Investigation on a method of increasing mortise and tenon joint strength of a fast growing wood

A new method of increasing the strength of mortise and tenon joint of fast growing wood was put forward in this paper. Poplar (Populus spp.) T-shaped specimen jointed by oval tenon was put as an example, and a harder wood beech (Fagus sylvatica) block was embedded in the mortise of poplar transverse component, then connected with vertical component by loose tenon. Firstly, the best fitting parameter between beech block and poplar transverse component was investigated by innovative measuring method. Then the best fitting parameter between poplar vertical component and loose tenon was also studied. Finally, holding the same size of components and the best fitting parameters, the influence of different grains of beach embedded in poplar on the withdrawal force of T-shaped specimens was argued, and compared with the poplar integral and beech integral mortise and tenon joined T-shaped specimens. The results showed that the withdrawal force of beech integral tenon joint (type Ⅳ joint) was 5 027 n, poplar loose tenon joint embedded with beech in longitude (type Ⅲ joint) was 4 242 n, poplar loose tenon joint embedded with beech in transverse (type Ⅱ joint) was 3 775 n, and the poplar integral tenon joint (type Ⅰ joint) was 3 123 n, respectively. In other words, the withdrawal force was type Ⅳ joint > type Ⅲ joint > type Ⅱ joint > type Ⅰ joint. Following conclusions can be drawn based on the results of experiment: the withdrawal force of type Ⅲ joint was 12.4% bigger than type Ⅱ joint, and suggested that the embedded direction influenced the strength of joint, and longitude embedded was more efficient. Besides, the type Ⅲ joint was 35.8% bigger than type Ⅰ joint, nearly 1 119 n, indicating that the method of embedding hard wood with longitude grain in fast growing wood joint was able to increase the withdrawal force of joint significantly, and then provide a new method for direct application of fast growing wood in solid wood mortise and tenon joint furniture.