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This study demonstrates a novel, single‐step, and low‐energy ultrasonic approach to fabricate lightweight, high‐performance flax fiber‐reinforced composites enhanced by nanotitanium dioxide coating and fly ash hollow cenospheres. This innovative approach leads to a remarkable 23% weight reduction compared with conventional composites, making it ideal for the applications demanding both lightweight and superior mechanical properties. Through dynamic mechanical testing, it is found that the composites' viscoelastic behavior, including storage modulus and damping factor, is significantly influenced by both frequency and temperature. By applying time–temperature superposition principles, the composite's dynamic properties are comprehensively characterized across a wider frequency range. A modified fractional calculus Huet–Sayegh model accurately captures the observed viscoelastic behavior. The combined effect of nanotitanium dioxide coating, which strengthens the fiber–matrix interface, and the inclusion of rigid fly ash hollow cenospheres results in significant improvements in both storage modulus (10% increase at room temperature) and peak loss factor (80% increase) compared with uncoated flax fiber‐reinforced composites. The nanocoating and cenospheres' rigid shells contribute to enhanced stiffness, while the cenospheres' hollow structure provides efficient energy dissipation mechanisms, leading to an improved damping performance. This ultrasonic approach offers a promising and sustainable method for synthesizing natural fiber nanocomposites with superior viscoelastic properties. [ABSTRACT FROM AUTHOR]

The excellent tribological properties of copper are well known, therefore it is commonly used in components whose tribological characteristics have a high impact. Thanks to the characteristics of Additive Manufacturing it is possible to manufacture parts incorporating copper particles. However, the main mechanical studies are related to performance under tensile-compression or bending conditions and the tribological properties remain understudied and this means that there is no knowledge of the possible performance of parts obtained using additive techniques with these particles. For this reason, this article proposes to carry out a study on a polymeric Additive Manufacturing process, specifically, Fused Filament Manufacturing, which is the most widely used process at present and where it is possible to obtain thermoplastic matrix filaments with different types of reinforcements. In this case, a reinforcement of metallic nature will be chosen, such as copper particles, where the properties of this material will be exploited. The aim is to find out how the basic manufacturing parameters, layer thickness and temperature, influence the tribological behaviour of the parts obtained with this process. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the effect of volume fraction of continuous carbon fiber and sample length on buckling characteristics of polysilicon. A statistical design of 12 samples were formulated with constant cross-section area of 2500 mm ^2 using Design of Experiment software (DOE). The samples were sketched using ABAQUS 2019 software, and the total buckling force each sample was estimated. The estimated buckling forces were statically evaluated as a response using DOE. The estimated forces of 3.48776e07, 4.00652e07 and 5.78142e07 newton for the simulated samples of 100 mm in length and 0,15, and 25% volume fraction respectively, is an indication of positive effect of fiber volume fraction on the necessary force for buckling. In addition, similar tendency was found in other samples (the higher fiber volume fractions the higher buckling force). However, the estimated buckling force for each sample was negatively affected with length of the sample. The result indicated a value of 4.00652E+07, 5.00447E+06 and 1.80390E+06 newton at a constant fiber volume fraction and different length of 100, 300 and 500 mm respectively. The statistical analysis of the simulated buckling force showed a signification design, and the date of one factor effect is highly supported by the simulated buckling forces. The equation of a significant design can be used to estimate the buckling force at any fiber volume fraction and sample length.

The self-resistance electrical (SRE) heating method to cure the carbon-fiber-reinforced polymer (CFRP) parts possesses the advantages of rapid and volumetric heating, low energy consumption, and low asset investment. But the current SRE heating methods are difficult to uniformly cure the shaped CFRP parts due to the non-uniformly distributed Joule heat power in the parts with a varying cross-sectional area. In this paper, an optimized multi-zone SRE heating method is proposed, in which the uniform heating and curing process of the shaped CFRP part is firstly achieved. By optimizing the orientation of the rectangular zones, the local overheating caused by the voltage gradient and current diffusion between different zones is notably suppressed. Combined with the electro-thermal numerical analysis, the influence of the positional offset of electrodes in two adjacent zones on the temperature uniformity is investigated. Based on this, an automated zone discretization algorithm and the optimal selection method of the zone orientation are established. The proposed method is numerically and experimentally validated with the typical-shaped CFRP parts, and the results are compared with that of the existing SRE heating method. The proposed method realizes that the maximum in-plane temperature difference of shaped CFRP parts is reduced by more than 80%. This method significantly improves the temperature uniformity of shaped CFRP parts during the multi-zone SRE heating process, which provides a potential solution for high-quality and efficient curing of CFRP parts. [ABSTRACT FROM AUTHOR]

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Nanofibers offer great potential for improving the mechanical performance of optically transparent composites without compromising transparency. To achieve this, the reinforcing nanofibers must be thinner than the low end of the visible light spectrum (400 nm). Herein, a self‐mixing co‐electrospinning approach was employed to prepare electrospun meshes of well‐blended nylon‐6 (PA‐6) nanofibers and poly(methyl methacrylate) (PMMA) fibers, from which composite films containing PA‐6 nanofibers with varied diameters (approximately 100–800 nm) and mass fractions (1–7 wt%) were fabricated by hot‐press molding. When the PA‐6 nanofiber content was less than 5 wt%, the mechanical properties of the PA‐6/PMMA composite remarkably improved compared to those of neat PMMA, without considerably influencing its transparency. Furthermore, the thermal stability of the PA‐6/PMMA composite was clearly improved compared to that of neat PMMA. These results suggest that this material has the potential for wider adoption in applications requiring both transparency and high mechanical properties. [ABSTRACT FROM AUTHOR]

• Procedure for ultrasonic fatigue testing of PEEK and CNT reinforced PEEK is described. • Pulsed loading and temperature monitoring are necessary to avoid specimen heating. • Servohydraulic and ultrasonic tests of CNT reinforced PEEK deliver similar lifetimes. • Very high cycle fatigue strength significantly increased with CNT reinforcement. Fatigue properties of polyetheretherketone (PEEK) and multiwall carbon nanotube (CNT) reinforced PEEK were investigated with the ultrasonic fatigue testing method. Lifetimes were measured in the high and very high cycle fatigue regime at resonance frequency 19 kHz and load ratio R = -1. Pulse-pause loading served to avoid specimen self-heating and led to effective cycling frequencies in the range from several hundred Hz to about two kHz. Stress amplitude for 50 % fracture probability at 109 cycles is 21.2 ± 4.3 MPa for unreinforced PEEK (22 % of its tensile strength) and 33.5 ± 3.5 MPa for CNT reinforced PEEK (33 % of its tensile strength). Servohydraulic fatigue tests at 22 Hz with CNT reinforced PEEK delivered fatigue lifetimes comparable to ultrasonic tests, i.e. no frequency effect and no influence of load versus displacement control was observed. Keeping specimen temperature far below the glass transition temperature, ultrasonic fatigue testing of a high temperature resistant plastic was successfully implemented. [ABSTRACT FROM AUTHOR]

Production of versatile composites is a very attractive field. Carbon containing epoxy resins are one of the most relevant reinforced plastics used for a wide number of applications. In this research, we studied the influence of five different commercial biochar samples for the selective enhancement of brittleness and ductility of an epoxy based composite. We proved the relationship between biochar morphology and composites mechanical properties with the aid of FT-IR and FE-SEM analysis. We were able to improve the neat resin mechanical properties by doubling its Young's modulus and ultimate tensile strength using a wheat straw derived material, and to increase its elongation by 40%, we used a Miscanthus derived biochar. [ABSTRACT FROM AUTHOR]

The main advantages of polymer gears compared to metal gears are low manufacturing costs for mass production, vibration damping, and there is no need for a lubricant. In the literature and guidelines, the allowable gear endurance limits for bending and contact stresses are mainly given for polyamides (PA) and polyacetals (POM). A large number of suitable polymer gear materials is available, but the standards offer little support for the lifetime calculations of polymer gears from other materials. Therefore, the testing of gear geometry and materials combinations cannot be avoided in the design of an optimal gear drive. However, gear testing is very time-consuming and expensive, especially when testing several different material combinations in different testing conditions. By applying the upgraded accelerated testing procedure, gear test time and costs can decrease significantly. Determination of the gear temperature during meshing is needed for the precise calculation of plastic gears. The presented temperature calculation model is corrected and improved with input parameters, which were determined from the test results. Accelerated tests were conducted on different combinations of reinforced and unreinforced commercially available materials: PA6, PA66, POM and PPS. Glass and carbon fiber were used for reinforcement. The research goal was characterization of different material pairs with the coefficient of friction, time strength, wear, and the failure mechanism in relation to load cycles and load level. The paper's contribution are some general guidelines for selecting polymer material for gears, such as fiber reinforcement improves the allowable stress level at up to a few million load cycles; unreinforced polymers are better for a higher number of load cycles. Also, PTFE - the internal lubricant significantly reduces a coefficient of friction if added to PA polymers, and is less efficient in combination with POM.

In this paper, the axial behaviors of reactive powder concrete (RPC) short columns confined with carbon fiber reinforced polymer (CFRP) were investigated. All the specimens have square cross section of 100 mm × 100 mm and length of 400 mm with aspect ratio 4. The experimental work consists of three groups. The first group consists of six specimens of RPC with 2% micro steel fiber, without ordinary reinforcing steel and confining by zero, one and two layer of CFRP respectively. The second group consists of six specimens of RPC with 2% micro steel fiber and minimum ordinary reinforcing steel and confining by zero, one and two layers of CFRP respectively. The third group consists of four specimens of RPC without micro steel fiber and ordinary reinforcing steel and confining by one and two layers of CFRP respectively. Experimental data for strength, longitudinal and lateral displacement and failure mode were obtained for each test. The toughness (area under the curve) for each test was obtained by using numerical integration. The RPC columns confined with CFRP showed stiffer behavior compared with RPC columns without CFRP. The ultimate load of the RPC columns with 2% micro steel fiber + two layers of CFRP + minimum ordinary reinforcement were more than that of the RPC columns with 2% micro steel fiber + minimum ordinary reinforcement and without CFRP by about 1.333.

Production of versatile composites is a very attractive field. Carbon containing epoxy resins are one of the most relevant reinforced plastics used for a wide number of applications. In this research, we studied the influence of five different commercial biochar samples for the selective enhancement of brittleness and ductility of an epoxy based composite. We proved the relationship between biochar morphology and composites mechanical properties with the aid of FT-IR and FE-SEM analysis. We were able to improve the neat resin mechanical properties by doubling its Young’s modulus and ultimate tensile strength using a wheat straw derived material, and to increase its elongation by 40%, we used a Miscanthus derived biochar.

A nonlinear numerical multiscale analysis to predict the residual shrinkage and thermal stresses arising during curing and cooling of thickwall cross-ply filament-wound cylinders of a reinforced polymer is performed at macro- and microscales using the representative volume element (RVE) of the composite. The mechanical behavior of the polymeric matrix is described by a nonlinear viscoelastic model with account of chemical shrinkage. The fiber material is considered elastic, isotropic, and temperature-independent. The maximum residual macrostresses arising during manufacture of the cylinders were calculated. The fields of residual microstresses in the RVE in three different zones across the thickness of the cylinders were found. Results of the microscale analysis showed that microstresses in some zones of RVE were several times higher than macrostresses in these areas. [ABSTRACT FROM AUTHOR]

In this paper, the effects of adding graphite on the mechanical and tribological properties of polyamide 6 (PA6)-based composites were investigated. PA6 was reinforced with graphite by varying the weight proportions. The test specimens for mechanical and tribological experiments were molded in an injection molding machine. The mechanical properties of PA6 and graphite-reinforced PA6 polymer composites were investigated in terms of tensile strength, impact and hardness tests. The PA6 composite containing 20 wt% graphite revealed the better mechanical behaviors. The wear test was observed by using a pin-on-disk machine under dry sliding conditions at 5, 10, 20 and 30 N applied load values and sliding speed of 1000, 1500 and 2000 rpm. Scanning electron microscopy was utilized to examine the worn surfaces microstructure and wear mechanisms before and after the tribological test. The results showed that the reinforced PA6 polymer composites with 20 wt% graphite enhanced the best tribological behavior. The addition of graphite enhances the life condition of normal PA6 to a greater extent. Also, this composite exhibits stronger interfacial bonding characteristics with improved wear resistance. [ABSTRACT FROM AUTHOR]

A numerical multiscale analysis to predict the residual thermal stresses occurring during cooling in thick-walled filament-wound cylinders made of a reinforced polymer at macro-and microscales is presented. Two types of contact - bonded and unbonded - between the mandrel and the composite are considered. The fields of microstresses are calculated in three different zones across the thickness of the cylinder by using the multiscale finite-element method. Results of the microscale analysis showed that the microstresses several times exceeded the macrostresses in these areas. The value and position of the maximum microstresses were found to depend on the type of contact between the mandrel and the thick-walled cylinder. [ABSTRACT FROM AUTHOR]

• P-DGEBA, a new DGEBA analog containing phosphorus, was successfully synthesized using two chemical synthesis techniques. • P-DGEBA/DGEBA blend exhibited similar rheology to epoxy resin systems; formulation was achieved without additional heating. • A technique for manufacturing high-quality carbon fabric composite laminates for flammability test has been developed. • P-DGEBA has promise as a reactive flame retardant for epoxy since it maintains mechanical characteristics. This paper describes the synthesis of a phosphorus-based flame retardant that is a chemical analog of diglycidyl ether of bisphenol A (DGEBA), as well as its incorporation as a matrix into carbon fiber laminates. Carbon fiber composites, if used for structural applications in mass transport vehicles (aircraft, trains), will require some aspects of improved fire performance to be used safely in those applications. The first phase of work involved the development of two separate synthesis routes to produce the flame retardant monomer, referred to as Phosphorus-DGEBA or simply P-DGEBA. The second step was to determine the viability of the compound's polymerization behavior through various experimental mixing formulations and curing conditions with an aliphatic amine curing agent. Differential scanning calorimetry (DSC) was used to evaluate the curing behavior of P-DGEBA when mixed with DGEBA and an aliphatic amine curing agent and dynamic mechanical analysis (DMA) was used to observe the glass transition temperature (T g) of the carbon fiber composites. Thermogravimetric analysis (TGA) was also used to investigate the thermal stability and thermal degradation behaviors of the P-DGEBA/DGEBA blends. The final step included the fabrication of composites and their flammability testing using a cone calorimeter. DMA testing for P-DGEBA measured a T g that was 10 °C higher than a DGEBA based carbon fiber composite, and DSC studies found that the P-DGEBA / DGEBA blend polymerized well with the amine curing agent. The TGA, MCC, and cone calorimeter data yielded mixed results with TGA and MCC suggesting a more condensed phase / char formation flame retardant activity for P-DGEBA, while cone calorimeter suggested a more vapor phase flame retardant activity. Overall, the P-DGEBA shows some promise as a reactive FR for epoxy + carbon fiber composites, but more study is needed. [ABSTRACT FROM AUTHOR]

Acrylic bone cement is widely used to anchor orthopedic implants to bone and mechanical failure of the cement mantle surrounding an implant can contribute to aseptic loosening. In an effort to enhance the mechanical properties of bone cement, a variety of nanoparticles and fibers can be incorporated into the cement matrix. Mesoporous silica nanoparticles (MSNs) are a class of particles that display high potential for use as reinforcement within bone cement. Therefore, the purpose of this study was to quantify the impact of modifying an acrylic cement with various low-loadings of mesoporous silica. Three types of MSNs (one plain variety and two modified with functional groups) at two loading ratios (0.1 and 0.2 wt/wt) were incorporated into a commercially available bone cement. The mechanical properties were characterized using four-point bending, microindentation and nanoindentation (static, stress relaxation, and creep) while material properties were assessed through dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, FTIR spectroscopy, and scanning electron microscopy. Four-point flexural testing and nanoindentation revealed minimal impact on the properties of the cements, except for several changes in the nano-level static mechanical properties. Conversely, microindentation testing demonstrated that the addition of MSNs significantly increased the microhardness. The stress relaxation and creep properties of the cements measured with nanoindentation displayed no effect resulting from the addition of MSNs. The measured material properties were consistent among all cements. Analysis of scanning electron micrographs images revealed that surface functionalization enhanced particle dispersion within the cement matrix and resulted in fewer particle agglomerates. These results suggest that the loading ratios of mesoporous silica used in this study were not an effective reinforcement material. Future work should be conducted to determine the impact of higher MSN loading ratios and alternative functional groups. [ABSTRACT FROM AUTHOR]

Salt-plasticized polyelectrolyte complexes of sodium polystrenesulfonate (Na-PSS) and polydiallyldimethylammonium chloride (PDADMAC) were found to be fully dense (non-porous) when hot-pressed under optimal conditions. The quality of these saloplastics is determined by the molecular weights of polyelectrolytes, the salt type and concentration, as well as processing conditions like pressure and temperature. Higher molecular weights give more compact precipitates that are easy to process while decreasing the molecular weight led to particulate ones. Both the type and concentration of salt on complex formation and doping are explored and are found to play an equally important role. The effects of individual hot-pressing parameters, namely, pressure and temperature are studied thoroughly, facilitating the formation of uniform free-standing films over a wide range of thicknesses from 8 μm to 1 mm. For the first time, saloplastics were studied as free-standing films that are dense even at the nanometer scale. In their dry states, they were brittle and strong, showing a uniform Young's modulus over a range of relevant thicknesses, while the wet states were rubbery and elastic, showing a decreasing trend with thickness. In the wet state, the inverse trend is due to the quicker drying of thin films. Within a single hot-pressing step, protruding shapes and structures from the surface were efficiently made at different length scales. Moreover, saloplastics were also successfully reinforced with thin woven and nonwoven fibers for enhanced tensile strengths, higher than conventional thermoplastics. Overall, this work demonstrates an easy approach to fabricate dense saloplastics and their unique mechanical properties. [Display omitted] • Na-PSS and PDADMAC complexes are varied using salt, concentration, molecular weight. • Optimal complexes are hot-pressed into saloplastics and parameters are studied thoroughly. • Freestanding and completely dense films over a wide range of thicknesses are made. • Tensile tests in wet and dry states show the role of water, stability, strength. • Reinforcements and profiles like chevrons are shown within single step hot-pressing. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a facile strategy for fabricating arrays of two- and three-dimensional gold nanostructures using PDMS-infiltrated polystyrene (PS) colloidal crystals. PDMS molding of colloidal crystal, gold vapor deposition, and subsequent calcination of PS produced gold thin layers over hexagonal PDMS microwell arrays with hemispherical air-voids of approximately 140nm on glass substrates. Vapor deposition of perfluoroalkylsilane thin layers improved the thermal stability of the colloidal template over 100°C, providing a route to preparation of hollow architectures with gold thin layers supported by PDMS nanostructures. Surface modification of the PDMS using poly(allylamine hydrochloride) induced two-dimensional colloidal crystals of PS and PMMA spheres through electrostatic interactions. Particle aggregation of 13nm gold nanoparticles in the PDMS microwells demonstrated a surface plasmon resonance band red-shifted to 810nm, in comparison with that on the flat surface at 720nm. [Copyright &y& Elsevier]

The mechanical and tribological behaviors of polyamide 6 (PA6) and high density polyethylene (HDPE) polyblends made using maleic anhyride polypropylene as the compatibilizing agent were studied. The compositions investigated for tribological behavior were 80 wt.% PA6–20 wt.% HDPE and 60 wt.% PA6–40 wt.% HDPE. The polyblends were reinforced with glass fiber (GF) and filled with polytetrafluoroethylene (PTFE) and copper oxide (CuO). The polymeric materials were blended using a modular intermeshing co-rotating twin-screw extruder. The reinforced composite specimens with different fiber proportions were made in a reciprocating screw injection molding machine using the blended materials as the feed stock. The friction and wear experiments were run under ambient conditions in a pin-on-disk machine with the polymer pin riding on the flat surface of a steel disk at a sliding speed of 1 ms−1 and under a nominal pressure of 0.64 MPa. The tensile strength of the polyblend with composition 80 wt.% PA6–20 wt.% HDPE increased with fiber reinforcement but the material became brittle. The maximum reductions in wear and the coefficient of friction were obtained by filling the polyblends with 10 wt.% PTFE. The fiber glass reinforcement was not found effective in lowering the already low wear rate of the polyblend. [Copyright &y& Elsevier]

• Thermolysis recycling of thermoset carbon fibre reinforced polymer (TS-CFRP) is presented. • Fibre structure preservation from end-of-life TS-CFRP waste recycling is investigated for permeability and fibre nesting behaviour. • Mechanical properties of remanufactured TS-CFRP are assessed and compared. • Improved integrity, economical value and market attractiveness of recovered carbon fibre are discussed. Recycling of thermoset carbon fibre reinforced polymer (TS-CFRP) composites using thermal processes result in recovered carbon fibres (rCF), being fluffy and losing their alignment and length, leading to a deteriorating impact on the remanufactured part mechanical properties. In this work, the thermolysis recycling process is used to preserve the fibre structure including fabric stacking sequence, fibre orientation, alignment and length from the waste TS-CFRP parts. Investigation on the rCF structures with varying fabric and stacking sequence has been conducted to understand fibre nesting, alignment disturbance and permeability characteristics for composites remanufacturing. The fibre nesting in the rCF structures affects the permeability and hence should be considered for optimising the remanufacturing process parameters. Mechanical characterisation – tensile and interlaminar shear strength – of TS-CFRP and TS-rCFRP parts has also been carried out and compared with the properties from the existing literature to understand the effect of multiple recycling on the performance of the remanufactured composite parts with preserved fibre structure. The results showed that the overall fibre structure from the waste TS-CFRP part can be preserved using the thermolysis process providing the potential to directly replace the long virgin fibres in the manufacture of products with structural value. The remanufactured composite parts retain 80~90% of the TS-CFRP modulus after multiple recycling. The reduction in tensile properties of the TS-rCFRP parts was recorded compared to TS-CFRP parts, mainly due to the removal of fibre sizing. However, after first recycling, minimal reduction in tensile properties was recorded in the subsequent recycling. [ABSTRACT FROM AUTHOR]