Showing papers on "Flexural strength published in 2005"
TL;DR: In this paper, the applicability of basalt fiber as a strengthening material for structural concrete members through various experimental works for durability, mechanical properties, and flexural strengthening was investigated, and the results showed that two layers of the basalt fibre sheets were thought to be better strengthening scheme.
Abstract: This study investigates the applicability of the basalt fiber as a strengthening material for structural concrete members through various experimental works for durability, mechanical properties, and flexural strengthening. The basalt fiber used in this study was manufactured in Russia and exhibited the tensile strength of 1000 MPa, which was about 30% of the carbon and 60% of the high strength glass (S-glass) fiber. When the fibers were immersed into an alkali solution, the basalt and glass fibers lost their volumes and strengths with a reaction product on the surface but the carbon fiber did not show significant strength reduction. From the accelerated weathering test, the basalt fiber was found to provide better resistance than the glass fiber. However, the basalt fiber kept about 90% of the normal temperature strength after exposure at 600 °C for 2 h whereas the carbon and the glass fibers did not maintain their volumetric integrity. In the tests for flexural strengthening evaluation, the basalt fiber strengthening improved both the yielding and the ultimate strength of the beam specimen up to 27% depending on the number of layers applied. From the results presented herein, two layers of the basalt fiber sheets were thought to be better strengthening scheme. In addition, the strengthening does not need to extend over the entire length of the flexural member. When moderate structural strengthening but high resistance for fire is simultaneously sought such as for building structures, the basalt fiber strengthening will be a good alternative methodology among other fiber reinforced polymer (FRP) strengthening systems.
905 citations
TL;DR: In this paper, multi-walled carbon nanotubes after modified by using a H2SO4 and HNO3 mixture solution were added to cement matrix composites to improve the flexural strength, compressive strength, and failure strain.
829 citations
TL;DR: In this paper, the degree of fiber-matrix adhesion and its effect on the mechanical reinforcement of short henequen fibers and a polyethylene matrix was studied, and the surface treatments were: an alkali treatment, a silane coupling agent and the pre-impregnation process of the HDPE/xylene solution.
Abstract: The degree of fiber–matrix adhesion and its effect on the mechanical reinforcement of short henequen fibers and a polyethylene matrix was studied. The surface treatments were: an alkali treatment, a silane coupling agent and the pre-impregnation process of the HDPE/xylene solution. The presence of Si–O–cellulose and Si–O–Si bonds on the lignocellulosic surface confirmed that the silane coupling agent was efficiently held on the fibres surface through both condensation with cellulose hydroxyl groups and self-condensation between silanol groups. The fiber–matrix interface shear strength (IFSS) was used as an indicator of the fiber–matrix adhesion improvement, and also to determine a suitable value of fiber length in order to process the composite with relative ease. It was noticed that the IFSS observed for the different fiber surface treatments increased and such interface strength almost doubled only by changing the mechanical interaction and the chemical interactions between fiber and matrix. HDPE-henequen fiber composite materials were prepared with a 20% v/v fiber content and the tensile, flexural and shear properties were studied. The comparison of tensile properties of the composites showed that the silane treatment and the matrix-resin pre-impregnation process of the fiber produced a significant increase in tensile strength, while the tensile modulus remained relatively unaffected. The increase in tensile strength was only possible when the henequen fibers were treated first with an alkaline solution. It was also shown that the silane treatment produced a significant increase in flexural strength while the flexural modulus also remained relatively unaffected. The shear properties of the composites also increased significantly, but, only when the henequen fibers were treated with the silane coupling agent. Scanning electron microscopy (SEM) studies of the composites failure surfaces also indicated that there is an improved adhesion between fiber and matrix. Examination of the failure surfaces also indicated differences in the interfacial failure mode. With increasing fiber–matrix adhesion the failure mode changed from interfacial failure and considerable fiber pull-out from the matrix for the untreated fiber to matrix yielding and fiber and matrix tearing for the alkaline, matrix-resin pre-impregnation and silane treated fibers.
769 citations
TL;DR: In this paper, a biomimetic approach was used to undertake self-repair and visual enhancement of impact damage by a bleeding action from filled hollow fibres, and the results of flexural testing have shown that a significant fraction of the flexural strength lost after impact damage can be restored by the selfrepairing effect of a healing resin stored within hollow fibers.
694 citations
TL;DR: In this article, a set of material property data is established based on published physical, mechanical, and thermal properties of alumina specimens that conform to the constraints of the material specification.
Abstract: Results of a data evaluation exercise are presented for a particular specification of sintered alpha-alumina (mass fraction of Al2O3, ≥0995; relative density (rho/rhotheoretical), ≥098; and nominal grain size, 5 μm) A comprehensive set of material property data is established based on published physical, mechanical, and thermal properties of alumina specimens that conform to the constraints of the material specification The criteria imposed on the properties are that the values should be derived from independent experimental studies, that the values for physically related properties should be mutually self-consistent, and that the sets of values should be compatible with established material property relations The properties assessed in this manner include crystallography, thermal expansion, density, sound velocity, elastic modulus, shear modulus, Poisson's ratio, bulk modulus, compressive strength, flexural strength, Weibull characteristic strength, Weibull modulus, tensile strength, hardness, fracture toughness, creep rate, creep rate stress exponent, creep activation energy, friction coefficient, wear coefficient, melting point, specific heat, thermal conductivity, and thermal diffusivity
669 citations
TL;DR: The ring opening chemistry of the Siloranes enables at the first time shrinkage values lower than 1 vol% and mechanical parameters as E-Modulus and flexural strength comparable to those of clinically well accepted methacrylate based composites.
623 citations
TL;DR: In this article, a new kind of high-strength composite was manufactured using microfibrillated cellulose (MFC) derived from kraft pulp, and the Young's modulus (E) and bending strength (σb) of composites using phenolic resin as binder achieved values up to 19 GPa and 370 MPa, respectively, with a density of 1.45 g/cm2.
Abstract: A completely new kind of high-strength composite was manufactured using microfibrillated cellulose (MFC) derived from kraft pulp. Because of the unique structure of nano-order-scale interconnected fibrils and microfibrils greatly expanded in the surface area that characterizes MFC, it was possible to produce composites that exploit the extremely high strength of microfibrils. The Young’s modulus (E) and bending strength (σb) of composites using phenolic resin as binder achieved values up to 19 GPa and 370 MPa, respectively, with a density of 1.45 g/cm2, exhibiting outstanding mechanical properties for a plant-fiber-based composite.
543 citations
TL;DR: In this article, the authors present a study on the flexural wave propagation in a single-walled carbon nanotube through the use of the continuum mechanics and the molecular dynamics simulation based on the Terroff-Brenner potential.
Abstract: The paper presents the study on the flexural wave propagation in a single-walled carbon nanotube through the use of the continuum mechanics and the molecular dynamics simulation based on the Terroff-Brenner potential. The study focuses on the wave dispersion caused not only by the rotary inertia and the shear deformation in the model of a traditional Timoshenko beam, but also by the nonlocal elasticity characterizing the microstructure of carbon nanotube in a wide frequency range up to THz. For this purpose, the paper starts with the dynamic equation of a generalized Timoshenko beam made of the nonlocal elastic material, and then gives the dispersion relations of the flexural wave in the nonlocal elastic Timoshenko beam, the traditional Timoshenko beam and the Euler beam, respectively. Afterwards, it presents the molecular dynamics simulations for the flexural wave propagation in an armchair (5,5) and an armchair (10,10) single-walled carbon nanotubes for a wide range of wave numbers. The simulation results show that the Euler beam holds for describing the dispersion of flexural waves in the two single-walled carbon nanotubes only when the wave number is small. The Timoshenko beam provides a better prediction for the dispersion of flexural waves in the two single-walled carbon nanotubes when the wave number becomes a little bit large. Only the nonlocal elastic Timoshenko beam is able to predict the decrease of phase velocity when the wave number is so large that the microstructure of carbon nanotubes has a significant influence on the flexural wave dispersion.
479 citations
TL;DR: In this paper, the strength potential of nylon-fiber-reinforced concrete was investigated versus that of polypropylene fiber reinforced concrete, at a fiber content of 0.6 kg/m 3.
477 citations
TL;DR: In this article, the dynamic and static mechanical properties of randomly oriented intimately mixed short banana/sisal hybrid fiber reinforced polyester composites were determined, and the experimental results confirmed the quantitative characterisation obtained from static and dynamic mechanical analysis.
471 citations
TL;DR: The present study suggests that sandblasting and grinding may be recommended to increase the strength of dental Y-TZP, provided they are not followed by heat treatment.
TL;DR: In this article, the effect of concentration of NaOH solution on the mechanical and chemical properties of the metakaolinite-based geopolymer was investigated by means of X-ray diffraction, scanning electron microscopy (SEM) and infrared spectrometry (IR).
TL;DR: The use of self-reinforcement by larger elongated grains in silicon nitride ceramics requires judicious control of the microstructure to achieve high steady-state toughness and high fracture strength as discussed by the authors.
Abstract: The use of self-reinforcement by larger elongated grains in silicon nitride ceramics requires judicious control of the microstructure to achieve high steady-state toughness and high fracture strength. With a distinct bimodal distribution of grain diameters, such as that achieved by the addition of 2% rodlike seeds, the fracture resistance rapidly rises with crack extension to steady-state values of up to 10 MPa{center_dot}m{sup 1/2} and is accompanied by fracture strengths in excess of 1 GPa. When the generation of elongated reinforcing grains is not regulated, a broad grain diameter distribution is typically generated. While some toughening is achieved, both the plateau (steady-state) toughness and the R-curve response suffer, and the fracture strength undergoes a substantial reduction. Unreinforced equiaxed silicon nitride exhibits the least R-curve response with a steady-state toughness of only 3.5 MPa{center_dot}m{sup 1/2} coupled with a reduced fracture strength.
TL;DR: In this paper, the advantages and disadvantages of stress-based and energy-based models of interfacial debonding and corresponding adhesional parameters (local interfacial shear strength, critical energy release rate, adhesion pressure) are discussed.
TL;DR: The shape memory effect in polymer networks intended for biomedical, and specifically cardiovascular, applications is examined, thermomechanical results are discussed in light of potential biomedical applications, and a prototype device is presented.
Abstract: We examine the shape memory effect in polymer networks intended for biomedical, and specifically cardiovascular, applications. The polymers were synthesized by photopolymerization from a tert-butyl acrylate monomer with a diethyleneglycol diacrylate crosslinker. Three-point flexural tests were used to systematically investigate the thermomechanics of shape storage (predeformation) and shape recovery. The glass transition temperature, T(g), of the polymers was determined to be approximately 65 degrees C. The polymers show 100% strain recovery, at low and high predeformation temperatures, up to maximum strains of approximately 80%. The polymers show a sigmoidal free strain recovery response as a function of increasing temperature at a constant heating rate. Free strain recovery was determined to depend on the temperature during predeformation; lower predeformation temperatures (T T(g)) is sigmoidal. The isothermal free strain recovery rate was found to increase with increasing temperature or decreasing predeformation temperature. The thermomechanical results are discussed in light of potential biomedical applications, and a prototype device is presented.
TL;DR: In this paper, a systematic study has been carried out to investigate matrix properties by introducing micro-and nanosized SiC fillers into an epoxy matrix and the resulting structural composites have been tested under flexural and tensile loads to evaluate mechanical properties.
TL;DR: In this paper, the isolated contribution of silica fume on the tensile strengths of high performance concrete (HPC) is investigated. But the results indicate that the optimum replacement percentage is not a constant one but depends on the water-cementitious material (w/cm) ratio of the mix.
TL;DR: In this article, a study on the reinforcement of existing wood elements under bending loads through the use of FRP materials is presented, in which an experimental program based on a four-point bending test configuration is proposed to characterize the stiffness, ductility and strength response of this article-reinforced wood beams.
Abstract: This paper presents a study on the reinforcement of existing wood elements under bending loads through the use of FRP materials. An analytical investigation was first conducted on the behavior of a generic FRP-reinforced wood section. This study, in turn, led to a numerical procedure based on non-linear wood properties, suitable for application in the design of FRP reinforcement of old, pre-existing wood beams under varying configurations of intervention layouts and materials. An experimental programme based on a four-point bending test configuration is proposed to characterize the stiffness, ductility and strength response of FRP-wood beams. Mechanical tests on the reinforced wood showed that external bonding of FRP materials may produce increases in flexural stiffness and capacity. The FRP composite material was made of High Tensile Carbon monodirectional reinforcing fabrics embedded in an epoxy resin matrix. This reinforcing method can be applied without necessitating the removal of the overhanging part of the pre-existing wood structure, thus maintaining the original historical structure. In addition, a beam non-linear model was proposed to predict ultimate load. At the end of this paper results of the experimental programme are presented and used for comparison with the numerical procedure.
TL;DR: In this paper, an analysis of impact fracture surfaces performed on polyester B composites clearly demonstrated better interfacial adhesion between fibre and matrix, and a moisture absorption test also showed that polyester b composites gave the most superior bonding and adhesion of all the other polyester-kenaf composites.
TL;DR: In this article, it is demonstrated how thin layers of concrete with textile reinforcement can be used for strengthening for reinforced concrete (RC) members, and the enhancement of bending capacity is illustrated with flexural strengthened RC-slabs.
Abstract: Using test results it is demonstrated how thin layers of concrete with textile reinforcement can be used for strengthening for reinforced concrete (RC) members. The enhancement of bending capacity is illustrated with flexural strengthened RC-slabs. It is also established that the shear capacity may be increased through strengthening of RC-beams, and that properties of serviceability are improved, in particular the reduction of deflections and crack widths. The detailed problem of force transfer from the textile reinforced strengthening layer to the existing concrete of RC-members is then explained and subsequently the relation between the transferable bond force and the associated bond length is shown. A simple model for dimensioning the flexural strengthening of RC-slabs is presented and necessary model extensions are additionally pointed out.
TL;DR: In this article, the effect of fiber length and fiber fraction on shrinkage, compressive strength, flexural strength and shear strength was investigated in composite soil reinforced with chopped barley straw, using four different soils.
Abstract: The shortage of low cost and affordable housing in Algeria has led to many investigations into local low cost construction materials. Earth construction is widespread in desert and rural areas but suffers from shrinkage cracking, low strength and lack of durability. The use of natural and vegetable fibres could improve its performance. This paper reports on an experimental study to investigate a composite soil reinforced with chopped barley straw, using four different soils. The effect of fibre length and fibre fraction on shrinkage, compressive strength, flexural strength and shear strength was investigated. Preliminary tests to enhance durability by using different waterproof renders are also briefly reported.
TL;DR: In this paper, specific strength, moduli and fracture toughness of varied microstructures of syntactic foam was evaluated by using 3M Scotchlite ™ K15 and K46 glass bubbles, and Phenoset BJO-093 hollow phenolic microspheres.
TL;DR: The results from the simultaneous measurement of shrinkage stress and conversion showed that the onset ofshrinkage stress coincides with the delayed gel point conversion, which is predicted to be 41% for the 3:4 stoichiometric PETMP/TATATO resin composition.
TL;DR: In this paper, the use of fiber reinforced cement composites (HPFRCCs) in beam-column connections allowed total elimination of joint transverse reinforcement while leading to outstanding damage tolerance.
Abstract: Tensile strain-hardening, high-performance fiber-reinforced cement composites (HPFRCCs) are being more commonly used in earthquake-resistant structures. This article discusses the applications for HPFRCCs, including for members with shear-dominated response such as beam-column connections, low-rise walls, and coupling beams, as well as flexural members subjected to large displacement reversals. The author determines that HPFRCC materials are effective in increasing shear strength, displacement capacity, and damage tolerance in members subjected to large inelastic deformations. The use of HPFRCCs in beam-column connections allowed total elimination of joint transverse reinforcement while leading to outstanding damage tolerance. Similarly, HPFRCC low-rise walls exhibited drift capacities larger than 2.0% with only minor damage at drifts ranging between 1.0 to 1.5%. The author concluded that one of the most encouraging results was observed in HPFRCC flexural members unreinforced in shear, which sustained reversed cyclic shear stresses as high as 2.7 MPa with up to 6.0% plastic hinge rotation. The use of HPFRCC materials leads to an increase in displacement capacity and outstanding damage tolerance, which make these composites attractive for reducing the need for costly post-earthquake repairs.
TL;DR: In this article, the results of the variation in chemical composition and tensile strength of coir, sisal, jute and Hibiscus cannabinus fibres, when they are subjected to alternate wetting and drying and continuous immersion for 60 days in three mediums (water, saturated lime and sodium hydroxide) were determined after 28 days of normal curing.
Abstract: This paper presents the results of the variation in chemical composition and tensile strength of coir, sisal, jute and Hibiscus cannabinus fibres, when they are subjected to alternate wetting and drying and continuous immersion for 60 days in three mediums (water, saturated lime and sodium hydroxide). Compressive and flexural strengths of cement mortar (1:3) specimens reinforced with dry and corroded fibres were determined after 28 days of normal curing. From the results it is observed that there is substantial reduction in the salient chemical composition of all the four fibres, after exposure in the various mediums. Coir fibres are found to retain higher percentages of their initial strength than all other fibres, after the specified period of exposure in the various mediums. The compressive and flexural strengths of all natural fibre reinforced mortar specimens using corroded fibres are less than the strength of the reference mortar (i.e. without fibres) and fibre reinforced mortar specimens reinforced with dry natural fibres.
TL;DR: In this paper, the coupling efficiency of seven coupling agents in wood-polymer composites (WPC) was investi- gated in a study, and the improvement on the interfacial bonding strength, flexural modulus, and other mechanical properties of the resultant wood fiber/high-density polyeth- ylene (HDPE) composites was mainly related to the coupling agent type, function groups, molecular weight, con- centration, and chain structure.
Abstract: The coupling efficiency of seven coupling agents in wood-polymer composites (WPC) was investi- gated in this study. The improvement on the interfacial bonding strength, flexural modulus, and other mechanical properties of the resultant wood fiber/high-density polyeth- ylene (HDPE) composites was mainly related to the cou- pling agent type, function groups, molecular weight, con- centration, and chain structure. As a coupling agent, mal- eated polyethylene (MAPE) had a better performance in WPC than oxidized polyethylene (OPE) and pure polyeth- ylene (PPE) because of its stronger interfacial bonding. A combination of the acid number, molecular weight, and concentration of coupling agents had a significant effect on the interfacial bonding in WPC. The coupling agents with a high molecular weight, moderate acid number, and low concentration level were preferred to improve interfacial adhesion in WPC. The backbone structure of coupling agents also affected the interfacial bonding strength. Com- pared with the untreated composites, modified composites improved the interfacial bonding strength by 140% on max- imum and the flexural storage modulus by 29%. According to the statistical analysis, 226D and 100D were the best of the seven coupling agents. The coupling agent performance was illustrated with the brush, switch, and amorphous struc- tures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 93-102, 2005
TL;DR: In this paper, the strength properties of high-volume fly ash (HVFA) roller compacted and superplasticised workable concrete cured at moist and dry curing conditions were evaluated.
TL;DR: In this article, the authors examined four types of date palm surface fibres and determined their mechanical and physical properties, such as strength, continuity index, toughness and microstructure, as a function of curing in water and in a hot-dry climate.
Abstract: The study examines four types of date palm surface fibres and determines their mechanical and physical properties. In addition, the properties of date palm fibre-reinforced concrete, such as strength, continuity index, toughness and microstructure, are given as a function of curing in water and in a hot-dry climate. The volume fraction and the length of fibres reinforcement were 2–3% and 15–60 mm respectively. Increasing the length and percentage of fibre-reinforcement in both water and hot dry curing, was found to improve the post-crack flexural strength and the toughness coefficients, but decreased the first crack and compressive strengths. In hot-dry climate a decrease of first crack strength with ageing was observed for each concrete type. Water curing decreased the global degree of the voids and cracks with time for each concrete type, but increased it in hot-dry climate.
TL;DR: Within clinically relevant power densities, not only energy density but also power density per se had significant influence on resin composite properties.
Abstract: According to the "total energy concept", properties of light-cured resin composites are determined only by energy density because of reciprocity between power density and exposure duration. The kinetics of polymerization is complex, and it was hypothesized that degree of cure, flexural strength, and flexural modulus were influenced not only by energy density, but also by power density per se. A conventional resin composite was cured at 3 energy densities (4, 8, and 16 J/cm(2)) by 6 combinations of power density (50, 100, 200, 400, 800, and 1000 mW/cm(2)) and exposure durations. Degree of cure, flexural strength, and flexural modulus increased with increasing energy density. For each energy density, degree of cure decreased with increasing power density. Flexural strength and modulus showed a maximum at intermediate power density. Within clinically relevant power densities, not only energy density but also power density per se had significant influence on resin composite properties.
TL;DR: In this paper, the effect of a low-molecular weight, maleated type coupling agent on the mechanical properties of polypropylene composites with various natural fibers such as old newsprint, kraft pulp and hemp were studied.
Abstract: Natural fibers are potentially a high-performance and non-abrasive reinforcing fiber source. In this study, mechanical properties of polypropylene (PP) composites with various natural fibers such as old newsprint, kraft pulp and hemp were studied. The effect of a low-molecular weight, maleated type coupling agent, on the mechanical properties of these natural fiber-filled PP composites was also investigated and the results showed that this can be used as a good interface modifier for improving the strength properties of the PP-filled composites and the optimum level of the coupling agent was found to be around 3-4 percentage by weight of the composite. Kraft pulp and hemp fiber-filled composites showed better tensile, flexural and un-notched impact strength compared to the glass fiber-filled composites at the same fiber loading. Hybrid composite produced using 10 wt% of glass fiber and 30 wt% of hemp fiber showed only a marginal improvement in the mechanical properties.