Dual beam laser grooving of CFRP by pulsed lasers

We have been investigating micromachining of CFRP by short laser pulses in order to minimize material damages and HAZ. The laser system used in this study was a Ti:Sapphire laser with pulsewidth of 100fs. For comparison, we also used 200ps stretched pulses from the Ti:Sapphire laser and output from a 200ns-pulsed fiber laser. In order to overcome slow processing speed by ultra-short pulses, we have proposed a novel dual beam grooving. In the first process, small-energy ultra-short pulses are used to cut the edges of the groove with multiple scanning. Secondly, high-energy long-pulses ablate the remained part with a single scanning. We used 1.3mm-thick uni-directional CFRP samples. Trenches with depth of 100µm and width of 50µm were machined by 200ps laser pulses. Then, 200ns fiber laser pulses were focused on one of the remained part in a single scanning. As a result, a groove with depth of 100 µm and width of 150 µm was formed without significant HAZ.