Increasing Fiber Length Research Articles

An investigation on minimum ignition energy (MIE) and thermodynamic analysis of typical fibrous dust

This study focused on several natural fibrous dust (cotton, silk, and linen fibers) and synthetic fibrous dust (polyester and nylon fibers) obtained from textile mills. Potential relationships between minimum ignition energy (MIE) values and equivalent diameters calculated via four phenomenological models were explored to explain the dependence of the MIE values on geometry. Diameter and material composition are the most critical factors influencing MIE of fibrous dust. However, the impact of length on MIE involving a fixed-diameter fiber cannot be ignored. To explain higher MIE values with increased fiber length per given diameter, an axial heat transfer mechanism model of fibrous dust was constructed in terms of energy conservation. In addition, the pyrolysis processes, pyrolysis mechanisms, and thermodynamic parameters (i.e., activation energy (E), pre-factor (A), and enthalpy(ΔH)) of typical fibrous dust were analyzed to provide a theoretical basis for the numerical simulation of this dust type.

Novel method of mechanical alignment for chopped carbon fiber/high density polyethylene composites: Processing, modeling, and characterization

In this study, we investigated a novel method of mechanical alignment to enhance the tensile properties of chopped carbon fiber (CCF)/high-density polyethylene (HDPE) composites. By utilizing a novel extruder and take-up system based on the melt spinning technique, we successfully controlled the alignment of CCF at various thicknesses using mechanical tension. This facilitated the production of extruded profiles with controlled tensile conditions. Experimental measurements were conducted to evaluate the tensile strength and modulus of the composites. The results demonstrate the effectiveness of the proposed CCF alignment method, which involves adjusting the thickness of the extruded profiles, in controlling the mechanical properties of the composites. As a result, the ultimate tensile strength increased by 50%, and the tensile modulus increased by 130%. Additionally, we developed a numerical model that predicts the tensile modulus based on randomly generated fibers and the Mori-Tanaka model for property estimation. The fiber orientation distribution was influenced by the fiber shape and manufacturing conditions. Scanning electron microscope (SEM) images revealed that the fibers aligned more along the extrusion direction with increased draw ratio. The orientation distribution of the randomly generated fibers varied significantly based on the fiber length and draw ratio, indicating a narrowed distribution range along the extrusion direction with increased fiber length or draw ratio. These findings demonstrate that the proposed CCF alignment method, which involves changing the thickness of the extruded profiles, can effectively control the mechanical properties of the composite.

Shear Strength Behaviors of Aeolian Sand Solidified by Microbially Induced Calcite Precipitation and Basalt Fiber Reinforcement.

Aeolian sand flow is identified as the main factor in the formation of sandstorms. However, conventional sand fixation methods cannot meet the current development requirements of environmental protection. In this paper, the method using Microbially Induced Calcite Precipitation (MICP) combined with basalt fiber reinforcement (BFR) was adopted to solidify the aeolian sand. Consolidated undrained triaxial shear tests were carried out to analyze the influence of fiber content, fiber length, confining pressure, and other factors on stress-strain characteristics, peak strength, brittleness index, and shear strength of aeolian sand. A shear strength model of aeolian sand solidification using MICP-BFR and considering the effect of fiber length and fiber content is established according to the test results. The results show that the peak strength of aeolian sand solidified by MICP-BFR is remarkably higher than that of aeolian sand solidified by MICP alone, and the peak strength rises with the increasing fiber length, fiber content, and confining pressure. The application of fiber can effectively reduce the brittleness index of aeolian sand solidified by MICP and improve the sample ductility. As fiber content and fiber length increase, the cohesion of solidified aeolian sand increases while the internal friction angle changes relatively little. In the limited range set by the test, the fiber length of 12 mm and the fiber content of 1.0% constitute the optimum reinforcement condition. The test results coincide with the model prediction results, indicating that the new model is fitting for predicting the shear strength of aeolian sand solidified by MICP-BFR. The research results provide an important reference value for guiding the practice of wind prevention and sand fixation in desert areas.

Hollow fiber membrane integrated water cooler: A novel liquid cooling solution

To address the issues of water–air cross-contamination, liquid droplet carryover, and high maintenance costs of traditional water-mediated evaporative cooling systems, the hollow fiber membrane integrated water cooler (MWC) is proposed as a novel liquid cooling solution. The MWC incorporates hydrophobic porous membranes that enable water vapor migration while avoiding direct contact between liquid water and air. In addition, the MWC offers advantages over conventional evaporative cooling paddings in terms of high specific surface area, corrosion resistance, and anti-scaling. To evaluate the cooling performance of a countercurrent MWC, an experimental bench was built to test its outlet water temperature under various operating conditions. The developed numerical model was verified with the measured data. Then, the influence of nine critical parameters, including operating conditions and membrane module specifications, on the outlet water temperature and cooling efficiency of the countercurrent MWC was numerically investigated. The results show that evaporative heat dissipation contributes to more than 80% of the total heat exchange in MWC. Cold and dry ambient air, high inlet water temperature, low water velocity, and high air/water ratio contribute to superior cooling capability. Moreover, the cooling performance of MWC improves with increasing fiber length, inner diameter, packing fraction, and decreasing membrane thickness. In addition, the MWC offers a cooling capacity per unit volume of up to 1094.72 kW/m3, an order of magnitude greater than conventional wet cooling towers. Overall, this work presents theoretical guidelines for optimizing the operating conditions and configuration of countercurrent MWCs.

Rheological behavior of basalt fiber sprayed cementitious composites (BFSCC)

In the application of modern sprayed cementitious composites, more specific requirements have been proposed for crack resistance, toughness, and durability. By adding fibers with high strength and toughness to the cementitious matrix, the resulting composite material can exhibit excellent mechanical properties. Currently, the commonly used fiber materials of sprayed cementitious composites include steel fiber, polypropylene fiber, basalt fiber. As a type of green and sustainable building material, basalt fiber has been widely used in various engineering projects. In the field of sprayed cementitious composites (SCC), the addition of chopped basalt fibers can enhance its toughness and cracking resistance. However, fiber inclusion may also lead to reduced workability and equipment clogging. Therefore, the rheological behavior of basalt fiber sprayed cementitious composites (BFSCC) under mixing and spraying stages of construction become critical and essential to be fully investigated. In order to simulate the actual engineering application environment of BFSCC, a mortar spraying machine and ICAR rheometer were used to evaluate the variation of key rheological parameters under mixing and spraying stages of construction. The yield stress, plastic viscosity, and thixotropic indices of BFSCC under the influences of basalt fiber characteristics, i.e., type, content and hybrid length, were investigated. The time-dependent rheological behavior of BFSCC was also evaluated. The results indicated that there were significant differences on rheological behaviors under mixing and spraying stages of construction when the basalt fiber was introduced. The spraying process yielded a much higher static and dynamic yield stresses of BFSCC compared with those of mixing stage. Under the same fiber volume content, the plastic viscosity of BFSCC increased first and then decreased with an increase in fiber length in both stages, reaching a maximum at 12 mm. The time-dependent changes in the thixotropic index decreased first and then increased with an increase in time in both the mixing and spraying stages. A prediction model on rheological parameters for BFSCC under mixing and spraying stages was established in accordance with fiber characteristics.

Fracture spacings of fiber inclusions in a ductile geological matrix and development of microboudins: 3D numerical modeling

Tensile fractures and resultant microboudinage structures of brittle fiber inclusions (e.g., tourmaline, piedmontite and amphibole) in the soft matrix of deforming minerals are of great significance for determining the finite strains and paleostresses of naturally deformed rocks. Using statistical strength theory, damage mechanics, and continuum mechanics, we have reproduced in a series of numerical models the sequential fractures of either homogeneous or heterogeneous fiber inclusions under axial tension in an elastoplastic matrix. The results clarify that: (1) The spacing between fractures in fibers is inversely proportional to the applied strain. As the applied strain increases, the fracture spacing systematically decreases as sequential fractures fill in until fracture saturation is reached. (2) As fiber length increases, the critical tensile strain for fracture saturation rises. For the same fiber diameter, saturation fracture spacing increases slightly with rising fiber length. For the same fiber length, however, saturation fracture spacing decreases significantly with lessening fiber diameter. Hence, fracture spacing at the saturation state depends on the volume fraction of fiber. (3) The rupture mode of fibers strongly depends on the non-uniform distribution of mechanical properties, which provides an effective approach for estimating the inhomogeneity of fibers by analyzing the formation of fractures. Furthermore, due to material heterogeneity, new fractures are unlikely to occur in the middle of existing adjacent fractures.

A cell wall-localized β-1,3-glucanase promotes fiber cell elongation and secondary cell wall deposition.

β-1,3-glucanase functions in plant physiological and developmental processes. However, how β-1,3-glucanase participates in cell wall development remains largely unknown. Here, we answered this question by examining the role of GhGLU18, a β-1,3-glucanase, in cotton (Gossypium hirsutum) fibers, in which the content of β-1,3-glucan changes dynamically from 10% of the cell wall mass at the onset of secondary wall deposition to <1% at maturation. GhGLU18 was specifically expressed in cotton fiber with higher expression in late fiber elongation and secondary cell wall (SCW) synthesis stages. GhGLU18 largely localized to the cell wall and was able to hydrolyze β-1,3-glucan in vitro. Overexpression of GhGLU18 promoted polysaccharide accumulation, cell wall reconstruction, and cellulose synthesis, which led to increased fiber length and strength with thicker cell walls and shorter pitch of the fiber helix. However, GhGLU18-suppressed cotton resulted in opposite phenotypes. Additionally, GhGLU18 was directly activated by GhFSN1 (fiber SCW-related NAC1), a NAC transcription factor reported previously as the master regulator in SCW formation during fiber development. Our results demonstrate that cell wall-localized GhGLU18 promotes fiber elongation and SCW thickening by degrading callose and enhancing polysaccharide metabolism and cell wall synthesis.

Strigolactones modulate cotton fiber elongation and secondary cell wall thickening

Cotton is one of the most important economic crops in the world, and it is a major source of fiber in the textile industry. Strigolactones (SLs) are a class of carotenoid-derived plant hormones involved in many processes of plant growth and development, although the functions of SL in fiber development remain largely unknown. Here, we found that the endogenous SLs were significantly higher in fibers at 20 days post-anthesis (DPA). Exogenous SLs significantly increased fiber length and cell wall thickness. Furthermore, we cloned three key SL biosynthetic genes, namely GhD27, GhMAX3, and GhMAX4, which were highly expressed in fibers, and subcellular localization analyses revealed that GhD27, GhMAX3, and GhMAX4 were localized in the chloroplast. The exogenous expression of GhD27, GhMAX3, and GhMAX4 complemented the physiological phenotypes of d27, max3, and max4 mutations in Arabidopsis, respectively. Knockdown of GhD27, GhMAX3, and GhMAX4 in cotton resulted in increased numbers of axillary buds and leaves, reduced fiber length, and significantly reduced fiber thickness. These findings revealed that SLs participate in plant growth, fiber elongation, and secondary cell wall formation in cotton. These results provide new and effective genetic resources for improving cotton fiber yield and plant architecture.

Test research on flexural strength of soil-cement reinforced with carbon fibers

In order to verify the feasibility of using chopped carbon fibers to reinforce soil-cement, the orthogonal test and verification test of flexural strength had been carried out and the correctness and effectiveness of the test results had been clarified. The test results indicated that the addition of carbon fibers could make the flexural strength of soil-cement improved effectively and change the brittle failure of soil-cement into plastic failure. The flexural strength of carbon fiber soil-cement (CFSC) could reach 0.509 MPa, that was 31.5 % higher than that (0.387 MPa) of the plain soil-cement in the standard condition. All the first extreme flexural strength (e.g. the flexural strength), yield strength, second extreme flexural strength and residual strength increased first and then decreased with the increase of either fiber content or fiber length. Thus, excessive fiber content and fiber length were not better and the optimum values were existent with 0.6 % and 15 mm respectively under the test conditions agreed in this study. The change magnitude of the yield strength, second extreme flexural strength and residual strength was much greater than that of the first extreme flexural strength. So the strengthening effect of the carbon fibers on soil-cement was better for its toughness and ductility than for its flexural strength. The order of soil type corresponding with the flexural strength of CFSC from high to low was clay, silty clay, mucky silty clay, silt and fine sand. The flexural strength of CFSC increased linearly with the increase of cement content and the economical cement content was obtained as 15 %. The flexural strength of CFSC increased quickly between the 3 d and 14 d, slowly between the 14 d and 28 d and very slowly after 28 d, but still was increasing. The interaction mechanism between carbon fibers and soil-cement had been analyzed from a macro and a micro perspective respectively. The modified multivariate nonlinear regression model was proposed. The results and conclusions above could provide reference and basis for the application and popularization of CFSC in actual engineering.

Mesoscale FE analysis of thermal conductivity of steel fiber-reinforced cementitious materials considering fiber-matrix interface and pore effects

The thermal conductivity (λ-value) of cementitious materials with steel fibers is not always better than that of plain cementitious materials due to the interface between the steel fiber and cementitious materials and the increased porosity. A mesoscale finite element (FE) model considering both fiber-matrix interface and pore effects was developed to quantify the influences of porosity, pore water saturation degree, fiber-matrix interface property, fiber content, fiber length, fiber shape, and fiber orientation on the λ-value of cementitious materials, which can explain well the various relationships between the λ-value of cementitious materials and steel fiber content reported in the literature. In the FE model, cementitious materials containing steel fibers were divided into two scales where Scale I included solid phase and pore, and Scale II was made up of the homogenous composites from Scale I and steel fibers. To achieve a more accurate representation of the pore structures, the pores at Scale I were created randomly without specifying their geometry. The fiber-matrix interface in cementitious materials at Scale II was modelled as a zero-thickness interface with constant interfacial thermal conductance. It is found that the λ-value of cementitious materials decreases linearly with increasing porosity but increases linearly with increasing pore water saturation degree. The influence of steel fiber on the λ-value of cementitious materials depends on the fiber-matrix interface property. When the fiber content or fiber length increases, the λ-value will increase for good fiber-matrix interfaces with high interfacial thermal conductance; while poor interfaces with low interfacial thermal conductance lead to an opposite trend. Fiber geometry has a limited impact on the λ-value. The fiber orientation can affect the λ-value of cementitious materials. When the fiber rotational angle with respect to the direction of temperature gradient increases, the λ-value of cementitious materials with the same fiber-matrix interface property will decrease.

Study on the Compressive Stress–Strain Curve and Performance of Low-Slump Polypropylene Fiber Concrete after High Temperature

This study aims to investigate the effect of high temperature on the mechanical properties of low-slump polypropylene fiber (PPF) concrete, and tests the tensile and compressive properties of 204 groups of low-slump PPF concrete with eight different dosages and four different lengths at normal temperature and after high temperature. The results of the compressive test showed that PPF can significantly improve the mechanical properties of concrete after high temperature when the fiber content is small, and the compressive strength of low collapse polypropylene fiber concrete after high temperature showed a tendency to rise and then fall at the same temperature with an increase of the fiber admixture. When the fiber content was 0.5 kg/m3, the compressive strengths of 3 mm, 9 mm, 15 mm and 19 mm reached their maxima, which were 9.65%, 11.33%, 7.90% and 2.87% higher than that of ordinary concrete, respectively. With an increase in fiber length, the effect of PPF on the compressive strength of concrete is not obvious. PPF at high admixture further increases the pore and air content in concrete, which decreases the compactness of the concrete, thus leading to a decrease in the compressive strength of the concrete. When the temperature was 800 °C and the fiber admixture was 5.0 kg/m3, the compressive strength of PPF concrete with different lengths reduced by 17.83%, 17.27%, 22.59% and 23.92%, respectively, compared to normal concrete. In addition, according to the results, the optimal combinations of strength at room temperature and after high temperature were 3 mm fiber length and 1.0 kg/m3 dosing and 9 mm fiber length and 0.5 kg/m3 dosing, respectively, which increased the compressive and tensile strengths by 17.15% and 25.72% at room temperature and by at least 6% and 20% after high temperature, compared to the concrete without fiber dosing. Moreover, the stress–strain constitutive equations of PPF concrete at normal temperature and after high temperature were established, which can be used for finite element simulation and related mechanical analysis of PPF after high temperature.

Toughening effect and mechanism of rice straw Fiber-reinforced lime soil

Lime-stabilized soil used for subgrade is prone to brittle damage under loading because of low toughness. Based on this phenomenon, the toughening effects of anticorrosive rice straw fibers on the lime-stabilized soil and its internal mechanism have been studied in this paper. Different fiber contents (0.2 wt%, 0.6 wt%, 1.0 wt%) and fiber lengths (0–10 mm, 10–20 mm, 20–30 mm) were studied. Three-point bending tests, unconfined compressive strength tests and triaxial compression tests were conducted on the rice straw fiber-reinforced lime soil. Energy absorption, deformation index, and brittleness index were evaluated under flexure, compression, and shear. The toughness change from energy, deformation, and strength was studied based on these. The toughening mechanism of fiber reinforcement was analyzed from the mechanism of fiber-soil interaction, the energy absorption threshold of the damage process, the damage pattern of specimens and the length of the crack propagation path. The results showed that with the increase in fiber content and fiber length, the energy absorption and deformation index of the damage process increased while the brittleness index decreased. The brittle damage pattern was improved, and the toughness increased. The fibers connect the soil particles on both sides of the fracture surface through the bridging effect, form a three-dimensional reinforcement network to restrict the soil particle movement and consume a lot of energy during the interaction with soil, which causes the increase in the energy absorption threshold of soil. Thus, the toughness of the lime-stabilized soil is improved.

The effect of neuromuscular electrical stimulation applied at different muscle lengths on muscle architecture and sarcomere morphology in rats.

Neuromuscular electrical stimulation (NMES) is often used to increase muscle strength and functionality. Muscle architecture is important for the skeletal muscle functionality. The aim of this study was to investigate the effects of NMES applied at different muscle lengths on skeletal muscle architecture. Twenty-four rats were randomly assigned to four groups (two NMES groups and two control groups). NMES was applied on the extensor digitorum longus muscle at long muscle length, which is the longest and stretched position of the muscle at 170° plantar flexion, and at medium muscle length, which is the length of the muscle at 90° plantar flexion. A control group was created for each NMES group. NMES was applied for 8 weeks, 10 min/day, 3 days/week. After 8 weeks, muscle samples were removed at the NMES intervention lengths and examined macroscopically, and microscopically using a transmission electron microscope and streo-microscope. Muscle damage, and architectural properties of the muscle including pennation angle, fibre length, muscle length, muscle mass, physiological cross-sectional area, fibre length/muscle length, sarcomere length, sarcomere number were then evaluated. There was an increase in fibre length and sarcomere number, and a decrease in pennation angle at both lengths. In the long muscle length group, muscle length was increased, but widespread muscle damage was observed. These results suggest that the intervention of NMES at long muscle length can increase the muscle length but also causes muscle damage. In addition, the greater longitudinal increase in muscle length may be a result of the continuous degeneration-regeneration cycle.

Performance analysis of spectrally shaped DDO-OFDM based on nonlinear differential coding and real-valued precoding

This paper presents a cost-effective spectrally shaped quadrature amplitude modulation (SS-QAM) signal in bandwidth limited direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems. The concatenation of the nonlinear differential coding (NLDC) and real-valued precoding sequentially implements spectral-shaping and multi-carrier modulation. Real-value discrete cosine transform (DCT) and discrete Hartley transform (DHT) are used to realize the uniform distribution of the fluctuation signal-to-noise ratio (SNR) and reduce the peak-to-average power ratio (PAPR). To broaden the flexibility of constellation mapping and improve the fine granularity of signals, six modulation formats are analyzed and evaluated in DDO-OFDM systems. Results show that SS-QAM is superior to uniformly distributed QAM in terms of reducing bit error rate (BER) and increasing normalized generalized mutual information (NGMI). Compared to the uniform 25/36/49/64/81/100 QAM OFDM signal, when the transmission distance is 20 km, SS-25/36/49 QAM signal can achieve error free transmission and SS-64/81/100 QAM can achieve 0.9971/1.0037/1.0255 Q-factor improvement and 0.0009/0.0014/0.0015 NGMI gain. When the transmission distance is 50 km, SS-25/36/49/64/81/100 QAM can achieve 0.4182/0.5169/0.9311/0.9988/1.0216/1.1487 Q-factor improvement and 0.0004/0.0008/0.0031/0.0043/0.0066/0.0083 NGMI gain. When the transmission distance is 80 km, SS-25/36/49/64/81/100 QAM can achieve 0.4754/0.7486/1.181/1.2012/1.2302/1.3904 Q-factor improvement and 0.0015/0.0046/0.0108/0.0152/0.0172/0.0205 NGMI gain. In addition, the Q-factor and NGMI gain increases as the fiber length increases, which verifies that the presented scheme is robust to the nonlinear effect.

The effect of different nitrogen doses and water levels on the yield and yield components of cotton

This study was conducted to determine the effect of irrigation levels and nitrogen doses on yield and some yield parameters of Stoneville 468 cotton (Gossypium hirsutum L.) cultivar produced in semi-arid climatic conditions in 2017 and 2018 crop growing seasons with 3 replications utilizing the split plot design with random blocks. Five fertilizer (nitrogen) doses (0, 100, 150, 200 and 250 kg ha−1) and 4 irrigation percentages (25, 50, 75% and 100% of the field capacity) were used as treatments. In the experiment, the main plots were nitrogen doses, and the sub-plots were amounts of irrigation levels. In the first year of the experiment, a total of 1258 mm irrigation water was applied to the 100% trial (I100) while 1332 mm irrigation of water was applied. The results of study indicated that water stress caused a linear relationship between applied irrigation water amount and cotton seed yield, and the drip irrigation increased the nitrogen usage efficiency of the plants. As the amount of nitrogen rate and irrigation water applied was increased, plant height, the number of fruiting branches and bolls were increased. Whereas the amount of applied irrigation water, increased fiber length and the fiber length uniformity index but not fiber fineness according to the nitrogen dose application. Statistical analysis of water levels and nitrogen doses showed that 200 kg ha−1 pure nitrogen and I100 can be recommended.

Study on Dispersion Characteristics of HwBKP Hydrophobized by Repeated Gas Grafting in Polypropylene

This study investigated the fiber dispersion characteristics and physical property changes of HwBKP-PP composites through repeated hydrophobization and recycling of cellulose fiber. The gas-grafted paper was disintegrated and then gas-grafted again to achieve uniform dispersion of the cellulose fibers with PP. With each gas grafting repetition, the interfacial affinity between the hydrophobized fibers and PP improved, leading to enhanced tensile strength and melt flow index of the HwBKP-PP composite material due to the improved fiber dispersibility. However, recycling of hydrophobic paper resulted in the loss of fines in the recycled paper, so that increase in average fiber length caused fiber agglomeration, resulting in poor dispersibility, and subsequently decreasing the tensile strength and melt flow index of the composite.

Effect of pretreated cow dung fiber on rheological and fatigue properties of asphalt binder

Cow dung waste has caused severe environmental pollution and public health issues in China. In this study, the cow dung residues were used as a cheap renewable fiber to modify asphalt binder, providing a new solution for the proper disposal of cow dung waste. Three cow dung fibers with two lengths were prepared using different treatments, including original cow dung fiber (CDF), surface treatments of cow dung fiber (STCDF) and alkali treatments of cow dung fiber (ATCDF). The physicochemical properties of CDF, STCDF and ATCDF were analyzed by scanning electron microscope (SEM) and thermogravimetry (TG). The viscidity, rheological properties and fatigue characteristics of CDF modified asphalt binders (CDFMA) were evaluated using Brookfield viscometer and dynamic shear rheometer. The results showed that the rough surfaces of STCDF and ATCDF improved their thermal stability. STCDF and ATCDF enhanced the resistance to permanent deformation under high temperature conditions of modified asphalt binder. STCDF modified asphalt binders exhibited the best viscosity and rheological performance. The increase of fiber length was positively correlated with the high temperature deformation resistance of CDFMA. CDF, STCDF and ATCDF inhibited fatigue cracking of modified asphalt binders compared to base asphalt binders. ATCDF modified asphalt binders exhibited higher fatigue life and smaller crack under the same cyclic loading. The increase in fiber length had a slight improvement on the fatigue resistance of modified asphalt binders.

N and P fertilization management and their effects on growth, productivity, and quality of cotton cv. Super Giza 86

Two field experiments were carried out at Gharbia Governorate, El-Gemmeiza Agricultural Research Station, Egypt, during 2019 and 2020 seasons using the cotton cultivar Super Giza 86 (Gossypium barbadense L.) to study the effects of N [number of splits; (2, 3 and 4 splits) and time of application], P [sources; mineral, natural, bio-fertilizer, phosphoric acid, and mixture of these sources, time, and method of application] as well as their interactions. The experimental design was a strip plot with three and four replicates in 2019 and 2020 seasons, respectively. The important results indicated that two equal N splits resulted in a significant increase in growth parameters, earliness attributes (except boll shedding% which was decreased), seed cotton yield and its components in both seasons and significantly increased fiber length and fiber uniformity ratio in one season. However, fiber length increased in the second season in favour of four equal N splits. Fiber strength and fineness did not affect.

Flexural properties of fiber-reinforced alkali slag-red mud geopolymer

To improve the flexural performance of alkali slag-red mud geopolymer (AS-RG), polypropylene fiber was uniformly mixed into AS-RG, and a three-point bending test was carried out on fiber-reinforced AS-RG under different conditions; this was done to carry out the structural performance improvement and control test of composite materials. Based on the degradation control technology of fiber structure and properties, the ductility strengthening mechanism of composites was analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD) at the microscopic level. Particle flow numerical simulation software (PFC3D5.0) was used to simulate the whole process of three-point bending failure of the specimen, and the crack evolution law of the specimen was explained. The results show that the flexural strength of AS-RG can be effectively improved by adding a proper amount of polypropylene fiber, and the ability of resisting instability and failure of the material will be improved with the increase of fiber length, which will first strengthen, then weaken, and finally decrease with the increase of the water-binder ratio. Therefore, the combination of fiber length of 9 mm, fiber content of 4 ‰, and water-binder ratio of 0.26 has the best effect on improving the fracture performance of the material. The three-point bending PFC3D numerical test results of samples under different fiber content are basically consistent with the indoor test results. After adding fiber, the formation of the crack zone of the samples obviously lags, and the total number of cracks that the samples can bear under the peak strength increases significantly. This study results can provide a theoretical basis for the flexural performance of fiber reinforced AS-RG.

Study on the influence of drafting forms in front drafting zone of ring spinning frame on fiber motion and yarn quality

Double apron drafting is the general drafting form in the front zone of the ring spinning frame. In the double apron drafting system, the top apron and the bottom apron form an elastic tensor gauge, which can better control the movement of floating fibers and improve yarn quality. In order to investigate quantitatively the influence of the top apron and bottom apron on fiber movement and yarn quality in the double apron drafting system, the differences of fiber acceleration point distribution, yarn irregularity and yarn strength spun by double apron drafting, single apron drafting and simple roller drafting under different process conditions were compared. Compared with simple roller drafting, double apron drafting and single apron drafting can effectively control the fiber movement in the drafting zone. With the increase of fiber length, the difference between the distribution of fiber acceleration points obtained by double apron drafting and that obtained by single apron drafting gradually decreases. When the fiber length is greater than 32 mm, the difference is small. Besides, by analyzing the improvement rate of the top apron and bottom apron on yarn irregularity and yarn strength under different drafting settings, it was found that the overall improvement rate of the bottom apron on the yarn quality was higher than that of the top apron, especially for manmade fiber yarns. Even in some cases, the strength of viscose yarn spun by the single apron drafting process is higher than that of the double apron drafting process.