To improve the energy absorption efficiency of auxetic (negative Poisson's ratio, NPR) honeycomb structures for naval blast protection, this study proposes a novel in-plane NPR honeycomb design. The structure consists of a straight-walled, tetra-ligament, anti-chiral aluminium alloy framework combined with a foam-concrete infill.

Finite-element models were developed in Abaqus, where the 6061-T6 aluminium alloy framework was modelled using S4R shell elements and the foam-concrete filler using C3D8R solid elements. In-plane crushing simulations were conducted at 1 m/s, 15 m/s and 100 m/s. The collapse modes (crushing mode), stress-strain responses, and volumetric specific energy absorption (SEA) of unfilled, polyurethane-filled and foam-concrete-filled specimens were compared.

The foam-concrete infill modified the collapse mode, redistributed stresses more uniformly, and introduced brittle-material characteristics into the stress–strain curves. At high (100 m/s), medium (15 m/s) and low (1 m/s) impact velocities, the SEA of the foam-concrete-filled honeycomb exceeded that of the unfilled baseline by more than 200 %.

The tetra-ligament, anti-chiral architecture effectively combines the ductility of the metallic framework with the brittle crushing behaviour of foam concrete, offering a promising lightweight, high-efficiency solution for blast protection in naval structures.