Mechanical Behavior of <scp>FDM</scp> Printed <scp>CF</scp> ‐ <scp>3D</scp> Gyroid Structure Under Bending Moment: A Combined Experimental and Numerical Study

ABSTRACT The flexibility of 3D printing has made it a prominent method for manufacturing sandwich cores with intricate architectures, such as gyroid lattices. This study investigates the mechanical behavior of FDM‐printed carbon fiber (CF) gyroid‐based sandwich structures (GSS) through integrated numerical and experimental approaches. Four‐point bending tests determined the ultimate strength, stiffness, and failure modes, while a numerical model incorporating the 2D Hashin criterion simulated progressive damage. Results indicate that the GSS undergoes nonlinear progressive failure, with tested specimens exhibiting average ultimate load and stiffness values of 1350 N and 120 N/mm, respectively. At the tested scale, failure initiated via shear fracture between the indenter and support, yet the energy absorption capacity of the structure preserved over 50% residual strength post‐damage. Numerical results revealed that the interlaminar shear stress induced crack initiation and propagation which caused the structure to collapse. Comparative analysis of gyroid lattice sizes (5, 10, 20 mm) exhibited that lattice stiffness governs force transmission paths and failure modes: the 5‐mm lattice caused local crushing under the indenter, whereas the 15‐mm lattice prompted global transverse fracture. This work provides novel insights into the damage mechanics and design of architected composite sandwich structures.