Bio-derived PA11/bamboo charcoal/glass fibre composites for fused filament fabrication, warpage control, strength and flame retardancy

Adoption of polyamide-11 (PA11) in fused-filament fabrication (FFF) has been limited by warpage, trade-offs between stiffness/strength and toughness at service temperatures, and reliance on non-sustainable flame-retardant packages. To address these challenges, a bio-derived library of PA11 composites was formulated and FFF-printed by compounding bamboo charcoal (BC, 0–5 wt.%) with or without glass fibre (GF, 30 wt.%). Filaments were extruded and specimens were characterised for warpage, wettability, thermo-mechanical response, flammability, and mechanical performance (tensile/flexural/impact/hardness) from 23-90°C. Warpage was suppressed from 3.81 mm in PA11 to ∼0.1 mm with 3 wt.% BC + 30 wt.% GF (∼97% reduction), indicating effective shrinkage control during printing. Mechanical performance was elevated: ultimate tensile strength reached 76.5 MPa in the hybrid, with increased hydrophobicity and improved high-temperature stiffness retention. Horizontal burning rate was lowered by up to 61.9% versus PA11, evidencing char-forming and barrier effects of BC with GF. Architected honeycomb meta-bio-composites were also printed, exhibiting quasi-zero-stiffness force regulation and high specific energy absorption (655 J/kg at 50% compression), highlighting utility for energy dissipators and overload protection. Sustainable, FFF-printable PA11/BC/GF formulations are therefore evidenced to deliver lightweight, durable candidates for automotive, robotic, and protective-sport applications while clarifying processing – structure – property relationships for functional PA11.