Fiber Geometry Research Articles

Application of X-ray Computed Tomography to Measuring Fiber Orientation Distribution of Chopped Carbon Fiber Tape Reinforced Thermoplastics

Evaluating the internal geometry of carbon fiber reinforced plastics is important to predict its mechanical properties and fracture behavior. In this study, we employed two different commercially available image processing software – AVIZO and 3D-Bon to analyze the fiber orientation distribution (FOD) of the chopped carbon fiber tape reinforced thermoplastics (CTT) by processing the imaged volume observed from an X-ray computed tomography (CT) system. To clarify the capability of the CT observation and subsequent analysis, the elastic modulus of CTT was estimated analytically based on the FOD data. Meanwhile, the experimental results were selected as the reference value for qualification. The local FOD, which was obtained from an individual observation, presented local anisotropy and stochastic dispersion of the fiber strands, while we found that the representative FOD of CTT can be acquired by performing CT observation and analysis on more than 15 samples. The statistical analysis and cross section observation were performed to validate the reliability of multi-sample observation.

Butt-Coupling of 4.5 μm Quantum Cascade Lasers to Silica Hollow Core Anti-Resonant Fibers

We report on experimental characterization of butt-coupling between a quantum cascade laser operating around the wavelength of 4.5 μm and a silica hollow core anti-resonant fiber. The used fiber has a single ring of non-touching capillaries surrounding a 42.5 μm dimeter air core and a mid-infrared transmission window in the wavelength range of 2.8 to 4.7 μm. A lens-less butt-coupling interconnection is established and coupling efficiency of 22% is achieved with over 100 mW of power at the fiber output. Bending losses in this test-bed system are verified depending on radius with the loss remaining below 1 dB/m for 20 mm loops, while bend losses exceeding 10 dB/m are observed when the fiber is bent down to a 5-mm radius. The presented coupling dramatically improves the output beam quality of the quantum cascade laser with a measured NA = 0.45. The beam at the fiber output has a circular shape, measured M <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 1.04 and uniform numerical aperture of NA = 0.13. Together with the hollow core fiber geometry, the proposed system would be suitable for simple implementations of absorption spectroscopy of popular atmospheric agents, like N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O.

Polyelectrolyte Complex Tubular Membranes via a Salt Dilution Induced Phase Inversion Process

Tubular membrane geometries are key elements of many industrial filtration applications and artificial organs. Established processes to fabricate polymeric membranes require the use of organic solvents, which are prone to be phased out due to stricter regulations. In the quest of developing solvent‐free alternative fabrication processes, polyelectrolyte complex (PEC) membranes are recently discovered, offering a promising alternative. While flat sheet PEC membranes are successfully fabricated, tubular or hollow fiber geometries remain a material engineering challenge. For the first time, the organic solvent‐free fabrication of PEC tubular membranes in a dry‐jet wet spinning process is demonstrated. The aqueous polymer solution comprising the polyanion—poly(sodium‐4‐styrenesulfonate) (PSS), the polycation—poly(diallyldimethylammonium‐chloride) (PDADMAC), and KBr is extruded with the water‐based bore fluid through a single‐orifice spinneret, passing an air‐gap before immersed into an aqueous coagulation bath. The phase inversion kinetics are influenced to form a defect‐free lumen separation layer through the addition of glycerol to the bore fluid. The resulting tubular membranes show reproducible nanofiltration membrane properties. They have a molecular cut‐off of 320 Da, are positively charged and retain salts with a characteristic salt retention hierarchy. This promising material engineering strategy motivates to continue the quest for smaller tubular dimensions toward hollow fibers.

Functionalized Fiber Reinforced Composites via Thermally Drawn Multifunctional Fiber Sensors

AbstractMonitoring fiber reinforced polymer composites (FRPC) during their production and operation is becoming crucial to track the performance of the final parts and optimize the overall life cycle. The challenges associated with integrating multifunctional sensors with the required aspect ratio, manufacturing scalability, robustness, and performance within FRPC parts remain, however, unresolved. Here, a novel class of electronic polymer fiber sensors that can be seamlessly integrated within FRPC, and can sense and decouple cure time, temperature, and strain during and postprocessing is reported. It is shown that the particular fiber geometry induces a minimal impact on the final FRPC microstructure. Integrating both capacitive‐ and resistive‐based sensors within the electronic fibers, the monitoring of the resin flow and its curing during the production of FRPC parts is demonstrated. Finally, the embedded fiber sensors are used to measure and decouple thermal and mechanical loads imposed on the parts during their use, paving the way toward a new platform for smart and connected fiber reinforced polymer composites.

Reventing brittle hybrid high-strength reinforced concrete slab collapse due to punching shear using coal flyash substitution, tie wire fiber and polypropylene fiber

Heavy vehicles crossing a bridge could lead in punching shear failure at reinforced concrete deck slab due to highly concentrated axial compressive load from their wheels. This may occur in a very brittle manner and difficult to fix. Effort in improving punching shear capacity of deck slab is with using high-strength concrete and adding fibers into concrete. However, high-strength concretes are not environmentally friendly because using a lot of cement contributing to large CO2 emissions to the atmosphere during its production, therefore coal flyash is used as a part of cement substitution. Based on these facts, this research aims to analyze punching shear capacity of hybrid high-strength reinforced concrete slabs using coal flyash as cement substitution which added with tie wire fiber and polypropylene fiber. The amount of coal flyash was taken 15% from cement weight as cement substitution, tie wire fiber 2% from concrete volume having aspect ratio l/d of 40 and straight shaped fiber geometry, as well as polypropylene fiber 0.2% from concrete volume. Three hybrid high-strength reinforced concrete slabs of 60 × 60 cm2 (two-way-slab) with a thickness 12 cm, w/c-ratio of 0.30 and concrete cylinder compressive strength of f′c = 60 MPa were made with 15% coal flyash and 2% tie wire fiber (CFA-TWF), 15% coal flyash and 0.2% polypropylene fiber (CFA-PPF), as well as 15% coal flyash and combination of 2% tie wire fiber and 0.2% polypropylene fiber (CFA-TWF-PPF). One plain slab without flyash and fibers (PSHSC) was tested as a comparison. To guarantee the punching shear failure mechanism, the slabs were reinforced with tensile reinforcement of 10 Ø 10.5 mm which was distributed to each direction and tested then by giving a concentrated punching load. The results showed that using of coal flyash substitution and addition of fibers could significantly increase the punching shear capacity and structural ductility of hybrid high-strength concrete slabs with the highest enhance both achieved in CFA-TWF-PPF, i.e., 67.91% for punching shear capacity and 92.82% for structural ductility compared with plain slab PSHSC.

A twist sensor based on polarization-maintaining fibers with different cladding diameters

A fiber twist sensor using a Sagnac interferometer incorporating a tapered polarization-maintaining fiber (PMF) is proposed. The transmission properties of the sensor are investigated both theoretically and experimentally. Given the optoelastic effect, which depends on fiber geometry, the modal and group birefringences of the PMF can be controlled by applying different twist angles. The spectral wavelength shifts, free spectral ranges, and transmission losses of the original, microtapered, and etched PMFs were compared. Notably, the interference dips for the etched PMF move in opposite directions. As a result, the proposed PMF-based sensor could have multiparameter sensing applications.

Bridging the gap between lab-scale and commercial dimensions of hollow fiber nanofiltration membranes

The development of nanofiltration membranes with hollow fiber geometry is a relatively young field of research in membrane science with only limited, but quickly growing, availability on a commercial scale. These membranes offer promising properties for application in water treatment such as high fouling resistance and low cost compared to Reverse Osmosis membranes. Major differences are found in dimension and operating conditions of hollow fiber nanofiltration membranes used in academia and on an industrial scale. To allow for adequate comparison and prediction of membrane performance, the effect of fiber dimension and operating conditions on process performance needs to be properly understood. A systematic experimental study on MgSO4 retention by hollow fiber nanofiltration membranes was performed to investigate the effect of fiber length and operational conditions on membrane performance. A significant drop in the retention of MgSO4 was observed for 1.5 m long fibers in flux ranges of 20 LMH when reducing crossflow velocity to 0.1 m/s. Transport models were used to describe and predict this behavior. We show that the commonly used mass transport models under predict this decrease in retention. Using different theoretical transport models for the hollow fiber feed phase and reducing dimensional resolution from 2D to 1D and 0D allows for the identification of limitations of the commonly applied analytical mass transfer correlations. To accommodate for this discrepancy found between experimental results and model predictions, a correction factor was derived using the 2D model to specifically account for deviations of these correlations at high permeate recovery values. Our newly developed model makes it possible to accurately predict full scale membrane performance solely based on measured done on small scale membranes, an important precondition for the further development of dense hollow fiber based membranes and processes.

A loading assisted diffuse wave inspection of delamination in a unidirectional composite

Delamination localization and characterization are critical for the structure integrity of fiber reinforced polymer composites with various fiber distributions and geometries. Different to direct wave based methods, the diffuse wave inspection is promising for rapid structure interrogation with only a few ultrasonic transducers required. The angle dependant diffusivity and dissipation are first measured in a unidirectional composite plate manufactured from hot press. Both coefficients represent an orthotropic behavior and can be predicted through rotation matrix calculation. 27% signal energy variation is found between the 0.1 mm thick delamination zone and the intact zone. The measurement along the fiber direction gives the best signal-to-noise ratio among all directions. No coefficient difference exists under amplitude normalization. A compressive loading is then applied to have different acoustic responses from different zones. Based on the acoustoelastic effect, the decorrelation coefficient variation is negligible in the intact zone with the strain of 10−3. Similar to the clapping effect, the loading triggered decorrelation coefficient variation becomes important as the transducer pairs approach the delamination zone. This has also been validated by the energy variation method. In addition, when the loading is centered in the delamination zone, the decorrelation coefficient variation area that can be captured by the diffuse wave is 45 × 210 mm2. Based on the Locadiff imaging method, the delamination geometry is finally characterized through Bayesian inference together with the numerical defect sensitivity kernel and the decorrelation coefficients. According to this loading-delamination-diffuse wave interaction analysis, the loading unveiled delamination geometry is found to center at [146,138] mm with an area of 3.5 × 10−4 ~ 11 × 10−4 m2 compared to the ground truth of [145,150] mm and 5.2 × 10−4 m2 respectively. It is promising for early-stage defect inspection in advanced composite structures.

Synchrotron X-ray metrology of dopant distribution and oxidation state in high pressure CVD grown TM2+:ZnSe optical fibers

High pressure chemical vapor deposition (HPCVD) has shown to be a promising method for producing Cr2+:ZnSe and Fe2+:ZnSe mid-IR optical fiber lasers. The oxidation state of the dopants and their spatial homogeneity are critical for the characterization of effective fiber laser performance; however, this is challenging for small fiber cores and small doping concentrations. We demonstrate using synchrotron micro X-ray fluorescence (XRF) mapping to study the distribution of the dopants throughout the fiber cross-sections. Furthermore, we study the local chemical environment of these unique fiber structures using micro X-ray near edge absorption spectroscopy (XANES). Our study reveals that transition metal doped ZnSe deposited using HPCVD has nanoscale dopant aggregation although the material is chemically identical to the commercially produced diffusion doped laser crystals, as indicated by the presence +2 oxidation state of the dopants. This work demonstrates the power of synchrotron-based X-ray techniques for use as metrology tools for improving the performance of laser materials in fiber geometry.

Dynamics of drop absorption by a swelling fiber.

Swelling of individual fibres exposed to a favorable solvent may affect the mechanical properties or shape of a fibrous material. We provide experimental results of the absorption dynamics of a single drop deposited on a swellable fibre and show that the total absorption time is highly dependent on the fibre geometry and drop volume. The curvature of the fibre prevents the total spreading of a drop even if the fluid is fully wetting the fibre. For drops larger than a critical volume, a local saturation of the fibre is thus reached below the drop, leading to a strong increase in the total absorption time. These observations are then rationalized with a simple pseudo-diffusive model to understand the drop absorption and fibre swelling dynamics. This minimal model provides quantitative predictions of the total absorption time.

Influences of nylon fiber geometries and contents on mechanical behavior of reinforced mortar

Used nylon fishing nets were utilized as recycled nylon (RN) short fibers for reinforcing cement mortar. Fishing nets were cut into specified shapes and lengths, then mixed into mortar. In this study, the influences of fiber geometries such as diameter, aspect ratio and the fiber content on the me chanical properties of mortar were emphasized. Changes in flowability of fresh mortar, compressive strength, flexural strength, failure behavior, flexural toughness, residual strength factors were experimentally investigated and compared among various mixes. Experimental results indicated that fiber geometries as well as fiber content directly affect the mechanical properties of mortar. Adding fibers was found to reduce flowability and compressive strength of the mortar. For instance, using sharp-shapes reduced compressive strength by 41% while using cross-shapes improved flexural strength by 44.5%. Improvement in flexural strength and flexural toughness were found in association with the fiber content. RN fiber contributes to the post-peak loading capacity and prevents abrupt failure of concrete structures.

K3 mirror symmetry, Legendre family and Deligne's conjecture for the Fermat quartic

In this paper, we will study the connections between the mirror symmetry of K3 surfaces and the geometry of the Legendre family of elliptic curves. We will prove that the mirror map of the Dwork family is equal to the period map of the Legendre family. This result provides an interesting explanation to the modularities of counting functions for K3 surfaces from the mirror symmetry point of view. We will also discuss the relations between the arithmetic geometry of smooth fibers of the Fermat pencil (Dwork family) and that of the smooth fibers of the Legendre family, e.g. Shioda-Inose structures, zeta functions, etc. In particular, we will study the relations between the Fermat quartic, which is modular with a weight-3 modular form η(4z)6, and the elliptic curve over λ=2 of the Legendre family, whose weight-2 newform is labeled as 32.2.a.a in LMFDB. We will also compute the Deligne's periods of the Fermat quartic, which are given by special values of the theta function θ3. Then we will numerically verify that they satisfy the predictions of Deligne's conjecture on the special values of L-functions of critical motives.

The effect of metallic fiber geometry and multi-walled carbon nanotubes on the mechanical behavior of aluminum fiber-reinforced composite adhesive joints

The effect of the geometry of metallic fibers on the mechanical response of aluminum fiber-reinforced composite adhesive joints was studied experimentally. Moreover, a combination of multi-walled carbon nanotubes and aluminum fibers was used for reinforcing the composite adhesive joints. Different geometries for the aluminum fibers including straight, twisted and spring-shaped with different pitch lengths were considered. The results indicated that the composite adhesive joints reinforced with a combination of multi-walled carbon nanotubes and aluminum fibers experienced the highest improvement of 171% in the strength compared to the unreinforced specimen. It was found out that the aluminum fiber geometry can significantly influence the adhesive joint behavior. Incorporating the twisted aluminum fibers into the adhesive layer increased, while the spring-shaped fibers decreased the strength of the composite adhesive joints compared to the straight aluminum fibers. The fracture surfaces of the composite adhesive joints were analyzed using scanning electron microscope.

Designing tunable narrowband parametric source in Chalcogenide-based dynamic fiber geometry

We numerically investigate the generation of spectrally isolated narrowband tunable parametric sources by continuous-wave pumping a specially designed gelatin-coated chalcogenide-silica dynamic fiber in the normal dispersion regime. The relative humidity (RH) dependent phase matching dominated by fourth order dispersion has been exploited for the first time, to the best of our knowledge, to produce far-detuned new wavelengths. A tunable source in the range of 0.96–2.5 μm with a tuning rate of 1.3 THz/%RH has been designed by milliwatt pumping a 30 cm long fiber at 1.395 μm. Additionally, the sideband tailorability of about 50 THz close to the visible band was achieved by selectively exciting higher-order fiber modes (HE21) in the anomalous dispersion regime at 0.91 μm. We emphasize that the parametric sources from the proposed host would be extremely useful in short-wave infrared spectroscopy and biomedical applications.

Modelo mecánico para la resistencia a cortante de vigas de hormigón armado reforzado con fibras, sin armadura de cortante

Es bien conocido que la adicion de fibras de acero mejora la resistencia a cortante y ductilidad de las vigas de hormigón armado. Sin embargo, a pesar de los numerosos estudios existentes, las normativas y recomendaciones de diseño se basan en modelos empiricos que presentan mucha dispersion cuando se comparan sus resultados con los de ensayos. Ello es fundamentalmente debido a las incertidumbres asociadas al comportamiento del hormigon con fibras debido a la orientcion, ditsribucion y adherencia de las fibras con el hormigón, entre otros factores. Por ello, la caracterizacion del hormigon con fibras se asocia a parametros de ensayos a flexión, a pesar de que las tensiones post-fisuracion obtenidas no son directamente utilizables como tensiones transmitidas a través de la fisura crítica. Por otra parte, la mayoría de los ensayos existentes no disponen de estos parametros experimentales. Por ello se detecta la necesidad de disponer de modelos mecánicos (no empíricos) que partan de los parametros usados en el dise´ño del hormigón con fibras (tipo, geometria y cuantia de las fibras, etc)&#x0D; A tal fin, en esta ponencia se presenta un modelo mecánico de resistencia a cortante, obtenido extendiendo el modelo "Multi-Action Shear Model" previamente desarrollado en las universidades UPC y UIB, incorporando los efectos de las fibras , tanto a puenteando la fisura crítica como aumentando la resistencia de la cabeza de compresión. Por otra parte, la tension residual a través de la fisura crítica se obtiene mediante una formulación desarrollada en funcion de las caracteristicas de las fibras (geometria, forma, caracteristicas de adherencia, volumen de fibras) y de la resistencia a traccion del hormigón. Los resultados del modelo, comparados con los de 488 tensayos a cortante incluidos en una reciente base de datos de vigas de hormigon con fibras, sin cercos, han mostrado una dispersión menor que cualquiera de los modelos existentes hasta el momento, siendo por tanto muy adecuado (por sencillez y precision) para el diseño de estas estructuras.

GLS-Se optical fibre from extruded glass structured preforms and rods for the IR region

Depending on composition, chalcogenide glasses have been proven as a reliable medium to transmit light in the range from the visible to the long-wave infrared (LWIR), specialty glasses based on gallium lanthanum sulfide (GLS) with a selenium (Se) addition. This family of glasses offers a broad transparency window depending on the composition. Their optical, mechanical, and thermal properties have been exploited in their bulk form. In this paper, we demonstrate the fabrication of optical fibres from extruded structured (core-clad) preforms and rods, with an emphasis on maintaining the intrinsic characteristics of the glass and exploiting the optical fibre geometry for light delivery.

Structural plasticity of the avian pectoralis: a case for geometry and the forgotten organelle.

The avian pectoralis muscle demonstrates incredible plasticity. This muscle is the sole thermogenic organ of small passerine birds, and many temperate small passerines increase pectoralis mass in winter, potentially to increase heat production. Similarly, this organ can double in size prior to migration in migratory birds. In this Commentary, following the August Krogh principle, I argue that the avian pectoralis is the perfect tissue to reveal general features of muscle physiology. For example, in both mammals and birds, skeletal muscle fiber diameter is generally accepted to be within 10-100 µm. This size constraint is assumed to include reaction-diffusion limitations, coupled with metabolic cost savings associated with fiber geometry. However, avian muscle fiber structure has been largely ignored in this field, and the extensive remodeling of the avian pectoralis provides a system with which to investigate this. In addition, fiber diameter has been linked to whole-animal metabolic rates, although this has only been addressed in a handful of bird studies, some of which demonstrate previously unreported levels of plasticity and flexibility. Similarly, myonuclei, which are responsible for protein turnover within the fiber, have been forgotten in the avian literature. The few studies that have addressed myonuclear domain (MND) changes in avian muscle have found rates of change not previously seen in mammals. Both fiber diameter and MND have strong implications for aging rates; most aging mammals demonstrate muscular atrophy (a decrease in fiber diameter) and changes in MND. As I discuss here, these features are likely to differ in birds.

Mathematical modeling of CO2 separation using different diameter hollow fiber membranes

This research presents a 2D mass-transfer simulation model using computational fluid dynamics (CFD) for separation of CO2 from a binary gas mixture of CO2/CH4 by means of polytetrafluoroethylene (PTFE) hollow fiber membrane contactor (HFMC). Governing equations with their corresponding boundary conditions are solved using COMSOL Multiphysics and the results are validated against reported experimental data. Convection and diffusion flux vectors and concentration gradient of CO2 species in the radial and axial directions of the HFMC are investigated. This study provides an opportunity to investigate the effects of gas and liquid cross flow velocities on the overall performance of membrane contacting system. The results demonstrate that increasing the liquid phase velocity improves the CO2 absorption performance of the membrane system, while increasing the gas mixture velocity deteriorates the CO2 separation of the system. The impact of hollow fiber geometry on the removal of CO2 is investigated and the results indicate that hollow fibers with smaller inner diameter provides higher effective mass-transfer area and therefore superior CO2 removal performance. Furthermore, the modeling predictions for the CO2 removal are in good agreement with the experimental data under various ratios of gas to liquid velocity. The PTFE hollow fiber membrane contacting system showed a great potential for separation of CO2 from gas mixtures.

A wave optics based fiber scattering model

Existing fiber scattering models in rendering are all based on tracing rays through fiber geometry, but for small fibers diffraction and interference are non-negligible, so relying on ray optics can result in appearance errors. This paper presents the first wave optics based fiber scattering model, introducing an azimuthal scattering function that comes from a full wave simulation. Solving Maxwell's equations for a straight fiber of constant cross section illuminated by a plane wave reduces to solving for a 3D electromagnetic field in a 2D domain, and our fiber scattering simulator solves this 2.5D problem efficiently using the boundary element method (BEM). From the resulting fields we compute extinction, absorption, and far-field scattering distributions, which we use to simulate shadowing and scattering by fibers in a path tracer. We validate our path tracer against the wave simulation and the simulation against a measurement of diffraction from a single textile fiber. Our results show that our approach can reproduce a wide range of fibers with different sizes, cross sections, and material properties, including textile fibers, animal fur, and human hair. The renderings include color effects, softening of sharp features, and strong forward scattering that are not predicted by traditional ray-based models, though the two approaches produce similar appearance for complex fiber assemblies under many conditions.

Chemical and morphological changes in fibre structure due to material heating during ultrasonic-assisted embossing of cardboard

Embossing is a commonly used design element on printed products and packaging. It enhances the product impression with optical and haptic effects. The material deformation during the embossing of cardboard is normally done using high mechanical pressure between two dies. The use of ultrasound in the embossing process leads to a noticeable reduction of the embossing pressure and a greater embossing precision. However, there is a noticeable heating of the cardboard during the ultrasonic-assisted embossing process. This work aimed to characterise the effects of heating and to understand the reasons for the greater precision with decreased force when ultrasound is used. Therefore, the effects of the thermal ultrasonic energy on the chemical composition and the morphological properties of the fibres were investigated. The findings showed that no noticeable changes occurred in the chemical composition or fibre geometry as a result of the embossing process with ultrasound.