Polyamide12‐Meta‐Composites with Excellent Mechanical Performance, Shape‐Memory, Flame Retardancy and 3D/4D Printability

ABSTRACT Achieving multifunctional polymer composites that combine mechanical strength, thermal stability, flame retardancy, and shape‐memory capability while remaining compatible with additive manufacturing remains challenging. In this work, a comprehensive materials library of fused filament fabrication (FFF)‐printable polyamide 12 (PA12) composites was developed using bamboo charcoal (BC), a BC/carbon nanotube (BC/CNT) hybrid, and conventional glass fiber (GF) and carbon fibers (CF). PA12/BC and PA12/BC/CNT composites were compounded, extruded into filaments, and systematically characterized in terms of microstructure, wettability, thermomechanical behavior, flammability, shape‐memory performance, and mechanical properties at ambient and elevated temperatures. The BC/CNT hybrid represents the key innovation of this study, enabling a synergistic reinforcement strategy that simultaneously enhances stiffness, strength, damping, thermal stability, flame retardancy, and hydrophobicity while preserving excellent shape‐memory behavior. In contrast, GF and CF reinforced composites provide higher stiffness and strength but suppress shape‐memory functionality. Extending beyond material development, architected shape‐memory polymer meta‐composites with honeycomb, honeycomb‐circle hybrid, and auxetic geometries were fabricated via 4D printing. They demonstrated shape‐recovery, force‐regulating behavior and high energy absorption/dissipation under compression. These results establish BC/CNT‐reinforced PA12 as a more sustainable and multifunctional alternative to conventional fibre‐reinforced systems for advanced additive manufacturing applications.