Abstract: 3D printing technology provides a new method for composite material preparation. In order to study the effect of different printing layer thicknesses (t) on the tensile deformation and damage evolution of 3D printed composites, three kinds of composite materials with different printing layer thicknesses were printed by COMBOT-200 printer. The mechanical behavior and damage evolution of the printed composite specimens under tensile loading were studied by using acoustic emission (AE) and digital image correlation (DIC) techniques. Through AE signal analysis, cluster analysis and global strain analysis, the failure mechanism was clearly revealed. The results show that the failure load of 3D printed composites decreases, and the cumulative hits of AE signals per unit time increases rapidly with the increasing printing layer thickness. AE signals under tensile loading are divided into three categories which correspond to matrix cracking, fiber debonding and fiber fracture, respectively. In the same load range, the strain value on the specimen surface increases with the increase of print layer thickness. When the specimen approaches to tensile failure, the surface strains of such material increase sharply, indicating that the specimen is almost fractured. The complementary nondestructive testing technology of AE and DIC can be used to simultaneously obtain the AE response and surface strain field information of 3D printed composites under tensile load,and the damage evolution and fracture mechanism are revealed. The combination of AE and DIC technology provides a reference for the health monitoring of 3D printed composites.

Key words: 3D printed composites, AE, DIC, Cluster analysis, damage mechainism