On the Growth of Small Cracks in 2024-T3 and Boeing Space, Intelligence and Weapon Systems AM LPBF Scalmalloy®

Abstract

The desire to use additively manufactured (AM) parts to ensure the availability of military aircraft, and to build limited-life unmanned aerial vehicles (drones), coupled with the United States Air Force (USAF) approach to the airworthiness certification of AM parts has focused attention on durability analysis/assessment, and hence on the growth of small cracks in AM parts. Previous studies have shown that laser powder fusion built (LPBF) Scalmalloy® has: i) A yield stress and an ultimate strength that are greater than that of AA2024-T3 and comparable to that of AA7075-T6; ii) A resistance to crack growth that is better than that of AA7075-T6 and comparable to that of AA2024-T3. However, since the ability to predict the durability of a part is essential for its airworthiness certification, the present paper illustrates how to perform a linear elastic fracture mechanics (LEFM)-based durability assessment of Boeing Space, Intelligence and Weapon System (BSIWS) LPBF Scalmalloy®. The durability study includes specimens with both machined surfaces and surfaces left in the as-built condition. As a result, it would appear that BISWS AM LPBF Scalmalloy® is an ideal candidate for building limited-life AM replacement parts for fixed and rotary wing aircraft and drones.