Improved adhesive bonding of CFRP due to re-deposition prevention during UVns-laser cleaning

Due to increasing demand for weight reduction, the use of carbon fiber-reinforced plastics (CFRPs) is steadily growing in the field of transportation like automotive and aircraft. An important method for joining these materials is adhesive bonding, which requires suitable surface conditions and therefore often an appropriate pre-treatment to provide high bond strength. In this context treatment with lasers, especially in the UV range, has been in scientific focus during the last years [1,2]. During the laser treatment, contaminations and the uppermost matrix layer will be ablated and thus are removed from the surface. Re-deposition of ablated material on the as-treated surface but also a too strong fiber exposure are critical problems, which can lead to deterioration of the adhesive strength. In this work the distribution of re-depositions generated by a nanosecond UV laser (l = 248 nm) on EP based CFRP and the prevention of the corresponding re-deposition effects by parameter selection for a laser scanning process have been investigated. A possible strategy to reduce debris formation on the surface with adapted selection of pulse overlap with respect to laser fluence [3] will be presented and limits of laser pre-treatment, like a strong fiber exposure, will be discussed. Finally the UV laser treatment will be compared to other methods for adhesive pre-treatment like CO2-snow in combination with atmospheric pressure plasma and corundum blasting.