•Relatively high crystallinity index (52.6%) was found in Furcraea foetida fiber.•High cellulose (68.35wt.%) content.•Low density (778kg/m3) of FF promotes the low weight applications.•The FF ...cellulose degradation at 320.5°C evident by thermo gravimetric analysis.
The exploration of new natural fibers in the field of polymer composites can contribute to increase the invention of natural reinforcements and expand their use in possible applications. In the present work, the physico-chemical, thermal, tensile and morphological properties of Furcraea foetida (FF) fiber are presented for the first time. Chemical analysis results shows that FF has relatively higher cellulose (68.35%) with lower hemicelluloses (11.46%) and lignin (12.32%). Structural analysis of FF was conducted by Fourier transform infrared and 13C (CP-MAS) nuclear magnetic resonance spectroscopy. X-ray diffraction (XRD) analysis evidenced that FF has crystallinity index of 52.6% with crystalline size of 28.36nmThe surface morphology of FF was investigated by scanning electron microscopy (SEM), energy dispersive X-ray micro analyzer (EDX) and atomic force microscopy (AFM). The thermogravimetric analysis (TGA) reveals thermal constancy of the fiber upto 320.5°C with the kinetic activation energy of 66.64kJ/mol, which can be used as reinforcements in thermoplastic green composite whose working temperatures is below 300°C. The FF results were compared with those of other natural fibers, and indicated as a suitable alternative source for composite manufacture.
Fibre-reinforced composite materials have gained an increasing success, mostly for strengthening, retrofitting, and repairing existing structures. However some problems may arise with the use of ...traditional FRP (Fiber Reinforced Polymer), particularly when the compatibility with the substrate and the reversibility of the intervention are required, as in case of cultural heritage buildings, or specific exposition conditions may compromise the long term effectiveness of the reinforcement, as in presence of high temperature and humidity. Starting from these considerations new composite materials are emerging as a more effective solution in certain fields of application and under specific service conditions; in this context, mortar-based composite systems, consisting of one or more layers of uni- or bi-directional fibre nets embedded in cement/lime-based matrix layers, can be used as reinforcement of both concrete and masonry structures. However, the research work dealing with these emerging materials and their performances when used as a strengthening system for existing structures is still limited. Both experimental and theoretical investigations are needed in order to deliver reliable design methodologies. In this work, a Round Robin Test aimed to the characterization of both bond with the existing substrate and tensile performance of glass fabric (in the form of grids) coupled with inorganic mortar matrices is presented. The investigation was conducted at fifteen laboratories involved in the RILEM Technical Committee 250-CSM (Composites for the Sustainable Strengthening of Masonry). With the aim of studying the bond behaviour between Fabric Reinforced Cementitious Matrix (FRCM) composites and masonry substrate, single and double lap shear tests were carried out on brick-masonry prisms. Results provide useful informations about the mechanical properties, the bond capacity and the failure mechanisms of different commercially available glass FRCM systems. Finally, critical aspects are underlined to address the progress of the research work.
The microstructure, mechanical and corrosion properties of a cost-effective face-center cubic (fcc)-structured Co-free Fe50Mn27Ni10Cr13 high entropy alloy (HEA), which is developed here, has been ...studied using a comprehensive approach of ex-situ tensile tests, in-situ SEM/EBSD tensile measurements, ex-situ TEM studies, Tafel polarization, and immersion tests. After thermo-mechanical treatments, this alloy exhibits a tensile strength of 463 MPa and elongation of over 40% which are comparable to other expensive HEAs. A miniature-designed dog-bone specimen for in-situ SEM/EBSD measurements was successfully employed to study the underlying deformation mechanisms of the alloy, exhibiting the double-fiber 111 and 001 texture typical of TWIP steels. Nano-, meso- and macro-scale studies revealed that the excellent combination of strength and ductility of this newly-developed cost-effective fcc-structured HEA is originated from the formation of stacking faults and nano-twins during tensile deformation. This newly-developed alloy also exhibits good corrosion resistance in the following solutions: NaCl > NaOH >H2SO4 > HCl. The corrosion resistance was mostly found to be dependent on the amount of Mn-oxide in the passive film formed on the surface of the alloy. This work, following the non-equiatomic HEA design strategy, develops a cost-effective HEA with a good combination of mechanical with corrosion properties, which will trigger more investigations.
•Novel Fe50Mn27Ni10Cr13 HEA exhibits a 111 and 001 double-fiber texture after deformation.•Successful in-situ EBSD/SEM tensile-test at higher strains.•Dislocation glide and mechanical twinning deformation mechanisms.•Good corrosion response as follows: NaCl > NaOH > H2SO4 > HCl.
•Miniaturized Tensile Test (MTT) is extremely sensitive to specimen size effects and data deviation or scattering in experiment.•Guidelines for small specimen design are summarized and extended.•Data ...processing techniques can help to optimize the design of small specimens and reduce the errors in MTT.
Miniaturized Tensile Test (MTT), as an important type of Small Specimen Test Technology (SSTT), has gained increasing attentions in the nuclear industry and other fields. However, MTT faces great challenges because the test results may deviate from standard specimens due to specimen size effects and may exhibit large scatters caused by fabrication imperfection. In order to improve the reliability of MTT, many efforts have been made during the past several decades, and various issues regarding on the MTT have been studied. This paper reviews and analyzes the previous studies of specimen size effects on mechanical properties and summarizes the design guidelines for MTT proposed in previous literatures. The previous specimen designs for standard and small specimens have also been reviewed briefly. The SSTT including specimen preparation, testing operation, measurements of stress and strain also have been addressed in this study, since the testing results of SSTT are sensitive to dimensional deviations, surface defects, measurement errors, etc. In addition, data analysis schemes such as elongation conversion with simple formulae or even FEM simulation have been discussed.
In this paper, an experimental and statistical analysis was carried out from hollow concrete blocks. Firstly, 30 blocks were tested under compression force (
vertical
-direction). After, 60 blocks ...were studied under the splitting test from ASTM–C–1006 and, later a direct tensile test was applied to other 60 blocks. The blocks, in the direct tensile test, were subjected to a tensile force in the
horizontal
directions (30 in each directions). For the direct tensile test, a special test procedure was developed. The results show that, independently of the test procedure applied (direct or splitting), the tensile strength has a significant statistical difference between both horizontal directions (
x
and
y
), evidencing the non–isotropy character from the hollow concrete blocks. Splitting method results was significantly smaller in the
x
–direction than by the direct method, contrary in the
y
–direction. A statistical analysis of parametric and non-parametric hypothesis tests was used to determine the significance levels between both test procedures. In addition, this article concludes with a discussion between the compressive and tensile strength relationships in the orthogonal directions of the hollow concrete blocks.
Graphical abstract
The recrystallized and pre-deformed CoCrNi medium-entropy alloy (MEA), introduced with high-density deformation twins, exhibits an unprecedented high yield strength up to 2.1 GPa. We found that the ...highly distorted deformation twins provide strong resistance to crack propagation and the activated dislocation motion accommodates the further plastic deformation. Our in situ tensile tests of pre-notched sample reveal that crack propagation through strain localization band eventually leads to fracture. This result offers new insights on design and processing of MEA for desired mechanical performance.
•A pre-deformation process is introduced to prepare CoCrNi MEA in liquid nitrogen environment, resulted in highly twinned microstructure.•This highly twinned MEA exhibits an ultra-high strength up to 2.1 GPa and considerable crack resistance.•A plastic zone exists in the vicinity of the crack tip, which is ascribed to highly distorted DTs and activated dislocations.
The deformation mechanisms associated with uniaxial tensile testing are studied by conducting tensile experiments of an FeCrAl alloy using scanning electron microscopy (SEM) coupled with electron ...backscattered diffraction (EBSD). Prior to the deformation, investigated alloy was consisting grain and precipitate size of ∼63.0 μm and ∼6.7 μm, respectively. The recorded SEM micrographs and EBSD data at increasing levels of strains revealed the complex phenomena of slip bands’ formation in the presence of surface grain morphology evolution and their (001), (110) and (111) crystallographic planes distortions. The grains with orientation (110)||tensile direction (TD) shows higher shape change; however, (001)||TD and (111)||TD oriented grains show higher lattice gradient formation. Extracted information from the EBSD indicates that the crystallographic rotations drive towards specific, fiber-like texture in relation to the loading direction. Postmortem analysis of the recorded microstructure during the tensile deformation explains the phenomena of crack formation in the hard-intermetallic particles before the ultimate tensile strength (UTS). However, after the UTS, pores were identified in the neck that resulted from extensive plastic deformation. In-depth analysis was carried out to identify the cause of cracks and pores formation phenomena during the tensile test.
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Flexible Rutherford cables are needed to realize high field superconducting magnets with A15 conductors based on the react-and-wind (R&W) technology. Aiming such an application, ultra-thin A15 ...composite wires with a diameter of 0.03-0.05 mm have been developed by the National Institute for Materials Science (NIMS). Mechanical properties of such ultra-thin Nb 3 Sn wires were evaluated to determine the cabling parameters and mechanical analysis of twisted cables. Tensile tests were performed at room temperature for 0.05 mm-thick Nb 3 Sn wires before and after heat treatment for the first time. Basic mechanical parameters such as 0.2% proof strength and fracture strength were evaluated from a stress-strain curve. Young's modulus of such a thin wire was determined from unlading and reloading slopes of a load-stroke curve for the specimens with different gauge lengths. Fracture strain was estimated without using extensometers and strain gauges by correcting for machine deformation. Based on these results, we concluded that a simple technique to measure stress-strain curves for ultra-thin Nb 3 Sn wires was able to be established.
Purpose The purpose of this study was to clarify the biomechanical properties of the capsule in a normal rat knee joint. Participants and Methods Femur-capsule-tibia composite specimens prepared from ...the hindlimbs of five 8-week-old male Wistar rats were subjected to tensile testing. Results The waveforms of the length-tension curves showed steep and repeated declines in some individual rats (three out of five samples) while in others (two out of five samples) they were not repeated. Conclusion It was found that some capsules in the rat knee fossa had a mixture of cruciate ligament-like fibers while others did not.
In this work, a precipitation strengthened high entropy alloy was subjected to thermo-mechanical process in order to homogenize the grain microstructure. Tensile tests from room temperature to ...1000 °C were conducted; microstructures were observed by scanning electron microscope and transmission electron microscope. Formation of cellular precipitate along grain boundaries was observed and could be related to hot tensile ductility drop at 750 °C (1023 K). Experimental analysis has indicated that driving force for the formation of cellular precipitates could be resulted from the chemical instability of supersaturation after annealing and migration of grain boundaries, and this phenomenon could be suppressed either through alloy design to increase gamma-prime solvus, and to hinder the migration of grain boundaries. This study serves as a guideline to design composition and thermo-mechanical process for precipitation strengthened high entropy alloys.
•A precipitation strengthened high entropy alloy was subjected to thermos-mechanical process.•Chemical instability of supersaturation and migration of grain boundaries can cause formation of cellular precipitate.•Tensile ductility drop occurred around 750 °C in present high entropy alloy due to cellular precipitate.•Cellular precipitate does not affect tensile ductility at room temperature.•The formation of cellular precipitate can be suppressed by alloy design and cooling rate during heat-treatment.
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