超高分子量聚乙烯纤维/环氧复合材料的吸湿行为及吸湿应力分析

为了揭示超高分子量聚乙烯(UHMWPE)纤维增强环氧树脂基复合材料的吸湿机制,利用ABAQUS有限元软件,建立二维模型,对此类复合材料的吸湿行为及吸湿应力进行研究。模拟计算了两种不同纤维分布模型内部的水分浓度场分布; 根据获得的水分浓度场,对两种模型随温度及时间变化的吸湿应力场进行了分析。结果表明: 水分在两种模型中的扩散都符合Fick扩散定律,纤维按正六边形分布模型比纤维随机分布模型更早达到吸湿平衡,但后者更符合实际情况,也与实验结果比较吻合; 长时间的吸湿会导致材料内部吸湿应力达到很高的水平(>60 MPa),温度越高,越早达到吸湿平衡,应力越大,最大的吸湿应力出现在纤维聚集最密集的基体区域,纤维随机分布模型的吸湿应力水平高于纤维按正六边形分布模型。

Analysis of hygroscopic behavior and moisture-induced stress in ultra-high molecular weight polyethylene fiber/epoxy composites

In order to reveal the moisture absorption mechanism of ultra-high molecular weight polyethylene (UHMWPE) fiber-reinforced epoxy composites, the two-dimensional finite element models were established by using ABAQUS, and the hygroscopic behavior and moisture-induced stress in the composites were studied. The moisture concentration fields in two models with different fiber distributions and environment temperatures were calculated, and then the moisture-induced stresses were analyzed on the basis of the first step. The results show that the moisture absorption processes of the two models all are in agreement with Fick’s diffusion law, the saturation time of moisture absorption of the model with hexagonally distributed fibers is less than that of the model with randomly distributed fibers, but the latter is more coincidental with practical situation and fitted well with the experimental data. The stress within the materials induced by long time moisture absorption can reach to a higher level (above 60 MPa), the higher the temperature, the more early the moisture absorption balance, the greater the stress, and the maximal value appears in the matrix region where fiber aggregation state is most crowded. The stress level of the model with randomly distributed fibers is obviously higher than that of the model with hexagonally distributed fibers.