Impact and Compressive Performance of 3D ‐Printed PA6 /Functionalized Graphene Nanoplatelet Sandwich Structures With Auxetic Cores

ABSTRACT This study examines the impact and compressive behavior of additively manufactured polyamide 6 (PA6) nanocomposite sandwich panels reinforced with amine‐functionalized graphene nanoplatelets (NH ₂ ‐GNPs). PA6/NH ₂ ‐GNP filaments were produced and processed via fused filament fabrication (FFF) to manufacture sandwich structures incorporating re‐entrant auxetic, hybrid, and conventional honeycomb cores. Low‐velocity impact, in‐plane uniaxial compression, and postimpact residual compression tests were conducted to assess energy absorption, deformation behavior, and failure mechanisms. Graphene loadings of 1, 2, 3, and 4 wt% were evaluated and benchmarked against unreinforced PA6 structures. An optimal reinforcement level of 2 wt% NH ₂ ‐GNPs resulted in improved compressive strength, delayed densification, and enhanced energy absorption, particularly in re‐entrant auxetic configurations. At higher filler concentrations (3–4 wt%), hybrid cores exhibited improved postimpact damage tolerance, highlighting the influence of filler concentration on residual mechanical performance. Microstructural characterization using scanning electron microscopy and X‐ray micro‐computed tomography confirmed improved filler dispersion and interfacial integrity, supporting effective stress transfer within the printed polymer matrix. Finite element simulations captured stress distribution and deformation mechanisms, corroborating experimental observations. The results provide insight into the structure–property relationships governing the mechanical performance of PA6/graphene nanocomposites manufactured by fused filament fabrication. These results demonstrate that combining auxetic core architectures with tailored nanocomposite reinforcement is an effective strategy for enhancing the structural performance and impact resistance of PA6 3D‐printed sandwich structures.