Laser transmission joining of thermoplastics and thermoset carbon fiber reinforced plastics: Analyzing the occurrence of ablation and pores

Abstract

In this work, laser transmission joining of thermoplastics and thermoset carbon fiber reinforced plastics is analyzed regarding the occurrence of ablation and pores within the interface of the joint. Therefore, the heating behavior of the used carbon fiber reinforced plastics and the ablation of the upper resin layer of the carbon fiber reinforced plastics are characterized, by performing bead on plate welds using a continuous wave fiber laser (µ ≈ 1064 nm) and a scanner optic. The influence of the applied laser-intensity on the ablation threshold is investigated. Additionally, the temperatures before reaching the ablation threshold are measured by an infrared camera to analyze the ablation mechanisms and to derive a process window for the joining process. The findings are validated by creating joints of carbon fiber reinforced plastics and Polyamide 6, evaluating their morphologic characteristics. The results show that the applied laser intensity and the morphological structure of the used carbon fiber reinforced plastics both have a significant influence on the heating behavior, the ablation threshold and the achievable joint characteristics. It was found that large and pore-free joints can be provided when applying low heating rates by using low laser intensities.