Effect Of Fiber Addition Research Articles

Efficiency of steel and macro-synthetic structural fibers on the flexure-shear behaviour of prestressed concrete beams

The efficiency of steel and structural synthetic fibers on the performance improvement of prestressed concrete (PSC) beams under combined flexure-shear is studied. Results of eleven PSC beams tested at a shear span (a) to depth (d) ratio of five are presented. Discrete steel and macro synthetic structural polyolefin fibers of varying dosages of 0.35%, 0.7% and 1.0% by volume of concrete were used. The effect of fiber addition on overall load – displacement, load- strain, and strain energy absorption capacity of PSC beams is analysed. Other parameters such as shear span to depth ratio (a/d), compressive strength of concrete, prestressing reinforcement ratio were kept constant. The test results portray that the addition of steel fibers stiffens the post cracking response, increases the strain energy absorption capacity more efficiently when compared to macro synthetic fibers (Polyolefin). The failure mode changed from less ductile flexure-shear to more ductile flexure dominant mode at 0.35% and 0.70% volumetric dosage of steel and synthetic fibers, respectively. The strain energy absorption capacity increased by more than 100% at 1.0% fiber addition for both steel and macro-synthetic fibers.

Composites from poly(lactic acid) and bleached chemical fibres: Thermal properties

Poly (lactic acid) (PLA) reinforced with bleached kraft soft wood (BKSW) biocomposites with fibre content up to 35% were processed by kinetic mixing and injection moulding. The cellulosic filler was a commercial chemical bleached kraft soft wood pulps composed of well individualized fibres free from lignin with diameter about 20 μm and length within micron scale. The effect of fibre addition on the thermal properties of composites was investigated using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA) and thermo-mechanical analysis (TMA). In a previous work, it was demonstrated that fibre inclusion on PLA enhanced the modulus as well as the strength. Fibre addition promoted the crystallization of PLA by favouring the heterogeneous nucleation and accelerating the crystallization kinetic, without adversely altering the thermal stability. The DMA analysis confirmed the strong stiffening effect brought by the addition of fibres at the glassy as well as the rubbery domains. The presence of fibres had also a beneficial effect on the dimension stability by lowering the thermal expansion coefficient of composites.

Sedimentation of particles in shear flows of viscoelastic fluids with fibers

We study the effect of fiber additives on rheology and sedimentation of particle suspensions in a base viscoelastic suspending fluid in the case when the suspension is subjected to shear flow. We found experimentally that fiber additives (3–6 mm in length and 8–12 μm in diameter at a mass fraction of 0–0.4%) increase the suspension viscosity and retard the particle sedimentation significantly. At the same mass concentration, long and thin fibers reduce the sedimentation velocity and increase the viscosity to a much greater extent than short and thick fibers. We revealed that both rheology and sedimentation are controlled by a single conformational parameter (overlap parameter) defined as the number of fibers per unit volume multiplied by fiber length cubed.

Effect of fiber addition on fresh and hardened properties of spun cast concrete

The effect of fiber addition on the properties of fresh and hardened concretes casted by centrifugation was investigated. Workability of fresh concrete mixtures, sludge bleeding after centrifuging, and mechanical properties of hardened concrete including compressive and splitting tensile strengths and modulus of elasticity were examined. Post-crack behavior of spun cast concrete was investigated by splitting tensile testing. Considering sanitary sewer environments, concrete resistances against sulfuric acid erosion and sulfate expansion were evaluated. Although the addition of low fiber fractions (below 0.15vol.%) did not significantly affect workability and strength of the spun cast concretes, it enhanced their toughness and resistance against sulfate expansion.

Effects of basalt and glass chopped fibers addition on fracture energy and mechanical properties of ordinary concrete: CMOD measurement

This study investigates fracture behavior of basalt fiber reinforced concrete (BFRC) and glass fiber reinforced concrete (GFRC) comparatively. For this purpose, three-point bending tests were carried out on notched beams produced using BFRC and GFRC with 0.5, 1, 2 and 3kg/m3 fiber contents to determine the value of fracture energy. Fracture energies of the notched beam specimens were calculated by analyzing load versus crack mouth opining displacement (CMOD) curves by the help of RILEM proposal. In addition, microstructural analysis of the three components; cement paste, aggregate, basalt and glass fiber were performed based on the Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy examinations and analysis were discussed. The results showed that the effects of the fiber contents on fracture energy were very significant. The splitting tensile and flexural strength of BFRC and GFRC were improved with increasing fiber content whereas a slight drop in flexural strength was observed for high volume of fiber content. On the other hand, effect of fiber addition on the compressive strength and modulus of elasticity of the mixtures was insignificant.

Thermal properties of palm fiber and palm fiber-reinforced ABS composite

In this study, a natural fiber extracted from the palm tree was used as reinforcement for acrylonitrile butadiene styrene (ABS) matrix composites. Palm fiber (PF)-reinforced ABS (PF-ABS) composites were prepared via injection molding machine. Three sets of samples were prepared for three different mass% (5, 10 and 20 %) of fiber contents. The effect of fiber addition in composite along with the age and different edges of the palm fiber on thermal properties was evaluated with the help of thermogravimetric/differential thermogravimetric, differential thermal analyses and thermomechanical analysis. Thermal stability of the palm fiber is more for 11- to 20-year age group than 5- to 10-year age group for both thin and thick edges of palm fiber. The thermal stability of PF-ABS composites for different mass percentage of fiber is more or less same except 10 % fiber content in PF-ABS composites.

Influence of the incorporation of fibers in biscuit dough on proton mobility characterized by time domain NMR

The effect of fiber addition on the distribution and mobility of protons in biscuits is studied by using low resolution time domain nuclear magnetic resonance (TD-NMR). The proportion of flour is reduced in order to incorporate inulin and oat fiber. NMR temperature dependent experiments are carried out in order to gain insight on the processes occurring in biscuit baking. Proton populations were identified measuring spin–spin relaxation times (T2). The major change in the relaxation profiles upon incorporation of fibers corresponds to mobile water molecules, which appear to be related to dough spreading behavior and biscuit quality. Biscuit samples baked in a commercial oven were studied by two dimensional spin–lattice/spin–spin (T1–T2) relaxation maps. The T1/T2 ratio is used as an indicator of the population mobility, where changes in the mobility of water in contact with flour components as starch, proteins and pentosans are observed.

Mechanical enhancement of cement-stabilized soil by flax fibre reinforcement and extrusion processing

Cement-based materials typically exhibit low tensile strength and their behaviour is generally brittle. Fibres can be added to make composites with enhanced tensile response and toughness. This study focuses on the effects of flax fibre content, mix design and processing on the hardened product properties (density, fibre orientation, surface quality, compressive and tensile strength). Effects of fibre addition on the mechanical performance of cast and extruded flax fibre reinforced composites are compared. Microstructure observations are used to study the influence of processing on fibre–matrix bond, fibre dispersion and fibre orientation. Flax fibre dispersion and orientation are also investigated to understand their effect on mechanical behaviour. In the case of cast materials, fibres do not significantly improve the mechanical behaviour. In contrast, improvement of fibre dispersion and fibre/matrix bond quality due to an extrusion process enhances mechanical performance.

Effect of fiber addition on slow crack growth of a dental porcelain

AimsTo evaluate the effect of the processing method (conventional sintering, S, and heat-pressing, HP) and addition of potassium titanate fibers, PTF, on the microstructure, mechanical properties (flexural strength, σf, and Weibull parameters, m and σ5%), slow crack growth parameters n (stress corrosion susceptibility coefficient), and optical properties (translucency parameter, TP, and opalescence index, OI) of a feldsphatic dental porcelain. MethodsDisks (n=240, Ø12×1mm) of porcelain (Vintage-Halo, Shofu) were produced using S and HP methods with and without addition of 10wt% (conventional sintering) or 5wt% (heat-pressing) of PTF. For the S method, porcelain was sintered in a conventional furnace. In the HP technique, refractory molds were produced by lost wax technique. The porcelain slurry was dry-pressed (3t/30s) to form a cylinder with 12mm (diameter) and 20mm (height), which was heat-pressed for 5min/3.5bar into the mold. Specimens were tested for biaxial flexural strength in artificial saliva at 37°C. Weibull analysis was used to determine m and σ5%. Slow crack growth (SCG) parameters were determined by the dynamic fatigue test, and specimens were tested in biaxial flexure at five stress rates: 10−2, 10−1, 100, 101 and 102MPa/s (n=10), immersed in artificial saliva at 37°C. Parameter n was calculated and statistically analyzed according to ASTM F394-78. Optical properties were determined in a spectrophotometer in the diffuse reflectance mode. ResultsThe highest n value was obtained by the combination of heat-pressing with fiber addition (37.1) and this value was significantly higher than those obtained by both sintered groups (26.2 for control group and 27.7 for sintered with fiber). Although heat-pressing alone also resulted in higher n values compared to the sintered groups, there were no significant differences among them. Fiber addition had no effect on mechanical strength, but it resulted in decreased TP values and increased OI values for both processing methods. Heat-pressing alone was able to reduce the porosity level of the porcelain. ConclusionsAddition of PTF combined with heat-pressing can reduce strength degradation of a dental porcelain compared to sintered materials with or without fibers. Heat-pressing (HP) alone should be considered as a good alternative for clinical cases where high translucency is required.

Steel Fibre Reinforcing Characteristics on the Size Reduction of Fly Ash Based Concrete

The behavior of glued steel fibres in high strength concrete with size reduction properties of concrete has been attempted. Glued steel fibres with both ends hooked having length to diameter ratio of 70 was added at a dosage level of 0.5% to 1.5% by volume fraction. The study was carried out to analyze the effects of fibre addition on the thickness reduction of concrete element. A high strength concrete mixture was designed and various thicknesses of concrete prisms were casted for different volume fraction of steel fibres. The hardened concrete properties were determined based on the mix constituents such as water to binder ratio 0.3 (w/b), superplasticizer dosage, fine to coarse aggregate ratio 0.6 (F/c), and fly ash replacement level at 25% and 50% by weight of binder content. The experimental test results showed that the flexural strength varies with respect to the depth of concrete specimen. It can be observed that the reduction in size up to 10% size containing 25% fly ash with 1.5% steel fibres showed better strength enhancement of 4.70 MPa and 6.69 MPa for 7 days and 28 days, respectively. Also, the addition of steel fibres at higher percentage of fly ash containing 50% showed better improvement in the flexural strength for the size reduction at 5%, when compared to plain concrete beam which exhibited higher stress carrying capacity of 6.08 MPa at 28 days and showed an increase of 7.99%.

Effect of fiber addition on slow crack growth of porcelains

Effect of fiber addition on slow crack growth of porcelains

Effects of fiber addition on antioxidant capacity and nutritional quality of wheat bread

Wholegrain and high fiber foods are recognized as nutritious and healthful products due to their content of dietary fiber, antioxidants and bioactive compounds. In this study, wheat, rye, barley, oat wholegrain flours and two fibers namely cellulose (insoluble fiber) and xanthan gum (soluble fiber) were used to replace a portion of wheat flour in pan bread to study effects of fibers on phenolic compounds, antioxidant capacity, dietary fiber fractions, and starch digestibility in vitro. Incorporation of wholegrain flours increased free and bound phenolics and antioxidant capacity of all the breads examined to various extent depending on the source of fiber. Additionally, soluble, insoluble and total dietary fiber fractions and total minerals increased with the addition of wholegrain flours or fibers. Rapidly and slowly digestible and resistant starches were not significantly influenced by adding wholegrain flours or fibers to breads. The study demonstrates the importance of enriching wheat bread with wholegrain flours to boost antioxidants and dietary fibers. On the other hand, more research is required to better understand impact of wholegrain flours or fiber on starch digestibility in vitro and glycemic response.

Effect of Fiber Addition, Heat Treatment, and Preset Pressure on Mechanical Properties of Ultra-High-Strength Mortars

In this study, efforts were undertaken to produce ultra-high-strength mortars (UHSM) from conventionally available materials. Selection of mixtures and optimization of mixtures were achieved by adopting the basic principles of UHSM and through trial studies. A preliminary investigation was carried out to assess the effects of different curing regimes on the strength development of UHSM. Effects of fiber addition, heat treatment, and preset pressure on the rate of strength development of UHSM mixtures were individually assessed to better understand their benefits in the production of UHSM. Mechanical properties of the heat-treated UHSM were then investigated to determine the performance of the UHSM developed from conventional materials. Results from this study suggested that for the production of UHSM, a multiple curing regime was best suited and was then used for further studies. Data on strength development indicated that heat treatment increased the strengths by 57% to 75%. With application of preset pressure, the compressive strengths of UHSM were increased significantly by 15% to 18%. The optimum quantity of fibers to produce UHSM was found to be 2% to 3%. Effectiveness of fibers in increasing the strength of UHSM was found to be higher for heat-cured specimens than for normal water-cured specimens. The maximum target strengths obtained from the UHSM were 194 MPa, 24 MPa, and 31 MPa for compression, split tension, and flexure, respectively. The UHSM also showed improved energy absorption and toughness characteristics, especially at higher-fiber dosages.

Load–deflection performance of partially prestressed concrete T-beams with steel fibres in partial and full depth

A total of twelve partially prestressed concrete T-beams were cast without and with fibres in partial and full depth. These beams were tested to assess the effect of fibre addition in different zones in the cross-section, namely, flange, web or the entire cross-section, on the load–deflection performance of the flexure critical beam specimens. An attempt has been made to predict the load–deflection characteristics of the beam specimens utilising the tension softening effects in the stress–strain behaviour of fibre-reinforced concrete. The proposed model accounts for the interaction of the matrix with the fibre pull-out mechanism. The details of the constitutive material properties used and the proposed layer-based analysis are presented in this paper. Comparisons with test data show good agreement.

Effect of fiber addition on mechanical and tribological properties of a copper/phenolic-based friction material

The purpose of the present work is to compare the effects of addition of different fibers on the mechanical and tribological properties of a copper/phenolic resin-based semi-metallic friction material using the same fiber contents and process conditions. The results indicate that cracks/voids are observed more or less in all post-cured materials. Compared to fiber-free material, materials containing copper and brass fibers have higher compressive strengths, while materials containing cellulose and carbon fibers have lower strengths. After post-curing all materials increase in thickness and decrease in weight and density. Cellulose fiber-added material has the greatest increase in thickness and decrease in density. Except cellulose, all fiber-added materials exhibit higher average COF values than that without fibers. Significant fade occurs to materials containing steel, brass, cellulose and ceramic fibers. Steel fiber-added material has the largest wear, while copper fiber-added material has the smallest wear. A loosely bonded layer of wear debris almost fully covers the worn surfaces of fiber-free as well as brass, cellulose and ceramic fiber-added materials. The debris layer partially covers the surfaces of copper and carbon fiber-added materials, and is substantially absent from the surface of that containing steel fiber. Among all fibers copper fiber appears to be the best candidate due to its relatively high and stable COF as well as low wear.

Effect of Fiber Additives on the Turbulent Jets

Effect of Fiber Additives on the Turbulent Jets

The effect of kevlar fiber reinforcement on the curing, thermal, and dynamic‐mechanical properties of an epoxy/anhydride system

AbstractCuring, thermal, and dynamic‐mechanical relaxational behavior of an epoxy/‐anhydride resin and a Kevlar‐fiber/epoxy composite were compared. Reinforcement by Kevlar fibers had a catalytic effect on the curing reaction. Reinforced formulations produced higher extents of reaction than neat formulations at the same curing time. Curing kinetics was also studied by means of DSC heating scans. When the Kevlar content increased, the heat flow curves and the exothermic peak temperature shifted significantly to lower temperatures. The glass transition temperature of the matrix also decreased as the Kevlar content increased. Postcuring reduced the differences between the neat and reinforced formulations. Loss tangent and storage modulus versus frequency master curves were obtained from isothermal dynamic‐mechanical measurements. The effect of fiber addition on the main dynamic‐mechanical relaxation was analyzed with a simple mechanical model.

Effects of preferential encapsulation of glass fiber on the properties of ternary GF/PA/PP blends

AbstractLong fiber molding materials are expected to play an important role in the near future. This paper describes a series of experiments performed to examine properties of ternary blends containing glass fiber (GF), polyamide (PA), and polypropylene (PP). The continuous glass fiber was impregnated with one of the blend constituent polymers by our specially designed impregnation apparatus and cut into chips of 6 mm length. These chips and the other polymer were used to produce various testing specimens in a twin screw extruder or in injection molding machine. The results indicated that the effect of fiber addition on the mechanical and rheological properties is clearly dependent on the order of impregnation process. In the blends containing the GF/PA + PP, the GFs are preferentially encapsulated with PA, and therefore the mechanical properties are superior to the blends with the GF/PP + PA in which the PP phase is located surrounding the GFs. This improved wetting of fibers by sequential impregnation not only resulted in better properties but also protected the fibers from shear action of the screw, thereby allowing significant increase in average fiber length to be achieved in the injection molding process.

Numerical solution of fiber suspension flow through a complex channel

Both numerical simulations and fiber orientation observations were carried out to investigate two-dimensional fiber orientations in a Newtonian flow through a 1:4 backward-facing step channel. Furthermore, the flows of suspensions with high aspect-ratio fibers in a Newtonian solvent through a 1:4 backward-facing step channel were computed rigorously by coupling the flow field with fiber orientation. In the numerical simulations, a statistical scheme (number of fibers N=1800) was used. In a recirculating flow, all fibers completely align along the streamlines for large aspect-ratio fibers ( r a=10 000), while complete alignment can be achieved, however, the preferred angle lies obliquely to the streamlines for small aspect-ratio fibers ( r a=5). On the other hand, in a main flow, the preferred angle lies obliquely to the streamlines in the central region of the channel, and furthermore, the fibers are less oriented and their preferred angles tilt away largely from the streamlines as the Reynolds number (Re) decreases. In the computations of flows of suspensions with high aspect-ratio fibers, co-linear alignment of fibers was used in a recirculating flow, while a complete alignment condition was adopted in a main flow. The relation between the fiber parameter φμ/ η and vortex length L v* follows a linear trend and its gradient decreases as Re increases, i.e. when inertia dominates the flow, the effect of fiber additives on flow structure becomes insignificant in an expansion flow. In an expansion flow of fiber suspensions for the complete alignment case, the worst orientation of fibers can be predicted clearly as a band-like pattern both near the vortex boundary and in the upper region of the expanding part. It can be supposed that fluid anisotropy near the vortex boundary is a key factor for the vortex enhancement in a complex flow.

A Study of the Interphase Region in Carbon Fibre/Epoxy Composites using Dynamic Mechanical Thermal Analysis

Abstract We have examined the effect of fibre addition on the glass transition temperature (T g ) of two epoxy resin systems (an amine cured and an anhydride cured epoxy system) using dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC). The presence of fibres changes the glass transition temperature (T g ) of an anhydride cured epoxy resin but does not affect that of an amine cured epoxy. The data suggest that two counteracting mechanisms are responsible for these changes: firstly, the presence of fibres causes a restriction of the molecular motion in the resin system, and secondly, the presence of carboxyi and keto-enol groups on the fibre surface inhibit curing of the resin close to the fibre, i.e. in the interphase region. The former increases the T g and is a long range effect whereas the latter decreases the T g and is a localised phenomenon. Changes in the dynamic properties of the interphase region are only detected when the samples are loaded in the longitudinal ...