Fiber Rotation Research Articles

A hybrid method of phase shifting interferometry and optical tomographic techniques for determining the optical anisotropy of grafted nylon-6 fibres with PMMA polymer

A method combining the phase shifting interferometry PSI and optical tomographic techniques for detecting the optical properties of grafted nylon-6 fibres is introduced. The method is capable of detecting the optical anisotropy and morphological properties of the sample at same time for the same region of the tested sample. The effect of grafting of nylon-6 with poly(methyl methacrylate), PMMA, polymer on their optical and morphological properties was investigated. The two-beam Pluta polarising interference microscope attached to a fibre rotation device with the suggested method were used to produce both computed tomographic data for morphological characterisation of the grafted fibre and interferometric measurements of birefringence values along the fibre axis. A blank sample of nylon-6 fibre was used to confirm the impact of grafting process with the PMMA polymer on the optical and structural properties of the nylon-6 fibres. Two -beam interference patterns are included for illustration.

A micromechanically based model for dynamic damage evolution in unidirectional composites

This article addresses the micromechanically motivated, quasistatic to dynamic, failure response of fibre reinforced unidirectional composites at finite deformation. The model draws from computational homogenization, with a subscale represented by matrix and fibre constituents. Undamaged matrix response assumes isotropic viscoelasticity–viscoplasticity, whereas the fibre is transversely isotropic hyperelastic. Major novelties involve damage degradation of the matrix response, due to shear in compression based on a rate dependent damage evolution model, and the large deformation homogenization approach. The homogenized quasi-brittle damage induced failure is described by elastically stored isochoric energy and plastic work of the undamaged polymer, driving the evolution of damage. The developed model is implemented in ABAQUS/Explicit. Finite element validation is carried out for a set of off-axis experimental compression tests in the literature. Considering the unidirectional carbon–epoxy (IM7/8552) composite at different strain rates, it appears that the homogenized damage degraded response can represent the expected ductile failure of the composite at compressive loading with different off-axes. Favourable comparisons are made for the strain and fibre rotation distribution involving localized shear and fibre kinking.

Microfiber transport characterization in human nasal cavity – Effect of fiber length

Understanding the transport and deposition of fibers in the respiratory airway is of great significance for the exposure assessment to non-spherical contaminants. Due to its complexity, few computational studies physically resolved the fibers' coupled translational and rotational motion in investigating fiber transport behaviors in the 3D human nasal airways. Additional studies are needed to fully understand the role of the fiber lengths in nasal deposition and the practical benchmarking of fiber characterization to its spherical equivalency. This study investigated the transport and deposition of fibrous particles in the human nasal cavity, resolving the coupled translational and rotational motion to fill the gap. For the first time, a detailed single fiber trajectory in the 3D nasal chamber, accounting for the coupled translational and rotational movement, was visually presented. The subtle effects of fiber deposition due to fiber lengths, rotation, and interaction with the local flow stream, were revealed and analyzed. Furthermore, the study identified the relationship between microfiber deposition and fiber lengths in the human nasal cavity. In particular, nasal deposition of the fibrous and spherical particles with the same impaction parameter or aerodynamic diameter was compared and discussed. The study led to the findings that fiber lengths play different roles in affecting the transport and deposition of microfibers in the human nasal cavity. The relative deposition level between elongated fibers and the spherical particles varies depending on the impaction parameter or the aerodynamic diameter. Current findings are well supported by the literature data.

Prediction of fiber rotation in an orifice channel during injection molding process

Additive alignment in polymer composites can enhance the physical properties of the constitutive material. Researchers have attempted to understand and predict the additive orientation during the fabrication process, such as injection molding. In this study, the rotation of carbon fibers embedded in uncured polydimethylsiloxane flowing in an orifice channel is analyzed via a flow visualization experiment and image processing of obtained images. The angular velocity of additives is correlated with the shear rates in the flow field calculated from the computational fluid dynamics simulation with the assumption of a single-phase and a non-Newtonian flow. The effective shear rate is found to have a larger effect on the rotation of fiber compared with the aspect ratio of the fiber and the initial alignment angle to the flow direction. A correlation between the effective shear rate and angular velocity of the fibers is developed and verified experimentally. This correlation can be used to predict the fiber rotation during polymer composite fabrication within an orifice channel and hence provide useful information regarding the anisotropic physical properties of the final product.

Cosserat Elasticity of Lattice Solids

We discuss a model of fibrous solids composed of three families of continuously distributed Kirchhoff rods embedded in a matrix material. This is a special case of Cosserat elasticity in which the basic kinematic descriptors are a single deformation field and three rotation fields, one for each fiber family. The fibers are assumed to convect with the underlying continuum deformation as material curves. Various kinds of internal connectivity, imposing restrictions of the fiber rotations fields, are considered.

Ultrasound measurement of fiber orientation and tissue strain in excised myocardium under biaxial tension

Biaxial mechanical testing is a useful tool for determining the mechanical properties of myocardium tissues, which are anisotropic due to their layered and fibrous microstructure. Mechanical properties of the tissue are largely determined by those of the laminar myofiber sheets, whose orientations vary in a helix throughout the tissue thickness. Fiber architecture of tested tissues is usually determined post hoc by destructive histological sectioning, and the contribution of fiber kinematics to tissue-level mechanical behavior is accomplished by assuming a continuum model for the myocardium. In this work is presented simultaneous ultrasound-based measurement of fiber orientation and tissue strain in excised myocardium under biaxial tension. Two-protocol (1:1 and 1:6) testing is employed in order to probe tissue anisotropy and fiber kinematics. An ultrasound linear array (15 MHz) is scanned by rotation about the imaging axis to obtain three-dimensional backscatter data from the tissue during quasi-static biaxial deformation, from which transmural fiber orientation and tissue strain are determined by backscatter tensor imaging and 3D speckle tracking, respectively. Results illustrate feasibility of the simultaneous measurement and future utility for studying fiber mechanics in diseased tissues. Fiber rotation and elongation measured directly from ultrasound is compared to that calculated under the continuum assumption.

Analysis of nonlinear shear and damage behaviour of angle-ply laminates with Direct FE2

In this paper, non-linear shear and damage behaviour of angled ply laminates is studied and simulated with the Direct FE2 approach. The FE2 method allows dual scale modelling of composite laminates by coupling micromechanical models of Representative Volume Element (RVE) of unidirectional fibre reinforced polymer composite with a macroscale laminate level model. Angled ply laminates under uniaxial tension are chosen because their non-linear behaviour arises from matrix plasticity and fibre reorientation under tension in addition to constituent damage and becomes important particularly for large deformation. This requires additional effort to account for fibre rotation to existing homogenized ply damage models. The FE2 approach requires only constituent (matrix and reinforcement) properties as input, thus removing the need for homogenized laminate and ply-level constitutive properties. At the macroscale, the FE2 model gave good prediction of experimental stress-strain response of laminates under uniaxial tension, while concurrently, the microscale RVEs captured fibre rotation, micro-cracks and fibre rupture.

Increasing perpendicular alignment in extruded filament by an orifice embedded 3D printing nozzle

ABSTRACT The mixing of fibrous additives in the polymer base is being widely investigated for improving the mechanical properties of printed parts using fused filament fabrication (FFF). In this study, flow visualisation experiments and computational fluid dynamics (CFD) analysis were conducted on the flow channel of a nozzle with an orifice for enhancing the through-layer physical properties of the printed parts. Flow visualisation experiments were conducted on the flow channels of nozzles installed with orifices of various shapes. Using ball-milled carbon fibre in high-viscosity polydimethylsiloxane (PDMS) that imitates filament flow in FFF, the fibre angles were measured for different internal and external locations of the nozzle. The distribution of the fibre angles inside the nozzle was compared with the gradient of the flow field calculated for the same shape by CFD analysis. It was found that the orifice structure inside the nozzle increases the vertical alignment of the fibre. An abrupt increase in the extension rate at the exit of the orifice is considered to be the reason behind the rotation and vertical orientation of fibres inside the nozzle channel. Results presented in this work provide the basis for achieving improved through-plane physical properties of FFF printed parts through fibre alignment.

A Numerical Simulation Method for the One-Step Compression-Stamping Process of Continuous Fiber Reinforced Thermoplastic Composites.

Continuous fiber reinforced thermoplastic (CFRTP) composites have many advantages, such as high strength, high stiffness, shorter cycle, time and enabling the part consolidation of structural components. However, the mass production of the CFRTP parts is still challenging in industry and simulations can be used to better understand internal molding mechanisms. This paper proposes a three-dimensional simulation method for a one-step compression-stamping process which can conduct thermoplastic compression molding and continuous fiber reinforced thermoplastic composite stamping forming in one single mold, simultaneously. To overcome the strongly coupled non-isothermal moving boundary between the polymer and the composites, arbitrary Lagrangian–Eulerian based Navier–Stokes equations were applied to solve the thermoplastic compression, and a fiber rotation based objective stress rate model was used to solve for the composite stamping. Meanwhile, a strongly coupled fluid structure interaction framework with dual mesh technology is proposed to address the non-isothermal moving boundary issue between the polymer and the composites. This simulation method was compared against the experimental results to verify its accuracy. The polymer flow fronts were measured at different molding stages and the error between simulation and experiment was within 3.5%. The final composites’ in-plane deformation error was less than 2.5%. The experiment shows that this work can accurately simulate the actual molding process.

The Development of Controlled Orientation of Fibres in SFRC.

The article is focused on finding the possibility of the controlled orientation of fibres in fibre reinforced concrete constructions. This is because the controlled orientation of the fibres can contribute to the improvement of some properties of fibre reinforced concrete. The research is based on the experimental investigation of orientation control–rotation of fibres in a transparent matrix representing concrete replacement. From the conceptual model, the article continues with experimentation, data analysis and comparison of conclusions. During the experiment, a mechanical tool was developed and monitored to guide the fibres. The main monitored parameters of the levelling tool were the tips dimensions and the distance between them. The experiment results show the possibility of achieving a higher orientation of the fibres around one axis and suitable parameters of a mechanical tool.

Determination of the spherical part of the couple-stress in a polar fibre-reinforced elastic plate subjected to pure bending

This communication provides initial information and understanding of the manner in which a newly developed theoretical mechanism (Soldatos in Int J Solids Struct 202:217–225, 2020) is applied in specific boundary value problems met in polar linear elasticity of fibrous composites and thus enables the determination of the spherical part of the couple-stress tensor. In this context, it tests the applicability of the implied mechanism/method in the case that a rectangular plate reinforced by a single family of unidirectional fibres is subjected to pure bending. The problem solution is obtained for either non-polar or polar material behaviour, where fibres are considered perfectly flexible or resistant in bending, respectively, and provides clear evidence of the correctness of the principal argument that underpins the proposed method. Namely, that the general rotation field of the plate deformation differs from the fibre rotation field. That newly discovered method enables an extra energy term that emerges in the strain energy function of the fibrous composite plate to relate with the spherical part of the couple-stress tensor outside conventional equilibrium conventions. It thus leads to the determination of the spherical part of the couple-stress and its distribution throughout the plate body in a complete and comprehensive manner.

Effect of fiber orientation on the tensile properties of cross-ply laminates of PP reinforced continuous carbon fiber

This paper presents an experimental study of tensile properties, using a carbon–polypropylene uni-directional sheet with a thickness of 0.15 mm, which shows that highly non-linear stress–strain curves can be achieved with cross-angle-ply laminates. Generally, these properties are studied from the scanning electronic microscope and X-ray computed tomography. Cross-ply laminates with fiber orientation angles from 15 to 60° are investigated and it is found that there are the pseudo-ductile behavior with the fiber rotation, especially at fiber orientation angles from 30° to 60°.The Pseudo-ductile behavior is a phenomenon in which the apparent strain increases after yielding with strain hardening. It is greatly affected by the fiber reorientation in the loading direction. The fiber reorientation is allowed the plasticity of the polypropylene and thickness of each layer.

Study of Pulse Formation in an EDFL Under a Large Dispersion Variation Hybridly Mode-Locked by Graphene and Nonlinear Polarization Rotation

In this work, we present a detailed experimental study of pulse formation mechanism in an EDFL, hybridly mode-locked by use of a CVD monolayer graphene onto a D-shaped optical fiber and nonlinear polarization rotation (NPR), under a large intracavity dispersion influence (up to 100 times) ranging from 12.3 to 1382 m cavity lengths. Analyzing the spectral evolution, temporal and soliton behaviors of the pulse, our results revealed the presence of four laser operating regimes with non-soliton and soliton formation from short to ultralong cavity lengths, all related to graphene/NPR nonlinearities, dispersion and soliton propagation influences.

High-Rate In-Plane Shear Testing of IM7/8552 Using the Split Hopkinson Tension Bar

The high-rate in-plane shear properties of IM7/8552 carbon/epoxy composite material were investigated using a split Hopkinson tension bar featuring constant impedance mountings and semiconductor strain gauges in order to maximize the quality of the load signal. The in-plane shear response up to failure was evaluated using digital image correlation and correction terms for fiber rotation. The data confirmed previously determined experimental data reporting an increase of in-plane shear strength with increasing loading rate: In-plane shear strengths of 135 and 175 MPa were measured for strain rates of 320 and , respectively. The results indicate that a Johnson–Cook-type semilogarithmic scaling law can be used to describe the evolution of in-plane shear strength with increasing loading rate.

Universal features of the shape of elastic fibres in shear flow

Abstract

Effect of muscle stimulation intensity on the heterogeneous function of regions within an architecturally complex muscle.

Skeletal muscle has fiber architectures ranging from simple to complex, alongside variations in fiber-type and neuro-anatomical compartmentalization. However, the functional implications of muscle subdivision into discrete functional units remain poorly understood. The rat medial gastrocnemius has well-characterized regions with distinct architectures and fiber type composition. Here, force-length and force-velocity contractions were performed for two stimulation intensities (supramaximal and submaximal) and for three structural units (whole muscle belly, proximal region, and distal region) to assess the effect of muscle compartmentalization on contractile force-length-velocity relationships and optimal speed for power production. Additionally, fiber strain, fiber rotation, pennation, and architectural gearing were quantified. Our results suggest that the proximal and distal muscle regions have fundamentally different physiological function. During supramaximal activation, the proximal region has shorter (8.4 ± 0.8 mm versus 10.9 ± 0.7 mm) fibers and steeper (28.7 ± 11.0° versus 19.6 ± 6.3°) fiber angles at optimum length, and operates over a larger (17.9 ± 3.8% versus 12.6 ± 2.7%) range of its force-length curve. The proximal region also exhibits larger changes in pennation angle (5.6 ± 2.2°/mm versus 2.4 ± 1.5°/mm muscle shortening) and architectural gearing (1.82 ± 0.53 versus 1.25 ± 0.24), whereas the distal region exhibits greater peak shortening speed (96.0 mm/s versus 81.3 mm/s) and 18-27% greater optimal speed. Overall, similar patterns were observed during submaximal activation. These regional differences in physiological function with respect to the whole muscle highlight how variation in motor recruitment could fundamentally shift regional functional patterns within a single muscle, which likely has important implications for whole muscle force and work output in vivo.NEW & NOTEWORTHY We show that muscle compartmentalization can influence whole muscle contractile properties, with slower-fibered proximal rat medial gastrocnemius undergoing larger changes in pennation angle and architectural gearing, whereas the faster-fibered distal region achieves greater peak and optimal shortening velocity, and power output. Consequently, regional variation in motor recruitment can fundamentally influence functional patterns within a single muscle.

Measurements of length effects on the dynamics of rigid fibers in a turbulent channel flow

Nonspherical particles such as fibers are commonly dispersed by turbulent boundary layer flows encountered in industry as well as our daily living environment. Fiber length has an effect on the orientation, translation, and rotation of fibers. In this experimental study it was found that irrespective of fiber length, mean squared fiber tumbling rates strongly increased in the buffer layer, but remained constant in the log-layer and the wake region. A clear length effect was observed as longer fibers tumbled at higher rates than shorter ones.

Stable dual-wavelength laser incorporating polarization-maintaining erbium-doped fiber

A stable dual-wavelength erbium-doped fiber laser is proposed and experimentally demonstrated. The mode competition in the gain medium was suppressed by enhancing the polarization hole burning mechanism through incorporation of polarization maintaining erbium-doped fiber and nonlinear polarization rotation. The fiber laser displayed high stability with lasing side-mode suppression ratios of 60.69 and 60.57 dB. Additionally, the negligible peak power fluctuation of 0.01 dB was achieved at 1557.17 and 1560.19 nm with both peak powers of 0.23 mW and 3-dB bandwidth of 0.028 and 0.025 nm, respectively. These findings provide insights for an enhanced seed laser source design for remote dual-wavelength fiber laser applications.

A six-node prismatic solid finite element for geometric nonlinear problems in elasticity

The present work deals with an extended six-node prismatic 3D solid finite element to the analysis of nonlinear geometrical problems. The kinematic formulation is based on a virtual Space Fiber Rotation (SFR) concept which conducts to improve the displacement fields with additional displacement terms, presenting rotational degrees of freedom (DOFs). Once the standard and patch tests for linear validation are previously achieved, the present element is assessed again for large displacement and moderate rotation. For this purpose, the total Lagrangian approach is used and the Green–Lagrange strain/Piola–Kirchhoff​ stress tensors are considered. The material behavior considered in this work is restricted to Saint-Venant–Kirchhoff model for 3D large displacements elasticity To demonstrate the efficiency and accuracy of the developed finite element model, extensive and standard nonlinear benchmarks are presented. The obtained results show a good convergence and accuracy compared to similar finite elements and consequently well capability of the present element to deal with geometric nonlinear problems, including prediction of several limit points.

Analysis of carbon fiber alignment in a polydimethylsiloxane matrix flowing in an orifice channel

Owing to their remarkable physical properties compared to those of the other conventional materials, polymer composites are gaining increasing attention. In addition, it is well known that fiber-type additives are more effective in enhancing the mechanical and thermal properties of composites than other types of additives. However, the additive fibers tend to align in certain directions during the molding process and significantly affect the anisotropy of the medium. To understand the additive alignment and orientation during an injection molding process, we performed a flow visualization experiment and compared the fiber alignment with the flow field calculated from a computational fluid dynamics simulation. A mixture of polydimethylsiloxane and carbon fibers was utilized as the working fluid inside an orifice channel, which together approximated a molten polymer composite flow in a mold during the polymer fabrication process. Observation of rotation of fibers in the flow visualization images was quantified and compared to the velocity gradient fields. The magnitudes of the extension and shear rates were found to be responsible for perpendicular and parallel alignments of fibers inside the orifice channel.