The aim of the thesis was to examine the influence of convective drying on the mechanical properties of common ash wood (Fraxinus excelsior L.) with particular attention given to changes in the modulus of elasticity depending on wood moisture content. Static three-point bending tests and measurements of dynamic modulus of elasticity were carried out under longitudinal and transverse bending vibrations of the specimens. A total of 23 specimens with radial and tangential orientation were analysed, with moisture content monitored using electrical resistance and gravimetric methods. Over a period of 451 hours, the average moisture content of the wood decreased from 24.8% to 11.4%, with an average drying rate of 0.48% per day. The results showed that with decreasing moisture content, the static modulus of elasticity generally increased, while the dynamic modulus increased to a lesser extent; however, the relationship was not statistically significant (R2 < 0.5). The highest average modulus of elasticity in static tests was 10,296 MPa. On average, tangentially oriented samples achieved higher values of the dynamic modulus than radially oriented ones. The dispersion of dynamic measurement results suggest that wood structure and drying-induced stresses – particularly those resulting from local moisture gradients – have a stronger influence on stiffness properties. Simultaneous monitoring of moisture content and mechanical properties proved to be a useful approach for optimizing the drying process.
|
