Measurement of the elastic parameters of densified balsam fir wood in the radial-tangential plane using a digital image correlation (DIC) method

Thermo-hydro-mechanical densified balsam fir (Abies balsamea (L.) Mill.) wood used in this study was made by compressing wood in the radial (R) direction (ray direction) at a temperature of 230 °C and a compression ratio of 60 % for 20 min, which significantly increased its density and some mechanical properties. However, the elastic parameters of densified wood in the R and tangential (T) directions, [moduli of elasticity (E R and E T), shear modulus (G RT), and Poisson’s ratios (μ RT and μ TR)], have seldom been reported because of the relatively small thickness of a densified wood specimen. This study measured the E R, E T, G RT, μ RT, and μ TR of densified balsam fir wood using a digital image correlation method, which was used to measure the strain field of a specimen under compressive loading. The corresponding five elastic parameters of undensified balsam fir wood were also measured. The experimental results were: (1) E R was 284 MPa, which was about 66 % lower than that of undensified fir; (2) E T was 2551 MPa, which was about ten times larger than that of undensified fir; (3) G RT was 21 MPa, which was about 50 % lower than that of undensified fir; and (4) μ RT and μ TR were 0.104 and 0.331, which were about 75 and 10 % lower than those of undensified fir, respectively.