The plywood consumption in various applications is increasing, especially in construction. In service, plywood can be exposed to a range of outdoor conditions, sometimes at elevated temperatures. This requires an understanding of the structural behavior and knowledge of the effects of the elevated temperatures on the properties of plywood. Therefore, the objective of this research was to study the effect of exposure time on physical and mechanical properties of plywood at elevated temperatures. The plywood samples were tested after exposure to nine different temperatures (50 °C, 75 °C, 100 °C, 125 °C, 150 °C, 175 °C, 200 °C, 225 °C and 250 °C) and ten exposure time levels (0.5, 1, 1.5, 2, 2.5, 3, 6, 8, 10 and 12 h) at each temperature. Additionally, a set of control samples was tested at room temperature. The findings of this study indicated that exposure of plywood panels to elevated temperature caused significant degradation of their bending and bonding strengths, whereas the hydrophobicity of the panels improved. Three stages of plywood degradation could be distinguished. Below 175 °C, there is a slow decline in strength; the decisive change already occurs at 175 °C; but as temperature increases beyond 175 °C, a rapid decrease in strength is observed. Plywood samples lost 98.1% of their initial strength after 1.5 h of exposure at 250 °C, and lost 98.5% after 6 h of exposure at a temperature of 225 °C. Statistical regression-based models were also developed and evaluated for predicting the strength loss of plywood panels as a function of weight loss. As the weight losses of panels increased, the losses in bending and bonding strength increased too. The decrease in bending and bonding strength only becomes significant when the weight loss exceeds 5%. When the weight losses increased above 15%, plywood samples almost lost their strength.

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热处理对桦木胶合板某些物理和机械性能的影响

胶合板在各种应用中的消耗正在增加，特别是在建筑中。在使用中，胶合板可能会暴露在一定范围的室外条件下，有时甚至在高温下。这需要了解结构行为，并需要了解高温对胶合板性能的影响。因此，本研究的目的是研究暴露时间对高温下胶合板物理和机械性能的影响。胶合板样品在暴露于九种不同温度（50°C，75°C，100°C，125°C，150°C，175°C，200°C，225°C和250°C）和十个不同温度后进行测试每个温度下的暴露时间水平（0.5、1、1.5、2、2.5、3、6、8、10和12小时）。另外，在室温下测试一组对照样品。这项研究的结果表明，胶合板的暴露于高温下会导致其弯曲和粘结强度的显着降低，而胶合板的疏水性得到了改善。胶合板降解可以分为三个阶段。低于175°C，强度会缓慢下降。决定性的变化已经在175°C发生；但随着温度升高超过175°C，强度会迅速下降。胶合板样品在250°C下暴露1.5 h后失去其初始强度的98.1％，在225°C下暴露6 h后损失98.5％。还开发了基于统计回归的模型并进行了评估，以预测胶合板的强度损失与重量损失的关系。随着面板重量的减少，弯曲和粘结强度的损失也增加了。仅当重量损失超过5％时，弯曲和粘合强度的降低才变得显着。当重量损失增加到15％以上时，胶合板样品几乎失去了强度。