Enhanced in-plane impact characteristics of a novel circular-reinforced sinusoidal honeycomb

Curved-wall auxetic honeycombs show significant potential for alleviating stress concentrations and enhancing energy absorption. In this study, a novel circular-reinforced sinusoidal honeycomb (CRSH) was developed by reinforcing the nodes of a conventional sinusoidal honeycomb (SH) with circular rings. Finite element models were validated through quasi-static compression tests on 3D-printed CRSH and SH specimens. The influence of three dimensionless parameters ($\overline{a}$, $\overline{t}$, and $\overline{r}$) on the in-plane performance of CRSH was systematically assessed across a broad range of impact velocities. As velocity increases, CRSH transitions from a five-stage deformation mode to a four-stage mode, and finally to a three-stage mode. Theoretical models were developed to predict two plateau stresses under low-velocity impacts and one plateau stress under high-velocity impacts, showing good agreement with the simulated results. Compared with geometrically equivalent circular-reinforced quadrilateral honeycomb (CRQH) and SH, CRSH exhibits a strong auxetic effect, more stable plateau stresses, and higher specific energy absorption (SEA). Under low-velocity impacts, CRSH shows 70.14 % higher SEA than CRQH and 131.01 % than SH. This advantage persists at medium velocities, with SEA exceeding CRQH by 26.09 % and SH by 110.92 %, and even at high velocities, CRSH maintains a 24.43 % advantage over SH. Parametric analyses reveal that reducing $\overline{a}$ while increasing $\overline{t}$ and $\overline{r}$ can optimize SEA, ensuring CRSH’s competitiveness under high-velocity impacts. Its tunable impact performance and multi-plateau mechanism make CRSH particularly well-suited for adaptive energy absorption applications in aerospace, automotive safety, and defense systems.