Joining with high strength is also expected to apply to airplanes or racing cars to save their energy and to enhance their mobility. However it is difficult to join between metals and polymers. In order to enhance the joining strength, a carbon fiber reinforced interface has been suggested. To prevent to decay the carbon fiber by decomposition, the fiber has been coated with nickel film, which protects the carbon fiber against metal liquid. One side plain of the coated fiber is dipped into metal liquid. After solidification, another side of the coated felt is also dipped in other materials. The nickel coated carbon fiber reinforced interface between metals and differential materials probably acts as one of ideal original bonding.