Development and characterization of novel auxetic structures based on re-entrant hexagon design produced from braided composites

摘要

This paper reports the first attempt of developing macro-scale auxetic structures based on re-entranthexagon design from braided composite materials for civil engineering applications. Braided compositerods (BCRs) were produced and arranged as longitudinal and horizontal elements to produce threetypes of auxetic structures: (1) basic re-entrant hexagon structure, (2) basic structure modified by addingstraight longitudinal elements and (3): structure-2 modified by changing structural angle. The influenceof various material and structural parameters as well as structure type on Poisson's ratio and tensileproperties was thoroughly investigated. The auxetic behaviour was found to strongly depend on thestructural angle and straight elements, resulting in lower auxeticity with lower angles and in presence ofstraight elements. Material parameters influenced the auxetic behaviour to a lesser extent and a decreasein auxetic behaviour was noticed with increase in core fibre linear density and using stiffer fibres such ascarbon. The reverse effect was observed in case of tensile strength and work of rupture. Among thesestructures, structure-3 exhibited good auxetic behaviour, balanced tensile properties, and high energyabsorption capacity and their auxetic behaviour could be well predicted with the developed analyticalmodel. Therefore, these novel structures present good potential for strengthening of civil structures.