Fiber Length Distribution Research Articles

A Preliminary Study on the Effect of Short Fiber Content on Drafting Force and its Variability

ABSTRACT Fiber length is one of the most important factors affecting the drafting force and its variability. By analyzing the draftometer data, the interaction between the dynamic drafting force and its variability with respect to the short fiber content of carded cotton sliver is discussed. Two cotton slivers with similar physical properties, except for their short fiber content (i.e.8.8% and 5.3%) were tested. An increase in drafting force and a decrease in its coefficient of variance (CV%) was noticed for the sample with higher short fiber content. With back gauge increase (from 43mm to 51 mm), the drafting force decreased and its variability increased, irrespective of short fiber content. The inter-fiber cohesion generally decreased, with widened roller settings. It was shown that a broader distribution of fiber length in an assembly of fibers created, more contact points in the strand being aligned by the drafting process. The CV of drafting force increased as we moved from the smaller back ratch to a wider one, which also contributed to sliver irregularity.

Effect of fiber feeding route upon extrusion process on the electromagnetic, mechanical, and thermal properties of nickel-coated carbon fiber/polypropylene composites

Extrusion processing and properties of fiber-reinforced polymer matrix composites may be influenced by the fiber feeding route upon extrusion. The purpose of the present study was to investigate the effect of fiber feeding route on the fiber length distribution, electromagnetic interference shielding effectiveness (EMI SE), tensile, and flexural properties and heat deflection temperature of resulting composites with different fiber contents. H–NiCF/polypropylene and S–NiCF/polypropylene pellets were produced through two different feeding routes of nickel-coated carbon fiber (NiCF), hopper feeding (H) and side feeding (S) upon extrusion process, respectively. NiCF-reinforced polypropylene (PP) composites were fabricated by means of compression molding using each pellet, respectively. The effect of fiber feeding route on the electromagnetic, mechanical, and thermal properties of the composites with various NiCF contents was studied. S–NiCF/PP composites exhibited the EMI SE, tensile, and flexural properties and heat deflection temperature higher than H–NiCF/PP composites. The improved properties of S–NiCF/PP composites were ascribed to higher aspect ratio and longer fiber distribution of NiCF remaining in the composite than H–NiCF/PP counterparts, due to less shearing and fiber damages during extrusion.

Impact of the Fiber Length Distribution on Porous Sponges Originating from Short Electrospun Fibers Made from Polymer Yarn

AbstractUltralight highly porous sponges made of short electrospun polymer fibers have gained significant attention for a variety of applications. According to the established procedures, short electrospun fibers are obtained by cutting or homogenization of electrospun fibers in suspension, which yield fibers with inhomogeneous fiber length. The role of the fiber length distribution and the fiber length in the mechanical compressibility of the sponges is unknown. Therefore, as a model study, sponges made from suspensions of short electrospun poly(acrylonitrile) (PAN) fibers with controlled fiber length distribution are investigated, and the role of the fiber length distribution in the compressibility of the sponges is analyzed quantitatively. These sponges are also compared to the ones prepared by established procedure as a benchmark. It is found that the compression stress and modulus of ultralight sponges with monodisperse short fibers are respectively 32% and 45% higher than that made with polydisperse short fibers. The study also shows that sponges made from longer fibers have higher modulus in comparison to the sponges made from shorter fibers.

Impact of fiber length and fiber content on the mechanical properties and electrical conductivity of short carbon fiber reinforced polypropylene composites

This paper evaluates the influence of fiber length and fiber content on the mechanical and electrical properties of injection molded short carbon fiber (CF) reinforced polypropylene (PP) composites. At first, four injection molded PP/CF composites containing 10 vol.% CF were produced using varying compounding parameters in order to achieve different fiber length distributions. Subsequently, the processing conditions giving the longest fibers in the final composites were used for the production of PP/CF test specimens containing varying amounts of CF (5, 10 and 15 vol.%). Identical processing parameters were used for the varying fiber contents. The fiber length distributions of all composites were determined. Furthermore, the tensile and impact properties were tested as well as heat deflection temperature and electrical conductivity. Within the investigated range, composite properties were dependent on fiber length and fiber content. Tensile strength, tensile modulus, notched impact strength and electrical conductivity showed highly accurate linear correlation with the weight average fiber length. Tensile strength and modulus even showed a very well fitting linear correlation with the fiber volume content. The best results were achieved for a composite containing 15 vol.% CF, with 98 MPa tensile strength, 14.4 GPa tensile modulus and an electrical conductivity of 10 2 S/cm.

Tearing of post-consumer cotton T-shirts and jeans of varying degree of wear

The demand for textile fibres is growing quickly. However, global cotton production has stabilized around 25 Mton/year. This is a sound development since cotton cultivation causes major sustainable development issues. Even if regenerated cellulose fibre production steadily grows, it is still only from a sixth to a fifth of cotton volumes. Hence, it is essential to find resource-efficient routes to generate alternatives to virgin cotton. There are many promising research initiatives that discover the possibility to utilize waste streams of neat cotton and cotton in fibre blends as raw materials for dissolving pulp for regeneration into, for example, viscose or Lyocell. However, there is a much simpler and energy-efficient route at hand. If fabrics are disintegrated mechanically, the separated fibres can be turned into yarn again. However, since fibre length is a key parameter to accomplish strong and durable textiles, fibre length loss upon tearing should be minimized. This study evaluates how fibre length distribution alters upon tearing of post-consumer cotton waste of two different constructions: denim and single jersey; and different degrees of wear, rendering four different fractions: (1) barely worn denim, (2) rather worn denim, (3) barely worn single-jersey and (4) rather worn single-jersey. Before tearing, the garments were dissembled, their yarns were characterized, fibre length distributions were manually determined for (1)–(4). Length analysis of the recovered fibres after tearing revealed that the length drop was most severe for (a) the finer single-jersey and (b) the barely worn fractions. The findings suggest that significant wear does not exclude from mechanical recycling.

TAM BB‐2139 ELSU extra long staple upland germplasm

AbstractThe minimum or nondiscount upper half mean length (UHML) of upland cotton, Gossypium hirsutum L., for consumption in the United States is 27 mm, while the minimum for international markets is 28 mm. This discrepancy is based on the remaining US spinning mills predominately using rotor spinning technology, while ring spinning predominates internationally. Along with increased international base for staple length, processors desire greater fiber strength, decreased short fiber content, and more uniform fiber length distributions to withstand ever‐increasing processing speeds and rigor and to produce premium yarns with improved end use quality. A narrower micronaire range (or finer yet mature fibers) or finer fibers is also desirable. With increasing export of US cotton and advances in spinning technology, improvements of fiber quality parameters are essential for the competitiveness of US upland cotton. Producers receive premiums for improved fiber quality, and their product is more competitive with manmade fibers in the textile market. TAM BB‐2139 ELSU (extra long staple upland) (Reg. no. GP‐1071, PI 691840) exhibited UHML exceeding the control cultivars and averaged 35.5 mm UHML across six locations in central and south Texas in 2016–2017. It also averaged 36.6 mm in the 2016 USDA Regional High Quality Test when grown across nine locations in eight states. The minimum UHML for G. barbadense L., pima cotton, is 34.9 mm. TAM BB‐2139 ELSU will provide upland cotton breeders with a source for improving UHML.

RVE modelling of short fiber reinforced thermoplastics with discrete fiber orientation and fiber length distribution

This study presents an analysis of modelling aspects on the effective composite properties of short glass fiber reinforced thermoplastics using representative volume elements (RVE). Although, many investigations were published showing effects of different modelling parameters of RVEs, we further elaborate in this contribution the parameters: influence of fiber packing, fiber shape, bonding of the fibers to the matrix, fiber length distribution and fiber orientation. The knowledge of these influences is used to determine the extent to which the increased modelling accuracy and thus the computational effort leads to an improved RVE’s forecast quality. This objective is achieved by creating and comparing different RVE models of a PBT-GF20 composite. The information required for the RVE models is obtained by experimental characterization of the PBT-GF20 and the PBT matrix material. It can be concluded based on the results of the numerical investigations in conjunction with the experimental tests of the composite that fiber packing, fiber length distribution, fiber orientation and fiber geometry are essential for a precise determination of the effective composite properties.

Endpoint Detection of Partially Overlapping Straight Fibers using High Positive Gaussian Curvature in 3D images

This paper introduces a method for detecting endpoints of partially overlapping straight fibers in three-dimensional voxel image data. The novel approach directly determines fiber endpoints without the need for more expansive single-fiber segmentation. In the context of fiber-reinforced polymers, endpoint information is of practical significance as it can indicate potential damage in endless fiber systems, or can serve as input for estimating statistical fiber length distribution. We tackle this challenge by exploiting Gaussian curvature of the surface of the fibers. Fiber endpoints have high positive curvature, allowing one to distinguish them from the rest of a structure. Accuracy data of the proposed method are presented for various data sets. For simulated fiber systems with fiber volume fractions of less than 20 %, true positive rates above 94 % and false positive rates below 5 % are observed. Two well-resolved real data sets show a reduction of the first rate to 90.3 % and an increase of the second rate to 13.1 %.

Efficient Bayesian Function Optimization of Evolving Material Manufacturing Processes.

The scale-up of laboratory procedures to industrial production is the main challenge standing between ideation and the successful introduction of novel materials into commercial products. Retaining quality while ensuring high per-batch production yields is the main challenge. Batch processing and other dynamic strategies that preserve product quality can be applied, but they typically involve a variety of experimental parameters and functions that are difficult to optimize because of interdependencies that are often antagonistic. Adaptive Bayesian optimization is demonstrated here as a valuable support tool in increasing both the per-batch yield and quality of short polymer fibers, produced by wet spinning and shear dispersion methods. Through this approach, it is shown that short fiber dispersions with high yield and a specified, targeted fiber length distribution can be obtained with minimal cost of optimization, starting from sub-optimal processing conditions and minimal prior knowledge. The Bayesian function optimization demonstrated here for batch processing could be applied to other dynamic scale-up methods as well as to cases presenting higher dimensional challenges such as shape and structure optimization. This work shows the great potential of synergies between industrial processing, material engineering, and machine learning perspectives.

Study on Fiber Cutting Performance of Isometric Straight Bar Plate with Different Bar Angle

The refining plate is a direct-acting component of refiners in pulping, and the bar profile of it have a major impact on fiber cutting, which affects the paper forming and strength of the formed paper. In this paper, the fiber average length, the fiber length distribution, the original fiber cutting rate and adjacent fiber cutting rate of samples collected in different refining time are used to analyze the fiber cutting mechanism of the isometric straight bar refining plates with different bar angles. The results show that the fiber cutting performance of plates gradually decreases and the limit fiber cutting length of the plate increases with the increase of the bar angle which is opposite to the conclusion predicted by specific edge load (SEL). However, the fiber cutting action of plates is gradually weakened until the average fiber length is reduced to the limit cutting length of plates. Meanwhile, the cutting mechanism of the straight bar plates with different bar angles is different. The larger bar angle of plate, the lower fiber cutting rate and the adjacent cutting rate of which is basically kept constant during refining, while the adjacent cutting rate of smaller bar angle plate on fibers gradually decreases with refining and finally remains constant. The study on the cutting performance of different bar angle plates has positive significance for the selection and design of refining plates for different pulping process.

Quantifying cellulose accessibility during enzyme-mediated deconstruction using 2 fluorescence-tagged carbohydrate-binding modules

Two fluorescence-tagged carbohydrate-binding modules (CBMs), which specifically bind to crystalline (CBM2a-RRedX) and paracrystalline (CBM17-FITC) cellulose, were used to differentiate the supramolecular cellulose structures in bleached softwood Kraft fibers during enzyme-mediated hydrolysis. Differences in CBM adsorption were elucidated using confocal laser scanning microscopy (CLSM), and the structural changes occurring during enzyme-mediated deconstruction were quantified via the relative fluorescence intensities of the respective probes. It was apparent that a high degree of order (i.e., crystalline cellulose) occurred at the cellulose fiber surface, which was interspersed by zones of lower structural organization and increased cellulose accessibility. Quantitative image analysis, supported by 13C NMR, scanning electron microscopy (SEM) imaging, and fiber length distribution analysis, showed that enzymatic degradation predominates at these zones during the initial phase of the reaction, resulting in rapid fiber fragmentation and an increase in cellulose surface crystallinity. By applying this method to elucidate the differences in the enzyme-mediated deconstruction mechanisms, this work further demonstrated that drying decreased the accessibility of enzymes to these disorganized zones, resulting in a delayed onset of degradation and fragmentation. The use of fluorescence-tagged CBMs with specific recognition sites provided a quantitative way to elucidate supramolecular substructures of cellulose and their impact on enzyme accessibility. By designing a quantitative method to analyze the cellulose ultrastructure and accessibility, this study gives insights into the degradation mechanism of cellulosic substrates.

Data-Driven Predictive Probability Density Function Control of Fiber Length Stochastic Distribution Shaping in Refining Process

Pulp is the most important raw material in paper industries, whose fiber length stochastic distribution (FLSD) shaping directly determines the energy consumption and paper quality of the subsequent papermaking processes. However, the mean and variance are insufficient to describe the FLSD shaping, which displays non-Gaussian distributional properties. Therefore, the traditional control method based on the mean and variance of the fiber length is difficult to control the FLSD shaping effectively. In this article, a novel data-driven predictive probability density function (PDF) control method is proposed for the FLSD shaping in the refining process. First, the PDF of FLSD shaping is approximated by a radial basis function neural network (RBF-NN) and the parameters of each RBF basis function are tuned by using an iterative learning law. Second, the random vector functional link network (RVFLN)-based data-driven modeling method is employed to construct the prediction model of the weight vector. Consequently, the predictive controller is designed based on the constructed PDF model of the FLSD shaping in the refining process and the stability issue of the resulted closed-loop system is discussed. The experiments using industrial data are given to illustrate the effectiveness of the proposed method. Note to Practitioners —Pulp quality control in the refining process plays a critical role in the optimization of product quality and energy saving in the pulping and papermaking processes. Different from the conventional control method based on the mean and variance of the fiber length, a novel data-driven predictive PDF control method is proposed for the non-Gaussian stochastic distribution dynamic characteristics of the fiber length, which is used to achieve the desired PDF shaping of fiber length distribution. This kind of novel control method includes the control of the traditional mean and variance of the fiber length in some sense and has applications that are more extensive.

Comparing non-destructive 3D X-ray computed tomography with destructive optical microscopy for microstructural characterization of fiber reinforced composites

Due to their lightweight, relatively high stiffness properties, and formability into complex shapes, discontinuous fiber composites are advantageous for producing small and medium size components. Improved characterization techniques and post-processing methodologies are required for more reliable quantification of the microstructure and defect distributions in these materials, in order to employ model-based approaches to assess their structural integrity. This work compares a non-destructive X-ray approach with a destructive optical microscopy approach for characterizing the microstructural attributes, specifically the fiber volume fraction, porosity volume fraction, fiber orientation distribution, and fiber length distribution of discontinuous glass fibers in a polypropylene matrix. Additionally, a method for destructively determining the ambiguous components of the orientation tensor (related to the sign ambiguity of the out-of-plane angle in a destructive cross-sectional cut of a fiber) over a large surface area is included. It was found that fiber volume fraction and average fiber aspect ratio matched well, while fiber orientation and porosity detection had small but notable differences. The differences in the detection capabilities of each technique are quantified and discussed shedding light on the specific advantages and disadvantages of each approach, and enabling engineers to quantify uncertainty in their microstructural characterization measurements especially as they relate to model based structural integrity activities.

Geometric Analysis Based Double Closed-Loop Iterative Learning Control of Output PDF Shaping of Fiber Length Distribution in Refining Process

In order to improve the pulp quality and to reduce the energy consumption, the fiber length distribution (FLD) is generally employed as one of the important technological indexes in the refining process. Considering that the traditional mean and variance of fiber length are unable to adequately characterize the non-Gaussian distribution properties, this paper proposes a novel geometric analysis based double closed-loop iterative learning control (ILC) method for probability density function (PDF) shaping of output FLD in the refining process. Primarily, a radial basis function (RBF) neural network with Gaussian-type is utilized to approximate the square root PDF in the inner loop, where the RBF basis function parameters (center and width) are tuned between any two adjacent batches by using an ILC law, and the subspace identification method can be applied to establish the state-space model of weight vector. Then, for the sake of accelerating the convergence rate of the closed-loop system, a geometric analysis based ILC method is adopted in the outer loop. Finally, both simulation and experiments demonstrate the effectiveness and practicability of the proposed approach.

Fiber aspect ratio effect on mechanical and thermal properties of carbon fiber/ABS composites via extrusion and long fiber thermoplastic processes

The present study explores the effect of the aspect ratio of carbon fiber on the mechanical, thermal, and impact properties of carbon fiber-reinforced acrylonitrile-butadiene-styrene (ABS) matrix composites, which were produced using: (1) chopped carbon fibers with different lengths by means of twin-screw extrusion followed by injection molding; and (2) long fiber thermoplastic (LFT) pellets with different lengths by means of LFT followed by injection molding. The results revealed that the carbon fiber/ABS composites made by using carbon fiber/ABS LFT pellets exhibited the tensile, flexural, dynamic mechanical thermal, heat deflection temperature, and impact properties higher than those by using conventionally extruded carbon fiber/ABS pellets. It is noted that 12-mm-long LFT pellets contributed most to improving the mechanical and thermal properties of carbon fiber/ABS composites, compared to 6- and 24-mm-long LFT pellets. Meanwhile, the Izod impact strength of the composites was highest in the case of 24-mm-long LFT pellets. The improvements in the mechanical and thermal properties of carbon fiber/ABS composites were explained by different length distribution and aspect ratio of carbon fibers existing in the composites produced via conventional twin-screw extrusion and LFT processes, respectively.

Mechanical properties of short basalt fibre reinforced polypropylene and the effect of fibre sizing on adhesion

The focus of this study was to investigate the potential of short basalt fibre (BF) as reinforcement for polypropylene (PP) and the effect fibre sizing has on adhesion and resultant mechanical properties. Short fibre PP composites were manufactured at fibre loadings of 10, 20 and 30 wt% using fibres coated in multi-purpose epoxy based sizing and four experimental PP tailored sizings. SEM image analysis of polished composite cross-sections showed that dispersion was independent of what matrix the fibre sizing was designed for. Fibre length distribution showed the final fibre length of BF was larger than glass fibres in PP composites, which is attributed to its higher abrasive resistance. DSC revealed in general basalt does not influence the crystallinity of PP but some sizings resulted in a 2–3%increase, however, BF increases onset crystallisation temperature by ~3 °C. Tensile and flexural properties of PP can be significantly increased by up to 64% (tensile strength) and 110% (tensile modulus) through the addition of short BF with properties increasing as fibre content increases; however the impact strength simultaneously decreases. Mechanical properties were highly dependent on fibre sizing, where fibres indicating good adhesion provided the greatest increase in tensile and flexural strength but resulted in lower impact strength. Analysis of the fibre-matrix interface highlighted the significant effect sizing has on interfacial shear strength where improvements of 117% were evident. This study highlights the potential of BF as an effective reinforcement for PP while enforcing the importance and advancements of fibre sizing on promotion of adhesion.

Computer method of processing of deformed steel wire microstructures images for its properties analysis

Mechanical properties of board-bronzed wire depend from one side on the wire rod microstructure from which it is produced and from the other side – determines by peculiarities by the microstructure of the wire itself. At present, there are no generally accepted methods of deformed wire microstructure analysis allowing establishing relationship between characteristics of wire deformation and microstructure characteristics. A mathematical apparatus and new algorithm for processing of microstructure of pearlite steel wire after drawing elaborated based on microstructure image processing and its parameterization. As the main parameter of microstructure, the density function of statistical distribution of fiber lengths used, which allows characterizing quantitatively image of microstructure. Based on the experimental data of OJSC “BMZ – management company of “Byelorussian metallurgical company” holding” correlation demonstrated between degree of wire twisting and degree of delamination. On the basis of samples of perlite steel and their images obtained for bronzed bead wire manufactured at OJSC “BMZ – management company of “Byelorussian metallurgical company” holding” density functions of statistical distribution of perlite microstructure fiber length for the group of samples calculated. Criteria for wire microstructure analysis, based on density distribution function along length of fibers, as well as reduced distribution function proposed. Correlation between degree of delamination, number of wire twists and characteristics of its microstructure determined, calculated using the distribution function of wire fibrous structure with pronounced texture in the cross section.

Controlling the Aspect Ratio of Supramolecular Fibers by Ultrasonication

AbstractTailoring the fiber length of supramolecular fibers with a homogeneous length distribution is challenging. Typically, self‐assembly processes, a bottom‐up approach, allow controlling the supramolecular fiber diameter but not the fiber length. Therefore, in this study, a top‐down approach, namely ultrasonication, is applied to achieve dimensional control of the length of supramolecular fibers. As a supramolecular building block, the benzenetrisamide (BTA),1,3,5‐tris(2,2‐dimethylpropionylamino)benzene (t‐Bu‐BTA), is selected since it effectively forms rigid supramolecular submicron fibers from solution. The important ultrasonication processing parameters, such as sonication time, fiber concentration, dispersion medium, and dispersion temperature are systematically varied to determine their influence on the final fiber length and length distribution. Controlling the cutting into short submicron fibers is readily achieved by adjusting the applied sonication time and the viscosity of the dispersion medium. Based on these results, it is now possible to tailor the aspect ratio of supramolecular submicron fibers.

Effect of Lubricants on Fiber Length Distribution and Properties of Glass Fiber Reinforced Composites Based on Polyamide 1010

Influence of lubricants such as montan waxes and fatty acid esters, on properties of glass fiber reinforced composites based on polyamide 1010. Composites with 40 % wt. glass fibers were obtained on twin-screw extruder, while the fiber breakage occur. Fiber length distribution were measured. It is shown, that adding of 0.5 % wt. of lubricants increase content of glass fibers longer than 2 critical length and improve mechanical properties.

Effects of Fiber Dimension and Its Distribution on the Properties of Lyocell and Ramie Fibers Reinforced Polylactide Composites

The regenerated cellulose fiber (Lyocell) and natural cellulose fiber (ramie) with different initial lengths were used to reinforce polylactide (PLA) by melt compounding and injection molding. The fiber dimension and its distribution in composites after injection molding were analyzed by high-resolution Fiber Quality Analyzer (FQA). Moreover, the contents of small fibers with length < 0.2 mm were also provided by FQA. Then the influences of fiber dimension and its distribution on the mechanical properties of the composites were investigated. The results showed that fiber length was reduced during compounding and injection molding processes, and the longer the initial fiber length, the more severe the length declined. Compared with ramie fiber, Lyocell fiber showed a longer fiber length, smaller diameter and narrower width distribution in composite after injection molding. Additionally, the content of small fiber played an important role in the analysis of the relation between the fiber dimension and mechanical properties of composites owing to its smaller aspect ratio. The different mechanical characteristics of the PLA composites were attributed predominantly to the fiber aspect ratio and the small fiber content. By comparison, Lyocell fiber exhibited better reinforcement for PLA due to the higher aspect ratio and lower small fiber content. The tensile strength, tensile modulus and impact strength of Lyocell/PLA composite were increased by 8.61 %, 75.43 % and 26.9 %, respectively.