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

理论上，具有负泊松比的材料（即拉胀材料）具有比具有正泊松比和相同杨氏模量的材料改进的硬度、抗冲击性、断裂韧性和剪切模量。已经报道了随机纤维结构中的拉胀行为的实验证据，但是这类拉胀材料仍然在很大程度上处于探索之中。 在这里，拉胀纤维增强复合材料的设计和开发的替代路线将使用数值和实验方法进行研究。中心假设是，拉胀复合材料可以通过将拉胀纤维网络嵌入常规基质材料内来制造。 这一假设的有效性将在该项目的实验部分通过复合材料样品的制造和机械测试进行研究。 主要的建模目标是发展一个数值网络模型，从而可以彻底研究随机纤维网络材料的拉胀行为。 智力上的优点在于通过探索拉胀材料设计的替代路线所获得的好处。 数值模型将是一个有价值的工具，在该领域的auxetics和将是至关重要的设计和开发的新的复合材料，优化的杨氏模量和泊松比。 来自代表性不足群体的K-12学生的外联活动将有助于通过提高对工程的认识和兴趣来提供该项目的更广泛影响，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.