纳米颗粒和连续纤维对微纳米多相复合材料压缩性能的协同增强机理研究

Multi-scale phase reinforced polymer composites (MPRCs) tailored with nano-scale fillers, micro-scale fibers and polymer matrix have shown great potential as engineering materials. This type of materials can provide the opportunity for fabrication of advanced composites by combining innovative nanotechnology with conventional fiber reinforced composites (FRPs), leading to further improved mechanical performance as compared to conventional FRPs and nanocomposites. Unfortunately, there still remains ambiguous understanding on the synergistic reinforcing effect introduced by the multi-scale phases so far, which limits the current research and development of MPRCs...The proposed project aims to investigate the synergistic reinforcing effect of nanoparticles and continuous fibers on the compressive performance of MPRCs, through systematical experimental and theoretical studies. The research will be focused on two issues:..(1) The mechanical behaviors and failure mechanisms of MPRCs when subjected to quasi-static and dynamic compression. Through comprehensive experimental study combining standard mechanical tests and meso-scale tests using fiber bundles, the work aims to elaborate the roles that multiple phases play respectively in the improvement of compressive performance of MPRCs...(2) The synergistic effect of nanoparticles and fibers on reinforced compressive properties of MPRCs. This part of work will elucidate how the incorporated nanoparticles interact with continuous fibers, and contribute to the enhanced polymer matrix and fiber/matrix interface, which result in the improvement in ultimate compressive performance of the composites. A multi-scale model bridging micro-scale material structures, meso-scale failure mechanisms and macro-scale mechanical properties of MPRCs will be established...This project will provide new insights into the fundamental reinforcing mechanisms caused by the incorporation of nanoparticles as well as their influence on the mechanical behaviors of MPRCs. The knowledge gained is essential for the design and development of MPRCs, and for full exploitation of their potential in high performance applications.

微纳米多相复合材料是整合新颖的纳米技术与传统的纤维增强技术，具有比常规两相纳米复合材料和纤维增强复合材料更加优异力学性能的先进工程材料。其中，纳米颗粒和微米级纤维作为多尺度的增强相，综合影响复合材料的力学性质。目前对多相增强的内在机制尚缺乏清晰认识。本项目针对该问题，重点就纳米颗粒和连续纤维在增强高聚物复合材料压缩性能中的协同作用，开展系统的实验研究和定量化的理论分析。（1）结合复合材料宏观动静态压缩实验和纤维束细观力学实验技术，研究多相复合材料的压缩行为和破坏机制，揭示各增强相在复合材料压缩中的增强机理；（2）分析纳米颗粒的引入对复合材料中纤维/基体界面力学性质的影响和微纳米增强相的协同增强机制，研究建立包含微观结构参数和细观破坏机制的复合材料宏观力学性能的理论模型。本项目能促进对微纳米多相复合材料力学行为的深入理解，指导该新型材料的设计制备和性能预测，充分发掘其作为先进工程材料的潜力。

本项目针对SiO2纳米颗粒和连续碳纤维增强的微纳米多相复合材料的压缩性能进行了系统的研究，探讨了协同增强机制，并在相关的实验技术方面开展了一系列研究，具体内容及取得的成果如下：.1).以均匀分散有SiO2纳米颗粒的环氧树脂为基体，T700碳纤维布为微米尺度增强相，通过真空辅助树脂传递模塑工艺制备了单向纤维复合材料层合板，利用偏轴压缩实验评估了其轴向压缩的强度。发现引入5 wt%SiO2纳米颗粒形成的微纳米多相复合材料的压缩强度，相比传统的碳纤维增强复合材料提高了约25%。对试样的显微表征表明，单向纤维复合材料的压缩失效主要表现为剪切型微屈曲。基于微屈曲失效机制，建立了微纳米多相复合材料的压缩强度模型，该模型反映了纳米颗粒对基体弹塑性力学性质的改变如何影响微纳米复合材料的宏观压缩性质。模型预测结果与实验结果达到良好的一致。.2).参照复合材料层合板的横向拉伸和面内剪切国际测试标准(ISO 527和ASTM 5379)，发展了纤维束复合材料测试技术，该技术可用于评估单向纤维层合板的层间界面性能。纤维束复合材料测试技术相比传统的单纤维测试方法，能够避免较大的随机误差，评估纤维束和树脂基体之间的宏观粘接强度，而相对于工程中常用的层合板测试方法，则具备制样简单，破坏区域可控等优点。通过对比和分析，建立了纤维束复合材料测试结果与单向纤维层合板测试结果的定量关系。利用该关系，可根据纤维束复合材料的强度，估算层合板层间界面在正应力和剪应力作用下的强度。利用该技术，评估了微纳米多相复合材料的层间界面性能，结果表明，将SiO2纳米颗粒引入树脂基体之后，纤维和基体间的宏观粘接强度得到显著提高。.3).由于对纤维束和基体界面区域变形场的观测和分析需求，对数字图像相关方法(DIC)开展了研究。提出了路径无关的DIC方法，该方法适用于分析间断变形场，可有效避免非连续变形区域的测量误差影响其相邻区域的变形测量。同时利用路径无关的DIC方法的特点，开发了基于GPU的并行DIC方法，在保持高精度的前提下，将目前的DIC计算速度提高近两个数量级。该方法在普通个人电脑上的计算速度可高达每秒16万点，是迄今为止文献报道的最高纪录。