AbstractFailure mechanism and its characterization methods of 3D‐printed fiber‐reinforced composites are still needed thorough investigation. In this work, typical 3D‐printed composites reinforced with 10% and 20% continuous Kevlar fiber are prepared, respectively, three point bending progressive damage experiments are carried out, and the damage evolution are real‐time monitored by acoustic emission (AE) technology. When load reaches the maximum value and failure point, microcomputed tomography (micro‐CT) observations are performed for loaded specimens to explore inside damages. Results show that bending strength of Specimen B (20% fiber) increases by 23% relative to Specimen A (10% fiber). Cumulative count and energy of AE signals are higher for Specimen B, and K‐means clustering algorithm is employed for deep analysis of AE signals. Three damage modes including matrix crack, fiber/matrix debonding, and fiber fracture are clustered and validated by micro‐CT, indicating that the combination of AE and micro‐CT is effective for the characterization of damage evolution of composites. Debonding due to poor adhesion between fiber and matrix is the main damage mode of 3D‐printed Kevlar fiber‐reinforced composites, and damages of Specimen B concentrated in the later stage. This work provides failure characterization methods for 3D‐printed fiber‐reinforced composites.