【作者】 许睿；

【导师】 沈珉；

【作者基本信息】 天津大学 ， 固体力学， 2012， 硕士

【摘要】 随机云杉短纤维增强聚丙烯热塑性复合材料因质轻、断裂韧性高,逐渐受到汽车、高速列车和大飞机内承力构件的青睐;现今对自然资源再利用、环境保护要求迫切,此种材料可降解、可循环使用、环境友好的性能,使得该材料的应用、研究价值较为突出。本文将弹塑性有限元方法与生成随机分布云杉纤维的程序相结合,考虑不同含量云杉短纤维的随机分布和随机方向等微结构特征,同时采用Cohesive Zone Model(CZM)描述界面相因素的影响,建立该复合材料二维拉伸数值模型,模拟了随机云杉短纤维增强聚丙烯热塑性复合材料的拉伸和循环加载行为。本文计算了纤维体积含量为10%、20%和49%的云杉/PP复合材料的整体拉伸真应力-真应变曲线,并确定了其CZM界面模型参数;与现有的七种复合材料有效弹性模量理论模型的预测结果和实验结果进行了比较,本文界面数值模型预测的材料整体刚度与实验结果吻合得最好。通过调控(CZM)界面模型Traction-Separation曲线参数,定量分析界面相强度、断裂能和界面牵引分离曲线形式对复合材料整体强度的影响,分析结果能够较好地用界面强度解释随纤维含量提高材料整体强度降低的实验现象。在此基础之上,本文预测了纤维含量为30%的材料的拉伸行为和剑麻增强聚丙烯复合材料的拉伸行为的结果。采用本文CZM界面拉伸有限元模型,预测了随机云杉短纤维增强聚丙烯热塑性复合材料拉伸卸载和重新加载、拉压循环应变载荷下的应力应变曲线,并给出了材料某局部区域云杉纤维与聚丙烯基体界面牵引分离曲线随总体载荷变化的响应,定量讨论了界面参数和界面断裂能对拉伸卸载和重新加载、拉压循环应变载荷下材料力学行为的影响。研究表明,本文CZM界面数值模型,能够定量描述随机云杉短纤维增强聚丙烯热塑性复合材料不同纤维含量随机微结构、纤维/基体界面性能等因素对材料整体拉伸、卸载和重新加载以及循环载荷下力学行为的影响;本文对随机纤维含量、微结构特征和纤维/基体界面性能影响的定量分析,有助于增加人们对随机短纤维复合材料界面载荷传递规律的理解,研究对定量调控随机短纤维微结构界面力学性能、对该类复合材料整体刚度、强度的优化设计具有重要的理论意义和指导作用。更多还原

【Abstract】 Because of light-weighted, high fracture toughness of Random Spruce Short Fiber reinforced polypropylene composites; they are preferred by automotive, high-speed trains and aircraft for load-bearing component increasingly. Owing to the urgent demand of the re-use of natural resources and environmental protection,the recycled, environmentally friendly properties of the biodegradable material make the application and research value of the materials become more prominent.Elastic-plastic finite element method and the random distribution of spruce fiber element program in common code are combined for this simulation, and simulated the tensile behavior of this composites in ABAQUS numerically, with the consideration of the interphase factor, by using the CZM. The tensile behavior and the cyclic loading behavior were simulated with this 2D tensile numerical model.The 10%, 20%and 49% volume content are simulated in terms of the true stress-strain curve, the parameters of the CZM were determined. The result from the CZM tensile model had been compared with the experiment result correctly. The interphase fracture energy, strength and the form of the traction-separation law were analyzed quantitatively through the parameter of the CZM. The result proved the experimental phenomenon that the interphse strength was decreasing with the increasing in fiber content. On basis of the conclusion, the tensile behavior of this material with the 30% fiber content is predicted and the sisal fiber reinforced PP composite has been compared with the experiment result through this CZM model.The CZM interphase tensile FEM predicted the true stress-strain curve for the tensile-unload and the reload, the cyclical strain and compressive load of the composite. The local CZM response for the Traction-Separation was changed with the overall load changing. The CZM parameters and the interphase fracture energy were discussed under the tensile-unload and the reload, the cyclical strain and compressive load of the composite quantitatively.The research showed that the CZM interphase model could quantitatively represent the influence of the different fiber volume content, random microstructure, and the interphase for the tensile-unload and the reload, the cyclical strain and compressive load of the composite. The quantitative analysis could help to understand the mechanism which the interface transfers the stress between fiber/PP. Also, it must have been guiding significance for the research on the quantitatively controlling random short fiber microstructure and interface mechanical performance, the global stiffness of composite material, the optimal design for the strength更多还原