Direct withdrawal strength of single-staple joints in pine plywood

Effects of staple penetration depth, staple gage, ply grain orientation, and staple crown orientation on the direct withdrawal strength of single staples from the sides and ends of five-ply pine plywood were investigated. Experimental results indicated that staple withdrawal strength increased significantly as the depth of staple penetration increased from 1/2 to 1-1/4 inches at increments of 1/4 inch. Staple withdrawal strength was not affected by staple gages within the depth penetration range from 1/2 to 1 inch, but in the case of depth penetration of 1-1/4 inches, 15-gage staples had significantly higher withdrawal strength than 16-gage staples. Ply grain orientation had no effect on staple withdrawal strength from the plywood. Staple end withdrawal strength was affected by the staple crown orientation, but side withdrawal was not. Regression analysis of the data indicates a linear relationship exists between staple withdrawal strength and depth of staple penetration for staple gages 15 and 16 in five-ply pine plywood. The direct withdrawal strength of the single-staple joints could be predicted by means of a first-order multiple regression equation including depth of penetration, gage, and staple crown orientation.