Hybrid Aluminum-Lithium Fasteners for Composite Structure

Light weight hybrid aerospace fastening collars were manufactured from 2099 alloy which is a new generation Al-Li alloy developed by Alcoa. Designed as an alternative to conventional titanium lockbolt collars, the new collars combine a lightweight Aluminum-Lithium alloy with a stainless steel element. The collars studied in this work are lockbolt collars with a controlled swaging feature and are to be used in a fastener assembly with a threaded pin. 

The mechanical properties of hybrid collars were compared to standard collars made of incumbent alloys such as 2024 aluminum and 3Al-2.5V Titanium. It was found that the 2099 collars can provide a substantial weight saving and equivalent mechanical properties. In addition, the corrosion characteristics of the hybrid collars installed on a carbon fiber composite were studied using the salt spray testing. This paper presents the results obtained from the mechanical and corrosion testing of the hybrid collars along with the weight saving potentials of the new product.