Modelling the negative Poisson's ratio of compressed fused fibre networks

Examples of auxetic fused fibrous assemblies can be found among both natural and synthetic materials. In theory, fibrous network materials can exhibit negative Poisson's ratios, yet the deformation mechanisms and parameters which give rise to a negative Poisson's ratio in disordered fibrous materials are not well understood, and this class of auxetic materials remains largely under‐explored. The potential applications of auxetic fibre networks include their use as reinforcement in composites. The process of embedding auxetic random fibrous networks in a polymer matrix is an attractive alternate route to the manufacture of auxetic composites; however, before such an approach can be developed, a methodology for designing fibrous networks with the desired negative Poisson's ratios must first be established. This requires an understanding of the factors which bring about negative Poisson's ratios in these materials. In this work, we present a modelling approach to study the auxetic behaviour of compressed fused fibrous networks. Finite element analyses of three‐dimensional stochastic fibre networks were performed to gain insight into the effects of parameters such as network anisotropy, network density and degree of network compression on the out‐of‐plane Poisson's ratio. The simulation results suggest that compression and anisotropy are the critical parameters that give rise to auxetic behaviour in these materials. We comment on the use of this model to inform the design of fibrous auxetic materials across different length scales, and on the feasibility of developing auxetic composites by using auxetic fibrous networks as the reinforcing phase. Preliminary experimental results indicate that this approach is a promising route in the pursuit of negative Poisson's ratio composites.