Process analysis of pseudo-plastic deformation behavior of unidirectional reinforced staple fiber organic sheets

单向增强短纤维有机片材假塑性变形行为过程分析

• 批准号: 471480678
• 负责人: Professor Dr.-Ing. Peter Mitschang
• 金额: --
• 依托单位: Leibniz-Institut für Verbundwerkstoffe (IVW)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/471480678?language=en
• 关键词: Process; analysis; pseudo; plastic; deformation

Continuously fiber-reinforced thermoplastics, so-called organic sheets, are mechanically high-performance semi-finished products, which are processed very economically into shell-shaped components in an efficient thermoforming process. However, the limited drapability of the fiber reinforcement results in comparatively limited geometric component complexity. Organic sheets with continuous carbon or glass fiber reinforcement do not exhibit plastic deformation behavior, since loading of the continuous fibers almost certainly leads to material failure due to the low elongation at fracture. Using staple fiber yarns provides one approach to solve this problem, as they make it possible to achieve an additional degree of freedom in deformation when thermoforming organic sheets. The staple fiber yarns are made of individual reinforcing fibers (so-called staple fibers) with an approximate length of 60 to 80 mm, which are overlapping at different positions. This provides a specific architecture that - in combination with a highly viscous thermoplastic matrix - results in a composite material, in which the individual reinforcing fibers can slide off from each other in the molten state of the matrix. This occurs due to the tensile stress applied in the longitudinal direction of the yarn. In technical terms, this means, that staple fiber organic sheets are pseudo-plastically deformable in the molten state. For the first time, this makes deep-drawing forming possible as it is currently known in metal sheet processing. The project focusses on qualifying the use of staple fiber yarns (made from recycled carbon fibers) in producing organic sheets, as well as on evaluating their processing in the thermoforming process. The fiber ondulation, caused by the production process, requires to be minimized in two process stages, thus improving the process behavior and mechanical properties of staple fiber organic sheets. First, an actively stretched staple fiber tape is produced, which is further processed into organic sheets in the tape laying process with further improvements of the single fiber orientation. These staple fiber organic sheets are analyzed in detail with regard to their pseudo-plastic material behavior. For this purpose, basic research is required for a consistent description of the material and process behavior from tape production to pseudo-plastic deformation in the thermoforming process. In order to investigate the basic mechanisms of pseudo-plastic material behavior, the investigations focus specifically on the behavior of unidirectional staple fiber organic sheets. If this research is successful, an extension to multidirectional laminates, as well as tool and specific thermoforming influences, will be explored in follow-up projects.

连续纤维增强热塑性塑料，即所谓的有机片材，是机械性能高的半成品，可以通过高效的热成型工艺非常经济地加工成壳形部件。然而，纤维增强的有限悬垂性导致相对有限的几何部件复杂性。具有连续碳纤维或玻璃纤维增强的有机片材不表现出塑性变形行为，因为连续纤维的加载几乎肯定会由于低的断裂伸长率而导致材料失效。使用短纤维纱线提供了解决该问题的一种方法，因为它们使得在热成形有机片材时可以实现额外的变形自由度。短纤维纱线由具有大约60至80 mm长度的单独的增强纤维（所谓的短纤维）制成，所述增强纤维在不同位置处重叠。这提供了一种特定的结构，该结构与高粘性热塑性基质结合产生复合材料，其中各个增强纤维可以在基质的熔融状态下彼此滑落。这是由于在纱线的纵向方向上施加的拉伸应力而发生的。在技术术语中，这意味着短纤维有机片材在熔融状态下是伪塑性变形的。这是第一次，这使得深冲成形成为可能，因为它是目前已知的金属板材加工。该项目的重点是鉴定短纤维纱线（由回收碳纤维制成）在生产有机板材中的使用，以及评估其在热成型过程中的加工。生产过程中产生的纤维波动，需要在两个工艺阶段中最小化，从而改善短纤维有机片材的工艺行为和机械性能。首先，生产主动拉伸的短纤维带，其在带铺设过程中进一步加工成有机片材，进一步改善单纤维取向。这些短纤维有机片材进行了详细的分析，就其伪塑性材料的行为。为此，需要进行基础研究，以一致地描述从胶带生产到热成型过程中的伪塑性变形的材料和工艺行为。为了研究假塑性材料行为的基本机制，研究重点是单向短纤维有机片材的行为。如果这项研究是成功的，延伸到多向层压板，以及工具和特定的热成型的影响，将在后续项目中探索。