Hygro-mechanical behavior of thermally treated beech subjected to compression loads

Straže, Aleš; Fajdiga, Gorazd; Pervan, Stjepan; Gorišek, Željko

doi:10.1016/j.conbuildmat.2016.03.038

Cited by 10 publications

(9 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Arnold (2010) studied the MC effect of thermally modified beech and spruce wood on the bending strength and revealed that the mechanical parameters of these two wood species after modification undergo smaller changes with increasing MC to the fibre saturation point (FSP) than the analogous parameters of unmodified wood. Similar conclusions have been drawn from the study of thermally modified beech wood subjected to compression parallel and perpendicular to the grain (Straže et al 2016). The above authors studied the variation in wood mechanical properties over the entire hygroscopic range.…”

Section: Introductionsupporting

confidence: 61%

Swelling restraint of thermally modified ash wood perpendicular to the grain

Majka

Roszyk

2018

Eur. J. Wood Prod.

View full text Add to dashboard Cite

The paper reports on creep of ash wood (Fraxinus excelsior L.) thermally modified at 180 and 200 °C, and subsequently subjected to compression in tangential and radial directions and simultaneously wetted, from the moisture content (MC) of 6% to above the fibre saturation point (FSP). The compressing load made 0.00, 0.25, 0.50 and 0.75 of impact stress at the proportional limit (R c). The compression stress needed to restrain the swelling of wood, the so-called swelling pressure, was indirectly determined from isochrones of mechano-sorptive creep. The most important finding was that thermal modification reduces the strain of ash wood subjected to compression perpendicular to the grain to a degree proportional to the mass loss. The compression stress needed to restrain the swelling of thermally modified wood is ca. 10 and 20% smaller in the tangential and radial directions, respectively. This effect leads to a reduction in the anisotropy of swelling pressure of thermally modified wood perpendicular to the grain. Moreover, although upon thermal modification the mass loss of wood takes place, at the MC of 6% it shows practically the same modulus of elasticity (MOE) and Rc as the unmodified wood. After wetting to MC higher than the FSP, the thermally modified wood at 200 °C shows significantly higher MOE and Rc than the wood modified at 180 °C and untreated wood. Reduction of wood hygroscopicity, an inevitable effect of thermal modification, also reduces the range of changes in mechanical properties of wood caused by the increase in its MC to the FSP.

show abstract

Section: Introductionsupporting

confidence: 61%

Swelling restraint of thermally modified ash wood perpendicular to the grain

Majka

Roszyk

2018

Eur. J. Wood Prod.

View full text Add to dashboard Cite

show abstract

“…An increase in the compressive strength of thermowood can be explained with a relative increase in the lignin content and its condensation confirmed by the near infrared spectroscopy (NIR) [55]. It is supposed that an increase in the modulus of elasticity of thermowood relates to forming new chemical bonds with higher bond energy in comparison to the energy of absent hydrogen bonds [57].…”

Section: The Impact Bending Strength and Brinell Hardnessmentioning

confidence: 99%

“…Lots of researchers found out that mechanical properties of wood like compressive strength [22] bending strength [21] and hardness [21,22] can be improved by impregnating the wood with waxes. Mechanical properties of wood like hardness [17,54], bending strength [54], compressive strength [54][55][56] and modulus of elasticity [57] were improved also under milder conditions of its thermal modification. An increase in the compressive strength of thermowood can be explained with a relative increase in the lignin content and its condensation confirmed by the near infrared spectroscopy (NIR) [55].…”

Section: The Impact Bending Strength and Brinell Hardnessmentioning

confidence: 99%

The Impact of Paraffin-Thermal Modification of Beech Wood on Its Biological, Physical and Mechanical Properties

Reinprecht¹,

Repák²

2019

Forests

View full text Add to dashboard Cite

The European beech (Fagus sylvatica L.) wood was thermally modified in the presence of paraffin at the temperatures of 190 or 210 °C for 1, 2, 3 or 4 h. A significant increase in its resistance to the brown-rot fungus Poria placenta (by 71.4%–98.4%) and the white-rot fungus Trametes versicolor (by 50.1%–99.5%) was observed as a result of all modification modes. However, an increase in the resistance of beech wood surfaces to the mold Aspergillus niger was achieved only under more severe modification regimes taking 4 h at 190 or 210 °C. Water resistance of paraffin-thermally modified beech wood improved—soaking reduced by 30.2%–35.8% and volume swelling by 26.8%–62.9% after 336 h of exposure in water. On the contrary, its mechanical properties worsened—impact bending strength decreased by 17.8%–48.3% and Brinell hardness by 2.4%–63.9%.

show abstract

“…Elastomechanical anisotropy of heat-treated wood has not been widely studied so far. However, some researchers report the increase in the mechanical anisotropy of wood, but already in the area of plastic deformations, where they determined the increase in the ratio of compression strength of wood along-and transverse to the grain [43,44].…”

Section: Discussionmentioning

confidence: 99%

Nondestructive Characterization of Dry Heat-Treated Fir (Abies Alba Mill.) Timber in View of Possible Structural Use

Straže

Fajdiga

Gospodarič

2018

Forests

Self Cite

View full text Add to dashboard Cite

The use of heat-treated timber for building with wood is of increasing interest. Heat treatment improves the durability and dimensional stability of wood; however, it needs to be optimized to keep wood's mechanical properties in view of the possible structural use of timber. Therefore, dry vacuum heat treatment varying the maximum temperature between 170 • C and 230 • C was used on fir (Abies alba Mill.) structural timber, visually top graded according to EN 338, to analyze its final weight loss, hygroscopicity, CIELAB color, and dynamic elastomechanical properties. It turned out that weight loss and total color difference of wood positively correlates with the increasing intensity of the heat treatment. The maximum 40% reduction of the hygroscopicity of wood was already reached at 210 • C treatment temperature. The moduli of elasticity in longitudinal and radial direction of wood, determined by ultrasound velocity, increased initially up to the treatment temperature of 210 • C, and decreased at higher treatment temperature. Equally, the Euler-Bernoulli modulus of elasticity from free-free flexural vibration of boards in all five vibration modes increased with the rising treatment temperature up to 190 • C, and decreased under more intensive treatment conditions. The Euler-Bernoulli model was found to be valid only in the 1st vibration mode of heat-treated structural timber due to the unsteady decrease in the evaluated moduli of elasticity related to the increasing mode number.

show abstract

Hygro-mechanical behavior of thermally treated beech subjected to compression loads

Cited by 10 publications

References 26 publications

Swelling restraint of thermally modified ash wood perpendicular to the grain

Swelling restraint of thermally modified ash wood perpendicular to the grain

The Impact of Paraffin-Thermal Modification of Beech Wood on Its Biological, Physical and Mechanical Properties

Nondestructive Characterization of Dry Heat-Treated Fir (Abies Alba Mill.) Timber in View of Possible Structural Use

Contact Info

Product

Resources

About