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Journal of Wood Science

, Volume 56, Issue 6, pp 437–443 | Cite as

High-temperature mechanical properties and thermal recovery of balsa wood

  • Thomas Goodrich
  • Nadia Nawaz
  • Stefanie Feih
  • Brian Y. Lattimer
  • Adrian P. Mouritz
Original Article

Abstract

This article presents an experimental study into thermal softening and thermal recovery of the compression strength properties of structural balsa wood (Ochroma pyramidale). Balsa is a core material used in sandwich composite structures for applications where fire is an ever-present risk, such as ships and buildings. This article investigates the thermal softening response of balsa with increasing temperature, and the thermal recovery behavior when softened balsa is cooled following heating. Exposure to elevated temperatures was limited to a short time (15 min), representative of a fire or postfire scenario. The compression strength of balsa decreased progressively with increasing temperature from 20° to 250°C. The degradation rates in the strength properties over this temperature range were similar in the axial and radial directions of the balsa grains. Thermogravimetric analysis revealed only small mass losses (<2%) in this temperature range. Environmental scanning electron microscopy showed minor physical changes to the wood grain structure from 190° to 250°C, with holes beginning to form in the cell wall at 250°C. The reduction in compression properties is attributed mostly to thermal viscous softening of the hemicellulose and lignin in the cell walls. Post-heating tests revealed that thermal softening up to 250°C is fully reversible when balsa is cooled to room temperature. When balsa is heated to 250°C or higher, the post-heating strength properties are reduced significantly by decomposition processes of all wood constituents, which irreversibly degrade the wood microstructure. This study revealed that the balsa core in sandwich composite structures must remain below 200°–250°C when exposed to fire to avoid permanent heat damage.

Key words

Balsa Thermal Mechanical properties Decomposition 

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References

  1. 1.
    Mouritz AP, Gibson AG (2006) Fire properties of polymer composite materials. Springer, DordrechtGoogle Scholar
  2. 2.
    Looyeh MRE, Rados K, Bettess P (2001) Thermomechanical response of sandwich panels to fire. Finite Elem Anal Des 37:913–927CrossRefGoogle Scholar
  3. 3.
    Mouritz AP, Gardiner C (2002) Compression properties of fire-damaged polymer sandwich composites. Composites 33A:609–620Google Scholar
  4. 4.
    Lattimer BY (2004) Large-scale fire resistance tests on sandwich composite materials. In: Proceedings of SAMPE 04. Long Beach, CA, May 16–20, 2004Google Scholar
  5. 5.
    Birman V (2005) Thermally induced bending and wrinkling in large aspect ratio sandwich panels. Composites 36A:1412–1420Google Scholar
  6. 6.
    Birman V, Kardomateas GA, Simitses GJ, Li R (2006) Response of a sandwich panel subjected to fire or elevated temperature on one of the surfaces. Composites 37A:981–988Google Scholar
  7. 7.
    Feih S, Mathys Z, Gibson AG, Mouritz AP (2008) Modelling compressive skin failure of sandwich composites in fire. J Sandw Struct Mater 10:217–245CrossRefGoogle Scholar
  8. 8.
    Krysl P, Ramroth WT, Steward LK, Asaro RJ (2004) Finite element modeling of fibre-reinforced polymer sandwich composites exposed to heat. Int J Num Meth Eng 61:49–68CrossRefGoogle Scholar
  9. 9.
    Gu P, Asaro RJ (2008) Distortion of polymer matrix composite panels under transverse thermal gradients. Comp Struct 82:413–412CrossRefGoogle Scholar
  10. 10.
    Gu P, Asaro RJ (2008) Wrinkling of sandwich polymer matrix composite panels under transverse thermal gradients. Fire Saf J 43:151–160CrossRefGoogle Scholar
  11. 11.
    Gu P, Asaro RJ (2008) Designing polymer matrix composite panels for structural integrity in fire. Compos Struct 84:300–309CrossRefGoogle Scholar
  12. 12.
    Gu P, Asaro RJ (2009) Designing sandwich polymer matrix composite panels for structural integrity in fire. Compos Struct 88:461–467CrossRefGoogle Scholar
  13. 13.
    Schaffer EL (1973) Effect of pyrolytic temperatures on the longitudinal strength of dry Douglas fir. J Test Eval 1:319–332CrossRefGoogle Scholar
  14. 14.
    Irvine GM (1985) The significance of the glass transition of lignin on thermomechanical pulping. Wood Sci Technol 19:139–149CrossRefGoogle Scholar
  15. 15.
    Uhmeier A, Morooka T, Norimoto (1998) Influence of thermal softening and degradation on the radial compression behaviour of wet spruce. Holfforschung 52:77–81CrossRefGoogle Scholar
  16. 16.
    Furuta Y, Kohara M, Kanayama K (1999) Thermal-softening properties of water-swollen wood. VI. The change of thermal-softening properties due to lignification with moso bamboo as a model material. Mokuzai Gakkaishi 45:193–198Google Scholar
  17. 17.
    Lenth CA, Kamket FA (2001) Moisture dependent softening behaviour of wood. Wood Fiber Sci 33:492–507Google Scholar
  18. 18.
    Yildiz S, Gezer ED, Yildiz UC (2006) Mechanical and chemical behaviour of spruce wood modified by heat. Build Environ 41: 1762–1766CrossRefGoogle Scholar
  19. 19.
    Boonstra MJ, Van Acker J, Tjeerdsdma BF, Kegel EV (2007) Strength properties of thermally modified softwoods and its relation to polymeric structural wood components. Ann Forest Sci 64:679–690CrossRefGoogle Scholar
  20. 20.
    Esteves BM, Pereira HM (2009) Wood modification by heat treatment: A review. BioResources 4:370–404Google Scholar
  21. 21.
    Easterling KE, Harryson R, Gibson LJ, Ashby MF (1982) On the mechanics of balsa and other woods. Proc R Soc London, A383: 31–41Google Scholar
  22. 22.
    Salmen L (1984) Viscoelastic properties of in situ lignin under water-saturated conditions. J Mater Sci 19:3090–1096CrossRefGoogle Scholar
  23. 23.
    Szczesniak L, Rachocki A, Tritt-Goc J (2008) Glass transition temperature and thermal decomposition of cellulose powder. Cellulose 15:445–451CrossRefGoogle Scholar
  24. 24.
    Ramiah MV (1970) Thermogravimetric and differential thermal analysis of cellulose, hemicellulose, and lignin. J Appl Polymer Sci 14:1323–1337CrossRefGoogle Scholar

Copyright information

© The Japan Wood Research Society 2010

Authors and Affiliations

  • Thomas Goodrich
    • 1
  • Nadia Nawaz
    • 2
  • Stefanie Feih
    • 2
  • Brian Y. Lattimer
    • 1
  • Adrian P. Mouritz
    • 2
  1. 1.Department of Mechanical EngineeringVirginia Polytechnic Institute and State UniversityBlacksburgUSA
  2. 2.School of Aerospace, Mechanical and Manufacturing EngineeringRMIT UniversityMelbourneAustralia

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