Evaluation of surface roughness based on sampling array for rotary ultrasonic machining of carbon fiber reinforced polymer composites

Abstract This paper focuses on the evaluation of surface roughness of carbon fiber reinforced polymer (CFRP) composites after rotary ultrasonic machining. The carried out research involved a novel evaluation method based on sampling array, in which N  ×  N samples are averagely distributed over machined surface. Surface topography of each sample was measured by a white light interferometer and quantitatively characterized by arithmetical mean height ( S a ). Frequency histogram of S a in sampling array was fitted with Gaussian function. The mean value and standard deviation of Gaussian function were applied to evaluate surface quality of machined surface. The conducted research shows that the critical sampling number is 13 × 13 and the relative error has found to be less than 1%. Moreover, the spatial distribution of S a across the surface has been analyzed innovatively and found that small value of S a takes a large proportion while large one presents strip spatial distribution along feed direction. Fracture mechanism of reinforcement fibers accounts for this phenomenon. This research work provides a foundation for surface quality evaluation of composites and has applications for precision manufacturing industry.