Exploring the use of an auxetic metamaterial layer as external reinforcement for masonry columns

The present study investigates the effectiveness of an externally bonded layer of auxetic metamaterial as reinforcement for square-section masonry columns by means of numerical analyses. Metamaterials characterized by engineered microstructures and tunable macroscopic properties offer the potential for optimizing the mechanical compatibility with the specific characteristics of the masonry substrate. In addition, their negative Poisson’s ratio allows the compressed layer to laterally confine the masonry with a pressure that is proportional to the vertical loading. The proposed strengthening concept is evaluated with reference to monotonic compression tests reported in the literature. Two three-dimensional finite element macro-models are developed, in which the masonry is represented using Concrete Damage Plasticity, while the reinforcement layer material is modeled as a homogeneous, isotropic, linearly elastic continuum. A comprehensive sensitivity analysis is subsequently carried out, treating the Young’s modulus and Poisson’s ratio of the auxetic layer as independent parameters. The results indicate that, although currently examined primarily from a theoretical standpoint, the proposed solution has the potential to constitute an effective innovation for the reinforcement of masonry columns, provided that the current technological limitations associated with the industrial production of auxetic materials can be overcome.