High-tenacity Fibers Research Articles

The Mechanical Characteristics of Enhanced Bendable Concrete By Polyvinyl Alcohol Fibers

Abstract Engineered Cementitious Composites (ECC), which are alternatively referred to as Bendable Concrete, is a class of Ultra-ductile cementitious composites characterized by their remarkable ductility and polyvinyl alcohol fiber (PVA) fiber reinforcing. These composites are designed to regulate cracks width effectively. This study investigates the influence of matrix flowability, fiber mixing technique, and curing conditions on the mechanical characteristics of Bendable Concrete utilizing high-tenacity (PVA) fibers. This study examined the compressive strength of Bendable concrete, which ranged from 60 to 70 MPa, with a strain exceeding 3%. To regulate the flowability of the matrix, high range water reducing admixture (HRWRA) was added to a matrix with a weight ratio of silica fume was 10% by weight of cement, a weight ratio of water to cementitious material of 0.3, also polyvinyl alcohol acetate solution (PVAS). The primary parameter under investigation in this study is the changing volume fraction dose of (PVA) fiber, while the remaining materials of the combination were held constant. Four different (PVA) fiber percentages (0.5, 1.0, 1.5, and 2.0)% were adopted by volume of cement. Three (cubes, cylinders, and prisms) were fabricated and cast from each mixture and tested at the ages (7, 28, and 90) days for investigated (compressive, splitting tensile, and Modulus of Rupture) strength, respectively. The results of the tests demonstrated that the proportion of fiber substantially affects the strengths, where both the Compressive strength and Splitting tensile strength were increased with the increment of fiber content until 1% of (PVA) fiber . In comparison, the higher Modulus of Rupture was abtained at 2% (PVA) fiber.

Extraction and Characterization of Dracaena fragrans Leaf Fibre

Textile industries have recently become prevalent environmental pollutants as a result of natural inconsistencies and resource scarcity. As a remedy, using natural fibres for textile production is strongly encouraged. Dracaena fragrans is an Ethiopian plant with lingo-cellulosic fibres that can be used for textile applications. This study focuses on the extraction and characterization of Ethiopian Dracaena fragrans leaf fibre and evaluates its application in the textile industry. For fibre extraction, water, 10% NaOH, 1% H2O2, EDTA di (with 1.5% and 1%, respectively), 0.2% pectinase (presoak), 0.05% alpha-amylase (for 24 hours, 18 hours, and 12 hours retting), and 5% gel retting methods were utilized. Subsequently, the properties of extracted fibre, mainly fibre length, fineness, tenacity, elongation at break, and degree of whiteness, were evaluated. Longer fibres (46 ± 0.74 cm) were obtained by pectinase retting. Comparatively, finer (11.22 ± 0.64 dtex) fibres were obtained by the water retting method. Fibre with the best tenacity (54.51 ± 0.61, 53.54 ± 0.60, and 52.53 ± 0.61) was obtained by EDTA di (1%), 5% gel retting and water retting methods respectively. On the other hand, higher elongation at break (7.28 ± 0.78%) was obtained by 0.05% alpha-amylase retting with a retting time of 24 hours. And finally, the best fibre whiteness (w* = 71) was obtained by 1% H2O2 retting. Long fibres obtained by the pectinase retting method can be used for the production of packaging sacks and hessians. Fibres obtained by the water retting method can be used for the production of linen fabrics such as lace and sheeting. On the other hand, high-tenacity fibres extracted using (1%) EDTA di retting and 5% gel retting methods can be used for the production of cloths, bags, and shoes. Finally, a highly extensible fibre extracted using α-amylase (24 hours retting) can be used for the production of sports clothes.

Disclosing the fatigue deformation mechanisms of different types of poly (ethylene terephthalate) industrial fibers on the base of the multiscale structural evolutions

AbstractThe fatigue behavior of poly (ethylene terephthalate) industrial fibers is a key issue in their long‐term service for engineering applications. To have a comprehensive understanding of the fatigue behavior, the high‐tenacity (HT) and low‐shrinkage (LS) PET fibers were selected to analyze the room temperature dynamic fatigue properties with different stress. Various techniques such as WAXD/SAXS and FTIR were employed to study the multiscale structure changes to disclose the fatigue mechanisms. Although the crystalline structure including orientation and crystallinity did not change, the amorphous structures varied with fatigue stress. The HT fiber exhibited a higher fatigue recovery ratio. The slight increase in amorphous orientation, and amorphous thickness was attributed to the oriented coiled molecular chains during tensile fatigue stress. In contrast, the LS fiber experienced plastic fatigue deformation with a lower recovery ratio. The molecular chains in the large amorphous domain are easily extended and oriented under tensile loading, increasing amorphous orientation and lamellar thickness. The fatigue mechanism for the LS fiber involved the conformation transition from gauche to trans conformers and a higher proportion of irreversible amorphous regions were formed. It is indicated that developing industrial filaments with small amorphous orientation and content is crucial to improving their fatigue resistance.

Copolymerization-Regulated Hydrogen Bonds: A New Routine for High-Strength Copolyamide 6/66 Fibers.

Hydrogen bond interactions are important for nylon fibers, which improve its mechanical properties and crystallization behavior, while hindering the movement and orientation of the molecular chain during the drawn process. In this study, hexamethylene adipamide was used as the second monomer in copolymerization with ε-caprolactam to obtain copolyamide 6/66 (CoPA), and high-tenacity fibers with a maximum value up to 8.0 cN/dtex were achieved by a multi-step drawn and thermal setting process. Results show that the hexamethylene–adipamide ratio affected the draw ratio (DR) of the as-spun fiber, on the tenacity of final high-performance fiber, and on crystalline. Both DR and tenacity showed evident increases with the hexamethylene–adipamide ratio up to 6% in CoPA and then changed smoothly. However, XRD and DSC results illustrate a decreased tendency with regard to crystallinity. The attenuated in-site total reflection Fourier transform infrared (ATR-FTIR) spectra were used to study the hydrogen bond interaction between the C=O group and N–H group and the crystal form of the fiber. Results show that the copolymerization destroyed the regularity of the main chain of CoPA and reduces the interaction of interstrand hydrogen bonds, facilitating the formation of the γ-crystalline form in as-spun fibers, fulfilling the transition from the γ to α crystalline form during the fiber-drawing step because of the release of the C=O group and N–H group from the hydrogen bond interaction at an elevated temperature close to the molten temperature of CoPA, and then reforming during the thermal-setting step which soiled the crystalline and improved the tenacity of the fiber. The copolymerization with a homologous monomer regulates the hydrogen bond interaction, fulfills the high drawn ratio and high tenacity fiber, and provides a new route for high-performance fiber preparation using traditional fiber formation of polymers.

Ballistic impact performance of UHMWP fabric impregnated with shear thickening fluid nanocomposite

In the present study, an attempt is made to improve the ballistic performance of unidirectional (UD) ultra-high molecular weight polyethylene (UHMWP) fabrics through shear thickening fluid (STF) impregnation. Impact tests in the range of 250–700 m/s were conducted using an aero-ballistic range. It was observed that the ballistic limit (V50) and the energy absorption of STF treated UD-UHMWP fabrics can be improved up to 5% and 13% respectively, corresponding to their neat ones. Increased energy absorption of STF treated fabric is attributed to the enhancement in the friction between layers of the STF-UHMWP fabric and the shear thickening effect. The effect of sample thickness of STF treated panels on the energy absorption, failure mechanism, and back face signature (BFS) is evaluated and compared with their neat counterparts. The damage was localized in the thinner panels (5 and 10 layers), and the layers were perforated through shear plugging near the impact region. The failure mode of thicker panels (20 and 30 layers) is accompanied by the tensile fracture of high tenacity fibres. It is concluded that the STF impregnation improves the ballistic resistance of UD-UHMWP fabric without affecting the flexibility and adding weight penalty.

Article Review on Vectran-Super Fiber from Thermotropic Crystals of Rigid-Rod Polymer

According to the economic and environmental perspective, multifilament Vectran, yarn spun from liquid crystal polymer, is important because of its quite simple processing during spinning in a wide range of injection moulding, extrusion moulding, and melt spinning. Vectran fiber is an aromatic polyester spun from a liquid crystal polymer in a melt extrusion process. This process orients the molecules along the fiber axis, resulting in a high tenacity fiber, and Vectran melts at 330°C. Heat treatment can improve and vary the tensile strength of Vectran fiber. On average, tensile strength for Vectran is 26 grams/denier (grouped as a high tenacity grade) and the strength of the fiber is maintained after several flexing and bending actions. Abrasion resistance of Vectran is even higher than a similarly sized aramid yarn. In addition, the original dimensions are maintained under variance of temperature with negligible creep and shrinkage. Vectran fiber, characterized by its golden color, high strength and modulus, thermal stability at high temperatures, low creep, and good chemical stability, can be used in many various industries starting from ropes and cables to profound sea survey and military products.

Structural evolutions during creep deformation of polyester industrial fiber via in situ synchrotron small-angle X-ray scattering/wide-angle X-ray scattering

This paper aims to identify the creep mechanisms of high tenacity (HT) polyester industrial fiber under different loads. In-situ synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) tests were conducted on a 1000 D HT fiber during the creep and creep recovery process with a low load (15 N) and a medium load (50 N) as well as creep rupture process with a high load (60 N). The measured creep strain-time curves comprised tensile zone (I), creep deformation zone (II) and creep recovery/rupture zone (III). The SAXS indicated that the macroscopic initial creep strain in zone I and creep deformations in zone II were attributed to conformation transition from gauche to trans in amorphous region, increasing the amorphous orientation and long period. Irreversible portion of conformation changes accounts for the small unrecoverable plastic creep strain after removing 15 N load in zone III. The initial creep strain in zone I and creep deformations in zone II of the 50 N creep process were bigger than the microscopic long period strain, because amorphous layers had conformational transformation and microfibril slippage which also produced a higher unrecoverable plastic creep strain in zone III. The long period increased significantly at the beginning of rupture zone with 60 N due to fragmentation of amorphous tie molecular. The disappearance of lamellar peaks at the end of rupture zone implied destruction of periodic lamellar structures, for the entire breakage of amorphous chains. The WAXS suggested that the crystal structure was stable under the creep loads.

A penetration model for semi-infinite composite targets

A penetration model for composites reinforced with high tenacity fibres like ultra-high molecular weight polyethylene (UHMW-PE) is proposed based on the modified Bernoulli theory typically used for metallic targets. The model describes penetration by tensile failure of the composite material through compression loading in an infinitely thick target and includes consideration for projectile deformation. The predicted projectile velocity and axial interface loads shows good agreement with numerical simulations for a deforming and rigid projectile condition against two grades of UHMW-PE composite. The model can also be used to predict transient projectile velocity and interface loads during the first phase of penetration (which acts over most of the penetration event) for a target of finite thickness. It was shown that transition to bulging occurs upon the arrival of the rarefaction wave, generated from the back of an unsupported target, at the projectile-target interface. The stress relief can lead to a change in penetration mode when the magnitude of release is sufficient to reduce the load at the interface below that of the target strength. This change in mode occurs late in the penetration event, and the model developed in this work is demonstrated to be valid up to this point.

High strain rate characterization of shear thickening fluids using Split Hopkinson Pressure Bar technique

Shear thickening fluids (STFs) are a special class of field responsive fluids which exhibit change of phase from liquid to solid when subjected to imposed shear. This remarkable characteristic of STFs has led to their application in soft body armor technologies, leading the development of concept of Liquid Body Armors (LBAs). LBAs extensively rely upon the symbiotic relationship between STF and high strength FRP (Fiber Reinforced Polymer) composites comprising of high tenacity fibers such as Kevlar, UHMWPE (Ultra High Molecular Weight Poly Ethylene) etc. Although in the past, STFs have been widely characterized by rheometers at low strain rates (≤103 s−1), but in actual practical scenarios, body armours encounter much higher strain rates (of the order of 105–107 s−1) under a ballistic impact. The main objective of this study is to capture the dynamics of STFs at such high strain rates by employing Split Hopkinson Pressure Bar (SHPB) technique. The STF sample was synthesized by dispersing 67.5wt.% of 100nm silica powder in Poly Propylene Glycol (PPG) and ethanol, using ultrasonic homogenization method. The mechanical response of STF was studied at high strain rates in terms of the stress-strain behavior and variation of the impact toughness with the loading rate of the fluid specimen. It was observed that the impact toughness of STF increased progressively with the specimen loading rate. The peak stress and peak strain rate attained in the SHPB tests were 147MPa and 22,100 s−1, respectively. The characteristic transition time of STF was found to be in the range of 13–25 µs.

Potential for the formation of respirable fibers in carbon fiber reinforced plastic materials after combustion

SummaryFundamental aspects for the thermal decomposition and formation of respirable fragments of carbon fibers are investigated to assess the health hazard of carbon fiber reinforced plastic material after a fire. The influence of temperature (600°C‐900°C)/heat flux (30‐80 kW/m2), time of thermal load (up to 20 minutes), and oxygen exposure is analyzed by means of mass loss and fiber diameter of intermediate modulus and high tenacity fibers with initial diameters of 5 to 7 μm. Various types and concentrations of flame retardants were tested with respect to fiber protection. Epoxy‐based composite specimens (RTM6/G0939) additionally containing aluminum or magnesium hydroxide and/or zinc borate (1‐25 wt% per resin) were analyzed by cone calorimetry. Carbon fiber decomposition increases with combustion/irradiation time and temperature/heat flux, after a threshold temperature (ca 600°C) is exceeded. Critical fiber diameters below 3 μm are reached within minutes and are predominantly observed close to the panel surface in contact with air. Effective fiber protection is achieved by flame retardants acting beyond 600°C, forming thermally resistant layers such as zinc borate. A new field of research is opened identifying flame retardants, which protect carbon fibers in carbon fiber reinforced plastic.

Influence of molar mass distribution on the final properties of fibers regenerated from cellulose dissolved in ionic liquid by dry-jet wet spinning

Regenerated cellulose fibers were produced by dry-jet wet spinning from cellulose/1,5-diazabicyclo[4.3.0]non-5-ene-1-ium acetate solutions. Cellulose blends with different molar mass distribution but fixed intrinsic viscosity were employed as starting materials to investigate the influence of the cellulose molecular structure on the spinnability and the mechanical properties of the resulting fibers. The cellulose/ionic liquid solutions were prepared from blends constituted of cotton linters and spruce sulfite pulp representing a polydispersity index from 2.0 to 5.9. Dynamic shear rheology was performed on the solutions to examine the effect of cellulose chain distribution on the visco-elastic behavior and to select the adequate temperature for stable spinning. The mechanical and physical properties of the resulting fibers were determined by tensile tests and birefringence measurements. Cellulose solutes having a share of high molecular weight cellulose (DP > 2000) higher than 20% and a minimum polydispersity index of 3.4 showed enhanced spinnability. Higher draw ratios were accessible, resulting in improved cellulose chain total orientation and high-tenacity fibers.

Effect of fiber geometry and tenacity on the mechanical properties of fine aggregates concrete

The effect of fiber cement interactions and its influence on flexural and tensile properties of cementitious composites are well known. In this research, acrylic fibers with different cross sectional and longitudinal shapes and different tensile strengths were selected as reinforcement of the specific fine aggregates concrete. Three point bending test, pullout test, and scanning electron microscopy were used to investigate flexural and pullout behavior of the composites. It was found that flexural toughness and pullout strength were increased 20% and 34%, respectively, by application of kidney shaped acrylic fibers in comparison to dog bone shaped acrylic fibers. It was also found that the flexural and pullout strength of composites containing non-crimped fibers are 33% and 26.5% higher than specimens with crimped fibers, respectively. Results showed that the flexural toughness and pullout strength of high tenacity fiber is 75% and 131% higher than regular fiber as well, respectively. The effect of fine aggregates on the adhesion of fibers to cement matrix was evaluated.

Electric-Field-Induced Actuation of Poly(vinyl alcohol) Microfibers

Poly(vinyl alcohol) (PVA) microfibers were actuated by application of a direct current (dc) electric field; there were large electrosensitivity differences between water-soluble and high-tenacity fibers. In particular, a bending actuation was observed for water-soluble PVA fibers with high sensitivity and large deformation upon applying a dc electric field. The mechanism of bending actuation was investigated through analysis of the chemical constituents, dielectric properties, bending rigidity, and morphology. It was found that the actuation behavior depends mainly on the mechanical and dielectric properties, which are related to the chemical structures of the fibers. It is clear that hydroxyl and carbon−oxygen double bonds are key factors influencing the electroactive characteristics. The content of hydroxyl groups not only determines the solubility of PVA fibers in water but also controls the antielastic bending. The content of CO groups may be related to the dielectric constant and bending rigidity. Furthermore, the CS bond in the X-ray photoelectron spectrum indicates that dimethyl sulfoxide remains even after solvent removal, and this can make it easier for the PVA fibers to become positively charged and then bend toward the cathode.

Polytetrafluoroethylene (PTFE) fiber reinforced polyetheretherketone (PEEK) composites

Abstract This work uses high tenacity expanded polytetrafluoroethylene (ePTFE) filaments as both a fiber reinforcement and a reservoir for solid lubricants. The goal is to reduce the wear of the composites by regulating the PTFE transfer. Expanded PTFE films are a porous network of PTFE nodes and fibrils, while highly oriented ePTFE filaments are aligned crystalline fibers that are regarded as high-tenacity fibers that can be woven into threads or yarns. Reported yield strength of these filaments can exceed 500 MPa. The best performing composites were those that had filaments of ePTFE aligned normal to the counterface. The wear rates obtained from the inclusion of expanded PTFE filaments were better than conventional powder filled PTFE–PEEK composites reaching values as low as K = 7 × 10−8 mm3/N m and showed stable friction coefficients below μ = 0.125 for over 2 million cycles.

Advantages of Fiber Rope Over Wire Rope

Over the years, fiber ropes have increased in strength to the point where they began to replace wire ropes in some applications. The major factors have been the development of high tenacity fibers and the advancements in fiber rope constructions. This started with high tenacity nylon and polyester fiber ropes, ropes combining both of those fibers, the combining of polyester and polypropylene ropes and ropes combining polypropylene and polyethylene. This was followed by the development of high-tech fibers, with the result that stronger and stronger ropes could be produced to the ultimate where a fiber strength member can provide a 10–1 strength-to-weight ratio advantage over wire rope. At the same time, new finishes for fibers were developed that improved durability and strength retention, new constructions were able to provide increased translation efficiency, and better inspection and testing methods were developed. Application advantages are discussed, each having a number of factors that reduce costs, even though the actual cost of the fiber strength member may be slightly higher than for wire. The result is a rationale that when the cost of a flexible strength member is fully measured there is a strong reason that a fiber strength member, when compared with a wire rope, can save money and improve operations in an increasing range of applications.

Model of Nylon 6 Fibers Microstructure Microfibrillar Model or “Swiss-Cheese” Model?

The microfibrillar morphological structure of aliphatic polyamide fibers has been consistently presented by the three phase microfibrillar model proposed by Prevoršek and not by the two phase microfibrillar model proposed by Peterlin. A widely spread opinion is that the 3-phase or “Swiss-cheese” model is applicable in all cases, either in case of high-tenacity fibres or in case of standard Nylon 6 textile fibers. Although the 3-pbase X-ray analysis is now routinely performed, the basic issue of 2-phase vs. 3-phase model has not yet been resolved. We have investigated the suitability of both models and found out that the 3-phase model which is suitable for high-tenacity Nylon 6 fibres cannot be applied in case of aliphatic Nylon 6 fibres manufactured by standard melt spun process. The microfibrillar structure of these fibers resembles to the microfibrillar model of PE more than to the morphology of high-tenacity Nylon 6 fibres. The generally established opinion about applicability of the 3-phase model for all aliphatic Nylon 6 fibres, regardless of the fiber forming process, is not acceptable. The key finding is. however, that Nylon 6 fibers can exist, depending on the forming process, in two morphologically different modifications corresponding to the above-mentioned models. By altering the fiber forming process it is possible to alter the morphology and to control the distribution of amorphous extended interfibrillar and intrafibrillar molecules, and to widen the range of mechanical and thermal properties.

Structure-Property Relationship of Blended Cotton Yarns Made from Low and High Tenacity Fibers

The tensile response of staple yams is usually determined by their structure and the mechanical properties of their constituent fibers. Yarn structure is influenced by the radial disposition of fibers along the yam length, commonly known as migration, and the packing density of the fibers in the yarn cross section. These, in turn, are affected by fiber properties, yarn factors, and the dynamics of preparatory and spinning pro cesses. Yarn structure development is further complicated when the yarn is spun from blends of different fiber types because the blending method usually profoundly influ ences the position and orientation of the fibers in the yam matrix. This investigation is concerned with the effect of fiber properties and yarn structure on the tensile properties of ring spun yarns made from a 50:50 blend of high (Pima) and low (Upland) tenacity cotton fibers spun using intimate and drawframe blending techniques. The drawframe blended yarn in this work is produced by arranging all high tenacity fiber slivers in the center of the drawframe creel to determine if preferential positioning in the core of the yam helps to improve the strength of drawframe blended yarn compared with intimate blended yarns. The findings reveal that intimate blended yam has better tensile strength than drawframe blended yarn, even though more high strength Pima cotton fibers are positioned in the core of the yam. This is because non-uniform fiber distribution re sulting from blending of different fibers affects the migratory behavior of fibers. The tensile failure of such yams is governed by the mode of fiber breakage and fiber slippage as determined by the yarn structure—fiber distribution and migration—rather than predominantly by fiber breakage compared with strength.

Design, synthesis and properties of a novel rigid rod polymer, PIPD or `M5': high modulus and tenacity fibres with substantial compressive strength

A rigid rod polymer with strong hydrogen bonds between the polymer chains was found in polypyridobisimidazole based on 2,3,5,6-tetraaminopyridine and 2,5-dihydroxyterephthalic acid (D. J. Sikkema and V. Lishinsky, WO 94/25506). The strong interchain forces translate into the highest compressive strength found in polymer fibres by far, and the polarity of the polymer seems to contribute to easy adhesion in advanced composite manufacture. The modulus and tenacity are as expected for a rigid rod polymer in the general class of the earlier PBZT and PBO fibres.

Polypropylene Fibres: An Industrially Feasible Pathway to High Tenacity

Extensive studies concerning the spinning and drawing of polypropylene have resulted in the identification of an industrially feasible pathway for the production of fine (< 0.6 tex) very high tenacity fibres (85 cN/tex). Essentially, as-spun fibres are produced from a low molecular weight polymer (MFI 35 g/10min) extruded at 280°C with a winding speed of 200 m/min. These paracrystalline fibres of low orientation are then subjected to a two-stage drawing process. The first stage, carried out at 60°C, results in oriented paracrystalline fibres which are then, during the second stage, transformed at a temperature of 140°C into highly oriented monoclinic fibres.

Regenerated Cellulose Fibers Spun from Organic Solvent.

The dry-wet spinning mechanism of regenerated cellulose fibers was examined by using N-methylmorpholine N-oxide (MMNO), which is known as a good organic solvent of cellulose. The special interest was paid on the effects of an air-gap length and a draft ratio of spinning process on mechanical properties and micro-structure of regenerated cellulose fibers, so as to control the mechanical properties of the fibers. In this study, cellulose MMNO solution with high concentration and high viscosity could be made due to the good solubility of MMNO. The regenerated cellulose fibers spun from MMNO solution gave the cellulose II crystalline unit cell. The mechanical properties of the regenerated fibers were widely changed by changing the air-gap length and the draft ratio, and the high-tenacity fibers were obtained by spinning conditions of 10-50mm of air-gaps and greater than 6 of draft ratios. The maximum modulus and tenacity in this series of the fibers were 214g/d and 5.8g/d, respectively.