Comparison of Stiffness and Strength Properties of Untreated and Heat-Treated Wood of Douglas Fir and Alder

Abstract

This paper investigates the effect of heat treatment temperature on the stiffness and strength properties of Douglas fir (Pseudotsuga menziesii Franco) and common alder (Alnus glutinosa Gaertn.) woods. Two temperatures of heat treatment were used: 165 and 210 °C. The effects of dynamic elasticity modulus, static elasticity modulus, impact toughness, bending strength, and density were evaluated. It is already understood that the mechanical properties, primarily the bending strength, decreases with increasing temperature. In contrast to the favorable stability in shape and dimension that was achieved, the changes in the woods' properties with temperature were mostly negative. Higher heat treatment temperatures corresponded with lower stiffness and strength properties. For higher temperature treatments, above 200 °C, deterioration of the tested properties was noticable as a result of the significant changes in the wood chemical structure. Even the positive effect of the equilibrium moisture decrease was not able to counterbalance the unfavorable changes. Moreover, it was observed that as the hemicellulose content is higher in alder wood, density, static bending strength, and toughness all decreased steadily at high temperatures, compared to Douglas fir wood.

Elastic and Strength Properties of Heat-Treated Beech and Birch Wood

“…Expected correlation (as stated Dinwoodie [49]) between statistical and dynamical MOEs has proved to be not very significant for possible predictions, especially for heat-treated wood (see Figure 6e,f). The explanation has already been described in detail in research by Borůvka [37], i.e., the different influence of moisture content during the measurement of dynamic and static moduli, as well as the existence of shear stress during the static three-point bending test. Interestingly, there is a considerable difference in the width of the annual rings between the two trees, with the birch having more than three times the width of the beech, but the density of both trees was more or less standard, within the limits indicated in the literature ( Table 2).…”

“…The aim of this study was to compare beech and birch wood and to better explain the effect of thermal treatment on their physical and mechanical properties. The related objective of this paper was primarily to verify the negativity of the higher level of treatment of deciduous woods ("210") against conifers (see [37]). This hypothesis has been completely confirmed and it is clear that for the mentioned species, the maximum temperature is about 200 • C. Above this temperature, there are already significant changes in the chemical structure, especially the hemicellulose components (see more information in Introduction).…”

Effect of surface carbonization on mechanical properties of LVL

“…The IT of the panels with the carbonized surfaces were all lower than those of the control, which decreased 64%, 38.3%, 42.2%, and 8.4% as the surface layer of LVL was heated at 120 °C, 160 °C, 200 °C, and 240 °C, respectively. Different from solid Douglas fir and alder wood, of which the IT values decreased with increased heating temperature (Borůvka et al 2015), the IT loss of the LVL was mainly alleviated with the increase in surface heating temperature from 120 °C to 240 °C. This decrease was possibly due to a complex chemical change under different temperatures in wood (Hughes et al 2015), and a synergistic effect of the mixed panel structure with both heated and unheated veneers in the LVL (Yu and Fan 2017).…”

Integration of Taguchi-Grey relational analysis technique in parameter process optimization for rice husk composite

“…The compatibilizer agent functioned as an effective binder with good adhesion. It is important for polymers to have filler content with uniform blending to maintain their physical properties (Borůvka et al 2015). Its low molecular weight reduced the viscosity during the process, hence enhancing flow characteristics.…”