Effect of heat treatments on the strength and stiffness of poplar

Abstract

The influence of environmental conditions on wood material properties is known. Temperature is one of them and its effect on poplar wood has been examined in a limited way which this study tried to figure out this issue in a limited context. The influence of heat treatment (110 °C, 160 °C, and 210 °C for 3 h and 6 h) on the density, ultrasonic wave velocity, modulus of rupture, and modulus of elasticity of poplar wood was evaluated. A 2,25 MHz longitudinal ultrasonic wave was used to determine both the ultrasonic wave velocity and the dynamic modulus of elasticity. A three-point bending test was conducted to determine the static modulus of elasticity and the modulus of rupture. The average values for the control samples were 350 kg/m³ for density, 3 598 m/s for ultrasonic wave velocity, 4 552 MPa for dynamic modulus of elasticity, 5 864 MPa for static modulus of elasticity, and 64,1 MPa for modulus of rupture. When samples were treated at 210 °C for 6 h, these properties decreased by 14,3 %, 3 %, 18,7 %, 25 %, and 50,2 %, respectively. In general, the dynamic modulus of elasticity values were lower than the static ones across all treatment conditions. The greatest difference between dynamic and static modulus (34 %) was observed at 110 °C for 6 h, while the smallest difference (18,8 %) occurred at 210 °C for 6 h. Improvements of up to 8,9 %, 2,4 %, and 0,85 % were observed in the modulus of rupture, static modulus of elasticity, and ultrasonic wave velocity, respectively, at 110 °C treatments.

Keywords

• Bending strength
• non-destructive testing
• thermal modification
• modulus of elasticity
• Populus canadensis
• ultrasound