Many forests of the United States have large areas that contain trees of small diameter, mixed species, and undefined quality. Because these areas are at risk from attack by insects, disease, and uncontrollable wild fires, it is essential to find ways to increase the incentive to harvest this small-diameter material. One way to do this is to develop cost-effective products for the fiber from these trees. Nondestructive technology needs to be developed to evaluate the potential quality of stems and logs obtained from trees in such ecosystems. Static bending, transverse vibration, and longitudinal stress wave techniques are frequently used to assess the modulus of elasticity (MOE) of lumber. Excellent correlations between MOE values obtained from these techniques have been reported. The objective of this study was to investigate the use of these techniques to evaluate the flexural stiffness and MOE of small-diameter logs. A total of 159 red pine and jack pine logs were obtained from northern Michigan and were assessed nondestructively using these techniques. Statistical comparisons between stiffness and MOE values obtained from each technique were then examined. Results of this study demonstrated that strong relationships exist between the log properties determined by the three techniques, longitudinal stress wave, transverse vibration, and static bending. Developed models allow for the prediction of static bending properties of logs at levels of accuracy previously considered unattainable. This indicates that any of these techniques can be used to sort small diameter logs with reasonable accuracy.

A cantilever-beam vibration-testing apparatus has been developed to provide a means of dynamic and non- destructive evaluation of modulus of elasticity for small samples of wood or wood-composite material. The apparatus applies a known displacement to a cantilever beam and then releases the beam into its natural first-mode vibration and records displacement as a function of time. That frequency and amplitude attenuation is then used to calculate the dynamic material properties of the cantilever beam. The dynamic testing is quick and calculates the dynamic modulus and loss-tangent damping coefficient.