Aerospace Industry Research Articles

Review of Wear and Mechanical Characteristics of Al-Si Alloy Matrix Composites Reinforced with Natural Minerals

Al-Si alloys are vital in the aerospace and automotive industries due to their high strength-to-weight ratio, excellent ductility, and superior corrosion resistance. These properties, along with good thermal conductivity, low thermal expansion, and enhanced wear resistance due to silicon, make them ideal for lightweight, high-performance components like engine parts exposed to harsh conditions and thermal cycling. In recent years, the development of aluminium metal matrix composites using Al-Si alloys as the base material has gathered significant attention. These composites are engineered by integrating various reinforcing particles into the aluminium matrix, which results in remarkable improvements in the wear resistance, hardness, and overall mechanical performance of the material. The stir casting process, a well-established and cost-effective method, is frequently employed to ensure a uniform distribution of these reinforcing particles within the matrix. This review delves into the influence of different types of reinforcing particles on the properties of Al-Si alloy-based AMCs. The incorporation of these reinforcements has been shown to significantly enhance wear resistance, reduce friction, and improve the overall strength and toughness of the composites, making them ideal candidates for high-performance applications in the automotive and aerospace sectors. Moreover, this review highlights the challenges associated with the fabrication of these composites, such as achieving a homogeneous particle distribution and minimizing porosity. It also discusses the latest advancements in processing techniques aimed at overcoming these challenges. Additionally, this review addresses the potential environmental and economic benefits of using natural reinforcements, which not only reduce material costs but also contribute to sustainable manufacturing practices.

Simulation and experimental thermal analysis of ultrasonic vibration-assisted high-efficiency deep grinding of γ-TiAl blade tenon

Gamma titanium-aluminum intermetallic compounds (γ-TiAl) have attracted considerable attention in the aerospace industry because of their outstanding thermal stability and broad range of properties. To analyze the grinding temperature during high-efficiency deep grinding (HEDG) and ultrasonic vibration-assisted high-efficiency deep grinding (UVHEDG) of γ-TiAl materials, both an analytical thermal model and a finite element simulation model were developed. Subsequent comparison trials between HEDG and UVHEDG were conducted to validate the accuracy of the simulation. The results show that the final prediction error can be effectively maintained within 15 %, and the temperature measurement curve fits well when an ultrasonic heat influence factor is incorporated into the 3D finite element model. The introduction of ultrasonic vibrations into the HEDG reduced the maximum grinding temperature by 39.1 %, effectively preventing grinding burns. The highest temperature consistently occurred in the top zone of the blade tenon tooth due to different heat conduction paths caused by the complex profile. This led to a 32.4 % and 31.9 % reduction in the grinding temperature in the bottom zone under HEDG and UVHEDG, respectively. The surface roughness of the machined blade tenon tooth reached 0.664 μm at the top and 0.721 μm at the bottom under UVHEDG, whereas it was 0.735 μm and 0.843 μm under HEDG.

Effects of conventional interweaving and secondary deposition on the microstructure and properties of Ti6Al4V/AA2024 alloy component fabricated by laser-directed energy deposition

The connection of dissimilar materials has always been a great challenge, especially titanium alloy and aluminum alloy, which have broad application prospects in the aerospace industry. In this work, the Ti6Al4V/AA2024 alloy component was prepared by laser-directed energy deposition (L-DED) technology based on a conventional interweaving structure, and the microstructure of four typical position interfaces was analyzed. Aiming at the problem of poor forming quality of titanium alloy in the second interweaving layer caused by high laser reflectivity of aluminum alloy, a secondary deposition process was proposed. The microstructure and mechanical properties of Ti6Al4V/AA2024 alloy component fabricated by two different processes were characterized and tested. The problems of discontinuity and penetrating cracks at the Ti6Al4V layer in the second interweaving layer are effectively tackled by secondary deposition. As a result, the mechanical property of the deposited structure can be effectively improved, of which the average compressive shear strength is 8% higher than that of the conventional interweaving Ti6Al4V/AA2024 alloy component. The stress at the Ti6Al4V/AA2024 interface presents a zig-zag distribution because of the interweaving structure, which avoids the generation of continuous stress bands and effectively inhibits the interface crack propagation.

Investigation of Titanium Nitride as an Effective Interphase for Carbon-Fiber-Reinforced Silicon Carbide Ceramic Matrix Composites.

Ceramic matrix composites (CMCs) have played a significant role in increasing the efficiency of gas turbine engines. CMCs combine the high temperature resistance of ceramics with the high mechanical strength of ceramic fibers into a single unit. Interphase layers are a crucial component in CMCs, as they prevent ceramic fibers from oxidation and introduce strengthening mechanisms into the composite. Hexagonal boron nitride and pyrolytic carbon are the most commonly used interphase layers in the aerospace industry. Other than that, very few materials have been evaluated as interphase layers. In this study, we explore the possibilities of using titanium nitride as an interphase layer in single-tow CMCs (mini composite) representative of a unidirectional composite at a smaller scale. T-300 carbon fibers were coated with TiN by atmospheric pressure chemical vapor infiltration using TiCl4, N2, and H2. The deposition temperature, precursor flow rate ratio, total precursor flow rate, and deposition time were optimized to obtain high-quality coatings. The best coating was produced at 800 °C, 4:1 H2 [TiCl4]/N2 ratio, 125 standard cubic centimeters per minute (N2 + H2 [TiCl4]) total flow precursor flow rate, and 2 h of deposition time. At these conditions, the coatings displayed good fiber coverage, good fiber adhesion, minimum fiber linkage, and minimum surface roughness. There was minimum fiber degradation after TiN coating, with a retention of 95% of the initial Young's modulus and 26% of the ultimate tensile strength of the carbon fiber. Adding the TiN interphase coating to the Cf/SiC CMC increased the ultimate tensile strength of the composite by 1122% and Young's modulus by 150%.

Novel Bis(4-aminophenoxy) Benzene-Based Aramid Copolymers with Enhanced Solution Processability.

Aramid copolymers have garnered significant interest due to their potential applications in extreme environments such as the aerospace, defense, and automotive industries. Recent developments in aramid copolymers have moved beyond their traditional use in high-strength, high-temperature resistant fibers. There is now a demand for new polymers that can easily be processed into thin films for applications such as electrical insulation films and membranes, utilizing the inherent properties of aramid copolymers. In this work, we demonstrate two novel aramid copolymers that are capable of polymerizing in polar organic solvents with a high degree of polymerization, achieved by incorporating flexible bis(4-aminophenoxy) benzene moieties into the chain backbone. The synthesized MBAB-aramid and PBAB-aramid have enabled the fabrication of exceptionally thin, clear films, with an average molecular weight exceeding 150 kDa and a thickness ranging from 3 to 10 μm. The dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) reveal that the thin films of MBAB-aramid and PBAB-aramid exhibited glass transition temperatures of 270.1 °C and 292.7 °C, respectively, and thermal decomposition temperatures of 449.6 °C and 465.5 °C, respectively. The mechanical tensile analysis of the 5 μm thick films confirmed that the tensile strengths, with elongation at break, are 107.1 MPa (50.7%) for MBAB-aramid and 113.5 MPa (58.4%) for PBAB-aramid, respectively. The thermal and mechanical properties consistently differ between the two polymers, which is attributed to variations in the linearity of the polymer structures and the resulting differences in the density of intermolecular hydrogen bonding and pi-pi interactions. The resulting high-strength, ultra-thin aramid materials offer numerous potential applications in thin films, membranes, and functional coatings across various industries.

Environmentally friendly MoS2-hBN solid lubricants: A Comprehensive Tribological Evaluation

Abstract MoS2-based solid lubricants have obtained significant attention and are extensively employed in the aerospace industry due to their desirable tribological performance. However, to enhance their performance in humid environments, MoS2 is often doped with Pb-based compounds. Considering the health and environmental concerns associated with Pb, it is necessary to develop eco-friendly alternatives. In this study, hexagonal boron nitride (hBN) has been used as a potential substitute for Pb-based dopants in MoS2-based solid lubricants and coatings with varying hBN contents (9.5, 11.5, 13.5, 15.5, and 17.5 wt.%) were applied to stainless steel substrates using a spray bonding technique. The friction and wear characteristics of the coatings were analyzed by using a ball-on-flat tribometer, employing constant load conditions. Subsequently, ex-situ analysis techniques such as scanning electron microscopy (SEM), raman spectroscopy, and atomic force microscopy (AFM) were used to characterize the coatings. The results showed that the coating with a lower hBN concentration presented improved tribological properties, which was correlated with the development of an effective MoS2-based transfer/tribo-film. This suggests that optimizing hBN content is crucial for enhancing the lubrication performance.

Failure Prediction of an Airfoil-Type Crack in Thermoelectric Coupling Materials

Airfoil-type cracks with curved surfaces and sharp tips are frequently encountered in modern engineering applications and the aerospace industry. However, such cracks significantly threaten structures due to stress concentration and further cause damage. This study investigates the theoretical analysis and failure prediction of airfoil-type cracks within thermoelectric coupling materials under the interaction of remote mechanical loads, heat flux and electric current density. By employing complex variable theory, conformal mapping methods, and the analytic continuation theorem, the full-field stress and stress intensity factors of an airfoil-type crack were determined under three different loading conditions. The results indicate that when the airfoil-shaped crack tip is subjected to horizontal compression, vertical tensile mechanical load, and both heat flux and current density parallel to the crack, the crack tip would reach a dangerous state. Additionally, the full-field stress distribution reveals stress concentration around the crack tip, which explains variations in SIFs under different external forces and shape factors. Four critical situations suppressing crack propagation under mixed loading conditions are proposed. Furthermore, using an acrylic plate and bismuth telluride alloy as examples, the critical values of external loading for the mixed-mode fracture are determined based on the strain energy density criterion. These critical values can be used to predict failure initiation, thus reducing the risk of structural failure due to airfoil cracks within thermoelectric coupling materials.

Enhancing the Lap Shear Performance of Resistance-Welded GF/PP Thermoplastic Composite by Modifying Metal Heating Elements with Silane Coupling Agent.

Thermoplastic composites are gaining widespread application in aerospace and other industries due to their superior durability, excellent damage resistance, and recyclability compared to thermosetting materials. This study aims to enhance the lap shear strength (LSS) of resistance-welded GF/PP (glass fiber-reinforced polypropylene) thermoplastic composites by modifying stainless steel mesh (SSM) heating elements using a silane coupling agent. The influence of oxidation temperature, solvent properties, and solution pH on the LSS of the welded joints was systematically evaluated. Furthermore, scanning electron microscopy (SEM) was utilized to investigate the SSM surface and assess improvements in interfacial adhesion. The findings indicate that surface treatment promotes increased resin infiltration into the SSM, thereby enhancing the LSS of the resistance-welded joints. Treatment under optimal conditions (500 °C, ethanol solvent, and pH 11) improved LSS by 27.2% compared to untreated joints.

End-of-life carbon fiber/poly(phenylene sulfide) semipreg scraps from the aerospace industry: Towards a sustainable product

End-of-Life (EoL) carbon fiber (CF)/poly(phenylene sulfide) (PPS) semipreg scraps from the aerospace industry were used for the development of new products. The scraps were cut and placed randomly in aluminum molds, with and without continuous layers of semipreg, to obtain five different laminates processed by hot compression molding. The laminates were inspected by ultrasound, followed by cutting standardized test specimens using a CNC machine. Afterward, the laminates were evaluated for thermal (differential scanning calorimetry, DSC) and mechanical properties (tensile test and interlaminar shear strength, ILSS). The morphological characteristics of fracture surfaces were evaluated by scanning electron microscopy, SEM, and optical microscopy, OM. Ultrasound inspection indicated that four laminates showed the presence of voids, flaws, defects, and internal discontinuities, some very pronounced. However, the five laminates processed did not show differences in thermal stability. The size of the scraps and the direction of the CF contributed unintentionally so that two laminates presented tensile strength values 15 % lower than the reference laminate (822 MPa) and ILSS values (64 MPa) very close to the reference. The micrographs showed the ordering and positioning of the CF/PPS semipreg layers. The results were promising and could be considered as resources for developing new products through recycling processes.

Experimental Study and Random Forest Machine Learning of Surface Roughness for a Typical Laser Powder Bed Fusion Al Alloy

Surface quality represents a critical challenge in additive manufacturing (AM), with surface roughness serving as a key parameter that influences this aspect. In the aerospace industry, the surface roughness of the aviation components is a very important parameter. In this study, a typical Al alloy, AlSi10Mg, was selected to study its surface roughness when using Laser Powder Bed Fusion (LPBF). Two Random Forest (RF) models were established to predict the upper surface roughness of printed samples based on laser power, laser scanning speed, and hatch distance. Through the study, it is found that a two-dimensional (2D) RF model is successful in predicting surface roughness values based on experimental data. The best and minimum surface roughness is 2.98 μm, which is the minimum known without remelting. More than two-thirds of the samples had a surface roughness of less than 7.7 μm. The maximum surface roughness is 11.28 μm. And the coefficient of determination (R2) of the model was 0.9, also suggesting that the surface roughness of 3D-printed Al alloys can be predicted using ML approaches such as the RF model. This study helps to understand the relationship between printing parameters and surface roughness and helps print components with better surface quality.

Effect of tool orientation on surface roughness and dimensional accuracy in ball end milling of thin-walled blades

AbstractIn the aerospace industry, high-precision components like impellers and blisks present considerable challenges in machining due to their intricate geometries and the need for reliable performance. Blades, often classified as thin-walled parts with complex, free-form surfaces, are crucial in ensuring the efficiency and safety of aircraft engines. Their geometries and materials require strict control over cutting parameters, such as tool path and orientation, to avoid deformation and maintain surface integrity. This study investigates the impact of tilt angle variation during ball end milling of Ti6Al4V thin-walled parts. Four different tilt angles (15°, 30°, 45°, and 60°) were analysed to evaluate their effect on dimensional accuracy and surface roughness. The results show that tilt angle significantly influences surface quality and dimensional precision. A tilt angle of 30° achieved the best balance between surface finish and dimensional tolerances, with flatness values ranging from 0.038 mm at 30° to 0.101 mm at 60°, representing a 152.5% increase in flatness. The findings provide practical guidelines for optimizing ball end milling of thin-walled components, emphasizing the importance of tool orientation in reducing deformation and enhancing surface quality.

Investigating the combined influence of rolling, ECAP processes, and intermediate annealing on mechanical and microstructural properties of beryllium copper alloy 25

A beryllium copper alloy 25 underwent a series of processing steps involving rolling, equal-channel angular pressing (ECAP), and subsequent annealing. This study delved into the combined effects of these processes on the microstructural evolution and mechanical properties of the deformed beryllium copper alloy 25. The investigation utilized optical microscopy, scanning electron microscopy, transmission electron microscopy, room temperature Vickers hardness testing, and tensile testing. The findings reveal a notable enhancement in the strength of the beryllium copper alloy 25 while preserving its ductility after subjecting it to six ECAP passes followed by annealing at 210 °C for 20 min, applied to the rolled sample. Initially, an increase in number of ECAP passes resulted in a gradual reduction in grain size and a weakening of the alloy's texture. This led to an increase in ultimate tensile strength up to 333.5% without reducing in percentage elongation. Notably, after six ECAP passes, the average grain size decreased from 48 µm to less than 1 µm, yielding exceptional comprehensive mechanical properties with significantly improved strength and plasticity. The resultant material exhibits promising potential for fabrication into bars and plates for a wide range of applications in aerospace and marine industries.

Unveiling the strengthening effect of Nb in Ti3SiC2/Ti25Zr25Ni25Cu25 + Nb/GH3536 brazed joint

In order to achieve the ceramic/metal brazed joint with excellent mechanical properties, many kinds of high-entropy alloy (HEA) filler have been developed to acquire the joint. However, in some HEAs with high content of active element, such as Ti25Zr25Ni25Cu25 amorphous HEA, the metallurgical reaction between active element and base materials resulted in the formation of continuous intermetallics (IMCs) layer in the brazing seam inevitably, embrittling the brazed joint. In this study, Nb element was added into Ti25Zr25Ni25Cu25 amorphous HEA filler to improve the microstructure of Ti3SiC2/GH3536 brazed joint, promoting the application of Ti3SiC2 and GH3536 in the aerospace industry. After detailed characterizations, the strengthening effect of Nb in the brazed joint was unveiled. The formation of Nb-base solid solution in the brazing seam was achieved owing to the addition of Nb, which effectively inhibited the generation of large brittle IMCs bulk. Moreover, the Nb-strengthened ZrSi2 and Ni2Ti phases were generated in the reaction zone, which was also favor in promoting the mechanical properties of brazed joints. When Ti25Zr25Ni25Cu25 amorphous HEA filler with 20 vol% Nb was applied to braze Ti3SiC2 to GH3536, a maximum value of 85.36 ± 2.39 MPa for shear strength was achieved. This study illustrates the optimization mechanism of Nb in Ti25Zr25Ni25Cu25 +Nb composite filler and promotes the further application of Ti25Zr25Ni25Cu25 in brazing system.

Aero-thermodynamic responses of a novel FGM sector disks using mathematical modeling and deep neural networks

Composite sector disks have extensive applications in aerospace industries, particularly when exposed to challenging conditions such as supersonic airflow and thermal environments. These applications leverage the superior properties of composite materials, including high strength-to-weight ratios, enhanced durability, and excellent thermal resistance, to meet the stringent requirements of aerospace operations. Multi-directional functionally graded (MD-FG) materials due to high-temperature resistance and other amazing properties in each direction have gotten plenty of attention recently. So, in this research, a thermoelasticity solution has been presented to study fundamental frequency traits of an MD-FG sector disk in supersonic airflow via both mathematics simulation and deep neural networks technique. For obtaining exact displacement fields, along with defining the changes of transverse shear strains along the system's thickness, the refined zigzag hypothesis is utilized. For obtaining the temperature-dependent equations, heat conduction relation and thermal boundary conditions of the MD-FG structure are presented. A coupled quasi-3D new refined theory (Q3D-NRT) and generalized differential quadrature method (GDQM) are presented for obtaining and solving the partial differential equations in the time-displacement domain. After obtaining the mathematics results, appropriate datasets are made for testing, training, and validation of the deep neural networks technique. Finally, the results have shown that aerodynamic pressure, temperature changes, Mach number, free stream speed, and air yaw angle have a major role in the stability/instability analyses of the thermally affected MD-FG sector disk in supersonic airflow. As an amazing outcome, increasing the sector angle, FG indexes, and temperature change lead to the reduction of the critical Mach number, and aerodynamic pressure associated with the flutter phenomenon.

Fabrication of PEI/CF composite parts with multi-angle reinforced mechanical properties by a micro-extrusion foaming FDM process

The combination of fused deposition modeling (FDM) and foaming technology enables the fabrication of complex hierarchical and lightweight parts. However, this approach is hindered by a reduction in the mechanical properties of final parts. To this end, with the aim of addressing the challenge of the fabrication of 3D-printed parts with enhanced mechanical and lightweight features, a micro-extrusion foaming FDM process using CO2 as a blowing agent was hereby established, and the carbon fiber (CF) was selected as a reinforcing filler. Compared to pure polyetherimide (PEI) parts, the longitudinal tensile strength of the PEI/CF parts with 5.0 wt% CF added increased by 30.3 %, while the interfacial bonding strength of PEI/CF-5.0 foamed parts increased by 86.3 % compared to the unfoamed parts. Furthermore, the PEI/CF-5.0 foamed parts, weighing only about 1.7 g, could bear a load of a 60 kg human body in multiple directions. Additionally, focusing on the filler orientation and the enhanced interdiffusion and entanglement of polymer chains at interfaces, the reinforcement mechanisms of the foamed parts fabricated by micro-extrusion foaming FDM process were discussed. The micro-extrusion foaming FDM process demonstrated the capability to produce lightweight parts with enhanced mechanical properties, making it a promising technology for applications in the aerospace and military industries.

Enhancing Security and Traceability in Aerospace Supply Chains through Block Chain Technology

This study explores the impact of blockchain technology on aerospace supply chains, focusing on mitigating risks such as supply chain disruptions, counterfeit parts, and regulatory compliance challenges. A mixed-methods approach was employed, combining quantitative and qualitative analysis using data sourced from publicly available databases, including the Federal Aviation Administration (FAA), the Aerospace Industries Association (AIA), the International Air Transport Association (IATA), and reports from blockchain technology providers. Descriptive analysis identified supply chain disruptions (M = 3.74, SD = 1.17) as the most significant risk, followed by counterfeit parts (M = 3.34, SD = 1.20). Structural Equation Modeling (SEM) demonstrated that part authentication and provenance tracking had the strongest impact on improving traceability (β = 0.40, p < 0.001) and transparency (β = 0.38, p < 0.001). A Cost-Benefit Analysis (CBA) revealed a positive return on investment, with cost-benefit ratios up to 2.31. Blockchain adoption was also found to reduce CO₂ emissions by up to 25%, while improving operational efficiency through shorter procurement lead times and lower administrative costs. However, regulatory misalignment and interoperability challenges remain barriers to full adoption. The study concludes that blockchain is a transformative tool for enhancing traceability, security, and sustainability in aerospace supply chains.

A HYBRID MEREC-TOPSIS APPROACH FOR THE IMPROVEMENT OF PHYSICAL VAPOUR DEPOSITED TITANIUM CARBO-NITRIDE COATING

Titanium carbo-nitride (TiCN) comes under the metal nitride group which can provide a combined property of titanium carbide (TiC) and titanium nitride (TiN) coating. TiCN Coating possess an excellent mechanical and tribological, properties which leads its application in many industries particularly in the Automotive and aerospace industries. TiCN films can be very hard and strong based on the composition and synthesis process. Physical Vapor Deposition (PVD) technique is widely used for the preparation of thin film coating because of its ability to precisely control the composition and thickness of the coatings. The properties of the developed coating significantly affect by the PVD process parameters and their levels. Multi-Criteria Decision Making (MCDM) methods are widely used in many sectors for the selection of process parameters based upon some specific criteria. In the present work TiCN coatings were synthesized by using one of the most widely used PVD method called magnetron sputtering. L16 orthogonal array was used as a design of experiment for the experimental work by varying the sputtering process parameters like bias voltage, N2 flow rate and substrate to target distance. After the synthesis, the developed films were tested using atomic force microscopy (AFM), Scanning electron microscopy (SEM), and Nanoindentation. From the characterization three response parameters such as hardness (H), Modulus of elasticity (E) and surface roughness (Ra) of the coating has been considered. A hybrid method based on improved removal effects of criteria- technique for order performance by similarity to ideal solution (MEREC-TOPSIS) approach has been considered for the for the process parameters selection. The results have also been compared with other weight calculation techniques. In all the cases it is observed that experiment no 16 and 15 have got the 1st and second rank respectively. However, experiment no 1 is the last rank in all the cases. From the correlation analysis it is found a strong positive correlation between MEREC-TOPSIS and other methods. The method provides a significant advancement in the selection of optimal parameters, ensuring enhanced coating properties crucial for industrial applications.

Extrusion 3D Printing of Intrinsically Fluorescent Thermoplastic Polyimide: Revealing an Undisclosed Potential.

Thermoplastic polyimides (TPIs) are promising lightweight materials for replacing metal components in aerospace, rocketry, and automotive industries. Key TPI attributes include low density, thermal stability, mechanical strength, inherent flame retardancy, and intrinsic fluorescence under UV light. The application of advanced manufacturing techniques, especially 3D printing, could significantly broaden the use of TPIs; however, challenges in melt-processing this class of polymer represent a barrier. This study explored the processability, 3D-printing and hence mechanical, and fluorescence properties of TPI coupons, demonstrating their suitability for advanced 3D-printing applications. Moreover, the study successfully 3D-printed a functional impeller for an overhead stirrer, effectively replacing its metallic counterpart. Defects were shown to be readily detectable under UV light. A thorough analysis of TPI processing examining its rheological, morphological, and thermal properties is presented. Extruded TPI filaments were 3D-printed into test coupons with different infill geometries to examine the effect of tool path on mechanical performance. The fluorescence properties of the 3D-printed TPI coupons were evaluated to highlight their potential to produce intricately shaped thermally stable, fluorescence-based sensors.

Fluorinated aggregated nanocarbon with high discharge voltage as cathode materials for alkali-metal primary batteries.

Due to its exceptionally high theoretical energy density, fluorinated carbon has been recognized as a strong contender for the cathode material in lithium primary batteries particularly valued in aerospace and related industries. However, CF x cathode with high F/C ratio, which enables higher energy density, often suffer from inadequate rate capability and are unable to satisfy escalating demand. Furthermore, their intrinsic low discharge voltage imposes constraints on their applicability. In this study, a novel and high F/C ratio fluorinated carbon nanomaterials (FNC) enriched with semi-ionic C-F bonds is synthesized at a lower fluorination temperature, using aggregated nanocarbon as the precursor. The increased presence semi-ionic C-F bonds of the FNC enhances conductivity, thereby ameliorating ohmic polarization effects during initial discharge. In addition, the spherical shape and aggregated configuration of FNC facilitate the diffusion of Li+ to abundant active sites through continuous paths. Consequently, the FNC exhibits high discharge voltage of 3.15V at 0.01C and superior rate capability in lithium primary batteries. At a high rate of 20C, power density of 33,694Wkg-1 and energy density of 1,250Wh kg-1 are achieved. Moreover, FNC also demonstrates notable electrochemical performance in sodium/potassium-CF x primary batteries. This new-type alkali-metal/CF x primary batteries exhibit outstanding rate capability, rendering them with vast potential in high-power applications.

The effects of MWCNT-STF on the impact resistance of fibre metal laminates

Fibre metal laminates (FMLs) have been widely used in the aerospace and transportation industries, due to their excellent impact and fatigue resistance. However, it is challenging to further improve the impact resistance of FMLs. In this study, shear thickening fluids (STFs) with different ratios of silicon nanoparticles to polyethylene glycol (PEG) were first produced to obtain the STF with optimized performance. Then, multiwalled carbon nanotubes (MWCNTs) were added to the STF to produce MWCNT-STF to further improve its shear thickening behaviour. The rheological test results have shown that the MWCNT-STF with the composition ratio of 30 wt% PEG200+0.2 wt% MWCNTs+69.8 wt% SiO2 demonstrates the best shear thickening function, with the peak viscosity being enhanced by 365 % but the critical shear rate reduced by 69 % compared with the original STF. The MWCNT-STF was then impregnated to Kevlar fabric by ultrasonic impregnation process. The experimental results show that MWCNTs contribute the best adhesion to Kevlar fabric when the ratio of MWCNT-STF to alcohol is 1:2, with the optimal add-on ratio as 53 %. The yarn pulling-out tests show that the addition of MWCNTs to STF improves the friction between the fabric yarns, which in turn increases their shear resistance. Then STF and MWCNT-STF Kevlar fabrics were integrated to FML manufacturing. The quasi-static perforation tests indicate that MWCNT-STF helps improve the specific energy absorption of the MWCNT-STF FMLs by up to 16 %, but with limited impact on the peak perforation force. More effectively, the low velocity impact tests show that the 3/2 FMLs made with 1, 2, and 3 layers of MWCNT-STF Kevlar fabric have an enhancement on their peak impact force by 20, 36 and 38 %, while on specific energy absorption by 30, 40 and 42 %, respectively, compared to 3/2 STF FMLs counterparts.