Influence of long and short glass fiber on the mechanical behaviour of a single cell metamaterial

Additive manufacturing is presenting new challenges in various aspects of part production. Among these, the potential benefits derived from material complexity have been growing in recent years, especially when using polymeric materials. In fact, mixing polymers with long/short fibres lead to moderate to significant improvements in the mechanical properties of the parts. The degree of improvement strongly depends on the part geometry and can become critical in the case of a workpiece with a repeating pattern, such as metamaterials. In this preliminary research, the authors investigate the mechanical performance of a single-hourglass cell which is a common auxetic geometry used to achieve a negative Poisson ratio in metamaterials. Nylon was used as the matrix, and glass as the fibre. FFF additive process was used to produce samples with different cell designs (in width, size, inclination) and the nature of the fibres (long and short). The results were analysed using statistical methods.