Development of novel auxetic structures from braided composite rods for structural applications

Auxetic materials are a class of materials that expand transversely when stretched longitudinally. Recently, auxetic materials are gaining special interest in technical sectors mainly due to their attractive mechanical behavior. This paper reports, for the first time, the development of auxetic structures from composite materials and the characterization of their auxetic as well as mechanical properties. The auxetic structures were developed by varying their geometry using core reinforced braided composite rods containing glass fibres for axial reinforcement, polyester filaments for braided structure and epoxy resin as matrix. The auxetic behavior of the structures was studied in a tensile testing machine using an image-based tracking method. The auxetic behavior and the tensile characteristics of the structure depends strongly on the initial geometric configuration of the structures. The Poisson's ratio measured from the structures tested are in the range of -0.30 to -5.15.