Void Formation During Manufacturing of Composites with Liquid Composite Molding Processes

一种被称为液体复合成型的制造工艺，用于制造聚合物复合材料，将纤维织物为基础的增强物放入模具中，并将聚合物树脂注入其中。聚合物复合材料中常见的制造缺陷是在加工过程中形成和生长的空隙。复合材料加工过程中的空洞可能在所有长度尺度上形成：在宏观尺度上（厘米到毫米尺度-零件尺度）；中观（毫米至亚毫米尺度-纤维束尺度）；和微尺度（微米到亚微米尺度的灯丝直径）。空洞的存在会导致零件性能显著降低，甚至被拒绝。由于缺乏对空洞形成和生长的了解，需要采用昂贵的检测技术来确保生产的零件符合设计规范。这项工作将进行基础研究，将所需的知识纳入制造模拟，为可靠地制造无空洞零件提供指导。这将降低成本，因为使用计算机模拟而不是耗时且昂贵的试验和错误方法可以减少拒收和检查。反过来，复合材料将比钢和铝更具成本竞争力，并减少对这些材料进口的需求。这项研究将通过在航空航天、汽车、生物医学、能源和体育等行业制造成本效益高、重量轻、无腐蚀的复合材料部件，使美国经济和社会重新焕发活力。该研究将被纳入计算机模拟，这也将为从业者和专业人士提供急需的培训，以减少从设计到原型到产品的制造周期时间，并鼓励高中生追求STEM领域，以提高美国在全球经济中的竞争力。本文描述了液体复合材料成型过程充型阶段的空隙动力学模型。所开发的总体框架将结合宏观、中观和微观尺度物理来预测孔隙的形成、生长和运动，作为材料、工艺和几何参数的函数。为了实现这一目标，(i)将开发一种多尺度流动建模方法，其中包括控制方程，包括空隙输运和动力学；（ii）将其纳入现有的模拟中，以提高其在宏观、中观和微观尺度上对孔隙度的预测能力。这将有助于确定材料和工艺参数窗口，以确保在可容忍的目标孔隙率内成功填充树脂。这样的指导方针将使制造工程师能够制定诸如提高真空效率，引入局部固结以增加树脂压力和操纵树脂流动以避免空隙夹带等策略。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

A manufacturing process, termed Liquid Composite Molding and used to fabricate polymer composites, places a fibrous textile-based reinforcement into a mold and injects a polymer resin into it. A common manufacturing defect in the polymer composite are voids which form and grow during the process. Voids during composite processing may form at all length scales: at the macro (cm to mm scale- part scale); meso (mm to sub mm scale- the fiber tow scale); and micro scale (micron to submicron scale filament diameter scale). The presence of voids results in a significant reduction in properties and even rejection of the part. Due to lack of understanding about void formation and growth, expensive inspection techniques need to be incorporated to ensure fidelity of the produced part to design specifications. This work will conduct fundamental research to incorporate the required knowledge in a manufacturing simulation to provide guidelines to reliably manufacture void-free parts. This will reduce costs due to less rejections and inspections from the use of computer simulations instead of time-consuming and expensive trial and error methodology. In turn, composites will be more cost competitive with steel and aluminum and reduce the need for import of these materials. The research will re-invigorate US manufacturing sector by fabricating cost effective, light weight and corrosion free composite parts in aerospace, automotive, biomedical, energy and sports industries benefiting the U.S. economy and society. The research will be incorporated in a computer simulation which will also provide the much-needed training to practitioners and professionals to reduce the manufacturing cycle time from design to prototype to product and encourage high school students to pursue STEM fields to advance US competitiveness in the global economy. This research describes the void dynamics to model the mold filling stage of the Liquid Composite Molding processes. The general framework developed will couple the macro, meso and micro scale physics to predict void formation, growth and movement as a function of material, process and geometric parameters. To accomplish this, (i) a multi-scale flow modeling approach will be developed with governing equations that include the void transport and dynamics to (ii) be included into an existing simulation to improve its predictive capabilities for porosity at macro, meso and micro scale. This will help determine material and processing parameter window that will ensure successful resin filling within tolerated target porosity. Such guidelines will allow manufacturing engineers to develop strategies such as improving vacuum effectiveness, introducing local consolidation to increase resin pressure and manipulate resin flow front to avoid entrapment of voids.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.