Mechanical property loss and the occurrence of wood decay during experimental outdoor aging of wood based panels

Abstract

Small specimens of sheathing-grade oriented strandboard (OSB) and sheathing-grade plywood were evaluated for retention of mechanical properties in exterior exposure over a series of exposure times. In contrast to previous studies of this nature, specimens at prolonged exposure times were also evaluated (in something more than a cursory manner) for presence of decay. Specimen size and mounting configuration had been selected to maximize wetting and drying induced stress on adhesive bonds but discourage water retention and thus the likelihood of decay. Mechanical properties decreased progressively with exposure time, at a decreasing marginal rate, without a steady level ever being attained. All panel types included in this study became infested with decay fungi by 7 years of exposure, although infestation was clearly most severe in panels fabricated from aspen, and decay induced degradation evidently became more pronounced with progressive exposure time beyond 7 years. In this study, the assumption that test fence exposures can be designed to induce moisture cycling induced stresses on adhesive bonds while simultaneously excluding infestation by decay fungi proved to be erroneous. Infestation was apparently by decay fungi adapted to rapid fluctuations in moisture and temperature conditions, species that are not recognized as commonly causing decay of wood products.

Citation

Carll, Charles G.; Wiedenhoeft, Alex C. 2007. Mechanical property loss and the occurrence of wood decay during experimental outdoor aging of wood based panels. 41st International Wood Composites Symposium proceedings : March 26-28, 2007, Seattle, WA. [Pullman, Wash.] : Washington State University, 2007: 16 pages.