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European Journal of Wood and Wood Products

, Volume 69, Issue 4, pp 557–563 | Cite as

Characterization of radial bending properties of cork

  • Ofélia AnjosEmail author
  • Helena Pereira
  • Maria Emília Rosa
Originals Originalarbeiten

Abstract

The behaviour of cork under three point bending stress in the radial direction was evaluated in relation to porosity (range 2.0–15.4%) and density (range 0.160–0.220 g cm−3). The study was made using water-boiled cork planks of two commercial quality classes (good and poor quality) collected at an industrial mill. Cork samples were cut with the largest dimension in two directions, axial and tangential, and with the load zone in the inner part and the outer part of the plank.

The stress-strain curves obtained in bending were similar for the different test specimens and similar to those observed for tensile tests in cork but the mechanical resistance of cork in bending was higher than in tension and lower than in compression. The direction of the internal stress in samples submitted to bending was a highly significant factor of variation. The curves showed an initial linear elastic region with a mean Young’s modulus of 14 MPa for the tangential direction and 21 MPa for the axial direction, followed by a region of a gradual cork yielding up to a peak load, and failure at an average stress of 1.2 MPa and a strain of 14%. There was significant difference in the bending properties of cork samples obtained from cork planks of different quality classes.

Density and porosity were not individually well correlated with the mechanical parameters. It was however possible to model Young’s modulus by combining porosity and density.

Keywords

Fracture Stress Tangential Direction Fracture Strain Quality Classis Tangential Surface 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Radiale Biegeeigenschaften von Kork

Zusammenfassung

Untersucht wurde das Verhalten von Kork in radialer Richtung im Drei-Punkt-Biege-Versuch in Abhängigkeit der Porosität (im Bereich von 2,0–15,4 %) und der Dichte (im Bereich von 0,160–0,220 g cm−3). Untersucht wurden in Wasser gekochte Korkplatten zweier Handelsklassen (gute und schlechte Qualität), die in einem Betrieb entnommen wurden. Die Proben wurden mit ihrer größten Abmessung in axialer bzw. tangentialer Richtung ausgeformt und mit der innen liegenden beziehungsweise außen liegenden Seite im Biege-Zugbereich geprüft.

Die Spannungs-Dehnungskurven der verschiedenen Proben verliefen ähnlich, und sie entsprachen denjenigen der Zugversuche. Die Biegefestigkeit war jedoch höher als die Zugfestigkeit und niedriger als die Druckfestigkeit. Einen großen Einfluss hatte dabei die Orientierung der Proben. Die Proben wiesen einen zunächst linear elastischen Bereich auf, mit einem mittleren E-Modul von 14 MPa bei den in tangentialer Richtung ausgeformten Proben und von 21 MPa für die axialen Proben, mit einem anschließenden nicht-linearen Bereich bis zu einer Bruchfestigkeit von im Mittel 1,2 MPa und einer Bruchdehnung von 14 %. Die Biegeeigenschaften der Korkproben der beiden Handelsklassen waren signifikant verschieden.

Die Parameter Dichte und Porosität waren jeder für sich mit den mechanischen Eigenschaften nicht hoch korreliert. Es war jedoch möglich, den E-Modul als Funktion von Dichte und Porosität zu modellieren.

Notes

Acknowledgements

We thank Subercentro Cortiças, Lda. in Ponte de Sor, Portugal, for the cork planks and Pedro Pina for his help to develop the image analysis algorithm.

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Ofélia Anjos
    • 1
    • 2
    • 4
    Email author
  • Helena Pereira
    • 2
  • Maria Emília Rosa
    • 3
  1. 1.Unidade Departamental de Silvicultura e Recursos NaturaisEscola Superior Agrária de Castelo BrancoCastelo BrancoPortugal
  2. 2.Centro de Estudos Florestais, Instituto Superior de AgronomiaUniversidade Técnica de LisboaLisboaPortugal
  3. 3.Departamento de Engenharia de Materiais, Instituto Superior TécnicoUniversidade Técnica de LisboaLisboaPortugal
  4. 4.Centro de Estudos de Recursos NaturaisAmbiente e Sociedade (CERNAS)CoimbraPortugal

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