Effect of the number of screws and screw size on moment capacity of furniture corner joints in case construction

Abstract

Tests were carried out in order to determine the bending moment capacity of L-type glued-screwed coner joints constructed with multiple screws. 6 sizes of screws were used for assembling the specimens. 2, 3, and 4 screws were used in the joints of the specimens that have the same width. Specimens were prepared of 18-mm-thick particleboard (PB) and medium density fiber-board (MDF) with resin surfacing. The specimens were constructed with both screws and polyurethane adhesive. Specimens were tested under static compression and tension loads. Results have shown that the maximum moment capacity is obtained with the MDF specimens when the number of screws in the joints is 4. In both compression and tension tests, MDF corner joints were stronger than PB corner joints. Results of the tests also indicated that a screw corner joint becomes stronger as either screw diameter or screw length is increased. Screw length was found to have a greater effect on moment capacity than diameter. Furthermore, the average moment capacities of glued-screwed corner joints evaluated in this study in compression could be predicted by means of the expressions: CMPB = -81.59 + 16.09 X + 14.52 Y + 1.47 Z CMMDF = -173.9 + 29.07 X + 24.62 Y + 2.26 Z and in tension by means of the expressions: TMPB = -8.4 + 17.73 X + 44.55 Y + 1.32 Z TMMDF = -136.1 + 32.42 X + 17.25 Y + 2.2 Z where CMPB, CMMDF = moment capacities of PB and MDF joints, respectively, under compression load (Nm); TMPB, TMMDF = moment capacities of PB and MDF joints, respectively, under tension load (Nm); X = number of screws; Y = screw diameter (mm); Z = screw penetration (mm).