Static Bending Properties of Structural Wood-Base Panels: Large-Panel Versus Small-Specimen Tests

The use of small-specimen bending tests on some particle panel products may be inappropriate because the relative size of the specimen and wood elements in the panel (wafers, flakes, strands) can result in unnecessarily large variability in test values. In this study, eight different structural panel products were tested in static bending using quarter-point loading of four different test panel sizes. The goal was to assess the effect of panel size on bending strength and variability of test values. Products tested included veneered composite panels, oriented strandboard, waferboards, and flakeboards. For comparison, tests were made on 3-inch-wide midspan-loaded specimens specified in ASTM D 1037. Bending strengths (MOR) and stiffnesses (MOE) were essentially the same for all sizes of quarter-point-loaded test panels for each of the eight products. MOE from ASTM-size specimens was somewhat lower, whereas MOR was somewhat higher than corresponding values from the other test panels. Variability of test results generally increased as test panel size decreased. Strength characteristics of sheathing-grade face veneers were overriding factors in variability of composite panels. The study results suggest that large-panel bending tests should be used when developing design stresses for some structural-use panels.

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