Experimental characterization and numerical simulation of the automated fiber placement (AFP) process for thermoplastic fiber-reinforced plastics

热塑性纤维增强塑料部件的高效、高质量和可重复性生产需要自动化制造过程。由于其负载路径取向沉积纤维到近净形状的组件，自动纤维放置（AFP）具有特别大的潜力。在热塑性AFP （TP-AFP）过程中，通过适当的温度控制，原位固结是可能的，即固结代替了没有下游热固性的过程。然而，对该过程的理解仍远未达到TP-AFP广泛工业应用所需的成熟水平。例如，今天仍然很难为最重要的关键参数（如激光功率，速度和压实压力）定义合适的工艺窗口，以确保始终如一的高质量组件。特别是，残余应力和变形的预测没有得到充分的解决，而且过程校准通常基于试错法。这种低预测精度和高工业需求之间的差异的原因同样可以归因于实验表征和建模和仿真的可能性尚未达到最大值。因此，申请人的目的是通过新颖的实验研究和数值模拟方法，从根本上提高对TP-AFP领域的过程理解。在实验方面，重点将放在将光纤传感器集成到AFP过程中。光纤布拉格光栅（FBG）传感器将首次用于监测关键点（包括层压内）的特征TP-AFP过程变量（固结压力和层压温度），从而可以可靠地确定制造后的过程诱导残余应力。长期目标是通过所谓的结构健康监测（SHM）对运行中的组件进行监视。关于TP-AFP过程的数值模拟，目前仍然缺乏一种整体的方法来可靠地预测关键部件的性能。因此，本项目的重点将放在基于非线性有限元方法（FEM）的相应整体过程模型的开发和逐步集成上。目的是实现在预测精度的显著改进，在目前的研究状态与这个TP-AFP整体过程模型。最后，实验、建模和仿真相结合也是本课题的一大特色。例如，模拟活动将一致地访问并行获得的实验结果，以便所有子模型都可以适当地参数化。这种集成的方法最终确保了开发过程模型的最高质量。

The efficient, high-quality and reproducible production of thermoplastic fiber-reinforced plastic components requires automated manufacturing processes. Due to its load-path oriented deposition of fibers to near-net-shape components, automated fiber placement (AFP) has particularly great potential. With proper temperature control during thermoplastic AFP (TP-AFP) in-situ consolidation is possible, i.e. a consolidation in place of the process without downstream thermosetting. However, the understanding of the process is still far from reaching the level of maturity necessary for a broad industrial application of TP-AFP. For example, it is still difficult today to define suitable process windows for the most important key parameters such as laser power, velocity and compaction pressure so that a consistently high quality of components is assured. In particular, the prediction of residual stresses and distortion is only solved insufficiently and process calibration is often based on a trial-and-error method. The reasons for this discrepancy between low prediction accuracy and high industrial demands can likewise be ascribed to possibilities of experimental characterization and modeling and simulation that are not yet maxed out. Therefore, the aim of the applicants is to improve process understanding in the area of TP-AFP fundamentally through novel experimental studies and methods of numerical simulation. On the experimental side, the focus will be on the integration of fiber optic sensors into the AFP process. For the first time, fiber Bragg grating (FBG) sensors will be used to monitor the characteristic TP-AFP process variables (consolidation pressure and laminate temperature) at key points, including within the laminate, thus allowing a reliable determination of the process-induced residual stresses subsequent to manufacturing. A long-term goal is the surveillance of the component in operation by so-called structure health monitoring (SHM). With respect to numerical simulation of the TP-AFP process, there is still a lack today of a holistic approach to reliably predict the critical component properties. Therefore, the focus in this project will be on the development and gradual integration of a corresponding overall process model based on nonlinear finite element methods (FEM). The aim is to achieve a significant improvement in prediction accuracy over the current state of research with this TP-AFP overall process model. Finally, the integration of experiment, modeling and simulation is also a particular feature of this project. For example, the simulation activities will consistently access the experimental results obtained in parallel so that all the sub-models can be appropriately parameterized. This integrated approach ultimately ensures the highest possible quality of the developed process model.