Effect of Drying at 120 °C and 150 °C on Selected Mechanical Properties of Silver Fir (Abies alba Mill.)

Abstract

High-temperature drying can considerably improve drying efficiency. However, information on its impact on the mechanical properties of silver fir during industrial high-temperature drying remains limited. Elevated drying temperatures may induce changes in wood structure that can influence mechanical performance. This study evaluated the effect of high-temperature drying schedules based on industrially applied temperature levels (120 °C and 150 °C) on selected mechanical properties of silver fir (Abies alba Mill.). Wood samples were kiln-dried at 120 °C and 150 °C, conditioned to equilibrium moisture content, and tested for impact bending strength, tensile strength perpendicular to the grain, and Janka hardness. Because the experimental material originated from a single silver fir tree, the findings should be interpreted as describing responses within the investigated material rather than as population-level effects for silver fir. The results showed that drying at 150 °C was associated with a tendency toward reduced values of selected mechanical properties; however, the effect of drying temperature was not statistically significant for impact bending strength. ANOVA showed that specimen thickness significantly affected impact bending strength and Janka hardness, whereas drying temperature had a significant effect only on tensile strength perpendicular to the grain. The lowest mean values were observed in the β-150 group, with impact bending strength of 5.4 J·cm−2 and tensile strength perpendicular to the grain of 2.3 MPa. The mean oven-dry density was 456.9 kg·m−3, while only weak relationships between density and mechanical properties were observed (r2 = 0.023–0.178). This suggests that factors related to drying conditions may contribute to variability in mechanical performance beyond the effect of density alone. Thus, the effects of the investigated drying conditions were property-specific rather than consistently attributable to drying temperature. Within the investigated material, these results indicate that the optimization of high-temperature drying schedules should consider both drying parameters and variability in mechanical properties.