The effect of ultrastructure and moisture content on mechanical parameters of pine wood (Pinus sylvestris L.) upon tensile stress along the grains

Abstract

IntroductionIt has been known for a long time that the effect of moisture on mechanical parameters of wood during tensile stress is different for early and latewood. As follows from the studies from the 1960s on pine wood (Pinus taeda L.), an increase in the moisture content from an air-dry state to a wet state leads to a decrease in the tensile strength of only 13% for earlywood and as much as 30% for latewood (Biblis, 1969). According to the measurements performed on Douglas-fir wood (Pseudotsuga menziesii Franco), the tensile strength of earlywood in an air-dry state is practically the same as in a wet state, and its linear modulus of elasticity in a wet state is about 20% lower than in an air-dry state. Specific work to ultimate load of wet earlywood can be 16% higher than that of air-dry wood. The tensile strength and modulus of elasticity of wet latewood are over 40% lower and the specific work to ultimate load is 50% lower than their correspondents in air-dry latewood (Helińska-Raczkowska and Raczkowski, 1979). Recently, Roszyk et al. (2013) showed that for, pine wood (Pinus sylvestris L.), the main mechanical parameters of earlywood subjected to tensile stress (immediate strength, modulus of elasticity, stress at the proportional limit) are practically independent of its moisture content. However, they reported that wet earlywood becomes damaged at a higher strain than air-dry wood. Although the main

Mechanical Properties of Earlywood and Latewood Sections of Scots Pine Wood

“…The MFA in the S2 layer of the EW were generally higher compared to LW. Thus, the tensile strength of EW was usually lower than that of LW (Wimmer et al 1997;Mott et al 2002;Moliński and Krauss 2008;Roszyk 2014). In the small MFA values, the cellulose determined the behaviour of the wood under tensile stress.…”

“…The difference in the tensile strength of EW and LW could be attributed to the differences in density and MFA of EW and LW. Roszyk (2014) determined the MFA were 16.4° and 9.0°, and the average density was 235 kg/m 3 and 665 kg/m 3 in EW and LW of scots pine, respectively. The MFA in the S2 layer of the EW were generally higher compared to LW.…”

“…The lower bending strength values of EW could be attributed to the lower density and higher MFA of EW compared to LW. Roszyk (2014) determined the lower density and the higher MFA values in EW of scots pine. The ratio of LW to EW bending strength was 2.51:1.…”

“…The MFA in the S2 layer of the EW are generally higher compared to the LW MFA. Roszyk (2014) determined that the MFA were 16.4° and 9.0°, and the average density was 235 kg/m 3 and 665 kg/m 3 in the EW and LW of Scots pine, respectively.…”

Comparison of Micro- and Standard-Size Specimens in Evaluating the Flexural Properties of Scots Pine Wood

“…The microfibril angles (MFA) in the S2 layer of the EW are generally higher compared to LW MFA. Roszyk (2014) determined the MFA were 16.4° and 9.0° and the average density were 235 kg/m 3 and 665 kg/m 3 in EW and LW of scots pine, respectively. Similar lower values were found by Deomano (2001).…”