Abstract
To elucidate the mechanism of wood sandwich compression, the response of wood compressing yield stress to hygrothermal conditions was investigated in this study with respect to preheating temperature (30–210 °C) and moisture content (MC, 0–100 %). An associated functional model was developed to predict wood yield stress based on the measured MC and temperature in wood. A 1 % increase in wood MC or a 10 °C increase of temperature led to a decrease in wood yield stress exceeding 0.1 MPa. Significant variations in yield stress, exceeding 0.8 MPa, were observed between high MC layer(s) and the remaining layer(s) along the wood thickness when there was an MC variation over 5 %. Preheating the wood with by heating platens accelerated water/moisture migration in wood, resulting in relatively low yield stress in the wood interior areas where water/moisture had migrated. This study demonstrated that the comparatively low yield stress of some wood areas was responsible for sandwich compression. When mechanically compressed, only the wood layer(s) with lower yield stress was compressed, leading to sandwich compression, regardless of whether the mechanical force was applied tangentially or radially.
Funding source: National Natural Science Foundation of China
Award Identifier / Grant number: 31670557
Award Identifier / Grant number: 32071690
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Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
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Research funding: This research was funded by the National Natural Science Foundation of China (grant nos. 32071690 and 31670557).
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Conflicts of interests: The authors declare that they have no conflicts of interest regarding this article.
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