Fundamental Research on Hole Drilling and Surface Grinding of Carbon Fiber Reinforced Plastic Composites with Rotary Ultrasonic Machining

碳纤维增强塑料复合材料由于其高强度和轻重量而具有许多应用，特别是在航空航天工业中。在飞机上使用碳纤维增强塑料复合材料可以降低制造和维护成本，节省燃料，增加有效载荷和航程，延长飞机寿命。碳纤维增强塑料复合材料部件可以制造成接近净形状，但是，仍然需要额外的加工过程，如研磨和修剪，以去除多余的材料，并且必须钻孔进行组装。复合材料的加工是困难的，因为它们的高磨耗性和倾向于分层在层之间的界面。因此，常用的钻孔和面磨方法成本高，效率低。旋转超声加工已被建议用于碳纤维增强复合材料的加工，但仍有许多科学障碍尚未克服。从这项研究中获得的结果将极大地有利于工程教育、美国经济、美国出口和整个社会。研究的目的是对旋转超声加工碳纤维增强塑料复合材料的钻孔和表面磨削产生新的认识。这项工作将有助于为美国航空航天工业开发一种创新、高效、经济的复合材料加工工艺。本研究将研究旋转超声加工中均质材料的实际去除机理，确定平面磨削中水平超声沿进给方向振动对切削力的依赖关系，探索超声制孔中切削力与分层的关系，了解超声振动对旋转超声加工和超声振动辅助加工的影响。并评估了刀具-工件接触方式和复合材料结构性能对加工性能的影响。方法将包括实验研究（建立实验和测量以获得过程参数）和理论建模（建立有限元分析模型和机械模型以探索对实验现象的基本理解）。该项目还将为复合材料/金属堆的加工提供基础知识，有利于其他难以加工的异质材料的加工，并在研究和教育中探索和实施创新概念。

Carbon fiber reinforced plastic composites have many applications, particularly in the aerospace industry, due to their high strength and light weight. The use of carbon fiber reinforced plastic composites in aircraft results in cost reductions in manufacturing and maintenance, fuel savings, payload and range increases, and aircraft life extensions. Carbon fiber reinforced plastic composite parts can be fabricated to near-net-shape, however, additional machining processes such as grinding and trimming are still needed to remove excess material and holes must be drilled for assembly. Machining of composite materials is difficult, due to their high abrasiveness and tendency to delaminate at the interfaces between layers. Therefore, the commonly used drilling and surface grinding methods result in high cost and low efficiency. Rotary ultrasonic machining has been suggested for the machining of carbon fiber reinforced composites, however, many scientific barriers are still not overcome. Results obtained from this research will greatly benefit engineering education, the U.S. economy, U.S. export, and society in general.The objective of the research is to generate new understanding of hole drilling in and surface grinding of carbon fiber reinforced plastic composites using rotary ultrasonic machining. This work will contribute to the development of an innovative, efficient, and cost-effective composite machining process for the U.S. aerospace industry. The research will study the actual removal mechanisms for homogeneous materials in rotary ultrasonic machining, determine the dependence of horizontal ultrasonic vibration along the feed direction on the cutting force in surface grinding, explore the relationship between cutting force and delamination in ultrasonic hole making, generate understanding of ultrasonic vibration's influence in rotary ultrasonic machining and ultrasonic vibration assisted machining, and assess the effects of the tool-workpiece contact mode and composite structural properties on machining performance. The methodologies will include both experimental investigations (setting up experiments and measurements to obtain process parameters) and theoretical modeling (building finite element analysis models and mechanistic models to explore the fundamental understanding of experimental phenomena). The project will also provide foundational knowledge for the machining of composite/metal stacks, benefit machining of other difficult-to-machine heterogeneous materials, and explore and implement innovative concepts in research and education.