Predicting tensile properties of finger-jointed tropical African hardwoods using longitudinal vibration method.

The longitudinal vibration technique was examined as a meansof predicting ultimate tensile strenght and tension modules of elasticity of finger-jointed tropical African hardwoods using three different finger profiles. Modulus of elasticity measured using the longitudinal vibration technique ( i.e. dynamic MOE) was significantly correlated to static tension modulus of elasticity (i.e. tension MOE) for 10, 18, and 20mm long finger profiles studied for Obeche (Triplochiton scleroxylon), Makore (Tieghemella heckelii) and Moabi (Baillonella toxisperma). Dynamic MOE was also significantly correlated to tension MOE for the combined data for each species, and for the three species. High correlation coefficient of r = 0.89 was obtained for the regression of the combined data for the three species, and the regression model derived was also highly significant (alpha < 0.001). Correlation between dynamic MOE and ultimate tensile strenght was, generally, higher than that between tension MOE and ultimate tensile strenght, for all the finger profiles studied for the three species. Correlation coefficient obtained for the combined data for the 18mm finger profile of the three species (r =0.69) was high, and the regression model derived highly significant (alpha < 0.001). The lower 5% exclusion limit line derived for the regressions of dynamic MOE as a function of tension MOE and tensile strenght may be useful for predicting the static tensile properties of the three tropical hardwoods. Within the limits of the study, the longitudinal vibration technique, which is easier than the static test may be useful as a non-destructive method for accurately predicting tensile properties of finger-jointed tropical African hardwoods.