US4621980A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fiber reinforced composite spar for a rotary wing aircraft
Assignee: RTX Corp
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Filing: 1984-09-19
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Granted: 1986-11-11
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Expires: 2004-09-19
Abstract
Abstract The present invention discloses a damage tolerant composite article comprising a plurality of layers of both graphite and polyaramide fibers. The graphite fiber layers are oriented at angles of about ±30° and about ±15° to the longitudinal axis while the polyaramide fiber layers are oriented at about ±14° to the longitudinal axis. Composite structures of this construction will have increased damage tolerance while maintaining the required bending and torsional stiffness.
Inventors
- 👤 Richard T. Reavely
- 👤 David N. Schmaling
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 16:19
CPC Classifications
A; A01; A01K; A01K87/00; B; B64; B64C; B64C27/00; B64C27/32; B64C27/46; B64C27/473; B64C2027/4733; B64C2027/4736; Y; Y10; Y10S; Y10S428/00; Y10S428/902; Y10T; Y10T428/00; Y10T428/13; Y10T428/1352; Y10T428/1369; Y10T428/24; Y10T428/24058; Y10T428/24124; Y10T428/30; Y10T428/31504; Y10T428/31511
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
82 words
A composite spar for a rotary wing aircraft blade comprising: a plurality of layers of graphite and polyaramide fibers wherein the layers of graphite fibers are oriented at about ±30° to about ±40° and about ±12° to about ±16° to the longitudinal axis of the structure and the polyaramide fibers are oriented at about ±12° to about ±16° to the longitudinal axis and said matrix is a thermosetting resin, wherein the concentration of polyaramide fibers is greater than 25 percent by weight.
Claim 2
Dependent Claim
82 words
A composite spar for a rotary wing aircraft blade comprising: a plurality of layers of graphite and polyaramide fibers wherein the layers of graphite fibers are oriented at about ±30° to about ±40° and about ±12° to about ±16° to the longitudinal axis of the structure and the polyaramide fibers are oriented at about ±12° to about ±16° to the longitudinal axis and said matrix is a thermosetting resin, wherein the concentration of polyaramide fibers is greater than 25 percent by weight.
Claim 3
Dependent Claim
68 words
A composite spar for a rotary wing aircraft blade comprising: a plurality of alternating layers of graphite and polyaramide fibers wound about a central axis, wherein the graphite fiber layers are oriented from about ±30° to about ±40° and from about ±10° to about ±20° and the polyaramide fibers are oriented from about ±12° to about ±16° to a longitudinal axis and said matrix is a thermosetting resin.
Claim 4
Dependent Claim
68 words
A composite spar for a rotary wing aircraft blade comprising: a plurality of alternating layers of graphite and polyaramide fibers wound about a central axis, wherein the graphite fiber layers are oriented from about ±30° to about ±40° and from about ±10° to about ±20° and the polyaramide fibers are oriented from about ±12° to about ±16° to a longitudinal axis and said matrix is a thermosetting resin.
Claim 5
Dependent Claim
69 words
The article of claim 1 having 17 layers of fiber reinforcement wherein layers 1, 4, 7, 10, 13 and 17 comprise graphite fibers oriented at about ±35° to the longitudinal axis, layers 2, 3 and 16 comprise graphite fibers oriented at about ±15° to the longitudinal axis and layers 5, 6, 8, 9, 11, 12, 14 and 15 comprise polyaramide fibers oriented at about ±14° to the longitudinal axis.
Claim 6
Dependent Claim
23 words
The article of claim 2 wherein the matrix material comprises about 40 percent to about 60 percent by volume of a thermosetting epoxy.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-11-10 | 1990-05-12 | 1990-11-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-11-10 | 1994-05-12 | 1994-11-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-11-10 | 1998-05-12 | 1998-11-11 | $7700.00 | Window Closed / Lapsed |