In situ structural changes of voids in OSB in three-point bending test

Oriented strand board (OSB) is widely used in construction due to its cost-effectiveness and good mechanical performances. While the relationship between processing parameters and void formation has been extensively studied, the real-time behavior of voids during mechanical loading remains poorly understood. This study investigated the dynamic relationship between void characteristics and mechanical properties of OSB using digital image correlation (DIC) technology during the three-point bending tests on 15 mm and 18 mm thick commercial panels. Results showed that the initial void sizes in the core and face layers averaged 0.019 mm² and 0.017 mm² respectively, with voidage being significantly higher in the core layer than in the face layers. The size of voids hardly changes when the loading force is lower than 0.7 times of the maximum loading force. Shear strain analysis revealed that structural changes were more pronounced in and around voids compared to other regions, especially in the core layer along the major axis. Fracture initiation was primarily associated with individual voids in face layers and areas of high void concentration in the core layer. Notably, continuous and large fractures enhance the specimen’s load-bearing capacity, resulting in high MOE and MOR values. Non-continuous fractures in the core layer, however, have limited contribution to increasing MOE and MOR of the specimens.