A Study On Mechanical Properties Of Larch With Finger-Joint

The important mechanical properties of Larch with finger joint were studied in this research. Firstly in order to know well the anisotropism of Larch , twelve elastic constants were measured by electrical strain gauges. The result showed that the elastic constants of Larch were accurate and reliable.Then, based on the idea that the strength would be improved once the tips were dispersed on different sections ,the bending strength ,tensile strength and MOE were measured for the samples with different kinds of finger joint .According to the analysis of variance, slope and joint gap before glued were remarkable factors that affected the mechanical properties. The results showed that slant finger joint was better than straight one, bigger gap before glued was better than smaller one. At the same time, the special phenomena that static MOE of Larch with finger joint was higher than solid Larch was noticed.It showed that Larch with finger joint probably has better resistance for deformation than solid Larch in long-term load. But dynamic MOE of Larch with finger joint was lower than solid Larch measured by transverse resonant method .Finally, the author gave consideration on the joint .The displacement field of finger joint was got by DSCM. The tensile test showed that obvious inconsistency existed in joint area. The inconsistency was bigger in the base o f joint than other places and near joint area was bigger than the area far from the joint. This experiment gave very good explanation to some destroyed style for finger joint lumber.