Hole quality and thermal defects in drilled CFRP by nanosecond pulsed laser

Abstract To explore the effect of nanosecond pulse laser drilling on the quality of carbon fiber reinforced polymer (CFRP). The effects of laser parameters such as laser power, scanning speed, pulse width and laser frequency on micro-hole quality and the thermal damage generated during the drilling process, were studied by using the univariate methods and the orthogonal experimental method for drilling micro-holes with a diameter of 0.4 mm using a 1064 nm fiber laser. The results indicate that with the use of pumping at the entrance, the hole diameter and the heat-affected zone (HAZ) width at the entrance and exit increased significantly with the increase of laser power, pulse width and frequency, and the decrease of scanning speed. The variation in HAZ width at the exit was correlated with whether the energy reached the carbon fiber ablation threshold. All the holes were tapered and the hole taper was closely related to the magnitude of the change in the laser parameters on the hole diameter at the entrance and exit. Holes with a taper of about 0.3 were obtained when the parameter combination was 99 W, 50 mm/s, 13 ns and 1500 kHz. Experiments indicate that laser power and pulse width are important factors affecting the quality of micro-hole processing. However, thermal damage defects such as striations, micro-cracks, delamination, voids and surface fiber ‘fish scale’ peeling can occur during nanosecond laser drilling.