Search

The aim of this research is the production of epoxy resin composites reinforced by birch, palm, and eucalyptus fibers with resin transfer molding technique and molded fiber production technique combination. The tensile stress of birch, palm, and eucalyptus reinforced epoxy composites were determined as 29.53, 42.24, and 45.28 MPa, respectively. Bending stress of birch, palm and eucalyptus reinforced epoxy composites were found as 58.83, 68.58, and 79.92 MPa, respectively. The birch epoxy composite had 0.105 J impact energy while palm and eucalyptus epoxy composites were determined as 0.130 and 0.124 J, respectively. It is clearly observed that fiber type was very effective on the mechanical properties of composites. The results of studies showed that molded fiber production method had a very promising future for the development of natural fiber reinforced composites. © 2019 Elsevier Ltd

Thermoset composites have a wide range of applications in the automotive, defense and aerospace industries. The development of strength and mechanical properties of composites is very important. In this work, two different additives as ceramic nanoclay and polyamide powders were added to E-glass reinforced epoxy resin composites in various weights 0.5 wt%, 1.0 wt% and 2.0 wt%. The effects of additives on the mechanical properties of composites were determined experimentally. In addition, mixtures of these additives were also used and the efficacy of each was compared. The positive effects of additives were observed. As a result, it was found that the tensile, buckling and compressive strengths of composites increased significantly. © 2019 Polish Academy of Sciences. All rights reserved.

In this experimental study, we investigated the effects of core yarn diameter and cover yarn type on the mechanical properties of composite yarns produced using a hollow spindle twisting machine according to the method of covering. Composite yarns containing stainless steel (SS) metal wires with diameters of 50 mu m and 100 mu m were produced with seven different cover yarns varying in their raw material and structure. These cover yarns were as follows: polypropylene, cotton, core-spun polyester/cotton, continuous filament polyester, continuous filament polyamide 6.6, core-spun polyester/polyester, and polyester cut fibre yarns. The mechanical properties measured were tensile behaviour and stiffness. According to the findings of the statistical analyses performed using the experimental values, the core yarn diameter, cover yarn type and the interactions of these factors were all significant factors affecting the tenacity, elongation at break, work of rupture and stiffness properties of the composite yarns. Composite yarns containing continuous filament polyamide 6.6 cover yarn showed higher tenacity values, while the maximum elongation at break was obtained for the composite yarns containing continuous filament polyester cover yarn. Both polyester and polyamide 6.6 possessed higher work of rupture values among the other types of cover yarns. An increase in the SS wire diameter resulted in a significant increment in stiffness values. The results of this study implied that it is important to give importance to component yarn types when designing composite yarns with desired physical properties.

The purpose of this work was to synthesize and study magnetic properties of composite films consisting of Gd-Co ferrimagnetic system and Al2O3 dielectric matrix. GdCo-Al2O3 films of different composition were synthesized by magnetron co-sputtering of Gd, Co, and Al2O3 targets in an Ar atmosphere. Investigation of magnetic properties was carried out using a vibrating sample magnetometer in the temperature range from 10 to 300 K. The obtained results showed that in the composite system with a volume of dielectric material exceeding 50% a superparamagnetic state is realized, indicating granular microstructure. In this case, the granules show signs of ferrimagnetic ordering. © Published under licence by IOP Publishing Ltd. Russian Science Foundation, RSF: 18-72-10044 This work was financially supported by the Russian Science Foundation in the framework of research project No. 18-72-10044.

Alginate and cellulose nanofibrils (CNF) are attractive materials for tissue engineering and regenerative medicine. CNF gels are generally weaker and more brittle than alginate gels, while alginate gels are elastic and have high rupture strength. Alginate properties depend on their guluronan and mannuronan content and their sequence pattern and molecular weight. Likewise, CNF exists in various qualities with properties depending on, e.g., morphology and charge density. In this study combinations of three types of alginate with different composition and two types of CNF with different charge and degree of fibrillation have been studied. Assessments of the composite gels revealed that attractive properties like high rupture strength, high compressibility, high gel rigidity at small deformations (Young’s modulus), and low syneresis was obtained compared to the pure gels. The effects varied with relative amounts of CNF and alginate, alginate type, and CNF quality. The largest effects were obtained by combining oxidized CNF with the alginates. Hence, by combining the two biopolymers in composite gels, it is possible to tune the rupture strength, Young’s modulus, syneresis, as well as stability in physiological saline solution, which are all important properties for the use as scaffolds in tissue engineering. (c) 2017 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).

This study examined basic mechanical properties and damage development properties of composite plates produced with carbon nanotubes grown on 2 × 2 twill woven carbon fabric and compared the results with composite materials without carbon nanotubes. The results revealed that there were significant decreases in mechanical properties and characteristic strain values where damage initiation and progression of the composite samples produced from carbon nanotubes grown on fabrics. It was found that Young’s modulus values decreased by 15–17%. Characteristic strain values where damage threshold decreased by 36–53%.

The focus of this paper is to evaluate the mechanical and dynamic mechanical properties of woven jute fabric-reinforced green epoxy composites as a function of modification of jute fibers by enzyme, CO2 pulsed infrared laser and ozone treatments. The treated jute fibers were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Composites were prepared by the hand layup method and compression molding technique and the resin curing process was optimized with the help of differential scanning calorimetry. The treatments resulted in the enhancement of flexural and impact properties. Statistical analysis of mechanical properties of composites, done by one-way analysis of variance, showed significant differences between the results obtained. Dynamic mechanical analysis (DMA) results revealed that treated composites have a higher storage modulus over the range of temperature. A positive shift of loss modulus and tangent delta peaks of treated composites to higher temperature was observed. The reduction in the tangent delta peak height of treated composites was also observed due to improvement in fiber/matrix interfacial adhesion. The degree of interfacial adhesion between the jute fiber and green epoxy was anticipated using the adhesion factor obtained through DMA data. Complex modulus variations and phase behavior of composites was studied by Cole–Cole analysis.

In this study, the mechanical properties of composite materials obtained from carbon and carbon-aramid hybrid woven fabrics produced in different constructions with the same yarn and under the same production conditions were determined, and the effects of weaving structure and hybridization on the mechanical properties were investigated. For this purpose, the geometric properties of carbon fabrics made from 12 K carbon yarn with four different weaving structures and two carbon-aramid hybrid fabrics made of 12 K carbon yarn and aramid yarn with two different structures were defined, and the mechanical properties of the composite materials were investigated under uniaxial tensile loading. The mechanical properties of the composite materials produced from the carbon and carbon-aramid hybrid fabrics were compared. The effects of weaving structure and hybridization on the mechanical properties were determined. Based on the weaving construction, Young’s modulus and the tensile strength declined approximately 34–39% and 24–27%, respectively. However, Young’s modulus was 16–63% higher than the expected value for the hybrid composites.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:29:05Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:43:05Z : No. of bitstreams: 1 2-s2.0-84877979785.pdf: 843233 bytes, checksum: 6070793d5e9f0bfe3d5efb1fd03b29e5 (MD5) Made available in DSpace on 2014-05-27T11:29:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-05-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Lignocellulosic fibers from banana peels were washed with water in order to increase their compatibility with a polymeric matrix, and their properties were compared with unwashed fibers. Washed banana fibers were mixed with high density polyethylene (HDPE) and placed in an injector chamber to produce specimens for tensile tests. Samples of washed bananafibers/HDPE composites were characterized by tensile tests and thermal analysis. The chemical composition of unwashed and washed banana fibers was analyzed by thermogravimetric analysis, scanning electron microscopy, and X-ray diffraction. The treatment with water was effective at removing extractives and increasing the surface roughness, thereby increasing the thermal stability of the fibers. However, results showed that the addition of washed banana fibers decreased the thermal stability of composites, while increasing the melting and crystallization temperatures of composites. The addition of 5 wt% fibers also provided an improvement in mechanical properties of composites in comparison with pure HDPE. Department of Materials and Technology NESP-Univ Estadual Paulista, Guaratinguetá/SP Department of Materials and Technology NESP-Univ Estadual Paulista, Guaratinguetá/SP FAPESP: 06/06740-2