Durability of Metal-Composite Friction Spot Joints under Environmental Conditions

Abstract

The current paper investigates the durability of the single-lap shear aluminum-composite friction spot joints and their behavior under harsh accelerated aging as well as natural weathering conditions. Four aluminum surface pre-treatments were selected to be performed on the joints based on previous investigations; these were sandblasting (SB), conversion coating (CC), phosphoric acid anodizing (PAA), and PAA with a subsequent application of primer (PAA-P). Most of the pre-treated specimens retained approximately 90% of their initial as-joined strength after accelerated aging experiments. In the case of the PAA pre-treatment, the joint showed a lower retained strength of about 60%. This was explained based on the penetration of humidity into the fine pores of the PAA pre-treated aluminum, reducing the adhesion between the aluminum and composite. Moreover, friction spot joints produced with three selected surface pre-treatments were held under outside natural weathering conditions for one year. PAA-P surface pre-treated specimens demonstrated the best performance with a retained strength of more than 80% after one year. It is believed that tight adhesion and chemical bonding reduced the penetration of humidity at the interface between the joining parts.

Feasibility study of friction stir joining of aluminium with carbon fibre reinforced thermoplastic composite

“…Main characteristics are mentioned as viscosity of polymer, cooling rate and aluminium surface structure that may prevent full interface wetting, including insufficient sealing against the environment. 47 Pre-treatment with phosphoric acid anodizing and subsequent application of primer enabled the best performance in ultimate lap shear strength (ULSS) after one year of natural aging (more than 80% of initial ULSS). More than doubled reduction in global mechanical static performance were reported for samples that were pre-treated by conversion coating and sandblasting, reaching 57% and 59% respectively of the initial ULSS.…”

“…45,46 Besides the polymeric film, also the surface pretreatment has a relevant influence on the joint aging behavior. Goushegir et al 47 concluded that during accelerated aging of FSpJ joints the complete wetting of aluminium surface with molten polymer hinders the moisture diffusion into the joint interface. Main characteristics are mentioned as viscosity of polymer, cooling rate and aluminium surface structure that may prevent full interface wetting, including insufficient sealing against the environment.…”

Evaluation of Joint Strength for CFRPs and Aluminum Alloys by Friction Stir Spot Welding Using Multi-Stage Heating

“…On the other hand, in the resin-to-metal FSSW process, frictional heat generated between the tool and the metal is used to heat the thermoplastic resin to its melting point. Some studies [10][11][12][13] have been conducted to apply FSSW to CFRTP-to-metal welding since heat and pressure can be applied simultaneously in a short time. Conventional equipment used for joining metallic materials can also be converted for this use.…”

Direct Bonding of Polymer and Metal with an Ultrahigh Strength: Laser Treatment and Mechanical Interlocking

“…In the past, the PMH was generally fabricated with traditional bonding, but the poor bonding strength, high cost, and complicated procedures inevitably limit its application. [ 8–12 ]…”