Structural composite material with improved acoustic and vibrational damping properties

1. A cured or uncured structural composite material comprising

a structural component in a form of a plurality of layers of textile that comprises structural fibers;

a thermosetting resin component; and

a viscoelastie interleaf positioned between a pair of adjacent layers of to tile, said viscoelastic interleaf comprising at least one thin layer of nonwoven material, which is comprised of thermoplastic elastomer fibers;

wherein the viscoelastic interleaf and structural component are partially or completely impregnated with the thermosetting resin component; and

wherein the resin component has a glass transition temperature T g that is higher than that of the viscoelastie interleaf, and

wherein the thermoplastic elastomer fibers in said nonwoven material are made of at least on polymer selected from the group consisting of styrenic thermoplastic elastomers, and a blend thereof.

2. The structural composite material as in claim 1 wherein the thermosetting resin component comprises an epoxy.

3. The structural composite material as in claim 1 wherein the structural fibers comprise carbon fibers.

4. The structural composite material of claim 1 wherein the viscoelastic interleaf is completely impregnated with the thermosetting resin component.

5. The structural composite material of claim 1 , wherein thermoplastic elastomer fibers in the nonwoven material are made of a styrenic thermoplastic elastomer which is a block copolymer having an elastomeric segment with a lower T g and styrenic segments with higher T g , and which forms a microphase separated structure at room temperature.

6. The structural composite material of claim 1 , wherein the viscoelastic interleaf has been treated by plasma to achieve a surface tension of at least 35 dyne/cm on both the sides.

7. A cured or uncured composite sandwich structure comprising

a first skin and a second skin; and

a honeycomb structure between the first skin and the second skin;

wherein each of the first and second skins comprises a plurality of layers of textile comprising structural fibers, an viscoelastie interleaf positioned between a pair of adjacent layers of the textile, and a thermosetting resin component,

wherein the viscoelastic interleaf comprises at least one thin layer of nonwoven material, which comprises thermoplastic elastomer fibers, and the thermosetting resin component has a glass transition temperature T g that is higher than that of the viscoelastie interleaf,

wherein the viscoelastic interleaf and the layers of textile are partially or completely impregnated with the thermosetting resin component, and

wherein the thermoplastic elastomer fibers of the nonwoven material are made of at least one polymer selected from the group consisting of: styrenic thermoplastic elastomers, and a blend thereof.

8. The cured or uncured composite sandwich structure as in claim 7 wherein the viscoelastic interleaf is coated at least on one side with a structural adhesive formulation.