Holz als Roh- und Werkstoff

, Volume 66, Issue 1, pp 63–69 | Cite as

Mechanical behavior of heat-treated spruce (Picea abies) wood at constant moisture content and ambient humidity

  • Marc BorregaEmail author
  • Petri P. Kärenlampi
Originalarbeiten Originals


The mechanical behavior of heat-treated spruce wood was investigated in relation to the mass loss that occurs during thermal treatment. At constant wood moisture content, the strength, failure strain and toughness of wood were reduced by the heat-bath treatment, decreasing with increasing mass loss. The stiffness was unaffected up to a mass loss of about 3%, and thereafter it decreased. The mechanical properties, however, are not only dependent on the mass loss but also on the relative humidity in the heating atmosphere. As a function of mass loss, the inelastic ductility and the inelastic toughness were the lowest when wood was heated in a dry climate, as compared to a moist climate.

On the other hand, the mechanical properties of heat-treated wood were tested at constant ambient humidity. In such circumstances, the failure strain and the toughness were still reduced, but the strength and the stiffness were actually improved up to a mass loss of about 2%–3%. The improvement is due to the lower equilibrium moisture content of heat-treated wood when placed in service conditions. As a function of mass loss, wood heated at intermediate relative humidity (in the vicinity of 50%) exhibited the best mechanical behavior, which surprisingly included inelastic ductility. This is believed to be due to some irreversible hydrogen bonding.


Mass Loss Equilibrium Moisture Content Failure Strain Reference Specimen Increase Mass Loss 
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Mechanisches Verhalten von wärmebehandeltem Fichtenholz (Picea abies) bei konstanter Holz- und Luftfeuchte


Das mechanische Verhalten von wärmebehandeltem Fichtenholz wurde in Zusammenhang mit dem bei der Wärmebehandlung auftretenden Masseverlust untersucht. Durch die Wärmebadbehandlung nahmen die Festigkeit, Bruchdehnung und Zähigkeit bei konstanter Holzfeuchte mit zunehmendem Masseverlust ab. Die Steifigkeit nahm erst ab einem Masseverlust von ungefähr 3% ab. Die mechanischen Eigenschaften hängen jedoch nicht nur vom Masseverlust ab, sondern auch von der relativen Luftfeuchte bei der Wärmebehandlung. Bezogen auf den Masseverlust waren der nicht elastische Anteil der Bruchdehnung und der nicht elastische Anteil der Zähigkeit bei Holz, das in trockenem Klima wärmebehandelt wurde, niedriger als bei einer Behandlung in feuchtem Klima.

Daneben wurden die mechanischen Eigenschaften von wärmebehandeltem Holz bei konstanter Luftfeuchte untersucht. Unter diesen Bedingungen nahmen Bruchdehnung sowie Zähigkeit ebenfalls ab, jedoch verbesserte sich die Festigkeit und Steifigkeit bis zu einem Masseverlust von 2%–3%. Dies ist auf die niedrigere Gleichgewichtsfeuchte von wärmebehandeltem Holz unter Praxisbedingungen zurückzuführen. Bezogen auf den Masseverlust zeigte Holz, das bei mittlerer relativer Luftfeuchte (ca. 50%) wärmebehandelt wurde, die besten mechanischen Eigenschaften. Erstaunlicherweise gilt dies auch für den nicht elastischen Anteil der Bruchdehnung, was wahrscheinlich auf irreversible Wasserstoffbindungen zurückzuführen ist.


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Faculty of Forest SciencesUniversity of JoensuuJoensuuFinland

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