Influence of geometry on the compressive behaviour and energy absorption of 3D-Printed honeycomb, auxetic, and hybrid sandwich cores

Abstract

The mechanical performance of additively manufactured sandwich cores is governed by cellular topology and process-induced anisotropy. This study investigates the quasi-static compressive behaviour and failure-based energy absorption of fused deposition modelling (FDM) printed polylactic acid (PLA) cores with honeycomb, re-entrant auxetic and hybrid geometries. Nine configurations varying in wall thickness and core height were tested to full failure at 5 mm/min per ASTM D695. Two independent prints per case were tested and mean values are reported. Energy absorption (EA) and specific energy absorption (SEA) were quantified by trapezoidal integration of load-displacement curves up to actual failure displacement and normalized by measured mass. Mean EA ranged from 4.70 J to 33.73 J and mean SEA from 0.39 J/g to 1.72 J/g. Low-aspect-ratio honeycombs deform by stable progressive buckling achieving the highest mean SEA of 1.72 J/g (Case 2, 1.2 mm wall) and 1.68 J/g (Case 3). Increasing core height from 6.0 mm to 10.0 mm promotes global buckling and interlayer fracture, reducing mean EA by 85.2% to 4.70 J. Re-entrant auxetic cores exhibit lateral contraction with serrated plateaus and 25-45% load drops due to node fracture, yielding mean EA of 6.59-21.82 J. Hybrid cores combining honeycomb and auxetic sub-structures produce sequential collapse resulting in the highest mean absolute absorption of 33.73 J at 12.83 mm, exceeding optimal honeycomb by 6.3%, with a mass penalty (26.80 g vs 18.92 g) reducing SEA to 1.26 J/g. Family-level normalized performance shows auxetic best for peak control and hybrid best for SEA and crush force efficiency. These findings provide experimentally validated design guidelines for tailoring crashworthiness of low-cost FDM PLA sandwich cores for lightweight impact-resistant applications.

The authors' abstract, as published at the source. International Journal of Protective Structures, 2026 · DOI ↗