UDRI began by determining the operational environment for the AV-8B engine inlet. Based on the operating environment, a commercial off the shelf damping material was selected for the application. The Navy conducted survivability tests on the damping material after exposure to various contaminants (jet fuel, salt water, etc.) at various temperatures. The damping material performed well under all conditions.

With a viable damping material identified, UDRI performed a series of finite element analyses to determine an optimal damping design. The resulting design is a constraining layer damping system consisting of 0.005 inch damping layer and a 0.030 inch primed aluminum constraining layer. The presence of the constraining layer enhances the effectiveness of the damping system. The damping material is self-adhesive at room temperature, which facilitates application to the existing structure.

As depicted in Figure 4, the Navy provided UDRI with an AV-8B test article upon which to demonstrate the damping effectiveness. UDRI began by testing the existing structure to determine the frequencies and damping in the current engine inlet. This data was utilized to correlate and refine the finite element model. Both the analysis and testing indicate that most of the engine inlet ring is relatively highly damped as currently fielded. However, there are a few modes that have much higher response levels. Excitation of these particular modes is believed to be the primary cause of the cracking problem in the engine inlet ring. Reducing the vibratory stresses from these modes is the goal for the damping design.