Vibration damping structures
A vibration damping body including an auxetic cellular structure having cell walls therein formed substantially of a first material having a first stiffness, the cellular structure further including a second material attached to said cell walls, the second material being selectively located throughout the cellular structure so as to include less than 50% by mass thereof and having a second stiffness which is lower than said first stiffness.
1. A vibration damping body comprising an auxetic cellular structure having cell walls defining a plurality of adjoining cells therein, said cell walls being formed substantially of a first material having a first stiffness, the cellular structure further comprising a second material attached to said cell walls, the second material being selectively located throughout the cellular structure so as to comprise less than 50% by mass thereof and having a second stiffness which is lower than said first stiffness, wherein
individual cells are polygonal in section in relation to a longitudinal axis of the cell structure and include acute vertices, and the second material is provided in the form of fillets in at least some of the acute vertices.
2. The body according to claim 1 , wherein the second material comprises less than 30% by mass of the cellular structure.
3. The body according to claim 1 , wherein the second material occupies less than 50% by volume of the cellular structure including voids therein.
4. The body according to claim 1 , wherein the cell walls are angled such that each cell in section takes the form of a re-entrant polygon in relation to a longitudinal axis of the cell structure.
5. The body according to claim 1 , wherein the second material is attached between adjoining cell walls of adjacent cells within the cellular structure.
6. The body according to claim 5 , wherein the second material forms a layer between the adjoining cell walls of adjacent cells.
7. The body according to claim 1 , wherein the second material is an elastomer.
8. The body according to claim 1 , wherein the first material is a polymer.
9. The body according to claim 1 , wherein the second material is selectively positioned at predetermined locations in the cellular structure at which strain is predetermined to be greatest in use.
10. The body according to claim 1 , comprising opposing outer walls, the cellular structure being constrained between said outer walls.
11. The body according to claim 1 , comprising a blade.
12. The body according to claim 1 , wherein the second material occupies less than 30% by volume of the cellular structure including voids therein.
13. The body according to claim 1 , wherein the second material occupies less than 20% by volume of the cellular structure including voids therein.
14. The body according to claim 1 , wherein the second material occupies less than 10% by volume of the cellular structure including voids therein.
15. The body according to claim 1 , wherein the second material comprises less than 20% by mass of the cellular structure.
16. A method of manufacturing a vibration damping body, comprising:
forming substantially of a first material an auxetic cellular structure having cell walls defining a plurality of adjoining cells therein, said first material having a first stiffness, and
bringing a second material into a binding relationship with said first material at selective locations within the cellular structure, such that the second material comprises less than 50% by mass of said cellular structure, said second material having a second stiffness which is lower than said first stiffness, wherein
individual cells are polygonal in section in relation to a longitudinal axis of the cell structure and include acute vertices, and the second material is provided in the form of fillets in at least some of the acute vertices.
17. The manufacturing method according to claim 16 , wherein the first and second material portions of said cellular structure are co-formed.
18. The manufacturing method according to claim 16 , wherein the second material is bonded to the cell walls of said cellular structure.
19. The manufacturing method according to claim 16 , wherein the first and/or second material portions are formed by a moulding process.
20. A vibration damping body comprising an auxetic cellular structure having cell walls defining a plurality of adjoining cells therein, said cell walls being formed substantially of a first material having a first stiffness, the cellular structure further comprising a second material attached to said cell walls, the second material being selectively located throughout the cellular structure so as to comprise less than 50% by mass thereof and having a second stiffness which is lower than said first stiffness, wherein
the second material is attached between adjoining cell walls of adjacent cells within the cellular structure.
21. A method of manufacturing a vibration damping body, comprising:
forming substantially of a first material an auxetic cellular structure having cell walls defining a plurality of adjoining cells therein, said first material having a first stiffness, and
bringing a second material into a binding relationship with said first material at selective locations within the cellular structure, such that the second material comprises less than 50% by mass of said cellular structure, said second material having a second stiffness which is lower than said first stiffness, wherein
the second material is attached between adjoining cell walls of adjacent cells within the cellular structure.