梯度含水状态对木材物理力学性能的影响研究毕业（设计）论文.docxVIP

大学本科毕业（设计）论文 （2013届) 题 目： 梯度含水状态 对木质材料物理力学性能影响的研究 教学院系： 材料工程学院 专 业： 木材科学与工程 梯度含水状态对木质材料物理力学性能影响的研究 （西南林业大学材料工程学院 昆明 650224） 摘 要：为考查环境湿度对木质材料物理力学性能的影响，本文以云南松（YunNan Pine,拉丁名Pinus Yunnanensis，简称：YPSW）、意杨（拉丁文：Populus euramevicana，简称：PSW）和意杨酚醛树脂单板层积材（PF-P-LVL）为研究对象，通过测试和分析不同含水状态下试材的外形尺寸、质量和静曲弹性模量（MOE），得如下结论：1）在吸湿过程中三种材料的厚度、宽度膨胀与名义含水率（Nominal moisture content,简称：NMC）增长成正相关关系，但膨胀率则相反；2）相同NMC下，三种材料梯度含水状态下的MOE均小于平衡含水状态下材料的MOE，但随材料水分梯度的减小，两者的差异也逐渐变小；3）尺寸膨胀对三种材料MOE的影响依次为P-PF-LVL＞YNP＞PSW，说明热压型人造板材料在吸湿过程中不但发生了原材料的尺寸膨胀，也发生了热压压缩的回复。 建议我国相关标准关注环境湿度变化引发的木质材料由于含水不均而导致的力学性能降低问题。 关键词：平衡含水状态,梯度含水状态,尺寸变化,弹性模量 Study on the Physical and Mechanical Properties influence from Gradient Moisture Content （Faculty of Material Engineering，Southwest Forestry University,Kunming,650224） Abstract: In order to investigate the effects of environmental moisture on physical-mechanical properties of wood materials, the dimension, mass and modulus of elasticity (MOE) of YNP, PSW and PF-P-LVL under different moisture content distribution were measured and analyzed. Final results showed: 1) the width and thickness swelling of three materials were all positive with their Nominal moisture content (NMC), but the swelling ratios were contrary to NMC; 2) MOEs of three materials under moisture content gradient distribution (GMC) were all lower than they under equilibrium moisture distribution (EMC), but this difference was getting smaller and smaller with the GMC decreased;3) the ranges of effects of dimensions on MOEs were P-PF-LVL＞YNP＞PSW, this indicated that hot-pressing material not only occurred dimensional swelling caused by moisture absorption, but also occurred dimensional recovery caused hot-pressing. Meanwhile, this paper suggested that such effects on mechanical properties caused by GMC should be pay attention to in Chinese relative standards or specifications. Keywords：equilibrium moisture content, gradient moisture content, dimensional changes, modulus of elast