Advanced Impact Resistant Auxetic Materials via Additive Manufacturing

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Auxetic materials, often referred to as "metamaterials" or "negative Poisson's ratio materials", are counter-intuitive in their response to deformation. Upon being stretched they will expand and conversely will contract when compressed. This behavior makes them very attractive for impact applications; upon being compressively loaded at high rates they will tend to supply increased resistance. As such there are several commercial auxetic products currently available, notably athletic footwear produced by the world's largest manufacturer. However, broader application of auxetic materials is only now garnering significant attention with the advent of additive manufacturing (AM). AM is a manufacturing method in which very complex geometries can be printed out of a wide variety of materials. Recently, AM has been applied to the manufacture of auxetics with the aim of leveraging the advantages of AM, namely the ability to print curved and graded materials. However, the current efforts have been limited to relatively small sizes and/or have not been experimentally tested at scale. A design tool is needed to bridge the technology gap between lab-scale AM auxetics and engineering auxetic commercially-ready products that have large sizes (on the order of tens of centimeters). The short-term objectives of the proposed work is to develop a validated design tool that can virtually simulate auxetic materials. This design tool is needed to accelerate the development of auxetic products for impact applications. The long-term objective is to harness the advantages of AM to address a well-known inequality in impact protective gear where female-specific athletics footwear and ballistic body armor are well-known needs. These needs are currently very sparsely filled due to the high manufacturing costs for sex-specific products. Through the use of the proposed design tool, this work aims to provide a technological means of accelerating the development of these needed footwear and armor products more realistic.