3D打印复合材料拉伸变形的声发射监测

Acoustic emission monitoring of tensile deformation of 3D printed composites

3D打印技术为复合材料制备提供了一种新方法。为了研究不同打印层厚度(t)对3D打印复合材料拉伸变形和损伤演化的影响,采用COMBOT-200打印机打印了3种不同打印层厚度的复合材料。采用声发射(acoustic emission, AE)和数字图像相关(digital image correlation, DIC)技术研究了拉伸加载下3D打印复合材料的力学行为和损伤演化。通过声发射信号分析、聚类分析和全局应变分析,清晰揭示了其失效机理。结果表明:随着打印层厚度的增加,3D打印复合材料的破坏载荷减小,单位时间内AE信号累积撞击数迅速增加;拉伸载荷下AE信号分为三类,分别为基体开裂、纤维脱黏和纤维断裂。在相同载荷范围内,试件表面应变值随打印层厚度的增加而增大。当试样接近拉伸破坏时,材料的表面应变急剧增加,表明试样接近断裂。利用AE和DIC相辅相成的无损检测技术,可以同时获得3D打印复合材料在拉伸载荷下的声发射响应和表面应变场信息,揭示其损伤演化和断裂机理。AE和DIC技术的结合为3D打印复合材料的健康监测提供了参考。

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.