Mechanics of Multi-functional Biocomposites

该奖项的目标是制造高度耐用和多功能的天然纤维复合材料。纤维增强聚合物复合材料是将聚合物与强增强纤维结合在一起制成的。玻璃纤维和碳纤维都是相对昂贵的人造纤维。然而，天然纤维资源丰富，可回收利用，价格低廉。在汽车、建筑、体育用品和电子产品等几个商业应用中使用天然纤维增强复合材料的趋势越来越大。尽管天然纤维复合材料已被用于多种工业应用，但由于其耐久性和力学性能(如刚性、强度、裂纹萌生和抗扩展性能)较差，其在承载应用中的应用非常有限。通过在天然纤维上涂覆石墨烯并在层板之间嵌入短碳纤维，将实现刚性、强度、抗裂性和损伤传感等多功能性能。此外，还将利用嵌入的石墨烯和短碳纤维单元产生的三维导电网络来了解天然复合材料在不同机械载荷下的损伤演化。该项目将为研究生和本科生提供将石墨烯嵌入天然纤维、复合材料制造和多尺度机电表征的培训机会。研究活动还将通过在当地公立高中的推广，促进在尖端科学技术方面招收和指导未被充分代表的学生。将进行一项全面的实验研究，以调查多功能天然纤维增强复合材料在不同长度尺度上的损伤演化。为了实现这一目标，将在准静态机械载荷条件下进行包含三维导电网络的机电响应的新颖而具有挑战性的实验。将石墨烯沿面内方向嵌入天然纤维层压板中，并沿着层压板之间的厚度方向聚集短碳纤维，将产生高灵敏度的导电网络。假设产生的导电网络在机械载荷作用下会发生变化，以反映损伤机制，如纤维从层合板上拉出、基体开裂、层合板之间的分层和裂纹桥联。除了宏观实验外，还将使用嵌入导电模式原子力显微镜的微拉伸测试仪进行纳米级实验，以捕捉拉伸和剪切加载条件下电流分布的变化。

The objective of this award is to fabricate natural fiber composites that are highly durable and multi-functional. Fiber-reinforced polymer composites are made by combining a polymer together with strong reinforcing fibers. Both glass and carbon fibers are relatively expensive, man-made fibers. However natural fibers are abundant, recyclable and cheap. There is a growing trend to use natural fiber reinforced composites in several commercial applications such as automobiles, building construction, sporting goods, and electronic goods. Although natural fiber composites are already used in several industrial applications, their use in load bearing applications is very limited due to their poor durability and mechanical properties such as stiffness, strength, crack initiation and propagation resistance. Multi-functional properties such as stiffness, strength and crack resistance, and damage sensing will be achieved by coating natural fibers with graphene and embedding short carbon fibers between the laminates. In addition, research will be performed to understand the damage evolution of the natural composites under various mechanical loads using the three-dimensional electrical conductive network generated by the embedded graphene and short carbon fiber elements. This project will provide training opportunities to graduate and undergraduate students on embedding graphene into natural fibers, fabrication of composites, and multi-scale electro-mechanical characterization. The research activities will also promote the recruitment and mentoring of underrepresented students in cutting-edge scientific techniques through outreach in local public high schools.A comprehensive experimental study will be conducted to investigate damage evolution at different length scales in multi-functional natural fiber reinforced composites. To accomplish this objective, novel and challenging experiments incorporating the electro-mechanical response of three dimensional electrical conductive networks will be performed under quasi-static mechanical loading conditions. Highly sensitive conductive networks will be generated by embedding graphene in natural fibers laminates along in-plane directions, and by flocking short carbon fibers along the thickness direction between the laminates. It is hypothesized that the generated conductive network will undergo changes during mechanical loads to reflect damage mechanisms such as fiber pulling from the laminates, matrix cracking, delamination between laminates, and crack bridging. In addition to macro-scale experiments, nano-scale experiments will also be performed using a micro-tensile tester embedded, conductive mode atomic force microscope to capture change in current profile under tensile and shearing loading conditions.