# US 2010/0166568 A1 · Composite-Steel Hybrid Mast for Rotorcraft

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- Number: US 2010/0166568 A1
- Document ID: US20100166568A1
- Status: Published application
- Kind: A1
- Application number: 12/377,007
- Filed: 2007-08-15
- Published: 2010-07-01
- Earliest claimed: 2006-08-17
- Assignees: Bell Helicopter Textron Inc.
- Inventors: Sherman S. Lin
- Web page: https://patentgrep.com/patent/US20100166568A1

## CPC

- B64C 27/12: Rotor drives
- B64C 27/58: Transmitting means, e.g. interrelated with initiating means or means acting on blades (means acting on blades B64C27/72)
- Y02T 50/40: Weight reduction
- Y10S 416/50: Vibration damping features
- Y10T 428/1355: Elemental metal containing [e.g., substrate, foil, film, coating, etc.]
- Y10T 428/1359: Three or more layers [continuous layer]
- B64C: AEROPLANES; HELICOPTERS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A composite-steel hybrid mast for a rotorcraft includes a tubular, steel portion having an internal surface defining a space therein and a composite portion disposed within the space defined by the internal surface of the steel portion and held in a fixed spatial relationship with respect to the internal surface of the steel portion.

## Claims

### Claim 1

A composite-steel hybrid mast for a rotorcraft, comprising:
a tubular, steel portion having an internal surface defining a space therein; and
a composite portion disposed within the space defined by the internal surface of the steel portion and held in a fixed spatial relationship with respect to the internal surface of the steel portion.

### Claim 2 (depends on 1)

The composite-steel hybrid mast, according to claim 1, wherein the composite portion includes a fiber-reinforced, polymeric composite material and a polymer of the composite material adhesively bonds the composite portion to the internal surface of the steel portion.

### Claim 3 (depends on 1)

The composite-steel hybrid mast, according to claim 1, further comprising:
an adhesive disposed between the composite portion and the internal surface of the steel portion, such that the adhesive adhesively bonds the composite portion to the internal surface of the steel portion.

### Claim 4 (depends on 1)

The composite-steel hybrid mast, according to claim 1, wherein the internal surface of the steel portion defines at least one groove.

### Claim 5 (depends on 1)

The composite-steel hybrid mast, according to claim 1, wherein ends of the composite portion are filleted or tapered.

### Claim 6 (depends on 1)

The composite-steel hybrid mast, according to claim 1, wherein the steel portion and the composite portion are adapted to carry at least one of lift, thrust, torsion, and bending loads while in use.

### Claim 7 (depends on 1)

The composite-steel hybrid mast, according to claim 1, wherein the composite portion is adapted to carry a design limit load.

### Claim 8 (depends on 1)

The composite-steel hybrid mast, according to claim 1, wherein the mast is adapted for incorporation into one of a helicopter and a tiltrotor aircraft.

### Claim 9

A method for making a composite-steel hybrid mast for a rotorcraft, comprising:
providing a tubular, steel portion comprising an internal surface defining a space therein;
preparing a composite portion comprising a fiber-reinforced, polymeric, composite material on an expandable mandrel;
placing the expandable mandrel, with the composite portion thereon, into the space defined by the internal surface of the steel portion;
expanding the expandable mandrel;
curing the composite portion;
unexpanding the expandable mandrel; and
removing the expandable mandrel from the composite portion.

### Claim 10 (depends on 9)

The method, according to claim 9, wherein the expandable mandrel comprises:
an elastomeric material defining a balloon structure.

### Claim 11 (depends on 9)

The method, according to claim 9, wherein expanding the expandable mandrel is accomplished by introducing a fluid into the mandrel under pressure.

### Claim 12 (depends on 11)

The method, according to claim 11, wherein the fluid is a gas.

### Claim 13 (depends on 12)

The method, according to claim 12, wherein the gas is at least one of air and nitrogen.

### Claim 14 (depends on 11)

The method, according to claim 11, wherein unexpanding the mandrel is accomplished by withdrawing the fluid from the mandrel.

### Claim 15 (depends on 9)

The method, according to claim 9, further comprising:
machining at least one of a taper and a fillet at an end of the composite portion.

### Claim 16 (depends on 9)

The method, according to claim 9, further comprising:
treating the internal surface of the tubular, steel portion with a chemical agent to improve adhesive bonding;
applying an adhesive primer to the internal surface of the tubular, steel portion; and
applying at least one ply of adhesive film to the internal surface of the tubular, steel portion prior to placing the expandable mandrel and the composite portion into the space defined by the internal surface of the steel portion.

### Claim 17 (depends on 9)

The method, according to claim 9, wherein the expandable mandrel comprises:
a segmented, metallic mandrel.

### Claim 18 (depends on 17)

The method, according to claim 17, wherein expanding the expandable mandrel is accomplished by mechanically actuating segments of the segmented, metallic mandrel toward the internal surface of the tubular, steel portion.