含水率对不同密度竹基纤维复合材料热压传热的影响

Effect of Moisture Content on Heat Transfer during Hot-Pressing Process of Bamboo Scrimber with Different Densities

竹基纤维复合材料在热压过程中由于含水率的影响,其传热性能与力学性能均会产生较大差异。在热压过程中出现芯层温度急剧升高、蒸汽压力过大的“锅炉效应”,导致板材热压周期发生变化。本文探讨含水率对不同密度板坯热压传热和“锅炉效应”的影响,并建立不同密度时含水率对升温时间的数学模型。结果表明,由于“锅炉效应”的影响,在升温阶段,同一密度下,升温时间随含水率的提升而逐渐缩短;在保压阶段,最高温度和升温温度随着含水率的提高而升高;在降温阶段,密度为0.90 g/cm^(3)时,板材的降温时间随含水率的升高先增后减,密度为1.05 g/cm^(3)和1.20 g/cm^(3)时,降温时间随含水率的增加而降低。因此,在实际生产中,压制密度大于1.05 g/cm^(3)的板材时,建议含水率控制在15%左右。该研究为竹基纤维复合材料热压工艺提供了借鉴和参考。

Due to the influence of moisture content during hot pressing, the heat transfer and mechanical properties of bamboo scrimber will be different. During the hot pressing process, there will be a "boiler effect" that the core layer temperature raised sharply, leading to change in the hot pressing cycle of plates.The influence of moisture content on hot pressing heat transfer and "boiler effect" of slabs with different densities was investigated, and the mathematical model of temperature raised time with different moisture content and densities was established. The results showed that due to the influence of "boiler effect", under the same density, the heating time was gradually shortened with the increase of water content;In the pressure maintaining stage, the maximum temperature and temperature raised with the increase of water content. When the density was 0.90 g/cm^(3), the cooling time of the plate increased first,and then decreased with the increase of water content. When the density was 1.05 g/cm^(3) and 1.20 g/cm^(3),the cooling time decreased with the increase of water content. Therefore, in actual production, when pressing plates with a density greater than 1.05 g/cm^(3), it was recommended that the moisture content be controlled at about 15%. This study provided a reference for the hot pressing process of bamboo based fiber composites.