Toward Negative Poisson's Ratio Composites - Numerical and Experimental Study

理论上，具有负泊松比的材料（即auxetic材料）比具有正泊松比和相同杨氏模量的材料具有更高的硬度、抗冲击性、断裂韧性和剪切模量。在随机纤维结构中缺失行为的实验证据已被报道，但这类缺失材料仍在很大程度上有待探索。本文将采用数值方法和实验方法来研究增塑型纤维增强复合材料的设计和开发。该研究的中心假设是，通过在传统的基体材料中嵌入消蚀纤维网络，可以制造出消蚀复合材料。该假设的有效性将通过复合材料样品的制造和力学测试在项目的实验部分进行调查。主要的建模目标是建立一个数值网络模型，从而可以深入研究随机纤维网络材料的塑性行为。智力上的优点在于通过探索辅助材料设计的替代途径所获得的好处。该数值模型将成为增塑学领域的一个有价值的工具，对杨氏模量和泊松比优化的新型复合材料的设计和开发至关重要。对来自代表性不足群体的K-12学生的外展活动将通过提高对工程的认识和兴趣，为项目提供更广泛的影响，并使学生有机会通过校园参观、演讲和指导活动了解研究活动。

In theory a material with a negative Poisson's ratio (i.e. an auxetic material) has improved hardness, impact resistance, fracture toughness, and shear modulus over one with a positive Poisson's ratio and the same Young's modulus. Experimental evidence of auxetic behavior in random fibrous architectures has been reported, but this class of auxetic materials remains largely under explored. Here an alternate route to the design and development of auxetic fiber reinforced composites will be investigated using numerical and experimental methods. The central hypothesis is that an auxetic composite can be manufactured by embedding an auxetic fibrous network within a conventional matrix material. The validity of this hypothesis will be investigated in the experimental component of the project through the fabrication and mechanical testing of composite samples. The primary modeling objective is the development of a numerical network model whereby the auxetic behavior of random fibrous network materials can be thoroughly investigated. The intellectual merits lie in the benefits to be gained by exploring alternate routes to the design of auxetic materials. The numerical model will be a valuable tool in the field of auxetics and will be critical to the design and development of new composite materials which are optimized for both Young's modulus and Poisson ratio. The outreach activities to K-12 students from underrepresented groups will serve to provide a broader impact of the project through increased awareness and interest in engineering and give students the opportunity to learn about the research activities through campus visits, presentations and mentoring activities.