Self-repairing, reinforced matrix materials

Abstract

Self-repairing, fiber reinforced matrix materials include a matrix material including inorganic as well as organic matrices. Disposed within the matrix are hollow fibers having a selectively releasable modifying agent contained therein. The hollow fibers may be inorganic or organic and of any desired length, wall thickness or cross-sectional configuration. The modifying agent is selected from materials capable of beneficially modifying the matrix fiber composite after curing. The modifying agents are selectively released into the surrounding matrix in use in response to a predetermined stimulus be it internal or externally applied. The hollow fibers may be closed off or even coated to provide a way to keep the modifying agent in the fibers until the appropriate time for selective release occurs. Self-repair, smart fiber matrix composite materials capable of repairing microcracks, releasing corrosion inhibitors or permeability modifiers are described as preferred embodiments in concrete and polymer based shaped articles.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This is a continuation of application Ser. No. 10 / 376,906, filed Feb. 28, 2003, U.S. Pat. No. 7,022,179, which is a continuation of application Ser. No. 09 / 447,894, filed Nov. 23, 1999, U.S. Pat. No. 6,261,360, which is in turn a continuation of Ser. No. 08 / 918,630, filed Aug. 22, 1997, now U.S. Pat. No. 5,989,334, which is in turn a continuation of application Ser. No. 08,537,228, filed Sep. 29, 1995, now U.S. Pat. No. 5,660,624, which is in turn a continuation of application Ser. No. 08 / 189,665, filed Feb. 1, 1994, abandoned, which is in turn a continuation-in-part of U.S. Ser. No. 08 / 174,751, filed Dec. 29, 1993, now U.S. Pat. No. 5,575,841, which is in turn a continuation of U.S. Ser. No. 07 / 540,191, filed Jun. 19, 1990 abandoned.BACKGROUND OF THE INVENTION [0002] The present invention generally relates to matrix materials for use in a wide variety of end use fields and applications. More particularly, the invention relates to new a...

AI Technical Summary

Benefits of technology

[0018] In accordance with these and other objects, the present invention provides new and improved shaped articles comprising:

[0019] a cured matrix material having a plurality of hollow fibers dispersed therein, the hollow fibers having a selectively releasable modifying agent contained therein, means for maintaining the modifying agent within the fibers until selectively released and means for permitting selective release of the modifying agent from the hollow fibers into the matrix material in response to at least one predetermined external stimulus. In accordance with this invention the shaped articles are matrix composite materials of varying size and end use applications. The cured matrix materials have within them smart fibers capable of delivering repair chemicals into the matrix wherever and whenever they are needed.

[0020] The present invention also provides a new and improved method for providing shaped articles having long-term durability and environmental degradation resistance comprising the steps of providing a curable matrix composition, distributing a plurality of hollow fibers therein in desired manner so that the hollow fibers are disposed within the matrix material in a desired predetermined distribution. The hollow fibers are filled with a selectively releasable modifying agent therein which is not released during the mixing or distributing step. The fibers are structured so that the modifying agents stay within the interior spaces or cavities of the fibers within the matrix until the matrix is cured or set. After curing, the modifying agents are selectively released from the fibers by application or action of at least one predetermined external stimulus.

[0021] In a preferred embodiment, the method of providing an improved durability shaped article comprises providing a cured matrix material containing smart self repair fibers reinforcement therein.

[0022] The principles of the present invention are applicable to space age polymer, metal and / or ceramic structural matrix composite materials as well as more conventional cementitious settable or curable building or construction materials.

Problems solved by technology

One major drawback of concrete is that it is relatively low in tensile strength.

Concrete also has little impact resistance and is frequently brittle.

A third major drawback is that its durability is significantly reduced when it is used in applications which require it to be exposed to repeated freeze-thaw cycles in the presence of water.

Freezing and thawing with the accompanying expansion and contraction of the water, forms cracks in the concrete.

The addition of fibers to concrete has improved its tensile strength but has decreased its compression strength.

Providing exterior coatings on the outer surfaces of the concrete has reduced water permeation, but it is a time-consuming additional step and has little, if any, effect on the lasting strength of the concrete.

These efforts have met with generally unsatisfactory results.

Moreover, the melted, permeated agents leave behind voids in the concrete which weakens the overall structure under load.

In connection with the polymer and / or metal or ceramic matrix composite materials, as well as, in the settable building materials such as concrete materials, special problems cause structures made from these materials to become aged or damaged in use.

More particularly, special structural defects arise in use including microcracking, fiber debonding, matrix delamination, fiber breakage, and fiber corrosion, to name but a few.

Any one of these microscopic and macroscopic phenomena may lead to failures which alter the strength, stiffness, dimensional stability and life span of the materials.

Microcracks, for example, may lead to major structural damage and environmental degradation.

The microcracks may grow into larger cracks with time and cause overall material fatigue so that the material deteriorates in long-term use.

Advanced matrix composites used in structural applications are susceptible to damage on both the macro- and microscopic levels.

Typical macroscopic damage to composite laminates involves delaminations and destruction of the material due to impact.

On the micrographic scale, damage usually involves matrix microcracking and / or debonding at the fiber / matrix interface.

Internal damage such as matrix microcracking alters the mechanical properties of shaped articles made therefrom such as strength, stiffness and dimensional stability depending on the material type and the laminate structure.

Thus, microcracks can ultimately lead to overall material degradation and reduced performance.

Moreover, prior studies have shown that microcracks cause both fiber and matrix dominated properties of the overall composite to be effected.

Repair of damages is a major problem when these matrix composite materials are employed in large-scale construction or advanced structures.

Microscale damage occurring within the matrix is likely to go undetected and the damage which results from this type of breakdown may be difficult to detect and very difficult to repair.

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