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

理论上，泊松比为负值的材料(即伸展材料)与泊松比为正值且杨氏模数相同的材料相比，具有更高的硬度、抗冲击性、断裂韧性和剪切模数。已经报道了随机纤维结构中伸展行为的实验证据，但这类伸展材料在很大程度上仍未被探索。在这里，我们将用数值和实验的方法研究纤维增强复合材料的设计和开发的另一条途径。中心假设是，可以通过在传统的基质材料中嵌入伸展纤维网络来制造伸展复合材料。这一假设的正确性将在该项目的实验部分通过复合材料试件的制造和力学测试来考察。主要的建模目标是开发一个数值网络模型，从而可以彻底地研究随机纤维网络材料的拉伸行为。智力上的优点在于，通过探索替代路线来设计伸展材料将带来好处。该数值模型将是营养学领域的一个有价值的工具，并将是设计和开发新的复合材料的关键，该复合材料的杨氏模数和泊松比都是最优的。面向代表不足群体的K-12学生的外联活动将有助于通过提高对工程学的认识和兴趣来扩大该项目的影响，并使学生有机会通过校园访问、演讲和辅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.