Resistance Spot Welding of CFRTP Composite Laminates

Resistance spot welding concepts for fastening and attaching structural components made of CFRTP composite laminates are presented. Due to the presence of touching fibers, CFRTP laminates exhibit electrical conductivity in the direction transverse to fiber axes as well as in the fiber direction. Therefore, passing an electric current through two overlapping CFRTP laminates, which are sandwiched between upper and lower electrodes, Joule heat is generated in the region of current concentration to melt them together. When the current flow ceases, their contacting surfaces rapidly cool down and are joined together in one spot. One and three dimensional transient heat transfer analyses have been carried out to provide welding variables appropriate for the spot welding of CFRTP laminates. In the experiment, two pieces of CFRTP coupon specimen made of a commingled yarn prepreg are spot welded for various current and time combinations to investigate the effects of welding variables on the weld strength. Although the material properties of CFRTP composites which directly influence the weldability, —anisotropy, resistivity, thermal conductivity and melting temperature, etc. —are significantly different from those of metals, sound spot welds are produced by the present method.