Understanding the mechanical performance of OSB in compression tests

Oriented strand board (OSB) is an important engineered wood product manufactured through bonding of wooden strands in cross-oriented layers. The mechanical performance of OSB obviously strongly depends on its micro-structural characteristics. Therefore, to be able to understand the compressive strength (CS) of OSB in loading conditions, its micro-structure has to be characterized throughout compression. Microstructural changes were monitored with 4D CT, and mesoscale strain transformations with digital image correlation (DIC). Samples from two types of OSB panels are prepared. For each type, a first series of samples is compressed using a universal testing machine, while recording the strain distribution with DIC. A second series of samples is investigated with X-ray CT. With the latter, microscopic changes are dynamically resolved while under compression by a CT-purposed load cell. The results of the compression experiments in combination with DIC reveal a piecewise-linear relationship between CS and the displacement of the loading wedge. Strain was analyzed separately in five regions along sample thickness, namely top, transfer, central, transfer and bottom. During compression, strain mainly increases in central regions, and strain in transition regions show comparatively more variable behavior. Compression of the samples is partially due to the delamination of strands and strand failure resulting from shearing. The X-ray CT results show that cracks in strands are more prone to be compacted under compression than wood vessels and inter-strand voids. Finally, non-woody solid substances, e.g. glue, additives and mineral intrusions, can locally strengthen the wood-based structure. The findings of this work can contribute to manufacturing strategies aiming to improve the mechanical performance of OSB. (C) 2020 Elsevier Ltd. All rights reserved.