Resonance and near infrared spectroscopy for evaluating dynamic wood properties

Abstract

Dynamic longitudinal (L) and transversal (T) tests based on wood resonance were performed on Eucalyptus specimens measuring 410 mm × 25 mm × 25 mm to obtain the dynamic elastic modulus (EL and ET), the first resonance frequency (f1L), the loss tangent (tan δT) and the specific modulus (E′L and E′T). Such dynamic traits and the air-dry density of wood were correlated by partial least squares (PLS) regressions to the near infrared (NIR) spectra measured in the central position of the longitudinal–radial surfaces. The statistics of the validation models for E, E′ and f1L ranged from 0.72 to 0.81 while the calibrations for loss tangent presented lower r2v (0.38), but promising RPD (ratio of performance to deviation) values (1.88). The key role of chemical wood components in the NIR-based calibrations for dynamic properties of wood is discussed. The association of the NIR spectroscopy and resonance techniques appears to be a rapid, low-cost and precise way to evaluate the visco-elastic properties of woods.