Fiber Bending Research Articles

Bionic artificial penile Tunica albuginea

Bionic artificial penile Tunica albuginea

A Mid-Infrared Ultrawide-Bandwidth Single-Polarization Single-Mode Fiber Based on a Twin-Tube Structure

A novel chalcogenide As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> fiber based on a twin-tube structure is proposed and numerically studied for mid-infrared (MIR) single-polarization single-mode (SPSM) operation. The proposed fiber consists of two identical thin-wall tubes, which are located symmetrically inside the cladding. The simulation results show that the y-polarization fundamental mode (YPFM) can be well confined between the two tube walls near the fiber center, while all of the unwanted modes, including the x-polarization fundamental mode (XPFM) and all of the higher order modes (HOMs), are effectively suppressed due to huge confinement loss (CL). The SPSM operation can be maintained in the wavelength range from 3 to 10 μm, covering almost the entire transparency region of an As <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> fiber, with the maximum YPFM CL of 8.63×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> dB/m at 10 μm. To the best of our knowledge, this is the first MIR fiber that can keep SPSM operation over such a wide wavelength region. Furthermore, the mode area of YPFM is quite small (e.g. 10.82 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at the wavelength of 6 μm), which is beneficial to realize high nonlinearity. Besides, the bending induced CL increment of YPFM at 10 μm is only 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> dB/m even when the fiber bending radius is 1 cm. Owing to the simple structure and outstanding properties, the proposed fiber has practical applications in MIR photonics and nonlinear fiber optics.

Range and strength of mechanical interactions of force dipoles in elastic fiber networks.

Mechanical forces generated by myosin II molecular motors drive diverse cellular processes, most notably shape change, division and locomotion. These forces may be transmitted over long range through the cytoskeletal medium - a disordered, viscoelastic network of biopolymers. The resulting cell size scale force chains can in principle mediate mechanical interactions between distant actomyosin units, leading to self-organized structural order in the cell cytoskeleton. Inspired by such force transmission through elastic structures in the cytoskeleton, we consider a percolated fiber lattice network, where fibers are represented as linear elastic elements that can both bend and stretch, and the contractile activity of myosin motors is represented by force dipoles. Then, by using a variety of metrics, we show how two such contractile force dipoles interact with each other through their mutual mechanical deformations of the elastic fiber network. As a prelude to two-dipole interactions, we quantify how forces propagate through the network from a single anisotropic force dipole by analyzing clusters of nodes connected by highly strained bonds, as well as through the decay rate of strain energy with distance from a force dipole. We show that predominant fiber bending screens out force propagation, resulting in reduced and strongly network configuration-dependent dipole interactions. On the other hand, stretching-dominated networks support longer-ranged inter-dipole interactions that recapitulate the predictions of linear elasticity theory. By characterizing the differences between tensile and compressive force propagation in the fiber network, we show how inter-dipole interaction depends on the dipoles' mutual separation and orientation. The resulting elastic interaction energy may mediate a force between multiple distant dipoles, leading to their self-organization into ordered configurations. This provides a potential pathway for active mechanical force-driven structural order in elastic biopolymer networks.

Effects of fiber bending section on the vibration characteristics of 3D printed CFRTP plates

Effects of fiber bending section on the vibration characteristics of 3D printed CFRTP plates

Miniature optical fiber curvature sensor via integration with GaN optoelectronics

Optical fiber curvature sensors have been considered as a promising option for human motion detection due to its good toughness, bending flexibility and anti-electromagnetic interference. However, for wearable devices, the miniature configuration is preferred, and a high integration of the light emitter, receiver and guided fiber is essential to configure the miniaturized sensing system. Here, we present a miniaturized curvature sensing system by integrating a GaN-based optoelectronic chip with the plastical optical fiber (POF). The light emitter and detector are fabricated on a GaN-on-sapphire wafer to form a tiny chip sized at 2.5 times 1.5 mm2. The on-chip photodetector (PD) effectively senses the reflected light intensity, extracting information on the fiber bending deformation. A compact curvature sensing system is demonstrated for finger motion detection with movement angles of 30–90° and frequencies of 0.4, 1, and 1.6 Hz. The results show that the monolithically integrated LED and PD chip can be combined with the POF with reliable operation. The demonstration of the monolithically integrated optoelectronic device suggests a promising potential technology for future wearable fiber optical sensor system.

Lateral crashworthiness performance of CFRP/aluminum circular tubes with mesoscopic hybrid design

Thin-walled fiber-reinforced plastic (FRP)/metal hybrid tubes exhibit superior crashworthy performance, which have shown promising prospect as collision-proof components to withstand lateral collisions. In the present work, novel hybrid tubes with alternated stacked FRP and aluminum layers hybridized at the mesoscopic scale were proposed. The lateral crashworthiness characteristics of carbon-fiber-reinforced plastic (CFRP)/aluminum hybrid circular tubes were investigated based on analytical, experimental and numerical method. To explore the effects of material composition on deformation patterns and energy absorption efficiencies, quasi-static lateral compressive tests were carried out and the results were compared. Under lateral compression, the CFRP/Al hybrid tubes were crushed progressively and stably. Large amounts of energy were absorbed through the progressive failure of the fiber and plastic bending of aluminum layers. Compared to pristine CFRP counterparts, the specific energy absorption (SEA) and crushing force efficiency (CFE) of CFRP/Al hybrid tubes increased by 45.58% and 73.68%, respectively. The peak crushing force (PCF) of CFRP/Al tubes was reduced by more than half when compared to pure CFRP tubes. Compared to experimental results, the numerical models predicted the crushing behavior and crashworthy performance with high accuracy. Additionally, an analytical model of CFRP/Al tubes was established to predict the energy absorption characteristics and the predict outcomes agreed well with the experimental results. The FRP/Al mesoscopic hybrid structures exhibited superior deformation stability and satisfactory energy absorption performance under lateral loading, overcoming the limitations of lightweight FRP materials for lateral collision protection. In sum, these findings look promising for lightweight anti-collision structural design.

Refractive index profiles and propagation losses in bent optical fibers

A better understanding of stress effects that affect the bending losses in active and passive optical fibers allows us to improve fiber system designs and helps to optimize refractive index profiles in high power, large mode area laser fibers. Bending an optical fiber affects the light in a fiber core by two different phenomena. First, the curved shape of the waveguide changes the light propagation. The second phenomenon is the refractive index change caused by the mechanical stress in a bent optical fiber. The refractive index changes due to bending stresses are estimated by the elasto-optic and stress-optic models. The light propagation in a curved waveguide can be modeled by applying the electromagnetic wave theory together with the conformally transformed refractive index profiles that include the stress effects. The modeled refractive index profiles that include the bending stress-induced index changes are compared with the refractive index profiles that were measured from actual bent optical fibers. We tested if this comparison would allow us to estimate stress-optic coefficient C2 values in stress-optic model. Measured bend loss values are compared to the bend loss values simulated with the modeled refractive index profiles.

Penetration Fracture Mechanism of Tungsten-Fiber-Reinforced Zr-Based Bulk Metallic Glasses Matrix Composite under High-Velocity Impact

In order to adapt to the launch velocity of modern artillery, it is necessary to study the fracture mechanism of the high-velocity penetration of penetrators. Therefore, the penetration fracture mode of tungsten-fiber-reinforced Zr-based bulk metallic glass matrix composite (WF/Zr-MG) rods at a high velocity is studied. An experiment on WF/Zr-MG rods penetrating into rolled homogeneous armor steel (RHA) was carried out at 1470~1650 m/s. The experimental results show that the higher penetration ability of WF/Zr-MG rods not only results from their "self-sharpening" feature, but also due to the fact they have a longer quasi-steady penetration phase than tungsten alloy (WHA) rods. Above 1500 m/s, the penetration fracture mode of the WF/Zr-MG rod is the bending and backflow of tungsten fibers. Our theoretical calculation shows that the deformation mode of the Zr-based bulk metallic glass matrix (Zr-MG) is an important factor affecting the penetration fracture mode of the WF/Zr-MG rod. When the impact velocity increases from 1000 m/s to 1500 m/s, the deformation mode of Zr-MG changes from shear localization to non-Newtonian flow, leading to a change in the penetration fracture mode of the WF/Zr-MG rod from shear fracture to the bending and backflow of tungsten fibers.

Low-Temperature Crosstalk Bending Sensor With High Sensitivity Based on a Super-Structure Long-Period Fiber Grating

A novel super-structure long-period fiber grating (SLPFG) is proposed for bending measurement with high sensitivity. The experimental and simulated results show that the number of multimode fibers (MMF) in one period influences the excited coupling mode and its coupling efficiency. Meanwhile, the bend sensitivity is increased by optimizing the number of MMFs and reaches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$17.237\,\,\text {dB}/\text {m}^{-{1}}$ </tex-math></inline-formula> . More importantly, the temperature cross-sensitivity is one order of magnitude lower than most fiber bending sensors.

Multi-mode step graded index fibers performance parameters (attenuation/dispersion/mode field) measurements by using OptiFiber simulation

Abstract This paper has clarified the positive and negative effects of 3.1% germania and 1% fluorine DS fibers in multi-mode silica profile. The group delay and the total fiber dispersion against operating wavelength for PS and various doped silica (DS) fibers are demonstrated and assured by using OptiFiber simulation. The material, waveguide and total fiber dispersions are demonstrated against wavelength for the PS fiber, 3.1% germania DS (GDS) fiber and 1% fluorine DS (FDS) fiber. Besides the mode field diameter, fiber material loss, fiber bending loss and the dispersion group delay are simulated and clarified against the operating wavelength for PS and different DS fibers. The study gives the effects of the dopant ratio of germania and fluorine on the zero dispersion wavelength shift and DS.

Strain and curvature optical fiber laser sensor based on an accurate RI-regulated FMF with high modal power balance

In this paper, a ring fiber laser sensor based on a three layered-core few modes fiber (TL-FMF) is proposed. The home-made TL-FMF is spliced with two pieces of single mode fiber (SMF) at both sides as the sensing and filtering component. In the TL-FMF, an intermediate with higher refractive index (RI) is sandwiched between a central dip and a sub-high RI layer. Due to the special RI, the TL-FMF has an equidistant modal effective RI difference and a balanced modal power of different modes, enabling a highly uniform interference spectrum. Then applying the TL-FMF in proposed ring fiber laser sensor, the sensing experimental results show that its sensitivities in strain and curvature are −2.78 pm/με and −6.17 nm/m−1, respectively, and shows an excellent characteristic of temperature insensitivity. This fiber laser sensor implements the dual-parameter measurement with anti-cross sensitivity, which offers a promising candidate in fiber fabrication monitoring, deformation measurement and bending detection.

Plastic deformation behavior of bending aluminum fiber porous material under compressive load

The 6061 aluminum alloy wires with diameters of 0.15 mm and 0.20 mm were cut into different structural sizes of 5 × 10 mm and 10 × 15 mm by a spring machine to bend the aluminum alloy fibers, one is 5 mm short side, 10 mm long side, and 1 mm arc radius, and the other is 10 mm short side, 15 mm long side, and 1 mm arc radius. Special cylindrical molds are used to prepare folding sheets with different porosities using vacuum hot pressing sintering technology. Bent aluminum fiber porous material. The gas displacement method was used to detect the pore size and pore size distribution, and the Plastic Deformation Behavior were analyzed by quasi-static uniaxial compression test. Research shows that the material presents a three-stage stress-strain curve, from the initial nonlinear elastic deformation stage to the pseudo-platform stage and the densification stage, the wire diameter and structure of the material The smaller the size, the more conducive to the densification of the silk skeleton, and the smaller the average pore size formed, the higher the compressive strength.

Multi-channel curvature sensor based on fiber bending loss wavelength and SPR.

Fiber Bragg gratings and interferometric curvature sensors are easily disturbed by axial strain and temperature, and cascaded multi-channel curvature sensing is difficult. In this letter, a curvature sensor based on fiber bending loss wavelength and the surface plasmon resonance (SPR) mechanism is proposed, which is insensitive to axial strain and temperature. In addition, fiber bending loss valley wavelength demodulation curvature improves the accuracy of bending loss intensity sensing. Experiments show that the bending loss valley of single-mode fiber with different cut-off wavelengths has different working bands which is combined with a plastic-clad multi-mode fiber SPR curvature sensor to realize a wavelength division multiplexing multi-channel curvature sensor. The bending loss valley wavelength sensitivity of single-mode fiber is 0.8474 nm/m-1, and the intensity sensitivity is 0.0036 a.u./m-1. The resonance valley wavelength sensitivity of the multi-mode fiber SPR curvature sensor is 0.3348 nm/m-1, and the intensity sensitivity is 0.0026 a.u./m-1. The proposed sensor is insensitive to temperature and strain, and the working band is controllable, which provides a new, to the best of our knowledge, solution for wavelength division multiplexing multi-channel fiber curvature sensing.

A bent fiber optic sensor based on gold nanoparticle-decorated silver film for integration of cytosensor and plasmonic photothermal therapy: A simulation study

The fiber optic surface plasmonic resonance (SPR), with the unique characteristic of miniaturized devices, high refractive index sensitivity, and intense plasmonic photothermal effect, is a promising technique for advanced biosensors in clinical medicine. Studies on the synergistic influence factors of the dual performance of refractive index sensitivity and surface heat field are benefitted for integration of cytosensor and phototherapy. Herein, a gold nanoparticle-decorated silver film (AuNPs-AgFM) was simulated as the coating to construct a bent fiber optic surface plasmonic resonance (SPR) through a Finite Element Method (FEM). Bending leads core mode to shift away from the center of curvature into the fiber cladding, which further reacted with the AgFM and AuNPs to generate the short wavelength peaks for cytosensor and long wavelength peaks for plasmonic photothermal therapy, respectively. Furthermore, the parameters of bent radius, AuNPs’ size, and thickness of AgFM were optimized considering both refractive index sensitivity and surface temperature. Under the optimal condition, the designed SPR biosensor exhibit high amplification sensitivity (AS) of − 2301.6 (1/RIU), wavelength sensitivity (WS) of 3120 (nm/RIU), and surface temperature of 54.9 ℃ under irradiation of near-infrared ray (NIR) laser. The proposed AuNPs-AgFM-based fiber optic SPR biosensor provides an alternative scheme to integrate cytosensor and phototherapy, further pushing fiber optics to clinical application.

Machine learning methods for estimating bent photonic crystal fiber based SPR sensor properties

In the recent years, the use of machine learning approaches in optical devices and fibers is increasing. However, most methods concentrate on the use of Artificial Neural Network (ANN) methods due to the ability of automatically fitting to the problem. In this work, a classical non-linear regression method, namely k-Nearest Neighbor Regression (KNNR) is proposed for determining the loss characteristics of a photonic crystal fiber (PCF) based surface plasmon resonance (SPR) sensor in the presence of a bend in either x or y direction. Although KNNR is a simple method, it is very well known that in certain systems it can out-perform ANN. It is believed that PCF based structures can be a good candidate for this comparison. In order to judge the performance of different regression techniques, we have built a database that contains 1180 samples. The dataset contains PCF structure data for non-bent(straight fiber), bent in x and y-directions. Experiments show that KNNR outperforms both ANN and Linear Least Square Regression methods even when a feature space expansion method is employed. In addition, KNNR does not require any lengthy training process, allowing it to be used instantly once the training data is available. This can be exploited to complement existing simulation techniques.

Inference of mechanical properties and structural grades of bamboo by machine learning methods

• Characterization of physical and mechanical properties of Guadua angustifolia Kunth (GAK) was conducted. • Pooling of the datasets were performed to undertake a statistical analysis using machine learning (ML) methods. • Regression for mechanical properties were determined based on ML methods based on geometrical and physical properties. • Classification ML methods were used to propose a grading for structural bamboo species such as GAK. Features such as fast–growth rate, high strength–to–weight ratio, high carbon sequestering capability amongst others, make bamboo an excellent alternative environmental–friendly construction material. Therefore, it is very important to establish the most appropriate geometrical and/or physical properties that can be used to infer capacities as well as structural grades for bamboo such as Guadua angustifolia Kunth (GAK). Thus, an extensive experimental characterization of physical and mechanical properties of GAK was conducted by two independent laboratories –with samples from the same plantation in Colombia. Pooling of the two datasets were performed in order to create a larger data and undertake a more rigorous statistical analysis using machine learning (ML) methods. In addition, regression equations of mean and characteristic values for parallel–to–fiber compression, shear and bending capacities, and flexural stiffness were determined based on ML methods employing geometrical and physical properties. Finally, ML methods were used to propose a classification method based on four capacity classes that could enable a simpler grading process for structural bamboo species such as GAK.

Thermo-stamping shear characteristics of thermoplastics based on X-ray micro-CT

ABSTRACT Understanding the thermo-stamping shear characteristics is not only essential to improve the forming quality of the glass fiber reinforced polypropylene (GFRPP) products but also critical to ensure their structure design reliability. Most previous studies primarily focused on the fiber yarn shear characteristics in the outer surface of the composite product, and omitted the shear angle variations of the inner layers, which might increase the failure risk to the product design. In this study, the U-shaped GFRPP rail was manufactured by the thermo-stamping process and scanned layer-by-layer through the X-ray micro-CT technology. Based on the scanning results, the differences in the shear angle variations of different layers at the same position, and within the same layer but different zones were analyzed, respectively. Finally, the effect of the temperature variation on the shear angle variation was analyzed by the simulation method. Results indicate that the interlaminar shear forces and slippages lead to the differences in shear angle variations among different layers. Intralaminar fiber yarn slippages and bending deformations caused the differences in shear angle variations within the same layer. The heat loss of the stamping molds resulted in a lower stamping temperature and further led to shear angle variation reduction.

Dynamic Friction-Slip Model Based on Contact Theory

In ultra-precision positioning equipment, the positioning accuracy is affected by the friction characteristics, especially the pre-slip stage. At present, the research on friction mainly includes contact theory and the dynamic friction process. There is no time variable in contact theory models, so they only apply to the stage of static contact, while the establishment of a friction dynamics model depends on parameter identification and cannot reflect the influence of a rough morphology and load. Therefore, neither theory can elucidate the ultra-precise slip mechanism. In this paper, maximum static friction force, tangential stiffness, and tangential damping models of contact surfaces were deduced through fractal contact theory. By substituting the contact parameters into the modified LuGre model, a dynamic slip model of the mask was established. Finally, the above model was verified by a reticle dynamic slip measurement system. The experimental results showed that in the pre-slip stage of the reticle, with an increase in the normal external load, the slippage of the reticle decreased. The theoretical value calculated by the model was basically consistent with the experimental value, and the slippage of the reticle mainly originated from the tangential deformation and relative sliding of the contact surface. With the increase in the normal external load, the proportion of the tangential deformation in the sliding of the entire contact surface was larger. For the change in slippage during different motion stages, the theoretical value was close to the experimental value after eliminating system errors such as vibration and fiber bending, which proved the correctness of the model in this paper.

Classification of progressive failure and mechanical behavior of dissimilar material hybrid joints at varying temperatures

This research illustrates the progressive failure mechanisms and variation in the mechanical behavior of dissimilar materials hybrid joints at elevated temperatures. For this purpose, a novel in-situ data fusion scheme was developed from experimental analysis which was validated through a coupled computational approach. The hybrid joint consisted of CFRP/Al worksheets joined through a steel bolt. The experimental analysis revealed distinct failure mechanisms in worksheets, i.e., yielding in Al sheet and a mixed failure mode in CFRP sheet while no signs of failure were observed in the steel bolt. Further, the progressive damage in the CFRP sheet was classified as a three-staged process which comprised elastic strain phase, crack initiation and progressive damage phase, and unstable fracture phase by correlating the temperature (Infrared Thermography) and strain variations (Digital Image Correlation). Further, degradation in mechanical behavior from room temperature was evaluated at three elevated temperatures, i.e., 50 °C, 75 °C, and 100 °C. A significant drop in mechanical properties (maximum strength and nominal stiffness) was noticed at high temperatures while a transition in failure mode was also evident (ply bending and pronounced fiber breakage) in comparison to the joints tested at room temperature. In computational analysis, Tsai–Wu, Maximum Stress, and Puck’s static failure criteria were coupled with the element deletion model to ascertain the critical ply and progressive damage in the joint. The experimental results were found in good agreement with the computational results in terms of critical ply and load-carrying behavior. In summary, this research helps to understand the progressive failure and variation in mechanical behavior about high temperatures in hybrid joints which can be extended to other dissimilar materials configurations as well.

Reversibility of Out‐of‐Plane Auxetic Response in Needle‐Punched Nonwovens

The utility of auxetic materials in applications such as foams and composites is contingent upon the performance of these materials under cyclic loading. Recently, several textile materials (knitted, woven, and nonwoven fabrics) have been found to exhibit auxetic properties, either through design and/or the use of a postprocessing treatment. In the wake of these advancements, this research examines the reversibility of the out‐of‐plane auxetic response in previously studied polyester fiber needle‐punched nonwovens. Herein, a heat‐compressed nonwoven is strained cyclically to different levels, and the thickness is measured before and after straining. While axial extension is found to be elastic for up to 3% strain, thickness increases (auxetic responses) are almost completely reversible for 1% axial strain and highly reversible for 2% and 3% axial strain. Irreversible changes can be clearly observed starting at strains of 2% and larger, especially for a higher number of cycles. Combining these results with the previous understanding from microscopic and tomographic imaging, possible reversible (straightening of bent fibers and fiber bundles) and irreversible (slipping or breaking of fibers) structural deformations leading to thickness changes are identified. These processes influence the magnitude of the auxetic response within and beyond the elastic strain regime, respectively.