Process innovation for the internal coating of carbon fiber reinforced plastic (CFRP) tubes via thermal spraying

The application of thermally sprayed coatings on CFRPs has.gained great interest to enhance thermal and tribological properties and several processes have been optimized. However, for the coating of internal surfaces of tubes there is no sufficient technical solution. This paper presents a novel process technique for the coating of internal surfaces of CFRP tubes via the transplantation of thermally sprayed coatings. A negative shape tube with defined surface and material properties has been coated by atmospheric plasma spraying (APS). The CFRP has been produced by filament winding onto the coating. After curing the specimen was separated from the tube. With this process innovation CFRP tubes with internal ceramic or metallic coatings can be produced without and any thermal degradation of the polymeric matrix nor any damage to the carbon fibers. There are several advantages compared to the conventional coating of CFRP. With the novel process technique internal coatings with a low roughness of Rz=10 µm can be produced as sprayed without post processing. The speciments have a significantly lower corrosion tendency compared to conventional coated CFRPs. A high adhesion strength of the coatings could be achieved with 16 MPa. The hardness of the internal alumina coating is 918 HV0.1.