Durability of Metal-Composite Friction Spot Joints under Environmental Conditions

• Published in: Materials Vol. 13; no. 5; p. 1144
• Main Authors: Goushegir, Seyed M, Scharnagl, Nico, Dos Santos, Jorge F, Amancio-Filho, Sergio T
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 04-03-2020; MDPI
• Subjects: Aging; Aging (natural); Aluminum; Aluminum alloys; Bond strength; Bonding strength; Carbon fibers; Chemical bonds; Conversion coating; Durability; fiber reinforced composites; Friction; friction spot joining; Humidity; Hydration; Investigations; mechanical properties; Microscopy; Moisture absorption; outdoor environmental durability; Penetration; Phosphoric acid; Polymers; Pretreatment; Primers (coatings); Sandblasting; Shear strength; Spectrum analysis; Weathering; friction spot joining; outdoor environmental durability; aging; aluminum alloys; fiber reinforced composites; mechanical properties
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma13051144

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.