<p>Integrating the lightweight and high-strength characteristics of honeycomb and trabecular structures, the load-path rerouting mechanism of the Bouligand helicoidal configurations, and the stress-concentration-reducing benefits of rounded corners, this study proposes a biomechanically inspired helicoidal sandwich structure with progressive failure characteristics. Using 3D printing technology to fabricate the experimental specimens, quasi-static compression tests and finite element simulations were conducted to systematically investigate the influence of core geometrical parameters, with particular emphasis on the helicoidal angle ranging from 0° to 360°, on the compressive behavior and failure modes. The results indicate that increasing the helicoidal angle reduces structural strength and stiffness but promotes stress redistribution, delays local buckling, and significantly enhances energy absorption capacity. Compared with the conventional honeycomb configuration, the trabecula-reinforced structure achieves increases of up to 42%, 76%, and 398% in compressive strength, elastic modulus, and specific energy absorption (SEA), respectively. The incorporation of rounded corners further improves the mechanical performance, with the HTR₁₀ configuration exhibiting maximum increases of 136%, 334%, and 333%, respectively. Moreover, the combination of large helicoidal angles and rounded corners promotes a transition in the failure mode from localized compressive buckling to global progressive folding, resulting in more stable deformation and enhanced energy dissipation.</p>