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，是机械性能优异的半成品，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，纤维增强材料的悬垂性有限，导致几何部件的复杂性相对有限。具有连续碳或玻璃纤维增​​强的有机片材不表现出塑性变形行为，因为连续纤维的负载几乎肯定会由于断裂伸长率低而导致材料失效。使用短纤维纱线提供了解决该问题的一种方法，因为它们可以在热成型有机片材时实现额外的变形自由度。短纤维纱线由长度约为60至80毫米的单根增强纤维（所谓短纤维）在不同位置重叠而成。这提供了一种特定的结构，与高粘性热塑性基体相结合，形成复合材料，其中各个增强纤维可以在基体的熔融状态下彼此滑落。这是由于施加在纱线纵向上的拉伸应力而发生的。用技术术语来说，这意味着短纤维有机片材在熔融状态下是可假塑性变形的。这第一次使得目前金属板材加工中已知的深拉成型成为可能。该项目的重点是验证短纤维纱线（由回收碳纤维制成）在生产有机片材中的使用，以及评估其在热成型过程中的加工。生产过程引起的纤维波动需要在两个工艺阶段最小化，从而改善短纤维有机片材的工艺行为和机械性能。首先，生产出主动拉伸的短纤维带，在带铺设过程中将其进一步加工成有机片材，并进一步改善单纤维取向。对这些短纤维有机片材的假塑性材料行为进行了详细分析。为此，需要进行基础研究，以对从胶带生产到热成型过程中的假塑性变形的材料和工艺行为进行一致的描述。为了研究假塑性材料行为的基本机制，研究重点关注单向短纤维有机片材的行为。如果这项研究成功，后续项目将探索多向层压板的扩展以及工具和特定热成型的影响。