Single Yarn Pull-out Tests Research Articles

Effects of different oxidation systems on the interfacial properties of bamboo fiber/epoxy resin composites

The objective of this study was to improve the interfacial properties of bamboo fabric (BF)/epoxy (EP) composites and thus enhance their mechanical properties. BF was treated with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidation system and N-hydroxyphthalimide (NHPI) oxidation system, respectively, to obtain BFO- T and BFO- N oxidation products with different surface morphologies. The effects of different oxidation treatments on the tensile strength (σc) and elongation at break (εc) of the composites were evaluated. Compared with the untreated BF/EP samples, BFO- T/EP showed a 56.9% increase in σc with a non-significant change in the increase in εc. BFO- N/EP showed a 30.1% increase in σc, but the improvement of εc reached 473.7%. The results of single-yarn pull-out tests and atomic force microscopy indicated that the proper size of grooves may be the key to improve the strength of the two-phase interface. The larger size of the grooves, the easier it is for the resin to infiltrate and fill the voids, thus forming occlusal structures that strengthen the interfacial bonding. Small-sized grooves, on the other hand, are not conducive to resin impregnation and therefore voids at the two-phase interface, thus hindering load transfer.

Gradient shear thickening gel/Kevlar fabric multi-layer armor with enhanced impact attenuation property

Realizing highly-efficient energy absorbing performance in soft body armor, yet with lightweight feature, has always been an eternal subject for personal protective equipment. This work reports a gradient-stacked shear thickening gel (STG)/Kevlar (GS-STG/Kevlar) fabric multi-layer armor with both lightweight feature and excellent impact attenuation performance. Firstly, STG is prepared by mechanical blending and chemical crosslinking and then coated on Kevlar fabrics, and afterwards STG-coated multi-layer Kevlar fabrics with gradient STG distribution in the thickness direction are fabricated. Single yarn pull-out test demonstrates that the friction between Kevlar yarns is greatly increased after STG treatment. Moreover, tribological testing also indicates that the friction coefficient of Kevlar fabrics is improved by coating STG. Furthermore, low- and high-speed impact experiments are conducted, and the results demonstrate that the GS-STG/Kevlar fabric composite exhibits the best impact attenuation property when compared with multilayered Kevlar fabrics and uniformly stacked STG/Kevlar fabrics under the same impact conditions. The increased friction and stiffening effect by STG, and the gradient stacking strategy are responsible for the great improvement in the impact attenuation performance of GS-STG/Kevlar fabric multi-layer armors. This study provides an effective methodology for achieving soft body armors with lightweight and high impact attenuation properties for personal impact protection.

Experimental Investigation of Beams Reinforced with Carbon 2D-Netzgitterträger Reinforcement

The increasing popularity of carbon-reinforced concrete (CRC) is attributed to its exceptional tensile properties, low density, no corrosion phenomenon, and remarkable flexibility, allowing it to be easily shaped into various forms. However, there is a pressing need to explore this innovative and sustainable alternative to traditional steel reinforcement. This motivates research and investigation of the feasibility of using a special 2D Netzgitterträger (NetzGT) reinforcement system, featuring a net-shaped fabricated textile made of multiple diagonally offset rovings with overlapping edge strands, as a viable alternative to traditional steel reinforcement in concrete beams. This 2D NetzGT reinforcement system has also been transformed into a 3D configuration for the development of a hollow core slab system. It is manufactured from carbon rovings with three different diagonal angles of 50°, 60°, and 70°. Laboratory experiments were conducted to assess the mechanical behavior of beams reinforced with the 2D NetzGT reinforcement. Tensile tests on strands were also performed with an increasing number of overlapped rovings to analyze their tensile strength. Additionally, single yarn pull-out tests were also conducted to examine the influence of the roving angle on the bond strength between the carbon textile roving and the concrete matrix.

Investigating the effect of aligned Ag nanorods on para-aramid woven fabric and anisotropy in inter-yarn friction

Inter yarn friction, measured in terms of yarn pull-out force, is a major mechanism of energy absorption in soft body armor. Increasing inter-yarn friction of para-aramid fabric to improve ballistic performance without adding weight is challenging. This work reports the fabrication of aligned Ag nanorods (AgNRs) on the para-aramid (Kevlar) fabric surface using the glancing angle deposition technique. A single yarn pull-out test examines Kevlar fabric treatment. The AgNRs-coated para-aramid fabric retains its flexibility and weight while increasing yarn pull-out force by 130%. Anisotropy in inter-yarn friction depends on the yarn's sliding direction relative to Ag nanorod tilt direction, indicating direction-dependent yarn pull-out force. The periodic character of pull-out response post-peak force is replicated by modeling the yarn pull-out phenomenon by incorporating a mesoscale level numerical model of woven fabric. The numerical model confirms the experimental results that formation of nanorods significantly increases inter-yarn friction and pull-out force.

Micromechanical modeling and experimental analysis of yarn separation type sewing damage on continuous filament fabrics

Fabrics with weaves of low interlacing density and smooth yarns such as continuous cuprammonium filaments are often susceptible to sewing damage of cracks perpendicular to the sewing line, seriously influencing the aesthetics of the finished garment. To understand how the important factors such as yarn modulus, yarn bending stiffness, sewing needle radius, yarn-on yarn-friction, fabric counts and fabric weaves act on the crack length of such a fabric, a micromechanical model is proposed, and the experimental results are compared with the theoretical prediction. Single yarn pull-out tests and single yarn axial compression tests are performed to estimate yarn-on-yarn friction and yarn bending stiffness, respectively. The model indicates that the sewing crack length is positively proportional to the yarn tensile modulus, yarn bending stiffness and the needle radius and is negatively proportional to the fabric count and the inter-yarn friction. The model predicted crack lengths are within the range of the experimental results in warp direction while the predicted value is substantially larger than the observed crack lengths in weft direction due to the high compressibility of the weft yarn, which decreased yarn tension, bending stiffness and increased yarn cover power. For a given fabric, increasing yarn-on-yarn friction and raising yarn compressibility is an effective way to control the crack lengths.

The influence of carbon nanotube addition on the shear-thickening performance of suspensions

The shear thickening fluid as a protective material has received increasing attention, and its impact resistance and its rheological properties are controllable by integrating various kinds of additives to a single phase shear thickening fluid. In this paper, the rheological properties of shear thickening fluids with 26 wt.% fume silica, PEG200 and different mass fraction of multi-walled carbon nano-tubes are investigated, and the effect of temperature from -5?C to 55?C on steady state rheological properties of 1.0 wt.% multi-walled carbon nanotubes reinforced shear thickening fluids is studied. Finally a single yarn pull-out test is conducted to examine the influence of multi-shear thickening fluid on the shear strength and inter-yarn friction of fabrics. The results show that the addition of multi-walled carbon nanotubes can improve significantly the viscosity and shear thickening efficiency.

Internal friction properties of carboxylated cellulose nanofibers (CNF-C) modified aramid woven fabrics

The internal friction properties of the aramid woven fabrics modified by carboxylated cellulose nanofibers (CNF-C) were studied, in order to better investigate the effect of CNF-C on the internal friction properties of the aramid woven fabrics, the yarn pull-out force of the modified aramid fabrics were tested by single yarn pull-out test. The chemical structure and surface morphology of the aramid fibers were characterized by Fourier Transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the strong hydrogen bond between CNF-C and aramid fiber and the dipole–dipole interaction between the polar groups of the fiber (such as –NH, –C = O) and hydroxyl groups are the bond mechanism. Compared with the untreated fabrics, the yarn pull-out force and fiber surface roughness of the CNF-C modified aramid fabrics are significantly improved. When the impregnation time is 0.5 h and the CNF-C concentration is 1 wt%, the yarn pull-out force reaches the maximum of 13.3 N, which is increased by 133.3% compared with the untreated aramid fabrics. The internal friction properties of the aramid woven fabrics are obviously increased by modification.

Shear deformation and energy absorption analysis of flexible fabric in yarn pullout test

The friction level between yarns significantly affects the ballistic performance of flexible fabrics. In this study, single yarn pullout tests of Kevlar 49 plain weave fabric under different preloads and different yarn pullout rates were carried out. The in-plane shear deformation of the fabric was measured using a digital image correlation method to determine the global shear strain and shear modulus. In addition, based on the stick-slip phenomenon in the process of yarn pulling, a bilinear stress transfer model between yarns was developed. The energy absorption mechanism and interface shear stiffness were theoretically analyzed, and the yarn interface parameters were inversely obtained from the experimental data. The analytical results of the proposed stress transfer model are consistent with the experimental load-displacement curve.

The Impact-Tensile Behavior of Cementitious Composites Reinforced with Carbon Textile and Short Polymer Fibers

The paper at hand focuses on the tensile behavior of ductile cementitious composites reinforced with short, randomly distributed, polymer fibers and a continuous carbon textile under quasi-static and impact loading. Strain-hardening cement-based composites (SHCCs) made of high strength fine-grained matrix with the addition of a 2% volume fraction of 6 mm-long ultra-high molecular weight polyethylene (UHMWPE) fibers and as-spun poly(p-phenylene-2,6-benzobisoxazole) (PBO-AS) fibers, respectively, were reinforced with one layer of carbon textile, which corresponds to a 0.68% volume fraction. The same fine-grained matrix reinforced with carbon textile only served as the reference material. The synergetic action of the two reinforcement types was investigated in uniaxial tension tests on composite specimens, as well as by means of single-yarn pullout tests at displacement rates of 0.05 mm/s in a hydraulic testing machine, and 8 m/s in a tensile split Hopkinson bar. The specimen’s deformations, the formation of cracks, and the fracture processes were monitored optically and subsequently evaluated using digital image correlation (DIC).

On the characterization and modelling of high-performance para-aramid fabrics

In this work, seven different types of fabrics based on para-aramid yarns with different interlacing geometries and reinforcement polymer matrix have been characterised and compared from yarn level to weave level. Mechanical properties such as maximum stress, failure strain, and elastic modulus have been obtained from uniaxial tensile tests, while the inter-yarn friction coefficients (static and kinetic) have been obtained by a combination of single yarn pull-out tests and an analytical model. Results show that mechanical properties are quite similar at yarn level but different at fabric level. Thus, the geometry, orientation and section of the yarn play an important role in the mechanical properties of the fabric. As an application of these results, a mesoscopic three-dimensional numerical model has been developed, and simulations of ballistic impact test have been carried out validating the model with experimental tests.

Carbon Fibre Reinforced Concrete: Dependency of Bond Strength on T<sub>g</sub> of Yarn Impregnating Polymer

In this paper, a method for the evaluation of the influence of different polymer suspensions and environmental conditions on adhesion between an impregnated carbon fibre heavy tow and concrete for reinforcement will be proposed. For this purpose, the impregnation material itself was investigated as a polymer film before and after incubation in water and aqueous suspensions, such as NaOH and a cementitious solution, in terms of its thermal properties, swelling behaviour and morphology. Thin polymer films were manufactured and subsequently investigated with quantification of the swelling for 28 d by thermal and scanning electron microscope analysis. The effect of pull-out shear stress was evaluated to investigate parameters such as high temperature and moisture on adhesion to concrete. Contact angle measurements were used to determine the surface energy of the polymer films. All incubated polymer films yielded a change in both surface morphology and specific residues on the polymer film surface, e.g. in the form of calcium carbonate, but no change in glass-transition temperature. A high correlation between glass-transition temperature and measured shear stress was shown during single yarn pull-out tests. Furthermore, the water treatment of pull-out samples strengthened the influence for the glass-transition temperature during the adhesion test. No influence of the surface energy of the used polymer impregnation for carbon fibres on the pull-out test was detected.

Experimental Study on Yarn Pullout Test of STF Modified Fabric

Shear thickening fluid (STF) solution with SiO2 as dispersing phase and ethylene glycol as dispersing medium was prepared by ball milling, Kevlar49 plain woven fabrics impregnated with SFT were prepared. The impact resistance and shear deformation of the STF modified fabrics were studied by single-yarn pull-out tests and digital image correlation (DIC). The experimental results show that a dynamic slippage of yarns makes the STF attached to the yarn surface appear shear thickening effect, so the sliding friction between the yarn is higher than the static friction due to the increased viscosity. Therefore, the bigger pull-out force of the STF-fabrics increases the energy absorption capacity of the fabrics. The DIC results show that the maximum shearing angle and the residual shearing angle of the STF modified fabrics are larger than those of the pure fabrics, indicating that the STF will increase the friction between the yarns without affecting the fabric flexibility.

The effect of graphene on the yarn pull-out force and ballistic performance of Kevlar fabrics impregnated with shear thickening fluids

The ballistic performance of Kevlar fabric impregnated with different shear thickening fluids (STFs) were investigated at various impact velocities. The SiO2 nanoparticle based STFs were reinforced with graphene and showed a significant increase in viscosity and shear thickening efficiency compared to pure STF. Ballistic experiments were performed on fabric treated by different STFs, and different failure modes including yarn slipping, extraction, and breakage in shear failure were obtained. To better understand how different STFs affect ballistic performance, single yarn pull-out tests were also carried out to examine the shear strength and friction between the interlocking yarns of fabric treated with STF. The results showed that STF reinforced with graphene is better at preventing the yarns from slipping, and the single yarn pull-out force is almost 5 times more than pure STF. Moreover, reinforced STF also has a significant influence on the ballistic limit and energy absorption of Kevlar fabrics. And the increased amplitude of energy absorption is almost 20% more than the pure STF/Kevlar load case. Combining with the energy absorption and different failure modes, the effect of STF on the failure mechanism of neat/treated fabric was also discussed.

Experimental study of yarn friction slip and fabric shear deformation in yarn pull-out test

Single yarn pull-out test is a model experiment method to research the mechanical properties of fabric under impact. This study aims to understand the yarn pull-out mechanism and fabric shear deformation behavior of Kevlar 49 plain fabric by using the single yarn pull-out test combined with the digital image correlation method. The load-displacement curve contains typical physical phenomena such as crimp extension, crimp swap, frictional slip of yarn, and fabric deformation behavior. In the static friction stage, the pull-out load increased nonlinearly with the displacement, and the crimp extension of the pulled warp yarn occurred gradually. In the kinetic friction stage, the load decreased undulately until the warp was pulled out. Moreover, the fabric shear deformation sharply increased in the static friction stage, then decreased slowly during the kinetic friction stage. It was found that fabric shear deformation was still apparent after the yarn was completely pulled out.

Experimental and numerical analysis of high and low velocity impacts against neat and shear thickening fluid (STF) impregnated weave fabrics

This investigation aims to study the efficiency of STF impregnated plain-weave fabric made of Kevlar under high and low velocity impact conditions. The shear thickening fluid (STF) was prepared by ultrasound irradiation of silica nanoparticles (diameter ≈30 nm) dispersed in liquid polyethylene glycol polymer. STF impregnation effect was determined from single yarn pull-out test and penetration at low velocity using drop weight machine equipped with hemi-spherical penetrator and dynamic force sensor. Force-displacement curves of neat and impregnated Kevlar were analysed and compared. Also, the STF impregnation effect on Kevlar multilayers was analysed from high velocity impact tests using 9mm FMJ bullet at 390 m/s. After impact, Back face deformation (BFD) of neat and impregnated Kevlar layers were measured and compared. Results showed that STF impregnated fabrics have better energy absorption and penetration resistance as compared to neat fabrics without affecting the fabric flexibility. When relative yarn translations are restricted (e.g. at very high levels of friction), windowing and yarn pull-out cannot occur, and the fibres engaged with the projectile fail in tension that leads to fabric penetration. Microscopy of these fabrics after testing have shown pitting and damage to the Kevlar filaments caused by the hard silica particles used in the STF. Mesoscopic 3D Finite Element models were developed using explicit LS-DYNA hydrocode to account for STF impregnation by employing the experimental results of yarn pull-out tests, low and high velocity impacts. It was found that friction between fibers and yarns increase the dissipation of energy upon impact by restricting fiber mobility, increasing the energy required for relative yarn translations and transferring the impact energy to a larger number of fibers.

Study on Single-yarn Pullout Test of Ballistic Resistant Fabric under Different Preloads

During bullet penetrating fabric, the pull-out force of yarn in fabric is related to the impact resistance of fabric when the yarn is pulled out from the fabric. The complex uncrimping and friction slip behavior occur during the yarn pullout process, which is critical to learn the impact resistance of fabric. Based on digital image correlation technique, the deformation behavior of Kevlar 49 fabric subjected to preload during the single-yarn pullout process was studied in this paper. The pullout force and displacement curve shows a straight rise and an oscillated decrease. In the linear rise stage, the yarn uncrimping causes a static friction effect. The maximum of the pullout force is not linearly increased with the preload. In the oscillating descending stage, the local descent of the pullout force indicates that the yarn end is gradually withdrawn from the fabric, and the local rise indicates that the yarn end moves to the next weft/warp interaction until the yarn is completely pulled out. The shear deformation of fabric corresponds to the single-yarn pullout process.

Single-yarn pull-out test in neat, solvent-treated and shear-thickening fluid-impregnated Kevlar® KM2 fabric

PurposeIn order to help explain experimental findings related to the stabbing- and ballistic-penetration resistance of flexible body-armor, single-yarn pull-out tests, involving specially prepared fabric-type test coupons, are often carried out. The purpose of this paper is to develop a finite-element-based computational framework for the simulation of the single-yarn pull-out test, and applied to the case of Kevlar® KM2 fabric.Design/methodology/approachThree conditions of the fabric are considered: neat, i.e, as-woven; polyethylene glycol (PEG)-infiltrated; and shear-thickening fluid (STF)-infiltrated. Due to differences in the three conditions of the fabric, the computational framework had to utilize three different finite-element formulations: standard Lagrangian formulation for the neat fabric; combined Eulerian-Lagrangian formulation for the PEG-infiltrated fabric (an Eulerian subdomain had to be used to treat the PEG solvent/dispersant); and combined continuum Lagrangian/discrete-particle formulation for the STF-infiltrated fabric (to account for the interactions of the particles suspended in PEG, which give rise to the STF character of the suspension, with the yarns, the particles had to be treated explicitly).FindingsThe results obtained for the single-yarn pull-out virtual tests are compared with the authors’ experimental counterparts, and a reasonably good agreement is obtained, for all three conditions of the fabric.Originality/valueTo the authors’ knowledge, the present work represents the first attempt to simulate single-yarn pull-out tests of Kevlar® KM2 fabric.

Effect of Fabric Weave on Stick-Slip Properties of Woven Fabrics

Abstract The aim of this study was to understand the stick-slip properties of dry polyester plain, ribs and satin woven fabric weaves. It was found that the amount of stick-slip force was related to the number of interlacement points in the fabric, whereas the amount of accumulative retraction force was related to fabric structural response. Stick-slip force and accumulative retraction force depend on fabric weave, fabric density, the number of pulled ends in the fabric and fabric sample dimensions. The weft directional single and multiple yarn stick-slip and accumulative retraction forces of dry plain fabrics in fabric edge and centre regions were higher than those in the satin fabric due to fabric weave. In addition, the warp directional single and multiple yarn stick-slip and accumulative retraction forces in the meso-cell-1 to the meso-cell-6 of dry wide and long satin fabric in fabric edge were higher than those in the weft direction due to fabric density. Stick-slip and accumulative retraction forces of polyester fabric in the multiple yarn pull-out test were higher than those of the single yarn pull-out test.

Stick-slip properties of single and multiple yarn pull-out in dry and softening treated polyester satin woven fabrics in boundary region

Purpose – The aim of this study was to understand the stick-slip properties of single and multiple yarn pull-out in dry and treated polyester satin woven fabric in boundary regions. Design/methodology/approach – Polyester satin pattern woven fabric was used to conduct the pull-out tests in order to examining the kinetic region of the force-displacement curve. Data generated from this research help the authors to obtain stick-slip force and accumulative retraction force. Findings – It was found that stick-slip force and accumulative retraction force depend on the number of pulled ends in the fabric, fabric sample dimensions and softening treatments. Stick-slip forces of polyester satin fabric in the multiple yarn pull-out test were higher than those of the single yarn pull-out test. Stick-slip force in single and multiple yarn pull-out tests in the dry polyester satin fabric was generally higher than those of the softening treated polyester satin fabric. In addition, the warp directional single and multiple yarn stick-slip and accumulative retraction forces in the dry and softening treated polyester fabrics were generally higher than those in the weft direction in the fabric edges due to fabric density. On the other hand, the amount of stick-slip force was related to the number of interlacement points in the fabric, whereas the amount of accumulative retraction force was related to fabric structural response. Originality/value – The mechanism of stick-slip and accumulative retraction force of dry-treated polyester satin pattern woven fabrics were explained. This research could be valuable for development of multifunctional fabrics in technical textiles and ballistic.

Characterizations of stick-slip stage of yarn pull-out in dry and softening treated polyester plain woven fabric

The aim of this study was to understand the stick-slip properties of polyester plain woven fabric. For this reason, pull-out test was conducted on dry and softening treated polyester woven fabrics. It was found that stick-slip force and accumulative retraction force depend on the number of pulled ends in the fabric, fabric sample dimensions and softening treatments. Stick-slip forces of polyester fabric in the multiple yarn pull-out test were higher than those of the single yarn pull-out test. Stick-slip force in single and multiple yarn pull-out tests in the dry polyester plain fabric were generally higher than those of the softening treated polyester plain fabric. On the other hand, the amount of stick-slip force was related to the number of interlacement points in the fabric whereas the amount of accumulative retraction force was related to fabric structural response.