Predicting modulus of rupture of solid and finger-jointed tropical African hardwoods using longitudinal vibration

The longitudinal vibration technique was examined as a means of evaluating the modulus of elasticity (MOE) and predicting the modulus of rupture (MOR) of solid and finger-jointed lumber from three tropical African hardwoods, Obeche (Triplochiton scleroxylon), Makore (Tieghemella heckelii), and Moabi (Baillonella toxisperma). Dynamic MOE was well correlated to static bending MOE for solid and finger-jointed lumber from the three tropical African hardwoods. Correlation coefficients of 0.94 and 0.90 obtained for the regression of dynamic MOE on MOR for solid and finger-jointed lumber, respectively, were comparable to those of 0.95 and 0.91 between static MOE and MOR for solid and finger-jointed lumber, respectively. Regression models developed for the regression of dynamic MOE on MOR for both solid and finger-jointed lumber were statistically highly significant (a= 0.05). The lower 5 percent exclusion limit lines derived seemed useful for predicting the MOR of solid and finger-jointed lumber from the three hardwoods. Although the static bending test is generally recognized as a more desirable method of determining MOR, the results indicated that the longitudinal vibration technique may also be useful as a nondestructive technique for predicting MOR of solid and finger-jointed tropical African hardwoods. The technique seems more applicable in situations where static bending testing is not feasible to undertake.