NASA's Langley Research Center has developed an enhanced design for a composite panel with a recessed core. NASA designed it to decrease the radiation efficiency and increase the transmission loss while maintaining load-bearing capability so it could be used in applications such as aircraft floors. Similar to traditional composite panels, the innovation possesses low weight characteristics, but in addition, it can be used in load-bearing applications. The invention was developed for NASA's Quiet Aircraft Technology Program. The superior design of the composite panel can be used in a wide variety of commercial applications wherever honeycomb is needed and improved acoustics are desired. NASA has patented and tested the novel design, and is interested in attracting development partners and potential licensees for the recessed core composite panel design.
This method constructs recessed core composite panels to reduce unacceptable noise radiated by the existing composite panels. Composite panels are widely used in aerospace applications, and like most lightweight, stiff materials, they efficiently radiate sound, resulting in high noise levels in an enclosed area. Conventional noise treatments add weight to a vehicle, which negates some of the benefits of using composite panels.
The innovation is a variation on a voided core for reduced sound radiation in composite panels. A voided core is made by removing the core material in select areas. This creates a double-wall cavity, which increases transmission loss, but weakens the panel. In the recessed core, only a portion of the honeycomb is removed through the thickness. Both of these methods decrease wave speed by reducing stiffness in portions of the panels. The lost stiffness is recovered by reinforcing the recesses with thin plates; in effect, creating interior face sheets. The reinforced recessed core improves transmission loss over the solid core design yet maintains panel strength. Optimization of the recess layout is possible for a particular application.