Fiber Interface Research Articles

Insights into the effects of different inorganic fillers on the electrochemical performances of polymer solid electrolytes

Compared with polymer electrolyte, organic/inorganic composite solid electrolyte (CSE) shows greater advantage in solid lithium battery. The choice of inorganic filler in composition, morphology and conductivity determines the different electrochemical performance of CSE, which affects the ion migration and interface compatibility of electrolyte. Therefore, we compared inorganic fillers (LLZO particles, LLZO fibers, Al2O3 particles and Al2O3 fibers) into the polypropylene oxide (PPO) polymer to study the different effects of these four fillers on the properties of CSE. The results show that fibrous fillers have a long-distance ion transport path compared with particles, the active filler LLZO fiber has higher conductivity than the inert filler Al2O3 fiber, which greatly improves the ionic conductivity of the composite electrolyte (4.59 × 10−4 S cm−1). In addition, the existence of LiF component builds a high-strength solid electrolyte interface to protect lithium metal, especially the Li-Al-O formed at the interface of Al2O3 fiber better guarantees the stability of lithium, and solves the problem of dendrite growth and interface compatibility.

The hierarchical layer with dynamic imine bonds on carbon fiber surface to simultaneously improve interface and electromagnetic shielding properties of carbon fiber reinforced thermoplastic composites

Constructing surface hierarchical layer is regarded as an effective surface modification of carbon fibers (CFs) to enhance their composites mechanical properties. However, this method usually deteriorates the intrinsic properties of CF and the hierarchical layer is not fully compatible with thermal processing of the polymer. Here, a novel hierarchical layer consisting of polydopamine, polyethyleneimine and multi-walled carbon nanotubes without damages to CF was successfully decorated on CF surface (CNT@PP-CF) for simultaneously enhancing the mechanical and the electromagnetic interference (EMI) shielding properties of CF reinforced polyamide 66 (PA66) composite. The CNT@PP hierarchical layer with dynamic imine bonds enhanced the interfacial wettability and bonding between CF and PA66 during thermal processing. Compared with that of untreated-CF, the interfacial shear strength and tensile strength of CNT@PP-CF/PA66 composite were increased by 52.3% and 19.2%, respectively. Meanwhile, the EMI shielding performance was enhanced by 89.6%. This improvement would be ascribed to the dynamic imine polar groups and heterogeneous interfaces in the hierarchical layers which enhanced the conductive and dielectric losses of composites. Our research provided a novel approach based on dynamic covalent bond exchanges to achieve the functional and structural integration of CF reinforced thermoplastic resin composites.

Fast response characteristics of fiber Bragg grating temperature sensors and explosion temperature measurement tests

Transient temperature measurement technology with fast response, harsh measurement environment, and high technical challenges has attracted research interest in the field of temperature measurement. Based on the differential equation of heat conduction at the interface of an optical fiber, the dynamic-response-time formula of the optical fiber was derived, the dynamic response capability of the optical fiber with different diameters was analyzed, and the transient thermal response simulation of the optical fiber was conducted. The theoretical dynamic test response times of optical fibers with diameters of 80, 125, and 145 µm were 30.21, 60.78, and 85.97 ms, respectively. Fast-response fiber Bragg grating (FR-FBG) temperature sensors were designed and manufactured by femtosecond-fabricated FBGs with diameters of 80 and 125 µm. The average response times of the 80 and 125 µm-FR-FBG temperature sensors were 33.2 and 65.3 ms, and the errors between the data and theoretical values were 9.89 % and 7.44 %, respectively. From explosion experiments, it is concluded that the femtosecond grating can be applied to the monitoring of rapid temperature response during explosion, and the response time is related to the diameter of the grating.

Study of the effect of strain rate on the in-plane shear and transverse compression response of a composite ply using computational micromechanics

The use of composite materials for structures subjected to impacts requires a deep understanding about the dynamic behaviour of the material. To this end, a physically-based computational micromechanics simulation tool has been developed to predict failure initiation in a composite ply over a wide range of strain rates. The computational micromechanics framework incorporates constitutive models for the fibre, matrix and fibre-matrix interface, which are partly calibrated with novel micromechanical testing techniques. The simulation tool was applied to two matrix-dominated deformation modes of the ply: transverse compression and in-plane shear. The comparison of simulation and experimental results at coupon level have revealed a change in failure initiation mechanism of the composite ply with strain rate, which was then corroborated through observation of the fracture surfaces on the samples.

Analysis on the turning point of dynamic in-plane compressive strength for a plain weave composite

Experimental investigations on dynamic in-plane compressive behavior of a plain weave composite were performed using the split Hopkinson pressure bar. A quantitative criterion for calculating the constant strain rate of composites was established. Then the upper limit of strain rate, restricted by stress equilibrium and constant loading rate, was rationally estimated and confirmed by tests. Within the achievable range of 0.001/s–895/s, it was found that the strength increased first and subsequently decreased as the strain rate increased. This feature was also reflected by the turning point (579/s) of the bilinear model for strength prediction. The transition in failure mechanism, from local opening damage to completely splitting destruction, was mainly responsible for such strain rate effects. And three major failure modes were summarized under microscopic observations: fiber fracture, inter-fiber fracture, and interface delamination. Finally, by introducing a nonlinear damage variable, a simplified ZWT model was developed to characterize the dynamic mechanical response. Excellent agreement was shown between the experimental and simulated results.

Enhanced Insulation Strength of Meta-Aramid Paper by Co-Modification of Chopped Fiber With Plasma Discharge and Coupling Agent

The interface of fibers and fibrids is a key factor for the insulation strength of meta-aramid paper. In this article, a co-modification method of plasma discharge and coupling agent treatment for chopped fibers is proposed. By optimizing the plasma treating time, the surface hydroxyl groups are introduced to facilitate the grafting of coupling agents. Among three kinds of coupling agents, including amino-propyl-triethoxy-silane (AP), glycidyletheroxy-propyl-triethoxy-silane (GP), and mercapto-propyl-triethoxy-silane (MP), AP shows the best effect on improving the article breakdown strength, which reaches 28.3 kV/mm, 25% higher than the unmodified one. The modified papers showed compact paper structures, reductions of electrical conductivity, and deepening of carrier trap curve. Through the molecular dynamics (MD) simulation, we found that the coupling agent containing hydrogen bond (H-bond) donors rather than acceptors, namely AP, is easier to form new interface H-bonds with precipitated fibrids and does not consume intrinsic H-bonds with chopped fibers, and thus performs better on the fiber–fibrids interface interaction.

Multiscale Study of the Effect of Fiber Twist Angle and Interface on the Viscoelasticity of 2D Woven Composites.

Time and temperature affect the viscoelasticity of woven composites, and thus affect their long-term mechanical properties. We develop a multiscale method considering fiber twist angle and interfaces to predict viscoelasticity. The multiscale approach is based on homogenization theory and the time-temperature superposition principle (TTSP). It is carried out in two steps. Firstly, the effective viscoelasticity properties of yarn are calculated using microscale homogenization; yarn comprises elastic fibers, interface, and a viscoelastic matrix. Subsequently, the effective viscoelasticity properties of woven composites are computed by mesoscale homogenization; it consists of homogenized viscoelastic yarns and matrix. Moreover, the multiscale method is verified using the Mechanics of Structure genome (MSG) consequence. Finally, the effect of temperature, fiber twist angle, fiber array, and coating on either the yarn's effective relaxation stiffness or the relaxation moduli of the woven composite is investigated. The results show that increased temperature shortens the relaxation time of viscoelastic woven composites, and fiber twist angle affects tensors in the relaxation stiffness matrix of the yarn; the coating affects the overall mechanical properties of woven composites as well.

One-dimensional grating coupler on lithium-niobate-on-insulator for high-efficiency and polarization-independent coupling.

A metal-based one-dimensional grating coupler on an x-cut lithium-niobate-on-insulator wafer structure for a polarization-independent fiber interface is designed and demonstrated. By using a metal-based plasmonic mode, the diffractive angle for the two polarized modes in the lithium niobate ridge waveguide can be tuned to be the same. The polarization dependence of the grating coupler therefore can be effectively reduced. The fabricated device exhibits -3.56-dB and -4.08-dB peak coupling losses per coupler at 1573 nm for the TE and TM modes, respectively. The polarization-dependent losses are less than 0.69 dB in a 44-nm wavelength range. The demonstrated grating coupler can serve as a polarization-independent optical fiber interface on lithium-niobate-on-insulator and facilitate on-chip polarization diversity applications.

Tribological properties of hemp fiber reinforced polylactic acid bio-composites: effect of different types of modification methods

In this study, green composites are prepared with 30 wt.% hemp fibers reinforced polylactic acid (PLA) to enhance the impact and tribological properties. Different surface treatments of alkali and silane, compatibilizer of maleic anhydride (MA), and blends of thermoplastic polyurethane (TPU) and poly (butylene succinate) were applied to improve interfacial adhesion between fibers and matrix. Hemp-reinforced PLA bio-composites were fabricated and characterized by hardness, impact strength, wear, and friction properties. The tribological tests of the injection-molded components were performed under two different loads (10 N and 20 N) as dry-sliding linearly reciprocating motion per ASTM G133. Modified composites gave better tribological properties than unmodified composites. While no remarkable improvement was observed in the hardness value of untreated fiber-reinforced composite, alkali-treated composite reached up to 43% improvement in hardness value. In general, as the load increased, weight loss increase was observed in all composites. Unmodified bio-composite exhibited a very low weight loss and specific wear rate (SWR) compared to neat PLA under 10 N load. The SWR of the MA bio-composite had the lowest value for both loads (10 N and 20 N) compared to the other bio-samples. The TPU blended bio-composite exhibited the highest impact strength (22.96 kJ m−2) after pure PLA (26.5 kJ m−2). Therefore, due to surface treatments and blends applied to the fibers, some composites’ hardness and wear resistance were increased while the impact strength and friction coefficient was decreased. Especially silane surface treatment and MA compatibilizer application increased the wear resistance of composites. When the scanning electron microscope images were examined, it was revealed that the fiber and matrix interface bonding was good, and the fibers were firmly embedded in the matrix. Furthermore, forming a protective thin film layer formed by the polymer debris from the surface during dry-sliding increased the wear performance of the bio-composites.

Modification of UHPC Matrix and Fiber Surface for Improving the Mechanical Performance of Ultra-High-Performance Fiber-Reinforced Concrete

In this study, filler and silica fume were substituted by Liquid crystal display glass powder (LCDGP) and nanosilica, respectively, to improve the performance of ultra-high- performance fiber-reinforced concrete. In addition, the surface of steel fiber was modified with ethylenediaminetetraacetic acid (EDTA) solution to improve the interfacial friction between the fiber and Ultra-high-performanceconcrete (UHPC) matrix. Both LCDGP and nanosilica reacted with calcium hydroxide to form hydrates, and the fiber surface roughness increased owing to the EDTA treatment. When LCDGP was used, the compressive strength decreased owing to a decrease in packing density; however, the compressive and tensile strengths of Ultra-high-performance fiber-reinforced-concrete (UHPFRC) were improved on using nanosilica. It was observed that the surface modification of the fiber increased the friction force between the UHPC and fiber interface; therefore, it was more effective in improving the tensile strength than the compressive strength.

Reinforcing interlaminar interface of carbon fiber reinforced metal laminates by graphene

Fiber metal laminas (FMLs) are disadvantaged by weak interlaminar strength limiting their application where dynamic loads are expected. In this study, graphene platelets (GnPs) were employed to strengthen the interlaminar interface in carbon fiber (CF) metal laminates. GnPs within range of 0–1 wt% were added into epoxy resin via ultrasonication. GnPs-based FML samples were prepared by wet lay-up method and tested under flexural loading, short beam shear and single lap shear. The reinforcing mechanism and failure modes were investigated. The results show that 0.5 wt% of GnPs increases the flexural strength and interlaminar shear strength by 39.7% and 53.2%, respectively. In addition, molecular dynamics (MD) simulations concluded that the addition of low content of GnPs increases the elastic modulus of the matrix and improves the resin adsorption on the surface of carbon fiber and Al sheets. The results from both the experimental and MD simulation indicate that adding GnPs can effectively improve the interlaminar mechanical properties of FMLs. In principle, the research method in this paper can be applied to the study of FMLs with other nanomaterials.

A Low-Flow Fiber-Optic Flowmeter Based on Bending Measuring Using a Cladding Fiber Bragg Grating

A low-flow flowmeter based on the bending measurement of a cladding fiber Bragg grating (CLFBG) has been proposed and demonstrated. The CLFBG is fixed in a cantilever beam structure composed of a spring and a circular target. A femtosecond laser side-illumination technique was utilized to ensure that the grating inscription remains close to the core–cladding interface of the multi-cladding fiber (MCLF). The cladding resonance presents fiber bending dependence because of the asymmetrical distribution of the CLFBG along the fiber cross section. The force exerted on the circular target by the slow flow rate of the fluid on the order of mm/s bends the fiber, which changes the peak intensity of the cladding mode. The experimental results show that the sensor responds in the range of 0–87 mm/s and has extremely low-temperature cross-sensitivity. The proposed sensor has potential application prospects in high-precision, low-start flow measurement and can be applied to oil pipelines, downhole, and other fields.

Acoustic emission of the fracture behaviors of epoxy foam composites reinforced by bamboo fibers

The epoxy foam composites reinforced by unidirectional bamboo fibers were prepared and their mechanical property was examined by tensile test. The fracture morphology was observed by an environmental scanning electron microscopy (ESEM) and the fracture behaviors were quantitatively analyzed based on the acoustic emission (AE). The results indicated that the fiber reinforced foam (FRF) composites displayed much higher strength and toughness that are 131.3% and 223.5% higher than the pristine unfilled epoxy foam (PF), respectively. The mechanical behaviors of FRF during the fracture process were mainly the failure of porous matrix covered on the fiber interface, which took a proportion of 72.2%. The fiber dissociations and fiber breakage took 19.6% and 8.2%, respectively. The structure-property relationships bridged by AE and the fractography were investigated, and the strategies on strengthening and toughening the porous polymer composites were discussed.

Molecular dynamics simulation and finite element method investigation of PTFE/carbon fiber composite tribological properties

The mechanical parameters of polytetrafluoroethylene (PTFE), microstructures of carbon fiber (CF) and PTFE-CF interface were calculated based on the density function theory, molecular dynamics and finite element simulations. Then the friction models of GCr15-PTFE/CF composite were constructed, and the friction mechanisms of PTFE/CF composite were analyzed. The results show that the friction coefficients of composite materials containing different CF defect ratios are almost the same, indicating that the defect ratio has little influence on the friction coefficient. The position of CF in the PTFE matrix has a great impact on CF damage; the closer it is to the upper specimen during friction, the more serious the damage. In addition, the disordered structure was observed to have the most serious damage.

Effect of fibre orientation on the light scattering during laser transmission welding

During laser welding of thermoplastic (LTW) composites reinforced with short fibres, a divergence of the laser beam is observed due to internal refraction of the beam at each matrix–fibre interface. This phenomenon leads to scattering of the laser beam in this heterogeneous medium, resulting in reduction of energy reaching the weld interface. This work presents a numerical study of the effect of fibre orientation in fibre-reinforced composites during the laser transmission welding simulation. A three dimensional (3D) numerical structure is generated to take into account the real microstructure of a composite material reinforced with short fibres. The information of fibre volume fraction, fibre length distribution and fibre orientation distribution is extracted from injection moulding simulations. Fibre orientation distribution function is extracted from fibre orientation tensors. An algorithm is implemented to trace rays propagating through composite material at two scales: microscopic and macroscopic. This algorithm uses optical properties of the composite material to simulate laser beam reflection and refraction in a complex structure. Laser beam scatter at the weld interface is simulated in 3D geometries with various fibre orientation distributions. The effect of fibre orientation on the light scattering phenomenon of laser is compared for different cases of fibre orientation. The simulation results are validated experimentally.

Experimental investigations on thermo-stamping of carbon fiber reinforced polyamide 6 hat-shaped components with self-resistance electrical heating: Influence on microscopic and macroscopic properties from temperature related processing parameters

Thermo-stamping is a widely used forming process for automotive components made from fiber reinforced thermoplastic composites, but it still suffers from a variety of challenges such as long cycle time and high energy consumption. In this paper, self-resistance electrical (SRE) heating, an internal efficient heating method with the advantages of rapid heating speed and low energy consumption, was introduced into thermo-stamping for the rapid manufacturing of carbon fiber reinforced polyamide 6 (CFR-PA6) hat-shaped components. The impacts of the temperature related process parameters, preheating temperature (90 °C ∼ 220 °C) and mold temperature (20 °C ∼ 130 °C) on the shape accuracy, surface quality, microscopic morphology and mechanical properties of obtained hat-shaped components were investigated through experimental characterization. Besides, the energy-saving effect of SRE heating was also revealed compared with radiant heating, an external heating method. It is found that the defects such as fiber bundle cracks, matrix cracks and interface cracks caused by SRE heating are more serious than those caused by radiant heating, which is attributed to the effect of Joule heating, Lorentz force and dielectric breakdown. However, a high mold temperature can reduce these defects owing to the reconsolidation behavior of the hat-shaped component during the thermo-stamping process. The results show that the hat-shaped components possess a good formability and forming quality at a preheating temperature at 200 °C and mold temperature at 130 °C. Moreover, the total cycle time of thermo-stamping with SRE heating is less than 1 min and the energy consumption by SRE heating is about 9.86 % ∼12.09 % compared with radiant heating, which provides a more energy-efficient option for industrial production.

Nonlocal modeling of crack-interface interaction in a composite system

The mechanical response and the fracture phenomena in a composite system not only depend on the elastic and fracture properties of individual constituents but also on additional parameters such as fiber alignment, fiber volume fraction, interface properties and laminate layup. Fiber alignment is one such parameter that governs the design of the composite according to the purpose required. In the present work, a nonlocal approach combined with a cohesive zone model is proposed and implemented in finite element framework. The proposed model can capture different failure phenomena in a matrix- fiber system. The influence of various properties of fiber, matrix, and the fiber-matrix interface on the mechanical response of the composite system is studied. An exponential coupled cohesive zone law is considered for modeling fiber-matrix interface. Smeared representation of crack and interface are considered in the analysis. The results are validated with numerical simulations present in the literature.

Physical and Mechanical Behaviour of Silane-Modified Coconut Inflorecence/Glass Fibril-Fortified Hybrid Epoxy Composites

Augmenting concern towards effective utilization of agro waste into useful products has fomented the scientific community to look for alternate source of materials. On circular economy contemplation, natural fibers extricated from agro waste have a potential headway towards evolution of newer materials. Natural fiber hybridized with glass fiber and fortified with epoxy matrix has been found to be a promising material with unique characteristics to suit a wide variety of applications. The hydrophilic natural fibers have a resistance to bind with the polymer matrix; as a result, interfacial adhesion is limited, thereby mechanical properties of the composites are not much appreciable. In this present research, the lignocellulose fibrils extracted from coconut inflorescence were subjected to three types of silane modifications, namely, KH550 (amino silane), KH560 (epoxy silane), and KH570 (methyl silane) before hybridization. The effect of silane modification on the functional groups was investigated. The KH570 silane-modified inflorescence fiber hybridized with glass fiber and fortified epoxy composites were found to exhibit utmost tensile and flexural strengths of 102.6 MPa and 166.89 MPa, respectively. FTIR analysis confirmed KH570 silane modification leads to condensation reaction between interface of fibers and matrix. SEM analysis also confronted the elimination of functional groups present in the coconut inflorescence fibers.

Effect of Reinforcing Steel Fiber on Permeability of High Strength and Ultra-Low Permeability Concrete

Information on the water permeability of materials for radioactive waste disposal in geological repositories is essential. High strength and ultra-low permeability concrete (HSULPC) is being considered as a material used to package transuranic (TRU) waste. HSULPC would be reinforced by steel fiber to increase its tensile strength and toughness, but the effect of reinforcing steel fiber on permeability is unclear. Permeability tests need to be highly accurate to determine the hydraulic properties of low permeability materials. In this study, the hydraulic conductivity of HSULPC with steel fiber using the transient pulse method. The hydraulic conductivities of HSULPC with/without steel fiber were determined to be around 10−13 to 10−11 m/s under the confining pressures between 2 and 10 MPa and pore pressure of 1 MPa constant. The results further showed that the permeability of these materials had a hysteretic dependence on the effective confining pressure. There was no remarkable difference of hydraulic conductivity between HSULPC with and without steel fiber. SEM observation revealed that HSULPC with steel fiber has isolated voids to some extent included during mixing of concrete but there are few voids on the interface of steel fiber for water channel. However, due to the higher porosity, the hydraulic conductivity of HSULPC with steel fiber is relatively higher than that without fiber. Still, the permeability of fiber reinforced HSULPC is low enough compared with Horonobe mudstone and Toki granite and would enable it to effectively confine 14C radionuclides in TRU waste.

Solution Uptake in Cylindrical Carbon-Fibre-Reinforced Polymer (CFRP) Tendons

Salt water exposure conditions relevant to carbon-fibre-reinforced polymer (CFRP) prestressed concrete structures in marine environments are investigated. The diffusion into relatively small diameter CFRP tendons can be a lengthy process so the prediction of the long-term moisture uptake using short-term experiments on thin films of epoxy would be advantageous. However, the fibre inclusions within a composite introduce complexities, and factors are typically required for correlation with pure epoxy specimens. Diffusion parameters based on moisture uptake result from CFRP tendons exposed to salt water solution at 20°C and 60°C are compared with those obtained using equivalent thin film specimens. The higher temperature is selected to accelerate the moisture uptake. It is found that the measured ratios of tendon and epoxy diffusivity were temperature dependent, and the combination of the higher temperature and salt solution leads to an increased propensity for moisture uptake in the tendon. Existing analytical models to predict the CFRP tendon diffusivity from that of a thin film of epoxy did not appear to capture the observed trends. However, predictions using a unit cell with a fibre interface zone suggest that this may be due to an increased diffusivity in the interphase region.