Void Formation During Manufacturing of Composites with Liquid Composite Molding Processes

一种用于制造聚合物复合材料的制造工艺，称为液体复合材料成型，将纤维织物增强材料放入模具中，并向模具中注入聚合物树脂。聚合物复合材料的一个常见制造缺陷是在加工过程中形成和长大的空洞。复合材料加工过程中的空洞可以在所有长度尺度上形成：宏观尺度(厘米到毫米尺度-部分尺度)；中观尺度(毫米到亚毫米尺度-纤维丝束尺度)；以及微观尺度(微米到亚微米尺度细丝直径尺度)。空隙的存在会导致性能的显著降低，甚至会导致零件报废。由于对孔洞的形成和生长缺乏了解，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，为可靠地制造无气孔零件提供指导。这将降低成本，因为使用计算机模拟而不是耗时和昂贵的试验和错误方法减少了拒收和检查。反过来，复合材料将比钢铁和铝更具成本竞争力，并减少对这些材料的进口需求。这项研究将通过在航空航天、汽车、生物医学、能源和体育行业制造成本效益高、重量轻和无腐蚀的复合材料部件来重振美国制造业，使美国经济和社会受益。这项研究将被纳入计算机模拟，该模拟还将为从业者和专业人员提供亟需的培训，以缩短从设计到原型再到产品的制造周期，并鼓励高中生攻读STEM领域，以提高美国在全球经济中的竞争力。本研究用气孔动力学来模拟液态复合材料成型过程中的充型阶段。所开发的总体框架将结合宏观、细观和微观尺度的物理来预测作为材料、过程和几何参数的函数的空穴的形成、生长和运动。为此，(I)将开发一种多尺度流动模拟方法，其控制方程包括空穴输运和动力学；(Ii)将其包括在现有的模拟中，以提高其在宏观、细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，以确保在容许的目标孔隙率内成功填充树脂。这样的指导方针将允许制造工程师制定策略，如提高真空效率，引入局部固结以增加树脂压力，并操纵树脂流动前沿以避免陷入孔洞。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.