마찰교반점용접을 이용한 Al-CFRP 용접부의 부식 특성

Abstract

Lightweight material is applied to cope with intensive environmental regulations. Initial research is focused on the mono-metallic metals such as strengthening the rigidity of steel materials and improving methods of welding and joining. BIW (Body-in-White) has been studied to improve lightweight method using dissimilar materials between steel and non-ferrous metal. Lightweight vehicle is required crash stability, tensile strength and reliability for developing the hybrid electric, hydrogen electric vehicles. Therefore, Automobile company has to be satisfied with environmental regulations and also developing the MMI(Multi Material Integration) method, which is a lightweight technology applied to polymer materials.

Aluminum has a specific strength, corrosion resistance and recyclability comparing with steel. By replacing steel to aluminum, it is possible to reduce vehicle’s weight about 45%. CFRP(Carbon Fiber Reinforced Plastic) is focused on the next-generation lightweight material and it has excellent mechanical performance about 60% weight and 5 times higher strength compared to aluminum.

However, it is difficult to secure high-strength and stable joints by using the conventional Arc welding. Mainly, reason is a difference of material properties in each’s. Therefore, various welding and joining methods have been studied to overcome the difference in physical properties between Al alloy and CFRP. Mechanical fastening: SPR (Self Piercing Rivet) has reported to have problems such as lowering of impact stability and corrosion. Other metod: FSJ(Friciton Stir Joining) is a low heat input solid state welding, easy to secure the strength and quality when joining dissimilar materials. Especially, it is necessary to study the quality and reliability of joints by comparing each material with each’s process parameters.

Therefore, this paper aim to secure the quality’s assurance and reliability of joints by comparing with each process parameter and tensile shear strength of Friction spot joints of Al 5052-H32 and CFRP(PA66).

As a result, considered by process parameters. The deeper tool’s plunge depth is (0.2 → 0.3 mm), suppressing force is increased. It is contributed the suppression of expanding bubbles & micro-crack. The more increased the tool’s dwell time(10, 15, 20 s) is, heat input is increased at the interface. This is affected the formation of micro-cracks and the growth of gap. Lastly, The faster the tool’s rotation speed is, the interlocking area is expand.

Maximum tensile shear strength of 3.1 kN is obtained at this parameters (plunge depth: 0.3 mm, dwell time: 10 s, rotation speed: 500 rpm) without deformation and fracture.