Structural panels for exposed surfaces

A method, comprising:

• determining a target acoustic profile of an aircraft based on an acoustic environment of an exterior surface of the aircraft during operation, the determining a target acoustic profile comprising:
• determining a target peak frequency;
• determining a target absorption coefficient;
• and
• determining a target frequency width;
• determining a plurality of metallic foam layer characteristics based on the target acoustic profile, the plurality of metallic foam layer characteristics comprising:
• a metallic foam layer composition;
• a metallic foam layer pore density;
• and
• a metallic foam layer thickness;
• determining a plurality of elastomer characteristics that will enhance the absorption of targeted acoustic energy corresponding to the target acoustic profile of the aircraft, wherein the plurality of elastomer characteristics are determined based on the target acoustic profile and the metallic foam layer characteristics, the plurality of elastomer characteristics comprising:
• an elastomer composition;
• and
• an elastomer saturation level;
• providing a metallic foam layer comprising the plurality of determined metallic foam layer characteristics, the metallic foam layer comprising a Poisson ratio of less than or equal to zero;
• depositing an elastomer having the determined elastomer composition into the provided metallic foam layer at the determined elastomer saturation level;
• determining a melamine foam layer comprising melamine foam based on the target acoustic profile;
• coupling the melamine foam layer to the metallic foam layer comprising the deposited elastomer;
• and
• coupling the melamine foam layer and the metallic foam layer comprising the deposited elastomer onto the exterior surface of the aircraft, wherein the melamine foam layer and metallic foam layer comprising the deposited elastomer absorbs acoustic energy corresponding to the target acoustic profile;
• wherein determining a plurality of elastomer characteristics comprises:
• selecting first and second elastomers based on the target acoustic profile and the determined plurality of metallic foam layer characteristics;
• and
• selecting a ratio between the first and second elastomers based at least on the target acoustic profile and the determined foam layer characteristics;
• and
• wherein depositing an elastomer comprises depositing the first and second elastomers.