Bending Capacity of Middle Joints of Upholstered Furniture Frames
This study evaluates the edgewise bending moment capacity of the four most frequently used middle joints in the upholstered furniture frames. The research included the following joints: Mortise and Tenon, double Dowel, Corner Blocks and double Gusset Plates, designed in the form of middle joints and made of beech and poplar solid wood. The test results indicated that regarding the edgewise bending force, the strongest middle joint was the double dowel joint made of beech wood (1896.9 N), while the respective joint made of poplar marked quite a low value of bending force (937.2 N). The strength of wooden corner blocks was proved to be quite powerful, made either of beech wood, poplar wood or the combination of the two wood species (beech: 1881.8 N, poplar: 1237.6 N, beech-poplar: 1783.6 N). The gusset plate joint made of beech resulted in weaker values (1378.2 N), compared to the dowel and corner block joints made of beech, whereas the same joint made of poplar demonstrated very satisfying values of edgewise bending force (1471.8 N). Finally, the mortise and tenon joint appeared to have the lowest strength, both in the case of beech (1306 N) and poplar (634 N). The highest coeffi cient of elasticity (CE) derived from double gusset plate joint, made of beech. All the joints showed good elasticity, except the mortise and tenon joint made of poplar, as well as, the dowel joint made of poplar, which recorded the lowest elasticity values of all. Generally, beech wood resulted in stronger and more elastic joints compared to poplar.
Shear force and bending moment capacities of joints constructed with glued corner blocks
Tests were carried out to determine the ultimate shear and bending moment capacities of glued corner blocks under controlled laboratory conditions. Yellow-poplar and sweetgum were utilized in constructing the joint specimens, but all comer blocks were cut from yellow-poplar. The glue faces of the four different size blocks used in the tests measured 25 by 25 mm, 25 by 38 mm, 25 by 51 mm, and 25 by 64 mm so that the edges of the glue faces on the blocks measured 25, 38, 51, or 64 mm. Specimens were assembled with liquid animal hide glue. Specimens were tested under static load by applying either shear or bending forces. Both the average shear force and the average bending moment capacities of joints formed with various size comer blocks could be predicted by relatively simple exponential expressions.
Design and testing of bookcase frames constructed with round mortise and tenon joints
Previous work has shown that by using round mortise and tenon joints, durable maintenance-free school chairs and desks can be produced from largely waste local woody materials by cottage industries in remote regions of the world. Results of this previous work would suggest that by using this same method of construction, well-de- signed, durable, functional bookcases also could be produced from locally available small-diameter tree species and thin plywood or other thin panel materials. A number of panel and frame bookcases utilizing round mortise and tenon joints were constructed to evaluate their performance. Tests conducted on the resulting bookcase frames and shelves indicated that shelves constructed of thin plywood supported by small front and back shelf rails with ends joined to the corner posts with round mortise and tenon joints easily met critical shelf deflection criteria. The excellent deflection characteristics of the shelves were credited to the high degree of end fixity of the shelf rails that was ob- tained through the use of snug fitting round mortise and tenon joints.