Change search
Refine search result
1 - 5 of 5
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Baillif, Marie Le
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    The effect of processing on fiber dispersion, fiber length and thermal degradation of bleached sulfite cellulose fiber polypropylene composites2009In: Journal of Thermoplastic Composite Materials, ISSN 0892-7057, E-ISSN 1530-7980, Vol. 22, no 2, p. 115-133Article in journal (Refereed)
    Abstract [en]

    The goal of this study was to examine how the extrusion process affects the dispersion, length and thermal degradation of cellulose fibers (CF) in polypropylene (PP) composites. Bleached sulfite cellulose fibers were pelletized and then compounded (20 and 30 wt%) in a co-rotating twin screw extruder. The pelletizing process of cellulose fibers was found to cause extensive fiber breakage. The fiber length was decreased from an initial 1.7 to 0.8 mm. The results showed that higher screw speed, higher fiber content and two extrusions increased the shear energy, resulting in improved fiber dispersion but also caused fiber breakage and thermal degradation. The composites mechanical properties were not improved with better fiber dispersion and the reason for this might be the extensive fiber breakage and thermal degradation. Moreover, it was found that the PP polymer was also slightly degraded during the compounding process.

  • 2.
    Butylina, Svetlana
    et al.
    Lappeenranta University of Technology.
    Martikka, Ossi
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Kärki, Timo
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Thermal performance and optical properties of wood-polymer composites2013In: Journal of Thermoplastic Composite Materials, ISSN 0892-7057, E-ISSN 1530-7980, Vol. 26, no 1, p. 60-73Article in journal (Refereed)
    Abstract [en]

    The thermal performance and optical properties of wood-polypropylene composites made from untreated wood material with and without metal-containing pigments, and composites made from heat-treated wood material were studied. The thermal heat buildup and linear shrinkage were determined. The impact of the optical properties of the surface of the composites on the heat buildup was analysed. The wood-polypropylene composites made from untreated wood without pigment were found to have the lowest heat buildup; a similar composite containing grey pigment had the highest heat buildup. The linear shrinkage of the studied wood-polypropylene composites was in the range 0.05-0.16%

  • 3.
    Rozite, Liva
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Varna, Janis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Pupurs, Andrejs
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nonlinear behavior of PLA and lignin based flax composites subjected to tensile loading2013In: Journal of Thermoplastic Composite Materials, ISSN 0892-7057, E-ISSN 1530-7980, Vol. 26, no 4, p. 476-496Article in journal (Refereed)
    Abstract [en]

    The effect of temperature (T = 22°C, 30°C and 35°C) and relative humidity (RH = 34% and 66%) on mechanical behavior of natural fiber reinforced bio-based matrix composites subjected to tensile loading was investigated. Three composites were studied (a) polylactic acid (PLA) composite with 10% weight fraction of flax fibers; (b) PLA composite containing 5% viscose fibers (filaments of regenerated cellulose); (c) lignin-based composite with 30% of flax fibers. Elastic modulus, the nonlinear tensile stress–strain curves and failure were analyzed showing that all materials are temperature sensitive. The nonlinearity was analyzed studying modulus degradation as well as development of viscoelastic and viscoplastic strains. The modulus reduction in PLA-based composites starts after reaching the stress maximum and is not significant, whereas the modulus reduction in lignin-based composites starts before the maximum and it can reach 50%. With increasing RH these effects are slightly larger. The time-dependent phenomena were analyzed in short-term creep and strain recovery tests demonstrating significantly higher viscoplastic strain in lignin composites. Both viscoelastic and viscoplastic strains are larger at higher RH.

  • 4.
    Szpieg, Magdalena
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Giannadakis, Konstantinos
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Varna, Janis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Time-dependent nonlinear behavior of recycled polypropylene in high tensile stress loading2011In: Journal of Thermoplastic Composite Materials, ISSN 0892-7057, E-ISSN 1530-7980, Vol. 24, no 5, p. 625-652Article in journal (Refereed)
    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.

  • 5.
    Varna, Janis
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Berglund, Lars A.
    Luleå tekniska universitet.
    Ericson, Mats L.
    Linköpings universitet.
    Specimen size effects on modulus of GMT and other inhomogeneous composites1992In: Journal of Thermoplastic Composite Materials, ISSN 0892-7057, E-ISSN 1530-7980, Vol. 5, no 2, p. 105-114Article in journal (Refereed)
    Abstract [en]

    Mean values and standard deviations are often used to characterize certain mechanical properties. It is widely known that some properties, e.g., tensile strength of brittle solids and their standard deviations, are affected by the volume studied. In the pres ent study, the mean value and the standard deviation for the longitudinal elastic modulus of a cuboid specimen are treated. A model to predict the mean values and standard devia tions for varying lengths and widths is presented. Experimental data from the literature for glass mat reinforced polypropylene is used to show that the model shows excellent ac curacy with experimental data

1 - 5 of 5
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf