Machining-induced temperature field in CFRP materials (TFC)

由于其显著的比强度和刚度，碳纤维增强塑料（CFRP）越来越多地用于高负载的轻质结构，例如在航空航天工业中。通过合理布置单向光纤层，可以使光纤最优地适应有效载荷方向。在原始的近净成形工艺之后，通常需要对零件进行加工以满足精度要求。通常，铣削是用于这一步。与机械加工相关的工件载荷具有机械和热损伤功能表面的风险，这可能导致由于修复或报废而导致的高成本。加工过程中产生的热量，其在零件内的分布以及由此产生的热损伤，除其他因素外，取决于相对于进给方向的纤维取向。在初步研究中，建立了任意纤维取向正交各向异性工件内部温度场计算的解析模型。在该模型中，（有效）热源宽度和热流密度是最重要的。目前，这些参数很难评估，但可以从本研究的实验中识别出典型的个案。本研究计划的目的是从根本上研究热工艺参数、热源宽度和热流密度对刀具和材料性能以及切削条件的依赖关系。为此，现有的CFRP切割加工中心增加了必要的测量设备，以进行热机械过程表征。基于实验识别的特征，推导了经验相关性，并用综合模型描述了经验相关性。由此，建立了基于模型的UD-CFRP工件热影响区的温度场和热损伤仿真模型，并将其作为相关输入参数的函数。为UD-CFRP建立的模型在本项目中进行了经验扩展，从而提供了加工过程中热损伤因果关系的科学相关发现。由于基于模型的UD-CFRP系统仿真揭示了加工由非卷曲织物（NCF）制成的CFRP时的工艺限制，因此有望在工业实践中具有很高的价值。NCF-CFRP的可移植性以及被忽视的影响（例如零件表面的传热）的实施将在第二个资助阶段进一步研究。

Due to their remarkable specific strength and stiffness, carbon fiber reinforced plastics (CFRP) are increasingly used for highly loaded lightweight structures, e.g. in the aerospace industry. By suitable arrangement of unidirectional (UD) fiber layers, the fibers can be optimally adapted to the effective load directions. After the original near-net forming process, it is usually necessary to machine the components to meet the precision requirements. Often, milling is used for this step. Workpiece loads associated with machining carry the risk of damaging the functional surfaces mechanically and thermally which may lead to high costs due to repair or scrap.The heat generated during machining, its distribution within the part and the resulting thermal damage are, amongst other factors, dependent on the fiber orientation with respect to the feed direction. In preliminary research, an analytical model for the calculation of the temperature field within orthotropic workpieces for arbitrary fiber orientations was developed. In this model, the (effective) heat source width and the heat flux are of primary importance. Currently, those parameters are difficult to assess, but could be identified for exemplary individual cases from experiments in this research.The objective of this research proposal is to fundamentally investigate the dependence of the thermal process parameters heat source width and heat flux on tool and material properties as well as on the cutting conditions. For this purpose, the existing machining center for cutting of CFRP is enhanced with the necessary measuring equipment for thermomechanical process characterization. Based on experimentally identified features, empirical correlations are deduced and described by a comprehensive model. Thus, the model-based simulation of the temperature field and thermal damage in the heat-affected zone of UD-CFRP workpieces is established as a function of the relevant input parameters.The model established for UD-CFRP is empirically expanded within this project and thereby delivers scientifically relevant findings on cause-effect relationships of thermal damages in machining. It is expected to be of high value for industrial practice, as the model-based simulation of UD-CFRP systems reveals process limits when machining CFRP made of non-crimped fabrics (NCF). The portability to NCF-CFRP as well as the implementation of neglected effects, e.g. the heat transfer at the part surface, will be further investigated in the second funding phase.