Formable constraining layer system

(54) FORMABLE CONSTRAINING LAYER SYSTEM

(75) Inventors: R. Craig Virnelson, Chesterland;

Jeffrey J. Schroeder, Cleveland;
Maurice E. Wheeler, Ashtabula, all of
OH (US)

(73) Assignee: Soundwich, Inc., Cleveland, OH (US)

( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.

(21) Appl. No.: 09/237,606

(22) Filed: Jan. 25, 1999

Related U.S. Application Data

(60) Provisional application No. 60/072,600, filed on Jan. 26, 1998.

(51) Int. CI.7 B32B 27/04; B32B 27/12;

B32B 5/02

(52) U.S. CI 442/104; 442/173; 442/175;

442/327; 442/328; 442/374; 442/375

(58) Field of Search 442/104, 71, 72,

442/74, 173, 175, 327, 328, 374, 375

(56) References Cited

U.S. PATENT DOCUMENTS

4,311,751 1/1982 Braeggemann et al. .

4,766,028 * 8/1988 Rich 428/253

4,803,105 2/1989 Kretow et al. .

4,842,938 6/1989 Rizk et al. .

5,160,783 11/1992 Nemoto et al. .

5,487,928 1/1996 Fujimoto .

5,578,800 * 11/1996 Kijima 181/171

5,858,521 * 1/1999 Okuda et al 428/219

OTHER PUBLICATIONS

Thiokol Propulsion, TCRTM (Composite Resin System), 1998, pp. 1-7.

* cited by examiner

Primary Examiner—Terrel Morris

Assistant Examiner—Norca L. Torres

(74) Attorney, Agent, or Firm—Pearne & Gordon LLP

(57) ABSTRACT

A vibration-damping laminate having a constraining layer secured to a viscoelastic layer. The constraining layer includes a mat of non-thermoplastic fibers. The viscoelastic layer includes a thermoplastic elastomer.

16 Claims, 1 Drawing Sheet

1

FORMABLE CONSTRAINING LAYER
SYSTEM

CROSS-REFERENCE TO RELATED
APPLICATION

This application claims the benefits of U.S. Provisional Application No. 60/072,600, filed Jan. 26, 1998.

BACKGROUND OF THE INVENTION

This invention relates to vibration-damping materials, and in particular to vibration-damping laminates having constraining layers.

A structure that is under the influence of internal and/or external forces, such as an automobile panel, tends to vibrate and produce undesirable noise. It is known to reduce the vibration of the structure by attaching a vibration-damping material to the structure. The vibration-damping material often consists of a single layer of a viscoelastic material, such as asphalt or rubber. It has been found particularly useful, however, to use a laminate as the vibration-damping material, wherein the laminate includes a viscoelastic layer and a constraining layer with a high Young's modulus. Such a constraining layer increases the damping effect of the laminate, and supports and protects the viscoelastic layer and the structure. Conventionally, the constraining layer is composed of metal because metal has a high Young's modulus.

Although a laminate with a metal constraining layer provides numerous advantages, such a laminate also has disadvantages. A laminate with a metal constraining layer has increased weight, is harder to shape, is more expensive to produce, and is usually more expensive to install.

Based upon the foregoing, there is a need in the art for an improved vibration-damping laminate. The present invention is directed to such a laminate.

SUMMARY OF THE INVENTION

It therefore would be desirable, and is an advantage of the present invention, to provide a vibration-damping laminate having a constraining layer that includes non-thermoplastic fibers. A viscoelastic layer is secured to the constraining layer. In one embodiment, the viscoelastic layer includes a thermoplastic elastomer. In another embodiment, the viscoelastic layer includes a blowing agent.

Also provided in accordance with the present invention is a method of damping a structure having a surface with a depression formed therein. A laminate is provided that includes a constraining layer secured to a viscoelastic layer. The constraining layer includes non-thermoplastic fibers. The viscoelastic layer includes a thermoplastic elastomer and a blowing agent. The viscoelastic layer is secured to the surface of the structure, over the depression. The laminate is then heated to activate the blowing agent, thereby causing the viscoelastic layer to expand into the depression.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

FIG. 1 shows a schematic view in cross-section of a laminate;

FIG. 2 shows a schematic view in cross-section of the laminate secured to a structure;

2

FIG. 3 shows a schematic view in cross-section of the laminate secured to a second structure with a depression; and

FIG. 4 shows a schematic view in cross-section of the 5 laminate expanded to extend into the depression.

DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS OF THE
INVENTION

10 It should be noted that parts are parts by weight and percents are weight percents unless otherwise indicated or apparent. In addition, when a preferred range such as 5-25 is given, this means preferably at least 5 and preferably not more than 25.

15 As used herein, the term "thermoplastic" means capable of being repeatedly softened by an increase in temperature and hardened by a decrease in temperature.

As used herein, the term "thermoset resin" means a polymer resin that, when cured by application of heat or

20 chemical means, changes into a substantially infusible and insoluble material.

As used herein a "prepreg" is a ready-to-mold material in sheet form that includes a layer of cloth, mat, fiber, or paper,

25 impregnated with resin.

Referring now to FIGS. 1 and 2, there is shown a vibration-damping laminate 10 embodied in accordance with the present invention. The laminate 10 is for attachment to a surface 16a of a structure 16, such as an automobile

30 panel (typically metal or plastic). The laminate 10 comprises a constraining layer 12 with first and second surfaces 12a, 12b, and a viscoelastic layer 14 with first and second surfaces 14a, 14b. The first surface 12a of the constraining layer 12 is secured to the first surface 14a of the viscoelastic

35 layer 14. Release liners 18 may be releasably secured to the second surfaces 12b, 14b of the constraining layer 12 and the viscoelastic layer 14 during storage of the laminate 10, prior to usage.

Preferably, the constraining layer 12 is comprised of a mat 4q or layer of fibers impregnated with a resin or other matrix material. Preferably, the constraining layer 12 is 10-40% by weight resin, with the remainder being fibers. In addition, the constraining layer 12 preferably has a weight of 10-50, more preferably 15-30, more preferably about 20, ounces 45 per square yard.

Preferably, the fibers are non-thermoplastic fiberglass fibers, carbon fibers, aramid fibers, keviar fibers, ceramic fibers, or combinations thereof. Less preferably, the fibers are other synthetic fibers. The fibers may be woven or 50 unwoven, but are preferably orientated in a plurality of directions.

Preferably, the resin is an epoxy resin. A heat-reactive curing agent may be mixed into the resin, suitable epoxy resins include bisphenol A-based epoxy resins, bisphenol

55 F-based epoxy resins, epoxodized novolac resins, and cycloaliphatic epoxides. Suitable curing agents include dicyandiamide, Lewis acids, and amine salts. Less preferably, the resin is another thermoset resin, or a thermoplastic resin. Suitable thermoset resins include:

60 crosslinked polyester resins, phenolic resins, ureaformaldehyde resins, and polyurethane resins.

Preferably, the constraining layer 12 is a prepreg sold by Thiokol Propulsion under the trade name TCR, and includes heavy weight glass fiber sold under the trade name E-Glass,

65 and an epoxy resin (with a heat sensitive curing agent) sold under the trade name UF3325; the resin content being about 34.5 percent (%).

In lieu of being a mat or layer of fibers impregnated with a resin, the constraining layer 12 may less preferably be comprised of a weave of non-thermoplastic fibers and thermoplastic fibers that is not impregnated with a resin binder or matrix, such a weave hereinafter being referred to as a "resinless weave". Preferably each strand in the resinless weave has non-thermoplastic fibers commingled with thermoplastic fibers. The non-thermoplastic fibers may be composed of non-thermoplastic fiberglass fibers, carbon fibers, aramid fibers, kevlar fibers, ceramic fibers, or combinations thereof. Preferably, the thermoplastic fibers comprise 10-40% by weight of the resinless weave.

When the resinless weave is heated, such as by baking, the thermoplastic fibers melt around the non-thermoplastic fibers. Upon cooling, the thermoplastic fibers solidify, thereby forming a solid matrix that encases the nonthermoplastic fibers. A preferred resinless weave is Twintex T44EP (e-glass and polypropylene, 44 ounces per square yard) or other Twintex product from Vetrotex CertainTeed Company. The resinless weave is preferably 10-50, more preferably 15-30, more preferably about 20, ounces per square yard.

The viscoelastic layer 14 is preferably comprised of a thermoplastic elastomer. The preferred formulation (Formulation 1) for the viscoelastic layer 14 is as follows:

Formulation 1

In Formulations 1, 2, and 4, the thermoplastic elastomer "A" is preferably a styrene-isoprene block copolymer sold by the Kuraray Company under the trade name VS-1. Less preferably, thermoplastic elastomer "A" is a linear styreneisoprene-styrene block copolymer sold by the Shell Chemi

45 cal Company under the trade name Kraton D 1107. Still less preferably, thermoplastic elastomer "A" is another styrene copolymer sold by the Shell Chemical Company under the "Kraton" family of trade names. Still less preferably, the thermoplastic elastomer "A" is another commercially avail

50 able thermoplastic elastomer or rubber.

In Formulation 1, the thermoplastic elastomer "B" is Kraton D 1107. Still less preferably, thermoplastic elastomer "B" is another styrene copolymer sold by the Shell Chemical Company under the "Kraton" series of trade names. Still less

55 preferably, the thermoplastic elastomer "B" is another commercially available thermoplastic elastomer or rubber.

In Formulations 2 and 4, the thermoplastic polymer is preferably an ethylene and vinyl acetate copolymer (EVA). Less preferably, the thermoplastic polymer is a polyvinyl

60 acetate, a polyethylene, an amorphous polypropylene, or another commercially available thermoplastic polymer.

In Formulations 1-4, the filler is preferably calcium carbonate (CaC03). Less preferably, the filler is carbon black, titanium dioxide, clay, talc, mica, glass microbubbles,

65 fumed silica, or other commercially available fillers.

In Formulation 4, the blowing agent is preferably azodicarbonamide. Less preferably, the blowing agent is 4,4'