Standardised bending-class method for reclassification of flexural properties in general-purpose plywood

Plywood is a versatile wood-based panel commonly used in structural and furniture applications, where bending strength is a key performance criterion. This study proposed a standardised method for classifying general-purpose plywood into distinct Bending Classes (e.g. Class 10, 20, 30) based on mechanical performance rather than grain direction. In Indian plywood, which often uses plantation timber cores and thin face veneers, conventional direction-based testing can misrepresent actual strength, especially when cross-grain performance exceeds with-grain values. To improve reliability, the proposed method evaluates four mechanical parameters: modulus of rupture (MoR) and modulus of elasticity (MoE), measured both along and across the grain directions, with values scaled by a factor of 1/100 for normalisation. The minimum of these values is then floored to the nearest lower multiple of 10 to assign a Bending Class. This conservative approach helps accommodate material variability, measurement uncertainty, and environmental effects, reducing the risk of overestimating performance. Testing across samples from various Indian manufacturers revealed that in 78% of cases, MOR along the grain was the weakest parameter. Strong correlations between strength and stiffness validate the model. By reflecting actual material behaviour, the method enhances safety, streamlines design, and facilitates global harmonisation through a consistent, performance-based framework.