Effects Of Fiber Characteristics Research Articles

Effect of Fiber Characteristics on the Structure and Properties of Quartz Fiber Felt Reinforced Silica-Polybenzoxazine Aerogel Composites.

Fiber-reinforced aerogel composites are widely used for thermal protection. The properties of the fibers play a critical role in determining the structure and properties of the final aerogel composite. However, the effects of the fiber's characteristics on the structure and properties of the aerogel composite have rarely been studied. Herein, we prepared quartz fiber felt-reinforced silica-polybenzoxazine aerogel composite (QF/PBSAs) with different fiber diameters using a simple copolymerization process with the ambient pressure drying method. The reasons for the effects of fiber diameter on the structure and properties of the aerogel composites were investigated. The results showed that the pore structure of the aerogel composites was affected by the fiber diameter, which led to significant changes in the mechanical behavior and thermal insulation performance. At room temperature, pore structure and density were found to be the main factors influencing the thermal conductivity of the composites. At elevated temperatures, the radiative thermal conductivity (λr) plays a dominant role, and reducing the fiber diameter suppressed λr, thus decreasing the thermal conductivity. When the QF/PBSAs were exposed to a 1200 °C butane flame, the PBS aerogel was pyrolyzed, and the pyrolysis gas carried away a large amount of heat and formed a thermal barrier in the interfacial layer, at which time λr and the pyrolysis of the PBS aerogel jointly determined the backside temperature of the composites. The results of this study can provide valuable guidance for the application of polybenzoxazine aerogel composites in the field of thermal protection.

Effects of fiber characteristics and specimen sizes on static and dynamic split-tensile failures of BFLAC: 3D mesoscopic simulations

In this study, a three-dimensional mesoscopic numerical model considering concrete heterogeneity and explicit modelling of basalt fibers was established to simulate the static and dynamic split-tensile failures of basalt fiber-reinforced lightweight aggregate concrete (BFLAC), with a special focus on the influences of structure sizes (D = 100, 200, 300 and 400 mm), basalt fiber contents (Vf = 0.1 %, 0.2 % and 0.3 %), fiber lengths (Lf = 6, 12, 18, 24 mm) and loading strain rates (ε̇ = 10-5/s ∼ 100/s) on split-tensile failure patterns, deformation characteristic and failure strengths. Simulation results indicate that as the fiber length increases, split-tensile strength of BFLAC enhances first and then remains unchanged. As the fiber content increases, both static and dynamic split-tensile strengths enhance, showing a fiber reinforcement effect which increases with the rising strain rate rise and reaches a threshold when the strain rate exceeds 1/s. Under static and low strain rates, the size effect on split-tensile strength of BFLAC is reduced by the addition of basalt fiber content; while there is a reverse size effect under high strain rates and it is strengthened with the increasing fiber content. Besides, the strain rate effect of BFLAC is stronger with the increasing basalt fiber content. A unified TDIF formula of BFLAC considering the influence of basalt fiber content was proposed, which can provide a valuable reference for the dynamic performance simulations and calculations.

A numerical study on the spatial orientation of aligning fibrous particles in composites considering the wall effect

Abstract The reinforced efficiency of steel fibers in composites is closely related to their spatial orientation, which can be generally driven by the external magnetic force and restricted by the wall effect of rigid boundaries of the container. To clarify the spatial orientation of steel fibers in composites considering the effect of rigid boundaries under the electromagnetic field, a series of two-phase models consisting of fibrous particles and homogeneous matrix are generated, in which the fibers are separately simplified as spherocylindrical, cylindrical, and linear particles. Based on these models of the semi-periodic boundaries, the effect of fiber characteristics (e.g., the fiber content V f, fiber aspect ratio ε, fiber length l sf, and fiber style) on both the spatial distribution and orientation degree of fibrous particles is studied before and after the fibers are aligned by the magnetic force. The results revealed that (1) both the effective number N A and orientation degree ξ of fibrous particles at a cross-section of the container can be greatly increased when the electromagnetic field is applied and (2) the wall effect of rigid boundaries shows an adverse impact on the amelioration of N A and ξ, and the range size of the affected region is essentially equal to the effective length of fibrous particles of different shapes (e.g., l sf + D sf) for spherocylindrical particles and l sf for cylindrical and linear particles).

Biobased PLA/sugarcane bagasse fiber composites: Effect of fiber characteristics and interfacial adhesion on properties

PLA/sugarcane bagasse fiber composites were prepared by injection molding from two fractions of fibers with different fiber characteristics, which were determined before and after processing. Interfacial adhesion was modified by a maleated PLA coupling agent. The mechanical properties of the composites were characterized by tensile and impact testing, while local deformation processes by acoustic emission testing and microscopy. The results showed that considerable attrition takes place during melt processing in both the length and diameter of the fibers. The originally different batches of short and long fibers have similar dimensions after processing. Interfacial adhesion between PLA and bagasse is inherently good, thus coupling does not improve properties. Shear yielding and fiber fracture consume sufficiently energy to increase the impact resistance. Sugarcane bagasse fibers considerably increase the stiffness of PLA, result in almost constant tensile strength and increase impact resistance yielding a material with reasonable combination of properties for structural applications.

Effect of fiber characteristics on fresh properties of fiber-reinforced concrete with adapted rheology

The influence of fiber type and volume on fresh properties of fiber-reinforced self-consolidating concrete (FR-SCC) and fiber-reinforced super-workable concrete (FR-SWC) was investigated. These mixtures were developed for infrastructure construction and repair, respectively, and the fibers were incorporated to reduce cracking and enhance service life of concrete structures. The fibrous mixtures were proportioned with a Type-G expansive agent (EA) to reduce shrinkage and mitigate the risk of cracking. The selected fibers included a propylene synthetic fiber, five different steel fibers, and a hybrid fiber containing steel and polypropylene multifilament fibers. The fiber volume was fixed at 0.5% for the FR-SCC mixtures and varied between 0.5% and 0.75% for the FR-SWC. The investigated FR-SCC and FR-SWC mixtures had initial slump flow of 660–700 mm and 505–570 mm, respectively, and exhibited excellent passing ability and adequate stability. The investigated FR-SCC and FR-SWC mixtures with passing ability index greater than or equal to 12 and 11, respectively, evaluated using the modified J-Ring test exhibited good flowability without blockage and segregation. The passing ability index was inversely proportional to plastic viscosity for mixtures of a given coarse aggregate content and maximum nominal size of aggregate. Good relationships between slump flow and yield stress and T50 and plastic viscosity were established for the fibrous mixtures.

Highly coherent visible dispersive wave radiation in suspended core fibers

Visible dispersive wave (DW) generation is used in several applications, such as in dispersion measurements, fluorescence microscopy, and biomedicine. The effects of fiber characteristics, pump pulse width, and average pump power on DW generation are investigated in suspended core fiber (SCF) by numerical simulation. The coherence of visible DW is high in all cases. The dynamics behind DW generation are analyzed based on pulse evolution spectrograms. Energy exchange between DW and soliton occurs mainly in the first contraction of the first emitted soliton. Numerical simulations using experimental parameters indicate that the DW can be compressed down to approximately 40 fs. In experiments, under the pump pulse with a pulse width of 50 fs and pump wavelength of 1 μm, an isolated DW is generated at ∼480 nm in SCF1 featuring a large fiber core. Under the same pump conditions, isolated DWs at ∼466 nm and ∼485 nm with full width at half maximum of ∼40 nm and conversion efficiency of ∼10% are achieved in SCF2 with a small fiber core. The coherence of DW is better than that of the infrared component based on the comparisons of the pulse trains of DW and the infrared component in supercontinuum. The influence of OH− content on DW generation is also experimentally analyzed.

The interaction of delignification and fiber characteristics on the mechanical properties of old corrugated container fiber/polypropylene composite

AbstractThe effect of fiber characteristics from old corrugated container (OCC) paper on the strength properties of OCC/polypropylene composites was evaluated. Fibers with different contents of lignin (2.8%, 3.8%, 5.3%, and 7%) were produced using soda pulping. Wettability, tear, and tensile strength of the fibers were measured as the indication factors to assess the strength of reinforcing component in the composites. The weight portions of the OCC fibers, polypropylene, and maleic anhydride-grafted polypropylene (MAPP) were selected at 20%, 77%, and 3% of the total weight of the composite, respectively. The composite compounds were formed using a counter-rotating twin screw extruder, and the specimens were made in an injection molding machine. The interaction of fiber characteristics and fiber lignin content on the mechanical properties of composite was investigated. The results revealed that with lower fiber lignin content, both flexural and tensile properties were increased. Consequently, by forming better fiber dispersion and by reducing stress regions in the composite, impact strength was also improved. Lower lignin content resulted in better mechanical properties than fiber characteristics.

Yield stress of pretreated corn stover suspensions using magnetic resonance imaging

Cellulose fibers in water form networks that give rise to an apparent yield stress, especially at high solids contents. Measuring the yield stress and correlating it with fiber concentration is important for the biomass and pulp industries. Understanding how the yield stress behaves at high solids concentrations is critical to optimize enzymatic hydrolysis of biomass in the production of biofuels. Rheological studies on pretreated corn stover and various pulp fibers have shown that yield stress values correlate with fiber mass concentration through a power-law relationship. We use magnetic resonance imaging (MRI) as an in-line rheometer to measure velocity profiles during pipe flow. If coupled with pressure drop measurements, these allow yield stress values to be determined. We compare our results with literature values and discuss the accuracy and precision of the rheo-MRI measurement, along with the effects of fiber characteristics on the power-law coefficients.

Effect of Fiber Characteristics on the Desorption Rate of Water from Cloth

<b>Effect of Fiber Characteristics on the Desorption Rate of Water from Cloth </b>

Effects of fiber characteristics on the mechanical and rheological properties of poly(butylene terephthalate)/glass fiber composites

AbstractMorphological, mechanical, and rheological properties of poly(butylene terephthalate) (PBT)/glass fiber (GF) composites and their fiber lengths after extrusion were studied, along with the molecular weight of PBT and the sizing effect of the fiber. From the molecular weight effect of PBT on mechanical properties, the lower molecular weight PBT composites prepared showed higher flexural and tensile strengths compared to the PBT/GF composites prepared with a higher molecular weight PBT when the fiber content was over 20 wt %. This behavior was mainly due to the increased fiber length of the PBT/GF composite prepared with lower molecular weight PBT. For the PBT composites with GF coated with organic materials having polarity similar to that of the PBT matrix, better mechanical properties were observed due to higher bonding forces between the matrix and fibers. Due to the effect of fiber length on the complex viscosity of the PBT/GF composite and its resulting high elasticity, the shear thinning behavior was more significant for the composites containing long fibers than in composites containing short fibers. From the above results, it is suggested that the optimum mechanical properties of the fiber‐reinforced polymer composite can be achieved by varying the processing conditions such as molecular weight of the matrix polymer, surface treatment of the fiber, and feeder location of the fiber. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effects of fiber characteristics on the physical and mechanical properties of wood plastic composites

We investigated the effects of fiber variability, size, and content on selected mechanical and physical properties of wood plastic composites. HDPE and fibers were compounded into pellets by twin-screw extrusion and test specimens were prepared by injection molding. All tested properties vary significantly with fiber origin. Higher fiber size produces higher strength and elasticity but lower energy to break and elongation. The effect of fiber size on water uptake is minimal. Increasing fiber load improves the strength and stiffness of the composite but decreases elongation and energy to break. Water uptake increases with increasing fiber content.

Experimental and numerical analysis of fiber characteristics effects on fiber dispersion for wet-laid nonwoven

Dispersion and separation of fiber bundles into individual fibers, requires exposing them to a shear stress field to overcome inter-fiber frictional forces. To this end, fiber-mixing tanks are usually used to enhance shear and agitation in water and help the dispersion process. The required time and necessary agitation to separate and disperse fibers depend on fibers’ characteristics. It is well known that excessive agitation will give rise to the formation of rope defects in the output because of the high-energy vortices and optimizing the break up time is important in wet-lay process. In this work, experimental and numerical studies were done to investigate the effects of fiber characteristics on their dispersion in water for wet-laid nonwoven. The effective forces were analyzed using a one-way modeling of fiber behaviors in a stirred mixing tank. Results show that when the fiber diameter is increased, the required time for breaking up of fiber bundles and clumps is increased. The effects of fiber types on fibers break up and dispersing time, were also investigated. In the experimental work, an on-line vision system was designed to observe the dispersion behavior of polyester fibers. The effects of fiber length and fineness on the created defects (i.e. logs and ropes) in dispersion process, as well as on the dispersion speed, were studied. The results confirm that defects are increased by rising fiber length and fineness. It is also shown that increasing fiber length and fineness, decreases the required time for fiber clumps to be opened and reach a maximum number of individual fibers. On the other hand, when fiber length and fineness is increased, the dispersion speed increases.

Effects of Fiber Characteristics on the Rheological and Mechanical Properties of Polycarbonate/Carbon Fiber Composites

Rheological and mechanical properties of the polycarbonate (PC)/carbon fiber (CF) composites with different initial fiber length, sizing effect of the fiber, fiber content and screw speed have been studied. PC/CF composites were prepared by twin screw extruder. In the studies of sizing effect of the fiber on the rheological properties of the PC/CF composites, the viscosities of the composites prepared with the sized carbon fibers gave higher values than that prepared with unsized carbon fibers because of the increase in the fiber length after extrusion for the sized fibers. From the results of the effect of screw speed on the rheological and mechanical properties of PC/CF composites, we found that the viscosity and tensile strength decreased with increasing screw speed. This is mainly due to that the fact that the fiber length after extrusion has been decreased from 163 to 148 μm with the increase of the screw speed from 100 to 200 rpm when the fiber content used in the composites is equal. From the above results, it is suggested that the fiber length after extrusion of the PC/CF composites has a strong effect on the rheological and mechanical properties of the composites. Also, a relationship among the initial fiber length, sizing effect of the fiber, fiber content and screw speed has been studied comprehensively for the PC/CF composites.

Thermal energy transport within porous polymer materials: Effects of fiber characteristics

AbstractA theoretical model integrating the radiative and conductive heat transfer is presented and applied to evaluate the thermal energy transport within porous polymer materials. The model was first validated by comparing the computed thermal energy flux with the experimental measurements of two porous polymer materials made of wool and polyester. The model was then used to predict the effects of the polymer fiber characteristics (viz. fiber fractional volume, fiber emissivity, fiber radius, and fiber thermal conductivity) on the thermal energy flux within the porous polymer materials. It was found that decreasing fiber radius would significantly reduce the total thermal energy flux through the porous polymer materials, whereas increasing fibre emissivity or decreasing the thermal conductivity would cause a just slight reduction of the total thermal energy flux. The fiber fractional volume had a significant influence on the thermal energy flux, and thereby the fiber fractional volume can be optimized in view of improving the thermal insulating performance of the porous polymer materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Water Accessibilities of Man-made Cellulosic Fibers – Effects of Fiber Characteristics

The dynamic vapor water sorption and desorption experiments were performed on cellulosic fibers with different characteristics. The hysteresis between moisture sorption and desorption cycle at 10% relative humidity (RH) was independent on the total moisture regain and approximately 45% for all materials except for viscose fibers. Brunauer–Emmett–Teller surface volume (Vm) for moisture sorption and retention capacity of liquid water (WRV) were also measured. The Vm and WRV increase in proportion to the total amount of moisture sorption (Minf(total)) in all specimen except in poplar fiber. The coefficients of parallel exponential kinetics (PEK) were estimated by the curve-fitting of experimental data of the moisture regain, and the influences of the fiber characteristics on the PEK coefficients, the moisture regain, the hysteresis, Vm and WRV are discussed. The total equilibrium moisture content in the viscose fibers was higher but the moisture uptake and release rate was slower than the lyocell and poplar fibers. The cationization and the modification of shape of cross section accelerated the total equilibrium moisture content in the viscose fiber. A drying process at low temperature enhanced both the equilibrium moisture content and the moisture uptake and release rate in lyocell fibers while a spin finish retarded them. The total equilibrium moisture content was heightened by the crosslinking of the fiber, however, no obvious effect of the crosslinking on the moisture uptake and release rate was found. Effects of the type of the specimen and linear density on the moisture accessibilities are also discussed.

The effect of fiber characteristics on thermoregulatory responses and feeding behavior of heat stressed cows

We examined the effect of replacing wheat hay with soy hulls on thermoregulatory responses and feeding behavior under summer condition in dairy cows. Milk yield, feed intake, meal size, and number, heart rate and heat production were similar in the two dietary groups. Visit duration and time spent eating were shorter, and body temperature was higher in the soy hulls fed cows. It was concluded that supplying soy hulls can enable cows subjected to heat load conditions to reduce the costs of feed ingestion. However, the contribution of this tool to the overall energy budget is rather small.

Monte Carlo simulation of the effect of fiber characteristics on creep life of a fiber tow

Fatigue of reinforced ceramics at elevated temperatures was numerically evaluated with a fiber dominated, power-law creep model. A Monte Carlo simulation of fiber creep in a uniaxially loaded tow was used to examine the influence of fiber radius, elastic modulus, and strength on creep respose. The simulation permitted variation of both the average magnitude and dispersion of fiber characteristics while maintaining constant power-law creep parameters. A linear increase in creep life was predicted for an increase in mean fiber radius, and a linear decrease in creep life was predicted for an increase in the standard deviation of fiber radii. A linear increase in creep life was predicted for both an increase in mean fiber elastic modulus and standard deviation of elastic moduli. Characteristic fiber strength and Weibull modulus were predicted to have a significant effect on creep life of a SiC fiber low. An increase in either the characteristic strength or Weibull modulus was predicted to result in an increase in creep life.

The effect of fiber characteristics on hydrolysis and cellulase accessibility to softwood substrates

The effect of gross fiber characteristics on enzyme accessibility and hydrolysis of Douglas fir kraft pulp substrates was investigated. The average fiber size and coarseness of the substrate had a significant effect on the enzyme adsorption capacity. This was primarily due to the increased specific surface area of small fibers and fines. The observed adsorption capacities were in agreement with the hydrolysis rates and yields because the substrates with the lower average fiber size were hydrolyzed both at a faster rate and more completely. The observed changes in fiber-length distribution and fiber coarseness suggested that the effect of fiber size was most influential during the initial stages of hydrolysis. The small fibers and fines present in heterogeneous, lignocellulosic substrates were hydrolyzed rapidly, yielding a high initial rate of hydrolysis.

Effects of fiber characteristics on lung deposition, retention, and disease.

There is abundant epidemiologic evidence that asbestos fibers can cause lung fibrosis (asbestosis), bronchial cancer, and mesothelioma in humans, as well as limited evidence for such effects in workers exposed to slag and rockwool fibers. Epidemiological evidence for human disease from inhalation exposures to conventional fibrous glass is negative. While health concerns based on the morphological and toxicological similarities between man-made fibers and asbestos are warranted, it is important to note that most of the toxicological evidence for glass fiber toxicity in laboratory animals is based on nonphysiological exposures such as intratracheal instillation or intraperitoneal injection of fiber suspensions. Man-made fibers have produced lung fibrosis and mesotheliomas in such tests, albeit at much lower yields than asbestos. For all durable mineral fibers, critical length limits must be exceeded to warrant concern about chronic toxicity; i.e., 2 microns for asbestosis, 5 microns for mesothelioma, and 10 microns for lung cancer. Fiber width must be less than 0.1 microns for mesothelioma, and larger than this limit for asbestosis and lung cancer. The human health risks for most fibrous glass products are either low or negligible for a variety of reasons. First, most commercial fibrous glass products have mean fiber diameters of approximately 7.5 microns, which results in mean aero-dynamic diameters approximately 22 microns. Thus, most glass fibers, even if dispersed into the air, do not penetrate into the lung to any great extent. Second, the small fraction of smaller diameter fibers that do penetrate into the lungs are not persistent within the lungs for most fibrous glass products due to mechanical breakage into shorter lengths and overall dissolution.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Fiber Characteristics on Lung Deposition, Retention, and Disease

There is abundant epidemiologic evidence that asbestos fibers can cause lung fibrosis (asbestosis), bronchial cancer, and mesothelioma in humans, as well as limited evidence for such effects in workers exposed to slag and rockwool fibers. Epidemiological evidence for human disease from inhalation exposures to conventional fibrous glass is negative. While health concerns based on the morphological and toxicological similarities between man-made fibers and asbestos are warranted, it is important to note that most of the toxicological evidence for glass fiber toxicity in laboratory animals is based on nonphysiological exposures such as intratracheal instillation or intraperitoneal injection of fiber suspensions. Man-made fibers have produced lung fibrosis and mesotheliomas in such tests, albeit at much lower yields than asbestos. For all durable mineral fibers, critical length limits must be exceeded to warrant concern about chronic toxicity; i.e., 2 microns for asbestosis, 5 microns for mesothelioma, and 10 microns for lung cancer. Fiber width must be less than 0.1 microns for mesothelioma, and larger than this limit for asbestosis and lung cancer. The human health risks for most fibrous glass products are either low or negligible for a variety of reasons. First, most commercial fibrous glass products have mean fiber diameters of approximately 7.5 microns, which results in mean aero-dynamic diameters approximately 22 microns. Thus, most glass fibers, even if dispersed into the air, do not penetrate into the lung to any great extent. Second, the small fraction of smaller diameter fibers that do penetrate into the lungs are not persistent within the lungs for most fibrous glass products due to mechanical breakage into shorter lengths and overall dissolution.(ABSTRACT TRUNCATED AT 250 WORDS)