An optical method for rapid examination of check development in decorative plywood panels

Common methods for assessment of surface checking in decorative plywood panels rely on manual handling and visual inspection of specimens, a laborious procedure practically limiting the number of materials and variables that may be considered within one project. In this study, a new automated optical method for detection and measurement of checks has been developed. This method was based on the digital image correlation principle, which allowed identification of checks as small as 0.2 mm wide and 1 mm long. Continuous measurement allowed reliable check counts, and measurement of check dimensions as they develop during exposure to drying conditions. A check severity index has been proposed. The method has been validated in exposure tests conducted in harsh but realistic conditions, to increase the likelihood of checking and reduce the test duration to 4 h. In addition, an innovative test setup allowed near simultaneous monitoring of check development in up to 48 panel specimens sized 30 × 30 cm. The efficiency of the method allows studies to examine an unprecedented number of treatments and replicates.