Reduction In Mechanical Strength Research Articles

Effect of laser energy per unit powder feed on Hastelloy-X walls built by laser directed energy deposition based additive manufacturing

Laser Directed Energy Deposition (LDED), an additive manufacture process, has many inherent advantages and is attractive particularly for fabrication of thin walled components. The present work focuses on LDED of Hastelloy-X (Hast-X) walled structures built at three different values of Laser Energy per unit Powder Feed (LEPF), i.e., 8.2 kJ/g, 10.7 kJ/g and 13.2 kJ/g. The effect of LEPF on the built walls is examined for the geometry, microstructure and mechanical properties. The variations in built wall geometry are analyzed using statistical tools along the length, cross-section and build direction. The maximum deviation along wall height and width are found at LEPF of 13.2 kJ/g and 8.2 kJ/g, respectively. The examination along the build direction shows the maximum deviation in profile at lower layers with 8.2 kJ/g and at top layers with 13.2 kJ/g. The defect free deposits having dendritic growth at all conditions is observed. The dendrites size increases with increase in LEPF. A marginal reduction in mechanical properties, i.e., average microhardness (~8%), yield strength (~3.7%) and ultimate strength (~4%) are observed with increase in LEPF. Further, temperature distribution from finite element analysis based numerical simulation is used to understand the effect of LEPF on the wall structures. An increase in preheat temperature on previous layers with increase in number of layers and LEPF is observed. The study provides an understanding on the effect of process parameters on LDED built Hast-X wall structures.

A proof of concept of a structural supercapacitor made of graphene coated woven carbon fibers: EIS study and mechanical performance

A multifunctional supercapacitor based on a graphene nanoplatelet (GNP) coated woven carbon fiber (WCF) composite has been manufactured and its electrochemical and mechanical performance has been evaluated. Specific capacitance from voltammetry tests is about three times higher than the non-coated WCFs and several orders of magnitude above neat polymer WCF composites. Furthermore, an electrochemical impedance spectroscopy (EIS) analysis has been carried out in the coated and non-coated WCF capacitors. The equivalent circuit consisted on a series/parallel resistance/constant phase elements. EIS results show that the coated samples have superior capacitor properties, confirmed by chronoamperometry tests. The values of energy and peak power densities were also significantly higher in the coated WCFs, proving higher capabilities as supercapacitors. In addition, mechanical performance of structural supercapacitor is affected by the simultaneous addition of a polymer electrolyte and GNPs, with a reduction of mechanical strength when compared to neat polymer composites. However, and due to the lower viscosity of the electrolyte, there is a higher compaction of the material promoting an increase of WCF volume fraction on the LY-PEGDGE matrix samples, leading to similar values of Young Modulus. Despite the detriment of mechanical properties, they were far above other WCF-based structural supercapacitors. The proof of concept by illuminating a LED was highly successful, proving promising capabilities as structural supercapacitors.

The effect of process parameters on the morphology, mechanical strength and electrical resistance of CW laser-welded pure copper hairpins

Manufacturing of high-performance electric motors has become a key industrial goal over recent years due to increasing demand for electrification, in particular in the automotive field. The use of windings comprising pure copper conductors with a rectangular cross section allows the overall performance of electric motors to be increased. In the present work, the influence of processing parameters on weld quality for joining of copper hairpins with near-infrared laser irradiation performed with a specific welding path. After determining a feasible operating window, the effect of process parameters on fusion zone morphology, presence of pores and mechanical and electrical properties was investigated. The results showed that high power and high welding speed lead to joints characterized by less than 1 % pores. A maximum tensile load of 490 N was achieved during tensile tests performed on specimens obtained with optimized welding parameters, with fracture taking place in the heat affected zone (HAZ). Micro-hardness profiles confirmed slight softening near the HAZ, corresponding to a reduction in mechanical strength in this region. Electrical tests highlighted a correlation between mechanical properties and the electrical resistance of the connection.

Mechanical Damage Assessment of GFRP Rebars with Different Resins due to Hydrothermal Aging

Abstract This study investigates the effect of hydrothermal aging on the properties of glass fiber reinforced polymer (GFRP) rebars manufactured with isophthalic polyester or vinylester resin and glass fiber type E. The GFRP rebars were immersed in an alkaline solution (pH 12.6) for 1000 h at different temperatures (23 and 60 oC), and their deterioration was evaluated based on microstructural and chemical changes (using SEM, DSC, XRF, and FTIR techniques), moisture absorption, and variation in mechanical properties. The results indicated an increase in the presence of voids and water absorption of the rebars with accelerated aging, with a reduction in the glass transition temperature of the resin and alteration of the chemical composition of the glass fiber. The comparison between the experimental results indicates that the rebars with matrix in vinylester resin present greater chemical resistance than the rebars with a polyester matrix. The degradation of the rebar also resulted in a reduction of approximately 6% in the tensile strength of the rebar and 2% in the modulus of elasticity. Using the damage model, it was possible to identify that the reduction in mechanical strength was associated with the simultaneous degradation of the resin and glass fiber due to the alkaline attack.

Metallurgical Properties of Blast Furnace Extruded Briquettes (BREX) Based on Hematite Concentrate

The metallurgical properties of blast-furnace ore and ore-coal extrusion briquettes (BREX) based on hematite iron ore concentrate are studied. With respect to values of hot strength brex occupy an intermediate position between sinter and pellets. The reduction capacity for brex is significantly reduced with simultaneous addition of flux and solid fuel, which may be associated with a reduction in porosity (due to clogging of pores and the formation of a surface metal crust). Brex softening temperature range is largely dependent on composition and varies widely (130–330°C). The temperature range for onset of softening for all samples tested is 860–960°C. Prior softening of brex compared with sinter and pellets occurs due to a reduction in brex mechanical strength after loss of cement bonding properties (700–750°C) caused by loss of chemically bonded water and decomposition in the solid state of ferroakermanite (cement clinker component) at 775°C. It is necessary to take into account the difference in temperatures for the onset of softening of brex, sinter and pellets when selecting a multicomponent blast furnace charge. This makes it possible to avoid an increase in temperature in the cohesion zone and to reduce the zone for indirect reduction of oxides in the process of combined smelting with pellets and sinter. The data obtained make it possible to consider hematite ore based brex as a suitable blast furnace charge component.

Influence of Water-Repellent Admixtures on the Water-Resistance of Unstabilized and Stabilized Compressed Earth Blocks

The low durability of water action has been the main issue of earth construction since ancient times. In this way, sustainable solutions are needed to improve the earthen building materials water-resistance performance without significantly changing their appearance and eco-friendly nature. This study aims at characterizing the water-resistance of compressed earth blocks (CEB) produced with or without different types of colorless water-repellent admixtures. To this end, different types of unstabilized and 8% cement stabilized CEB were protected with two post-surface treatments, namely a silane-siloxane based surface water-repellent (SWR) and a natural linseed oil (LO), as well as one olein based integral water-repellent (IWR). Unprotected reference CEB were also considered for comparison purposes. More sustainable CEB were produced with 20% replacement of earth by recycling waste building materials. The CEB were tested in terms of compressive and flexural strength, capillary water absorption, immersion absorption, water permeability, low-pressure water absorption, and water erosion resistance from drip and spray tests. The influence of the moisture content on the compressive strength was also analysed. The cement-stabilization and water-repellent treatments were able to overcome the non-water-resistant nature of unstabilized CEB. In general, the best performance was attained with SWR, followed by IWR. The LO was less effective in reducing the long-term absorption but was able to protect unstabilized CEB from light rainfall simulated conditions. Under severe water erosion, the surface treatments were less effective, but water penetration was reduced up to near 40%. The mechanical strength, total porosity, water permeability and immersion absorption were not significantly affected by water-repellent products. Moreover, the mechanical strength reduction of stabilized CEB after saturation was about 30%, regardless of the water-repellent treatment. The main contribution of water-repellent admixtures occurred in all properties involving capillary absorption.

Calcitriol-Dependent and -Independent Regulation of Intestinal Calcium Absorption, Osteoblast Function, and Skeletal Mineralization during Lactation and Recovery in Mice.

Recovery from lactation-induced bone loss appears to be calcitriol-independent, since mice lacking 1-alpha-hydroxylase or vitamin D receptor (VDR) exhibit full skeletal recovery. However, in those studies mice consumed a calcium-, phosphorus-, and lactose-enriched "rescue" diet. Here we assessed whether postweaning skeletal recovery of Vdr null mice required that rescue diet. Wild type (WT) and Vdr null mice were raised on the rescue diet and switched to a normal (1% calcium) diet at Day 21 of lactation until 28 days after weaning. Unmated mice received the same regimen. In WT mice, cortical thickness was significantly reduced by 25% at 21 days of lactation and was completely restored by 28 days after weaning. Three-point bending tests similarly showed a significant reduction during lactation and full recovery of ultimate load and energy absorbed. Although Vdr null mice exhibited a similar lactational reduction in cortical thickness and mechanical strength, neither was even partially restored after weaning. Unmated mice showed no significant changes. In micro-computed tomography scans, diaphyses of Vdr null femora at 28 days after weaning were highly porous and exhibited abundant low-density bone extending into the marrow space from the endocortical surface. To quantify, we segregated bone into low-, mid-, and high-density components. In WT diaphyses, high-density bone was lost during lactation and restored after weaning. Vdr null mice also lost high-density bone during lactation but did not replace it; instead, they demonstrated a threefold increase in low-density bone mass. Histology revealed that intracortical and endocortical surfaces of Vdr null bones after weaning contained very thick (up to 20 micron) osteoid seams, covered with multiple layers of osteoblasts and precursors. We conclude that during the postweaning period, osteoblasts are potently stimulated to produce osteoid despite lacking VDRs, and that either calcitriol or a calcium-enriched diet are needed for this immature bone to become mineralized. © 2022 American Society for Bone and Mineral Research (ASBMR).

Incorporation of Recycled Polypropylene and Fly Ash in Polypropylene-Based Composites for Automotive Applications

The principal aim of this study is to investigate the utilization feasibility of waste materials, i.e., recycled Polypropylene (PP), and fly ash in the formulation of auto parts which are commonly designed based on PP. The typical formulation of auto parts consists of PP, elastomer, filler, and compatibilizer. Various recycled PP/virgin PP ratios were considered as the matrix of the composites. It is found that the increasing concentration of recycled PP in the composite leads to a reduction in mechanical properties, particularly ductility and impact strength. However, due to a lower viscosity at the presence of recycled PP, better dispersion of filler particles, observed by SEM analysis, leading to the improvement of tensile strength. Besides, the employment of recycled material lowers the percentage of crystallinity and melting temperature. It is deduced that the deployment of 20/80 to 40/60 ratios of recycled PP/virgin PP in the composites reasonably meets the requirements for auto parts with advantages in the environmental and economic aspects. Compared to the composites filled with talc, the ductility of fly ash-filled composites is higher. The simultaneous utilization of talc and fly ash as a hybrid system brings about higher ductility, but lowers impact strength compared to talc-filled samples. Using recycled PP mixed with fly ash provides advantages in cost reduction and sustainable and environment-friendly production.

Effect of Admixtures on Mechanical Properties of Cementitious Mortar

In the current study, the primary focus is to investigate the effect of Styrene Butadiene Rubber (SBR), silica fume and fly ash on compressive and flexure strengths of cementitious mortar. Three types of specimens are prepared; the first series comprises of control specimen; the second one consists of the mortar’s specimen modified with SBR and the third one consists of the mortar’s specimen modified with SBR in a combination of fly ash and silica fumes. Mortar samples are cast in the weight ratio of 1:2.75 (cement: sand). The SBR is added at a rate of 20% of the mass of cement. The water to cement ratio (W/C) is kept at 0.5 for control specimens and the quantity of mixing water in SBR-containing samples is reduced by the same amount as the SBR is added: The adjustment is meant to obtain same consistency for all the specimens. 20% fly ash and 2.5% silica fume are added to the mortar as replacement of cement. Compressive and flexure tests are carried out according to ASTM standards. Moreover, SEM is also performed on samples at the age of 28 days. Studies reveal that SBR and SCMs reduce the mechanical strength of the mortars. SEM and EDS studies show that SBR hinders the formation of albite, whereas silica content from silica fumes and fly ash converts CaCO3 to Wollastonite (a white loose powder), which is responsible for the reduction of mechanical strength. The study also confirms that the addition of SBR in place of water hinders the formation of primary and secondary hydration products. Doi: 10.28991/cej-2020-03091610 Full Text: PDF

Highly compressible and durable superhydrophobic cellulose aerogels for oil/water emulsion separation with high flux

Nowadays high porosity aerogels are widely applied in wastewater purification, while the fragility and unversatility of nascent cellulose aerogels limited the application in oil/water filtering separation. Here, highly compressible, elastic, superhydrophobic cellulose/poly(vinyl alcohol) (PVA) composite aerogels were fabricated via combination of chemical cross-linking, freeze drying and silanization. The obtained cellulose/PVA aerogels exhibited durable superhydrophobicity with WCA of 156.6 °, even maintaining 155.0 ° after 30 days. Synergistic effects of physical entanglement, chemical cross-linking and H-bond network between cellulose and PVA molecular chains endowed the aerogels with excellent compressibility and recoverability. The aerogels exhibited maximum compressive stress of 490.7 kPa at 90% strain, even without reduction in mechanical strength under 70% compressive strain for 10 cycles. More importantly, the strengthened aerogels exhibited remarkable separation performances for both immiscible oil/water mixtures and surfactant-stabilized water-in-oil emulsions. Fascinating permeation flux of up to 7176.3 L m−2 h−1 and total separation amount as high as 4550.6 L m−2 with separation efficiency of 98.5% for water-in-cyclohexane emulsion were harvested. Thus, this work provides a green, sustainable and mass-producible cellulose-based aerogel for high-efficiency oily wastewater remediation.

Use of Raman spectroscopy to characterize the effect of nanomagnetite as an addition to Portland cement paste on mitigating internal sulfate attack

Cement pastes containing nanomagnetite and pyrite were exposed to oxygen and moisture for 90 days. The paste containing pyrite showed evidence of internal sulfate attack, through a reduction in mechanical strength and presence of microcracks with ettringite verified by FEG SEM/EDS. Nanomagnetite increased the mechanical strengths, verified by the pore filling and formation of more chemically stable compounds in the matrix, such as hydrated C4AF. One percent nanomagnetite was the most effective concentration to mitigate the effects of internal sulfate attack. Raman spectroscopy is a differentiated technique for identifying nanomagnetite, pyrite oxidation product and low crystallinity compounds, such as C-S-H.

Flexural behavior of GFRP bar-reinforced calcium aluminate cement concrete beams containing forta-ferro fibers in acidic environment

The present study is dedicated to investigating the effects of Forta-Ferro (FF) fiber and calcium aluminate cement (CAC) on the flexural behavior of concrete beams reinforced with glass fiber-reinforced polymer (GFRP) rebars subjected to acid attack. Bending tests were designed to assess the effects of the acidic environment, replacement of ordinary Portland cement (OPC) with CAC, and the addition of FF fibers on the flexural strength, the load-deflection curve, and the cracking behavior of the beam specimens. Based on the results, the optimum content of FF fibers for improving the mechanical properties of concrete, as well as the flexural behavior of beams, is 0.4%. Further, using 0.7% FF fibers proved to be very effective in controlling the mechanical strength reduction of concrete and the flexural strength of beams immersed in acid. In addition, substituting CAC for OPC enhanced the ultimate flexural capacity of the beams with and without immersion in acid. With regard to cracking behavior, the presence of FF fibers, the exposure of specimens to acid, and the replacement of OPC with CAC reduced the average width and spacing of cracks and increased the number of cracks in the beams.

Characterization of particleboard made from oil heat-treated rubberwood particles at different mixing ratios

Particleboard was produced by mixing oil heat-treated rubberwood particles at different ratios, with the goal of achieving high dimensional stability. Rubberwood particles were soaked in palm oil for 2 h and heat treated at 200 °C for 2 h. The treated particles were soaked in boiling water for 30 min to remove oil and were tested for chemical alteration and thermal characterization via Fourier-transform infrared spectroscopy and thermogravimetric analysis. Particleboard was fabricated by mixing treated rubberwood particles (30%, 50%, and 70%) with untreated particles (70%, 50%, and 30%, respective to previous percentages) and bonded with urea-formaldehyde (UF) resin. The results revealed that oil-heat treated particles had greater thermal stability than the untreated particles. The addition of oil heat treated particles improved the physical properties of the particleboard with no significant reduction in mechanical strength. However, this was only valid for ratios of 70% untreated to 30% treated and 50% untreated to 50% treated. When a ratio of 70% oil heat treated particles was used, both the physical and mechanical properties were reduced drastically, due to bonding interference caused by excessive oil content. Particleboard made with a ratio of 5:5 (treated to untreated) exhibited the best physical and mechanical properties.

The Effect of the Processing Parameters on the Properties of the Liquid Phase Spark Plasma Sintered 80Fe-20(Al + MWCNT) Magnetic Metal Matrix Nanocomposites

In this paper, the liquid phase sintering was performed using spark plasma sintering to produce iron (Fe: 80 vol%)–aluminum (Al)–multi-walled carbon nanotubes (MWCNTs) magnetic hybrid metal matrix nanocomposites. The properties of the nanocomposites were investigated by considering different parameters of materials processing. The reinforcement of MWCNT with a content of 0–2 vol% did not affect the saturation magnetization of the nanocomposites but increased the coercivity and reduced both the electrical resistivity and the mechanical transverse rupture strength. It was found that milling the powders for 24 h resulted in composite with high saturation magnetization (148.820 A·m2/kg) and high coercivity (2175.6 A/m) but further milling time had reduced the values of magnetic properties. The mixture of Fe nanoparticles and Fe microparticles in composites with a nanoparticles-to-microparticles volume ratio of 1:1 has led to the enhanced saturation magnetization up to 157.820 A·m2/kg and reduced the coercivity of 50.20% in comparison with the Fe nanoparticles based nanocomposites. That mixture exhibited good electrical resistivity but caused the reduction of mechanical strength. The post-sintering annealing has significantly improved the magnetic softness of the composites by reducing the coercivity up to 854.30 A/m and increased the saturation magnetization.

Behavior of Specialty Optical Fibers in Crude Oil Environment

To mimic extreme downhole application conditions, a series of optical fibers was aged in crude oil at a pressure of 2000 psi and temperatures of 100-300 °C. The fibers under investigation used various coatings, including dual and single acrylate, silicone/acrylate, carbon/acrylate, silsesquioxane-type hybrid, polyimide, carbon/polyimide, acrylate/PFA and polyimide/PFA. Interactions with crude oil led to swelling, delamination, and dissolution of some of the coatings, which ultimately resulted in reduction of mechanical strength of the fibers. For different coating types, the temperatures were determined above which a significant strength degradation was observed. Carbon/polyimide, acrylate/PFA, and polyimide/PFA coatings were found to be the most oil-resistant. The amount of hydrogen generated by crude oil was evaluated from the attenuation spectra collected from the immersed fibers. For this analysis, two fibers (one doped with germanium and the other with germanium and phosphorus) were utilized as sensors. Using this approach, it was possible to estimate the amount of hydrogen generated by crude oil at different temperatures.

Dapagliflozin and Liraglutide Therapies Rapidly Enhanced Bone Material Properties and Matrix Biomechanics at Bone Formation Site in a Type 2 Diabetic Mouse Model.

The aim of this study is to compare head-to-head the effects of dapagliflozin and liraglutide on bone strength and bone material properties in a pre-clinical model of diabetes-obesity. Combined low-dose streptozotocin and high fat feeding were employed in mice to promote obesity, insulin resistance, and hyperglycaemia. Mice were administered daily for 28days with saline vehicle, 1mg/kg dapagliflozin or 25nmol/kg liraglutide. Bone strength was assessed by three-point bending and nanoindentation. Bone material properties were investigated by Fourier transform infrared microspectroscopy/imaging. Although diabetic controls presented with dramatic reductions in mechanical strength, no deterioration of bone microarchitecture was apparent. At the tissue level, significant alterations in phosphate/amide ratio, carbonate/phosphate ratio, tissue water content, crystal size index, collagen maturity and collagen glycation were observed and linked to alteration of matrix biomechanics. Dapagliflozin and liraglutide failed to improve bone strength by 3-point bending or bone microarchitecture during the 28-day-treatment period. At bone formation site, dapagliflozin enhanced phosphate/amide ratio, mineral maturity, and reduced tissue water content, crystal size index, and collagen glycation. Liraglutide had significant effects on phosphate/amide ratio, tissue water content, crystal size index, mature collagen crosslinks, collagen maturity, and collagen glycation. At bone formation site, both drugs modulated matrix biomechanics. This study highlighted that these two molecules are effective in improving bone material properties and modulating matrix biomechanics at bone formation site. This study also highlighted that the resulting effects on bone material properties are not identical between dapagliflozin and liraglutide and not only mediated by lower blood glucose.

Effect of Lanthanum Addition on Grain Refinement and Mechanical Properties of Mg–9Li–3Al Alloy

The impact of lanthanum addition on the microstructural changes and mechanical characteristics of Mg–9Li–3Al + xLa alloys are studied. The alloys are fabricated through a liquid metallurgy route involving stir casting by an electrical resistance furnace. The microstructural analysis showed that the as-cast alloys primarily comprises of α-Mg and β-Li phases. Irregular distribution of Al–Li lamellar and some granular fragments MgLi2Al observed over the magnesium-rich α-phase and lithium-rich β-phase. The influence of lanthanum addition to the alloy system leads to grain refinement by forming Al11La3 and Al4La intermetallics. Among the series of cast alloys, the Mg–9Li–3Al–1La alloy exhibits excellent ultimate tensile strength—178 MPa with 10.2% elongation. Addition of 1.5 wt% La and beyond tends to coarsen the grains leading to a reduction in mechanical strength. Hot extruded Mg–9Li–3Al–1La alloy exhibited more refinement in the microstructure and breakdown of intermetallic (Al4La and Al11La3) is observed. A significant improvement in the UTS values around 39% displayed by the Mg–9Li–3Al–1La alloy extruded at a ratio of 25:1.

An Experimental Investigation of Dynamic Properties of Fiber-Reinforced Tire-Derived Lightweight-Aggregate Concrete

This paper presents the results of an experimental study to investigate dynamic properties of polypropylene fiber-reinforced concrete beams with lightweight expanded shale (ES) and tire-derived aggregates (TDA). The mixture design followed past experiences in combining ES and TDA to enhance toughness and energy absorption in flexural behavior. The new mixture also contained 2% fiber by volume to improve such properties further. Experiments included compressive testing on cylindrical specimens as well as flexural testing on rectangular specimens to verify mechanical properties of fiber-reinforced tire-derived lightweight aggregate concrete (FRTDLWAC) subject to static loading. The results of these experiments confirmed reduction of mechanical strength due to addition of TDA and improvements in flexural strength due to fiber reinforcement. The dynamic testing included non-destructive impact loads applied to flexural specimens using a standard Schmidt hammer. A high-speed camera recorded the response of the system at 200 frames per second to allow detailed observations and measurements. Interpretation of energy-based dynamic results revealed that TDA enhances energy absorption through damping in flexural behavior. Results also indicated that fiber reinforcement reduces the amount of absorbed dynamic energy, even though; it enhances the absorbed strain energy due to crack bridging effect.

Experimental Investigation of Dynamic Properties of Fiber-Reinforced Tire-Derived Lightweight-Aggregate Concrete

This paper presents the results of an experimental study to investigate dynamic properties of polypropylene fiber-reinforced concrete beams with lightweight expanded shale (ES) and tire-derived aggregates (TDA). The mixture design followed past experiences in combining ES and TDA to enhance toughness and energy absorption in flexural behavior. The new mixture also contained 2% fiber by volume to improve such properties further. Experiments included compressive testing on cylindrical specimens as well as flexural testing on rectangular specimens to verify mechanical properties of fiber-reinforced tire-derived lightweight aggregate concrete (FRTDLWAC) subject to static loading. The results of these experiments confirmed reduction of mechanical strength due to addition of TDA and improvements in flexural strength due to fiber reinforcement. The dynamic testing included non-destructive impact loads applied to flexural specimens using a standard Schmidt hammer. A high-speed camera recorded the response of the system at 200 frames per second to allow detailed observations and measurements. Interpretation of energy-based dynamic results revealed that TDA enhances energy absorption through damping in flexural behavior. Results also indicated that fiber reinforcement reduces the amount of absorbed dynamic energy, even though; it enhances the absorbed strain energy due to crack bridging effect.

Fabrication of aramid nanofiber-wrapped graphene fibers by coaxial spinning

Flexible and highly conductive fibers have attracted much attention due to their great potential in the field of wearable electronic devices, but how to achieve high flexibility while ensuring high conductivity remains a challenge. The preparation of polyelectrolyte-wrapped graphene sheath-core fibers by coaxial spinning provides a strategy to meet this challenge. However, the encapsulation of the polymer sheath results in difficulty in the reduction of graphene oxide (GO), insufficient reduction and limitations of sheath mechanical strength cause insignificant performance improvements. Here, aramid nanofiber (ANF) with excellent thermal stability and mechanical properties is selected as advanced coating materials for graphene wires, thereby realizing the reduction of GO by thermal reduction. Benefit from the combination of the excellent intrinsic characteristics of ANF and graphene, the coaxial fibers not only exhibit high conductivity, but also a significant increase in mechanical properties was achieved. In short, the core-sheath graphene fibers wrapped by ANF were successfully prepared by coaxial spinning. And our coaxial fibers are expected to be used in the field of wearable electronics due to their excellent properties of flexibility, high electrical conductivity, and easy to implement mass production.