Bidirectional Fiber Research Articles

Fully aminated p‐polyaramid effectively strengthen and toughen Bisphenol A epoxy resin and its warp‐knitted carbon fiber composites

AbstractStemming from the cost‐effectiveness and broad applicability, many modification researches on Bisphenol A epoxy resin (DGEBA) and its carbon fiber composites have been done extensively. Here, following the concept of molecular composite, we prepared fully aminated p‐polyaramid with reactive amino side groups by polycondensation and reduction reaction, aiming to construct a molecular distribution of the reinforcement within the resin matrix and achieve a satisfactory enhancement effect. Among them, after adding 1 wt% fully aminated p‐polyaramid, Young's modulus and tensile toughness of the DGEBA epoxy resin (EP) increased significantly to 2.34 ± 0.03 GPa (+68.3%) and 4402 ± 213 kJ/m3 (+30.5%), the flexural modulus and toughness reached 4.14 ± 0.04 GPa (+42.8%) and 0.44 ± 0.01 J (+83.3%). Moreover, the Tg of EP was only decreased by 2.7°C. In addition, their warp‐knitted bidirectional carbon fiber composites also have enhancements in both flexural properties and interlaminar shear strength (all improved by more than 20%). What is noticeable is that the preparation and blending of fully aminated p‐polyaramid are simpler and more effective than most other micro‐ or nanofillers, and the dispersion is more uniform. Thus, it can act as a highly effective reinforcement and strengthen the properties of DGEBA and its carbon fiber composite materials significantly.Highlights Fully aminated p‐polyaramid is uniformly dispersed in EP by chemical bonds. DGEBA is strengthened and toughened without a significant decrease in Tg. The tensile and flexural modulus of EP is increased by 68.3% and 42.8%. Fully aminated p‐polyaramid can reinforce warp‐knitted carbon fiber composite.

Bi-directional SMF-NDF-optical/5G NR wireless converged systems

This study presents the transmission of fifth-generation (5G) new radio (NR) signals over bi-directional single-mode fiber (SMF)-negative dispersion fiber (NDF)-optical/5G NR wireless converged systems, using two cascaded reflective semiconductor optical amplifiers (RSOAs). Downstream transmission of 5G NR 16-quadrature amplitude modulation (QAM) signals achieved an aggregate net bit rate of 228.037 Gb/s, comprising 59.813, 74.766, and 93.458 Gb/s at 150, 250, and 325 GHz, respectively. The system achieved a low bit error rate (BER) and clear constellation patterns. However, systems without NDF exceed the forward error correction 7% threshold, indicating the importance of NDF in compensating for fiber dispersion. Moreover, for upstream transmission, two cascaded RSOAs are used to transmit 5G 16-QAM-orthogonal frequency division multiplexing signals, achieving a total data rate of 40 Gb/s. The use of two cascaded RSOAs in the system significantly improved upstream performance, resulting in low BERs and clear constellation patterns. This system not only achieved high data rates but also extended transmission coverage to support the deployment of advanced 5G NR applications.

Bidirectional all-PM Er-doped fiber laser based on a self-stabilized interferometer mode-locker

We demonstrate a bidirectional all polarization-maintaining (PM) Er-doped fiber laser based on a self-stabilized interferometer mode-locker. By utilizing mechanical sharing and multiplexing propagation directions, the laser has balanced bidirectional outputs and passively suppresses common-mode noise. We also investigate the intra-cavity pulse dynamics via numerical simulations, which coincides well with experimental observations. The self-stabilized interferometer compensates for the group delay difference between the polarization components induced by linear birefringence. The cross-phase modulation effect in the self-stabilized interferometer leads to asymmetric spectra. In addition, from 10 kHz to 1 MHz frequency range, the integrated RMS phase noise in clockwise (CW) and counter-clockwise (CCW) directions are 0.124 mrad and 0.14 mrad, respectively. The integrated RMS RIN in CW and CCW directions are 439 ppm and 464 ppm. Due to passive common-mode noise cancellation, the repetition frequency difference can be stabilized near 19 Hz in 2500 s gate time. The stability of the repetition frequency difference can reach a minimum value of 4.167 × 10−4 at a gate time of 100 s. This novel bidirectional all-PM Er-doped fiber laser based on a self-stabilized interferometer mode-locker can provide a new scheme for the construction of an all-PM dual-comb system.

Physical, Mechanical and Thermal Characterization of Areca, Pineapple and Glass Fiber Reinforced Polymer Composites for Aerospace Applications

In the current scenario, the focus on applying natural fiber-reinforced polymer composites in aerospace applications has increased tremendously due to their attractive characteristics such as lightweight, higher strength-to-weight ratio, good thermal stability at environmental temperatures, resistance to corrosion, sound absorbing capability and increased fuel efficiency. Further, studies on Bi-directionally oriented fiber composites have more advantages than the random or unidirectional orientation, such as uniform stress distribution and improved bonding at the interface. So, the present work focuses on using the Areca, Pineapple Leaf Fiber (PALF) and Glass fiber as the bi-directional fiber mat for reinforcing it into Epoxy polymer. The three different materials were fabricated by changing the fiber type with constant volume fraction and orientation. The martial characterization was done on the fabricated composites in order to evaluate their orientation effectiveness through density, moisture absorption, tensile, impact, hardness and thermal degradation. The bonding relationship was analyzed through a Scanning Electron Microscope. The results showed that the properties obtained were higher for the PALF composite than the areca composites due to the fact that the higher surface area of PALF fibers is confirmed through SEM analysis.

A Bidirectional Mode-Locked Fiber Laser for Asynchronous Noise-like Pulse Generation

A Bidirectional Mode-Locked Fiber Laser for Asynchronous Noise-like Pulse Generation

Improving the Performance of Bidirectional Communication System Using Second-Order Raman Amplifiers

In order to achieve low-cost scalability, the same-wavelength bidirectional (SWB) fiber communication system is a better solution. We present a detailed investigation of the performance of the different orders Raman amplifiers in same-wavelength bidirectional fiber communication systems. We discuss how to suppress the main factor affecting system performance which is Rayleigh scattering noise (RSN). By using different Raman amplifiers to construct different quasi-lossless transmission, the performance changes in the same-wavelength bidirectional fiber optic communication system were studied. On this basis, multi-channel and same-wavelength single fiber bidirectional system experiments were conducted to compare the performance of second-order Raman systems and first-order Raman systems. The results indicate that the Rayleigh scattering suppression effect of second-order Raman systems is better, and compared to first-order Raman systems, the average signal-to-noise ratio (SNR) can be increased by 2.88 dB.

Comparative study on shape memory, mechanical, and thermomechanical properties of multi‐walled carbon nanotubes and graphene nanoplatelets modified bidirectional (twill) carbon fiber polymer composites

AbstractThe research conducts a comparative analysis of epoxy/bi‐directional (twill) carbon fiber three‐phase shape memory hybrid composites modified with MWCNT and GnP, examining their mechanical, thermomechanical, and shape memory properties. Fabrication involves preparing nanoparticle‐modified epoxy nanocomposites through ultrasonication followed by hand layup technique. The findings revealed that the modified composites achieved their optimal performance at a 0.6 wt% concentration of nanoparticle, with the tensile strength and modulus increasing by 33.59% and 23.47% for 0.6 wt% MWCNT composite and by 45.94% and 25.61% for 0.6 wt% GnP composite. GnP‐modified composites outperformed MWCNT ones due to GnP's sheet structure aligning parallel to the load and larger surface area facilitating enhanced interaction with the matrix. Despite polymer modification, the shape recovery ratio values remained high, with 98.92% for unmodified composite, 97.72% for 0.6 wt% MWCNT composites, and 97.12% for 0.6 wt% GnP modified composites, all exceeding 90%, indicating no compromise in performance.

Synergistic demulsification of oil-in-water emulsion using bidirectional pulse electric field and fiber coalescence

The methods of demulsification using bidirectional pulsed electric field (BPEF) and fiber coalescence exhibit limited effectiveness under conditions of high emulsification degree of oil-in-water (O/W) mixture or low oil content. However, there is an urgent requirement for efficient O/W emulsion separation. This study investigated the synergistic demulsification of oil-in-water emulsion using BPEF combined with fiber coalescence. It explored the impact of coalesced fiber parameters, output parameters of bidirectional pulse power supply, and water quality parameters on the demulsification performance of O/W emulsion. The demulsification performance of BPEF coupled with viscose fiber was superior to that of coupling polytetrafluoroethylene (PTFE) fiber, and the 10 % fiber filling rate exhibited a better synergistic demulsification effect than the 5 % fiber filling rate. The optimal synergistic demulsification performance was achieved with a 10 % viscose fiber filling ratio, 400 V pulse voltage, 50 Hz frequency and 30 % duty ratio. The O/W emulsion with an oil content of 4100 mg/L could be reduced to 9.28 mg/L, resulting in a demulsification efficiency of 99.77 %, which was 55.98 % higher than that of BPEF. The study showed that utilizing BPEF in conjunction with fiber coalescence could be a promising approach for synergistic demulsification of O/W emulsions.

A continuum model for the mechanics of elastomeric sheets reinforced with extensible bidirectional fibers resistant to lateral pressure

We investigate the concurrent three-dimensional (in-plane and out-of-plane) deformations of fiber-reinforced composite (FRC) sheets undergoing lateral pressure. This involves the utilization of the Neo-Hookean strain energy model for the matrix material and computing the strain energy of bidirectional fibers by accounting for the stretching, bending, and twisting responses of the fibers. The kinematics of FRC are formulated within the framework of differential geometry on FRC surfaces, including the computations of the first and second gradient of deformation. By employing the variational principles, we derive the Euler equations describing the mechanics of the fiber–matrix composite system subjected to lateral pressure. The resulting three-dimensional continuum model theoretically predicts the deformation of the matrix material and it is found that the maximum deformation of matrix material occurs in the diagonal direction of the domain, yet, the center of the domain suffers weak in-plane deformation because of surface tension equilibrium. In addition, the stretching, bending, and twisting kinematics of fiber units are computed to investigate the effects of the individual fiber’s kinematics on the overall deformation of fiber meshwork. Lastly, it is found that the lateral pressure on the FRC surface induces fiber flexure in the vicinity of domain boundaries and fiber stretch inside the domain, corresponding to the intensified shrinking strain near the edges and stretching strain in the middle of the domain. The theoretical results provide phenomenologically meaningful insights into comprehending the damage patterns of the fiber-reinforced building material, the hemispherical dome shaping results of bamboo Poly (lactic) acid (PLA) composites and the out-of-plane deformation of woven fabric.

Investigating the changing dynamics of processing, temperature‐based mechanics, and flame retardancy in the transfer of ammonium polyphosphate/inorganic silicate flame retardants from epoxy resins to glass fiber composites

AbstractAlthough numerous investigations study the improvement of flame retardancy of epoxy resins using additives, maintaining the flame retardant (FRs) modes of action present in the resins upon transfer to composites is challenging. In this study, ammonium polyphosphate (APP) and inorganic silicate (InSi) are loaded at 10%, 30%, and 50% by weight, in a diglycidyl ether of bisphenol A (DGEBA) resin cured with dicyandiamide and transferred to bidirectional (BD) glass fiber (GF) composites. Although a 50% loading of the FRs impacts the curing kinetics of the resin system, the effect on the glass transition temperature of the resin system remains negligible compared to reactive FRs in the state of the art integrated into the resin's chemical structure. Increasing the FR content improved the heat release characteristics in both the resins and composites. However, the charring mode of action is completely suppressed in the formulation with 10% APP + InSi. A 30% concentration of the FRs restored the charring action in the composite and the GFs provide increased protective layer action upon transfer to the composites. This study highlights the importance of accounting for the changing dynamics related to processing and flame retardancy upon transferring FRs from resins to composites.

Influence of varying matrix/fiber concentration on mechanical properties of bi-directional carbon fiber reinforced polymer composite

The polymer composites comprising bi-directional carbon fabric incorporated in the epoxy matrix have been developed for various advanced applications in the field of automobile and aerospace sectors. The distinct advantages of using epoxy material with hardener are good adhesion, high tensile, compression and bending strengths, good corrosion, and heat resistance properties. Using carbon fiber enhances the stiffness, reduces the weight, and improves the chemical resistance apart from possessing high thermal conductivity and low coefficient of thermal expansion. Considering all the above aspects, the present work proposes to investigate the mechanical properties of carbon-reinforced epoxy composites with fiber matrix ratios of 40:60, 50:50, and 60:40 by wt% as these particular combinations have been limitedly addressed so far. The well-known hand lay-up technique has produced the laminates and the test samples prepared from the laminate are subjected to tensile, flexural, hardness, and impact strength properties. Based on the experimental work of the composites made in the laboratory, the fiber matrix ratio of 60:40 has revealed the best attributes in terms of higher mechanical strengths compared to the composites with fiber matrix ratio of 40:60 and 50:50 and the data obtained have been substantiated using scanning electron microscope analysis.

Numerical study of a bi-directional in-band pumped dysprosium-doped fluoride fiber laser at 3.2 µm

Numerical study of a bi-directional in-band pumped dysprosium-doped fluoride fiber laser at 3.2 µm

Coherent and Incoherent Breathing Solitons in a Bidirectional Ultrafast Thulium Fiber Laser

Mode‐locked lasers are prone to exhibit a wide range of dynamics, including the coherent dissipative soliton with high robustness or the possible emission of incoherent pulse bursts. Herein, it is proposed to expand the notion of dissipative breathing solitons to incoherent localized formation, which is illustrated experimentally by reporting original coherent and incoherent breathing solitons generated in a 2 μm bidirectional ultrafast fiber laser. A real‐time spectral characterization of the breathing soliton dynamics with different coherence is provided, highlighting salient features of the self‐organization. The switching between coherent breathing soliton and noise‐like pulse is also experimentally demonstrated, corresponding to the multiple transient decoherence and coherence recovery. High behavior similarity exists in bidirectional solitons evolution owing to the common gain and loss modulation. Numerical simulations using a discrete laser model validate the experimental findings. This research generalizes previous observations of breathing solitons made in the coherent case and opens up new possibilities for generating breathers in various dissipative systems.

Nano‐enhanced epoxy sandwich composites: Investigating mechanical properties for future aircraft construction

AbstractThe aviation sector is continually seeking ways to reduce the weight of aircraft structures without compromising their mechanical integrity. Lightweight materials, such as advanced epoxy sandwich composites with hybrid nanostructures, have the potential to significantly contribute to fuel efficiency, thereby addressing environmental concerns and operational costs. This research investigates the mechanical properties of hybrid sandwich polymer composites filled with silica nanoparticles (SNiPs). Epoxy isocyanate (PU) foam sandwich composites were fabricated with kevlar fiber, carbon fiber, and glass fiber, constructed by alternating inclined interply bidirectional fiber and foam layers. SNiPs were introduced into the composite system at varying percentages, such as 0, 2, 4, and 6 wt%. The study employs a systematic approach, incorporating experimental testing, to assess key mechanical parameters, including tensile strength, flexural strength, and shear strength. The test results indicate that the incorporation of SNiPs improved the mechanical properties of the composites, leading to enhanced strength, toughness, and modulus of elasticity. Incorporation of composite laminates with 4 wt% SiNPs resulted in improved three‐point bending, tensile, shear, and torsional strengths, with maximum values of ca. 64, ca. 5, ca. 2 MPa, and ca. 22 Nm, respectively. The findings contribute to the ongoing pursuit of materials that can meet the stringent demands of modern aviation, ultimately paving the way for advancements in aircraft construction and design.

High-Precision Fiber Noise Detection and Comparison over a 260 km Field Fiber Link.

In this paper, we present a high-precision optical frequency noise detection and comparison technique using a two-way transfer method over a 260 km field fiber link. This method allows for the comparison of optical frequencies between remote optical references without the need for data transfer through communication. We extend a previously established two-way comparison technique to obtain all data at the local site. Two optical carrier signals are injected into the bidirectional fiber from both ends, and one carrier is reflected back from the remote end. This enables the phase comparison of the two carrier signals at a single site without the need to transmit experimental data. The common-mode frequency noise induced by the bidirectional fiber link is detected and effectively suppressed without the need for sophisticated active fiber noise control. Our demonstration system, which uses a 260 km field fiber link and a common laser source, achieves a fractional instability of 2.5×10-17 at 1 s averaging time and scales down to 3.5×10-21 at 8000 s. This scheme offers the distinct advantage of completing the comparison at a single site, eliminating the need for remote data transfer via communication. This method is expected to enhance reliability for high-precision frequency comparisons between remote optical clocks and advanced atomic clocks.

Solitons, bifurcation and chaotics in a bidirectional mamyshev oscillator

Bidirectional mode-locked fiber lasers are able to deliver two outputs of pulses in the clockwise (CW) and counterclockwise (CCW) directions, having important applications in dual-comb spectroscopy, asynchronous optical sampling and terahertz time-domain spectroscopy. In this paper, we have experimentally demonstrated an all-fiber Er/Yb-doped bidirectional passively mode-locked Mamyshev oscillator (MO) without an external seed. Two stable mode-locked states with remarkable different characteristics are observed by adjusting the pump power. The transition process between the two mode-locked states shows chaotic behaviors, which are further investigated with numerical simulations based on the Ginzburg-Landau equation. The bidirectional MO proposed in this work is not only a good laser source, but also a good platform to study soliton dynamics, system bifurcation, and chaos in ultrafast fiber laser systems.

Biomechanical considerations of semi-anatomic glass fiber-reinforced (GFRC) composite implant for mandibular segmental defects: A technical note

ObjectivesThe aim of this study was to investigate the selected biomechanical properties of semi-anatomic implant plate made of biostable glass fiber-reinforced composite (GFRC) for mandibular reconstruction. Two versions of GFRC plates were tested in vitro loading conditions of a mandible segmental defect model, for determining the level of mechanical stress at the location of fixation screws, and in the body of the plate. MethodsGFRC of bidirectional S3-glass fiber weaves with dimethacrylate resin matrix were used to fabricate semi-anatomic reconstruction plates of two GFRC laminate thicknesses. Lateral surface of the plate followed the contour of the resected part of the bone, and the medial surface was concave allowing for placement of a microvascular bone flap in the next stages of the research. Plates were fixed with screws to a plastic model of the mandible with a large segmental defect in the premolar-molar region. The mandible-plate system was loaded from incisal and molar locations with loads of 10, 50, and 100 N and stress (microstrain, με) at the location of fixation screws and the body of the plate was measured by strain gauges. In total the test set-up had four areas for measuring the stress of the plate. ResultsNo signs of fractures or buckling failures of the plates were found during loading. Strain values at the region of the fixation screws were higher with thick plate, whereas thin plates demonstrated higher strain at the body of the plate. Vertical displacement of the mandible-plate system was proportional to the loading force and was higher with incisal than molar loading locations but no difference was found between thin and thick plates. ConclusionGFRC plates withstood the loading conditions up to 100 N even when loaded incisally. Thick plates concentrated the stress to the ramus mandibulae region of the fixation screws whereas the thin plates showed stress concentration in the angulus mandibulae region of the fixation and the plate itself. In general, thin plates caused a lower magnitude of stress to the fixation screw areas than thick plates, suggesting absorption of the loading energy to the body of the plate.

Effects of Fiber Orientation on the Mechanical Properties of Bidirectional Woven Kevlar Epoxy Composite

Objectives: This study focuses on the mechanical behavior of different fiber orientations of bi-directional woven Kevlar fabric to improve the mechanical properties of the Kevlar epoxy composite materials. Methods: Here in this paper hand moulded composites are fabricated with the Bidirectional plain-woven Kevlar-49, Epoxy resin LY 556 and hardener HT972 and the configuration of the layer was symmetrical and contained 6 plies which arranged as C- (0/45/-45/45/-45/0), B- (0/60/-60/60/-60/0). The standard ASTM D 3039 for tensile test, ASTM D790 for flexural test and ASTM D256 was followed for the laboratory test. F indings: Polymer composite materials are popular due to its weight strength ratio. Bidirectional woven fiber is used for the analysis, where different fiber orientations are compared. From the analysis it is observed that, mechanical properties vary with different fiber orientations. Novelty: In this paper, tensile modulus, flexural modulus, and absorbed impact energy observed in the laboratory to find out the suitability of the Kevlar composite as a building material. The findings of this research are expected to have practical implications for the development of stronger and more durable polymer fiber composites in various structural applications. Keywords Kevlar fiber, Epoxy, Tensile test, Woven fabric, Fiber orientation

Optically synchronized unidirectional optical amplifier-based coherent optical fiber links.

We report on the realization of a unidirectional transmission-based bidirectional erbium-doped fiber amplifier (UTB-EDFA) for the coherent optical fiber links. By applying an optical phase-locked loop (OPLL) between the two unidirectional EDFA (Ui-EDFA) paths, the annoying uncorrelated phase noise between the two paths can be largely suppressed. Promisingly, we can independently optimize the gains of the UTB-EDFAs for bidirectional transmissions, resulting in higher net gain acquired compared with the conventional single-path bidirectional EDFA (SPBA)-based ones. We demonstrate that the fractional frequency instability of the UTB-EDFA-based scheme can be decreased by 26.3% over the most asymmetrical 100 km two-way optical frequency comparison (TWC) system compared with the SPBA-based ones and, more importantly, can acquire higher net gain for unevenly distributed sub-links over ultra-long fiber links, such as 1000 km, by independently optimizing the gains. This technique paves the way for the applications of large-scale fiber networks.

Experimental evaluation of one and two-directional wicking geotextile stabilized permeable base

Incorporating wicking geotextiles significantly reduces the moisture levels in road bases under saturated and unsaturated conditions, improving the strength of granular materials and reducing water-related pavement damage. Despite the numerous well-documented applications of wicking geotextiles, most practical uses or research predominantly feature wicking fibers oriented in a single direction. Although theoretically incorporating multidirectional wicking fibers should enhance drainage efficiency, empirical studies on the impact of bidirectional fibers on geotextile drainage performance are scarce. A year-long comparative study was conducted in Shenzhen to examine the influence of fiber orientation. In this study, the moisture content in the aggregate base of a permeable sidewalk across three distinct test sections – single-directional, bidirectional, and no wicking geotextile – determined that two-directional wicking geotextiles are superior to their one-directional counterparts in reducing the volumetric water content in the granular base.