Features of acoustic emission and micro‐CT of 3D‐printed continuous Kevlar fiber‐reinforced composites during progressive damage under flexural load

Failure 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.