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.
