PSI - Issue 61

T. Stoel et al. / Procedia Structural Integrity 61 (2024) 206–213

207

2

T. Stoel et al. / Structural Integrity Procedia 00 (2023) 000 – 000

1. Introduction In the context of politically and economically motivated efforts to achieve climate and sustainability goals, reducing emissions in the mobility sector is essential (Banister (2011)). To achieve emission reductions, greater energy and material efficiency must be strived for, which in vehicle construction is realized by lightweight design. The objective of lightweight design is to reduce mass input while maintaining the overall performance of the component. The lower mass means less energy is required when using lightweight components, this results in lower energy consumption and correspondingly lower emissions (Sun et al. (2016)). Carbon fiber reinforced plastics (CFRP) are characterized by their good lightweight properties (Lee et al. (2019)). Until now, finishing operations such as milling or abrasive water jet cutting have been required to meet geometric and functional requirements, which lead to high production costs (Monoranu et al. (2019)). Therefore, alternative manufacturing processes need to be investigated for cost-efficient use of CFRP in lightweight design (Kafara et al. (2017)). As a mass production technology for piercing and trimming operations, shearing might meet those requirements. Shearing of unidirectional (UD) CFRP was investigated by Shirobokov et al. (2015) and showed potential. For an improved sheared surface quality, the use of a counter punch (Shirobokov et al. (2015)) as well as sharp cutting edges (Klocke et al. (2017)) was proposed. Furthermore, for metals improved sheared surface quality can be achieved by near-net-shape blanking technologies like fine blanking with a small die clearance (Klocke (2013)). The extensive experience available for fine blanking of steel raises the question to which extent it is possible to transfer this knowledge to the machining of CFRP. Therefore near-net-shape blanking of CFRP comparable to fine blanking except for the use of a chamfered die to provide a sharp cutting edge at the die and without vee ring to avoid delamination is to be investigated. For a corresponding investigation, the numerical analysis is a suitable method in addition to experimental testing. Previous studies in the field of numerical modeling of shearing of CFRP were carried out in the context of the shearing of multidirectional laminates by Shirobokov et al. (2018) and Yashiro et al. (2014). Specific numerical investigations of near-net-shape blanking technologies have not been performed so far. 2. Materials and Methods Until now the cause effect relations of material and process parameters by means of near-net-shape blanking of UD CFRP laminates are not sufficiently researched. From an engineering point of view, the analysis of the blanking force is an important characteristic for the process design and enables a validation by means of experimental investigations. For this reason, the purpose of this study is to develop a finite element (FE) process model of near-net shape blanking for the numerical investigation of the influence of process and material parameters on the blanking force. 2.1. Approach The basis of the numerical modeling was an existing simulation approach for shearing of CFRP laminate by Shirobokov et al. (2018). This simulation approach was extended with respect to the representation of a small die clearance, a controlled counter punch force as well as the possibility of representing different fiber orientations and fiber volume fractions of the laminate. Figure 1a shows a schematic representation of the correspondingly adapted model setup. For the near-net-shape blanking process, four tool components are used. The actual shearing of the laminate is performed due to a relative motion of punch and die. In addition, the tool components blank holder and counter punch are used. The purpose of blank holder and counter punch is to induce compressive stresses in the shear zone which cause a hydrostatic compressive stress state in the shear zone (Klocke (2013)). As a result, tensile stress induced crack growth is suppressed, which ultimately leads to improved sheared surface quality. Furthermore, the counter punch prevents a bending of the blanked part.