Evaluation and classification of CFRP kerf width by acoustic emission in nanosecond laser cutting

In the nanosecond ultraviolet laser cutting carbon fiber-reinforced polymer process, the photoelectric signal is weak and the temperature difference does not change greatly. Both two are difficult to measure. The acoustic emission (AE) signal is obvious so that it is a feasible method for online monitoring and quality assessment. In this article, A laser with a maximum power of 15 W and a 100 × 100 × 0.5 carbon fiber plate were used. By time domain feature analysis and continuous wavelet transform, a strong correlation is found between the AE signal and the kerf width (WQ). As the laser power increases from 1.17 W to 9.67 W, the corresponding increases in root mean square (RMS), measured area of the rectified signal envelop (MARSE) and the intensity of 280 kHz ranges from 0.03 V to 0.13 V and 75.81 to 332.61, and 0.018 to 0.1, and WQ increases from 49.56 μm to 140.43 μm. Under different scanning speeds (100, 200, 400, 600 mm/s), processing counts (1, 5, 10, 20 times), cutting angles (0, 30, 60, 90°), the similar trends are also reflected. Besides, WQ is refined into three states of uncut, cut off, and slag, and it is found that combined AE signal characteristic could be used for classification. The combined signal characteristic (WN) less than 88,000 corresponds to the uncut state, more than 250,000 corresponds to the slag state, between the two is cut and no slag state.