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  • 1.
    Asp, Leif
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Szpieg, Magdalena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Wysocki, Maciej
    Swerea SICOMP AB.
    Mechanical performance and modelling of a fully recycled modified CF/PP composite2012Ingår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, nr 12, s. 1503-1517Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fully recycled carbon fiber reinforced maleic anhydride grafted polypropylene (MAPP)-modified polypropylene (rCF/rPP) composite material has been developed and characterized. This new composite was manufactured employing papermaking principles, dispersing the recycled carbon fibers (rCF) in water, and forming them into mats. Two layers of the recycled polypropylene (rPP) films manufactured using press-forming were sandwiched between three rCF preform layers in a stack. The stack was heated and press-formed resulting in a composite plate with a nominal thickness of 1.20 mm and a fiber volume fraction of 40%. A series of tensile tests using rectangular specimens cut in four different directions (0°, 90°, ± 45°) in the composite plate were performed to confirm in-plane material isotropy. Models to predict stiffness and strength of the short fiber rCF/rPP composite were also employed and validated using experiments. The models were found to be in good agreement with experimental results. Fiber length distribution measurements were performed before (unprocessed) and after (processed) composite manufacturing to investigate the influence of processing on fiber degradation. The results revealed a significant reduction in fiber length by the press-forming operation. To model the viscoelastic and viscoplastic responses of the composite an inelastic material model was employed and characterized using a series of creep and recovery tests. From the creep tests, it was found that the time and stress dependence of viscoplastic strains follows a power law. The viscoelastic response of the composite was found to be linear in the investigated stress range. The material model was validated in constant stress rate tensile tests and the agreement was good, even close to the rupture stress.

  • 2.
    Giannadakis, Konstantinos
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Szpieg, Magdalena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Mechanical performance of a recycled carbon fibre/PP composite2011Ingår i: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 51, nr 5, s. 767-777Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A composite made of recycled carbon fibres in recycled polypropylene matrix is studied experimentally to describe the features of the elastic and time dependent nonlinear mechanical behaviour. The properties of the developed material have a large variability to be addressed and understood. It was found that the stress-strain curves in tension are rather nonlinear at low strain rate and the strength is sensitive to strain rate. The elastic properties' reduction for this composite after loading to high strains is rather limited. More important is that even in the "elastic region" due to viscoelastic effects the slope of loading-unloading curve is not the same and that at higher stress large viscoplastic strains develop and creep rupture is typical. The time and stress dependence of viscoplastic strains was analysed and described theoretically. The viscoelastic response of the composite was analysed using creep compliance, which was found to be slightly nonlinear

  • 3.
    Szpieg, Magdalena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    A novel composite material from recycled constituents2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The increasing industrial use of carbon fibre in e.g. aircraft and wind turbines calls for strategies for their recovery and possible reuse. In additional, tremendous amount of energy is needed to be able to manufacture pristine carbon fibres. The work that has been done was to manufacture engineering composite material made from recyclates. Processing scrap from PURE® was extensively studied in terms of its stability and process ability as a thermoplastic matrix material. In a second study polypropylene scrap material was reprocessed into a film by press forming and introduced into a stack of carbon fibre preforms made from recycled carbon fibres recovered via a pyrolysis process from aircraft structures. The preform stack was heated and the composite material was manufactured by press forming.A challenging issue in this work was to achieve the desired distribution of the recovered carbon fibres in the fibre preforms. It is well known that dispersion of reinforcement is of immense importance for quality and performance of the composite materials. Here, a paper making method is employed to distribute the recovered carbon fibres randomly in the plane. The quality of the manufactured novel, fully recycled, composite material regarding void content and consolidation was controlled by extensive microscopy. The resulting composite material was analysed in terms of its mechanical performance including elastic modulus, Poisson's ratio, strength and strain to failure as well as its creep resistance.

  • 4.
    Szpieg, Magdalena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Development and characteristics of a fully recycled CF/PP composite2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The increasing industrial use of carbon fibre in e.g. aircraft and wind turbines calls for strategies for their recovery and possible reuse. In addition, tremendous amount of energy is needed to be able to manufacture pristine carbon fibres. In this work, an engineering composite material was manufactured from recyclates. Processing scrap from PURE was extensively studied in terms of its stability and processability as a thermoplastic matrix material. Polypropylene scrap material was reprocessed into a film by press forming and introduced into a stack of carbon fibre preforms made from recycled carbon fibres recovered via a pyrolysis process from aircraft structures. The preform stack was heated and the composite material was manufactured by press forming. A challenging issue in this work was to achieve the desired distribution of the recovered carbon fibres in the fibre preforms. Here, a paper making method was employed to distribute the recovered carbon fibres randomly in the plane. It is well known that the fibre/PP interface properties are often the weakest link in the composite performance. Several modifications, including the addition of maleic anhydride grafted polypropylene (MAPP), are often used. MAPP improves the interface bonding between the fibre and polymer matrix by two simultaneous reactions. Firstly, the long molecular chain is responsible for chain entanglements and co-crystallisation with the non-polar PP matrix. These entanglements provide mechanical integrity to the host material. Secondly, the anhydride groups chemically interact with the functional groups on the fibre surface. The addition of MAPP has been found to improve the interface and increase the stiffness and strength of the composite. Inelastic mechanical behaviour in tension of a recycled polypropylene (rPP) matrix and a rPP matrix with addition of 10% of maleic anhydride grafted polypropylene (rPP+MAPP) was characterised and compared. The time dependent response was decomposed into nonlinear viscoelastic and viscoplastic parts and each of them quantified. It was found that the elastic properties of the rPP matrix did not degrade during loading. The addition of MAPP to the rPP matrix did not change the mechanical properties of the material. A non-linear material model was developed and the involved parameters (stress dependent functions) were identified. The model was then validated in a stress controlled test at a constant stress rate. The inelastic and time dependent behaviour of the MAPP modified composite material in tension was analysed. A series of quasistatic tensile and creep tests were performed to identify the material model, which accounts for: a) damage related stiffness reduction, b) development of stress and time dependent irreversible strains described as viscoplasticity, c) nonlinear viscoelastic behaviour. Fibre length distribution was investigated before and after composite manufacturing process to investigate the influence of the processing conditions on the fibre degradation. The quality of the manufactured novel, fully recycled, composite material regarding void content and fibre orientation was examined by microscopy.

  • 5.
    Szpieg, Magdalena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Giannadakis, Konstantinos
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Viscoelastic and viscoplastic behavior of a fully recycled carbon fibre-reinforced maleic anhydride grafted polypropylene modified polypropylene composite2012Ingår i: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 46, nr 13, s. 1633-1646Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of maleic anhydride grafted polypropylene (MAPP) coupling agents on properties of a new composite made of recycled carbon fibers and recycled polypropylene (rCF/[rPP + MAPP]) was studied experimentally. This new material presented significantly improved properties, compared to the previous generation, without the addition of MAPP (Giannadakis K, Szpieg M and Varna J. Mechanical performance of recycled carbon fibre/PP. Exp Mech 2010; published online.). This was mostly attributed to improvement of the fiber/matrix interface. The inelastic and time-dependent behavior of the MAPP modified composite material in tension was analyzed. A series of quasi-static tensile and creep tests were performed to identify the material model, which accounts for: (a) damage-related stiffness reduction, (b)development of stress and time-dependent irreversible strains described as viscoplasticity, (c) nonlinear viscoelastic behavior. The damage-related stiffness reduction was found to be less than 10%. Although damage-dependent stiffness was not the main source of nonlinearity, it was included in the inelastic material model. In creep tests, it was found that the time and stress dependence of viscoplastic strains follows a power law, which makes the determination of the parameters in the viscoplasticity model relatively simple. The viscoelastic response of the composite was found to be linear in the investigated stress domain. The material model was validated in constant stress rate tensile tests.

  • 6.
    Szpieg, Magdalena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Giannadakis, Konstantinos
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Varna, Janis
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Time-dependent nonlinear behavior of recycled polypropylene in high tensile stress loading2011Ingår i: Journal of Thermoplastic Composite Materials, ISSN 0892-7057, E-ISSN 1530-7980, Vol. 24, nr 5, s. 625-652Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inelastic mechanical behavior in tension of a recycled polypropylene (rPP and a rPP with addition of 10% of maleic anhydride grafted polypropylene (rPP + MAPP) was characterized and compared. The time-dependent response was decomposed into nonlinear viscoelastic and viscoplastic parts and each of them quantified. It was found that the elastic properties did not degrade during loading. The addition of MAPP did not change the mechanical properties of the rPP. A nonlinear material model was developed and the involved parameters (stress-dependent functions) were identified. The model was then validated in a stress controlled test at a constant stress rate.

  • 7.
    Szpieg, Magdalena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Wysocki, M.
    SICOMP AB, Swedish Institute of Composites.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Novel composites from recycled constituents2009Ingår i: 24th annual technical conference of the American Society for Composites 2009 and 1st Joint Canadian-American Technical Conference on Composites: Newark, Delaware, USA, 15 - 17 September 2009 / [ed] John W. Gillespie, Red Hook, NY: Curran Associates, Inc., 2009, Vol. 4, s. 2651-2661Konferensbidrag (Refereegranskat)
    Abstract [en]

    Only a small fraction of the waste generated by use and manufacturing of carbon-based composites is currently reused. However, due to European Union (EU) regulations and limited amount of landfilling, the industry is forced to consider recycling solutions already during the manufacturing process. The following work is devoted to the development of a technique for manufacture of novel engineering materials from recycled carbon fibres and thermoplastic matrix. Fibre preforms are manufactured employing a papermaking technique for dispersing the carbon fibres. The polypropylene (PP) matrix was reprocessed into a film. The carbon fibre preforms and PP films were stacked and composite materials were subsequently manufactured by press forming and evaluated.

  • 8. Szpieg, Magdalena
    et al.
    Wysocki, Maciej
    Swerea SICOMP AB, Mölndal.
    Asp, Leif
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Recycled polypropylene aimed as composites precursor material2009Ingår i: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, nr 9-10, s. 412-418Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of this research is to assess the stability and processability of recycled PP materials for their suitability for use as matrix material in polymer composite. The work comprises development and characterisation of matrix precursors from recycled polypropylene. The reused PP considered comes from two sources: PP from the self reinforced PP PURE® processing scrap and an automotive grade developed to offer an even material quality. To assess the thermal stability of two PP qualities for subsequent composite manufacturing, oxidation induction time (OIT), melting point (Tm), decomposition temperature (Td) and viscosity (μ) were investigated. The results indicate, that PURE® processing scrap is very well stabilised and therefore suitable for multiple processing, whereas the automotive grade recycled PP cannot be used for this purpose. Fibres, for subsequent composite preforming were spun by melt spinning from the PURE® scrap processing and its mechanical properties were characterised.

  • 9.
    Szpieg, Magdalena
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Wysocki, Maciej
    Swerea SICOMP AB, Mölndal.
    Asp, Leif
    Reuse of polymer materials and carbon fibres in novel engineering composite materials2009Ingår i: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 38, nr 9-10, s. 419-425Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work was devoted to the development of a technique for manufacture of a novel engineering material from carbon fibres and thermoplastic matrix recyclates. Fibre preforms were manufactured employing a papermaking technique for dispersing the carbon fibres. The polypropylene (PP) matrix recyclate was reprocessed into a film. The carbon fibre preforms and PP films were stacked and composite materials were subsequently manufactured by press forming. The mechanical behaviour of carbon fibre preforms was characterised by a compaction test and compared to the results obtained by consolidation test of the carbon fibres reinforced PP composites. The consolidation experiments were found to follow the trend from compaction tests allowing prediction of the amount of polymer material needed, fibre volume fraction as well as composites thickness. The resulting dispersion of fibres and void content were evaluated by microscopy.

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  • asciidoc
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