Directional dependency and loading rate sensitivity of 3D-printed continuous fiber-reinforced composite gyroid structures

Purpose This study aims to investigate how fiber type, loading direction, and loading velocity affect the structural and energy-absorption performance of three-dimensional (3D)-printed gyroid structures manufactured from continuous fiber-reinforced composites (CFRCs), thereby assessing their suitability for advanced energy-absorbing applications. Design/methodology/approach Gyroid structures were fabricated via fused filament fabrication using Onyx and Onyx reinforced with glass, Kevlar, and carbon fiber filaments. X-ray computed tomography (CT) imaging was employed to characterize the morphology and locations of internal voids. Mechanical performance was evaluated through quasi-static compression of Onyx and GFF/Onyx gyroids in three orthogonal directions, followed by quasi-static and dynamic compression tests on Onyx, GFF/Onyx, KFF/Onyx, and CFF/Onyx gyroids. Findings CT analysis revealed voids in Onyx concentrated in the infill region due to bead placement, while GFF/Onyx showed voids at fiber–wall interfaces in high-curvature regions. Under quasi-static loading, GFF/Onyx exhibited higher stiffness but lower specific energy absorption (SEA) in the X and Y directions due to interlaminar failure, whereas the Z direction showed stable progressive folding with enhanced SEA linked to bead alignment. Under dynamic loading, Onyx gyroids fragmented, whereas fiber-reinforced variants retained structural integrity through fiber bridging. GFF/Onyx achieved the highest plateau stress in both loading regimes, while KFF/Onyx displayed the greatest strain-rate sensitivity, with plateau stress and SEA increases of 67.43% and 84%, respectively. Originality/value The work provides a comprehensive, directional, and rate-dependent assessment of CFRC gyroid lattices, linking void morphology and fiber architecture to mechanical response. These insights inform the tailored design of 3D-printed CFRC gyroid structures as lightweight, high-performance energy absorbers for advanced engineering applications.