Interfiber Friction Research Articles

The role of impact energy and silica concentration on dynamic impact and quasi-static puncture resistance of fabrics treated with shear-thickening fluids

The primary objective of this study is to reveal the role of shear-thickening fluids on the low-speed impact behavior and quasi-static puncture resistance conditions of impregnated p-aramid fabric. This was achieved by progressively increasing the silica ratio methodically. Rheological experiments indicated that 60% represents a crucial threshold for silica content, over which the rheological performance of fluids markedly improves. The impregnated targets exhibited a substantial increase in both dynamic impact and quasi-static puncture resistance in comparison to the neat fabric. Results from tests using the same amount of impact energy showed that impregnated targets had much better impact resistance (ranging from 30.5% to 119.2%) and better energy absorption (ranging from 22.9% to 61.3%) than the untreated targets. In quasi-static tests, impregnated targets exhibited significantly higher puncture resistance, ranging from 42.3% to 90.46%, compared to the neat fabric. The enhanced performance of impregnated targets was ascribed to the presence of interfiber friction, the thickening mechanism of the fluid, and the hardness of the particles. Compared to the neat fabric, the performance enhancement achieved in dynamic impact tests is greater than that observed in quasistatic tests. The variation in performance was associated with the contact area of the threat with the target. Due to the intense force exerted by the knife tip, its contact area with the target is smaller in comparison to that of the impactor. This caused the particle hardness and thickening mechanism to play a lesser role in quasi-static tests compared to impact tests. In addition, to reveal the effect of impact energy, tests were carried out at three different impact energy levels: 20J, 40J, and 60J. The impact resistance of both neat and impregnated textiles improved as the impact energy went up. Nevertheless, the neat fabric exhibited a greater augmentation in resistance in contrast to the impregnated one.

High Frictional Coated Multi-Layer Ballistic Fabrics for High Velocity and Hypervelocity Impact Protection

Increasing the inter-fiber friction of ballistic fabrics is crucial for improving their impact shielding performance. Shear thickening fluid (STF) impregnation is commonly used to improve inter-fiber friction, but it has several fundamental shortcomings. Polymer coating, with its superior properties, can be an ideal material for increasing the friction coefficient of fabrics. Our study aimed to evaluate the effectiveness of the coating process in enhancing the energy absorption mechanism within and among the fabric layers. Additionally, we investigated the capability of a multi-layer coated fabric system for hypervelocity impact shielding and spall liners. Our findings demonstrated the effectiveness of the coating process in improving the ballistic limit of the fabric system. Coated fabrics showed a 19.6% and 23.4% increase in specific energy absorption compared to pristine fabrics. We conducted hypervelocity impact experiments with impact velocities between 1.9 km/s to 2.1 km/s using a triple bumper system. The front bumper generated a debris cloud, the back bumper comprised the coated fabrics, and the third bumper acted as a witness plate. We compared the area of impact on the witness plate and the penetration area to estimate the efficiency of the coated fabrics. Our results showed that the coated fabrics had a higher area of impact with lower intensity of damage and a decrease in the penetration area compared to pristine fabrics with similar areal densities, indicating excellent impact shielding performance.

COMPLEMENTARY ENERGY PRINCIPLE FOR CABLE NETWORKS IN TERMS OF FORCE VECTOR VARIABLE

An alternative approach to the variation formulation of static equilibrium problem for cable networks is proposed. The dual minimization principle is derived in terms of force variables. The full vector force in the cable member is chosen as the dual variable. Unlike the previously proposed treatments of the problem using the scalar axial force variable the elastic energy retains the most general form until the closing steps. It is only assumed to be a convex function of the member end-to-end vector. As a result the nonsmooth asymmetric response of the cable does not appear in the form of inequality in the very beginning. Instead it shows up in the final form of the complementary energy functional, which turn out to be non-differentiable for zero member forces. The kinematic relations between member elongations and nodal displacements convert into the force equilibrium conditions in terms of nodal reactions and member force vectors. The Dirichlet boundary conditions appear in the dual form as a linear term in the complementary energy functional. For the linear elastic cables this approach lead to a second-order cone optimization problem with two sets conical constraints. Such formulation provides flexibility and thus can be potentially extended to account for phenomena such as inter-fiber friction and adhesion. Keywords: complementary energy, variational principles, cable networks

Effect of Laundry Parameters on Micro Fiber Loss during Washing and Its Correlation with Carbon Footprint

ABSTRACT Nowadays, with the fast growing fashion trend, a surge in fashion demand is there. In future, this demand may expect to increase further in multifold. A particular apparel design is not being used for longer period due to the fast changing fashion and this will cause the shedding of micro fibers. Most of the clothes are blends of polyester (synthetic fibers) and cotton (natural fibers) (P/C: 70:30) and when wash these clothes, the shed fibers coming out and pollute the environment. These shed fibers poses a major threat to aquatic and terrestrial ecosystem and also human health. The experimental study was performed on washing machine, considering three parameters – time (duration of washing), detergent concentration of washing liquor and mechanical stress level, to study the shed fibers. The study shows that the major contributing parameter causing more fiber loss was found to be 1% (lower) detergent concentration, this was perhaps due to decrease in inter-fiber friction. On the other hand, high micro fiber loss was achieved at higher mechanical stress and processing time. Also, the increased mechanical stress, increases the friction between the fabric and drum. Thus increases the electricity consumption. The combined impact of time and detergent concentration, increase the fiber loss. With higher processing time and lower detergent concentration, increases the micro fiber loss. The increased processing time and mechanical stress increases the micro fiber shedding and electricity consumption.

Chemical\u2013physical and dynamical\u2013mechanical characterization on Spartium junceum L. cellulosic fiber treated with softener agents: a preliminary investigation

Long cellulose fiber (10–30 cm), extracted from Spartium junceum, was chemically treated with different softening agents with the aim to improve its textile applicability. A preliminary sensory evaluation of the treated fibers revealed an evident, though qualitative, improvement of the fiber softness. The effects of the softening agents on the fiber was evaluated quantitatively, by means of macroscopic measurements of the wettability, viscoelasticity, and thermal (thermal gravimetry) properties. Moreover, the effects of the softening treatments on the microscopic structure of the fiber and on its properties at a molecular level, were studied by optical and scanning electron microscope and X-ray diffraction (XRD), respectively. The macroscopic analysis showed that the softeners used increases the hydrophilicity and water wettability of the cellulose fiber with respect to the raw one. Moreover, the dynamical mechanical analysis on sample yarns showed that the softeners increase the interfiber frictional forces. A linear correlation between the interfiber friction and the increase of hydrophilicity and fiber wettability was shown. The treated fiber exhibits a more homogeneous thermal behaviour, due to more homogeneous structural features, since the thermal-induced cellulose fibrils depolimerization undergoes a marked temperature range contraction. These data can be well related with those obtained by microscopy analysis, showing that the fiber surface, after the treatment, appears thinner and less rough, as well as with the XRD analysis, which shows that softeners induce a significant decrease of the fiber crystallinity.

Tensile behavior of non-crosslinked networks of athermal fibers in the presence of entanglements and friction.

Many biological and soft artificial materials contain a random network of non-crosslinked fibers as their main structural component. The excluded volume interactions (contact forces) at fiber contacts control the mechanical behavior of these systems. This physics has been studied extensively in compression, but little is known about the relation between network structure and its mechanical response in tension. In particular, although occasionally used conjecturally, the notion of fiber entanglements in athermal networks is not well defined, nor is it clear what role entanglements play in athermal network mechanics. The primary contribution of this work is the introduction of a measure of the degree of entanglement of a system of random athermal fibers, and the definition of its relationship with the mechanical behavior of the network. Entanglements confine the fibers during tensile loading, reduce the auxetic effect in mat-like networks, and maintain the inter-fiber contact density. In the absence of this contribution, reduction of the contact density during tensile loading due to auxeticity results in stress reduction. Entanglements stabilize the network via a tensegrity mechanism similar to that operating in woven materials and lead to network stiffening. The relation between the proposed measure of entanglements and the fiber volume fraction is defined. The effect of inter-fiber friction on the mechanics of entangled mat-like non-crosslinked fiber networks is also evaluated.

A Study on the Recycling of Kraft Carrier Board by Dry Circular Action Pre-Treatment and Alkaline Soaking

Kraft carrier board (KCB) is a packaging material that requires strong wet strength, so sizing and wet strength agents are applied in the manufacturing process. Therefore, the kraft carrier board will not get wet and disintegrated easily during pulping. In order to solve the problem of disintegration of KCB, a circular action treatment (CAT) was used, which was designed to solve the problem of shortening of fiber length and poor dewatering caused by beating of old corrugated containers. CAT physically hits raw materials by spinning steel chains. In this study, we tried CAT to improve the disintegration efficiency of KCB. In addition, the effect of alkaline soaking of KCB on the recycling efficiency was analyzed. Untreated KCB showed low disintegration efficiency and even NaOH had little effect on it. Meanwhile, the disintegration efficiency was improved by the dry CAT, and it was further improved by introducing NaOH in soaking treatment. Fiber length and fiber width of KCB were not changed by CAT. However, the recycled sheet based on CAT treated KCB showed high bulk and bad formation due to the relatively low flexibility of CAT treated KCB fibers. Promoted efficiency of disintegration resulted in a significant decrease of shear forces at pulping stage of CAT treated KCB and so fiber flakes didn’t have sufficient interfiber frictions after all. Enhancement of the defibration efficiency resulted in a significant decrease in shear force in the pulping stage of CAT treated KCB, thus the fiber flakes did not have sufficient interfiber friction. The physical properties of the recycled KCB sheet were mostly high in stock without CAT treatment.

Optimization of Process Parameters to Control Yarn Packing Density of Cotton Spun Yarn by Using Multiple Regression Models

Ring spinning frame is the most common and widely used technique for the production of yarn. This yarn subsequently utilized for the production of fabrics. Recently the research studies are more emphasis to create the living comfort condition. The yarn package density has a vital role to determine the feel, comfort, bulkiness and dyeing characteristics of the spun yarn. The yarn packaging density is largely influenced by the yarn process parameters. Ring spinning technique is the most common and widely used for the production of yarn. This yarn subsequently utilized for the production of fabrics. Recently the research studies are more emphasis to create the living comfort condition. The yarn package density is a vital role to determine the feel, comfort, bulkiness and dyeing characteristics of the spun yarn. It is largely influenced by the yarn manufacturing techniques and raw material used. The effects of spinning process parameters on packing density will be helpful to predetermine the yarn comfort behaviour prior to the complete the fabric manufacturing process. Mechanical behaviour of the staple yarn depends on the fiber characteristics and the yarn structure i.e. the arrangement of the individual fiber on the cross-section of the yarn. The fiber distribution on the cross section of the yarn and packing density of yarn has been investigated. The study provides how the spinning process parameters affect the internal structure of ring spun yarn. The aim of the study is to improve the package density of the yarn to achieve dynamometric and comfort properties of yarn to attract a wide variety of customers. Yarn Packing Density represents inter-fiber distance and friction, hence controlling the mechanical and comfort properties of the yarn. The main objective of this study is to control the packing density of yarn during the spinning process. In this work the 100 percent cotton used as raw material and spun on a ring spinning machine. The 135 ring yarns samples have been produced from three different types of yarn counts include (Ne 8, 16 and 24) with nine different samples of identical counts were produced. The three different variables within the count sample are TPI and spindle speed and count. Yarn packing density was calculated by using the driven equation by the application of multiple regression models. The final result shows that packing density has directly related to the TPI, Spindle speed and count

Optimization of Process Parameters to Control Yarn Packing Density of Cotton Spun Yarn by Using Multiple Regression Models

Ring spinning frame is the most common and widely used technique for the production of yarn. This yarn subsequently utilized for the production of fabrics. Recently the research studies are more emphasis to create the living comfort condition. The yarn package density has a vital role to determine the feel, comfort, bulkiness and dyeing characteristics of the spun yarn. The yarn packaging density is largely influenced by the yarn process parameters. Ring spinning technique is the most common and widely used for the production of yarn. This yarn subsequently utilized for the production of fabrics. Recently the research studies are more emphasis to create the living comfort condition. The yarn package density is a vital role to determine the feel, comfort, bulkiness and dyeing characteristics of the spun yarn. It is largely influenced by the yarn manufacturing techniques and raw material used. The effects of spinning process parameters on packing density will be helpful to predetermine the yarn comfort behaviour prior to the complete the fabric manufacturing process. Mechanical behaviour of the staple yarn depends on the fiber characteristics and the yarn structure i.e. the arrangement of the individual fiber on the cross-section of the yarn. The fiber distribution on the cross section of the yarn and packing density of yarn has been investigated. The study provides how the spinning process parameters affect the internal structure of ring spun yarn. The aim of the study is to improve the package density of the yarn to achieve dynamometric and comfort properties of yarn to attract a wide variety of customers. Yarn Packing Density represents inter-fiber distance and friction, hence controlling the mechanical and comfort properties of the yarn. The main objective of this study is to control the packing density of yarn during the spinning process. In this work the 100 percent cotton used as raw material and spun on a ring spinning machine. The 135 ring yarns samples have been produced from three different types of yarn counts include (Ne 8, 16 and 24) with nine different samples of identical counts were produced. The three different variables within the count sample are TPI and spindle speed and count. Yarn packing density was calculated by using the driven equation by the application of multiple regression models. The final result shows that packing density has directly related to the TPI, Spindle speed and count

Dynamic mechanical behavior of flocked layer composite materials

A custom designed dynamic mechanical apparatus was constructed to measure the tan(δ) (loss tangent) properties of Flocked (layer) Energy Absorbing Materials (FEAM). Flocked Impact Energy Absorbing (IEA) materials derive their dynamic mechanical impact absorbing properties from the compressional deformation (bending, buckling) and inter-fiber friction of nominally upright flocked fibers in the flock fiber composite assembly. The reported work summarizes the dynamic mechanical, low strain, linear viscoelastic tan(δ) properties of FEAM composite layer structures at frequencies from 25 to 100 Hz and a temperature range of 0 °C–50 °C. The effect of tan(δ) at various flock densities (fibers/mm2) was also measured. These studies were carried out to gain information and insight into the role that a material’s dynamic mechanical properties have on the overall IEA performance of sport (and military) apparel pad structures. Results show that the tan(δ) of FEAM materials increases as the measuring frequency and flocked layer’s flock density increase. Tan(δ)’s behavior at various temperatures (0 °C–50 °C) did not follow an expected trend; the highest tan(δ) value was observed to occur at room temperature. Nevertheless, the obtained tan(δ) information on these various FEAM configurations should provide some guidance in designing optimized FEAM sport (and military) pad IEA composites.

Tensile characterization of 3D nanostitched p-aramid/phenolic MWCNTs composites

The tensile properties of nanostitched and nanoprepreg three dimensional para-aramid/phenolic composites were studied. The tensile responses of para-aramid/phenolic composites showed three regions as initial inter-fiber friction, crimp exchange and yarn extension regions. Their tensile moduli in each region were defined. It was obtained that stitching and multiwall carbon nanotubes slightly increased the tensile strength of all stitched and stitched/nano composites. Tensile failure on all stitched structure showed brittle matrix and multiple ductile filament breakages in yarn after angular deformation in composite surface layers as well as local restricted delamination. Failure mechanism of carbon stitched composite was interestingly different compared to para-aramid stitched composite in where carbon stitching yarn was failed in the loop section. It was pulled out thickness direction of the composite and caused large local opening between layers.

In‐plane response of para‐aramid/phenolic nanostitched and nanoprepreg 3D composites under tensile loading

The tensile properties of nanostitched and nanoprepreg three dimensional para‐aramid/phenolic composites were studied. The tensile responses of para‐aramid/phenolic composites showed three regions as initial interfiber friction, crimp exchange, and yarn extension regions. Their tensile moduli in each region were defined. It was obtained that stitching and multiwall carbon nanotubes slightly increased the tensile strength of all stitched and stitched/nano composites. Tensile failure on all stitched structure showed brittle matrix and multiple ductile filament breakages in yarn after angular deformation in composite surface layers as well as local restricted delamination. Failure mechanism of carbon stitched composite was interestingly different compared to para‐aramid stitched composite in where carbon stitching yarn was failed in the loop section. It was pulled out thickness direction of the composite and caused large local opening between layers. POLYM. COMPOS., 40:1275–1286, 2019. © 2018 Society of Plastics Engineers

Filamentary structures that self-organize due to adhesion.

We study the self-organization of random collections of elastic filaments that interact adhesively. The evolution from an initial fully random quasi-two-dimensional state is controlled by filament elasticity, adhesion and interfilament friction, and excluded volume. Three outcomes are possible: the system may remain locked in the initial state, may organize into isolated fiber bundles, or may form a stable, connected network of bundles. The range of system parameters leading to each of these states is identified. The network of bundles is subisostatic and is stabilized by prestressed triangular features forming at bundle-to-bundle nodes, similar to the situation in foams. Interfiber friction promotes locking and expands the parametric range of nonevolving systems.

New experimental device for measuring the inter-fiber transversal friction

The mechanical behavior of fibrous structures depends on the inter-fiber friction. In the scientific literature, many researchers have studied this kind of friction, however all of them focused on the inter-fiber friction in only two directions: longitudinal-to-longitudinal (l-l) and longitudinal-to-transversal (l-t). Hence, there are no studies, up to now, focusing on transversal-to-transversal (t-t) direction. For this reason, an experimental device was developed to evaluate the transversal inter-fiber friction. The obtained results would allow characterizing and modelling this type of friction.

New Experimental Device for Measuring the Inter-Fiber Transversal Friction

The mechanical behavior of fibrous structures depends on the inter-fiber friction. In the scientific literature, many researchers have studied this kind of friction, however all of them focused on the interfiber friction in only two directions: longitudinal-to-longitudinal (l-l) and longitudinal-to-transversal (l-t). Hence, there are no studies, up to now, focusing on transversal-to-transversal (t-t) direction. For this reason, an experimental device was developed to evaluate the transversal inter-fiber friction. The obtained results would allow characterizing and modelling this type of friction.

Effect of the inter-fiber friction on fiber damage propagation and ballistic limit of 2-D woven fabrics under a fully confined boundary condition

This paper investigates the effect of the inter-fiber friction coefficient on fabric ballistic performance. Firstly, dynamic stress responses within a fabric due to first fiber failure are analyzed. Relations between inter-fiber friction and progressive fiber failure are assessed. Then, ballistic perforation processes of Kevlar KM2 fabrics are simulated using a fiber level micro-approach, the digital element approach (DEA). In this model, each yarn is discretized into many fibers and each fiber is divided into many rod elements. A Monte Carlo process is utilized to assign a unique strength to each element following a bimodal Weibull distribution function. DEA is used to simulate the ballistic perforation processes. A comparative investigation using a broad range of inter-fiber friction coefficients are conducted. Relations of ballistic limits and inter-fiber friction coefficients are presented. Simulation results show that ballistic limit improves as the inter-fiber friction coefficient increases up to a critical value. Beyond that point, ballistic strength decreases slightly as the inter-fiber friction coefficient increases. The inter-fiber friction also changes the ballistic perforation mechanisms.

Wide‐Range Tunable Dynamic Property of Carbon‐Nanotube‐Based Fibers

A carbon nanotube (CNT) fiber is formed by assembling millions of individual tubes. The assembly feature provides the fiber with rich interface structures and thus various ways of energy dissipation, as reflected by the nonzero loss tangent (>0.028–0.045) at low vibration frequencies. A fiber containing entangled CNTs possesses higher loss tangents than a fiber spun from aligned CNTs. Liquid densification and polymer infiltration, the two common ways to increase the interfacial friction and thus the fiber's tensile strength and modulus, are found to efficiently reduce the damping coefficient. This is because the sliding tendency between CNT bundles can also be well suppressed by a high packing density and the formation of covalent polymer cross‐links within the fiber. The CNT/bismaleimide composite fiber exhibits the smallest loss tangent, nearly the same as that of carbon fibers. At a higher level of the assembly structure, namely a multi‐ply CNT yarn, the interfiber friction and sliding tendency obviously influence the yarn's damping performance, and the loss tangent can be tuned within a wide range, similar to carbon fibers, nylon yarns, or cotton yarns. The wide‐range tunable dynamic properties allow new applications ranging from high quality factor materials to dissipative systems.

Identifying the breaks of wool fibers based on the waveform analysis of acoustic emission

Acoustic emission (AE) of fiber break is the sound waves reflecting the stress waves of material during rupturing. It can be employed to evaluate the tensile properties of single fiber during the fiber-bundle tensile test. The key to this technique is to identify AEs of fibers at the break point accurately. However, the severe interference introduced by the background noise and the inter-fiber friction is inevitable. In this paper, a filtering method based on the wavelet de-noising is used to remove the background noise. In order to identify the fiber-broken AEs, a combined parameter that characterizes the amplitude and the density fluctuation along the time axis is proposed. Multiple test results indicate that this parameter can be used to identify wool fiber-broken AEs with accuracy rates higher than 95%.

Dissolution of serpentine fibers under acidic flotation conditions reduces inter-fiber friction and alleviates impact of pulp rheological behavior on Ni ore beneficiation

In beneficiation of Ni ores containing fibrous serpentines in large amounts, flotation pulps exhibit high viscosity, impacting Ni recovery and grade. Fibers entangle in pulp with formation of inter-fiber networks made up of micro floccs that spread across the pulp volume. These networks are sturdy and difficult to disentangle as inter-fiber frictional forces which are the predominant among the inter-particle forces restrict sliding of fibers at the inter-fiber contact points. The net force from numerous contact points in a network is significant. Therefore, the pulp yield stress value, a measure of net inter-particle forces, is considerably higher than that is typical in flotation. According to this study, the pulp yield stress decreases upon addition of H2SO4 to the pulp, which also correlates to the extent of serpentine dissolution. The continuation of fiber dissolution is necessary to maintain the inter-fiber frictional forces to a lower value, and serves as an inter-fiber lubricant for loosening of these networks. Thus, acidic conditions alleviate the impact of pulp rheological behavior on Ni ore beneficiation.

Effect of Plasma Treatment on Air and Water-Vapor Permeability of Bamboo Knitted Fabric

In this paper, the effects of oxygen and atmospheric plasma on air and water-vapor permeability properties of single jersey bamboo fabric have been investigated. The changes in these properties are believed to be related closely to the inter-fiber and inter-yarn friction force induced by the plasma treatments. The outcomes showed that the water-vapor permeability increased, although the air permeability decreased along with the plasma treatments. The SEM images clearly showed that the plasma modified the fiber surface outwardly. The results showed that the atmospheric plasma has an etching effect and increases the functionality of a bamboo surface, which is evident from SEM and FTIR–ATR analysis. These results reveal that atmospheric pressure plasma treatment is an effective method to improve the performance of bamboo fabric. Statistical analysis also indicates that the results are significant for air permeability and water-vapor permeability of the plasma-treated bamboo fabric.