Characterization and modeling of the laser-based separation process and resulting damage mechanisms of carbon fiber reinforced plastics under fatigue loading

本课题旨在对激光加工过程中温度场的确定、温度场对损伤发展的影响以及循环载荷作用下碳纤维增强塑料（CFRP）的损伤机理进行模拟研究。为此，将采用激光加工的方法生产和切割具有各种基体材料，热固性环氧树脂（EP）和热塑性聚酰胺6.6 （PA）的单向（UD） CFRP。要分离的材料在激光束焦点中蒸发，产生热致损伤，称为热影响区（HAZ）。为了确定机械特性，进行了机械-热应力叠加疲劳试验。集成光纤布拉格光栅（FBG）传感器以及热电偶为激光加工和机械测试中的温度和应变测量提供了基础。为了得到关于CFK损伤机制的结论，在进一步的步骤中，进行了间歇原位计算机断层扫描（CT）研究，并与先前的结果相关联。结合实验研究，将开发一个模拟，根据所使用的材料和层压结构，从强度、速度和材料去除方面描述加工过程，并预测成品部件加工过程中的温度场。在这些数据的基础上，确定HAZ的特征。通过对实验结果的并行验证，对仿真进行了迭代优化。

The aim of the research project is the simulation development for the determination of temperature fields in laser processing, characterization of their effects on the damage development, and the damage mechanisms of carbon fiber reinforced plastics (CFRP) under cyclic loading. For this purpose, unidirectional (UD) CFRP with various matrix materials, thermoset epoxy resin (EP) and thermoplastic polyamide 6.6 (PA) will be produced and cut by means of laser processing. The material to be separated evaporates in the laser beam focus, generating thermally induced damage referred to as heat affected zones (HAZ). To determine the mechanical characteristics, with superimposed mechanical-thermal stress, fatigue tests are carried out. Integrated fiber Bragg grating (FBG) sensor, as well as thermocouples, provide the basis for temperature and strain measurement during laser processing and mechanical testing. In order to obtain conclusions about CFK damage mechanisms, in a further step intermittent in-situ computed tomography (CT) investigations are performed and correlated with the previous results. In combination with the experimental investigations, a simulation will be developed which describes the machining process in terms of intensity, speed and material removal depending on the material used and the laminate structure and predicts the resulting temperature fields during the processing of the finished component. On the basis of these data, the characteristics of the HAZ should be determined. By parallel verification of the results by means of experiments, the simulation is iteratively optimized.