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Acoustically tailored composite rotorcraft fuselage panels
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | May, Carl Hambric, Stephen Kendrick, Phil Lee, Edward Wess Sr., Denis Cai, Liang-Wu Koudela, Kevin Shepherd, Micah Snider, Royce |
| Copyright Year | 2015 |
| Description | A rotorcraft roof sandwich panel has been redesigned to optimize sound power transmission loss (TL) and minimize structure-borne sound for frequencies between 1 and 4 kHz where gear meshing noise from the transmission has the most impact on speech intelligibility. The roof section, framed by a grid of ribs, was originally constructed of a single honeycomb core/composite face sheet panel. The original panel has coincidence frequencies near 700 Hz, leading to poor TL across the frequency range of 1 to 4 kHz. To quiet the panel, the cross section was split into two thinner sandwich subpanels separated by an air gap. The air gap was sized to target the fundamental mass-spring-mass resonance of the double panel system to less than 500 Hz. The panels were designed to withstand structural loading from normal rotorcraft operation, as well as 'man-on-the-roof' static loads experienced during maintenance operations. Thin layers of VHB 9469 viscoelastomer from 3M were also included in the face sheet ply layups, increasing panel damping loss factors from about 0.01 to 0.05. Measurements in the NASA SALT facility show the optimized panel provides 6-11 dB of acoustic transmission loss improvement, and 6-15 dB of structure-borne sound reduction at critical rotorcraft transmission tonal frequencies. Analytic panel TL theory simulates the measured performance quite well. Detailed finite element/boundary element modeling of the baseline panel simulates TL slightly more accurately, and also simulates structure-borne sound well.|||||||||||| |
| File Size | 10735879 |
| Page Count | 160 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20150013990 |
| Archival Resource Key | ark:/13960/t2k69gp6r |
| Language | English |
| Publisher Date | 2015-07-01 |
| Access Restriction | Open |
| Subject Keyword | Acoustics Damping Panels Honeycomb Cores Noise Reduction Structural Vibration Acoustic Propagation Roofs Acoustic Frequencies Sandwich Structures Static Loads Finite Element Method Sound Transmission Mathematical Models Fuselages Rotary Wing Aircraft Composite Structures Transmission Loss Frequency Ranges Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Technical Report |
