An experimental study on 3D-printed continuous fiber-reinforced composite auxetic structures

Abstract

Auxetic structures have negative Poisson’s ratios (NPR). Due to the unique deformation mechanism, auxetic structures possess extraordinary mechanical properties, such as indentation resistance, shear resistance, fracture toughness, and energy absorption capability. However, the stiffness and load-bearing capacity are the weak points for auxetic structures. 3D printing of continuous fiber-reinforced composite enables the fabrication of lightweight and highly stiff complex structures, providing a perfect manufacturing method to remedy the shortcomings of auxetic structures. This work investigated the mechanical properties of 3D-printed continuous fiber-reinforced composite auxetic structures. In this study, we utilized continuous fiber-reinforced composite 3D printing to fabricate two types of auxetic structures. The fiber path configurations were varied among the test specimens to explore the effect of fiber distribution on mechanical properties. A uniaxial tensile test was performed to evaluate the tensile properties and Poisson’s ratio of continuous fiber-reinforced composite auxetic structures. Results showed that the tensile modulus and strength have been dramatically improved with a minor mass increase. The auxetic behavior can be strengthened by properly allocating the reinforcing fibers. However, the addition of continuous fiber led to different performances on the selected auxetic structures. In summary, two out of the five specimens demonstrated simultaneous improvements in stiffness, strength, and auxeticity across the conducted tests.