K. Johnson, D. White, Solidica, Inc., Ann Arbor, MI

Summary:

Manufacturing technology for continuous fiber reinforced (CFR) metal matrix composites (MMCs) remains a costly, low yield process, and has limited the use of high stiffness, lightweight materials such as aluminum matrix composites. An ultrasonic consolidation (UC) technique that is similar to composite tape lay up technology has been demonstrated. This “metal tape lay up” process has the potential to address many of the yield and affordability problems of current CFR MMC manufacturing processes. Recent experiments have shown that a wide range of fibers, including structural (SiC, B, glass), active (shape memory alloy wires), and sensing (optical fibers and wave guides) can be embedded in an aluminum alloy matrix. Some examples are shown in Figure 1-3 below.

Current research in this area is focused on the development of a fundamental understanding of the mechanics of metal flow around embedded fibers and characterization of the fiber-metal interface to optimize fiber density and the mechanic properties of the completed structure. Work in this area is focused on developing an elasto-plastic, time dependent three dimensional model of the process of metal deformation and consolidation around fibers using ultrasonic excitation. Some of the factors to be considered include material properties, yield stage and yield criterion, kmatic bilinear strain hardening after yield and complex end article geometries. Because of the flexibility of the metal tape lay up concept, new aerospace structural concepts incorporating low cost, local reinforcement can be enabled by this manufacturing approach. This talk will describe the ultrasonic consolidation technique for fiber embedding, provide examples of materials systems and interfacial behavior, and describe the fundamental mechanics of enhanced metal flow due to ultrasonic excitation, and how it affects continuous fiber embedding.