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  • 1.
    Nikonovich, Maksim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Costa, Joana F.S.
    CEMMPRE, Department of Chemical Engineering, University of Coimbra, Coimbra, Portugal.
    Fonseca, Ana C.
    CEMMPRE, Department of Chemical Engineering, University of Coimbra, Coimbra, Portugal.
    Ramalho, Amilcar
    CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Structural, thermal, and mechanical characterisation of PEEK-based composites in cryogenic temperature2023In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 125, article id 108139Article in journal (Refereed)
    Abstract [en]

    Thermal, thermo-mechanical and mechanical properties of four different commercially available polyetheretherketones (PEEK) based materials were investigated. PEEK matrix was either modified and/or reinforced with carbon fibres, graphite and/or PTFE. Impact strength was measured at three different temperatures: 25 °C, −100 °C, and −195 °C. At 25 °C, thermal stability and mechanical properties, including the elastic modulus, compression, and impact strength, were enhanced with the addition of carbon fibres. Matrix modification had a minor impact on thermal stability, while the mechanical properties decreased, except for impact strength. At −100 °C, the mechanical properties of the neat polymers were improved, including increased impact strength by 20% compared to values at 25 °C. Addition of fillers hindered the rise of impact strength due to complex mechanisms caused by different coefficients of thermal expansion of reinforcements and matrix. At −195 °C, the significant increase of impact strength was revealed for unmodified PEEK reaching 30 times higher values than at 25 °C, while matrix modification suppressed the rise of impact strength. The scratch test indicated the superior behaviour of unfilled PEEK during the tested load range (up to 15 N), while the effect of the fillers was observed at much lower load threshold of 7 N.

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  • 2.
    Nikonovich, Maksim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Ramalho, Amilcar
    CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Cryogenic cyclic aging effect on thermal, mechanical and tribological performance of PEEK-based materialsManuscript (preprint) (Other academic)
  • 3.
    Nikonovich, Maksim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Ramalho, Amilcar
    CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Effect of cryogenic aging and test-environment on the tribological and mechanical properties of PEEK composites2024In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 194, article id 109554Article in journal (Refereed)
    Abstract [en]

    This study investigated mechanical and tribological properties of polyetheretherketone (PEEK) and PEEK composites, before and after aging in liquid nitrogen for 5 months. Tribological tests conducted at 25 °C and at − 100 °C in air and in high vacuum (10−5 Pa) environment revealed the effect of matrix modification, fillers, environment, temperature, and cryogenic aging on their performances. Cryogenic aging of the polymers resulted in cryogenic embrittlement and decrease of the fracture toughness by around 10% and increase of wear rate by at least 20%. Very low coefficient of friction (0.02) was achieved in cryogenic vacuum environment for carbon fiber, graphite, and PTFE reinforced PEEK. The results indicate the significant impact of aging, temperature and environment on PEEK and its composites.

    Download full text (pdf)
    fulltext
  • 4.
    Nikonovich, Maksim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Ramalho, Amilcar
    CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Impact of test-environment and cryogenic aging on mechanical properties and tribological performance of PI-based materialsManuscript (preprint) (Other academic)
    Abstract [en]

    This study investigates the effect of test-environment, temperature, and cryogenic aging in liquid nitrogen for 5 months on mechanical and tribological performance of polyimide (PI) and PI composites. Tribological tests were conducted at 25 °C in air, and at both 25 °C and -100 °C in a high vacuum (10-5 Pa) environment. Impact of cryogenic aging, testing condition on PI-based materials varied depending on the polymer structure and composition. Cryogenic aging led to embrittlement, increasing the coefficient of friction and wear rate up to 77% and 165%, respectively. Some polyimides exhibited the lowest coefficient of friction (0.04) in vacuum at 25°C, while the temperature reduction to -100 oC in vacuum generally decreased the tribological performance, increased contact stresses and abrasive wear of the materials. 

  • 5.
    Nikonovich, Maksim
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements. CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Ramalho, Amilcar
    CEMMPRE, Department of Mechanical Engineering, University of Coimbra, Portugal.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Influence of cryogenic cyclic aging on thermal, mechanical and tribological performance of PI-based materialsManuscript (preprint) (Other academic)
1 - 5 of 5
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