01 Sep 2012 Science

Development of auxetic structure in composite materials application in structures

The Poisson’s ratio of any material is defined as the ratio of the lateral length and longitudinal length, typically ranging between 0 and 1. In general, when subjected to the application of a uniaxial longitudinal loading, the material elongate in that direction and reduce the cross section; however, in auxetic materials this phenomenon is reversed, i.e., the materials have the ability to stretch in one direction and expand in the other, presenting a negative Poisson ratio.

In this work, we intend to develop auxetic structures from stranded men in composite material based on theoretical designs. The auxetic structures were developed using braids with core rods containing glass fibres, basalt and/or carbon for axial reinforcement, and polyester filaments for the braided structure, impregnated with epoxy matrix. The auxetic behaviour of the developed structures was evaluated using advanced image analysis methods and exhibited negative Poisson’s ratio, ranging between -3.80 and -8.00 depending on the design used. The basic design of these structures was modified with linear vertical rods in order to meet the needs of structural reinforcement in civil engineering that require a high relation strength/deflection. Reinforced masonry structures with these materials were tested and compared in terms of the impact behaviour, and the auxetic behaviour has demonstrated a significant positive effect on the capacity for absorbing energy.

This project was carried out within the framework of the PhD studies of the researcher Subramani Pichandi under the supervision of Professor Raul Fangueiro and the co-supervision of Professor Daniel Oliveira.



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