This paper presents an evaluation of two distinct techniques to improve energy absorption capability of an accordion cellular structure with close-to-zero Poisson’s ratio. For this purpose, fiber-reinforcement and foam-filling methods were employed to address the material enhancement and to obtain light and tough structures with high specific energy absorption. Employing an innovated additive manufacturing based on material extrusion process, specimens of glass fiber-reinforced PLA were produced in both in-plane directions to compare with the un-reinforced counterpart. In continue, some of the 3D printed samples were strengthened by means of polyurethane foam in their hollow structure. The quasi-static compressive tests showed that the initial stiffness, collapse stress, and plateau stress were enhanced significantly in the presence of both fiber-reinforcement and foam-filling. The energy absorption behavior of the enhanced cellular structure was then simulated via finite element method and a good-agreement between experimental and numerical results was observed. Afterwards, an analytical model was proposed to validate the observed elastic stiffness of the compressive samples. In comparison with the relevant cellular configurations, it was also demonstrated that the fiber-reinforced PLA accordion cellular structures, as well as the foam-filled ones, exhibited not only a greater specific energy absorption but also presented a lower density.
