Effect of Thermal Modification of Wood on Strength and Elasticity Modulus in Static Bending

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UDС

[674.049.2+674.046.7]

DOI:

10.17238/issn0536-1036.2015.6.85

Abstract

The paper presents the experimental results of physical and mechanical properties of ther-mally modified timber of pine (P?nus sylv?stris), birch (B?tula P?ndula), oak (Qu?rcus R?-bur), aspen (Tilia europaea) and lime (P?pulus tr?mula). Wood samples’ heating was car-ried out in a saturated steam medium in a steam convection section and atmospheric pres-sure at maximum temperatures of 180 ?С, 200 ?С and 220 ?С and the duration of treatment at a peak value of 3 hours. The values of mass loss and the change in density when dry, specified moisture content, elasticity modulus and tensile strength at static bending were defined. The increase in mass loss was significant for all wood species. Maximum mass loss was determined for oak, lime and aspen wood specimens at average values of 17.8 %, 13.4 % and 16.5 % respectively, at a maximum temperature of 220 ?С. The density of thermally modified wood was reduced with increasing treatment temperature and reached the mini-mum values for wood of oak and aspen. Elasticity modulus at static bending increased for different species on average of 10…20 % for peak processing temperatures of 180 ?С and 200 ?С and subsequently reduced by increasing the temperature up to 220 ?С. The ultimate strength at static bending is increased for birch samples, treated at 180 ?С, on average of 12.5 %, pine – 14.5 % and lime – 9.2 %. With the rise of peak processing temperature up to 200 ?С the maximum reduction of ultimate strength of wood was observed in oak samples (on average 19.5 %). For birch and lime samples the decrease was insignificant – 3.5 % and 0.5 % in comparison with the unmodified samples. The rise of ultimate strength was ob-served for aspen samples of 23 % and 11.5 % for the 180 ?С and 200 ?С. The maximum decrease of the ultimate strength at static bending was marked for all species in the heat treatment temperature of 220 ?С, that was compared to unmodified samples for birch – 31.5 %, oak – 38.9 %, pine – 9.5 %, lime – 4.6 % and 11.5 % of aspen.

Authors

E.S. Sharapov, Candidate of Engineering Sciences, Associate Professor A.S. Toropov, Doctor of Engineerig Sciences, Professor A.S. Korolev, Postgraduate Student

Affiliation

Volga State University of Technology, Lenin sq., 3, Yoshkar-Ola, Republic of Mari El, 424000, Russian Federation; е-mail: sharapoves@volgatech.net

Keywords

thermally modified timber, mass loss, density, elasticity modulus at static bend-ing, static modulus.

References

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