High Speed Ridged Fasteners for Multi-Material Joining

Automobile manufacturers are reducing the weight of their vehicles in order to meet strict fuel economy legislation. To achieve this goal, a combination of different materials such as steel, aluminum and carbon fiber composites are being considered for use in vehicle bodies. The ability to join these different materials is an ongoing challenge and an area of research for automobile manufacturers. Multiridged fasteners are a viable option for this type of multi-material joining. Commercial systems exist and are being used in the industry, however, new ridged nail designs offer the potential for improvement in several areas. The goal of this paper is to prototype and test a safer flat-end fastener whilst not compromising on strength characteristics, to prevent injury to factory workers. The nails were prototyped using existing RIVTAC® nails. To analyze these nails, joints were created using aluminum 6061-T6 and are tested in the shear and cross-tension loading conditions, using JIS Standards. A baseline strength comparison between the proposed designs and the existing ogive shaped nails was performed. From the results, it was observed that flat- ended nails producing a joint with only a 4% decrease in retention strength can be made and used. This can be considered a good tradeoff, since we are able to remove the sharp end of the nail whilst retaining good strength characteristics.