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

The aim of this work was to investigate the impact of nanosecond pulse laser drilling on the quality of carbon fiber reinforced polymer (CFRP). The effects of laser parameters, including laser power, scan speed, pulse width and laser frequency on micro-hole quality and the thermal damage generated during the drilling process were analyzed. 0.4 mm diameter micro-holes were drilling using a 1064 nm fiber laser, using univariate and orthogonal experimental method. The results indicate that pumping at the entrance leads to a significant increase in hole diameter and heat-affected zone (HAZ) width at both the entrance and exit, as laser power, pulse width and frequency increase, and scanning speed decrease. The width of the HAZ at the exit is dependent on whether the energy reaches the carbon fiber ablation threshold. The holes were tapered and the hole taper was closely related to the change in laser parameters at the entrance and exit of the hole. A taper of approximately 0.3 was achieved with a combination of 99 W, 50 mm/s, 13 ns and 1500 kHz. The experiments indicate that laser power and pulse width are crucial factors that affect the quality of micro-hole processing. However, nanosecond laser drilling can result in thermal damage defects, including striations, micro-cracks, delamination, voids and surface fiber ‘fish scale’ peeling.