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  • 1.
    Dhakal, Nayan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, LS2 9JT Leeds, United Kingdom.
    Espejo, Cayetano
    Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, LS2 9JT Leeds, United Kingdom.
    Morina, Ardian
    Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, LS2 9JT Leeds, United Kingdom.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological performance of 3D printed neat and carbon fiber reinforced PEEK composites2024In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 193, article id 109356Article in journal (Refereed)
    Abstract [en]

    This work investigates the tribological behavior of neat and carbon fiber-reinforced polyether-ether-ketone (PEEK) materials processed using the fused filament fabrication (FFF) technique. The reciprocating sliding behavior of printed polymers against stainless steel (SS) under dry and water-lubricated conditions was studied. The running-in behavior and evolution of friction were dependent on the material combination and sliding conditions. PEEK reinforced with 10 wt% carbon fibers was optimal considering tribological performance. Neat PEEK exhibited a combination of abrasive and adhesive wear mechanisms, while composites primarily showed fiber-matrix debonding and delamination during sliding. The outcome of this work has significance in improving the processing design of PEEK-based materials in extrusion-based 3D printing for tribological applications.

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  • 2.
    Dhakal, Nayan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Shi, Yijun
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Tribological behaviour of UHMWPE composites lubricated by polyvinylpyrrolidone‐modified water2022In: Lubrication Science, ISSN 0954-0075, E-ISSN 1557-6833, Vol. 34, no 1, p. 42-53Article in journal (Refereed)
    Abstract [en]

    Tribological characteristics of ultra-high molecular weight polyethylene (UHMWPE) composites with 10% short carbon fibres (SCF) lubricated in water with polyvinylpyrrolidone (PVP) as a modifier were investigated. The aqueous solutions with varying concentrations of PVP were prepared, and their viscosity-enhancing action, friction-reducing properties and anti-wear performances were studied under different loading conditions equivalent to 10 and 20 MPa of contact pressures at a constant sliding speed of 20 mm/s. The results showed that PVP is an excellent viscosity modifier for water. PVP-modified water exhibited excellent performance compared to distilled water, reducing the wear and friction coefficient of neat UHMWPE up to 25%. The anti-wear properties of UHMWPE-SCF composite were also improved with PVP modified water lubrication, yielding a maximum reduction of wear up to 45%. PVP seems to be a promising additive of modifying the lubricating properties of distilled water for water-based lubrication. 

  • 3.
    Dhakal, Nayan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, LS2 9JT, Leeds, United Kingdom.
    Wang, Xiaolong
    State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, CAS, Lanzhou, 730000, China.
    Espejo, Cayetano
    Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, LS2 9JT, Leeds, United Kingdom.
    Morina, Ardian
    Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, LS2 9JT, Leeds, United Kingdom.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Impact of processing defects on microstructure, surface quality, and tribological performance in 3D printed polymers2023In: Journal of Materials Research and Technology, ISSN 2238-7854, Vol. 23, p. 1252-1272Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing (AM), also known as three-dimensional (3D) printing, of polymer-based materials is growing as a time-efficient, economical, and environmentally sustainable technique for prototype development in load-bearing applications. This work investigates the defects arising from the processing in material extrusion-based AM of polymers and their impact on the part performance. The influence of raster angle orientation and printing speed on tribological characteristics, microstructure, and surface finish of acrylonitrile butadiene styrene (ABS) fabricated in a heated build chamber was studied. Comprehensive analysis with fractography and tomography revealed the formation, distribution, and locations of internal voids, while surface defects were studied with the topography analysis of as-printed surfaces. Surface roughness and tribological results show that printing speed can be optimally increased with a minimal impact on interlayer bonding and part performance. Increased printing speed allowed up to 58% effective reduction in printing time obtaining comparable mechanical properties at varying process parameters. 3D printed ABS exhibited dry sliding friction coefficients in the range of 0.18–0.23, whilst the maximum specific wear rate was 6.2 × 10−5 mm3/Nm. Higher surface roughness and increased printing speed exhibited delayed running-in during dry sliding, while insignificant influence was observed for steady-state friction and wear behaviors. The findings indicate that improved surface finish and reduced internal defects can be achieved with a controlled build environment allowing for higher printing speed. The observations in this study are evidence that 3D printing can be adapted for the sustainable manufacturing of polymeric components for tribological applications.

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