Abstract

Auxetic materials are not natural. No known biological examples exist. The first auxetics were foams with specifically engineered microstructures. Depending on the size of the air gaps in the microstructure, the auxetic effect in these materials can be more or less extreme. Most auxetic foams expand by a factor of about 30% or so before shredding due to the stretching force. With more advanced auxetics, structured on the molecular level, more impressive expansion may be possible. Auxetic materials are interesting both because of their novel behavior and because of enhancements in other material properties that are related to Poissons ratio. This paper deals with auxetic material and their applications in textile fields.

Introduction

Materials can be divided into two basic categories: structural or functional. Development of structural materials is focused on improving their mechanical or physical properties, often with a saving in weight or cost. By contrast, functional materials are designed to detect and/or respond to events or stimuli that occur during their lifetime. These materials often display novel and counterintuitive behavior. Examples include electrically (semi) conducting polymers, materials that contract when heated, and those that expand when subjected to hydrostatic pressure. Another example is a remarkable class of materials known as auxetic materials. When stretched lengthways, these materials get fatter rather than thinner.

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The authors are Assistant Professors in the Department of Textile Technology at PSG College of Technology, Coimbatore.