Comparison of moisture-dependent orthotropic Young’s moduli of Chinese fir wood determined by ultrasonic wave method and static compression or tension tests

Wood with distinctively different properties in the longitudinal, radial and tangential directions exhibits a strong moisture-dependent material characteristic in the elastic range. The purpose of this study was to analyze the orthotropic elastic properties of Chinese fir wood [Cunninghamia lanceolata (Lamb.) Hook] determined at different moisture conditions using an ultrasonic wave propagation method. The results were compared with those obtained by the traditional static compression or tension tests. The results confirm that the stiffness coefficients obtained by the ultrasound without considering the complete stiffness matrix show significantly higher values than the compression or tension Young’s moduli in all the three anatomical directions at each specific MC. The differences between stiffness coefficients and Young’s moduli were significantly reduced by corrections with Poisson ratio. Only in tangential direction, the Young’s moduli with Poisson ratio correction are statistically equivalent to the Young’s moduli obtained by compression and tension.