Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Noninterengaged fiber-containing paper-free web or sheet...
Reexamination Certificate
2000-02-17
2003-07-15
Dixon, Merrick (Department: 1774)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Noninterengaged fiber-containing paper-free web or sheet...
C428S293100, C428S297400, C428S298100, C428S301400, C428S332000, C428S364000, C428S374000, C428S375000, C428S396000
Reexamination Certificate
active
06592979
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention concerns hybrid matrix fiber composites having improved compressive performance suitable for compression-critical applications as well as improved stiffness, toughness, and durability. The composites are fabricated by hybridization of two matrix materials. In particular, the invention concerns the composites comprised of a component fabricated from a plurality of fibers positionally aligned into a tape and impregnated with a first matrix material cured or otherwise solidified to appropriate stiffness and compression strength, and from the tape embedded in and surrounded by a second matrix material that acts as a binder to hold the tape together and is cured to appropriate toughness. The composite is used alone, or in combination or laminated with other structural materials. The invention further concerns a method and process for fabrication of the hybrid matrix fiber components.
2. Background Art and Related Art Disclosures
In aerospace, transportation, military and other industries, there is a continuous need for lightweight and durable structures having high performance in compression-critical applications, for construction and protection of various articles and structures, for insulation and for other uses.
At present, nearly all fiber composite materials are fabricated using multi-filament fiber tows and at most a single matrix material. The tows are comprised of thousands of filaments having diameters in the range of 5 &mgr;m to 100 &mgr;m and typically 5 &mgr;m to 15 &mgr;m. Processes used to fabricate useful structures from fiber composites typically involve placement (“impregnation”) of a single matrix material precursor within and between the fiber tows. The flow of the matrix material precursor between filaments and around tows can lead to the formation of microstructural defects such as poor filament distribution and poor fiber alignment. Where composite fibers are not aligned, the composite lacks the maximum achievable stiffness and compression strength.
Various fiber-reinforced materials have been available and previously disclosed. However, these materials are made of a single matrix, at most, and, thus, may possess the undesirable defects and properties just described.
Several-fiber-reinforced articles of manufacture include only a single matrix surrounding the reinforcement fibers. For example, in U.S. Pat. No. 4,764,397, a fiber composite is formed by applying a matrix consisting of a blend (mixture) of aromatic and thermoplastic polymers to reinforcing fibers and the plastic matrix is cross-linked. U.S. Pat. No. 5,324,563 describes composite rods comprised of carbon fiber and a single, fully cured or solidified, matrix material. This material seems to have enhanced compressive strength but has not-enhanced toughness. The described rods are pultruded shaped composites of relatively large circular cross-section and these are primarily used as a structural member but not as a form of reinforcement to be bonded together.
In some fiber-reinforced articles of manufacture, the fiber-matrix composition is covered with layers of other materials. U.S. Pat. No. 5,085,928 concerns a fiber reinforced composite matrix consisting of unidirectional fibers alternating with porous spunlaced fibrous layers. All of the layers are embedded in a thermoplastic resin. Similarly, U.S. Pat. No. 4,532,169 discloses fiber matrix layers that are placed in contact with other layers of fibrous material. In this patent, high-performance fiber ribbons are impregnated with a single matrix material that is not cured or solidified while the fiber is tensioned.
U.S. Pat. No. 4,992,318 describes ceramic matrix composite products made of long reinforcing fiber layers and short reinforcing chopped fiber or particulate layers. The layers are placed in alternating arrangement to provide both high interlaminar shear strength and also high transverse strength. While the layered configuration of these fiber articles seems to provide enforced toughness, it does not provide enhanced compressive strength and stiffness.
All the above cited patents concern single matrix composites which do not provide the needed combination of durability, stiffness, and compressive performance for many structural applications.
It is, therefore, a primary object of this invention to provide a lightweight, rigid, strong, tough, stiff and durable material able to withstand high compressionstresses. The fiber composite according to the invention has all of the described properties.
All publications, patents and patent applications cited in the specification are hereby incorporated by reference in their entirety.
SUMMARY OF THE INVENTION
One aspect of the current invention concerns hybrid matrix fiber composites having improved compressive performance suitable for compression-critical applications as well as improved toughness, stiffness, and durability. The composites are produced by hybridization of two matrix materials wherein a component fabricated from a plurality of fibers positionally aligned into a ribbon, i.e., a sheet-like or ribbon-like shaped composite, is impregnated with a first matrix material and cured or otherwise solidified to appropriate stiffness and compression strength, and the ribbons are then coated by a second matrix material acting as a binder that holds the ribbons together.
Another aspect of the current invention is a hybrid matrix fiber composite wherein the first matrix provides a composite having a compressive strength and stiffness through impregnated fibers aligned into a ribbon, and the second matrix placed between the ribbons provides the hybrid composite with fracture toughness. The first and second matrix materials are chemically or physically bonded together to form the composite.
Another aspect of the current invention is a method for manufacturing hybrid matrix fiber composites wherein a plurality of fibers are impregnated in a first matrix material and cured to partially or fully solidify the first matrix material around the aligned fibers to form a ribbon. A plurality of ribbons are parallelly positionally aligned and coated with a second matrix material, and the second matrix material is cured or otherwise solidified to form chemical or physical bonds between the two matrices.
Another aspect of the current invention is a process for manufacturing a hybrid matrix fiber composite comprising steps:
(a) producing a component comprising a plurality of fibers by:
(i) impregnating the fibers in the first matrix materials;
(ii) aligning said fibers by tensioning; and
(iii) curing, partially curing, or otherwise solidifying the first matrix material around the aligned fibers to form a ribbon;
(b) aligning a plurality of ribbons evenly within a second matrix material; and
(c) curing or otherwise solidifying the first and second matrix materials to form chemical or physical bonds between the two matrixes.
Still another aspect of the current invention is a hybrid matrix fiber composite having a compression strength of at least about 2×10
5
psi, a stiffness of at least about 6×10
6
psi and a toughness (G
IC
) of at least about 500 J/m
2
.
REFERENCES:
patent: 4532169 (1985-07-01), Carley
patent: 4764397 (1988-08-01), Fischer et al.
patent: 4925729 (1990-05-01), O'Connor
patent: 4936186 (1990-06-01), Sekido et al.
patent: 4992318 (1991-02-01), Gadkaree
patent: 5085928 (1992-02-01), Krueger
Deteresa Steven J.
Groves Scott E.
Lyon Richard E.
Dixon Merrick
Tak James S.
The Regents of the University of California
Thompson Alan H.
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