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Decrease of stiffness properties of degraded wood predicted by means of micromechanical modeling
Vienna University of Technology, Austria.ORCID iD: 0000-0002-7829-4630
Vienna University of Technology, Austria.
Norwegian Forest and Landscape Institute, Norway.
Georg-August-University of Göttingen, Germany.
2011 (English)In: Proceedings of the International Research Group on Wood Protection IRG/WP 11-40570, International Research Group on Wood Protection , 2011, 2-15 p.Conference paper, Published paper (Other academic)
Abstract [en]

Wood exhibits a highly anisotropic mechanical behavior due to its heterogeneous microscopic structure and composition. Its microstructure is organized in a strictly hierarchical manner from a length scale of some nanometers, where the elementary constituents cellulose, hemicelluloses, lignin, and extractives are found, up to a length scale of some millimeters, where growth rings composed of earlywood and latewood are observed. To resolve the microscale origin of the mechanical response of the macro-homogeneous but micro-heterogeneous material wood, micromechanical modeling techniques were applied. They allow for prediction of clear wood stiffness from microstructural characteristics. Fungal decay causes changes in the wood microstructure, expressed by modification or degradation of its components. Consequently, macroscopic mechanical properties are decreasing. Thus, in the same manner as for clear wood, consideration of alterations of wood in a micromechanical model allows predicting changes in the macroscopic mechanical properties. This contribution covers results from an extensive experimental program, where changes in chemophysical properties and corresponding changes in the mechanical behavior were investigated. For this purpose, Scots pine (Pinus sylvestris L.) sapwood samples were measured in the reference condition, as well as degraded by brown rot (Gloeophyllum trabeum) or white rot (Trametes versicolor). Stiffness properties of the unaffected and the degraded material were not only measured in uniaxial tension tests in the longitudinal direction, but also in the three principal material directions by means of ultrasonic testing. The experiments revealed transversal stiffness properties to be much more sensitive to degradation than longitudinal stiffness properties. This is due to the degradation of the polymer matrix between the cellulose fibers, which has a strong effect on the transversal stiffness. On the contrary, longitudinal stiffness is mainly governed by cellulose, which is more stable with respect to degradation by fungi. Consequently, transversal stiffness properties or ratios of normal stiffness tensor components may constitute suitable durability indicators. Subsequently, simple micromechanical models, as well as a multiscale micromechanical model for wood stiffness, were applied for verification of hypotheses on degradation mechanisms and model validation.

Place, publisher, year, edition, pages
International Research Group on Wood Protection , 2011. 2-15 p.
National Category
Wood Science
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
URN: urn:nbn:se:lnu:diva-51305OAI: oai:DiVA.org:lnu-51305DiVA: diva2:914409
Conference
42nd Annual Meeting, The International Research Group on Wood Protection, 8-12 May, 2011, Queenstown, New Zealand
Available from: 2016-03-23 Created: 2016-03-23 Last updated: 2016-04-27Bibliographically approved

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  • apa
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