings. It is shown that in order to increase the indexes of physical-mechanical and thermophysical properties in the epoxy binder, it is necessary to introduce additives: modifiers, plasticizers, dispersed and fiber fillers. The introduction of dispersed additives into the epoxy binder is actual. It this case, it is effective to use fillers of different dispersity in the complex. The influence of two-component polydispersed filler on the elasticity modulus in flexure of the developed epoxy composite is analyzed. The critical content of a two-component polydispersed filler is found by the method of mathematical planning of an experiment. a mixture of nanodispersed compounds 1 (d = 20 . . . 80 nm) − 0.75 . . . 1.0 pts.wt., a mixture of discrete fibers 1 (l = 0.5 . . . 1.0 mm, d = 18 . . . 25 µm) – 0.2 pts.wt. by the 100 pts.wt. of the epoxy oligomer ED-20. An introduction of the two-component polydispersed filler to the epoxy binder allows significantly to increase the values of the elasticity modulus in flexure of the protective coatings to = 4.8 . . . 5.0hP a. Additionally, the effect of two-component polydispersed filler on the impact resilience of the developed epoxy composite was determined. It is proved that the critical content of a two-component polydisperse filler is: a mixture of nanodispersed compounds 2 (d = 30 . . . 40 nm) − 1.00 . . . 1.25 pts.wt., a mixture of discrete fibers 2 (l = 0.5 . . . 1.0 mm, d = 18 . . . 25 µm) − 0.1 . . . 0.2 pts.wt. by the 100 pts.wt. of epoxy ED-20. An introduction of the two-component polydispersed filler to the epoxy binder allows significantly to increase the values of the impact resilience to W’ = 10.0. . . 10.2 kJ/m2. The obtained results allow us to create polymeric coating with improved indexes of the physical and mechanical properties in complex.

UV‐activated frontal polymerization was exploited for the preparation of epoxy–carbon fibre composites. The curing process was investigated showing the frontal behaviour, and the final properties of UV‐cured composites were compared with those of the same composites obtained by thermal curing in the presence of amine as hardener. The best curing formulations were designed, defining the photoinitiator‐to‐thermal initiator ratio, which was 1.5:1.5. It was observed that the presence of the carbon fibres induced an acceleration of the front velocity. By comparing the thermomechanical properties of the thermally cured composite and the same composite crosslinked using the frontal process, we could observe that the latter showed higher Tg value and lower σf. This was attributed to the formation of a different polymeric network structure. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]