Understanding factors affecting the process efficiency, quality and carbon emission in laser drilling of CFRP composite via tailored sequence multiple-ring scanning

Carbon fibre reinforced polymer (CFRP) is increasingly being used in the aerospace, marine, and land transport due to its lightweight, corrosion resistance, and high strength. However, hole drilling during assembly remains challenging due to extensive tool wear and delamination. Laser processing, typically used for drilling and machining, often produces heat effects or is low in efficiency if ultrashort pulse lasers are used. Here, we report an optimised result for a tailored sequence multiple-ring scanning laser drilling method that significantly improves the process efficiency (up to 800 %) by using a continuous wave high power fibre laser operating in pulse mode. Factors such as ring numbers, ring spacing (hatch distance), laser power, and pulse frequency are investigated using statistical design of experiments, and their interactions and effects on process efficiency, carbon emissions, heat-affected zone size, and hole taper are evaluated. The work shows that process efficiency can be significantly increased as the number of rings increases. This is counter-intuitive and would be useful for industrial applications. Using nitrogen as the assist gas results in significantly lower unit process carbon emissions than using argon. The mechanisms behind this efficiency improvement are discussed.