In the following, laser transmission welding was transferred to heat conduction welding for joining endless carbon fiber reinforced thermoplastics (CFRTP). The purpose of the investigation was to demonstrate the laser weldability of this material combination. In these investigations, lap shear samples were welded using a carbon fiber fabric and a non-crimped fabric in a PEKK matrix and a carbon fiber fabric with a PPS matrix. The influence of surface contaminations and the effect of the removal technique on the lap shear strength were investigated. These investigations generate the basic knowledge to transfer this new CFRTP-CFRTP welding technique for real parts.