Single Fiber Bundle Research Articles

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.

Formation of damage and its effects on non-crimp fabric reinforced composites loaded in tension

Non-crimp fabric (NCF) composites, manufactured by resin infusion techniques are one of the most promising next generation composite materials. They offer large potential for application in primary structures as they give excellent performance at low production costs. However, before NCF composites will be efficiently used in design, detailed understanding of governing micro mechanisms must be accumulated and described by predictive models. In the present study, NCF cross-ply laminates have been tested in tension. Intralaminar cracks caused in the 90° fibre bundle layers and their effect on laminate mechanical properties have been monitored. Occurrence of ‘novel’ type of cracks propagating in the load direction (longitudinal cracks) is explained by a thorough FE analysis using an Representative Volume Element (RVE) approach, revealing stress concentrations caused by 0° fibre bundle waviness. Effects of damage on mechanical properties are modelled using modified micro mechanical models developed for analysis of conventional laminated composites. The analysis reveals mechanical degradation to be ruled by the crack opening displacement (COD). However, unlike traditional composites, transverse cracks do not generally extend through the entire thickness of the 90° layer, but are rather contained in single fibre bundles, limiting the COD.

Protecting multicast sessions in WDM optical mesh networks

Recent advances in wavelength-division-multiplexing (WDM) technology are expected to facilitate bandwidth-intensive multicast applications. However, a single fiber (bundle) cut on such a network can disrupt the transmission of information to several destination nodes on a light tree-based multicast session. Thus, it is imperative to protect multicast sessions e.g., by reserving resources along backup trees. We show that, if a backup tree is directed-link-disjoint to its primary counterpart, then data loss can be prevented in the event of any single link failure. We provide mathematical formulations for efficient routing and wavelength assignment (RWA) of several multicast sessions (including their backup trees for dedicated protection) at a globally optimum cost. We present these formulations for networks equipped with two kinds of multicast-capable switch architectures: one using the opaque (O-E-O) approach and the other using transparent (all-optical) approach. We expand our formulations to accommodate sparse splitting constraints in a network, in which an optical splitter has limited splitting fanout and each node has a limited number of such splitters. We develop a profit-maximizing model that would enable a network operator to be judicious in selecting sessions and simultaneously routing the chosen ones optimally. We illustrate the solutions obtained from solving these optimization problem formulations for a representative-size network.

Axial impregnation of a fiber bundle. Part 1: Capillary experiments

AbstractThis is an experimental study to investigate the axial capillary impregnation of an E‐glass fiber bundle by using two Newtonian infiltrating fluids: (a) silicone oil and (b) epoxy. First, the wetting properties of the systems were measured, i.e. the surface tension of each fluid and the contact angle between the fluid and a single fiber filament. Liquid height and weight data as a function of time were collected from several capillary impregnation experiments of single fiber bundles. A data analysis is presented following either the integral or the differential approach to determine capillary pressure, permeability and porosity. The so‐determined values of capillary pressure were compared to corresponding theoretical values and were generally found much lower, unless the duration of the capillary experiment was around a month. This long‐term experiment brought substantial improvement in the determined values of capillary pressure. The infiltration plots from the experimental data will be further used for validation of theoretical inpregnation curves, which will result in the theoretical prediction of permeability and capillary pressure in Part 2 of this study (1).

Industrial hemp ( Cannabis sativa L.) growing on heavy metal contaminated soil: fibre quality and phytoremediation potential

Hemp ( Cannabis sativa L.) was used to examine its capability as a renewable resource to decontaminate heavy metal polluted soils. The influence of heavy metals on the fibre quality was of special interest. Determination of heavy metal content was carried out by means of atomic absorption spectroscopy (AAS). Four different parts of the plant were examined: seeds, leaves, fibres and hurds. In each case, the concentration relation was Ni>Pb>Cd. However, the heavy metal accumulation in the different parts of the plant was extremely different. All parts of hemp plants contain heavy metals and this is why their use as a commercially utilisable plant material is limited. We found that the highest concentrations of all examined metals were accumulated in the leaves. In this field trial, hemp showed a phytoremediation potential of 126 g Cd (ha vegetation period) −1. We tested the fibre quality by measuring the pure fibre content of the stems and the fibre properties after mechanical separation. In addition, the fibre fineness was examined using airflow systems and image analysis. The strength was measured by testing single fibre bundles with a free clamping distance of 3.2 mm using a universal testing device. Finally, we compared the results from the stems and fibres from trials on heavy metal polluted ground with hemp stems and fibres from non-polluted ground. Since there was no comparable unpolluted area near the polluted one, reference values were taken from an area quite far away and subsequently with a different soil composition and also exposure to different meteorological conditions. Thus, the observed differences are only partially caused by the heavy metal contamination.

Modeling Analysis of Tensile Tests of Bundled Filaments with a Bimodal Weibull Survival Function

A convolution model applied to single mode Weibull fiber bundle experiments was extended to predict the response of bimodalmodel bundles. Published data for bimodal SiC fibers predicted the sensitivity of bundle test as a function of gauge length. A bundle test could rapidly determine the modality of a bundle from experiments at two gauge lengths. Next, the method checked the applied strain rate bimodality of Kevlar. The analysis indicates that a bundle test cannot determine the parameters of a modelthat predicts variation in apparent modulus or strain to failure since slack in the bundle generates these effects.

Glass fibre strength distribution determined by common experimental methods

The tensile strength of brittle fibres is routinely described by the Weibull distribution. The parameters of the distribution can be obtained from tests on single fibres and fibre bundles or from model composite tests. However, there is growing evidence that the distribution parameters obtained by different experimental techniques differ systematically. In order to investigate the possible causes of such discrepancies, single-fibre tension, fibre bundle, and single-fibre fragmentation tests are employed in this study to obtain strength distribution of commercial E-glass fibres. The results reveal parameter dependence on the approach used to extract the distribution parameters from experimental data. Particularly, in the case of single-fibre tension tests, the shape parameter obtained from average fibre strength vs. length data is larger than that obtained at a fixed gauge length. It is assumed that the apparent fibre strength scatter is caused by both the inherent flaw structure along a fibre and by the fibre-to-fibre strength variability within a batch, due to slightly differing processing and handling history of the fibres. Fibre fragmentation test results are used to derive the Weibull distribution parameters applicable to the fibre batch. The strength distribution obtained is compared with strength data for the single fibres, and reasonably good agreement is observed.

Effects of 17beta-estradiol on tension responses and fatigue in the skeletal twitch muscle fibers of frog.

The effects of 17beta-estradiol (10(-5) M), an active estrogen, on the tension and fatigue responses of single fiber or fiber bundle prepared from frog skeletal muscle were investigated. The administration of 17beta-estradiol caused a transient potentiation of tetanus tension by field stimulation at every minute. This potentiation was not affected by the presence of nicardipine, suggesting that the action of 17beta-estradiol would place the excitation-contraction (E-C) coupling beyond T-tubule depolarization. Fatigue was produced by repeated tetanic stimulation every second until tension declined to approximately 40% of the initial level. Fibers were then allowed to recover by having tetani given to them every minute. In the normal Ringer solution, the time to 50% of the initial tetanus tension was 41.7 s. With the presence of 17beta-estradiol, the time to 50% tension was faster than that of control. The presence of 17alpha-estradiol, a stereoisomer, caused no potentiation of tetanic tension to be stimulated every minute, and the rate of decline of fatigued response was almost the same as that of control, suggesting the existence of specific estrogen receptors in the frog muscle. In fatigued muscle with or without estrogen, the tension to field stimulation was transient and not sustained. When the fatigued muscle was again treated with field stimulation at every minute after the more-frequent stimulation, the recovery rate was increased in 17beta-estradiol. A prompt reduction in temperature to 5 degree C, from 20 degree C, in the presence of caffeine elicited the tension response, a rapid cooling contracture (RCC). The presence of 17beta-estradiol inhibited peak tension and maximum rate of rise of the RCC only after the repetitive electrical stimuli. These results suggest that the potentiation of contraction upon the electrical stimulation by 17beta-estradiol was induced by the increase of myoplasmic-free Ca(2+) concentration via an activation of some E-C coupling process. The 17beta-estradiol-induced facilitation of fatigue response to repetitive tetanus stimuli with high frequency may be due to an increase in the imbalance of Ca(2+) turnover in the cytoplasm.

A Study of Wool's Tensile Strength in Early Stage Processing

The tensile strength of wool during pre-spinning processing is examined in this paper. Both single fiber breaking load and fiber bundle strength are studied. The results confirm that carding causes more fiber damage or strength loss than other processes examined. The breaking load of fibers in combed sliver may be significantly higher than that in carded sliver, because combing breaks weak fibers damaged in carding and increases the average fiber diameter in combed sliver by removing some fine fibers. An attempt is made to generate an ideal bundle strength profile from single fiber tensile curves. Compared with the tensile curve of the ideal fiber bundle, the tensile curve of an actual wool bundle shows a relatively higher elongation and lower tenacity, probably due to the between-fiber interactions and relatively poorer fiber orientation in the actual wool bundle. A method of minimizing fiber interaction during bundle strength testing is proposed.

Mechanical and Impact Properties of Untreated Jute Fabric Reinforced Polyester Laminates Compared With Different Ε-Glass Fibre Reinforced Laminates

In recent years, the improvement of properties of natural fibre reinforced laminates over the pure polymeric matrix has been thoroughly investigated with the aim of providing a possible replacement of E-glass fibre reinforced composites for some large-volume applications. In the present study, the properties of a jute/polyester laminate are compared with those yielded by two E-glass fibre woven laminates. These are an Eglass/polypropylene commingled twill weave laminate (®Twintex) and a plain woven-roving E-glass/polyester composite. These two materials are representative of a large part of glass fibre reinforced laminates currently used, since Twintex is widely used e.g., in automotive industry, while glass mat/polyester laminates are still very popular in naval applications. All the materials have a 60% wt. fibre content. A number of tests were carried out, including mechanical tests, interlaminar shear strength tests, Charpy impact and falling weight impact tests. After that, the consolidation of the composites was investigated by interlaminar shear strength tests and observing the porosity present in the materials under an optical microscope. The results confirm the concerns on impact performance of natural fibre reinforced composites. Moreover, mechanical and impact properties on jute fibre reinforced composites show not negligible scattering, that makes it difficult to measure the maximum load values that can safely be applied to these materials during their service. This variation of properties is due mainly to not constant fibre fraction in the composite and to the scattering in properties between the single fibres and fibre bundles. In spite of this, the mechanical and impact properties of jute/polyester laminates as a whole proved promising.

Muscle fiber conduction velocity at different states of isotonic contraction.

Conduction velocity (CV), relative twitch force (RTF) and contraction time (CT) of single muscle fibers (SF) and small muscle fiber bundles (FB) were measured at different states of isotonic contraction with double impulse stimuli at varying interstimulus intervals (ISI) from 0 to 1000 ms in the biceps brachii muscle in vivo. During an isotonic contraction, muscle fibers conducted the action potential on average 0.18 m/s faster along the muscle fiber membrane than did relaxed muscle fibers. This difference was statistically significant (P < 0.001). There was a significant positive correlation between the degree of isotonic contraction and fiber bundle conduction velocity (FBCV) with a first peak at the maximum RTF at an ISI of 9 ms and a second peak at the maximum CT at an ISI of 100 ms.

Thermal stabilization of polyacrylonitrile fibres

A polyacrylonitrile (PAN) fibre, Dralon T (DT), and a copolymer manufactured as a carbon fibre precursor, Special Acrylic Fibre (SAF), were studied as received and after heat-treatment in air at various temperatures up to 300°C. Wide angle X-ray scattering (WAXS) was undertaken on single fibres, fibre bundles and films, utilizing both conventional and synchrotron sources. With a conventional source, the normal WAXS pattern was observed for both polymers, i.e. two main equatorial reflections, a diffuse equatorial reflection and a diffuse off-equatorial reflection. With a synchrotron source, seven equatorial WAXS reflections could be detected in DT. Also, a sharp, meridional reflection was observed in SAF as received and in DT after stretching at 100°C. Unpolarized and polarized infra-red spectra were obtained from single fibres and films by FTIR microscopy. A measure of the extent of reaction (EOR) following heat-treatment was derived from the intensity of the nitrile absorption and the intensity of absorption at 1600 cm −1: EOR=[ I 1600/( I CN+ I 1600)]. Two complementary measures of orientation were used to follow changes on heat-treatment: the peak width at half-height of an azimuthal plot of the most intense WAXS reflection and the nitrile dichroic ratio from FTIR microscopy. For fibres held under tension during heat-treatment, the degree of orientation by either measure did not decrease until the EOR exceeded 0.5. Solid-state 13C NMR, together with IR results, indicated that at least three chemical processes occurred on heat-treatment: nitrile reaction, conjugated C=C formation and oxidation.

Optical fiber water droplet sensor using absorption of fluorescence of Tm^3+:YAG

A two-dimensional noncontact optical fiber water droplet sensorthat uses the fluorescence from a laser-diode-pumpedTm(3+):YAG and that uses a single fiber bundle for the probefiber has been constructed. The sensor is based on absorptionspectroscopy but has the significant advantage that the residual pumplight works for the reference signal. The water depth can beevaluated from the minimum intensity ratio between the fluorescencesignal and the reference signal when the probe is scanned inplane. The sensor can also estimate both the size and the positionof a water droplet. A high degree of discrimination of a waterdroplet from other perturbations such as oil and surface irregularitieshas been demonstrated. An approximate calculation in ahemispherical model of a water droplet was carried out and is shown tobe in good agreement with experimental results.

Studies on the 14.5 nm meridional X-ray diffraction reflection during length changes of intact frog muscle fibres.

The intensity of the 14.5 nm meridional reflection (M3) from activated skeletal muscle fibres was studied in both single fibres and fibre bundles during the imposition of length changes. During shortening at small load, the intensity of the reflection decreased within 2 ms to less than 20% of isometric intensity, then recovered partially during the remainder of the shortening. When shortening was terminated, recovery of intensity was delayed. Small shortening steps (0.5% fibre length) produced a fall in M3 intensity (IM3) delayed by ca. 250 microseconds compared to the fall in tension. For larger step releases (1% fibre length), the fall in IM3 was not delayed. The fall in IM3 could be almost completely reversed by a subsequent restretch applied within 1.5 ms. Beyond 10 ms after the initial release, the restretch caused a further fall in intensity. A rapid step stretch (0.5% fibre length) also caused a fall in IM3 without delay, which was partially reversed by a release applied within 10 ms. A second small release applied 3 ms (or less) after the first caused a second fall in M3 intensity, but without delay and with faster time course. Small amplitude sinusoidal length oscillations (0.15-0.2% sarcomere; 1 kHz) caused a sinusoidal change in M3 intensity, which was 180 degrees out of phase with the force oscillations, and lacked distortion during its release phase.

Optical design of a free-space photonic switching system

The optical design of a photonic switching system is described in detail. The system is a 4-f imaging system with one lens design based on a Petzval lens and the second lens design based on a double Gauss lens. The assembled system is 60 mm x 70 mm x 370 mm and features a single imaging stage, pupil division for beam combination, and a single fiber bundle for both input and output. A brief description of the system requirements is provided, and the implication of some of these requirements for the paraxial design is explained. The choice of design forms for the lenses is explained, the design process is outlined, and the final lens designs are provided. Lens tolerancing is outlined and the final lens tolerances are provided. Finally, the assembly and the alignment processes are described.

Interface reactions and fracture behaviour of fibre‐reinforced Mg/Al alloys

In the composite system carbon fibre/magnesium alloy the interface reactivity was varied over a wide range by adding different amounts of the alloying element aluminium (alloys: AM20, AZ91) and by using carbon fibres of different surface properties (fibres: M40J, T300J). The structure and composition of interlayers in these composites down to the atomic scale as well as their effect on the mechanical properties were studied systematically by the combination of high‐voltage electron microscopy, high‐resolution electron microscopy, energy‐dispersive X‐ray spectroscopy and electron energy‐loss spectroscopy with scanning electron microscope in situ bending tests. As resulting microstructure and nanochemistry correlate with the micromechanical fracture behaviour of the metal matrix composites, the interface reactivity can be used as a parameter governing the composite properties.In addition to precipitates of aluminium carbide, strongly influencing the fracture behaviour, there are also graphitic carbon ribbons and layers of nanocrystalline magnesium oxide at the fibre/matrix interface.Increasing the reactivity of the composite system, three characteristic modes of fracture behaviour are observed: single fibre pullout, bundle fracture (the optimum composite) and brittle failure.

Cross-bridge movement in rat slow skeletal muscle as a function of calcium concentration.

A single fibre bundle from rat soleus muscle was chemically skinned with saponin and the transfer of myosin heads from the thick filaments to the thin filaments at a sarcomere length of 2.4 microm was measured as a function of Ca2+ concentration using an x-ray diffraction method at 4-7 degrees C. In the relaxed state, the 1,0 spacing was 42.08 nm. The spacing showed no significant decrease when the Ca2+ concentration was below the threshold (-log10 [Ca2+] or pCa 5.8). No significant transfer of the myosin heads occurred when the Ca2+concentration was below the threshold (pCa 5.8). When the muscle was maximally activated at pCa 4.4, the spacing decreased to 40.35 nm. During the maximum isometric contraction at pCa 4.4, 54. 9 +/- 6.5% (+/-SE of the mean) of the myosin heads were transferred to the thin filaments. The transfer of the myosin heads was approximately proportional to relative tension. These results suggest that myosin heads of both fast-twitch and slow-twitch skeletal muscles transferred on the common movement as a function of Ca2+ concentration.

The tensile strength of hybrid fibre composites: a probabilistic analysis of the hybrid effects

A hybrid composite formed by brittle and less brittle fibres embedded into a ductile matrix is taken as the model for study. The breaking strains of distinct fibre types in the hybrid composite are considered in this paper as statistical variables so that the stress-strain relationship of the composite is treated as a typical stochastic process indexed with the composite strain. Also the mechanism reflecting the interactions between the constituents revealed by the fragmentation process during composite extension, and the effect of breaking strain variation between individual fibres of the same type have been included in the stochastic formula. Based on this theo­retical model, the prediction of the entire stress-strain curve of a hybrid composite is provided in this study. A comprehensive parametric study is then carried out to illustrate the inter-relationships between the composite breaking behaviour and the fibre and composite interfacial properties. Next, as the hybrid effect is defined by comparing the hybrid composite either with the rule of mixtures using single fibre properties or fibre bundle properties, or with a non-hybrid composite, the differences in these cases are discussed in detail. Various sources causing the hybrid effect are revealed, studied and summarized. These sources are found due partly to the property variations of the fibres which affect the interactions in the hybrid composite between fibres and matrix, and partly to the cross coupling interactions between the fibres of different types in the hybrid composite. The impacts of these sources on the composite behaviour as well as the associated hybrid effects are demonstrated and the important factors are detected and examined. It is then stressed in this paper that since most of the mechanisms responsible for causing the so-called hybrid effects have been proved effective in non- liybrid composites as well, we need to be more cautious concerning the definition for the hybrid effects in a hybrid composite. Finally, the relationships between the hybrid effects and the important variables such as the relative hybrid ratio, a LE the relative fibre-matrix interface shear strength T y /E f , and the relative fibre tensile modulus Ef HE E/ fLE are investigated and illus­trated.

Nerve fibres in urothelium and submucosa of neuropathic urinary bladder: an immunohistochemical study with S-100 and neurofilament.

Intravesical administration of drugs has been used commonly in spinal cord injury patients to suppress detrusor hyperreflexia (eg oxybutynin, verapamil, terodiline) or, to initiate a micturition reflex (eg 15S 15-methyl prostaglandin F2 alpha, protaglandin E2); however, the response has been variable and sometimes, unpredictable. This prompted us to study the presence of nerve fibres in the vesical urothelium and submucosa in mucosal biopsies taken from the dome and trigone (obtained prior to performing a therapeutic procedure eg, vesical lithotripsy, or a diagnostic cystoscopy) in 47 consecutive, unselected paraplegic/tetraplegic patients with a neuropathic urinary bladder. Nerve fibres were demonstrated by routine immunohistochemical technique using commercially available monoclonal and polyvalent antibodies against S-100 (DAKO A/S, Glostrup, Denmark) and Neurofilament (MILAB, Malmo, Sweden). Biopsy specimens were graded for the presence of nerve fibres on a 0-3 scale for urothelium, and superficial/deep submucosa separately in a blind and randomised manner. Virtually no fibre presence was found in one paraplegic patient and no superficial or single fibres were noted in a tetraplegic patient. Absence of C-fibre hyperplasia (Grade 0) was found in nine cases (paraplegic: 4; tetraplegic: 5); Grade 1 hyperplasia was observed in 17 cases (paraplegic: 4; tetraplegic: 13); Grade 2 hyperplasia was seen in 11 cases (paraplegic: 7; tetraplegic 4); and Grade 3 hyperplasia was noticed in eight cases (paraplegic 3: tetraplegic: 5). The magnitude of C-fibre hyperplasia was not significantly different between paraplegic and tetraplegic patients (chi(2) = 4.64; P = 0.3262). The relationship, if any, between the degree of C-fibre hyperplasia and duration of paralysis was studied by categorising patients as < 5 years, and > 5 years of paralysis. No evidence of single fibre or fibre bundle hyperplasia (Grade 0) was seen in five and six cases, grade 1 hyperplasia in six and 11 cases, grade 2 hyperplasia in two and nine cases, and grade 3 hyperplasia in three and five cases respectively in these two categories of patients. (chi(2) = 1.92; P = 0.58). The possible relationship between C-fibre hyperplasia in the vesical mucosa/submucosa and (i) the vesical response to intravesical drug administration; (ii) the vesical urothelial proliferation arrest; (iii) the electrical stimulation of urinary bladder by implanted electrodes (sacral anterior root stimulator); and (iv) long-term indwelling urethral Foley catheter drainage, are discussed with illustrative case reports. In conclusion, mucosal biopsy and study of nerve fibres in urothelium and submucosa of neuropathic bladder has helped to generate hypotheses on the association between C-fibre hyperplasia and response to intravesical pharmacotherapy and the predictive value of such a study in identifying those patients who are likely to respond to intravesical pharmacotherapy.

A New Approach Towards Defibrillation Electrodes: Highly Conductive Isotropic Carbon Fibers

A new carbon fiber material was studied for its potential benefit in defibrillation electrodes. Miniaturization of the fiber production can result in small strands with extremely large surface areas. Two carbon fiber patches and a single carbon fiber bundle were used for the purposes of this study, and the results were compared to those obtained with conventional titanium/mesh patch electrodes. Tests performed in a saline filled tank revealed considerably lower resistances through the carbon material when compared to standard mesh electrodes. There was also a higher peak current flow with lower voltage. The carbon fibers exhibited lower impedance for defibrillation and this may be related to low polarization known to occur with carbon materials. This new carbon material may prove to be useful and further research is required.