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Wood tensile strength at temperatures and moisture contents simulating fire conditions (1985)

Östman, B. A.. -L.

Springer

Wood science and technology 19 (1985), S. 103-116

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ISSN: 1432-5225

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Summary The immediate tensile strength parameters for spruce parallel to the grain and for hardboard have been determined at equilibrium conditions at temperatures up to 250°C. Below 100°C the moisture content has been varied between 0 and 30%. Above 100°C dry samples have been studied. An increase in moisture content up to about 12% leads to a slight increase in the tensile strength of spruce whereas the modulus of elasticity remains constant. With a further increase in moisture content, both properties decrease significantly. At any given moisture content, both properties decrease with increasing temperature. The corresponding strain at rupture is constant. An increase in temperature leads to a more or less linear decrease in the tensile strength and in the modulus of elasticity up to about 200°C. Above 200°C there is a more rapid decrease due to thermal softening. It is most relevant to consider the relative strength decrease since the absolute levels may be quite high due to the fact that wood samples without any irregularities were used. Such relative strength data are compared with the small amount of similar data found in the literature. The effects on the modulus of elasticity are discussed in terms of thermal softening and of water as a softener for the cellulose/hemicellulose polymers. The glass transition temperature is determined as a function of the moisture content.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00353071

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Comparison of three test methods for measuring rate of heat release (1985)

Östman, B. A-L. ; Svensson, I. G. ; Blomqvist, J.

New York, NY [u.a.] : Wiley-Blackwell

Fire and Materials 9 (1985), S. 176-184

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ISSN: 0308-0501

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Three test methods for measuring the rate of heat release, RHR, have been compared on the same building materials. The test methods are the OSU-box modified for O2-consumption, the STFI open arrangement and the NBS cone calorimeter. All methods are based on the oxygen-consumption technique. Radiation intensities up to 50 k Wm-2 have been applied. Thirteen different materials were tested. The results obtained using the three methods seem to be quite similar in spite of the different equipment used. The minor deviations observed in the results seem to be systematic and may be due to the different testing arrangements. There is a good correlation between results, e.g. total heat release up to 1min after ignition, obtained by the different methods. Additional information about the time to ignition is obtained simultaneously. Heat-release rates in the vertical and horizontal orientations are also compared in the NBS cone calorimeter.

Additional Material: 9 Ill.