Surface grinding of CFRP composites with rotary ultrasonic machining: a mechanistic model on cutting force in the feed direction

For carbon fiber-reinforced plastic (CFRP) composite components, especially advanced CFRP components with complex three-dimensional features, surface grinding is often needed to generate final dimensions and functional surfaces. Surface damages are frequently induced during surface grinding, reducing the load-bearing capability and service life of the components. Therefore, it is desirable to perform surface grinding of CFRP in a high-quality and high-efficiency way. Rotary ultrasonic machining (RUM) surface grinding has been investigated to machine CFRP for improved surface quality. Cutting force is one of the most important output variables for evaluating RUM surface grinding. The modeling of cutting force is essential to effectively control the occurrence of surface damages during RUM surface grinding of CFRP. In the RUM surface grinding process, the workpiece material is primarily removed by abrasives on the tool peripheral surface, thus it is essential to investigate the feed-direction cutting force model. However, such models are not available in the literature. In this study, for the first time, a mechanistic feed-direction cutting force model in RUM surface grinding of CFRP is established based on the assumption that the material is removed by brittle fracture. The mechanistic model has one parameter, fracture volume factor of the workpiece material, which needs to be determined by an experiment. There is a good consistency between theoretically predicted trends and experimentally observed results on the relationships between feed-direction cutting force and input variables.