Auxetic behavior of 3D-printed structure made in acrylonitrile butadiene styrene and carbon fiber-reinforced polyamide

Parts with an auxetic structure, which exhibit negative Poisson's ratio, can be associated with a novel class of smart materials. Such interesting property has been widely explored, over the time, for different applications, i.e., medical, automotive, robotic and aeronautic field. However, the research about the design and analysis of auxetic behavior is still on the way. In this paper, a 2D re-entrant honeycomb structure was realized using material extrusion additive manufacturing technology. Two different materials, acrylonitrile butadiene styrene and carbon fiber-reinforced polyamide were adopted. The technique of digital image correlation was implemented during the tensile test to evaluate over the time and in different areas of specimens the strain behavior of the auxetic structure for both investigated materials. The measured negative Poisson's ratio confirmed the auxetic behavior of the designed structure. The comparison between the two investigated materials showed a different trend of negative Poisson's ratio.