Two-dimensional Fiber Research Articles

Investigation of fibre orientation using SEM micrograph and prediction of mechanical properties through micromechanical modelling

The present study concerns the fabrication of short sisal fibre-reinforced polypropylene (PP/SF) composites by melt mixing with different fibre length (3, 6 and 10 mm) comprising of 70% of matrix PP and 30% of SFs followed by injection moulding. The PP/MA-g-PP/SF composites were prepared with the ratio of 65:5:30 with the optimized fibre length of 6 mm at different mould temperatures (25, 45 and 65°C) in a similar fashion. This work also further extended to study the effect of fibre orientation of the composites by numerical calculation of second-order orientation tensor. To evaluate the fibre orientations PP/MA-g-PP/SF composites at different mould temperatures, scanning electron microscope micrographs were used to estimate the accurate principal directions and two-dimensional fibre orientation distributions through centre coordinates of the elliptical fibre images. Finally, a mathematical model of modified rule of mixture was adopted to compare the predicted tensile strength and modulus with the experimental findings.

Design of hybrid photonic crystal fiber with elliptical and circular air holes analyzed for large flattened dispersion and high birefringence

A design of two-dimensional hybrid photonic crystal fiber (PCF) with elliptical and circular air holes and its analyses for large flattened dispersion and high birefringence is presented. The PCF has hexagonal layout with triangular lattice. There are five rings around the solid core. The inner three rings around the core have elliptical air holes while the outer two rings have circular air holes. Three such layouts are designed, analyzed, and compared with the layout having only circular air hole using full-vector finite difference time domain method. The layout with hybrid structure having combined elliptical and circular air hole gives a large flattened dispersion of the order of 4.88 ps/nm/km for the wavelength range of 1.2 to 1.8 μm and magnitude of modal birefringence is 1.238×10−3 at 1.55-μm wavelength.

Flipping and scooping of curved 2D rigid fibers in simple shear: The Jeffery equations

The dynamical system governing the motion of a curved rigid two-dimensional circular-arc fiber in simple shear is derived in analytical form. This is achieved by finding the solution for the associated low-Reynolds-number flow around such a fiber using the methods of complex analysis. Solutions of the dynamical system display the “flipping” and “scooping” recently observed in computational studies of three-dimensional fibers using linked rigid rod and bead-shell models [J. Wang et al., “Flipping, scooping, and spinning: Drift of rigid curved nonchiral fibers in simple shear flows,” Phys. Fluids 24, 123304 (2012)]. To complete the Jeffery-type equations for a curved fiber in a linear flow field we also derive its evolution equations in an extensional flow. It is expected that the equations derived here also govern the motion of slender, curved, three-dimensional rigid fibers when they evolve purely in the plane of shear or strain.

Oxidation behaviors and shear properties of z-pinned joint made of two-dimensional carbon fiber reinforced silicon carbide composite

Chemical vapor infiltration has been introduced for preparing z-pinned joint, which is made of two-dimensional carbon fiber reinforced silicon carbide composite. The effects of oxidation on the shear properties of the joint were investigated. The results showed that the joint strength increases with the increase of oxidation temperature, which is consistent with the oxidation consumption of the carbon phases. An exponential relationship is presented between the weight loss and the joint strength. In contrast, linear relationships are presented between the weight loss and the mechanical properties of the composite. The exponential relationship results from the coupled shear and bending stress states of the pin, according to the failure mechanisms of the joint. It is observed that in-plane and intra-layer cracks are formed under the shear stress. And these cracks are bridged by the fibers under the bending stress. Accordingly, the fiber bridging mechanism contributes to the joint strength before and after oxidation. For the conditions of this study, the joint strength can be roughly estimated as the plus of the in-plane shear strength and the tensile matrix cracking stress.

Effects of porosity on in-plane and interlaminar shear strengths of two-dimensional carbon fiber reinforced silicon carbide composites

Porosity effects on shear properties of 2D C/SiC were investigated based on the corresponding shear damage mechanisms. The results show that as the total porosity increases from 12.2% to 26.1%, the interlaminar shear strength decreases from 44.58MPa to 17.80MPa according to a power law, while the in-plane shear strength decreases linearly from 143.25MPa to 74.38MPa. Under interlaminar shear stress, delamination is resulted from matrix cracking and interface debonding/sliding mechanisms. Effects of porosity on interlaminar shear strength is controlled by the volume fraction of the delaminated matrix. Under in-plane shear stress, echelon matrix shear cracking and large scale fiber bridging mechanisms occur. The decreasing of in-plane shear strength depends on the spacing between the echelon cracks. Since the interface debonding/sliding mechanism occurs under both in-plane and interlaminar shear stresses, a relationship is obtained that the in-plane shear strength equals the sum of the interlaminar shear strength and the fiber bridging term under the minimum total porosity about 30.5%.

Influence of sintering process on microstructure and fracture behavior of CF/Si3N4 laminated ceramic composites

Carbon fibre reinforced Si3N4 (CF/Si3N4) biomimetic laminated ceramic composites were prepared through rolling, alternate stacking of two-dimensional carbon fibre cloth and Si3N4 green layers, burning out of organic components and hot-press sintering. The effects of the sintering process and sintering additives on the microstructure, fracture behavior and toughening mechanism of the composite were analysed. When sintered at 1850°C for 1.5 h with Al2O3, Y2O3 and MgO as sintering additives, a fully densified composite was obtained with homogeneous and moderate bonding interfaces between CF and the Si3N4 matrix, presenting improved flexural strength of 374.93 MPa and fracture toughness of 10.71 MPa m1/2, which were increased by 13.20% and 71.36% respectively, as compared with the monolithic Si3N4 ceramic. The primary toughening mechanism of the composite can be concluded as multiple crack deflection at the carbon fibre layers, fracture and pull-out of CF bundles and single CF within the carbon fibre layers.

On the first stability eigenvalue of CMC surfaces into warped products with two-dimensional fiber

The purpose of this article is the search of estimates for the first eigenvalue of the stability operator for constant mean curvature compact two-sided surfaces immersed into three-dimensional warped product spaces with two-dimensional fiber satisfying a suitable and well studied convergence condition. We also characterize the cases when the upper bound is reached. As an application, we derive some consequences for those surfaces that are stable, obtaining some classification results.

Double fiber probe with a single fiber Bragg grating based on the capillary-driven self-assembly fabrication method for dimensional measurement of micro parts

Focusing on the ultra-precision dimensional measurement of parts with micro-scale dimensions and high aspect ratios, a two-dimensional double fiber probe with a single fiber Bragg grating (DS-FBG probe) is investigated in detail in this paper. The theoretical analysis of the sensing principle is verified by spectrum simulations of the DS-FBG probe with a modified transfer matrix method using the strain distribution within the DS-FBG probe. The fabrication process and physical principle of the capillary-driven self-assembly of double fibers in the UV adhesive with a low viscosity are demonstrated. Experimental results indicate that resolutions of 30 nm in radial direction and 15 nm in axial direction can be achieved, and the short-term displacement drifts within 90 seconds are 28.0 nm in radial direction and 7.9 nm in axial direction, and the long-term displacement drifts within 1 hour are 61.3 nm in radial direction and 17.3 nm in axial direction. The repeatability of the probing system can reach 60 nm and the measurement result of a standard nozzle is 300.49 μm with a standard deviation of 20 nm.

Oxidation effects on in-plane and interlaminar shear strengths of two-dimensional carbon fiber reinforced silicon carbide composites

Effects of oxidation on in-plane shear strength and interlaminar shear strength of two-dimensional carbon fiber reinforced silicon carbide composites (2D C/SiC) were studied based on the corresponding shear damage mechanisms. The results showed that oxidation had resulted in severe degradations of the two strengths, however, it had little influence on the shear failure mechanisms. Under in-plane shear loading, large-scale fiber bridging mechanism controlled the shear behaviors. A modified rigid body sliding model was proposed to characterize the in-plane shear strength. In Comparison, interface sliding mechanism controlled the interlaminar shear strength. Based on above failure mechanisms, the two shear strengths were quantitatively characterized by the constituent properties, such as diameter of carbon fibers, interface sliding stress, matrix fracture energy and matrix cracking spacing. Therefore, oxidation effects on them were attributed to the decreased constituent properties which mainly results from oxidation consumption of the carbon phases. Finally, for the conditions of this study, a relationship was proposed that the interlaminar shear strength equals the in-plane shear strength minus the fiber bridging stress.

Nonlinear finite element analysis of ultra-high-performance fiber-reinforced concrete beams

A nonlinear finite element analysis was performed to simulate the flexural behaviors of ultra-high-performance fiber-reinforced concrete beams. For this, two different tension-softening curves obtained from micromechanics-based analysis and inverse analysis were incorporated. For micromechanics-based analysis, two-dimensional and three-dimensional random fiber orientations were assumed to obtain the fiber-bridging curve, and a softening curve of matrix in ultra-high-performance fiber-reinforced concrete was used. The use of tension-softening curves obtained from inverse analysis and micromechanics-based analysis using two-dimensional random fiber orientation exhibited fairly good agreement with the experimental results, whereas the use of tension-softening curve from micromechanics-based analysis using three-dimensional random fiber orientation underestimated the experimental results.

Detective technology with temporal resolution for the spatial distribution of near backscatter energy

The laser inertial confinement fusion experiment can provide very important data for the research of laser-plasma interaction to detect the spatial and temporal property of the backscatter light. The backscatter diagnostic system we already have dont have temporal resolution for the spatial distribution of backscatter energy. Therefore, based on the near backscatter diagnostic system on SG-Ⅲ prototype laser facility, we proposed and designed a kind of recording method which could detect the temporal process for the spatial distribution of backscatter energy. We verified the feasibility of this method through static experiment, whose result demonstrated that it was possible to record the messages transmitted by one-dimensional to two-dimensional imaging fiber bundles and retrieve these messages to two-dimensional image by data processing.

Mesophase pitch-based graphite fiber-reinforced acrylonitrile butadiene styrene resin composites with high thermal conductivity

One-dimensional (1-D) and two-dimensional (2-D) mesophase pitch-based graphite fiber (MPGF)/acrylonitrile butadiene styrene (ABS) resin composites were prepared from unidirectionally arranged MPGF/ABS resin laminae by a hot-press method. The morphologies, optical texture and crystal structure of the MPGFs and their ABS resin composites were investigated. The influence of the volume fraction, diameter and graphitization temperature of the MPGFs and the composite architecture on the thermal properties of the composites was discussed. The thermal diffusivity and thermal conductivity of the resultant composites parallel to the longitudinal fiber direction increase markedly with the volume fraction, diameter and graphitization temperature of the fibers. The 1-D composite with a fiber volume fraction of 62% possesses a bulk density of 1.64 g/cm3 and shows a high thermal diffusivity of 372 mm2/s and a high thermal conductivity of 518 W/m K parallel to the longitudinal fiber direction at room temperature. The corresponding axial thermal conductivity of the fibers, graphitized at 2900 °C with a diameter of 50–55 μm, is estimated to be 825 W/m K. The 2-D composite filled with a high (54%) volume fraction of MPGFs also exhibits a high thermal conductivity in two directions (parallel to the longitudinal directions of the incorporated fibers).

Method to Improve Seismic Performance of RC Moment-Resisting Frames Using Geometric Optimization

AbstractThis article presents an optimization method to determine the column dimensions that maximize the fundamental frequency of a building, which translates into a highly efficient computational algorithm for approximately solving this optimization problem. A thoroughly detailed example is provided for a 10-story building whose elastic behavior is analyzed using a three-dimensional model, employing a two-dimensional fiber model to assess its inelastic performance. The results show that, compared with the classical design, which has columns of uniform depth, the maximum elastic drift is reduced by 10% and that the drift demand decreases on the lower stories of the building. In addition, the overstrength of the structure and its ductility are increased by between 10 and 30%. Similar improvements are also observed in a second example for a five-story building, showing that the method is useful at least for midrise buildings.

Pasted type distributed two-dimensional fiber Bragg grating vibration sensor.

A pasted type distributed two-dimensional fiber Bragg grating (FBG) vibration sensor has been proposed and studied in this paper. The optical fiber is directly considered as an elastomer. The two-dimensional vibration can be separated by subtraction/addition of two FBGs' center wavelength shift. The principle of the sensor as well as numerical simulation and experimental analyses are presented. Experimental results show that the resonant frequencies of the sensor x/y main vibration direction are separately 1300/20.51 Hz, which are consistent with the numerical simulation analysis result. The flat frequency range resides in 10-750 Hz and 3-12 Hz, respectively; dynamic range is 28.63 dB; in the x main vibration direction, the sensor's sensitivity is 32.84 pm/g, with linearity 3.91% in the range of 10-60 m/s(2), while in the y main vibration direction, the sensor's sensitivity is 451.3 pm/g, with linearity 1.92% in the range of 1.5-8 m/s(2). The cross sensitivity is 3.91%. Benefitting from the two dimensional sensing properties, it can be used in distributed two-dimensional vibration measurement.

Optimization of Tow-Steered Composite Wing Laminates for Aeroelastic Tailoring

Tow-steered composites are optimized for use in tailoring the aeroelastic behavior of a simple two-dimensional composite wing, with particular emphasis on improving both flutter/divergence airspeeds and gust loads. Symmetric layups are considered where the fibers vary in orientation along the wingspan and chord. Tow-steered laminates were found to increase the instability airspeed by up to 7% compared with optimized straight-fiber laminates and by 13% compared with optimized laminates with standard () plies. Tow-steered laminates were also found to reduce the peak wing root gust loads (up to 52%) and the correlated gust loads (up to 24%). The lowest gust loads were reached with higher order nonlinear fiber angle variations when either all plies were optimized or when two-dimensional fiber angle variations were used. Optimization strategies that allowed the fiber angles to vary freely in each ply generally performed better than optimizations based on the rotation of ()-ply stacks along the span of the wing.

A Practical Deconvolution Computation Algorithm to Extract 1D Spectra from 2D Images of Optical Fiber Spectroscopy

Bolton & Schlegel presented a promising deconvolution method to extract one-dimensional (1D) spectra from a two-dimensional (2D) optical fiber spectral CCD (charge-coupled device) image. The method could eliminate the PSF (point-spread function) difference between fibers, extract spectra to the photo noise level, as well as improve the resolution. But the method is limited by its huge computation requirement and thus can not be implemented in actual data reduction. In this article, we develop a practical computation method to solve the computation problem. The new computation method can deconvolve a 2D fiber spectral image of any size with actual PSFs, which may vary with positions. Our method does not require large amounts of memory and can extract a 4 k × 4 k noise-free CCD image with 250 fibers in 2 hr. To make our method more practical, we further consider the influence of noise, which is thought to be an intrinsic ill-posed problem in deconvolution algorithms. We modify our method with a Tikhonov regularization item to depress the method induced noise. We do a series of simulations to test how our method performs under more real situations with Poisson noise and extreme cross talk. Compared with the results of traditional extraction methods, i.e., the Aperture Extraction Method and the Profile Fitting Method, our method has the least residual and influence by cross talk. For the noise-added image, the computation speed does not depend very much on fiber distance, the signal-to-noise ratio converges in 2–4 iterations, and the computation times are about 3.5 hr for the extreme fiber distance and about 2 hr for nonextreme cases. A better balance between the computation time and result precision could be achieved by setting the precision threshold similar to the noise level. Finally, we apply our method to real LAMOST (Large sky Area Multi-Object fiber Spectroscopic Telescope; a.k.a. Guo Shou Jing Telescope) data. We find that the 1D spectrum extracted by our method has both higher signal-to-noise ratio and resolution than the traditional methods, but there are still some suspicious weak features, possibly caused by the method around the strong emission lines. As we have demonstrated, our deconvolution method has solved the computation problem and progressed in dealing with the noise influence. Multifiber spectra extracted by our method will have higher resolution and signal-to-noise ratio, and thus will provide more accurate information (such as higher radial velocity and metallicity measurement accuracy in stellar physics) to astronomers than traditional methods.

Two-dimensional long-flexible fiber simulation in simple shear flow

Long-flexible fiber orientation under the influence of a flow field is an important engineering problem. One can encounter this problem in many fields. For example in fiber reinforced thermoplastics produced in both injection and compression molding, fiber orientation affect final part properties. Fiber orientation models are constructed for short fibers in a simple shear flow case and though this case is important it is not the general case. In this work we extract rotational friction coefficients from Jeffery's model, create a general case long-flexible fiber orientation model, and apply it in a simple shear flow. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Spatiotemporal optical bullets in two-dimensional fiber arrays and their stability

Long-lived light bullets fully localized in both space and time can be generated in novel photonic media such as multicore optical fiber or waveguide arrays. In this paper we present detailed theoretical analysis on the existence and stability of the discrete-continuous light bullets using a very generic model that occurs in a number of applications.

Manufacture of a 2D optical fiber array coupler with micrometer precision for laser radar applications

This article presents the manufacture of a 2D-fiber array coupler using UV-LIGA technology for the precise positioning of a two-dimensional (2D) optical fiber array. The precision of the alignment of the eight-by-eight fiber array was demonstrated to be less than 2 μm. The average concentricity error of the fibers to the positioning holes of the array coupler had a minimum and maximum error of 1.7 µm and 6.5 μm, respectively. The 2D fiber array coupler can fulfill the coupling and transmission requirements of 2D light spots for laser radar applications. The method developed here can easily be extended to the manufacture of larger arrays.

Multi-channel laser Doppler velocimetry using a two-dimensional optical fiber array for obtaining instantaneous velocity distribution characteristics

A laser Doppler velocimeter (LDV) has been developed that is capable of performing two-dimensional (2D) cross-sectional measurements. It employs two horizontal laser light sheets that intersect at an angle of 13.3°. Since the intersection region is thin, it can be used to approximately determine the 2D flow field. An 8 × 8 array of optical fibers is used to simultaneously measure Doppler frequencies at 64 points. Experiments were conducted to assess the performance of the LDV, and it was found to be capable of obtaining spatial and temporal velocity information at multiple points in a flow field. The technique is fast, noninvasive, and accurate over long sampling periods. Furthermore, its applicability to an actual flow field was confirmed by measuring the temporal velocity distribution of a pulsatile flow in a rectangular flow channel with an obstruction. The proposed device is thus a useful, compact optical instrument for conducting simultaneous 2D cross-sectional multipoint measurements.