Study on the energy absorption effect and impact resistance of a composite sandwich panel with carbon fiber reinforced re-entrant hexagonal honeycomb core with negative Poisson's ratio

Negative Poisson's ratio (NPR) structures have excellent energy absorption and buffering properties, but they generally have disadvantage of low specific strength, which restricts their wide applications. Therefore, in this study, the carbon fiber reinforced Nylon material (Nylon 12CF) was prepared and used to construct re-entrant hexagonal honeycomb NPR structure. The reinforced (Nylon 12CF) and unreinforced (Nylon 12) specimens were fabricated by 3D printing technology and tested quasi-statically. Then, the quasi-static of the reinforced and unreinforced re-entrant NPR structure and the impact analysis of the composite sandwich panel (CSP) with reentrant NPR carbon fiber reinforced core are carried out by finite element method. The results show that the NPR structure reinforced with carbon fiber has 112.5% higher failure stress and 113.9% higher energy absorption efficiency than the unreinforced structure. The finite element simulation results are in good agreement with the experimental results. Under the impact load of a 5 kg object with different initial velocities, the maximum of the displacement of the back face sheet's center point of the CSP with reinforced NPR core is smaller than that of CSP with unreinforced NPR core, especially when the impact velocity is 20 m/s. At different initial impact velocities, the CSP of the reinforced NPR structure core all showed high impact resistance, which was about 1.4 times that of the unreinforced NPR structure core. This research provides new ideas for designing more efficient energyabsorbing and impact-resistant structures.