Image analysis of the luster of fabrics with modified cross-section fibers

We have investigated the luster of modified cross-sectional fiber fabrics as one of the essential quality estimates for clothing development. We have confirmed an objective evaluation method, and have determined the experimental luster characteristics of modified cross-section fibers. The cross-section of the fibers in a fabric affects the appearance of a textile. We used the image analysis method to investigate the luster to determine the critical factors influencing the appearance of modified cross-section fiber fabrics. For similarly structured textiles in a component fabric, clear differences were observed in the fabric weave, density, percentage, and total area of blobs, which is image region. Color played a decisive role in the luster of the textiles, and luster was not significantly influenced by the modified cross-section fabric weave. In addition, the degree of luster did not increase in the order plain to twill to satin for modified cross-sectional fiber fabrics. All the split-type microfibers exhibited higher numerical luster values (percentage of pixels, and number and total area of blobs) than sea-island microfibers did. The degree of luster of the modified cross-sectional fiber fabrics was not high at specular reflection angles.     

Modeling the Fibrillation of Kevlar® KM2 Single Fibers Subjected to Transverse Compression

In this work, fibrillation is introduced as an energy absorbing mechanism in the modeling of Kevlar® KM2 single fibers subjected to quasi-static transverse compression. Fibrillation is simulated using a finite element model of the fiber cross-section containing discrete fibrils connected by interfibrillar cohesive zones. Model predictions of nominal stress-strain response for an assumed bilinear cohesive traction-separation interfibrillar behavior are compared to experimental data. Analysis shows that modeling of the microstructural fibril network, represented by a distribution of strong cohesive interactions, is necessary to capture the experimental response. The model provides valuable insight into the unique deformation mechanisms governing fiber fibrillation under transverse compression.     

Effect of cross-sectional morphology and composite structure of glass fiber felts on their corresponding acoustic properties

This paper presents the effect of cross-sectional morphologies and composite structures of glass fiber felts on their corresponding acoustic properties. Glass fiber felts with random and layered cross-sectional structure are produced by centrifugal-spinneret-blow system. Acoustic properties are determined by a B&K impedance tube. The results show that sound transmission loss (STL) of glass fiber felts with layered cross-sectional structure exhibit greater than that with random cross-sectional structure. However, there is a little difference between the absorption coefficient values for random and layered cross-section. It means that glass fiber felts with layered cross-section are better to improve the sound insulation. With the increase of thickness, STLs of glass fiber felts with the same areal density do not increase monotonically due to the changing of porosity and characteristic impedances. Different glass fiber felts with layered cross-sectional structure are combined to form a variety of composite structures. It finds that assembly order of glass fiber felts have an effect on the total sound insulation. The large mismatch between the acoustic impedances causes multiple reflections leading to the best STL.     

Mechanical enhancement of UHMWPE fibers by coating with carbon nanoparticles

Fiber-reinforced plastic (FRP) is composed of reinforced fibers and matrix resin, and has high specific strength and low-density materials. Because of the orientation of the fibers within them, FRPs are prone to buckling damage when under compression along the axial direction of the fiber, especially flexible organic ones. The compressive performance of FRP is largely dependent on fiber properties. the buckling load of FRP will increase with the increasing of fiber’s. In this study, we developed a way to improve the compressive and bending strength of ultra-high molecular weight polyethylene (UHMWPE) fibers. Carbon nanotubes (CNTs) and vapor-grown carbon fibers (VGCFs) were coated on the surface of UHMWPE fibers by pyrrole vapor deposition. The transverse compressive strength and bending strength of single UHMWPE fibers were determined by microcompression and single fiber bending measurements, respectively. The experiment result showed that coating UHMWPE fibers with CNTs and VGCFs increased both their transverse compressive strength and bending strength. It is excepted that the improved fiber would applied in FRP for better compressive performance.     

Mechanical properties and water absorption of short snake grass fiber reinforced isophthallic polyester composites

Natural fiber composite replaces the conventional and synthetic materials in many fields especially in light weight applications. The randomly oriented short snake grass fiber reinforced isophthallic polyester composites are prepared by hand lay-up technique and finally compression molded. The various length and weight fraction of fiber are used in composite fabrication. The mechanical properties and water absorption under various climatic conditions are examined according to the prescribed standard. SEM image revealing the fiber pullout and breakage of the tensile and impact fractured composite specimens has been analysed and compared with control through scanning electron microscope. The result shows that the mechanical properties increase with increase in fiber length and weight fraction of the composites. The rate of water absorption increases with increase in temperature and time. Obtained experimental tensile strength of the composite is compared with various theoretical models such as Series, Hirsch’s, Halpin-Tsai, Modified Halpin-Tsai and Modified Bowyer & Brader’s and the obtained inferences are discussed.     

Three-dimensional fiber orientation of fiber suspensions flowing through a rotating curved expansion duct

A complete three-dimensional Jeffery equation is solved through both analytical and numerical method to obtain the orientation evolution of a single fiber rotating in a shear flow. The orientation evolutions of a single fiber under different conditions are given. A more complete model for the simulation of fiber orientation is presented and combined with the Runge-Kutta algorithm to obtain the evolution of fiber orientation in the fiber suspensions through a rotating curved expansion duct. The numerical results show that the evolution of fiber orientation along the duct in different cross-sections is quite different. The fiber orientations change drastically in the vicinity of the inlet and then change slowly along the flow direction. The inlet velocity has little effect on the evolution of fiber orientation, but a great effect on the trajectory of the fiber. The effect of the initial fiber orientation on the evolution of fiber orientation is contrary to that of inlet velocity. The effect of rotation rate on the evolution of fiber orientation is much smaller than that of inlet velocity. Near the concave wall region the smaller the fiber aspect ratio is, the more drastically the fibers swing. The fibers near the centerline and the convex wall region do not show a swing. Studying such complex flow will beneficially contribute to reach a better understanding of flow properties in many important manufacturing processes to make composites.     

Scratch deformations of poly (ether ether ketone) composites

The experimental results obtained from scratching a semicrystalline poly (ether ether ketone) surfaces, (PEEK), and its composites are presented in this paper. A semicrystalline PEEK and a carbon fiber oriented PEEK were scratched using conical indenters on a pendulum sclerometer. The carbon fiber oriented PEEK composites were scratched in the parallel, the orthogonal and the transverse direction to the fiber orientation. Subsequent deformations of the surfaces were assessed through subjective evaluation of the images obtained from a scanning electron microscope (SEM). The semicrystalline PEEK samples were found to be deformed by ductile ploughing and brittle deformation mechanism. In addition a fibrillation of the crystalline lamella of the polymer was also seen to be formed in case of severe brittle deformations. Fiber matrix debonding, matrix material debris formation, and fiber breakage were observed to be the dominant deformation mechanisms of the carbon fiber oriented composites. The scratch deformations of fiber oriented polymers were found to be highly dependent on fiber orientation angle relative to the scratching direction.     

Prediction of the fabric’s crease recovery property with Taguchi design of experiment

The creasing characteristic of fabrics is affected by many factors like yarn twist, fabric density, fabric constructions, fabric thickness apart from the fiber type. In the first part of this study, the effect of yarn fineness, yarn twist, fabric tightness and weave construction factors on crease recovery was studied. In the second part of the study, in order to improve the creasing recovery of the fabrics, shape memory alloy (SMA) wires were used and the effect of shape memory alloy (SMA) wire on the crease recovery of cotton fabrics produced with different types of weave constructions were determined. Due to the high cost of SMA wire and the weaving operation adversity the two experimental plans were designed according to Taguchi design of experiment (TDOE). From the analysis of the first part, it was found that the yarn linear density had the greatest effect on fabric crease recovery compare to others. Twist coefficient was the second, weft density was third and the weave construction had the least significant effect on the crease recovery. The fabrics produced with coarser and low twisted yarns with high tightness and longer floats in the weave construction have higher crease recovery property. In the second part of the study, the application of the SMA wire significantly increased the crease recovery angle of the fabrics. The thickness of the SMA wire is very important and the effect depends on the wire thickness. The increase of the SMA wire thickness increases the crease recovery significantly. However it must be appropriate with the yarn and fabric properties. The distance between the SMA wire distances was expected to increase the crease recovery however the effect was found not significant. The fabrics produced with coarser yarns with longer floats in the weave construction have higher crease recovery property. However, statistically the effects of these parameters were found not significant due to the dominant effect of the wire thickness.     

Diameter variations of irregular fibers under different tensions

The cross-section area of animal fibers varies along the fiber length, and this geometrical irregularity has a major impact on the mechanical properties of those fibers. In practice fibers are often subjected to tensile stresses during processing and application, which may change fiber cross-section area. It is thus necessary to examine geometrical irregularity of fibers under tension. In this study, scoured animal fibers were subjected to different tensile loading using a Single Fiber Analyzer (SIFAN) instrument. The 3D images of the fiber specimens were first constructed, and then along-fiber diameter irregularities of the specimens were analyzed for different levels of tensile loading. The changes in effective fineness of the fiber specimens were also discussed. The results indicate that for the wool fibers examined, there is considerable discrepancy in the fiber diameter results obtained from the commonly used single scan along fiber length and that from multiple scans at different rotational angles, and that the diameter variation along fiber length increases as fiber tension increases. The results also show that when diameter reduction treatments are applied to wool by stretching, the reduced average fiber diameter is associated with an increase in both within-fiber and between-fiber diameter variations. So in terms of effective fineness, the change is much smaller than the difference between the average diameters of the parent and treated wool. These results have significant implications for improving the accuracy of fiber diameter measurement and evaluation.     

Effect of Basalt Fiber on the Strength Properties of Polymer Reinforced Sand

This paper displays an experimental study of the effect of basalt fiber on the strength properties of polymer reinforced sand. Laboratory trials of unconfined compression test (UCS), direct shear test, and tensile test were conducted on the specimens treated with polymer and basalt fiber, and several factors including polymer content, fiber content and dry density of sand that will influence the strength behaviors are investigated in detail. Based on test results and scanning electron microscope (SEM) images, the reinforcement mechanism was analyzed. The results showed that the polymer content, basalt fiber content and dry density of sand had greatly improved the strength behaviors of reinforced specimens. The increase in polymer and fiber content had an active effect on strength characteristics, while the angle of internal decreased slightly. The strength properties were enhanced with the increase in dry density, and the effect of dry density on tensile strength is affected by fiber content. The presence of randomly distributed fibers has formed a spatial fiber-sand net in sand, and the additive of polymer solution formed membrane to enwrap sand particles and connect sand and fibers, thereby formed a stable structure in sand. These structures have increased the bonding and interlocking forces between sand and fibers, and decreased the void ratio of reinforced specimens.     

Experimental study on compressive,flexural and fatigue behavior of warp-knitted spacer fabrics reinforced polyurethane cast elastomer composites

This paper reports an experimental study on compressive, flexural and fatigue behavior of polyurethane cast elastomers (PCE) reinforced with warp-knitted spacer fabrics (WKSF). It aims to investigate new applications for these fabrics as the reinforcements for elastomeric parts such as shoe soles, rubber floor coverings, vibration dampening and shock absorbing pads, etc. A series of polyester WKSF with different thickness, structure of outer layer fabric and spacer yarns density was prepared and converted to PCE reinforced WKSF using the hand molding method. All the samples, including the neat PCE, were subjected to static compression, flat and spherical compression, three-point bending and flexural fatigue tests. The results showed that reinforcing PCE with WKSF, considerably enhances its spherical compressive strength (concentrated loading), flexural strength and fatigue resistance. However, it deteriorates flat compressive strength (distributed loading) and recovery behavior after static compression loading. The effect of fiber weight fraction, thickness, structure of outer layer fabric and spacer yarns density on the mentioned properties of the composites was discussed in the paper.     

A study on structural characterization of thermal stabilization stage of polyacrylonitrile fibers prior to carbonization

Structural transformations taking place during the thermal stabilization of polyacrylonitrile (PAN) fiber used for the production of carbon fiber were characterized using a combination of polarized infrared spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and density measurements. Direct relationship between the increasing oxygen content and the density values was confirmed with increasing stabilization time. Linear density values were found to be directly influenced by the stabilization time. Thermal stability of stabilized precursor fibers was evaluated in terms of weight loss and residual weight fraction. The results showed that a residual weight fraction of 65 % at 1000 °C can be obtained but longer stabilization time resulted in a loss of residual weight fraction due to excessive thermal degradation. SEM was used for the observation of surface morphological features of stabilized precursor fibers. Polarized infrared spectroscopy showed the loss of molecular orientation of methylene (CH₂), nitrile (Ct=N), and carbonyl (C=O) groups in direct response to the effects of cyclization, dehydrogenation, and amorphization (i.e. decrystallization) processes taking place during the stabilization stage.     

Goniophotometric study of reflectance of non-circular cross-section polyester monofilament and its yarn under various applied tensions

The relative intensity-angular distribution of surface reflectance of one kind of non-circular cross-section (NCCS), herein referred to as octagonal cross-section, polyester monofilament and its yarn was investigated. Using a goniophotometer (GP), both the horizontally and vertically mounted substrate geometries were used, with the fiber or yarn at various, but known, tensions. An angle of incidence of 45° with respect to the fiber axis was used for the horizontally mounted fiber. The results indicate that the (specular) maximum appears at the expected surface reflectance angle around 40°, with the fiber held straight under applied load. The maximum in the reflection profile for the vertically mounted fiber or yarn, under the same conditions, was around 85°. It was also found, as is to be expected, that the calculated luster of the octagonal cross-section fiber and its yarn, using a Gaussian fitting model, was affected significantly by the load applied for both the horizontal and vertical geometries of the substrate. Further, it was observed that the relative reflection intensity of vertically mounted single octagonal fiber/monofilament was higher than that of horizontally mounted one under the same value of applied tension, while it was the reverse for the yarn from these filaments. With increased tension, the shine values of both horizontally and vertically mounted single fiber increased while those of its corresponding yarn decreased. Further, for both the horizontally and vertically mounted fiber, the difference in shine values for the two cases of tension and no tension was large, whereas such differences were much smaller for the yarn.     

Effect of two bounding walls on the rotational motion of a fiber in the simple shear flow

The effect of two bounding walls on the rotational motion of a freely suspended non-Brownian fiber in the simple shear flow at low Reynolds number was investigated numerically using the lattice-Boltzmann method. Data were reported for the fibers with aspect ratios of 8, 10, and 15 under various ratios of wall gap (2h) to fiber length (L). For 2h/L≥3.0, the time-dependent orientation of the fiber is shown to be in quantitative agreement with the Jeffery’s theory for ellipsoids suspended in an unbounded linear shear flow, and the effect of the walls on the rotational period of the fiber is insignificant for all fibers with different aspect ratios. For 1.8≤2h/L<3.0, the results reveal that the walls have different effects on the rotation of fiber. For 2h/L<1.8, the complete periodical motion of the fiber is suppressed. The fiber rotates to nearly aligning with the flow direction, and then ceases to rotate. In this orientation, the walls have a stabilizing effect on the fiber and this effect is more pronounced for the fibers with large aspect ratio. The fiber finally does not orient with the flow direction, but with a small angle with the flow direction, and the angle is an increasing function of the fiber aspect ratio and dependent on the wall gap.     

External configuration and crimp parameters of PTT (Polytrimethylene terephthalate)/PET (Polyethylene terephthalate) conjugated fiber

The cross-section shape, longitudinal self-crimping configuration of various PTT (Polytrimethylene terephthalate)/PET (Polyethylene terephthalate) filaments were observed and measured via microscope. The crimp parameters of the filaments, including helixes pitch, crimp radius, crimp curvature and regular crimp proportion were calculated, and the relationship between crimp parameters and self-crimping configurations of PTT/PET filament was analyzed. Various shapes of PTT/PET fiber cross-section were detected such as round, peanut, dog bone and pear like shapes. Crimp configurations were found not always regular spatial helix along the longitudinal direction of filament and had significant difference according to the fact whether the filament was undergone textured process. With the length rate of the long axis to the short axis of cross-section increasing, the crimp curvature of filament will also increase. The helix pitch and radius will increase while the crimp curvature will decrease with the increasing linear density for the same cross-section shape of PTT/PET filament.     

The variation of fibrils’ number in the sea-island fiber -low density polyethylene/polyamide 6-

In melt spinning of low density polyethylene/polyamide6 (LDPE/PA6), fibrils’ number in LDPE/PA6 blend fiber is calculated at different take-up velocity. Firstly, PA6 fibrils are dispersed in the LDPE matrix in LDPE/PA6 blend fiber (55:45, weight ratio). The number of PA6 fibrils increases with an increase of the take-up velocity. Because the shorter processing time suppresses the coalescence at the high take-up velocity, it causes an increase of PA6 fibrils. Besides, the irregular shape of PA6 fibrils’ cross section also confirms fibrils’ coalescence. Secondly, LDPE fibrils are dispersed in the PA6 matrix in LDPE/PA6 blend fiber (6:94, weight ratio). However, the number of LDPE fibrils doesn’t change no matter how the takeup velocity is. In case of LDPE/PA6 (6:94) blend fiber, the low weight ratio of the dispersed LDPE causes the absence of fibrils’ coalescence, so fibrils’ number does not change. In conclusion, the variation of fibrils’ number implies the existence of the coalescence phenomenon in the fiber spinning process. The variation of fibrils’ number in the sea-island fiber is of practical importance for manufacturing the micro-fine fiber, and is a method to investigate the coalescence behavior in the extensional flow.     

Study on optimum coagulation conditions of high molecular weight pan fiber in wet spinning by orthogonal experimental design

Orthogonal experimental design (I) and (II) were used to study optimum coagulation technology in wet spinning of high molecular weight PAN nascent fiber. Relationship between shape factor (De) and coagulation conditions such as coagulation bath concentration, temperature, and minus draw ratio was investigated to obtain nascent fiber with the minimum De value and smooth surface morphology. The nascent PAN fiber fabricated at the conditions of 80 wt% coagulation bath concentration (in this paper, the coagulation bath concentration refers to the mass concentration of DMSO in coagulation bath), 0 % minus draw ratio, and 40 °C coagulation bath temperature has the smallest fiber diameter, the most circular cross sectional (minimum shape factor) and smooth surface morphology, and the maximum density, which resulted in the most excellent mechanical properties of nascent PAN fiber.     

Relationship between chemical composition,crystallinity, orientation and tensile strength of kenaf fiber

The physical properties of natural growth fibers such as chemical composition content and fiber diameter are highly affected by environmental issues such as environmental changes and fiber extraction methods. These irregularities of the natural fibers seriously affect its utilization in composite as reinforcements. In this study, taking into account the importance of the fiber tensile strength, the correlation degrees between the kenaf fiber tensile strength and the fiber chemical composition, crystallinity, orientation degree were analyzed by the grey relational analysis method. Both the kenaf single fiber and fiber bundle were used as XRD and tensile strength test sample. The chemical composition content and the FTIR were carried out to obtain a correct result of the chemical composition content. It found that for the different XRD and tensile strength test samples, the single fiber showed lower crystallinity, higher orientation degree and tensile strength compared with the fiber bundle. The cellulose content and the orientation degree got the higher correlation degree with single fiber tensile strength, which was 0.674 and 0.640. The highest factor associated with the fiber bundle tensile strength was the orientation degree, the correlation degree was 0.747. The hemicellulose content and the crystallinity also got high correlation degree with the fiber bundle strength, which was 0.687 and 0.640.     

Fiber dispersion and breakage in deep screw channel during processing of long fiber-reinforced polypropylene

Long glass fiber-reinforced thermoplastics are usually processed by pultruded granules, but glass fiber rovings were used to process long glass fiber-reinforced thermoplastics in this study. This article investigated the dispersion and breakage of fibers during extrusion processing of long glass fiber-reinforced polypropylene containing 30 wt% glass fibers at a certain processing conditions. For this study, the morphology of the surface and polished cross-section of helices was observed by digital photography, as was the morphology of the remaining fiber after burning. On this basis, the fiber/polymer system behavior in the screw channel and the dispersion mechanism of the fiber bundles were analyzed. Moreover, scanning electron microscopy (SEM) was used to observe individual fiber cross-sections to analyze the mechanism of fiber breakage. Finally, the effect of processing conditions such as temperature, screw speed and fiber content on fiber length and dispersion was studied. The results show that the fiber agglomerates composed of fiber bundles form near the barrel surface at the fiber feed point and then undergo three main stages: compression, impregnation, and dispersion. The fiber bundles separate into daughter bundles and individual fibers in different parts of the screw channel. In addition, the results indicate that the fibers can suffer tensile fracture and bending fracture during the extrusion processing. Finally, this paper includes suggestions for improving fiber bundle dispersion and reducing fiber breakage.     

A new expression for the velocity profile in the turbulent pipe flows of fiber suspension

The equation of Reynolds averaged Navier-Stokes with the term of additional stress resulted from fibers and the equation of probability distribution function for mean fiber orientation with the second- and fourth-order orientation tensor of the fiber were derived and solved to explore the characteristics of turbulent fiber suspension in the turbulent pipe flows of fiber suspension. The effect of Reynolds number, fiber concentration and fiber aspect-ratio on the mean velocity were presented and analyzed. It was found that the velocity profile of fiber suspension becomes sharper with decreasing the flow rate and/or increasing the fiber concentration, which agrees with the corresponding experimental ones. The velocity profile becomes steeper as fiber aspect-ratio increases. Fibers at this range of concentration and scales play a role in the increase of viscosity. Finally, the prediction formula of velocity profile involving the effect of Reynolds number, fiber concentration, and aspect-ratio for the turbulent pipe flows of fiber suspension was derived.