Additive manufacturing (AM) allows for product development with light weight, fewer machining constraints, and reduced costs depending on the application. While AM is an emerging field, there is limited research on the use of AM for pressure vessels or implementation in high stress environments. Depending on the design approach and limitations of traditional material-removal fabrication techniques, AM parts can achieve high strength-to-weight ratios with reduced manufacturing efforts. Coupling AM with alternative metal and composite materials allows for unique designs that have high strength-to-weight ratios for pressure-based applications. The Johns Hopkins University Applied Physics Laboratory (JHU/APL) has conducted research on a number of these composite designs, focusing on the use of carbon fiber or metal plating with the AM materials.
Before implementing AM in field tested prototypes, JHU/APL performed strength limitation tests on AM pressure vessels (PVs) in the laboratory to prove their effectiveness. PVs constructed with varying thicknesses and coating techniques were divided into three groups, each with a uniform wall thickness that provided a congruent surface area to withstand higher pressures. These PVs were then paired with one of three coating/plating technologies, forming a trade matrix of varying AM thicknesses and plating techniques. Once fabricated and plated, these test PVs were hydro-statically tested at increasing pressure levels. This pressure testing demonstrates that the use of AM to create PVs, when paired with specific plating techniques, can result in structures with significant strength capabilities at lighter than normal PV weights.
Furthermore, JHU/APL has begun to test the AM PVs in a number of research projects. Such testing is desired because these unique parts can be easily manufactured in shapes and volumes that were previously unattainable through common manufacturing techniques. AM parts are now commonly used in air-frames; however, in higher pressure underwater scenarios AM’s capabilities are unproven. JHU/APL has begun to apply this new and emergent field to the effective design of AM PVs, which can play a significant role in the field of underwater vehicles and similar projects.
