Polyurethane-based composites (PUCs) are promising materials for stretch-forming dies used in aircraft skin components; however, their limited load-bearing capacity and insufficient wear resistance under severe conditions remain major challenges. In this work, graphite powder (GP) was incorporated into a polyurethane matrix to enhance its compressive and tribological performance. PUCs with different GP contents were fabricated by room temperature casting. Static compression tests, dynamic compression experiments using a split Hopkinson pressure bar, and wear tests under various normal loads were systematically performed. The results demonstrate that both elastic modulus and compressive strength first increase and then decrease with increasing GP content. When the GP content reached 5%, the composite exhibited the highest static compressive strength of 141.41 MPa, representing a significant improvement compared with the GP-free composite. Under dynamic loading, the composite containing 5% GP achieved the maximum dynamic compressive stress, which was 635.99 MPa at an impact pressure of 0.2 MPa. Moreover, composites with higher GP content exhibited markedly enhanced wear resistance under elevated normal loads. Scanning electron microscopy observations confirmed that GP promoted the formation of a stable lubricating transfer film, leading to a transition from severe adhesive wear to mild wear behavior.
To assess the feasibility of using bamboo–plastic composites in electrical insulation applications, the effect of fly ash—a type of highly productive coal power solid waste—on the in-service performance of bamboo–plastic composites for insulation (hereafter referred to as bamboo–plastic insulating materials) was investigated. The evaluation was based on four standard criteria for solid insulation materials: water repellency, mechanical properties, electrical properties, and voltage resistance. The results showed that with increasing fly ash content, all four properties initially improved and then declined. The maximum reductions in water absorption and the dielectric loss factor were 20.7% and 35.8%, respectively, while the maximum increases in contact angle, tensile strength, flexural strength, insulation resistance, surface flashover voltage, and breakdown voltage were 25.0%, 21.3%, 14.4%, 36.1%, 35.9%, and 7.5%, respectively. Following the breakdown, the microstructure of the bamboo–plastic insulating materials, irrespective of fly ash content, exhibited continuous conductive channels and irregularly distributed pitting.
The study reports the preparation and characterisation of non-apparel grade wool–natural rubber (NR) composites. Non apparel textile grade wool obtained from Malpura sheep (highly coarse) and Chokla sheep (medium coarse) were converted in to hand woven fabric in a conventional handloom. Both the fabrics were milled, scoured and coated with different natural rubber latex concentrations through padding method. The latex-coated wool fabrics were then vulcanised at higher temperature and pressure to prepare wool–NR composites. The physical and mechanical properties of the developed wool fabrics and wool–NR composites such as fibre loading, tensile strength, elongation, Young's modulus, tear strength, porosity, hardness, abrasion resistance, moisture content, static and dynamic frication and water diffusion were analysed. The composites were further characterised with Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The aging properties of composites due to accelerated thermal, UV exposure and soil degradation was also performed. Upon comparing the physico-mechanical properties, it is observed that the DRC (Dry Rubber Content) was found to be the governing factor in determining the mechanical properties of the composites. While coating with same natural rubber latex concentration, the mechanical properties of the medium coarse wool–NR composite was found to be higher as compared to the highly coarse wool–NR composite. Prolonged exposure to high temperature and UV radiation caused a significant reduction in mechanical properties of the composites. Upon accelerated soil burial for 120 days, the pristine wool fabric was found to be fully decomposed meanwhile, the composites with high rubber content exhibited less degradation.
A naturally occurring two-dimensional (2D) nano-SiO 2 derived from phytolith minerals was employed as a reinforcing filler for polymethyl methacrylate (PMMA) composites. Unlike conventional 2D materials, this SiO 2 does not require exfoliation, significantly reducing processing complexity and cost. The nanosheets were modified using 3-aminopropyltriethoxysilane (KH-550) and incorporated into PMMA via melt blending. FTIR analysis indicated that the 2D nano-SiO 2 was successfully modified by KH-550 and effectively grafted onto the PMMA chains, while SEM analysis revealed a distinct layered structure and strong interfacial adhesion, contributing to a porous morphology. Mechanical tests demonstrated that at an optimal loading of 1.06 wt.%, the composite achieved a tensile strength of 72.74 MPa and an impact toughness of 70.23 kJ/m 2 , representing increases of approximately 93.8% and 100.6% compared to pure PMMA. DSC analysis showed a slight increase in the glass transition temperature, indicating modest enhancement in thermal stability. These findings suggest that natural 2D nano-SiO 2 serves as a low-cost filler with a remarkable reinforcing effect on the mechanical performance of PMMA-based composites, exhibiting great potential for engineering applications.
The strip placement method was used to manufacture nine carbon fibre reinforced epoxy laminates that were tested in bending to study the influence of asymmetric wrinkles on strength. Due to the accuracy of the process and material flow of the material during consolidation, the achieved wrinkles did not match the intended wrinkles in terms of maximum fibre angles or degree of asymmetry, highlighting the difficulty of creating controlled wrinkles in flat coupon specimens. Nevertheless, the experimental data showed decreasing ultimate bending strength with increasing maximum angle and increasing strength with increasing asymmetry. Therefore, for samples with the same maximum angle, the sample with higher wrinkle asymmetry had a higher ultimate bending failure strength, highlighting the importance of considering wrinkle asymmetry alongside the often-used maximum angle. Simulations of the as-designed coupons were also run to design the experiment. In terms of the relevance of asymmetry, both the numerical and experimental data are in line with previous numerical studies on asymmetric wrinkles under pure tension and compression. Contrasting the as-designed wrinkle morphologies to the manufactured wrinkles, it was found that overall, the study highlights the complexity and difficulty of creating controlled wrinkles within coupon specimens and provides evidence for the relevance of wrinkle shape asymmetry when characterising and simulating wrinkles across multiple load cases.
Carbon fibre-reinforced thermoplastics are attractive for lightweight applications due to their high strength and corrosion resistance. Among engineering polymers, polyamide 12 (PA12) is widely used due to its low moisture absorption; however, its relatively high cost and limited availability are drawbacks. Compatibilised blends based on high-density polyethylene (HDPE) and polyamide 6 (PA6) emerge as an alternative. This study comparatively evaluates PA12- and HDPE/PA6(50/50)-based formulations, reinforced and unreinforced with 10 wt.% carbon fibres, focusing on their mechanical, thermal, morphological, and rheological behaviour. The HDPE/PA6/carbon composite showed higher tensile strength (47.3 MPa) and modulus (2010 MPa), whereas PA12 composites exhibited greater ductility (elongation >190%). Carbon fibre incorporation increased stiffness and reduced melt flow in both systems. Thermal analyses indicated distinct crystallisation behaviours, with PA12 showing a more uniform crystalline structure, while HDPE/PA6 blends exhibited multiphase crystallisation due to their immiscible morphology. Overall, compatibilised HDPE/PA6 blends achieved mechanical performance comparable to or exceeding PA12, albeit with reduced ductility.
This study investigates the influence of sodium hydroxide (NaOH) surface treatment on the out-of-plane auxetic behavior and mechanical properties of hemp/polylactic acid (PLA) nonwoven composites. Untreated and alkali-treated hemp fibers (2.5 wt.%, 5 wt.%, and 7.5 wt.% NaOH) were used to fabricate needle-punched nonwovens with 50 wt.% PLA. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) were employed to analyze surface morphology, thermal stability, and chemical changes, respectively. Alkali treatment effectively removed hemicellulose and lignin, enhanced surface roughness, and improved fiber matrix adhesion. Mechanical testing revealed that 5 wt.% NaOH treatment yielded the highest tensile strength due to optimal interfacial bonding and mechanical interlocking. However, out-of-plane Poisson's ratio measurements indicated a decrease in auxetic magnitude with increasing NaOH concentration, with the maximum negative Poisson's ratio of approximately -6.5 observed for untreated composites and -2.3 for treated ones. The results demonstrate that improved interfacial bonding enhances strength but restricts fiber rotation and reorientation, leading to reduced auxetic behavior. This work establishes a direct correlation between fiber surface modification and auxetic tunability, providing valuable insight into designing sustainable, functionally adaptive composites for structural and protective applications.
Fused filament fabrication (FFF) is a printing technology that relies on remelting and modelling physical objects from thermoplastic filament materials. Natural fibres have been studied and used for polymeric reinforcement. Yet, there is limited information in the literature about reinforcing filament materials for FFF printing. This study aimed to evaluate some surface properties of FFF 3D printed polyamide 6 reinforced with kenaf fibres. Kenaf fibres were retted, bleached with sodium hypochlorite solution, and silanised with 3-aminopropyltriethoxysilane solution prior to thermally compounding with polyamide beads to produce filaments for experimental groups. A total of 55 specimens were printed by an FFF printer for 5 groups: control, 0.1%, 0.3%, 0.5% and 1% kenaf fibres-reinforced polyamide (11 specimens for each group). Fourier-transform infrared spectroscopy analysis was conducted on the control and 1% kenaf-reinforced sample for chemical characterisation. The study groups were submitted to surface roughness, surface hardness and water contact angle measurement tests. The results showed no significant chemical change in the composite as a result of fibre incorporation. Surface hardness have shown a significant increase in their mean values after fibres incorporation, which were 93.3, 93.5, 92.2, 91.3 for 0.1, 0.3, 0.5 and 1% respectively compared with the control 88.9, while there was no significant difference in both surface roughness and surface hydrophilicity except for 1% kenaf-reinforced group (roughness = 358, contact angle = 55.1) compared to the control group (roughness = 216, contact angle = 46.4). Kenaf fibres reinforcement with polyamide 6 at concentrations not more than 0.5% has improved the surface hardness of the FFF printed material.
Fused Deposition Modeling (FDM) has promised to revolutionize the fabrication of strain sensors, offering design flexibility and cost-effectiveness. However, printing flexible thermoplastic elastomers with conductive nanomaterials presents challenges, such as nozzle blockages and inconsistent feeding due to high melt viscosity and filler agglomeration. In this study, hybrid thermoplastic polyurethane (TPU) nanocomposites filaments containing carbon nanotubes (CNT), graphene nanoplatelets (GNP), and boron nitride (BN), were developed. The hybrid fillers reduced the filament extrusion force and improved the printability compared to CNT-only composites, while maintaining high electrical conductivity and strain-sensing capabilities. A novel extrusion force testing method was implemented to measure the printability of the nanocomposite filaments. The printed sensors, prepared via FDM, demonstrated an enhanced strain-sensing range and mechanical durability, with TPU-CNT-BN composites achieving sensing up to 250% strain. These findings highlight the potential of hybrid nanocomposites for reliable and scalable production of flexible strain sensors using FDM, offering applications in wearable electronics and structural health monitoring.
In this work, hardness, wear resistance, modelling of dynamic mechanical properties and activation energy of thermal degradation of poly aryl ether ketone reinforced with tungsten carbide combined with carboxyl-functionalised multi-walled carbon nanotubes are reported. Melt mixing technique followed by injection molding was carried out for the production of poly aryl ether ketone/tungsten carbide/carboxyl-functionalised multi-walled carbon nanotube individual and hybrid nanocomposites. The hardness of the nanocomposites was measured using shore D hardness equipment and it was found out that poly aryl ether ketone reinforced with 0.75 wt.% tungsten carbide and 0.75 wt.% carboxyl-functionalised multi-walled carbon nanotubes (1.5WF) showcased the highest hardness value and an increment of 7.05% compared to base matrix. The hybrid nanocomposite 1.5WF was observed to be minimum specific wear rate at 10 N and 20 N. The storage modulus and damping behaviour of the individual and hybrid nanocomposites were modelled using classical equations. The integrated procedural decomposition temperature and activation energy were calculated, showing that 1.5WF nanocomposites exhibited a 45.63% higher activation energy compared to the base poly aryl ether ketone matrix using the Coats-Redfern method. The results revealed that the carboxyl-functionalised multi-walled carbon nanotube and tungsten carbide nanoparticles significantly influenced the Shore D hardness and sliding wear behaviour of the individual and hybrid nanocomposites.
This research evaluates the tribological performance of polytetrafluoroethylene (PTFE) filled with graphene nanoplatelets (GNPs) against steel under aqueous conditions to correlate the impact of the GNP percentage in PTFE, the test environment and load. Trials were carried out on a pin-on-disc reciprocating tribometer following Taguchi's L32 design. Analysis of variance revealed that GNP percentage and environment are the dominant factors affecting the average coefficient of friction (COF) and specific wear rate (SWR), respectively. The technique for order of preference by similarity to ideal solution (TOPSIS) was utilised to optimise the response variables (COF and SWR). Field emission scanning electron microscope and energy-dispersive X-ray spectroscopy were used to assess the worn surfaces. The outcomes established that the seawater environment remarkably decreased COF and SWR, and 5 wt. % GNP/PTFE performs best. TOPSIS demonstrates that a 5 N load, GNP percentage 5%, and seawater yield optimum performance.
This study provides a comprehensive assessment of the effects of carbonyl iron powder incorporation on ethylene-propylene-diene monomer composites cured via sulphur, peroxide and peroxide-co-agent systems following thermo-oxidative aging. After exposure to 155 degrees C for 72 h, sulphur-cured formulations containing carbonyl iron powder exhibited an approximately 70% increase in crosslink density relative to their non-aged counterparts, accompanied by pronounced decreases in elongation at break (approximate to 88%) and tear strength (approximate to 69%). In contrast, peroxide-cured systems demonstrated substantially higher resistance to thermo-oxidative degradation, a behaviour attributed to the superior stability of carbon-carbon crosslinks generated during peroxide vulcanisation. Notably, the composite cured with peroxide and a Type II co-agent displayed minimal formation of additional crosslinks (<14%), maintained tear resistance and showed only a moderate reduction in elongation (approximate to 35%). Magnetic and thermal analyses confirmed that the incorporation of carbonyl iron powder did not significantly affect properties such as magnetisation or thermal stability of the elastomeric matrix. Among all systems evaluated, the formulation cured with peroxide and the Type II co-agent (Formulation 6) exhibited the highest thermo-oxidative stability, indicating its suitability for applications requiring moderate magnetic responsiveness combined with enhanced long-term durability.
High-impact polystyrene (HIPS) is widely used in household appliances, electronic equipment casings, packaging materials, and automotive parts due to its excellent dimensional stability, fluidity, electrical insulation, and rigidity. However, its high flammability and significant smoke emission during combustion limit its application in fire-sensitive environments. In this study, a synergistic intumescent flame retardant system composed of hollow cubic zinc hydroxystannate (H-ZHS), piperazine pyrophosphate (PAPP), and melamine polyphosphate (MPP) was developed to improve the fire safety of HIPS composites. Thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 vertical combustion, and cone calorimetry (CCT) were employed to evaluate the thermal stability, flame retardancy, and smoke suppression properties. The optimised composite (30 wt% total flame retardant loading with a PAPP/MPP mass ratio of 7:3 and 2 wt% H-ZHS) achieved a UL94-V0 rating (1.6 mm thickness) and an LOI of 34.3%. Compared to pure HIPS, the peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) decreased by 74.1 +/- 3.2%, 20.6 +/- 1.8%, and 65.3%, respectively. The synergistic mechanism involved condensed-phase char formation catalysed by H-ZHS and gas-phase flame inhibition by non-flammable gases (e.g. NH3) from PAPP/MPP decomposition. This work provides a practical strategy for developing halogen-free flame-retardant HIPS composites with balanced fire safety and mechanical properties.
In this study, the effects of resin type and liquid butadiene rubber (LBR) on the rheological, network structure, mechanical, dynamic mechanical, and damping properties of poly(epichlorohydrin) (CO) and poly (epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) (GECO) elastomers were investigated. To study the impact of resin type, C8/C9 and C9/C10 aromatic hydrocarbon resins, phenolic resin, and LBR were used as liquid rubber. Rheological studies have shown that adding resin and LBR in the preparation of both CO and GECO-based elastomers reduces the degree of curing and, as a result, the cross-link density due to the plasticising effect of these agents. While the change in cross-link density reduced the tensile strength, it increased the elongation value at break. A sharp decline in the mechanical properties of systems using LBR has been observed. When using resin, the most significant change observed was in the damping properties of elastomers. The use of resin enhanced the energy dissipation properties. In both CO- and GECO-based elastomers, phenolic resin was identified as the most effective for extending the effective damping range. CO-DP5245 demonstrates effective damping (tan delta > 0.3) at particularly high temperatures (ranging from -2.0 degrees C to +70 degrees C), while GECO-T3108 shows effective damping at low temperatures (ranging from -36.1 degrees C to +10.5 degrees C). Among all the prepared elastomers, the highest tan delta (tan delta) value was obtained in the CO-PhenRes elastomer, which was formulated using CO-DP5245 and phenolic resin. This makes it suitable for high-temperature applications. Cyclic compression and dynamic mechanical analyses show that the GECO-based elastomer, prepared using C8/C9 hydrocarbon resin, is the most effective elastomer for low-temperature damping applications. These studies demonstrate that all physico-mechanical and dynamic mechanical properties can be modified in a controlled manner by altering the network structure using resin and LBR in both CO and GECO-based elastomers.
A naturally occurring two-dimensional (2D) nano-SiO2 derived from phytolith minerals was employed as a reinforcing filler for polymethyl methacrylate (PMMA) composites. Unlike conventional 2D materials, this SiO2 does not require exfoliation, significantly reducing processing complexity and cost. The nanosheets were modified using 3-aminopropyltriethoxysilane (KH-550) and incorporated into PMMA via melt blending. FTIR analysis indicated that the 2D nano-SiO2 was successfully modified by KH-550 and effectively grafted onto the PMMA chains, while SEM analysis revealed a distinct layered structure and strong interfacial adhesion, contributing to a porous morphology. Mechanical tests demonstrated that at an optimal loading of 1.06 wt.%, the composite achieved a tensile strength of 72.74 MPa and an impact toughness of 70.23 kJ/m(2), representing increases of approximately 93.8% and 100.6% compared to pure PMMA. DSC analysis showed a slight increase in the glass transition temperature, indicating modest enhancement in thermal stability. These findings suggest that natural 2D nano-SiO2 serves as a low-cost filler with a remarkable reinforcing effect on the mechanical performance of PMMA-based composites, exhibiting great potential for engineering applications.
Carbon fibre-reinforced epoxy resin composites (CF/EP) have been widely used in the shipping, aerospace and construction industries due to their excellent corrosion resistance and mechanical properties. However, thermosetting resins form insolubility and non-melting three-dimensional cross-linked networks after curing, making these materials difficult to be recycled. In our research described in this paper, we propose a solvothermal degradation method for recycling carbon fibres from CF/EP. We utilised acetic acid and hydrogen peroxide as solvents and controlled the reaction conditions at 100 degrees C-130 degrees C for 90 min-180 min to degrade CF/EP in a Teflon-lined autoclave. The experimental results indicated that the degradation degree of resin gradually increased with the reaction temperature and reaction time, reaching up to 99.8% at 100 degrees C for 180 min. Based on scanning electron microscopy, X-ray diffraction, Raman spectra analyses and X-ray photoelectron spectroscopy, we observed that the surface of the recycled carbon fibres had almost no resin residue and their microstructure was not significantly changed. The monofilament tensile strength of the recycled carbon fibres was 3.48 GPa. The strength retention rate of the RCF-100 degrees C-180 min was as high as 99.15% relative to the virgin carbon fibres, further confirming that the solvothermal degradation process hardly damaged the mechanical properties of the recycled carbon fibres. In addition, a possible degradation mechanism of CF/EP was proposed based on Fourier transform infrared spectroscopy analysis. The epoxy resin was efficiently degraded under the dissolution/swelling effect and chemical degradation reactions.
In response to the frequent fatigue failure of seals in hydraulic support safety valves under high-pressure, high-flow conditions with water-based media, this study aims to improve the service life of the seal by optimizing its structure. Using ABAQUS and a combined seal fatigue life prediction model, the influence of key structural parameters on fatigue life was investigated. Orthogonal experiments and range analysis were conducted, revealing the order of influence as follows: groove chamfer, relief hole diameter, O-ring compression ratio, and sealing clearance. After optimization, the fatigue life of the seal increased by 2.01 times. The proposed analysis method and model provide a useful reference for the reliability-based design of safety valves in hydraulic supports under high-pressure environments.
In this study, graphene nanoplatelets were integrated into a fluoroelastomer matrix to improve the performance of polymer nanocomposites specifically for O-ring production. The enhanced materials were subjected to field testing against sour condensate, demonstrating their potential for superior durability and resistance in challenging environments. This study evaluated the effects of graphene nanoplatelet on the mechanical properties and thermal stability of the graphene nanoplatelet/fluoroelastomer nanocomposite compared to the standard fluoroelastomer. Key properties such as tensile strength, hardness, and tear strength were assessed before and after aging tests, supported by transmission electron microscopy and field emission scanning electron microscopy analyses. The O-rings were tested in the mechanical seals of centrifugal pumps with sour condensate applications. The results demonstrated that the addition of graphene significantly improved moduli, tensile strength, hardness, and tear strength, while reducing elongation at break. The moduli of the nanocomposite at 10%, 50%, and 100% strain increased by 103.90%, 156.40%, and 130.30%, respectively, compared to those of the fluoroelastomer. Additionally, the nanocomposite exhibited improvements in tensile strength, hardness, and tear strength by 9.94%, 11.80%, and 50.80%, respectively, relative to fluoroelastomer. However, the elongation at break of the nanocomposite decreased by 58.22% compared to that of the fluoroelastomer. Post-thermal aging tests revealed enhanced thermal stability in the nanocomposite. Field tests confirmed the nanocomposite O-rings' effectiveness against sour condensate, successfully preventing issues like explosive decompression, with no signs of degradation. Overall, the nanocomposite O-rings exhibited a longer lifespan compared to traditional and very expensive perfluoroelastomer O-rings.
Reliable prediction of ultimate load in composite/titanium bolted joints is hindered by intricate, interacting damage modes under multi-axial stress. To overcome the limitations of current high-fidelity yet computationally expensive models, we present a hybrid data-physics framework that couples an enhanced shear-driven three-dimensional LaRC05 failure criterion with a streamlined backpropagation (BP) neural network. This synergistic coupling represents a paradigm shift, enabling a leap from high-cost, high-fidelity simulation to high-fidelity, low-cost prediction. The progressive damage process is embedded in ABAQUS through a user-defined material subroutine, accurately capturing damage initiation and evolution without resorting to excessive mesh refinement. Bayesian optimisation and Shapley Additive Explanations (SHAP)-based feature selection yield a compact network architecture that retains only the most influential inputs, ensuring robust generalisation across a broad design space. Validation against experimental data demonstrates markedly improved accuracy and computational efficiency, enabling rapid evaluation during early-stage design. The resulting tool is readily deployable, offering practitioners a swift and dependable route for the safety assessment of lightweight hybrid structures.
Polytetrafluoroethylene (PTFE) exhibits outstanding properties that make it a preferred engineering material, but its practical applications in demanding environments are limited by inherent deficiencies in hardness, creep resistance, and wear performance. This study investigates composite modification strategies through experimental and molecular dynamics simulation approaches, focusing on polyimide (PI) reinforcement in a PTFE matrix containing 5 wt% copper powder and 3 wt% molybdenum disulphide. Under standardised testing conditions (100 N load, 100 rpm rotation speed, and 60 min duration), the composite hardness demonstrated progressive enhancement with increasing PI content. Optimal tribological performance, characterised by minimised friction coefficient and volumetric wear, was achieved at 15 wt% PI incorporation. Comparative analysis revealed consistent trends between experimental measurements and simulation predictions. Through detailed examination of interfacial temperature distribution, atomic concentration profiles along the thickness direction, and radial distribution functions, the reinforcement mechanism was elucidated at the atomic scale, providing fundamental insights into the structure-property relationships of the composite system.
