Mechanical response and energy absorption of curved–wall auxetic honeycomb structures

To meet modern lightweight structural requirements, materials must exhibit high rigidity, toughness, and efficient energy absorption. While auxetic lattices offer promising solutions to these needs, conventional single-material honeycombs often face challenges such as localized crushing, lower negative Poisson’s ratios, and elevated initial peak forces, which can limit their performance. To overcome these limitations, we propose a novel curved-walled honeycomb (CW–HC) lattice that combines geometric refinement with a hybrid hard–soft material design. The structure incorporates a curved wall into the inclined ligaments, with the ligaments made of alternating stiff acrylonitrile butadiene styrene and compliant thermoplastic polyurethane segments. This design concept allows for the definition of material orientation, whether TPU or ABS, through Python programming. Finite element simulations using Abaqus/Explicit, combined with analytical modelling, are used to evaluate the mechanical performance of the CW–HC under quasi-static compression. The effective elastic stiffness is derived analytically, and key energy-absorption metrics are extracted from the simulation results. The enhanced lattices achieve specific energy absorption values of 750 J/kg for pure ABS and 550 J/kg for the TPU–ABS hybrid. The energy-absorption efficiency of ABS slightly exceeds that of TPU–ABS at lower thicknesses, whereas TPU–ABS surpasses ABS at 1.2 mm. The curved wall honeycomb design offers tunable behaviour, reduces peak stresses, and enables lightweight, impact-resistant structures.