Sonar dome

• US 20070230279A1
• Filed: 03/30/2006
• Published: 10/04/2007
• Est. Priority Date: 03/30/2006
• Status: Active Grant

• Current Assignee: Material Sciences Corporation (New Star Metals Holdings LLC)
• Original Assignee: Material Sciences Corporation (New Star Metals Holdings LLC)
• Inventors: Caiazzo, Anthony
• Granted Patent: US 7,408,842 B2
• Time in Patent Office: Days
• US Class Current: 367/188
• CPC Class Codes: G10K 11/02 Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators

Abstract

The Invention is a reinforced plastic sonar dome having a low acoustical insertion loss combined with sufficient mechanical strength. Acoustical and structural fibers are stochastically mixed and formed into a blended yarn. The blended yarn is woven into a blended fabric. The blended fabric is ordered into a stack having multiple layers of blended fabric. The blended fabric is incorporated into a polymer resin while the polymer resin is in liquid form using a vacuum assist. The acoustical fibers and the vacuum assist modify the acoustical properties of the resulting composite sonar dome.

Claims

1. A sonar dome to cover transducers of a sonar system of a vessel, the sonar dome comprising:

a. a solidified polymer resin, said solidified polymer resin defining an interior volume, said interior volume being configured to cover said transducers;

b. a substantially stochastic mixture of a plurality of acoustical fibers and a plurality of structural fibers, said stochastic mixture of said plurality of acoustical fibers and said plurality of structural fibers being imbedded within said solidified polymer resin, said acoustical fibers being selected to have a predetermined acoustical characteristic, said structural fibers being selected to have a predetermined structural characteristic.

2. The sonar dome of claim 1 wherein said predetermined acoustical characteristic of said plurality of said acoustical fibers comprises:

a one of said plurality of said acoustical fibers having an acoustical fiber speed of sound for a sound of a selected frequency propagating through said acoustical fiber, a one of said plurality of said structural fibers having a structural fiber speed of sound for said sound of said selected frequency propagating through said structural fiber, an absolute value of a difference between said acoustical fiber speed of sound and a speed of sound for said sound of said selected frequency propagating through water being less than said absolute value of said difference between said structural fiber speed of sound and said speed of sound for said sound of said selected frequency propagating through said water.

3. The sonar dome of claim 2 wherein the sonar dome has a predetermined design sound wavelength, said acoustical fibers having an acoustical fiber quantity, said structural fibers having a structural fiber quantity, said blended fabric having a predetermined ratio of said acoustical fiber quantity to said structural fiber quantity, said predetermined ratio being selected based upon said pre-determined design sound wavelength.

4. The sonar dome of claim 3 wherein said substantially stochastic mixture of said plurality of acoustical fibers and said plurality of structural fibers is arrayed in a blended yarn, said blended yarn is incorporated in a woven blended fabric, said blended fabric being imbedded within said solidified polymer resin.

5. The sonar dome of claim 4 wherein said blended fabric is one of a plurality of said blended fabrics, the sonar dome further comprising:

said plurality of said blended fabrics being formed into a multiple-layered stack of said blended fabrics, said stack of said blended fabrics being imbedded within said solidified polymer resin.

6. The sonar dome of claim 5 wherein each of said plurality of said blended fabrics within said stack has a one of a plurality of said ratios of said acoustical fiber quantity to said structural fiber quantity, said one of said plurality of said ratios being selected based upon a pre-determined design wavelength of said sound.

7. The sonar dome of claim 6 wherein said predetermined ratio of said acoustical fibers to said structural fibers for a one of said plurality of said blended fabrics is determined by a location of said one of said plurality of blended fabrics within said stack of said blended fabrics.

8. The sonar dome of claim 7 wherein said sonar dome has an inside surface and an outside surface, said ratio of said acoustical fiber quantity to said structural fiber quantity for said woven fabric proximal to said inside surface is greater than said ratio for said woven fabric distal to said inside and said outside surfaces, and said ratio of said acoustical fiber quantity to said structural fiber quantity for said woven fabric proximal to said outside surface is greater than said ratio for said woven fabric distal to said inside and said outside surfaces.

9. The sonar dome of claim 8 wherein said structural fiber is selected from a list consisting of carbon fiber, aramid and glass.

10. The sonar dome of claim 8 wherein said solidified polymer resin is a high-elongation resin.

11. The sonar dome of claim 8 wherein said acoustical fiber is selected from a list consisting of ultra-high molecular weight polyethylene fiber and polyester fiber.

12. The sonar dome of claim 1, said predetermined acoustical characteristic of said plurality of said acoustical fibers comprising:

said acoustical fibers having a speed of sound for frequencies between 1 kHz and 100 kHz of between 5000 m/sec and 10000 m/sec along the axis of the fiber and 1200 m/sec and 2000 m/sec transverse to the fiber length.

13. A sonar dome, the sonar dome comprising:

a. a plurality of acoustical fibers, said acoustical fibers being selected to have a predetermined acoustical characteristic;

b. a plurality of structural fibers, said structural fibers being selected to have a predetermined structural characteristic;

c. said plurality of said acoustical fibers and said plurality of said structural fibers being formed into a blended yarn, said blended yarn being formed into a blended fabric;

d. a solidified polymer resin, said blended fabric being incorporated within said solidified polymer resin.

14. The sonar dome of claim 13 wherein said blended yarn is formed of a mixture of said acoustical fibers and said structural fibers, said mixture of said acoustical fibers and said structural fibers being substantially stochastic.

15. The sonar dome of claim 14 wherein said predetermined acoustical characteristic of said acoustical fibers comprises:

a one of said plurality of said acoustical fibers having a speed of sound for propagation of a sound of a selected frequency through said acoustical fiber, said speed of sound for said sound of said selected frequency propagating through said acoustical fiber approximating said speed of sound for said sound of said selected frequency propagating through water.

16. The sonar dome of claim 15, the sonar dome further comprising:

a sonar window defined by said solidified polymer resin and by said blended fabric incorporated within said solidified polymer resin, said sonar window having a predetermined design wavelength of said sound, said blended fabric having a predetermined ratio of said acoustical fibers to said structural fibers, said predetermined ratio being selected based upon said pre-determined design wavelength of said sound.

17. The sonar dome of claim 16 wherein said window has a thickness, an inside surface and an outside surface, the sonar dome further comprising:

said blended fabric being a one of a plurality of said blended fabrics, said plurality of said blended fabrics being formed into a multiple-layered stack of said blended fabrics, said stack of said blended fabrics being incorporated within said solidified polymer resin, each of said plurality of said blended fabrics within said stack having a one of a plurality of said predetermined ratios of said acoustical fibers to said structural fibers, said one of said plurality of said predetermined ratios of said acoustical fibers to said structural fibers for said one of said plurality of said blended fabrics being determined by a location of said one of said plurality of blended fabrics within said stack of said blended fabrics.

18. The sonar dome of claim 17 wherein a one of said plurality of said blended fabrics located proximal to said inside surface of said window exhibits said predetermined ratio of said acoustical fibers to said structural fibers that is lower than said predetermined ratio exhibited by another one of said plurality of said blended fabrics that is located distal to said inside surface and said outside surface of said window, and another one of said plurality of said blended fabrics located proximal to said outside surface of said window exhibits said predetermined ratio of said acoustical fibers to said structural fibers that is lower than said predetermined ratio exhibited by another one of said plurality of said blended fabrics that is located distal to said inside surface and said outside surface of said window.

19. The sonar dome of claim 15 wherein said structural fiber has a structural fiber modulus of elasticity and wherein said acoustical fiber has an acoustical fiber modulus of elasticity, said structural fiber modulus of elasticity being greater than said acoustical fiber modulus of elasticity.

20. The sonar dome of claim 19 wherein said structural fiber is selected from the list consisting of carbon fiber, aramid fiber and glass fiber.

21. The sonar dome of claim 14, said predetermined acoustical characteristic of said plurality of said acoustical fibers comprising:

said acoustical fibers having a speed of sound for frequencies between 1 kHz and 100 kHz of between 5000 m/sec and 10000 m/sec along the axis of the fiber and 1200 m/sec and 2000 m/sec transverse to the fiber length.

22. A method for making a sonar dome, the method comprising:

a. mixing a predetermined quantity of acoustical fibers and a predetermined quantity of structural fibers to form a substantially stochastic fiber mixture having a predetermined ratio of said acoustical fibers to said structural fibers;

b. incorporating a polymer resin into said fiber mixture when said polymer resin is in a liquid form by applying means to reduce or avoid an air bubble or a void within said polymer resin by an amount sufficient to achieve a desired acoustical property when said polymer resin is in a solid form.

23. The method of claim 22, the method further comprising:

b. creating a blended yarn from said fiber mixture;

c. weaving a blended fabric of said blended yarn;

d. said step of incorporating said polymer resin into said fiber mixture comprising applying a partial vacuum to draw said polymer resin in said liquid form into said blended fabric.

24. The method of claim 23 wherein said fiber mixture is one of a plurality of said fiber mixtures, the method further comprising:

a. creating a plurality of said blended yarns from said plurality of said fiber mixtures;

b. creating a plurality of said blended fabrics from said plurality of said blended yarns;

c. stacking said plurality of blended fabrics to form a blended fabric stack;

d. said step of incorporating said polymer resin into said blended fabric comprising incorporating said polymer resin into said blended fabric stack.

25. The method of claim 24 wherein each of said plurality of fiber mixtures has a ratio of said acoustical fibers to said structural fibers and wherein each of said fabrics exhibits a one of said plurality of said ratios of said acoustical fibers to said structural fibers, the method further comprising:

a. said step of stacking said plurality of said blended fabrics comprising ordering said plurality of said blended fabrics based upon said ratio of said acoustical fibers to said structural fibers exhibited by each of said plurality of blended fabrics, and stacking said ordered plurality of said blended fabrics to form a blended and ordered stack;

b. said step of incorporating said polymer resin into said blended stack comprising incorporating said polymer resin into said blended and ordered stack.

26. The method of claim 25 wherein the sonar dome has an inside surface and an outside surface, said step of ordering said plurality of blended fabrics based upon said ratio of said acoustical fibers to said structural fibers exhibited by each of said plurality of said blended fabrics comprises:

ordering said blended fabric such that said ratio of said acoustical fiber to said structural fiber for a one of said plurality of said blended fabrics proximal to said inside surface is greater than said ratio for a one of said plurality of said blended fabrics distal to said inside and said outside surface, and ordering said blended fabric such that said ratio of said acoustical fiber to said structural fiber for another one of said plurality of said blended fabrics proximal to said outside surface is greater than said ratio for a one of said plurality of said blended fabrics distal to said inside and said outside surface.