Laser-induced periodic surface structures (LIPSS) can be generated on various materials by irradiation with linearly polarized ultrafast laser radiation, including the surface of carbon fibers. LIPSS enhance the effective area and can affect the wettability of a structured surface. These aspects could be beneficial for carbon fiber reinforced polymers (CFRP) as the higher surface area of structured fibers could result in an increased fiber-matrix adhesion, and an increased wettability can simplify the infiltration process. However, for effective manufacturing of CFRP a structuring rate in the order of magnitude of cm?/s must be achieved.?

In this study LIPSS were generated on dry carbon fiber plies using a wavelength of 1030 nm, a pulse duration of 350 fs and a spot diameter of 88 ?m. The best compromise of low damage and efficient structuring was found to be at 15 pulses per spot and a peak fluence of 2.91 J/cm resulting in a structuring rate of 1 cm?/s. This enabled the manufacturing of infiltration test samples and CFRP samples consisting of nine layers of double-sided structured carbon fiber plies.

The tests showed an increased infiltration speed for structured carbon fibers with epoxy resin in comparison to untreated fibers. The laser treated CFRP had a bend strength of 571 MPa while untreated CFRP had 582 MPa, showing no significant weakening of the fibers by the structuring process. Additionally, structural coloring of carbon fibers induced by LIPSS was observed, and was preserved after the infiltration.