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Stress-transfer mechanisms in wood-fibre composites
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , 12 p.
Series
Trita-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 0433
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4338OAI: oai:DiVA.org:kth-4338DiVA: diva2:11864
Presentation
2007-04-17, Sal D2, KTH, Lindstedtsvägen 5, Stockholm, 13:15
Opponent
Supervisors
Note

QC 20101102

Available from: 2007-04-19 Created: 2007-04-19 Last updated: 2013-01-15Bibliographically approved
List of papers
1. Dynamic-mechanical properties of wood-fibre reinforced polyactide: experimental characterization and micro-mechanical modelling
Open this publication in new window or tab >>Dynamic-mechanical properties of wood-fibre reinforced polyactide: experimental characterization and micro-mechanical modelling
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2006 (English)In: Journal of Thermoplastic Composite Materials, ISSN 0892-7057, E-ISSN 1530-7980, Vol. 19, no 6, 613-638 p.Article in journal (Refereed) Published
Abstract [en]

Wood-fiber reinforced polylactide is a biodegradable compositewhere both fibers and matrix are from renewableresources. When designing new materials of this kind, itis useful to measure the influence of fiber–matrixinterface properties on macroscopic mechanicalproperties. In particular, a quantitative measure of thedynamic stress transfer between the fibers andthe matrix when the material is subjected tocyclic loading would simplify the development of wood-fibercomposites. This is obtained by comparing themechanical dissipation of the composite with avalue predicted by a viscoelastic micromechanical model basedon perfect interfacial stress transfer. Theloss factors predicted by the model are 0.12 and 0.16 at dryand humid conditions, respectively, which amountto 63 and 66% of the experimentally determinedvalues. For Young's moduli the predicted values are 1.01 and0.88 GPa, which correspond to 92% of the experimentallydetermined values. The mismatch between thepredicted and experimental values may be attributed toimperfect interfaces with restrained stress transfer.Loss factors are also determined for specificmolecular bonds using dynamic Fourier transform infrared(FT-IR) spectroscopy. These values show the sametrends with regard to moisture content as themacroscopically determined loss factors.

Keyword
polylactide • wood fibers • micromechanics • stress transfer • imperfect interfaces • dynamic FT–IR
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-6991 (URN)10.1177/0892705706067480 (DOI)000241384300001 ()2-s2.0-33750180040 (Scopus ID)
Note
QC 20100714Available from: 2007-04-19 Created: 2007-04-19 Last updated: 2017-12-14Bibliographically approved
2. Effects of Moisture on Dynamic Mechanical Properties of Wood Fiber Composites Studied by Dynamic FT-IR Spectroscopy
Open this publication in new window or tab >>Effects of Moisture on Dynamic Mechanical Properties of Wood Fiber Composites Studied by Dynamic FT-IR Spectroscopy
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2008 (English)In: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 27, no 16-17, 1709-1721 p.Article in journal (Refereed) Published
Abstract [en]

Wood fiber reinforced polylactide is a biodegradable composite where both fibers and matrix are from renewable resources. In the development of such new materials, information on mechanical behavior on the macroscopic and the molecular level is useful. In this study, dynamic Fourier transform infrared (FT-IR) spectroscopy is used to measure losses at the molecular level during cyclic tensile loading for bonds that are characteristic of the cellulosic fibers and the polylactid matrix. This molecular behavior is compared with measured macroscopic hysteresis losses for different moisture levels. The results show that moisture ingress will transfer the load from the fibers to the matrix, and that a more efficient fiber-matrix interface would diminish mechanical losses. Although the dynamic FT-IR spectroscopy method is still qualitative, this investigation shows that it can provide information on the stress transfer of the constituents in wood fiber reinforced plastics.

Keyword
wood fiber, dynamic FT-IR, stress transfer, moisture, interface
National Category
Paper, Pulp and Fiber Technology Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-6992 (URN)10.1177/0731684407084663 (DOI)000260411900005 ()
Note
QC20100714. Tidigare titel "Effects of moisture on dynamic mechanical properties of wood-fibre reinforced polylactide studied by dynamic FT-IR spectroscopy. Available from: 2007-04-19 Created: 2007-04-19 Last updated: 2017-12-14Bibliographically approved
3. Role of fibre-fibre and fibre-matrix adhesion in stress transfer in composites made from resin-impregnated paper sheets.
Open this publication in new window or tab >>Role of fibre-fibre and fibre-matrix adhesion in stress transfer in composites made from resin-impregnated paper sheets.
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2009 (English)In: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 29, no 5, 551-557 p.Article in journal (Refereed) Published
Abstract [en]

Paper-reinforced plastics are gaining increased interest as packaging materials, where mechanical properties are of great importance. Strength and stress transfer in paper sheets are controlled by fibre-fibre bonds. In paper-reinforced plastics, where the sheet is impregnated with a polymer resin, other stress-transfer mechanisms may be more important. The influence of fibre-fibre bonds on the strength of paper-reinforced plastics was therefore investigated. Paper sheets with different degrees of fibre-fibre bonding were manufactured and used as reinforcement in a polymeric matrix. Image analysis tools were used to verify that the difference in the degree of fibre-fibre bonding had been preserved in the composite materials. Strength and stiffness of the composites were experimentally determined and showed no correlation to the degree of fibre-fibre bonding, in contrast to the behaviour of unimpregnated paper sheets. The degree of fibre-fibre bonding is therefore believed to have little importance in this type of material, where stress is mainly transferred through the fibre-matrix interface.

Keyword
Composites, Wood, Microscopy
National Category
Mechanical Engineering Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-6993 (URN)10.1016/j.ijadhadh.2008.11.002 (DOI)000265185300011 ()2-s2.0-62249147592 (Scopus ID)
Note
Tidigare titel: Comparison of stress-transfer mechanisms in paper sheets and composites med from resin-impregnated sheets. Uppdaterad från submitted till published: 20101102. QC 20101102Available from: 2007-04-19 Created: 2007-04-19 Last updated: 2017-12-14Bibliographically approved

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