Investigation of butt joint failure mode in sofa frame

PurposeThe purpose of this paper is to investigate the static behavior of different type of butt joints for application in a timber sofa furniture frame. In timber sofa structure, butt joints are commonly used between plywood and hardwood members but they are normally designed without any regard to the effect of grain directions of the wood members on the joint strength. The focus of the paper is to look at the effect of grain directions on the wooden member properties and on the strength of the butt joint in order to understand the failure mode to establish a more durable and effective sofa butt joint than the one normally used by the manufacturers.Design/methodology/approachExperiment tests are conducted to determine the mechanical properties of joint members, the maximum load‐carrying capacity of the butt joints, and the types of the failure in the joints in relation to different grain orientations under transverse loading conditions. Plywood and hardwood members are used in construction of the joint tests. Four types of butt joints are constructed with different condition of grain orientation, glue, and screw used in the joint members. The specimens are tested by fixing the plywood member and applying a transverse load to the hardwood member to simulate the conditions in the sofa frame.FindingsResult shows that butt joint with vertical grain orientation and joint with two screws and glue have the maximum load‐carrying capacity compared to the other three cases and compared to the current joint type used in the existing sofa frame design.Originality/valueThe paper is of value to furniture manufacturing industry, in which furniture members and joints are usually over‐designed without regard to grain orientations or applying sound engineering techniques.