Tensile Properties Of Single Fibers Research Articles

Experimental Study on Single Fiber Tensile Properties of Sisal Fibers Using a Digital Image Correlation Method as a Strain Measurement

ABSTRACT The development of natural fibers in engineering applications requires an accurate measurement of their dimensional characteristics and mechanical properties. Fiber cross-sectional area (CSA) obtained from lateral dimensional measurements should consider the specific cross-sectional shape (CSS) of the fibers and their wide lengthwise variations. In this study, the dimensional measurements of water-retted and unretted sisal fibers were conducted by laser scanning microscopy (LSM) and calculation-based methods. Single fiber tensile tests were performed using the digital image correlation (DIC) method. Results show that the diameters of water-retted and unretted fibers measured by LSM were 233 ± 45 µm and 236 ± 42 µm, respectively. The diameters of water-retted and unretted fibers obtained by calculation were 192 ± 17 µm and 178 ± 20 µm, respectively. The tensile strengths of water-retted and unretted fibers were 679 ± 118 MPa and 718 ± 106 MPa, respectively. The strain at failure and elastic modulus of water-retted and unretted fibers were 2.0 ± 0.6% and 34 ± 8 GPa, as well as 1.5 ± 0.2% and 48 ± 6 GPa, respectively. Water retting seems to predominantly influence the strain at failure and elastic modulus of sisal fibers, as confirmed by the ANOVA analysis.

Characterization of Cellulosic Leaf Fiber from the Typha Angustifolia Plant

ABSTRACT Typha leaves are a rich source of fiber cables and these fibers can also be extracted by chemical retting method and these are easily bio-degradable, and eco-friendly. The main objective of present work is to assess the fiber characteristics such as FTIR, XRD, TGA, SEM, and single fiber tensile properties by varying fiber extraction parameters. In the retting process, IR peaks clearly shows that there was a removal nonfibrous material (NFM). Using X-ray diffraction technique 67.61% crystallinity with a crystallinity index of 0.521 was observed. Fiber tips of SEM images confirm that by increase in chemical concentration and treatment time, there was more removal of NFM and fibrillation found. For the fiber extraction mainly two treatment particulars were varied i.e. sodium hydroxide (10, 20, and 30 gpl) and time (3, 4, 5, and 6 h). Out of various retting conditions, at 20 gpl with 4 and 5 h treatment time shows an excellent tensile strength of single fiber, i.e. 125 Mpa and 179.82 Mpa and 30 gpl with 4 hrs and 5 h observed moderate strength, i.e. 106.03 Mpa and 122.69 Mpa respectively.

Improved Mechanical Properties and Theoretical Prediction of Young’s Modulus of Polylactide Composites Reinforced with Sisal Fibers

The aim of this study is to evaluate the effect of different surface modifications on mechanical properties of sisal fiber reinforced PLA (SF/PLA) composites. Using theoretical models Young’s modulus of the SF/PLA composites has been predicted. Tensile properties of single fiber showed a reduction in the tensile strength and modulus by 25% and 26% respectively as compared to the untreated sisal fiber owing to surface treatments. Optimization of fiber loading has also been studied for SF/PLA composites. The tensile strength increased by 10% for 15 wt% of fiber loading with the combined treatment of alkali and HIU as compared to the untreated fiber reinforced PLA composites. Tensile modulus of 30 wt% of fiber loading showed 75.4% increment as compared to pure PLA. Young’s modulus of the composites has also been predicted by using the theoretical models which fit well to the obtained experimental values. This investigation confirms that the surface treatments of SF/PLA composites with alkali and HIU are effective to improve their mechanical properties

Reinforcement of natural fiber yarns by cellulose nanomaterials: A multi-scale study

Cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) were used to improve the mechanical properties of tapes and yarns produced from natural fibers as a new application of cellulose nanomaterials in textile-based composite products. Hemp and flax slivers were used as natural fibers for the production of yarns and tapes. CNC, unground CNF and two different ground CNF suspensions were used as the reinforcement agents. Fiber strands from each natural fiber were soaked in the cellulose nanomaterial suspension and then were processed into tapes or yarns. Individual hemp and flax fibers where also soaked in the same suspensions and dried. SEM microscopy of the surfaces and cross-sections of the yarns and tapes showed that cellulose nanomaterial suspensions affected the morphology of the natural fiber yarns and tapes by filling gaps and adhering the fibers together. Results of studies on tensile properties of single fibers showed improvement in initial modulus and strength of flax fibers after soaking in nanocellulose suspensions especially when CNF was used. Such consistent results were not however seen for hemp single fibers. Yarns and tapes produced by soaking fiber strands in different nanocellulose suspensions had considerably higher tensile properties in terms of strength and initial modulus than controls. Furthermore, it was shown that mixing cellulose nanomaterial suspensions with natural fibers improved the dewatering/drying process, a necessary step should cellulose nanomaterials be used in composite applications.

Property and Shape Modulation of Carbon Fibers Using Lasers.

An exciting challenge is to create unduloid-reinforcing fibers with tailored dimensions to produce synthetic composites with improved toughness and increased ductility. Continuous carbon fibers, the state-of-the-art reinforcement for structural composites, were modified via controlled laser irradiation to result in expanded outwardly tapered regions, as well as fibers with Q-tip (cotton-bud) end shapes. A pulsed laser treatment was used to introduce damage at the single carbon fiber level, creating expanded regions at predetermined points along the lengths of continuous carbon fibers, while maintaining much of their stiffness. The range of produced shapes was quantified and correlated to single fiber tensile properties. Mapped Raman spectroscopy was used to elucidate the local compositional and structural changes. Irradiation conditions were adjusted to create a swollen weakened region, such that fiber failure occurred in the laser treated region producing two fiber ends with outwardly tapered ends. Loading the tapered fibers allows for viscoelastic energy dissipation during fiber pull-out by enhanced friction as the fibers plough through a matrix. In these tapered fibers, diameters were locally increased up to 53%, forming outward taper angles of up to 1.8°. The tensile strength and strain to failure of the modified fibers were significantly reduced, by 75% and 55%, respectively, ensuring localization of the break in the expanded region; however, the fiber stiffness was only reduced by 17%. Using harsher irradiation conditions, carbon fibers were completely cut, resulting in cotton-bud fiber end shapes. Single fiber pull-out tests performed using these fibers revealed a 6.75-fold increase in work of pull-out compared to pristine carbon fibers. Controlled laser irradiation is a route to modify the shape of continuous carbon fibers along their lengths, as well as to cut them into controlled lengths leaving tapered or cotton-bud shapes.

Evaluating Tensile Properties of Wool Fibers Based on the Waveform of Acoustic Emission

As an indirect measurement, acoustic emission (AE) of fiber break reflects the deformation energy during rupturing. It can be employed to evaluate the tensile properties of single fiber in fiber-bundle tensile test. In this paper, the extension of single wool fiber in the fiber-bundle are calculated using AE method. Comparing to the control samples whose extension distribution is derived from the stress-strain curve of fiber bundle, it is believed that the extension distribution calculated from AEs is more accurate and reliable, since it is not affected by the discreteness of fiber strength. The experimental results also show that there is a good linear relationship between the break force of single wool fibers and their AE energy.

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%.

Comparison of the properties of scutched flax and flax tow for composite material reinforcement

The industrial production of flax fibers yields two fibrous products: scutched fibers are valuable for their length, fineness and cleanness, while tows are entangled, impure and are low-priced. There is a need for technical data to compare these two kinds of fibers beyond the difference of appearance, and to assess their potential as composite material reinforcements. In this work, we have compared the properties of scutched flax and flax tows from the same batch. The morphology was first assessed by measuring the length, cleanness and fineness of fiber bundles. The tensile properties of single fibers and of unidirectionally reinforced epoxy composites were then measured. The results show that the morphology of flax tows is different from but close to the morphology of scutched flax. Tow bundles were 15% shorter than scutched flax bundles and tow bundles were 25% thicker than scutched flax bundles. The tensile properties of single fibers were in the same range. Tensile properties of the unidirectional composites show a similar evolution of properties versus fiber volume fraction. The use of scutched flax allowed volume fractions of 0.7 to be achieved while tow volume fraction was limited to 0.6. Despite the visual and morphological difference between tows and scutched flax both can be good candidates for composite reinforcement in high performance applications.

Influence of the degree of retting of flax fibers on the tensile properties of single fibers and short fiber/polypropylene composites

The flax quality required for composite applications is not yet well established. Retting is one of the steps that are not well defined for these applications, and is a critical parameter during flax production. In this study, the influence of the degree of retting of flax on the properties of short flax fiber/polypropylene composites has been assessed. First, the degree of retting of gradually retted flax was measured by both qualitative and quantitative experimental techniques. In addition, water sorption studies were performed. Furthermore, tensile tests were carried out on both single fiber and injected composite materials. The microstructure of the composites was analyzed by scanning electron microscopy and X-ray micro-tomography. Single fiber and composite tensile properties, as well as water sorption behavior of flax fibers, were found to depend upon the degree of retting.

Effects of surface modifications on the interfacial bonding of flax/β-polypropylene composites

Interfacial bonding is a key factor for the successful application of flax/polypropylene (PP) composites. In this study, the effects of various chemical treatments on the interfacial bonding of flax/β-PP composites are investigated using a single-fiber pull-out test. Interfacial performance is evaluated using the following three chemical treatments: (1) alkali; (2) maleic anhydride PP (MAPP) copolymer; and (3) vinyltrimethoxysilane (VTMO). The crystalline morphology of PP matrices around the flax fiber and the treated single-fiber tensile properties are investigated. The results show that alkalized fiber treatment is crucial to successful interfacial modification. Further improvement is achieved using MAPP and VTMO treatments. The highest interfacial shear strength for α-PP and β-PP systems is 15.9 and 12.1 MPa, respectively. A grafting mechanism is proposed to describe the modification of VTMO on flax fibers.

The multi-pore-structure of polymer–silicon hollow fiber membranes fabricated via thermally induced phase separation combining with stretching

UHMWPE/PVDF/SiO 2 hollow fiber membranes with a multi-pore structure were fabricated via thermally induced phase separation combining with stretching (TIPS-S). The preparation process utilized mineral oil as the diluent. A finite element calculation was used to predict generation of interface pores and the deformation of the polymer matrix. This approach enabled assumptions about phase separation and interface pore generation to be formulated. The formation and development of the interface pores were studied by scanning electron microscopy (SEM). Membrane performance was characterized by a variety of metrics including permeability, melting and crystallization behavior, porosity and pore diameter, and single-fiber tensile properties. The results indicated that the membrane evidenced a multi-pore-structure consisting of TIPS-generated pores, broken pores in the amorphous region, and interface pores formed by drawing. This complex pore structure enabled improved membrane permeability. These experimental results were in agreement with the assumptions obtained from the use of finite element analysis.

Hierarchical composites of carbon nanotubes on carbon fiber: Influence of growth condition on fiber tensile properties

Growing carbon nanotubes (CNT) on the surface of high performance carbon fibers (CF) provides a means to tailor the thermal, electrical and mechanical properties of the fiber–resin interface of a composite. However, many CNT growth processes require pretreatment of the fiber, deposition of an intermediate layer, or harsh growth conditions which can degrade tensile properties and limit the conduction between the fiber and the nanotubes. In this study, high density multi-wall carbon nanotubes were grown directly on two different polyacrylonitrile (PAN)-based carbon fibers (T650 and IM-7) using thermal Chemical Vapor Deposition (CVD). The influence of CVD growth conditions on the single-fiber tensile properties and CNT morphology was investigated. The mechanical properties of the resultant hybrid fibers were shown to depend on the carbon fiber used, the presence of a sizing (coating), the CNT growth temperature, growth time, and atmospheric conditions within the CVD chamber. The CNT density and alignment morphology was varied with growth temperature and precursor flow rate. Overall, it was concluded that a hybrid fiber with a well-adhered array of dense MWCNTs could be grown on the unsized T650 fiber with no significant degradation in tensile properties.

Flax fiber surface modifications: Effects on fiber physico mechanical and flax/polypropylene interface properties

This study arises on the opportunities of using flax fibers as reinforcement for polypropylene (PP) matrix composites. For this purpose, untreated flax fiber bundles obtained by a retting process have been used. For improving compatibility between flax fiber bundles and PP matrix, fiber surface treatments such as maleic anhydride, maleic anhydride polypropylene copolymer, and vinyltrimethoxy silane have been carried out. On the other hand, alkali treatment has also been carried out for fiber modification. The effect of surface modification on tensile properties of single fibers and also on fiber-matrix interfacial shear strength (IFSS) has been analyzed. Finally, both optical microscopy and atomic force microscopy have been used for characterizing flax fiber microstructural features. The current study completes previous results to elucidate the influence of treatments on fiber surface and flax fiber-PP interface. POLYM. COMPOS. 26:324–332, 2005. © 2005 Society of Plastics Engineers.

Estimating Single Cotton Fiber Tensile Properties from the Load-Elongation Curves of Slack Bundles

A method has been developed to estimate single cotton fiber tensile properties from load-elongation curves of slack fiber bundles. The method is applied to bundle load- elongation curves from HVI tests to estimate the averages of fiber breaking strength, elongation, and crimp. The estimated values are compared with single fiber tensile properties obtained from a Mantis® single fiber tester.

Evaluating Single Fiber and Fiber Bundle Tensile Curves

Most research on estimations of fiber bundle tensile curves from single fiber tensile properties is based on knowledge of the frequency density distribution of fiber breaking extension and the linear elastic spring constant. Such research focuses on cotton fibers and fiber bundles. On the other hand, there are few methods to predict the tenacity of single wool fibers from fiber bundle tensile curves. Using characteristics of specific stress-strain curves from both single fiber and fiber bundle tensile testing, new theoretical calculations to estimate the tenacity and breaking extension distribution of single fibers from bundle tensile curves are described in detail for wool fibers. The experimental results show that these algorithms are effective and reliable for such evaluations, the experimental and estimated results obtained from the TENSOR fiber bundle tests and the SIFAN single fiber measurements agree with each other, and single fiber tenacity or even its urve can be evaluated using the tail of the bundle tensile curve.

Variations of Mature Cotton Fiber Tensile Properties: Association with Seed Position and Fiber Length

Variations in single fiber tensile properties of mature cotton fibers are investigated with respect to their association with seed positions and fiber-length groups within individual locules. Fibers from five varieties representing four cultivated cotton species ( G. herbeceum, G. arboreum, G. hirsutum, and G. barbadense) are included in this study. With the exception of G. arboreum, breaking forces, toughness, and linear density are highly dependent on the seed position in the locule, and the dependence is especially high for G. herbeceum and G. barbadense. Fibers from seeds located closer to the main stem have higher breaking forces and linear densities, indicating their association with the distribution of nutrition resources. The relationships between single fiber tensile properties and fiber lengths vary among these cotton species. Breaking force and tenacity are independent of fiber length for G. barbadense, whereas fiber-length dependence is positive for G. herbeceum and G. arboreum, and there is a negative trend for the Maxxa variety of G. hirsutum. For G. herbeceum and G. arboreum, longer fibers have higher breaking forces, whereas the opposite is true for Maxxa. Single fiber breaking elongation decreases with increasing fiber length for all except G. barbadense. Overall variations of single fiber tensile properties are associated more strongly with the seed position in the locule than with the fiber length.

Study on the effects of single fiber tensile properties on bundle tensile properties through estimation of HVI bundle modulus and toughness

The HVI properties and Mantis® single fiber tensile properties were analyzed to evaluate the relationship between fiber and bundle tensile properties. For this study, a new method has been developed for estimating the modulus and toughness of cotton fiber bundles directly from the HVI tenacity-elongation curves. The single fiber tensile properties were shown to be translated well into the bundle tensile properties. The single fiber breaking elongation was found to be the most significant contributing factor to bundle tensile properties. The bundle breaking elongation and toughness were shown to increase as the single fiber breaking elongation increased. The bundle modulus increased as the single fiber breaking elongation and/or standard deviation of single fiber breaking elongation decreased.

Tensile Behavior of Slack Fiber Bundles—Theory and Application to HVI Testing

A statistical model for the tensile behavior of a bundle of slack fibers is developed in terms of its constituent single fiber properties. A large amount of data on single fiber tensile properties is obtained by a Mantis® tester. Application of this theory to HVI tensile test results shows much better agreement than other models developed earlier for bundles of straight, equal length fibers.

Effects of a pulsed XeCl excimer laser on ultra-high strength polyethylene fiber and its interface with epoxy resin

The effects of excimer laser treatment on the changes in the surface topography, the physical and chemical properties of ultra-high strength polyethylene (UHSPE) fibers, and their interfacial property with epoxy resin were investigated. The scanning electron microscopy (SEM) photomicrographs show that UHSPE fibers exhibit a rougher surface after irradiation with the XeCl pulsed excimer laser as a result of intense laser heat and ablation. The wettability and surface chemistry of control and laser-treated UHSPE fibers were monitored by TRI wettability/friction apparatus. The chemical changes on the surfaces of UHSPE fibers were analyzed by Fourier transform infrared spectroscopy (FTIR) in attenuated total reflectance (ATR) mode. The tensile properties of single fibers, before and after laser treatment, were studied using an Instron tensile tester. Interfacial shear strength (IFSS) measurements were performed using the single-fiber pull-out test. The fiber surface becomes polar after the laser treatment with increased acid-base contribution. The strength of laser-treated UHSPE fibers is lower than that of the control fibers. The IFSS results indicate that laser treatment improves the adhesion strength of UHSPE fibers with epoxy resin because of the changes in surface chemistry and enhanced roughness. The results show the potential of the excimer laser as an alternative surface treatment for fibers to enhance their adhesion with epoxy resins.

Torsional and Tensile Properties of Single Fiber

Torsional and Tensile Properties of Single Fiber