Effect of Moisture Content on the Mechanical Properties of Douglas-Fir Plywood in Rolling Shear

A randomly selected sample of 52,5-ply, 1/2-inch-thick commercial sheathing-grade Douglas-fir plywood panels was cut into a total of 400 6-inch by 18-inch rolling-shear specimens. These were grouped into four matching sets and conditioned to nominal moisture contents of 7 percent, 16 percent, 24 percent and soaked. All specimens were tested parallel to their face grain. Load-deformation curves to failure were recorded for each specimen. The effect of moisture content upon the mechanical properties in rolling shear was examined to provide realistic correction factors from laboratory test results, determined at 7 percent moisture content, to dry service conditions and from dry service conditions to wet service conditions. Weighted linear regression equations were found to provide the simplest and fairly accurate estimates of mechanical properties below the fiber-saturation point of 28 percent to 29 percent. To provide the most complete information for design engineers and code authorities, the linear equations were estimated for both the mean and 5 percent exclusion-limit values of ultimate stress and the mean values for modulus of rigidity.

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