As FSS technology provides the capability to join multi-material structures on robotic platforms using linear configurations, the development more » of this technology for use on the BIW will impact a great diversity of CFRP joints within the vehicle thus, allowing a greater reduction in vehicle mass through more specifically designed structures. Implementation of FSS technology for joining polymer composites to metals will enable greater use of lightweight materials by providing technology capable of joining linear configurations without the use of adhesives or other third-body fasteners by creating an in-situ joint from the parent materials. The purpose of this project was to develop the critical process technology, models, and tools necessary to advance the Friction Stir Scribe, FSS, joining method through experimentation, validation at the laboratory scale, and integration into a production-like robotic environment. When peak load was increased, fretting between the rivet and the top of AZ31B became more dominant to initiate a crack during fatigue testing. From fractography, the crack initiation for lower peak load (<1 kN) case was observed at the fretting positions on the top and bottom surfaces of AZ31B sheet. The fatigue performance was better at higher peak load more » (>2 kN) and comparable to that of resistance spot welding of AZ31B to AZ31B at lower peak loads (<1 kN). Fatigue life of the CFRP-AZ31B joint was studied at various peak loads of 0.5, 1, 2, and 3 kN and compared with the resistance spot welded AZ31B-AZ31B from the open literature. Ultrafine grains were formed at the joint in AZ31B as a result of dynamic recrystallization, which contributed to the higher hardness. With the increase of rivet shank size, lap shear fracture load and mechanical interlock distance increased. « lessĬarbon fiber reinforced polymer (CFRP) and AZ31B Mg alloy were joined by the friction self-piercing riveting (F-SPR) with different steel rivet shank sizes. However, steel rivet was not significantly corroded potentially due to sacrificial anode effect by which AZ31B corroded first in the galvanic couple. From cross-sectional analysis of the F-SPR joint, extensive corrosion of AZ31B was observed at the joint and other exposure areas. With up to 200 h of exposure, the post-corroded F-SPR joint integrity retained 81.2% of the pre-exposure F-SPR joint strength with AZ31B pull-out failure mode. Salt fog corrosion testing (ASTM B-117) was performed to evaluate the corrosion performance of the uncoated F-SPR joint. The steel rivet fell between the AZ31B (active) and the thermoset CFRP (noble).

As expected, AZ31B was found to be the more » most active, while thermoset CFRP was the most noble. Corrosion potential was measured for each material to establish the galvanic corrosion characteristics. All F-SPR samples showed pull-out of AZ31B after mechanical testing, indicating good mechanical interlocking between the steel rivet and AZ31B. An average lap shear tensile load of 5.18 kN was achieved, while an average of 2.81 kN was found from cross-tension testing. Lap shear tensile and cross-tension testing were used to evaluate the mechanical joint performance. In the present work, thermoset carbon fiber–reinforced polymer (CFRP) was spot joined to magnesium alloy AZ31B by a friction self-piercing riveting (F-SPR) process. However, steel rivet was not significantly corroded due to sacrificial anode effect by which AZ31B corroded first in the galvanic couple. With up to 200 h of exposure, the post-corroded F-SPR joint integrity retained 81.2% of the pre-exposure F-SPR joint strength with AZ31B pullout failure mode. As expected, AZ31B was found to be more » the most active, while thermoset CFRP was the most noble.

All F-SPR samples showed a pullout of AZ31B after mechanical testing, indicating good mechanical interlocking between the steel rivet and AZ31B.

Cain sheet metal scribe