Fibers and Fiber Bundles

Tiny yet tough: Maximizing the toughness of fiber-reinforced soft composites in the absence of a fiber-fracture mechanism

The use of plant fibres in composite applications requires an efficient characterisation of their mechanical properties and thus an accurate description of their internal structure. The review of literature points out that there is still a lack of data on the organisation and structure of bast fibres. In this study, we propose to investigate the internal structure of hemp fibres using two experimental techniques: Focused Ion Beam (FIB) microscopy and optical coherence tomography (OCT). Results indicate that OCT, a non-destructive and non-invasive technique, is a powerful technique to quickly and easily describe the internal structure of fibres and also to discriminate single fibres from bundle of fibres. In this paper, we also show that among technical hemp fibres and for a same range of external diameters (of about 20–30 μm), two types of internal structures can be observed: (i) elementary fibres with a thick wall and a small lumen and (ii) bundle of small fibres with an external diameter of a few microns. According to data of literature, these two structures were identified as being respectively primary fibres and bundle of secondary fibres. This result is of great importance for the mechanical characterization of the bast hemp fibres. Indeed, this means that during the test campaigns, the batch of isolated fibres is undoubtedly composed of both single primary fibres and bundle of secondary fibres. It certainly participates to the high scattering in results.

Load-sharing and Monte Carlo models of defects in a bundle of fibres

This study deals with the prediction of the mechanical properties of wool bundle fibers and the characterization of the fracture performance of fiber fracture sound. Acoustic emission detection was used to record the fracture sound of wool fibers. According to the fracture sounds, the tensile properties of the bundle fibers were obtained. Acoustic emission provided a convenient method for obtaining fibers breaking elongation distribution. Based on the fiber bundle model and fiber breaking distribution, the fracture strength and elongation of bundle fibers could be predicted. Meanwhile, based on the correlation between the amplitude of fiber fracture sound and fiber breaking strength, the single fiber breaking strength could be predicted and the tensile properties of bundle fibers could also be obtained. The prediction results based on bundle fiber fracture sound were more similar to the measured results. Besides, the number of fibers within the bundle increased, the fiber interaction was also enhanced, and the bundle fiber strength prediction results were affected. This work was considered to have the potential of being used in the prediction of mechanical properties of natural fiber composites.

The scope of the investigations of the paper includes the efficiency in the prediction of strength characteristics of the ablating polymer unidirectional carbon-fiber-reinforced plastics at elevated temperatures based on the properties of the unreinforced matrix and a bundle of fibers in the process of thermal oxidative breakdown at different types of stress state. The characteristics of elasticity and parameters of strength of the transverse-isotropic carbon-fiber-reinforced plastic, as well as of its components (epoxy matrix and carbon fibers of T700 type), have been determined in compliance with the regulatory documents of Ukraine at low heating rates with the subsequent exposure of the specimens at the fixed temperature, when the inertia effects can be neglected. It is illustrated that the variation in densities of the ablating unreinforced matrix and the bundle of fibers at elevated temperatures is rather well described via the models of multiphase media employing the modified integral exponential function. The authors analyze the possibility to evaluate the critical stresses of the transverse-isotropic composite at elevated temperatures based on the mechanics of multiphase media considering the thermal and mechanical characteristics of the ablating polymer matrix and the bundle of carbon fibers. It is assumed that the task of heat and mass transfer can be solved separately from the coupled tasks of thermal mechanics of the ablating materials since mechanical stresses have no effect on its parameters. It is found that the calculation of critical stresses using the hypothesis for the total hermetic sealing between the phases or in the assumption on the low pressure in pores determines the lower and upper lines of variation of the composite strength at different types of stress state. In particular, the calculated strength of the unidirectional composite under tension in the transverse direction and in shear along and across the fibers is in good correlation with the experimental data obtained by the authors and other researches.

A stratified bundle is a fibered space in which strata are classical bundles and in which attachment of strata is controlled by a structure category F of fibers. Well known results on fibre bundles are shown to be true for stratified bundles; namely the pull back theorem, the bundle theorem and the principal bundle theorem. AMS SC : 55R55 (Fiberings with singularities); 55R65 (Generalizations of fiber spaces and bundles); 55R70 (Fiberwise topology); 55R10 (Fibre bundles); 18F15 (Abstract manifolds and fibre bundles); 54H15 (Transformation groups and semigroups); 57S05 (Topological properties of groups of homeomorphisms or diffeomorphisms).

Thailand has a huge variability of bast fiber plants, some of which have been little researched regarding their applicability in composites. Bast fiber(bundle)s from different species were investigated and incorporated into a polylactide (PLA) matrix by injection molding. Hemp and kenaf were used as well-studied fibers, while roselle, Fryxell and paper mulberry are less extensively characterized. Tensile strength, tensile modulus and interfacial shear strength (IFSS) of single fiber(bundle)s were highest for hemp, followed by kenaf, roselle, Fryxell and paper mulberry. Despite the lower tensile strength and IFSS of paper mulberry, the highest tensile strength was achieved for the paper mulberry/PLA composite followed by hemp/PLA. Scanning electron microscope (SEM) analyses showed that the single cells in paper mulberry fiber bundles, in contrast to the other fiber types investigated, were only partially bonded to each other, which explains the lower strength of the fiber bundles. The higher aspect ratio of fiber(bundle)s of paper mulberry in the PLA composite can explain the good composite characteristics. Apart from hemp, paper mulberry shows the best reinforcing effect in the PLA matrix and offers interesting potential for composite applications. Compared to neat PLA, the tensile strength could be increased by 24% and the tensile modulus by 54%.

BackgroundThis study aimed to clarify the morphological characteristics of the Lisfranc ligament and the cuneiform 1-metatarsal 2&3 plantar ligament (CMPL).MethodsForty legs from 20 cadavers were examined. Classification proceeded according to the number of fiber bundles in the Lisfranc ligament and the CMPL. Morphological features measured were fiber bundle length, width, thickness, and angle.ResultsIn Type I-a, the Lisfranc ligament and the CMPL were a single fiber bundle; in Type I-b, the Lisfranc ligament was a single fiber bundle, and the CMPL was two fiber bundles; in Type II-a, the Lisfranc ligament was a two fiber bundle, and the CMPL was a single fiber bundle; in Type II-b, the Lisfranc ligament and the CMPL were two fiber bundles; in Type III-a, the Lisfranc ligament was three fiber bundles, and the CMPL was a single fiber bundle; in Type III-b, the Lisfranc ligament was three fiber bundles, and the CMPL was two fiber bundles; in Type IV, the Lisfranc ligament and the CMPL could not be separated. Type I-a was seen in 37.5%, Type I-b in 10%, Type II-a in 30%, Type II-b in 7.5%, Type III-a in 7.5%, Type III-b in 2.5%, and Type IV in 5%. The Lisfranc ligament was significantly larger than the CMPL in total fiber bundle width, total fiber bundle thickness, and total fiber bundle angle.ConclusionThe Lisfranc ligament had up to 3 fiber bundles and the CMPL had one or two fiber bundles; classifications were four types and two subgroups.

Gypsum plaster composites reinforced with tropical fibre bundles extracted from Rhecktophyllum camerunense and Ananas comosus plants: Microstructure and mechanical performance

Morphological features of the anterior talofibular ligament by the number of fiber bundles

Comparative mechanical and thermal study of chemically treated and untreated single sugarcane fiber bundle

Light and X-ray scattering on the same primate and human brain samples cross-validate each other and enable accurate mapping of axonal trajectories in regions with uni- and multi-directional nerve fibers, which can be used to validate diffusion MRI.

Light and X-ray scattering on the same primate and human brain samples cross-validate each other and enable accurate mapping of axonal trajectories in regions with uni- and multi-directional nerve fibers, which can be used to validate diffusion MRI.

Flexible infrared image fiber bundles (FBs) are capable of delivering thermal images of areas that are difficult for ordinary thermal cameras to access while making the imaging systems compact and lightweight. Thus, FB-based thermal imaging systems show great potential in some important applications, such as infrared endoscopy, aircraft infrared warning, and satellite remote sensing. In most applications, FBs are required to have high overall transmittance (OT) and high spatial resolution (R), but the fabrication of such high-performance FBs is still a challenge. In this work, we demonstrate a new design of flexible mid-wave infrared chalcogenide FB with high OT and decent R by optimizing the composition of glass cladding and geometric parameters of single fibers. The FB is fabricated by a modified approach combining the stack-and-draw technique and layer-stacking method, and the thermal image delivery performance of the FB is comprehensively characterized. It is shown that the core diameter (d core) and core/cladding diameter ratio (R cc) of single fibers can be balanced to reduce leakage of the light propagating in the single fibers while making the FB retain a reasonably high filling factor. Thus a high-performance FB can be achieved. The fabricated FB consists of 124,200 single fibers featuring an As40S60 core, an As38.9S61.1 cladding, and a polyetherimide (PEI) protective coating, with a dcore of ∼22.8 µm and an Rcc of 0.8. It has a length of ∼52 cm and a filling factor of ∼50.2%. The FB presents excellent thermal image delivery performance, including an OT of 40.5%, a single-fiber loss of 1.71 dB/m at 4.6 µm, and an R of 20.2 lp/mm, which compares favorably to previously reported FBs. These findings provide new insights for the development of high-performance thermal imaging FBs and lay a foundation for their practical applications.

In this study, we investigated the improvement in carbon fiber (CF) bundle tensile tests. To effectively evaluate the mechanical properties of CF using the fiber bundle tensile test, measurement of system elongation correction considering nonlinear behavior and Weibull analysis using fitting of stress–strain curves was conducted. Shear-lag theory analysis revealed that the elongation in the nonlinear measurement system was largely governed by the adhesive layer deformation within the tabs. A nonlinear measurement elongation correction method was proposed that can be applied to specimens of different widths. Weibull parameters were extracted by fitting the stress–strain curves, while considering the effect of the kinetic frictional force. The obtained parameters from the fiber bundle tensile test corresponded to those obtained from the SFTT. Thus, the proposed fiber bundle test can be a simple method for evaluating fiber strength distribution.