Comparative Properties of Douglas-Fir Boards Made from Parallel-Laminated Veneers vs. Solid Wood

Static bending and cleavage resistance of nominal 1-by 6-inch boards made from five and seven parallel plies of rotary-cut Douglas-fir veneer compared favorably with that of clear, vertical-grain, solid-sawn Douglas-fir lumber. The laminated material was laid up in the form of 4- by 8-foot panels, using the regular assembly procedure in a plywood plant. All plies were parallel rather than alternately cross-banded as in conventional plywood. Twenty parallel-laminated and 10 solid wood specimens 5-1/2 inches wide and 44 inches long were ripped from the panels and tested flatwise for static bending. Cleavage (splitting) tests were made on standard 2- by 3-3/4 inch notched blocks. Modulus of elasticity (MOE) of the laminated boards ranged from 2,112,033 to 2,247,774 psi, compared with 2,138,150 to 2,413,290 psi for the solid boards. Modulus of rupture (MOR) was 9,265 to 11,396 psi for the laminated material and 9,265 to 12,028 psi for the clear, solid wood. Cleavage tests showed maximum load at failure of 138 to 149 lbs. for the solid wood, compared with 48 to 83 lbs. for the parallel-laminated boards. Total cleavage failures occurred more gradually in the laminated specimens than in the solid wood, due to slight misalignment of grain in the plies. Some economic advantages that would help offset the comparatively higher cost of producing 1-inch parallel-laminated boards, in plywood plants are: a) Veneers are recovered from the best portions of logs with no loss from saw kerf; b) a consistently uniform product could be turned out, with higher appearance grade veneers used for face and back plies and the lower grades in the center layers; and c) the product would lend itself to continuous production, with longer lengths obtained through end-jointing the veneers and randomly spacing the joints within the product.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member