Wyniki wyszukiwania - Biblioteka Nauki

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Investigation of crack resistance in epoxy/boron nitride nanotube nanocomposites based on multi-scale methodInvestigation of crack resistance in epoxy/boron nitride nanotube nanocomposites based on multi-scale method

100%

Hemmatian H. , Zamani M. R. , Jam J. E.

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tom Vol. 57 nr 1

207--219

EN

Boron nitride nanotubes (BNNTs) possess superior mechanical, thermal and electrical properties and are also suitable for biocomposites. These properties make them a favorable reinforcement for nanocomposites. Since experimental studies on nanocomposites are timeconsuming, costly, and require accurate implementation, finite element analysis is used for nanocomposite modeling. In this work, a representative volume element (RVE) of epoxy/BNNT nanocomposites based on multi-scale modeling is considered. The bonds of BNNT are modeled by 3D beam elements. Also non-linear spring elements are employed to simulate the van der Waals bonds between the nanotube and matrix based on the Lennard- -Jones potential. Young’s and shear modulus of BNNTs are in ranges of 1.039-1.041 TPa and 0.44-0.52 TPa, respectively. Three fracture modes (opening, shearing, and tearing) have been simulated and stress intensity factors have been determined for a pure matrix and nanocomposite by J integral. Numerical results indicate that by incorporation of BNNT in the epoxy matrix, stress intensity factors of three modes decrease. Also, by increasing the chirality of BNNT, crack resistance of shearing and tearing modes are enhanced, and stress intensity factor of opening mode reduced. BNNTs bridge the crack surface and prevent crack propagation.

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Effect of addition of non-functionalized graphene oxide in a commercial epoxy resin used as coating

100%

Varela Caselis J. L. , Santamaría Juárez J. D. , Galicia Aguilar J. A. , Domínguez Alcalá M. F. , Rubio Rosas E. , Mendoza Hernández J. C. , Sánchez Cantú M.

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2021

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tom Vol. 39, No. 4

467--477

EN

The paper studies the effect of incorporating graphene oxide (GO) without surface functionalization on a commercial epoxy resin. GO was dispersed in a commercial epoxy resin at concentrations of 0 wt.%, 0.1 wt.%, 0.5 wt.%, 1 wt.%, and 3 wt.%. The resultant materials were deposited on carbon steel substrates, followed by the use of a 5 wt.% aqueous NaCl electrolyte, to evaluate the effectiveness of their anticorrosive coating function. Scanning electron microscopy (SEM) analysis showed that the GO was homogenously dispersed in the polymer matrix, resulting in flat and smooth surfaces. The X-ray diffraction (XRD) results showed that although GO was highly dispersed in the polymer matrix, multilayer graphene was also obtained after curing. The anticorrosive properties were evaluated by electrochemical impedance spectroscopy (EIS) at various exposure periods. Analysis of the prepared samples indicated that the best anticorrosion performance among them was available with the 0.5 wt.% GO coating. The obtained results indicate that GO–polymer matrix composites provide improved corrosion protection properties even after 500 h exposure to the NaCl solution.

3

Encapsulation of power electronics components for operation in harsh environments

86%

Stosur M. , Sowa K. , Piasecki W. , Płatek R. , Balcerek P.

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tom Vol. 66, nr 4

855--866

EN

This paper reports on analyses and testing of sensitive power electronics components encapsulation concept, enabling operation in harsh, especially high pressure environments. The paper describes development of the concept of epoxy modules that can be used for protecting of the power electronics components against harsh environmental conditions. It covers modeling of the protective capsules using a simple analytical approach and Finite Element Method (FEM) models and validation of the developed models with the high pressure tests on samples fabricated. The analyses covered two types of the epoxy modules: of sphere- and elongated- shape, both with electrical penetrators that enable electrical connection of the encapsulated components with external power sources as well as other power modules and components. The tests were conducted in a pressure chamber, with a maximum applied pressure of 310 bars, for which online strain measurements have been conducted. The experimental results were compared with the simulation results obtained with analytical and FEM models, providing validation of the models employed. The experimental part of this work was conducted in collaboration with Polish Naval Academy in Gdynia.

4

Polymer Blended (Epoxy/Vinylester) Nanocomposites Resistance against Pulling & Sliding Wear Loads

86%

Harisankar P. , Reddy Y. V. M. , Reddy K. H.

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tom Vol. 18

75--90

EN

This paper discloses the development and synthesis of polymer blended nanocomposites filled with nanoclay. The hybridization of epoxy is mixed with vinylester resin (VER) to prepare polymer blend filled with organoclay was studied to enhance mechanical properties of epoxy/VER. Clay loading was done in such a way that with different wt. proportions viz.1, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, & 7.5 w % ratios. Appropriately cured samples gave excellent mechanical and tribological properties. Results showed that the tensile strength of the composites increased with increase in filler content for the range of filler contents (2.5-4 % vol.). The results indicated that at 4 % wt. of filler concentration the tensile strength obtained is good i.e. 47.79 MPa with density 1.37 gm/cm3 and hardness 45.5. Dry Sliding wear tests were also conducted by following a well-planned experimental schedule based on Taguchi’s design of experiments, considering parameters like Filler content, Normal load, Sliding Velocity and Sliding distance, on a Pin-On-Disc set-up (ASTM G-99 standard, Make: DUCOM Engineers, Bangalore, India). In the experimentation composite pins were worn against a rotating steel disc (Europe Norm) EN-31, (Rockwell C Hardness) HRC 60 and (Roughness Average) Ra 0.02 microns. Control factors like Filler Content, Normal Load were found to be significant factors affecting the Wear rate i.e. the inclusion of nanoclay as filler found to be contributed in improving the wear resistance of the composite. SEM observations are made to probe the wear mechanisms involved.

5

Comparative Studies by a Genetic Algorithm on the Mechanical Properties of PLA and Expoxy Biocomposite Materials Reinforced with Alfa Natural Fiber

86%

Tadjedit S. , Temimi L. , Boutaous A. , Mokadem A. , Doumi B. , Beldjoudi N.

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2016

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tom Vol. 20, nr 3

331--345

EN

The natural bers are indeed a renewable resource, biodegradable and naturally with technical qualities and very high mechanical properties. The mechanical properties of reinforcement biocomposites as alfa / polylactic acid (PLA) are largely conditioned by the interfacial bond between the two materials (ber and matrix). To characterize this link and locate damage to the ber-matrix interface, we used a genetic approach based on the Cox model and formalism of Weibull. This model taking into account the micromechanical behavior of the three composite and biocomposites materials: Glass/epoxy, alfa / epoxy and alfa / PLA. The results of this simulation show that the damage level of the interface is related to the nature of the materials used and the applied mechanical stress, and has shown that the green material alfa / PLA is stronger than the biomaterial alfa / epoxy. The results of this modeling are in agreement with those obtained experimentally by Antoine et al. So the natural bers have a very important role in enhancing the mechanical strength of composite and biocomposites materials.

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Swarm intelligence integrated approach for experimental investigation in milling of multiwall carbon nanotube/polymer nanocomposites

81%

Kharwar P. K. , Verma R. K. , Mandal N. K. , Mondal A. K. , Kharwar P. K. , Verma R. K. , Mandal N. K. , Mondal A. K.

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nr 3

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Swarm intelligence integrated approach for experimental investigation in milling of multiwall carbon nanotube/polymer nanocomposites

72%

Kharwar P. K. , Verma R. K. , Mandal N. K. , Mondal A. K.

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tom LXVII, nr 3

353--376

EN

In manufacturing industries, the selection of machine parameters is a very complicated task in a time-bound manner. The process parameters play a primary role in confirming the quality, low cost of manufacturing, high productivity, and provide the source for sustainable machining. This paper explores the milling behavior of MWCNT/epoxy nanocomposites to attain the parametric conditions having lower surface roughness (Ra) and higher materials removal rate (MRR). Milling is considered as an indispensable process employed to acquire highly accurate and precise slots. Particle swarm optimization (PSO) is very trendy among the nature-stimulated metaheuristic method used for the optimization of varying constraints. This article uses the non-dominated PSO algorithm to optimize the milling parameters, namely, MWCNT weight% (Wt.), spindle speed (N), feed rate (F), and depth of cut (D). The first setting confirmatory test demonstrates the value of Ra and MRR that are found as 1.62 µm and 5.69 mm3/min, respectively and for the second set, the obtained values of Ra and MRR are 3.74 µm and 22.83 mm3/min respectively. The Pareto set allows the manufacturer to determine the optimal setting depending on their application need. The outcomes of the proposed algorithm offer new criteria to control the milling parameters for high efficiency.

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Effect of silica fume and calcium carbonate whisker on interfacial behavior of near-surface-mounted FRP with magnesium phosphate cement

72%

Zhang L. , Geng T. , Liu Z. , Zhang W. , Shang Q.

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tom Vol. 20, no. 1

14--29

EN

Magnesium phosphate cement (MPC) is a potential substitute of epoxy as an adhesive material due to its advantages in setting time, early strength, and good fire and corrosion resistance. In this study, silica fume (SF) and calcium carbonate whisker (CCW) were employed to improve bond capacity of MPC which were used instead of epoxy in near-surface-mounted (NSM) fiber-reinforced polymer (FRP) systems. A direct pull-out test (DPT) was carried out to investigate bond performances of FRP–concrete interface after incorporating SF and CCW. According to the mix proportion of the MPC, a total of twenty-seven specimens in nine sets were divided into four groups: one group without additive, one group with SF alone, one group with CCW alone, and the last group with SF and CCW combination. Results showed that SF or CCW alone could improve MPC bond capacity, but their excess application would reduce it. SF and CCW combination, however, did not improve bond capacity as effectively as SF or CCW alone. Moreover, the addition of CCW would improve MPC’s bond ductility, with or without the adding of SF, but with the increase in CCW concentration, this improvement effect would decrease. Meanwhile, SF alone lowered its bond ductility.

9

Przemiana lepkosprężysta i właściwości napełnionych kompozytów epoksydowych odpornych na ścieranie

72%

Prokopchuk N. R. , Dolinskaya R. M. , Poloz A. Y. , Ebich Y. R.

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tom T. 22, nr 2

136--142

PL

Badano właściwości lepkosprężyste napełnionych kompozytów epoksydowych na bazie żywicy dian ED-20, w temperaturze 60–140°C, w zależności od zawartości napełniacza, węglika krzemu. Przedstawiono różnice we właściwościach kompozytów w zależności od zmiany stosunku energii odkształcenia sprężystego i plastycznego. Te energie odkształcenia kompozytów są z kolei określane przez morfologię wzmacniającego napełniacza o małej plastyczności.

EN

Viscoelastic properties of the filled epoxy composites on the basis of diane resin ED-20 are studied at 60–140°C depending on concentration of a filler, silicon carbide. Different properties of composites caused by change of an energy ratio of elastic and viscous deformation are shown. These energies of deformation of composites, in turn, are defined by morphology of the strengtheninged low-ductile filler.

10

Application of carbon nanotubes (CNT) to design of the strain sensor

58%

Grabowski K. , Uhl T. , Zbyrad P.

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tom R. 58, nr 11

984-986

EN

The aim of this work was to develop a sensor which could be easily applied to the tested material and integrated with it. Therefore, this paper is focused on the development of the Carbon Nanotube - a polymer strain sensor - which should fulfill such requirements. The development of such a sensor is discussed and the test of its performance are presented. Multiwalled CNTs were mixed with polymer and applied to the materials with use of screen printing. The sensor was tested for different types of loads. Manufacturing technology and sensor test results are presented in this work.

PL

W pracy opisano prototyp czujnika zrealizowany przy użyciu nanorurek węglowych oraz epoksydu. Czujnik został naniesiony na badany materiał (kompozyt włókna szklanego) przy użyciu sitodruku. Struktura sensora (rozłożenie nanorurek w epoksydzie) została zbadana przy użyciu mikroskopu elektronowego. Wykazano, że przy stosunkowo dużych zawartościach procentowych (powyżej 7.5%) nanorurki węglowe tworzą zbite skupiska, przy czym mniejsze zawartości procentowe pozwalają na stosunkowo równomierne rozłożenie nanorurek węglowych w epoksydzie. Dodatkowo czujniki zostały poddane badaniom statycznym jak i dynamicznym. Przy badaniach statycznych miało to na celu zbadania odpowiedzi sensora (czy jest zachowana jego liniowość). Przy obciążeniach dynamicznych celem było sprawdzenie czy dochodzi do uszkodzenia struktury sensora przy stosunkowo dużej ilości cykli obciążeń. Zmiany rezystancji zostały porównane ze zmianami odkształceń badanego materiału (uzyskanymi z maszyny wytrzymałościowej). Otrzymano liniowe odpowiedzi czujników zarówno przy małej jak i dużej liczbie cykli obciążeń.

11

Selected mechanical properties of stratfied composites with CNT filled matrix

58%

Cîrciumaru A. , Bîrsan I.-G. , Andrei G.

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tom R. 9, nr 2

186-191

EN

While the aim of composites is to replace metals in various applications, researchers are involved in improving not only the mechanical but also the electromagnetic and thermal properties of polymeric composites. Also, it is known that filled polymeric composites show interesting properties especially when the fillers are nanosized. In such conditions it is expected that laminate composites formed with filled epoxy will show different properties. These are the results of a trail-and-error study regarding the influence of fillers on the electrical (at first) and mechanical properties of reinforced composites with filled epoxy matrix. Two types of fiber fabric were used as reinforcements and ferrite, talc and CNT were used as fillers. 250 mm long, 120 mm wide and 5-7 mm thick plates of composites were formed in glass moulds. Electrical standard tests and three point bending standard tests were performed.

PL

Ponieważ celem projektowania kompozytów jest zastępowanie metali w różnych zastosowaniach, stawiane wymagania pociągają za sobą poprawę nie tylko właściwości mechanicznych, ale również elektrycznych i cieplnych kompozytów polimerowych. Wiadomo, że napełniane kompozyty polimerowe wykazują interesujące właściwości, zwłaszcza gdy napełniacze mają rozmiary nanomikrometrowe. W pracy przedstawiono wyniki, otrzymane metodą prób i błędów, wpływu napełniaczy na właściwości elektryczne i mechaniczne kompozytów z napełnioną osnową epoksydową. Zastosowano jako umocnienie dwa rodzaje tkanin, natomiast jako napełniaczy użyto ferrytu, talku i nanorurek węglowych. Kompozyty o wymiarach 250 mm długości, 120 mm szerokości i 5-7 mm grubości formowano w formach szklanych. Przeprowadzono standardowe testy elektryczne oraz próby trójpunktowego zginania.

12

Selected mechanical properties of fabric reinforced composites with talc and carbon black filled matrix

51%

Andrei G. , Cîrciumaru A. , Bîrsan I.-G. , Diaconu N.

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tom R. 9, nr 4

347-351

EN

Fillers are used in order to improve the properties of polymeric composites. It is possible to use the filled polymer in order to form reinforced composites. In both cases it is assumed that using some strategies the fillers' particles are uniformly distributed in the volume of matrix. Clearly, using filled polymers, the mechanical properties of formed composites will be changed. In this study, the emphasis is on finding out the influence of filled layer distribution on the properties of formed composite. Plates of reinforced composites were formed using mixed kevlar and carbon fiber fabric and epoxy resin as matrix. As fillers talc and carbon black were used. Three point bending tests were performed in order to point out the effect of filler and fillers' distributions on mechanical properties of materials.

PL

Napełniacze są stosowane w celu poprawy właściwości kompozytów polimerowych. Możliwe jest zastosowanie polimeru napełnionego do kształtowania kompozytów umacnianych. W obu przypadkach zakłada się, że cząstki napełniaczy są jednorodnie rozmieszczone w objętości osnowy. Niewątpliwie użycie napełnionych polimerów będzie zmieniać właściwości mechaniczne tworzonych kompozytów. Prezentowane badania miały na celu określenie wpływu rozmieszczenia wypełnionych warstw na właściwości utworzonych kompozytów. Płyty kompozytowe wytworzono przy zastosowaniu mieszanych tkanin z włókien kevlarowych i węglowych oraz żywicy epoksydowej jako osnowy. Jako napełniacze zastosowano talk i sadzę. Testy trójpunktowego zginania przeprowadzono w celu wykazania wpływu napełniacza i jego rozmieszczenia na właściwości mechaniczne materiałów.