Fiber Rotation Research Articles

Off-axis mechanical behavior and dynamic characteristics of UHMWPE composite laminates

An understanding of the off-axis mechanical behavior and failure mechanisms of ultra-high molecular weight polyethylene (UHMWPE) cross-ply laminates subjected to quasi-static and dynamic loadings is developed, with focus on the influence of off-axis angle and strain rate. For off-axis tension, UHMWPE laminates exhibit polymer shear response characteristics. An orientation-hardening phenomenon is captured, as fiber rotation leads to local increment of load capacity along the loading orientation. The failure strength presents an evidentially descending trend with off-axis angle from 0° to 45°. A non-monotonic variation of strength with strain rate is further observed: increasing with strain rate up to 500 s−1 but decreasing above, which is attributed to failure mode switching from plastic failure to brittle failure. The Tsai-Wu failure criterion, on homogenized cross-ply laminae, is experimentally modified with rate dependence. Further investigation on detailed information of the unidirectional properties should be conducted with the backing-out scheme to establish unidirectional failure criterion.

Flexible ZIF-67@PVDF tree-like nanofiber membrane with high piezoelectric output for energy harvesting

Modern demands for efficient, environmentally friendly, and self-powered devices have led to growing interest in piezoelectric polymers in the scientific community. In this paper, a ZIF-67 functionalized polyvinylidene fluoride/ tetrabutylammonium hexafluorophosphate tree-like nanofiber membrane (ZIF-67@PVDF/TBAHP-TLNMs) was developed as piezoelectric nanogenerator for energy harvesting. The ZIF-67@PVDF/TBAHP-TLNMs was prepared by in-situ growth of ZIF-67 on the surface of PVDF TLNMs, which demonstrated remarkable energy harvesting capabilities. The results indicated that the β-phase content of the in-situ growth of ZIF-67 reached 86.94 %, augmented the fiber's rotation radius, and elevated the electromechanical conversion efficiency. Notably, the short circuit current reached 3.87 μA and the output voltage exceeded 9.78 V, which was 10.7 times and 5.9 times higher than the electrical signal output of pure PVDF nanofiber membrane, respectively. Furthermore, the ZIF-67@PVDF/TBAHP-TLNMs exhibited exceptional mechanical properties, with an elastic modulus as high as 1.13 GPa, outperforming other nanofiber membranes and catering to the diverse requirements of wearable devices. During a 500 s test cycle, its layered structure remained intact, without any discernible damage or interlayer separation of the nanofibers. At the same time, the device exhibited high electromechanical conversion efficiency and a sensitive sensing function, which made it have broad application prospects in human motion monitoring and intelligent wearable devices.

Rare-earth dopant distribution measurement of optical fibers based on filtered back projection

We present a nondestructive measurement based on filtered back projection (FBP) for the distribution of rare-earth dopant in optical fibers. Based on the approach, a measurement system is established, where the single-mode pumped laser illuminates the fiber under test from the side, generating multi-wavelength fluorescence through photoluminescence (PL). The distribution of rare-earth doped particles is proportional to the distribution of fluorescence intensity. The projection images are collected by the CCD camera at 90° relative to the excitation arm. According to the computed tomography (CT), the rotation of the optical fiber enables the experimental measurements of intensity information extracted from multi-angle projections. The rare-earth dopant distribution of the fiber is reconstructed by the improved filtered back projection algorithm, which improves the quality of the reconstructed result by incorporating total variation (TV) algorithm. To evaluate the proposed approach, rare-earth dopant distribution is compared with results measured by EPMA, exhibiting a correlation coefficient above 0.99, and the relationship between the dopant distribution and the refractive index is analyzed. Measurements on doped particle distributions at various wavelengths are conducted, and the fluorescence spectrum are constructed to further analyze the fluorescence characteristics of rare earth doped fiber. Measurement of RE dopant distribution will be useful for quality evaluation and optimization of partial active optical fibers.

Mechanical properties and microstructure evolution of T2 copper in multimodal ultrasonic vibration assisted micro-compression

Multimodal ultrasonic vibration (UV) assisted micro-forming has been widely investigated for its advantages of further reducing forming loads and improving forming quality. However, the influence mechanism of different UV modes on microstructure evolution and mechanical properties was still unclear. Multimodal UV assisted micro-compression tests on T2 copper with different grains and sample sizes were conducted in this study. The microstructure evolution for different UV modes was observed by EBSD. The results showed that the true stress reduction caused by UV was increased sequentially with tool ultrasonic vibration (TV), mold ultrasonic vibration (MV) and compound ultrasonic vibration (CV). The region of grain deformation was shifted along the direction of UV, and the MV promoted the uniform distribution of deformation stress. The grain refinement, fiber streamline density, grain deformation and rotation degree were further enhanced under CV, due to the synergistic effect of TV and MV. Additionally, a coupled theoretical model considering both acoustic softening effect and size effect was proposed for describing the mechanical properties. And a physical model of dislocation motion in different UV modes was developed for describing the microstructure evolution. The maximum error between the theoretical and experimental results was only 2.39 %. This study provides a theoretical basis for the optimization of UV assisted micro-forming process.

Investigation of Fiber Orientation of Fused Filament Fabricated CFRP Composites via an External Magnetic Field

Abstract For carbon fiber-reinforced plastic (CFRP) composites, controlling the interior fiber distribution and orientation during the manufacturing process is a common approach to optize the structural performance of fabricated parts. However, few studies have been conducted to investigate fiber alignment during the additive manufacturing of CFRP composites. This study proposes a magnetic field controlled (MFC) method to control the fiber orientation during the fused filament fabrication (FFF) of nickel-coated carbon fiber (NCF) reinforced polymer composites. Firstly, a theoretical analysis model is established to explore the suitable magnetic field intensity for fiber rotation. Secondly, a customized FFF system with MFC components is implemented, and a polylactic acid matrix composite containing 10 wt% NCF is printed to validate the feasibility of the proposed approach. The microstructure of the printed samples is examined to assess the effectiveness of the method. Finally, uniaxial tensile tests are performed to investigate the impact of fiber orientation adjustment on mechanical properties. The experimental results reveal that the MFC method can effectively align the interior fiber orientation of CFRP composites, leading to a significant increase in the tensile strength (approximately 8.8%) and Young's modulus (around 10.5%) of the printed samples.

Fiber reorientation due to obstacles in open channel flow

A model along with experimental validation is presented for fiber re-orientation within the flow of a thin fluid layer down an inclined plane. Unlike the usual approach (Jeffery), the model accommodates the fast-changing velocity gradient defying linearization and the flow constraints due to the thin thickness of the fluid film. Model equations are formulated, and the algorithm for the fiber rotation is developed. The velocity field within the channel is obtained, using COMSOLTM multiphase simulation. The formulated model equations are used to track the orientation of a single fiber. The spatial fiber orientation state is described in terms of the second order tensor by tracking multiple individual fibers with different initial orientations. To validate the model's predictions, an experimental setup was fabricated to record individual fiber kinematics during the flow and to describe the orientation of fibers in the open channel. A novel benchmark for assessing fiber re-orientation models is presented, wherein the dynamics of fiber orientation is observed in response to a semicircular obstacle within the fluid flow. The experimental results are compared to model predictions and are in reasonable agreement. Despite the simplified approach, both the dynamic of single fiber and the development of fiber orientation distribution due to the obstacle can be reasonably predicted.

The Nanoscale Ordering of Cellulose in a Hierarchically Structured Hybrid Material Revealed Using Scanning Electron Diffraction.

Cellulose, being a renewable and abundant biopolymer, has garnered significant attention for its unique properties and potential applications in hybrid materials. Understanding the hierarchical arrangement of cellulose nanofibers is crucial for developing cellulose-based materials with enhanced mechanical properties. In this study, the use of Scanning Electron Diffraction (SED) is presented to map the nanoscale orientation of cellulose fibers in a bio-composite material with a preserved wood cell structure. The SED data provides detailed insights into the ordering of cellulose with an extraordinary resolution of ≈15nm. It enables a quantitative analysis of the fiber orientation over regions as large as entire cells. A highly organized arrangement of cellulose fibers within the secondary cell wall is observed, with a gradient of orientations toward the outer part of the wall. The in-plane fiber rotation is quantified, revealing a uniform orientation close to the middle lamella. Transversely sectioned material exhibits similar trends, suggesting a layered cell wall structure. Based on the SED data, a 3D model depicting the complex helical alignment of fibers throughout the cell wall is constructed. This study demonstrates the unique opportunities SED provides for characterizing the nanoscale hierarchical arrangement of cellulose nanofibers, empowering further research on a range of hybrid materials.

Effect of rotation on wave propagation in fibre-reinforced viscothermoelastic media of higher order

The purpose of the current study is to establish a novel mathematical model in the wave propagation in fibre-reinforced viscothermoelastic media of higher order. The governing equations of a fibre-reinforced viscothermoelastic media of higher order are solved analytically to determine mechanical displacement and stresses. Dispersion relation for Rayleigh-type, Love-type, and Stoneley-type wave has been derived using suitable boundary conditions, which is found to be complex in nature. The analysis included Rayleigh-type, Love-type, and Stoneley-type waves while the findings revealed a broader scope compared to previous research, which is encompassed by our results as special cases. Findings are compared with and without rotational effect, along with assessing the parameters for fiber-reinforced materials in the medium, it was observed that surface waves could not propagate in a fast rotating medium. These results are computed numerically and depicted graphically to highlight the effects of fiber reinforcement and rotation parameter on the surface wave speed. Certain particular cases of interest have been deduced from the current investigation. Numerical results and graphical analyses of surface waves were performed using MATLAB software.

The Truth of the Experiments of Invariable Speed of Light in Special Relativity

It is pointed out that the most experiments on the invariant speed of light in special relativity proves the round-trip invariant speed of light, not one-way invariant. This paper makes a distinction between them. The Michelson-Morley experiment and the experiment of high-energy particles emitting photons and so on are the round-trip experiment of light’s speed, showing that the average speed of light is a constant. But the Sagnac effect experiment, the Michelson-Gale's experiment that the earth's rotation effects the speed of light, and the satellite signal propagation between China and Japan are the one-way experiments of light’s speed, showing that the speed of light is variable, satisfying the Galilean velocity addition rule. The orbit shape changes of binary stars and the phenomenon of charm stars cannot be observed due to that the calculated observing directions are different from the practical observing direction for the observers on the Earth. The Fizeau water flow experiment and the Sagnac experiment are combined to prove that the rotation of optical fiber would affects the speed of light. The problem that the Sagnac effect is independent of the refractive index of optical fiber is explained well. It is proved that the Sagnac effect formula derived from special relativity is consistent with that derived from classical mechanics when the optical fiber’s refractive index . When , there is no the Sagnac effect according to special relativity. While according to classical mechanics, there is the Sagnac effect. The original experiment of Sagnac effect in 1913 was carried out in atmosphere with . Therefore, the original Sagnac experiment became a judgment experiment. It certainly jugated that the velocity of light satisfied the Galilean addition rule rather than the Lorentz transformation formula.

Mechanical Characterization of Collagen Hydrogels by Quasistatic Uniaxial Tensile Experiments

Collagen serves as an essential structural material in the human body. Despite the complex mechanical conditions surrounding the collagen hydrogels, previous studies mostly focus on analyzing the mechanical behavior under dynamically varying compressive or shear loads, but the tensile properties at the quasistatic time scale are relatively less studied. This work aims to investigate the quasistatic tensile behavior of reconstituted collagen hydrogels under uniaxial tensile stresses. The evolution of the collagen fiber network structures with straining is visually observed using the confocal microscope equipped with the tensile strain actuator. While the unfolding of the initially undulated fibers accommodates the early‐stage strains, the deformation mechanism continuously changes to the stretching of fibers through the network alignment to the tensile direction. This transition commences with the buckling of a fiber lying transverse to the loading direction, which otherwise locks the rotation of adjacent fibers.

Decomposition of plate displacements via Kirchhoff–Love displacements

In this paper, we show that any displacement of a plate is the sum of a Kirchhoff–Love displacement and two terms, one for shear and one for warping. The plate is then loaded so that bending and shear contribute the same order of magnitude to fiber rotation.

Temperature dependence of optical fiber current sensor with external conversion

The paper presents the research of a optical fiber current sensor with external conversion (OFCS-EC) as a function of temperature. The sensor was developed in the Department of Optoelectronics. The sensor was tested in the temperature range from 23 °C – 80 °C. For each of the temperatures, the sensitivity was determined on the basis of a sinusoidal waveform. Thus, the linearity of the transfer characteristics was checked. The main purpose of the experiment was to check the limits of sensitivity changes in changing thermal conditions and whether the sensor meets the standards used in the power industry. Full Text: PDF References M.J. Weber, "CRC Handbook of Laser Science and Technology. Supplement 2: Optical Materials", CRC Press, Boca Raton, FL, USA (1995). CrossRef S. Ju, Y. Lee, Y.T. Ryu, S.G. Kang, J. Kim, P.R. Watekar, B.H. Kim, Y. Lee, Y.H. An, C.J. Kim, W.T. Han, "Temperature Dependence of Faraday Rotation of Glass Optical Fibers Doped with Quantum Dots of CdSe and CdMnTe", Phys. Status Solidi A, 216: 1800549 (2019). CrossRef E. Lage, L. Beran, A.U. Quindeau, L. Ohnoutek, M. Kucera, R. Antos, S. R. Sani, G.F. Dionne, M. Veis, C.A. Ross; Temperature-dependent Faraday rotation and magnetization reorientation in cerium-substituted yttrium iron garnet thin films. APL Mater. 5, 036104 (2017). CrossRef S. Ju, J. Kim, K. Linganna, P.R. Watekar, S.G. Kang, B.H. Kim, S. Boo, Y. Lee, Y.H. An, C.J. Kim, et al. "Temperature and Vibration Dependence of the Faraday Effect of Gd2O3 NPs-Doped Alumino-Silicate Glass Optical Fiber". Sensors, 18, 988 (2018). CrossRef A. Jeffrey, D. and R.M. Bunch, "Temperature dependence of the Faraday rotation of Hoya FR-5 glass," Appl. Opt. 23, 633 (1984). CrossRef K. Barczak, J. Juraszek, "Optoelectronic system for detecting short-circuits in low voltage networks", Photon. Lett. Pol, 14, 37 (2022). CrossRef K. Barczak, K. Mazniewski, "Optical fiber current sensor with external conversion for measurements of low AC electric currents", Proc. SPIE, 10455 (2017). CrossRef

Effect of flax fiber orientation in carbon-flax fiber composite on tensile and visco elastic behavior

This paper deals with the effect of Flax fiber orientations on the tensile and viscoelastic response of Carbon/Flax hybrid composite. The composite laminates were prepared by varying flax fiber orientations of [0°4F/0°1C]1, [+30°2F/0°1C/−30°2F]1, [+45°2F/0°1C/−45°2F]1, [+60°2F/0°1C/−60°2F]1, and [+75°2F/0°1C/−75°2F]1 using the Hot press compression molding technique. The tensile and DMA (Dynamic Mechanical Analyzer) tests have been done for evaluating strength, strain to failure, toughness and storage and loss modulus, and also the damping factor of the laminates. The maximum tensile strength of 262 MPa was observed for 0-Degree oriented Flax fiber Carbon epoxy laminates. However, a decrease in tensile strength was noticed as the Flax fiber orientation increased from 0-Degree to 75-Degree. The maximum strain of 7.5% was induced in the 30-Degree Flax fiber carbon composite. Additionally, it was noticed that the rotation of fibers during load applied is the main cause for inducing additional strain to failure of Flax fibers. Changes in the storage modulus, loss modulus, and, damping factor were also observed for different flax fiber orientations.

Influence of internal muscle properties on muscle shape change and gearing in the human gastrocnemii.

Skeletal muscles bulge when they contract. These three-dimensional shape changes, coupled with fiber rotation, influence a muscle's mechanical performance by uncoupling fiber velocity from muscle belly velocity (i.e., gearing). Muscle shape change and gearing are likely mediated by the interaction between internal muscle properties and contractile forces. Muscles with greater stiffness and intermuscular fat, due to aging or disuse, may limit a muscle's ability to bulge in width, subsequently causing higher gearing. The aim of this study was to determine the influence of internal muscle properties on shape change, fiber rotation, and gearing in the medial (MG) and lateral gastrocnemii (LG) during isometric plantar flexion contractions. Multimodal imaging techniques were used to measure muscle shear modulus, intramuscular fat, and fat-corrected physiological cross-sectional area (PCSA) at rest, as well as synchronous muscle architecture changes during submaximal and maximal contractions in the MG and LG of 20 young (24 ± 3 yr) and 13 older (70 ± 4 yr) participants. Fat-corrected PCSA was positively associated with fiber rotation, gearing, and changes in thickness during submaximal contractions, but it was negatively associated with changes in thickness at maximal contractions. Muscle stiffness and intramuscular fat were related to muscle bulging and reduced fiber rotation, respectively, but only at high forces. Furthermore, the MG and LG had varied internal muscle properties, which may relate to the differing shape changes, fiber rotations, and gearing behaviors observed at each contraction level. These results indicate that internal muscle properties may play an important role in mediating in vivo muscle shape change and gearing, especially during high-force contractions.NEW & NOTEWORTHY Here, we measured internal muscle properties in vivo to determine their influence on the varying shape change and gearing behaviors in the synergistic gastrocnemii muscles. These relationships have previously only been hypothesized or examined within isolated muscles during supramaximal contractions. Our results contribute to a more comprehensive understanding of the factors that influence a muscle's mechanical response to force with implications for preventing or treating muscle deficits associated with aging, disease, and disuse.

Alignment of carbon fiber and PDMS mixture flowing in 90° elbow channel

In this study, flow visualization experiments and computational fluid dynamics simulations are conducted to analyze the rotation of carbon fibers flowing in a 90° elbow channel. In the corner of the 90° elbow channel, a directional change in velocities and velocity gradients results in the rotation of the fibers from a horizontal to vertical alignment. To analyze the fiber rotation, a mixture comprising uncured polydimethylsiloxane and ball-milled carbon fibers is utilized as the working fluid in a flow visualization experiment. The velocity and velocity gradients inside the channel are calculated via computational fluid dynamics simulation and then compared with the angular changes in the fiber rotation along different trajectories inside the elbow corner. A Lagrangian approach using a local coordinate system to trail each fiber along the trajectory is utilized to compare the effects of shear rate on fiber rotation. It is discovered that the fibers are affected by a relatively high local shear rate, and that they propagate with the flow, indicating a parallel alignment in the flow direction while exhibiting a 90° turn at the elbow corner.

Utilising Surrogate Models to Approximate Cardiac Potentials when Solving Inverse Problems via Bayesian Techniques.

Solving inverse problems is computationally expensive, if not infeasible, under specific scenarios. For example, many forward solutions are required when solving inverse problems using Bayesian techniques. In this work, a novel inference protocol is established, that can be used to infer the cardiac bidomain conductivities and the cardiac fibre rotation angle (bidomain parameters). This protocol uses a surrogate model, developed using generalised polynomial chaos techniques, to approximate cardiac potentials on a multi-electrode array. The resulting surrogate model is used in conjunction with Bayesian inference techniques to infer the bidomain parameters. A lower-order surrogate model (order three) can effectively characterise the influence of the extracellular conductivities and fibre rotation on the cardiac potentials; however, it is recommended that a higher-order surrogate model expansion of order seven be used to adequately characterise the influence of the intracellular conductivities as well. This seventh order surrogate model was successfully used to infer the extracellular conductivities and fibre rotation angle from a single set of synthetically generated noisy experimental potentials, while the intracellular conductivities were unable to be retrieved accurately under this scenario.

All-Fiber Waveplate Made of Helically Wound Spun Highly Birefringent Optical Fiber

Waveplates are elements that are widely used in the optical system for polarization transformation. In the fiber optical system, it is highly desired to utilize waveplates in the all-fiber form with minimum insertion loss and stable performance. In this paper, we propose an all-fiber waveplate that is made of the helically wound spun highly birefringent (SHB) optical fiber. To function as waveplates, the torsion of the helix should be equal to the inherent polarization rotation of the SHB fiber so that the geometric rotation can match the inherent polarization rotation. Therefore, the phase difference between two orthogonal components of the incident polarized light can increase almost linearly with the fiber length. Because the SHB fiber is insensitive to external perturbations, the proposed waveplate can provide a definite and stable polarization transformation. We develop a model based on the perturbation theory to characterize the polarization evolution of the helically wound SHB fiber. Simulations and experiments have demonstrated the excellent performance of our all-fiber waveplates.

Splitting failure of a composite under longitudinal tension

AbstractSignificant variation can be found in measurements for the longitudinal tensile strength of the same unidirectional (UD) composite. A splitting failure is one of the main reasons. It is shown in this paper that the shear stress component resulted from a longitudinal tension and a fiber misalignment can cause the matrix to fail before fiber break. The misalignment angle consists of an initial off‐axial angle and a further fiber rotation during the loading. Based on the micromechanics Bridging Model and the matrix true stress theory established by the author, splitting failure has been analyzed and predicted rigorously in this paper, only using the fiber and matrix properties together with the fiber misalignment angle. The fiber initial misalignment angle of a unidirectional plate can be obtained from testing statistics, or deducing from measured longitudinal compression strength. Our research indicates that the longitudinal tensile strength and the relevant failure mode can be significantly affected by the fiber initial misalignment.

Two-dimensional deformations in a rotating functionally graded fiber-reinforced thermoelastic half-space with magnetic field

The present study is concerned with the two-dimensional deformations in a rotating functionally graded (non-homogeneous), fiber-reinforced, transversely isotropic thermoelastic half-space under the effect of magnetic field in the context of Lord-Shulman theory. Material properties are supposed to be graded in -direction and normal mode technique is adopted to obtain the exact expressions for the temperature field, displacement and stress components. These results are computed numerically and depicted graphically to highlight the effects of fiber reinforcement, non-homogeneity parameter, magnetic field, rotation parameter and time on the variations of different physical fields. Certain particular cases of interest have been deduced from the current investigation.

A micromechanics based model for rate dependent compression loaded unidirectional composites

Strain-rate effects in a unidirectional non-crimp fabric carbon/epoxy composite are addressed. To allow for kink-band formation including strain-rate effects and damage in such composites, the paper advances a recent model focused on compression loading at small off-axis angles. The model is based on computational homogenization with a subscale represented by matrix and fibre constituents at finite deformation. The fibre constituent is assumed to be elastic transversely isotropic and the matrix is viscoelastic–viscoplastic with damage degradation. Novel model improvements of special importance to small off-axis loading relate to the isostress formulation of the homogenized response in transverse shear. In this context, an enhanced homogenized elastic response is proposed based on Halpin–Tsai corrections to account for the nonuniform stress distribution on the microscale. The model captures the strongly rate sensitive kink-band formation due to localized matrix shearing and fibre rotation, confirming the experimentally observed increase in compressive strength for high strain rates.