Material Processing and Mechanical Behavior of High-Performance Cellulose Nanopaper Made From Cellulose Nanofibrils

这笔拨款将用于研究开发由纤维素纳米原纤维自组装制成的用于结构应用的纤维素“纳米纸”。具有轻质特性的坚固、坚硬和坚韧的材料对于从汽车到航空工业的许多工程应用至关重要，以减少能源消耗并提高结构灵活性等。本研究旨在通过使用木质纤维素生物质衍生的纤维素纳米纤维作为石油基资源的替代品，创造传统化石燃料衍生聚合物和聚合物复合材料的绿色替代品。通过非接触、基于视觉的方法，在绿色材料加工、新型纳米结构材料的力学表征和建模领域，教育和培训来自不同和代表性不足群体的学生是总体研究目标的一部分。将研究成果纳入研究生课程，通过演示、演讲、出版物和其他外展活动向同行和广大社区传播研究结果，也是研究项目不可或缺的一部分。纤维素纳米原纤维所具有的高纵横比和半结晶纳米结构使其成为形成三维纠缠微观网络的理想材料，适合于通过自组装加工高性能结构材料。由此产生的材料通常被称为纤维素纳米纸，具有很好的机械特性。本基础研究是纤维素纳米纸在“现状”和功能化状态下的材料加工和机械行为的界面，旨在破译这种非传统和潜在的高性能机械应用变革材料的工艺-微观结构-性能关系。在材料加工方面，重点将放在(a)研究与环境友好型甲酸水解相关的反应条件和纤维素纳米纤维特性的机械纤颤参数，(b)研究不同的加工方法来控制所得到的纳米纸的质量、微观结构和功能。在力学表征方面，重点将放在(a)发展基于力学的对不同微观结构和功能的纤维纤维素纳米纸在不同长度尺度和加载速率下的拉伸和断裂响应的理解，(b)开发和展示单片和层压高性能纤维素纳米纸结构。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This grant will enable research on developing cellulose ‘nanopaper’ made by self-assembly of cellulose nanofibrils for structural applications. Strong, stiff and tough materials with lightweight characteristics are critical for many engineering applications ranging from automotive to aviation industries to reduce energy consumption and increase structural agility, among others. This research aims to create green alternatives to traditional fossil fuel derived polymers and polymer composites by employing cellulose nanofibrils derived from lignocellulosic biomass as an alternative to petroleum-based resources. Educating and training students from diverse and underrepresented groups in areas of processing of green materials and mechanical characterization and modeling of novel nanostructured materials via non-contact, vision-based approaches is part of the overall research goal. Incorporating the research outcomes into the graduate curriculum, disseminating the findings to peers and the community at-large through demonstrations, presentations, publications and other outreach activities is integral to the research project as well. The high aspect ratio and semi-crystalline nanostructure that cellulose nanofibrils possess make them ideal to form three-dimensionally entangled microscopic networks suitable for processing high-performance structural materials via self-assembly. The resulting material is often referred to as cellulose nanopaper and has promising mechanical characteristics. This basic research, at the interface of material processing and mechanical behavior of cellulose nanopaper in ‘as-is’ and functionalized states, is to decipher process-microstructure-property relations for this non-traditional and potentially transformative material for high performance mechanical applications. On the material processing front, the focus will be on (a) studying the reaction conditions associated with the environmentally-friendly formic acid hydrolysis and mechanical fibrillation parameters on the cellulose nanofibril characteristics, (b) investigating different processing approaches to control the resulting nanopaper quality, microstructure and functionality. On the mechanical characterization front, the focus will be on (a) developing mechanics-based understanding of the tensile and fracture responses of fibrous cellulose nanopaper of different microstructures and functionalities at different length scales and loading rates, (b) developing and demonstrating monolithic and laminated high-performance cellulose nanopaper structures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.