Predicting Fiber Attrition during Processing of Long-Fiber Reinforced Composites using a Mechanistic Model Approach

使用机械模型方法预测长纤维增强复合材料加工过程中的纤维磨损

基本信息

批准号：
1633967
负责人：
Tim Osswald
金额：
$ 29.88万
依托单位：
University of Wisconsin-Madison
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-09-01 至 2019-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1633967&HistoricalAwards=false
关键词：
Predicting Fiber Attrition during Processing

项目摘要

Due to their light weight and superior strength, Long Fiber-Reinforced Thermoplastics (LFTs) are used by the automotive and aerospace industries to manufacture critical load bearing structures. One of the major problems with LFTs is that the fibers that reinforce the plastic break during the molding process, compromising the strength of the final part. The fiber breakage also influences other concerns that manufacturers have when making these parts: how the fibers align (fiber orientation) and how they bunch up, leaving portions of the part without fibers (fiber density distribution). Therein lies the problem - it is the fibers that give a part strength. Today, manufacturing companies spend an enormous amount of time and resources trying to control the process to keep the fibers from breaking, bunching up or excessively orienting. They do this by repeatedly making prototypes until getting it right (trial-and-error). The computer simulation within this project can help the engineer visualize the fiber motion within the molding process, and thus solve the underlying problems before actually making a part. This project will result in a tool that industry can use to control the manufacturing process of discontinuous fiber-reinforced polymer composite structures, allowing engineers to make a part they know they can trust. With this increase in trust, these energy-efficient production methods for light weight parts will have a much wider acceptance. An increase in light parts will result in fuel efficiency in the transportation sector, significantly reducing CO2 emissions and directly supporting important worldwide climate change minimization strategies. Furthermore, being able to design LFT parts with confidence will unleash the potential of cost-competitive production of environmentally friendly, light weight and strong composite parts, and provide a technical edge to the automotive and aeronautical industries at a time when energy efficiency and innovation are needed.The modeling approach presented in this project is aimed at providing a tool required to understand and predict defects that arise in the molding of fiber reinforced composites, which today's simulation programs are not able to handle, in particular fiber attrition and fiber density distribution development during flow. The simulation in this project models the behavior of fiber suspensions at polymer processing concentrations using a single particle simulation approach for fiber bending and fiber breakage. The model represents each fiber in the system as a flexible chain of beam elements interconnected by nodes. Modeling flexible fibers is essential to properly understand behavior such as fiber jamming and fiber breakage, which is not accounted for when using the common rigid fiber assumption. The model researched here includes effects such as hydrodynamic forces, fiber flexibility, and excluded volume forces due to fiber-fiber and fiber-wall contacts. Results obtained with this simulation work will be validated with measurements conducted in controlled experimental set-ups at the PI's laboratories, and ultimately comparisons will be made with realist parts made by the PI's industrial partners. At the end of the project, the mechanistic model approach will be coupled to commercial software packages. The final product will allow the process engineer to predict process-induced fiber breakage as well as the properties of the final part during the design phase. Additionally, the processes can be modified to find optimal conditions, screw and gate geometries in order to minimize fiber attrition and achieve ideal fiber length distributions. The final tool will be the first model that incorporates and couples all three fiber properties and their interactions: fiber orientation, fiber density and fiber length distributions. With a higher level of understanding of the fiber motion phenomena during molding it will eventually be possible to mass produce polymer composite parts with increased properties and controlled quality making light weight polymer composites available to a wider range of applications.

由于其轻巧和优势强度，汽车和航空航天行业使用了长纤维增强的热塑性（LFT）来制造关键的负载轴承结构。 LFT的主要问题之一是在成型过程中加强塑料破裂的纤维损害了最终部分的强度。纤维断裂还会影响制造商在制作这些部分时所面临的其他问题：纤维如何对齐（纤维取向）以及如何堆积，使部分部分没有光纤（纤维密度分布）。问题在于问题 - 纤维赋予了部分力量。如今，制造公司花费大量时间和资源来控制该过程，以防止纤维破裂，堆积或过度定位。他们通过反复制作原型直到正确（试用）来做到这一点。该项目中的计算机模拟可以帮助工程师可视化模制过程中的光纤运动，从而在实际制作一部分之前解决了基本问题。该项目将产生一种工具，行业可以用来控制不连续的纤维增强聚合物复合结构的制造过程，从而使工程师能够做出他们知道自己可以信任的部分。随着信任的增加，这些轻巧的零件的节能生产方法将获得更广泛的接受。光零件的增加将导致运输部门的燃油效率，大大减少二氧化碳排放，并直接支持重要的全球气候变化最小化策略。此外，能够充满信心地设计LFT零件将释放出具有成本竞争力的环境友好，轻度和强大的复合零件的潜力模拟程序无法处理，特别是流量过程中的纤维损耗和光纤密度分布的开发。该项目中的模拟使用单个粒子仿真方法在聚合物加工浓度下对纤维悬浮液的行为进行了模拟，以进行纤维弯曲和纤维断裂。该模型代表系统中的每个光纤是由节点互连的光束元件的柔性链。对柔性纤维进行建模对于正确理解诸如纤维干扰和纤维破裂之类的行为至关重要，当使用常见的刚性纤维假设时，这并不是考虑到这些行为。此处研究的模型包括诸如流体动力，纤维柔韧性以及由于纤维纤维和纤维壁接触而排除的体积力等效果。通过此模拟工作获得的结果将通过在PI实验室的受控实验设置中进行的测量进行验证，并最终将与PI工业合作伙伴制作的现实主义部分进行比较。在项目结束时，机械模型方法将与商业软件包结合使用。最终产品将允许工艺工程师在设计阶段预测过程诱导的纤维断裂以及最终部分的特性。此外，可以修改过程以找到最佳条件，螺钉和门几何形状，以最大程度地减少纤维的损耗并实现理想的纤维长度分布。最终的工具将是将所有三种纤维特性及其相互作用融合并伴侣的第一个模型：纤维方向，纤维密度和纤维长度分布。随着对纤维运动现象的更高了解，最终将有可能批量产生具有增加性能和控制质量的聚合物复合零件，从而使较大的应用适用于更广泛的应用。