U.S. patent application number 11/932720 was filed with the patent office on 2008-03-06 for self-repairing, reinforced matrix materials.
Invention is credited to Carolyn M. Dry.
Application Number | 20080053338 11/932720 |
Document ID | / |
Family ID | 27558638 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080053338 |
Kind Code |
A1 |
Dry; Carolyn M. |
March 6, 2008 |
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.
Inventors: |
Dry; Carolyn M.; (Winona,
MN) |
Correspondence
Address: |
Mara E. DeBoe;MERCHANT & GOULD P.C.
P.O. Box 2903
Minneapolis
MN
55402-0903
US
|
Family ID: |
27558638 |
Appl. No.: |
11/932720 |
Filed: |
October 31, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11278631 |
Apr 4, 2006 |
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11932720 |
Oct 31, 2007 |
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10376906 |
Feb 28, 2003 |
7022179 |
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11278631 |
Apr 4, 2006 |
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09447894 |
Nov 23, 1999 |
6261360 |
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10376906 |
Feb 28, 2003 |
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08918630 |
Aug 22, 1997 |
5989334 |
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09447894 |
Nov 23, 1999 |
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08537228 |
Sep 29, 1995 |
5660624 |
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08918630 |
Aug 22, 1997 |
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08189665 |
Feb 1, 1994 |
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08537228 |
Sep 29, 1995 |
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08174751 |
Dec 29, 1993 |
5575841 |
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08189665 |
Feb 1, 1994 |
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07540191 |
Jun 19, 1990 |
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08174751 |
Dec 29, 1993 |
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Current U.S.
Class: |
106/642 ;
106/640; 106/643; 106/677 |
Current CPC
Class: |
A61L 27/48 20130101;
Y10T 428/249994 20150401; B29C 73/163 20130101; C04B 22/006
20130101; C04B 40/06 20130101; C04B 2235/524 20130101; C04B
2235/5284 20130101; C08K 7/02 20130101; B29C 73/22 20130101; C04B
40/0263 20130101; C22C 47/04 20130101; B32B 2307/762 20130101; C08K
7/00 20130101; B32B 5/02 20130101; C22C 47/00 20130101; C22C 49/14
20130101; Y10T 428/249995 20150401; B32B 15/14 20130101; B32B
2307/554 20130101; B32B 2250/40 20130101; C04B 40/0641 20130101;
Y10T 428/249997 20150401; C04B 40/0092 20130101; C04B 20/1025
20130101; C04B 2235/3217 20130101; C04B 2235/80 20130101; B28B
17/00 20130101; C04B 2111/72 20130101; C08J 3/241 20130101; B32B
17/10036 20130101; C22C 49/00 20130101; C04B 20/0056 20130101; C04B
40/0675 20130101; C04B 2103/0067 20130101; B32B 17/10963 20130101;
B32B 2603/00 20130101; C04B 35/80 20130101; B82Y 30/00 20130101;
B32B 17/04 20130101; Y10T 428/249971 20150401; B32B 15/20 20130101;
C04B 28/34 20130101; C04B 38/0003 20130101; B32B 2605/18 20130101;
B32B 15/18 20130101; B32B 2250/03 20130101; C04B 35/52 20130101;
C04B 40/0028 20130101; C04B 40/0633 20130101; B32B 2307/54
20130101; C04B 20/0048 20130101; C04B 20/1025 20130101; C04B
20/0056 20130101; C04B 40/0633 20130101; C04B 26/14 20130101; C04B
40/0633 20130101; C04B 22/085 20130101; C04B 24/08 20130101; C04B
24/282 20130101; C04B 24/32 20130101; C04B 24/42 20130101; C04B
28/02 20130101; C04B 40/0633 20130101; C04B 26/02 20130101; C04B
28/34 20130101; C04B 20/0056 20130101; C04B 2103/0046 20130101;
C04B 20/1025 20130101; C04B 2103/00 20130101 |
Class at
Publication: |
106/642 ;
106/640; 106/643; 106/677 |
International
Class: |
C04B 20/00 20060101
C04B020/00; C04B 16/00 20060101 C04B016/00; C04B 22/00 20060101
C04B022/00 |
Claims
1. An article comprising a cured matrix material having a modifying
agent therein, wherein the modifying agent is capable of
beneficially modifying the composite matrix material in response to
a stimulus.
2. The article of claim 1 in which the matrix is comprised of
cement, concrete, sintered fly ash or bottom ash/phosphoric acid
mixtures, ceramic, silicon oxide, titanium oxide, silicon nitride,
metals, aluminum, steel, metal alloys, carbon, graphite, asphalt,
thermoplastic polymers, thermosetting polymers, thermoplastic
elastomers, crosslinkable polymers, curable polymer resin systems,
hydroxyapatite, thermoplastic polymers, polyolefins, polyesters,
polycarbonates, polyacrylates, polyarylates, polyamides,
polyimides, polyaramides, polyurethanes, foaming polyurethanes,
curable resin systems, one and two part epoxies, phenolformaldehyde
resins, thermoplastic elastomers, rubbery polymers, styrene,
butadiene, rubber, neoprene, SEBS, NBR, and EPDM rubbers,
viscoelastic materials, latexes, sinterable ceramics,
hydroxyapatites, silicas, titanium, carbides, oxides, alumina,
iron, lead, copper, steel, bronze, phosphor bronze, brass, alloys,
bone, or calcium salts
3. The article of claim 1 wherein the modifying agent comprises at
least one of one- and two-part adhesives, one- and two-part epoxy
adhesives, cyanoacrylate adhesives, Elmer's glue, sealant,
siloxane, silica additives, calcium nitrate, polyprolylene glycol,
amines and other crosslinkers, epoxy precursors, polymerizable
monomers such as methyl methacrylates, styrene or other
polymerizable starting materials, acids, bases, and solvents.
4. The article of claim 1 wherein the modifying agent self repairs
the matrices by way of cement, fly ash, bottom ash, phosphoric
acid, ceramic, silicon oxide, titanium oxide, silicon nitride,
metals, aluminum, steel, metal alloys, carbon, graphite, asphalt,
thermoplastic polymers, thermosetting polymers, thermoplastic
elastomers, crosslinkable polymers, curable polymer resin systems,
hydroxyapatite, thermoplastic polymers, polyolefins, polyesters,
polycarbonates, polyacrylates, polyarylates, polyamides,
polyimides, polyaramides, polyurethanes, foaming polyurethanes,
thermosetting and crosslinkable polymers, curable resin systems,
one and two part epoxies, phenolformaldehyde resins, thermoplastic
elastomers, rubbery polymers, styrene, butadiene, rubber, neoprene,
SEBS, NBR, and EPDM rubbers, viscoelastic materials, latexes,
sinterable ceramics, hydroxyapatites, silicas, titanium, carbides,
oxides, alumina, iron, lead, copper, steel, bronze, phosphor
bronze, brass, bone, calcium salts
5. The article of claim 1 further comprising at least one release
vessel having the modifying agent therein.
6. The article of claim 5, wherein the release vessel is a hollow
particle.
7. The article of claim 1, wherein the article is for an aircraft,
automotive, aerospace, or marine application.
8. The article of claim 1, wherein the article resists cracking,
corrosion, and oxidation.
9. The article of claim 1, wherein the stimulus is at least one of
heating, cooling, loading, impacting, cracking, water infusion,
chloride infusion, alkalinity changes, acidity changes, acoustic
excitation, low frequency wave excitations, hydrostatic pressure,
rolling pressure, light sensitivity, laser excitation, electrical
currents, voltages, electrorheological excitation, radiation, or
other energetic stimuli.
10. The article of claim 1, wherein the matrix is steel and the
stimulus is heat caused by fire or impact caused by earthquake.
11. An article comprising a cured composite matrix material having
a modifying agent in release vessels therein, wherein the modifying
agent is capable of beneficially modifying the composite matrix
material in response to a stimulus, wherein the cured matrix is a
coating.
12. The article of claim 11 wherein the modifying agent comprises
at least one of one- and two-part adhesives, one- and two-part
epoxy adhesives, cyanoacrylate adhesives, Elmer's glue, sealant,
siloxane, silica additives, calcium nitrate, polyprolylene glycol,
amines, epoxy precursors, polymerizable monomers such as methyl
methacrylates, styrene, acids, bases, solvents, cement, fly ash,
bottom ash, phosphoric acid, ceramic, silicon oxide, titanium
oxide, silicon nitride, metals, aluminum, steel, metal alloys,
carbon, graphite, asphalt, thermoplastic polymers, thermosetting
polymers, thermoplastic elastomers, crosslinkable polymers, curable
polymer resin systems, hydroxyapatite, thermoplastic polymers,
polyolefins, polyesters, polycarbonates, polyacrylates,
polyarylates, polyamides, polyimides, polyaramides, polyurethanes,
foaming polyurethanes, crosslinkable polymers, curable resin
systems, one and two part epoxies, phenolformaldehyde resins,
thermoplastic elastomers, rubbery polymers, butadiene, rubber,
neoprene, SEBS, NBR, and EPDM rubbers, viscoelastic materials,
latexes, sinterable ceramics, hydroxyapatites, silicas, titanium,
carbides, oxides, alumina, iron, lead, copper, steel, bronze,
phosphor bronze, brass, alloys, bone, and calcium salts.
13. The article of claim 1, wherein the modifying agent in the
hollow particle is a polyolefin.
14. The article of claim 13, wherein the matrix is a laminate
structure.
15. The article of claim 14 wherein the polyolefin reacts with a
chemical in the laminate structure.
16. The article of claim 11 further comprising at least one hollow
release vessel having the modifying agent therein and the vessels
are made of fiberglass fibers, cement fibers, asphalt fibers,
hydroxyapatite fibers, glass fibers, ceramic fibers, metal fibers,
polyolefin fibers, polyester fibers, polyamide fibers, polyaramide
fibers, polyimide fibers, carbon fibers, graphite fibers, cellulose
fibers, nitrocellulose fibers, hydrocarbon fibers, Goretex.TM.
fibers, Kevlar.TM. fibers, silicon nitride fibers, polysiloxane,
epoxy, hydrocarbon, polytetrafluoroethylene, polyurethane, aramid,
polypropylene, or elastomer
17. The article of claim 1, wherein the hollow release vessel is a
hollow particle.
18. The article of claim 11, wherein the coating is a paint,
membrane, or roofing material.
19. The article of claim 11, wherein the coating is for an
aircraft, automotive, aerospace, or marine application.
20. The article of claim 11, wherein the coating resists cracking,
corrosion, and oxidation.
21. The article of claim 11, wherein the coating is a heat
sensitive coating, a pH sensitive coating, or an ion sensitive
coating.
22. The article of claim 11, wherein the external stimulus is at
least one of heating, cooling, loading, impacting, cracking, water
infusion, chloride infusion, alkalinity changes, acidity changes,
acoustic excitation, low frequency wave excitations, hydrostatic
pressure, rolling pressure, light sensitivity, laser excitation,
electrical currents, voltages, electrorheological excitation,
radiation, or other energetic stimuli.
23. The article of claim 11, wherein the matrix metal is steel and
the external stimulus is heat caused by fire or impact caused by
earthquake.
24. A shaped article comprising a cured composite matrix material
having a modifying agent therein, wherein the modifying agent is
capable of beneficially modifying the composite matrix material in
response to a stimulus, wherein the cured matrix material comprises
metal.
25. The article of claim 24, wherein the metal comprises at least
one of aluminum, steel, iron, titanium, lead, copper, bronze,
phosphor bronze, brass and other alloys.
26. The article of claim 25 wherein the metal is foamed.
27. The article of claim 24, wherein the matrix further comprises
polymer.
28. The article of claim 27, wherein the polymer is a foamed
polymer.
29. The article of claim 27, wherein the metal and polymer form a
sandwich panel.
30. The article of claim 24, wherein the modifying agent comprises
charged ions.
31. The article of claim 30, wherein the charged ions are metallic
charged ions.
32. The article of claim 26 wherein the modifying agent comprises a
metal particle.
33. The article of claim 24, wherein the metal matrix is steel and
the stimulus is heat caused by fire or impact caused by
earthquake.
34. The article of claim 24, wherein the metal is aluminum and the
modifying agent comprises copper.
35. The article of claim 34 wherein the modifying agent comprises
copper and another metal.
36. The article of claim 24, wherein the modifying agent comprises
copper and the metal matrix comprises at least one of aluminum,
steel, iron, titanium, lead, bronze, phosphor bronze, brass and
other alloys.
37. The article of claim 24 further comprising at least one hollow
release vessel having the modifying agent therein.
38. The article of claim 37 in which the release vessel is a
particle.
39. The article of claim 37 wherein the matrix is carbon and
alumina and the release vessels are silicon nitride fibers.
40. The article of claim 39, wherein the article is a piston.
41. The article of claim 24, wherein the article is for an
aircraft, automotive, aerospace or marine application.
42. A shaped article comprising a cured composite matrix having a
modifying agent therein, wherein the modifying agent is capable of
beneficially modifying the cured composite material in response to
a stimulus, wherein the cured composite matrix comprises polymeric
material.
43. The article of claim 42, wherein the polymeric material
comprises at least one of a thermosetting or thermoplastic
material.
44. The article of claim 42 wherein the modifying agent comprises
at least one of polyolefin, polyester, polyamide, polyaramid,
polyimide, carbon, graphite, cellulose, nitrocellulose,
hydrocarbon, polytetrafluoroethylene, aramid, polypropylene, and
elastomer, one- and two-part adhesives, one- and two-part epoxy
adhesives, cyanoacrylate adhesives, Elmer's glue, acids, bases,
solvents, polysiloxanes, and amines.
45. The article of claim 42 further comprising at least one hollow
release vessel having the modifying agent therein and selected from
fiberglass fibers, cement fibers, asphalt fibers, hydroxyapatite
fibers, glass fibers, ceramic fibers, metal fibers, and the like,
polyolefin fibers, polyester fibers, polyamide fibers, polyaramide
fibers, polyimide fibers, carbon fibers, graphite fibers, cellulose
fibers, nitrocellulose fibers, hydrocarbon fibers, Goretex.TM.
fibers, Kevlar.TM. fibers, piezoelectric and shape memory
alloys.
46. The article of claim 42, wherein the hollow release vessel is a
hollow particle having modifying agent therein.
47. The article of claim 46, wherein the modifying agent in the
hollow particle is a polyolefin.
49. The article of claim 47 wherein the polyolefin reacts with a
chemical in the matrix.
50. The article of claim 42, wherein the modifying agent comprises
at least one of aluminum, steel, iron, titanium, lead, copper,
bronze, phosphor bronze, brass and other alloys.
51. The article of claim 42 wherein the matrix is cured by means of
catalysts, crosslinkers, radiation, heat, moisture, cooling,
setting up, hardening, rigidifying, curing, or setting to form the
shaped article.
52. The article of claim 42 in which the modifying agent is a
polymerizable monomer.
53. The article of claim 52 wherein the monomer is methyl
methacrylate, styrene, epoxy, siloxane, or amine.
54. A shaped article comprising a cured composite matrix having a
modifying agent therein, wherein the modifying agent is capable of
beneficially modifying the cured composite material in response to
a stimulus, wherein the cured composite matrix comprises a laminate
structure.
55. The article of claim 54 wherein the modifying agent is a layer
of the laminate.
56. The article of claim 55 wherein the modifying layer of the
laminate performs repair of the article.
57. A shaped article comprising a cured composite matrix having a
two-part epoxy modifying agent therein, wherein the modifying agent
is capable of beneficially modifying the cured composite material
in response to a stimulus, wherein the cured composite matrix
comprises polymeric material.
58. The article of claim 54 further comprising an epoxy precursor
material and an amine cross-linking agent.
59. A shaped article comprising a cured composite matrix having a
plurality of hollow vessels and modifying agent therein, wherein
the modifying agent is capable of beneficially modifying the cured
composite material in response to a stimulus selected from the
group of electrical, magnetic, and chemical means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of application of Ser. No.
11/278,631, filed Apr. 4, 2006 which 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 and improved
self-repairing, settable or curable matrix material systems
containing so-called smart-release fiber reinforcements, alone or
in combination with other reinforcement. My prior parent
application, Ser. No. 540,191, filed Jun. 19, 1990, describes the
new and improved inorganic and organic matrix composites employing
concrete matrix systems and asphalt matrix systems as illustrative
embodiments. That prior application describes smart-release hollow
fiber additives in settable construction materials and
thermoplastic matrices, such as asphalt. This application is being
filed to describe other embodiments of the smart-release matrix
composite materials generally described in my earlier application
and to provide additional examples of end use applications to which
these new and improved compositions, articles and methods may be
specially adapted and used.
[0003] Cement is a fine, gray powder consisting of alumina, lime,
silica and iron oxide which sets to a hard material after mixture
with water. Cement, along with sand and stone aggregate, make up
concrete, the most widely used building material in the world.
Steel reinforcing bars (rebars) are commonly added to the interior
of concrete for additional strength.
[0004] There are many reasons for the popularity of concrete. It is
relatively inexpensive, capable of taking on the shape of a mold,
has exceptionally high compression strength and is very durable
when not exposed to repeated freeze-thaw cycles. However, as a
building or construction material, concrete, whether it is
reinforced or not, is not without some shortcomings. One major
drawback of concrete is that it is relatively low in tensile
strength. In other words, it has little ability to bend. 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.
Concrete is relatively porous and water is able to permeate the
material. Freezing and thawing with the accompanying expansion and
contraction of the water, forms cracks in the concrete.
Furthermore, if salt is also present in the environment, it
dissolves in the water and permeates into the concrete where it is
capable of inducing corrosion in any of the rebars or other
metallic reinforcements present.
[0005] Various techniques have been suggested in the past for
overcoming these drawbacks. 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. The addition of modifying agents as
freely-mixed additives into a concrete mixture before setting has
also been tried. These efforts have met with generally
unsatisfactory results. Attempts to add modifying agents in the
form of micronodules or prills have also been tried. Frequently,
the prills are designed to be heat melted to cause release of the
modifying agent into the matrix after setting of the materials.
These designs require the application of heat to release the
beneficial additive into the matrix after cure. Moreover, the
melted, permeated agents leave behind voids in the concrete which
weakens the overall structure under load. Accordingly, a demand
still exists for an improved concrete matrix material having
greater tensile strength, greater durability and comparable or
improved compression strength.
[0006] In addition to cementitious building materials, the use of
polymer composites as structural materials has grown tremendously
in recent years. Polymer composite materials have advantages over
steel or concrete including good durability, vibration damping,
energy absorption, electromagnetic transparency, toughness, control
of stiffness, high stiffness to weight ratios, lower overall weight
and lower transportation cost. These polymer matrix materials
comprise a continuous polymer phase with a fiber reinforcement
therein. Some polymer composite materials are three times stronger
than steel and five times lighter. They have heretofore been
generally more expensive but their use may, in the long term, be
economical because of their greatly reduced life cycle costs.
Europeans have made bridges completely of specialty polymer matrix
composite materials. The polymer composite materials may be used as
rebars, tensioning cables, in bonded sheets, wraps, decks,
supports, beams or as the primary structures for bridges, decks or
buildings. Structures made from polymer matrix materials are
especially effective in aggressive environments or are well adapted
for building structures where electromagnetic transparency may be
needed for highways, radar installations and hospitals.
[0007] As used herein, matrix composite materials may refer to
generally any continuous matrix phase whether it comprises a
settable construction material such as cementitious materials or a
thermoplastic material such as asphalt materials, as well as, other
synthetic or natural high polymer materials, ceramics, metals and
other alloy materials. The matrix composite materials include
various fiber reinforcements therein distributed throughout the
matrix or placed at desired locations within the continuous phase.
The matrix composite materials may be fabricated as large building
structures and load bearing shaped articles, or they may be molded
or machined as small parts for specialty uses. For example, the
matrix material may comprise a thin sheet or web of material in the
form of a foil, wrap, tape, patch or in strip form. As presently
used in this specification, the term matrix composite material does
not necessarily refer to large civil engineering structures such as
highways and bridges.
[0008] 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.
[0009] 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. Thermal, electrical and acoustical properties
such as conductance, resistance and attenuation have also been
shown to change as matrix cracks initiate. Microcracks act as sites
for environmental degradation as well as for nucleation of
microcracks. Thus, microcracks can ultimately lead to overall
material degradation and reduced performance.
[0010] Moreover, prior studies have shown that microcracks cause
both fiber and matrix dominated properties of the overall composite
to be effected. Fiber dominated properties such as tensile strength
and fatigue life may be reduced due to redistribution of loads
caused by matrix damages. Matrix dominated properties on the other
hand such as compressive residual strength may also be influenced
by the amount of matrix damage. The impact responses of toughened
polymer matrix composites have been studied and it has been shown
that matrix cracking precedes delamination which, in turn, precedes
fiber fracture. Tough matrices which can reduce or prevent matrix
cracking tend to delay the onset of delamination which results in
an improved strength composite and longer lasting composite
material.
[0011] Repair of damages is a major problem when these matrix
composite materials are employed in large-scale construction or
advanced structures. Macroscale damage due to delamination,
microcracking or impacts may be visually detected and can be
repaired in the field by hand. 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.
[0012] In order to overcome the shortcomings of the prior art
construction and polymer, ceramic or metal matrix composite
materials, it is an object of the present invention to provide new
and improved smart structural composite materials having a
self-healing capability whenever and wherever cracks are
generated.
[0013] It is another object of the present invention to provide new
and improved composite materials including self-repairing
reinforcing fibers capable of releasing chemical agents into the
local microscopic domains of the matrix to repair matrix
microcracks and rebond damaged interfaces between fibers and
matrices.
[0014] It is a further object of the present invention to provide a
new and improved structural material.
[0015] It is another object of the present invention to provide a
new and improved cementitious material.
[0016] It is still a further object of the present invention to
provide a new and improved cementitious or other construction
composite material having greater durability and greater tensile
strength.
[0017] It is still another object of the present invention to
provide a new and improved matrix composite materials containing
smart self-repairing fiber reinforcement containing repair
chemicals therein which may be released by the smart fibers as
needed in response to an external stimulus, and optionally which
may be refilled with additional repair chemicals as needed in the
field.
SUMMARY OF THE INVENTION
[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.
[0023] Other objects and advantages will become apparent from the
following Detailed Description of the Preferred Embodiments, taken
in conjunction with the Drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIGS. 1a-1f are schematic views of the new and improved
self-repairing fiber reinforced matrix composite material in
accordance with the present invention, illustrating a smart matrix
repair sequence of load-induced cracking, modifying chemical
release and subsequent rebonding and repair of the fiber and
matrix;
[0025] FIGS. 2a-2e are schematic views of the new and improved
self-repairing fiber reinforced matrix composite material in
accordance with this invention, illustrating a smart matrix repair
sequence of salt or pH change penetration into the matrix adjacent
a smart fiber wrapped rebar reinforcement causing dissolution of
the pH sensitive coating, thereby releasing anticorrosion modifying
agents in the domain or vicinity of the rebar to prevent corrosion
of the rebar;
[0026] FIGS. 3a-3c are schematic views of the new and improved
self-repairing fiber reinforced matrix composite material in
accordance with this invention, illustrating a smart matrix repair
sequence of freeze/thaw protection including freeze induced release
of antifreeze from the fibers to provide an antifreeze-containing
matrix to reduce freeze/thaw damage;
[0027] FIG. 4 is a schematic view of the new and improved smart
fiber reinforced matrix composite material in accordance with the
present invention, illustrating a release, repair mechanism in
which the fiber is debonded from the coating and matrix in response
to an applied load to release the modifying agent from the uncoated
fiber pores;
[0028] FIG. 5 is a schematic view of a smart fiber reinforced
matrix composite material in accordance with this invention,
illustrating a release, repair mechanism in which an applied load
causes dimensional changes in the fiber promoting release of
modifier from the fiber into the matrix;
[0029] FIGS. 6a and 6b are schematic views of a new and improved
matrix composite material in accordance with this invention,
illustrating release and repair from twisted fiber bundles, whereby
compressive loading causes unlocking of the twisted fiber bundles
to release modifying agent into the adjacent matrix;
[0030] FIG. 7 is a schematic view of a new and improved
self-repairing fiber reinforced matrix composite material and
system in accordance with the preferred embodiment of this
invention, whereby a smart fiber disposed within the matrix may be
refilled with replacement modifier as needed by drawing modifier
into the fibers using a vacuum pump;
[0031] FIG. 8 is a schematic view of a fiber reinforced matrix
composite material in accordance with another preferred embodiment
of the invention, illustrating a matrix containing a network of
interconnected smart fibers into which additional modifying
chemicals may be added from the exterior of the matrix in use;
[0032] FIG. 9 is a schematic view of the new and improved matrix
composite material in accordance with this invention, illustrating
a light activated release mechanism employing lasers;
[0033] FIG. 10 is a schematic view of the new and improved
self-repairing matrix composite material in accordance with this
invention, illustrating a hydrostatic pressure induced release and
repair mechanism;
[0034] FIG. 11 is a schematic view of a smart fiber reinforced
matrix composite material wherein the modifying agents are released
from the fibers by acoustic excitation;
[0035] FIG. 12 is a schematic view of a smart fiber reinforced
matrix composite material of this invention, illustrating seismic
or low frequency wave-induced modifying agent release
mechanism;
[0036] FIGS. 13a and 13e are schematic views comparing the
corrosion of rebars possible with conventional cement
rebar-reinforced matrices of the prior art shown in FIG. 13a with
the corrosion prevention provided by the new and improved smart
fiber matrices of this invention shown in FIG. 13e;
[0037] FIGS. 13b and 13f are schematic views illustrating a
comparison of the permeability of prior matrices shown in FIG. 13b
with the impermeability produced by the smart matrix permeability
modification agent release mechanisms in accordance with this
invention shown in FIG. 13f;
[0038] FIG. 13c schematically illustrates the internal cracking
problems associated with prior art freeze/thaw damage to prior art
matrices shown in FIG. 13c in comparison with the antifreeze
containing smart matrix composite in accordance with this invention
shown in FIG. 13g;
[0039] FIGS. 13d and 13h illustrate the load-induced cracking
schematically illustrated for a prior art matrix shown in FIG. 13d
in comparison with the internally released crack prevention and
filling smart fiber matrices in accordance with the present
invention shown in FIG. 13h;
[0040] FIG. 14 is a schematic view of a new and improved smart
fiber having a notched wall configuration;
[0041] FIG. 15 is a schematic view of a new and improved smart
fiber having a bulging spheroidal portion and along its
cross-sectional configuration;
[0042] FIG. 16 is a schematic view of a V-shaped smart hollow fiber
in accordance with this invention;
[0043] FIG. 17 is a schematic view of a double lumen smart fiber
tubing in accordance with this invention;
[0044] FIG. 18 is a U-shaped smart fiber tubing in accordance with
this invention;
[0045] FIG. 19 is a schematic view of an alternate smart fiber
configuration including an A-shaped tapering enlarged area along
the length thereof;
[0046] FIG. 20 illustrates a coaxial concentric assembly of a
polypropylene inner hollow fiber surrounded by an outer brittle
glass fiber in accordance with a preferred embodiment;
[0047] FIG. 21 is a schematic view of a new and improved
anticorrosion composite matrix in accordance with this invention,
illustrating the use of redundant protective features to provide an
enhanced anticorrosion reinforced concrete member;
[0048] FIGS. 22a-22d are schematic views illustrating the use of
specialty piezoelectric smart repair fibers to provide selective
release and repair of ionically charged ion modifying agents in
response to compressive loading;
[0049] FIG. 23a is a schematic view of an alternate embodiment of a
self-repairing fiber reinforced matrix composite material in
accordance with this invention, illustrating the use of a smart
matrix repair fiber wrapped rebar in combination with an
impermeable barrier layer equipped with sensors to detect changes
in moisture, voltage or chloride iron concentration within the
matrix;
[0050] FIG. 23b is a schematic view of a preferred embodiment
similar to FIG. 23a wherein the impermeable barrier is employed as
an electric charge applicator to permit an applied electrical
signal to cause a release of anticorrosion chemicals within the
matrix adjacent a rebar;
[0051] FIG. 23c is a schematic view of the alternate embodiment
similar to FIGS. 23a and 23b wherein a separate water barrier layer
is employed as a first line of defense in combination with the
hollow smart fibers in accordance with this invention, which in
turn contains water binding hydroscopic chemical agent such as
Zypex.TM., or the like;
[0052] FIG. 23d illustrates a special embodiment employing a
separate electrode barrier adjacent a rebar wrapped with the smart
fibers which act to create a galvanic cell to release a water
scavenging hydroscopic chemical when moisture intrusion is
detected;
[0053] FIG. 23e is an alternate embodiment of the type shown in
FIG. 23d wherein the electrode adjacent to the rebar is capable of
causing smart fiber release of charged zinc ions to coat the rebar
in an electroplating operation to prevent corrosion of the rebar
once the ingress of water or moisture is detected;
[0054] FIGS. 24a and 24b schematically illustrate an alternate
embodiment of the present invention wherein the smart fibers
comprise a twisted pair of fibers embedded in the matrix as shown
in FIG. 24a and wherein changes in load on the matrix cause
chemicals to be released from the twisted pair of fibers as shown
in FIG. 24b and illustrating that the twisted pair of fibers may
comprise optical fibers;
[0055] FIGS. 25a and 25b illustrate a schematic view of an
alternate embodiment of a new and improved matrix in accordance
with this invention, including an outer glass tube smart fiber
having an optical fiber therein as well as a modifying adhesive
chemical as shown in FIG. 25b and illustrating the release of
adhesive due to cracking or maintaining the optical fiber in an
intact condition as shown in FIG. 25b;
[0056] FIGS. 26a and 26b illustrate another preferred alternate
embodiment of the invention, schematically illustrating an optical
fiber which itself is used as the smart fiber containing repair
chemical therein and having an optical fiber cladding layer along
the periphery thereof as shown in FIG. 26a and showing in FIG. 26b
schematically the change in light transmission properties caused by
breakage of the outer glass fiber and leakage of the repair
chemical to indicate that a fracture and release and repair have
occurred;
[0057] FIGS. 27a and 27b show another alternate embodiment of this
invention wherein the smart repair fiber comprises an assembly of
an outer glass tube and an inner metal fiber member in an optical
fiber and an adhesive modifying chemical therein as shown in FIG.
27a, which in response to an applied cracking load ruptures the
glass fiber to repair the crack while maintaining the optical fiber
in an altered, but undamaged condition as shown in FIG. 27b;
[0058] FIGS. 28a-28c illustrate schematically optical fiber/smart
fiber reinforcements for concrete matrices and demonstrate that the
release, repair mechanisms may change the refracturing index
transmission properties of the fluid so that the repair fiber
itself may indicate the fact of rupturing repair and may also
indicate the volume of the cracks filled;
[0059] FIGS. 29a and 29b illustrate an alternate aspect of this
preferred embodiment wherein septums or Bragg optical gratings may
be positioned at desired locations along the length of the smart
repair optical fiber as shown in FIG. 29a, which may aid in
indicating the location of cracks along the length of the fiber
within the matrix as shown in FIG. 29b;
[0060] FIGS. 30a-30d illustrate a schematic view of an alternate
embodiment wherein a smart fiber reinforcement comprises an optical
fiber filled with a repair chemical employing mirrors as shown in
FIG. 30a to assist in locating where a crack damage has occurred as
shown in FIG. 30b and showing repair and rebonding of the repair
chemical into the vicinity of the crack in FIG. 30c and further
showing in FIG. 30d the optional replenishment of the repair
chemical from an outside source using a vacuum pump.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0061] In accordance with the present invention, new and improved
shaped articles comprise curable, settable, cross-linkable and/or
hardenable matrix materials. The matrix material comprises a
continuous phase and is a material that may be shaped to form a
three-dimensional shaped article adapted for a particular use.
Matrix materials can include any curable, settable or hardenable
materials used in construction, building, roofing, roadway,
aircraft, automotive, marine, appliances, transportation and/or
biomedical fields for making shaped articles. Typically these
materials will be moldable or castable to form shaped objects or
may be laminated or assembled into finished products. The matrix
materials may be inorganic or organic in nature and may include by
way of illustration: cement, concrete, sintered fly ash or bottom
ash/phosphoric acid mixtures, ceramic including, for example,
silicon oxide, titanium oxide, silicon nitride, and metals such as
aluminum, steel or other metal alloys, carbon, graphite, asphalt,
thermoplastic polymers, thermosetting polymers, thermoplastic
elastomers, crosslinkable polymers, curable polymer resin systems
and hydroxyapatite. Illustrative thermoplastic polymers include
polyolefins, polyesters, polycarbonates, polyacrylates,
polyarylates, polyamides, polyimides, polyaramides, polyurethanes,
foaming polyurethane compositions and any other thermoplastic
polymers used as engineering thermoplastics for making shaped
articles. Thermosetting and crosslinkable polymers and curable
resin systems may include, for example, one and two part epoxies,
phenolformaldehyde resins and other thermosetting and crosslinkable
polymers. Thermoplastic elastomers can include rubbery polymers and
copolymers including, for example without limitation,
styrenebutadiene, rubber, neoprene, SEBS, NBR, and EPDM rubbers and
the like. Viscoelastic materials and various latex materials may
also be used. The matrix materials may also comprise sinterable
ceramic materials including hydroxyapatites, as well as, other
ceramic materials such as silicas, titanium, carbides, oxides and
alumina. The matrix materials may also comprise metal matrices
including aluminum, iron, lead, copper, steel, bronze, phosphor
bronze, brass and other alloys, as well as biomimetic systems like
bone matrices formed of various calcium salts, as well as other
organic and inorganic materials.
[0062] The matrix materials in accordance with this invention are
processable to form shaped articles by molding, casting, sintering,
laminating, machining, extruding, or other material fabrication
method useful with the matrix material selected. The size and
configuration of the finished shaped article produced is
essentially unlimited including various small machined parts to
very large engineering construction panels for use in building
roadway and transportation applications. The matrix materials may
be cured by means of catalysts, crosslinkers, radiation, heat,
moisture, cooling or by any means used in this art for setting up,
hardening, rigidifying, curing, setting or shaping these matrix
materials to form shaped articles or objects.
[0063] The new and improved shaped articles of this invention
additionally comprise hollow fibers having interior spaces therein
for containing selectively releasable modifying agents. The hollow
fiber materials may include inorganic fibers or organic fibers.
Illustrative inorganic fibers include, without limitation:
fiberglass fibers, cement fibers, asphalt fibers, hydroxyapatite
fibers, glass fibers, ceramic fibers, metal fibers, and the like.
Illustrative organic fibers that may be used as the hollow fiber
component may include, without limitation: polyolefin fibers,
polyester fibers, polyamide fibers, polyaramide fibers, polyimide
fibers, carbon fibers, graphite fibers, cellulose fibers,
nitrocellulose fibers, hydrocarbon fibers Goretex.TM. fibers,
Kevlar.TM. fibers, and the like, to name but a few.
[0064] The fibers may be bundled, woven or loose. They may be held
or engaged together with flexible web materials. They may comprise
twisted pairs and additionally may include concentric structures of
one or more fibers. The sidewalls of the fibers are typically
rupturable or porous to permit the discharge or exiting of the
modifying agent into the surrounding cured composite matrix
material. The fibers may come in different shapes, volumes, and
wall thicknesses. They may be generally notched, have periodic
enlargements or bulges, V-shaped, double or multiple lumens,
U-shaped, or they may comprise combinations of one or more
different types of fibers. For example, double walled fibers are
particularly useful for two-part modifying compositions such as
epoxies. Doubled fibers including a metallic inside fiber and a
glass outer sheath fiber are useful where bending of the metal
fiber assists in breaking the glass carrier fiber. Additionally,
assembled structures of polypropylene hollow porous fibers disposed
inside a glass outer fiber might be used to permit a first break
and release of modifying material to occur with the glass fiber and
thereafter a secondary break and release of the polypropylene fiber
at a later date to provide a specially long-term profile
modification to the shaped matrix composites. The smart-release
fibers may also be paired or include other specialty fibers such as
piezoelectric fibers or optical sensor fibers for providing special
monitoring, metering and diagnostic capabilities. Some of these
specialty composites will be more particularly described
hereinafter. The fibers may also be woven together into a web so
that they may be wrapped as an organized bundle around rebars or
the like. Although fiber materials are preferred, other
container-like smart release structures or vessels may be provided
for special end uses. For example, in relatively large structural
parts it may be useful to add the repair chemicals in large flat
balloons or bags layered or laid up within the matrix or layers of
matrix. It should be apparent to those skilled in this art that for
certain end uses, small release vessels having a shape somewhat
different from hollow fibers for performing the same smart release
functions may be employed. In addition, the fibers may be
relatively small, chopped or comminuted fibers having lengths of
less than about one inch and diameters of less than about 100
microns. The fibers and matrices may be readily used in usual
shaping processes such as in an injection molding operations or the
like.
[0065] In accordance with this invention, the hollow fibers include
certain internal modifying agents which are--selectively releasable
from the fibers in response to the application of certain
predetermined external stimuli. The modifying agents include agents
which will modify the performance characteristics of the cured
shaped article matrix materials in use. By way of illustration, the
modifying agent may include polymerizable monomers such as methyl
methacrylates, styrene or other polymerizable starting materials.
They may additionally include two part epoxies wherein an epoxy
precursor material is disposed in one fiber or in one lumen of a
double lumen fiber and the amine or other cross-linking agent is
disposed in an adjacent fiber or in the other lumen of the double
lumen fiber. Other curable polymerizable monomers may also be
employed.
[0066] Another modifying agent which may be used herein includes a
sealant used to prevent water permeability and ingress or egress of
water or other liquid materials to and from the cured matrix
composite. Illustrative examples for cement may include oily
sealants to preventingress of water such as linseed oil or other
known sealant materials.
[0067] Another important modifying agent for both cementitious and
polymer matrices include adhesives which cure in situ to repair
microcracks within the matrix in use. Illustrative adhesives
include one- and two-part adhesives, one- and two-part epoxy
adhesives, cyanoacrylate adhesives, Elmer's glue and others known
to those skilled in the art. The adhesives may bond matrix to
matrix, fiber to fiber, as well as fiber to matrix.
[0068] Certain water barriers are particularly useful modifying
agents for cementitious matrices. These may include special
Zypex.TM. brand sodium silicate additives as well as siloxane and
silica additives known as Salt Guard.TM. and the like.
[0069] Another modifying agent useful in the shaped articles of
this invention includes anticorrosion agents such as calcium
nitrite. These are particularly useful in cementitious matrices
employing rebar reinforcements or steel mesh reinforcements.
[0070] Another example of a modifying agent which may be disposed
in the interior of the hollow fibers for use herein includes
antifreeze material such as polypropylene glycol.
[0071] Fiber protectors may also be used as the modifying agents
which can be materials which protect the fibers themselves within
the matrix material. An example of this includes pH modifiers for
protecting fiberglass in highly alkaline environments.
[0072] Still another class of modifying agents particularly useful
in polymer matrices are solvents which permits solvent action to
actually repair microcracking damage locally at a cracking site or
possibly to dissolve the matrix or fibers or both to permit them to
re-form at a later time.
[0073] In addition to solvents, other curable monomers and
co-monomers may also serve this repair function. pH modification
agents may also be used as the modifying agents, either alkali or
acidic agents, which may be placed in the interior of the fibers
only to be released by an appropriate pH changes in the matrix.
Other additives may include flame retardant agents. Visco-elastic
polymers may also be used as modifiers.
[0074] In accordance with this invention, means are provided for
maintaining the modifying agent within the hollow fibers. The
modifying agents may be physically trapped by, for example, drawing
liquid additives into the interior of the fibers and retaining them
therein by capillary action or by closing off the ends of the
fibers. For brittle fibers, sealing of the ends by heat or pressure
may be one method for maintaining the modifying agents therein.
Moreover, specialty coatings may be used, which will selectively
degrade upon the occurrence of a particular external stimulus.
Illustrative examples might include heat sensitive coatings, pH
sensitive coatings, ion sensitive coatings, and the like. These
coatings are effective to close off the pores of the hollow fiber
walls or the ends of the fibers to prevent premature leakage of the
modifying agent until the intended time. Illustrative coatings may
include waxes, low molecular weight hydrocarbon oils and coating
polymers to name but a few.
[0075] In accordance with the present invention, means for
permitting selective release of the modifying agent in response to
the external stimulus may be provided. Illustrative examples
include the selectively removable or dissolvable coatings which
give way to permit leakage of the modifying agent in response to,
for example, stimuli such as heating, cooling, loading, impacting,
cracking, water infusion, chloride infusion, alkalinity changes,
acidity changes, acoustic excitation, low frequency wave
excitations, hydrostatic pressure, rolling pressure, light
sensitivity or laser excitation, or the like. Electrical currents,
voltages, electrorheological excitation, radiation, or other
energetic stimuli may also be employed or effective to permit or
cause selective release of the modifying agent or agents from the
fibers.
[0076] In accordance with this invention, the selective release of
the modifier occurs in the matrix when and where it is required and
may lead to improved toughness, strength, ductility, brittleness,
permeability, fire retardancy, stiffness, dimensional stability,
modulus of elasticity, fatigue, impact resistance, and other
improved properties. Specially important in accordance with this
invention is the ability to repair small microcracks forming in the
reinforced matrix composites. The selective release of the
modifying agent may be chosen to be effective to rebond the fibers
to the matrix, to repair the fibers themselves, to improve or
restore the matrix to fiber interface, to repair delaminations, and
to repair microcracks in the matrix itself which may repair or
overcome cracking or corrosion induced dimensional weaknesses and
ultimately reduced durability for the shaped articles.
[0077] As has been mentioned above, the shaped articles in
accordance with this invention may be used for a number of
applications, both large and small. Large construction applications
are particularly preferred, particularly those used in harsh
environments or for outdoor use. Illustrative end use applications
for the new and improved shaped articles in accordance with this
invention include, for example without limitation, structural
sandwich panels, exterior applied insulation panels, fire panels,
construction building blocks, cements, concretes, fireproof doors,
panels, walls, hazardous waste containment vessels, engines,
concrete building blocks, roadways, bridges, dams, engines, road
surfaces, roofing blocks, roofing shingles, decks for parking
garages, and other building structures and columns. Other
construction applications might include the use of these shaped,
cured, smart-release composites in bridges, post-tensioning cables,
road decks, road deck overlays, aircraft body components, including
fuselages, wings and tip design, machined parts, helicopter blades
as well as the aforementioned roofing structures.
[0078] The shaped articles of this invention might also be useful
in biomedical applications as bone replacements as prosthetic
devices and as biomedical adhesives. More particularly, shaped
articles of this invention may be used to form self-growing
structures. In accordance with this aspect of the invention, the
goal is to create a ceramic resembling bone which is an
organic-inorganic composite created at low temperature due to the
presence of organisms. Bone is made up of an oriented matrix which
is secreted by bone forming cells referred to as osteoblasts. In
natural bone, organic matrices are made up of structural molecules
which serve as a scaffolding and which are laid down in very
precise, oriented pattern of fibrils into and onto which inorganic
crystalline phases form. The formation of the first crystals of
inorganic salts of calcium phosphate are often referred to as
initiation or nucleation which occurs along nucleation sites which
appear at regular intervals along the organic scaffolding, usually
collagen laid down by osteoblasts. Once nucleation has occurred,
the next major process involves the continuation of crystalline
growth from these nucleation sites outward along the fabric of the
organic matrix and eventually between the molecules which serve as
scaffolding. As crystal growth continues and forms against
inorganic matrix, there is a loss of organic components which are
designed to reserve space in the matrix forever expanding the
inorganic phase.
[0079] In accordance with this biological models, the present
invention may be employed to provided a self-growing structure
something like bone, wherein the hollow pores polymer fibers may
release chemicals and act as an organic template on which to form a
strong structural bone-like composite. This self-growing structure
might be used for structural materials as well as for computer
chips or for prosthetic devices. More particularly, just as
ligaments or tendons have been used as natural matrices to form
bone materials, these polymer tubes or fibers are used in
accordance with the present invention to concentrate bone-like
substances. The fibers are hollow and have porous walls. In
accordance with this invention chemicals are released from the
hollow fibers, particularly polymeric materials which are designed
to cause targeted release of water in an inorganic matrix to form a
structural network of calcium phosphate materials. Instead of using
collagen gels to form a backbone network, in accordance with this
invention, a matrix material including inorganic cementitious salts
and a first polymer reactant may be provided which includes hollow
fiber materials including a condensable or cross-linkable moiety
reactive with polymer. Under appropriate conditions, release of the
co-reactant from the fibers causes a condensation reaction of the
matrix polymer in which water is produced. The water byproduct of
the condensation reaction is used to hydrate cement to build up a
structural backbone along the fiber regions.
[0080] In accordance with another aspect of the invention, a hollow
porous polymer fiber material may be placed in a calcium phosphate
material matrix in which a polymer powder monomer is present. A
cross-linking monomer is then released from the fibers into the
matrix. The ensuing condensation polymerization reaction releases
water, which then hydrates the calcium phosphate materials. Xypex
or other cement crystallizing initiator materials may carry the
hydration reaction away from the polymer fiber scaffolding within
the inorganic matrix. The structural make-up of these materials may
be designed to resist stresses by including piezoelectric fibers
within the matrix. Lines of force may be generated by prestressing
or stressing the piezoelectric polymer fibers along which charged
cementitious ions will migrate. This will cause the polymer matrix
to rearrange and the composite prestressing forces therefore will
generate an appropriate microstructure within the material.
[0081] Also in accordance with this aspect of the invention,
self-healing may be accomplished by leaving some of the original
fibers void or by adding additional fibers designed with specialty
repair chemicals for repairing the system. Hollow porous fibers may
be used to deliver repair chemicals at a later time if damage such
as cracking occurs. Repair chemicals, either present as an adjuvant
fiber additive or added to hollow fibers from the outside, may be
used to improve the visco-elasticity of the entire component as
desired.
[0082] In accordance with this invention, materials may be
developed for application in self-repairing materials for use in
facings, coatings and membranes. In accordance with this aspect of
the invention, the new and improved fiber-containing matrix
materials may be provided in the form of paints, membranes, roofing
materials, or the like, including self-repairing liquids within the
fibers. The materials may be provided in the form of wraps for
buildings, bridges, roads, or the like, including webs or fabrics
of smart fibers disposed within the matrix. Repair chemicals may
repair cracks in the wrap itself or also seep into and repair
adjacent structures to which the wrap is adhered to improve the
overall structural performance over time. Specialty wraps including
solar collecting fibers might also be added to the exterior of
previously existing outdoor structures.
[0083] Another biological or biomedical application for the new and
improved shaped articles of this invention might include
smart-release bandages, artificial skin materials, poultices,
bandaids and the like which include smart fibers which release
healing chemicals or healing promoting chemicals by upon movement
of the patient or by application of another stimulus, such as for
example, a heating pad, or the like. The smart fibers used in these
bandage applications might include such release chemicals as oxygen
releasing chemicals, moisturizers, aloe vera, antibiotics,
anti-inflammatants, analgesics, non-stick agents or the like.
[0084] Another illustrative use of the shaped articles of this
invention might be polymer matrices including smart fibers therein
which may be made to include dissolving chemicals which ultimately
assist in de-naturing, degrading or destroying the polymeric
structures by depolymerization or chemical reaction to improve
recyclability of the polymer material.
[0085] The shaped articles of this invention may also be used in
various small shaped article applications including aerospace
applications, pipe repair, engine pistons, rubber matrices,
water-borne paints and coatings, rubber gasket materials and other
seals and in woven fabrics. For example, in fabrics the fibers may
contain a fabric glue to repair small tears or abrasions of the
fabric. Hard self-repairing shaped articles, such as silicon
nitride fibers in carbon-alumina matrices for pistons might be
used. Metal matrices that may be employed include metals and alloys
such as alumina as well as foamed metals. The fibers for these
metallic composites may include adhesive materials or corrosion
resistant materials to help repair the matrices or other desirable
smart release additives.
[0086] The new and improved smart fibers of the present may be
disposed within large cross-sectional areas or sections of a matrix
prior to cure which may thereafter be used to release curing agents
from several positions disposed throughout the curable matrix
simultaneously to speed up or assist in the curing of large
cross-section polymer articles. Similarly, natural fibers such as
wheat straws or the like may be added to concrete or adobe matrices
to stabilize the composites so that they do not crumble or flow in
use.
[0087] In a related application, the new and improved smart matrix
materials may be used to perform road repair and pothole repair. In
connection with this aspect, smart release fiber-containing uncured
material may be added to a pothole. An agitation or pressure may be
used to release curative agents from the interior of fibers
provided in the matrix material to promote adhesion and curing of
the pothole repair mass to the substrate road surface. Additional
fibers may be provided, containing repair adhesives which release
in response to tire pressure, to further strengthen and reinforce
the pothole patch in use.
[0088] Another highway application of the present invention
includes the use of smart release fibers to add phosphorescent
chemicals to concrete or asphalt matrices. Phosphorescent roads may
clearly demarcate the road or highway surface from non-road driving
surfaces at night without the need for street lights or other
markers or reflectors. The smart matrix materials would permit
renewed release of phosphorescent agents into the road surface, as
the layers of the road surface are worn away by highway traffic. A
continually replenishing supply of chemicals that could absorb
sunlight during the day and re-emit it as phosphorescent light in
the evening hours would be provided.
[0089] In accordance with another aspect of this invention, the
shaped articles may include hollow and continuous matrix formed
into a shaped article and having hollow fibers therein which permit
visual inspection of the structural part in use. The use of hollow,
air-filled fibers permits persons to actually look into and see
inside the matrix to see cracks near the fibers. These hollow
fibers also permit exterior introduction of chemicals to be
performed to add chemicals to a previously cured matrix.
[0090] Hollow or filled fibers may be provided with dyes or other
sensing or sensible materials to identify the presence of
structural stresses or weaknesses and also the locations of these
stresses in large structural articles. For example, release of dyed
materials from fibers may permit the dye to migrate to the surface
to indicate a structural compromise or repair need in a highway,
bridge, or the like. Specialty dyes such as X-ray sensitive dyes
may be added to help diagnose a small micro-structural repair
problem. More particularly, if the dye is leaked into the matrix in
use due to structural damage, periodic diagnostic teams may test
with high energy beams shined into the matrix. The interactive dye
would signal back after excitation in a detectable manner so that
the need for attention or repair would be revealed. Piezoelectric
fibers may also be used to evaluate the state of the matrix. Remote
sensing of eddy currents or electrical or magnetic fields generated
about the fibers in response to pressures or stress may be detected
in a matrix in these ways.
[0091] Still another application for the shaped articles of this
invention can include non-biological but biomimetic materials
wherein a polymer matrix containing crystallizable mineral elements
such as alumina alkoxide may be provided. A condensation reactive
element or ingredient provided inside the smart fibers may be
released on application of appropriate external stimulus from the
smart fibers within the matrix containing the alumina crystals. The
by-product water of the condensation reaction in this case may be
used to cause alumina crystals to grow at specified locations
within the shaped article.
[0092] Another special useful application of the shaped articles in
accordance with this invention is as a containment structures for
radioactive or chemical waste materials. In accordance with this
aspect, fibers provided with chemically sensitive coatings or
radiation sensitive coatings may be provided which are adapted to
release scavenger compounds when radiation or chemical waste is
detected. The compounds will then migrate from the fibers into the
matrix to scavenge and render harmless radioactive or chemical
materials leaking into the containment vessels to prevent them from
being discharged from the containment area into the environment.
Alternatively, permeability modifying agents may be released from
the coated fibers to boost the impermeability of the containment
vessel to water-borne contaminants.
[0093] The new and improved shaped articles of this invention may
be employed to form self-repairing impact resistance layers in
laminated materials and structures. For example, a clear,
transparent polymer matrix containing adhesive filled glass fibers
may be used as an interlayer between two safety glass or polymer
sheets. Impact fracture of a base sheet will cause local release of
repair adhesive from the interlayer to control fragmentation and
rebond cracked or fractured sections of a laminate.
[0094] As has been mentioned above, various means may be provided
to force the repair chemicals out of the fibers. Chemicals may be
pumped into hollow fibers from the outside or propellant gases may
be injected into previously filled fibers to which external access
has been provided to force the chemicals out. Other methods to
promote repair chemical release may include electrical, magnetic,
and chemical means which alter the shape, permeability or coating
integrity of the fibers. Shape memory alloy materials may be used
as the fiber or these materials may be used in the fiber to squeeze
the fiber and thereby pump the chemicals out. Fibers which change
their shape in response to applied light or magnetic forces or
fields may also be used to discharge the chemicals as desired.
[0095] The smart release shaped articles and materials in
accordance with the present invention may be used throughout
building structures to provide earthquake proof buildings which can
withstand seismic activity with reduced hazard and damage. This is
accomplished by preventing flying debris from being created and by
supporting building structures in matrices adapted to
visco-elastically respond to seismic vibration.
[0096] Because the beneficial improvements provided by the new
composition, articles and methods of this invention may be useful
for broad range of applications, it is difficult to specifically
enumerate each of them. The present invention will be further
illustrated by several specific end use applications provided to
further illustrate the improvements provided by the present
invention.
[0097] Referring now to FIGS. 1a-1f, the new and improved
self-repairing fiber reinforced matrix composite and its operation
in the field is shown. As depicted in FIG. 1, a hollow fiber
containing an adhesive modifying agent and coated with a thin
coating material is dispersed within a settable or curable matrix
material which may be either a polymer or cementitious material. As
shown in FIG. 1b, a loading applied to a shaped article causes
strains within the matrix, which in turn cause the fiber to break
and the matrix to crack. This causes the modifying chemical agent
disposed within the hollow fiber to be released into the vicinity
of the crack in the matrix as shown in FIG. 1b. The modifying agent
flows and fills the void as shown in FIG. 1e and eventually cures
to rebond the fiber to the matrix and to repair the fiber to itself
as shown in FIG. 1f. This schematically illustrates the modified
fiber concept of the present invention.
[0098] Referring now to FIGS. 2a-2e, a similar smart fiber repair
embodiment is depicted wherein the smart hollow fibers contain
anticorrosive modifying agent and are coated with fibers which are
pH sensitive. These smart fibers are disposed within the matrix
adjacent the rebar reinforcement by selectively positioning them
adjacent the rebar as the matrix is poured into the concrete mold
or the rebar can actually be wrapped with the hollow fibers which
have been previously banded together as a web or tape. In
accordance with this matrix composite construction, the
anticorrosion filled smart fibers are disposed immediately adjacent
the rebars. The anticorrosive chemical compounds are not released
to protect the rebars unless or until the exchange has occurred in
the vicinity of the rebar, either due to chloride iron infiltration
or carbon dioxide intrusion. The advance of corrosive chemicals
breaks down the pH versus sensitive coating on the smart fiber,
releasing the protective anticorrosive agent to protect the rebar
from corrosion by the environmental chemicals found in FIGS.
2c-2e.
[0099] Referring now to FIGS. 3a-3c, the smart fiber matrix is
shown in operation in plain and in antifreeze modifying agent
disposed within the hollow fibers. A water-based antifreeze expands
as it cools to force its way out of the pores in the hollow fiber,
thereby dislodging the coating, if present, and permitting the
antifreeze to exit into the local environment of the matrix. As
shown in FIGS. 3b-3c, the release of the antifreeze into the matrix
lowers the freezing temperature of moisture in the materials within
the matrix preventing freeze/thaw damage from occurring to the
matrix.
[0100] Referring now to FIG. 4, a debonding of a coated fiber is
shown as a mechanism for releasing the modifying agent contained
within the smart fiber into adjacent areas of the matrix. This can
occur, for example, where there is coating applied to the smart
fiber to retain the modifying agent within the fiber interior as a
higher affinity for the surrounding matrix in a cured state than to
the fiber. Accordingly, debonding of the fiber from its coating
allows the pores to become open to permit chemical release.
[0101] Referring now to FIG. 5, there is illustrated in the
embodiment wherein modifying agent release is caused by torting,
twisting or other load changes which cause a dimensional change in
the shape of the hollow fiber, which in turn forces the modifying
agent out into the surrounding matrix. These torting, twisting or
other loads placed on the fiber may cause local debonding of the
fiber from its coating, permitting release as shown in FIG. 4 or a
mechanical forcing of the contents of the fiber through the pores,
which in turn causes dislodgment of the coating may also occur.
[0102] Referring now to FIGS. 6a and 6b, the application of the
compressive load on a twisted fiber bundle can cause debonding of
the coating from the twisted fibers forcing fluid contained within
the hollow spaces of the fiber through the fiber pores and into the
surrounding matrix.
[0103] Referring now to FIG. 7, a preferred embodiment of the
present invention includes providing the smart hollow fiber
reinforcement within a matrix so that end portions of the fiber are
accessible from the exterior of the matrix to permit additional
modifying agents to be supplied into the fibers of the matrix. As
depicted therein, a reservoir of modifying agent may be placed in
the fiber and a vacuum pump may be attached to the opposed ends to
draw the modifying agent into the fibers to replenish any leaked
materials therein.
[0104] FIG. 8 is an extension of the concept described and
schematically illustrated in FIG. 7 wherein a series of hollow
smart fiber reinforcements are arranged in a continuous network to
permit the additional chemicals to be added from the outside
throughout the entire matrix.
[0105] Referring now to FIG. 9, other mechanisms may be employed
for dislodging or releasing the modifying agent into the
surrounding matrix at a selected time after curing, such as, by
example, using laser energy to cause an aneurysm to form in the
fiber which permits leakage.
[0106] Referring to FIG. 10, hydrostatic pressures may also cause
the fiber diameter to be locally reduced, causing an exiting of the
modifying agent into the surrounding matrix.
[0107] FIG. 11 shows an embodiment wherein acoustic excitation is
employed as the means for releasing the modifying agent from the
fiber.
[0108] FIG. 12 is an alternate embodiment wherein waves of low
frequency such as seismic waves may pass through the matrix in such
a manner as to cause debonding of the fiber from a coating or
uncoated fibers may cause the modifying agent to exit from pores
disposed within the fiber matrix disposed within the hollow
fiber.
[0109] FIGS. 13a through 13h demonstrate in a side-by-side
comparison the ability of the smart fiber reinforced matrix
composite materials prepared in accordance with this invention to
prevent environmental distress and aging frequently encountered by
prior art composite materials. A comparison of FIGS. 13a and 13e
shows that the modifying agent in FIG. 13a is an entire corrosion
agent to prevent corrosion of the rebars and in that case calcium
nitrite is preferred.
[0110] In FIGS. 13b and 13f the permeability of the matrix may be
controlled by setting up a polymerized polymer within the matrix as
shown in FIG. 13f to prevent permeability. This may be effected in
several ways, and in one preferred embodiment, polymerizable
components are freely mixed within the concrete which require only
the exposure to a liquid catalyst to cause them to set up into an
impermeable barrier. FIGS. 13c and 13g illustrate the release of
antifreeze materials in FIG. 13g to prevent freeze/thaw and to
brittleness and cracking due to ice crystals formation within the
matrix from occurring. Finally, FIGS. 13d and 13h illustrate the
development of local microcracks due to local loading which may be
locally repaired by release of repairing adhesives as in FIG. 13h
to fill cracks or voids and rebond fibers and matrices adjacent
microcracks to prevent major microscopic failures from
occurring.
[0111] In accordance with this invention, the smart fiber hollow
fibers used to make the smart fiber reinforcements in accordance
with this invention may have any desired configuration. As
illustrated in FIGS. 14 through 20, a wide variety of
cross-sectional configurations may be employed, as well as
multi-lumen tubes and multiple concentric tube assemblies may be
employed.
[0112] Referring now to FIG. 21, the new and improved smart fiber
matrix composite materials in accordance with this invention may be
used in connection with other matrix protecting practices to
provide redundant protection against environmental damage. As
depicted in FIG. 21, a cementitious matrix including rebars may
include surface coatings and sealants to prevent the ingress of
harmful environmental liquids. Calcium nitrite anticorrosion
chemicals may be freely mixed within the cement and the smart fiber
reinforcements may be disposed immediately adjacent the rebar
containing additional anticorrosive modifying agents in accordance
with this invention for release as needed when the concentration of
corrosion chemicals get sufficiently high to stimulate their
release.
[0113] Referring now to FIGS. 22a through 22d, there is depicted a
special embodiment of the present invention wherein the notion of
smart fiber release and repair is coupled with specialty fibers. As
depicted in FIG. 22a through 22d, the smart fiber itself comprises
a piezoelectric fiber into which a liquid chemical is first applied
or deposited by providing an electric current to the piezoelectric
components of the fiber. The modifying chemicals accretes within
and on the surfaces of the web of fibers making up the solid
piezoelectric cylinders, which in turn hollow fibers which may be
placed and disposed within the matrix. In accordance with these
embodiments the modifying agents are released from the
piezoelectric fibers by the application of service load stresses on
the matrix. These generate electrical charges in the piezoelectric
fibers due to their piezoelectric character. The electrical charges
cause positive ions to move from inside the porous fibers into the
surrounding matrix. Negative ionic materials located in the matrix
may also be drawn into or attracted to the piezoelectric hollow
fiber. In this way repair can be done by dispersing charged ions
into the matrix or may through by selectively drawing undesired
materials into the fibers to remove them and causing damage to the
matrix.
[0114] Referring now to FIGS. 23a through 23d, another specialty
application for the smart fiber reinforced matrix materials in
accordance with this invention is shown, which include an
impermeable barrier equipped with smart sensors in addition to a
hollow fiber wrapped rebar composite in accordance with this
invention. The impermeable barrier may be connected to sensor
equipment shown as a feedback loop capable of detecting ingress of
moisture, changes in voltage or changes in chloride iron
concentration,
[0115] As shown in FIG. 23b, once the ingress of moisture is sensed
at the impermeable barrier layer, an electrical signal may be sent
through the inner barrier layer, causing discharge or migration of
cations from the middle layer towards the rebar, which causes a
coating on the smart fiber to be broken down to permit release of
the modifying agent contained therein of anticorrosion chemicals
into the immediate vicinity of the-rebar to prevent corrosion.
[0116] As depicted in FIG. 23c, the hollow smart fibers in
accordance with this invention are disposed in a region bounded by
the barrier layer on one side and the rebar on the other to provide
redundant backup protection to the rebar to prevent corrosion. More
particularly, the hollow fibers contain water binding chemicals
which effectively remove the damaging water from reaching the rebar
in that intermediate region, thereby preventing corrosion.
[0117] In FIG. 23d, an alternate aspect is provided wherein the
barrier is electrified to provide a galvanic cell in the immediate
region between the barrier layer and the rebar. A counter galvanic
cell is created about the hollow middle fibers which contain a
modifying chemical inside the buffer zone, which in turn can
release moisture binding hydroscopic chemicals in response to
application of electrical charges or may release anticorrosive
chemicals. In accordance with FIG. 23e, the hollow fibers disposed
within the barrier buffer zone may include zinc ions which will
migrate and coat the rebar in a galvanizing or electric lading
action by application of the voltage between the barrier and
rebar.
[0118] Referring now to FIGS. 24 and 24b, another specialty
embodiment of the invention includes the use of optical fibers as
the self-repairing fiber which in turn contains a modifying
chemical which may be positioned within the matrix. Twisted pair
fibers, for example, may be used as shown in FIGS. 24a and 24b. In
response to the application of applied loads, the optical fibers
may be changed in their transmission properties indicating a break
or leak in the matrix and may in turn be caused to discharge their
internal modifying agent into the surrounding matrix to, for
example, repair a microcrack as shown in FIG. 24d.
[0119] FIGS. 25a and 25b depict a similar embodiment involving the
use of glass hollow fibers as surrounding hollow fibers for
containing adhesive repair modifying agents and for housing an
optical fiber therein. As shown in FIG. 25b, microcracking of the
matrix causes release of the repair adhesive locally within the
matrix to prevent further cracking and breaking which might damage
the optical fiber and its transmission capability.
[0120] Referring now to FIGS. 26a and 26b, a different use of
optical fibers as the smart fibers in a matrix composite in
accordance with this invention is shown. More particularly, a
cladded optical fiber having an interior cavity filled with an
adhesive repair chemical is provided in a surrounding polymer or
cement matrix. The light transmission of the intact fiber is of a
given value. Once applied, loads are caused cracking and bending of
the matrix as shown in FIG. 26b which will cause bending of the
fibers decreasing the amount of light transmitted therethrough.
[0121] Referring now to FIGS. 27a and 27b, another glass fiber
embodiment is shown wherein an assembly including an outer hollow
glass tube filled with adhesive modifying agent and including an
optical fiber therein and a middle fiber therein provide a special
matrix composite. As shown in FIG. 27b, in response to an applied
load, the middle fiber bending assist in breaking the outer glass
tube to thereby release the repairing adhesive to the matrix. The
optical fiber polymer may be bent or stretched and light lost to
cladding coating on the fiber may be detected outside the matrix to
determine bending of the fibers and possible microcracking
therein.
[0122] Referring now to FIGS. 28a through 28c, another use-of an
optical fiber for forming the smart repair fibers in accordance
with this invention illustrates reliance on release of the repair
chemicals within the optical fiber to change the optical
characteristics to indicate that microcracking has occurred wherein
the change in volume of the repair material can indicate the volume
cracks that needed to be filled and the change in refracturing
index of light transmitted through the fiber may also give an
indication of the volume of the cracks that have been filled in
accordance with this invention.
[0123] Referring now to FIGS. 29a and 29b, a plurality of septums
or brag optical gradings may be positioned along the modifying
agent filled optical fiber in accordance with this invention to
permit the diagnostic detection of the location of cracks by
noticing changes in the refracturing index located between
gradings. FIGS. 29a and 29b illustrate a further preferred
embodiment employing optical fibers as the hollow fiber component
of the smart matrix materials in accordance with this invention.
The elongate optical fiber is subdivided into longitudinal segments
by dividers or septums over brag optical gradings which maintain
the optical transmission characteristics along the fiber when
filled with the chemical modifying agents. As depicted in FIG. 29b,
in the event of a breakage and leaking of the repair chemical into
the adjacent matrix, the dividers or septums limit the quantity of
fluid loss to a local segment only. The change in optical
characteristics in that local segment will still serve to identify
the location of the crack, while preventing an overall loss in all
of the fiber fluid contents.
[0124] Referring to FIGS. 30a-30d, still another optical fiber
hollow fiber embodiment of this invention is depicted employing
fibers of predetermined longitudinal length or dimension having a
mirror end well at one end thereof and having repair chemical
disposed therein. Checks on the integrity of the optical fiber
segment can be made by intermittently sending an optical pulse
along the short length of the fiber and bouncing it off the mirror
and comparing the reflected intensity to the transmitted intensity
to determine whether or not there has been a change along the
length of the fiber. By placing a mirror intermediate the length of
a row of fiber, the fiber sensing the optical sensing test could be
performed from either end and in that manner the location of the
break on one side of the mirror or the other could be
determined.
[0125] Referring now to FIG. 30c, the new and improved smart matrix
material is shown in a rebonded condition wherein the interior
modifying agent, in this case an adhesive, has leached into the
surrounding matrix to repair crack, to bond the matrix to itself,
and to bond the coating to the matrix and the coating to the fiber.
This restores the overall integrity of the composite, and in some
cases, may lead to actual increases in overall strength and
performance for the rebond material.
[0126] FIG. 30d illustrates the exterior refilling design in
accordance with the preferred embodiment for vacuum pump refilling
of a broken optical fiber to repair or restore optical transmission
service therealong.
[0127] In accordance with the present invention, other embodiments
for using the self-repairing fiber reinforcement smart matrix
composite matrix materials described herein will be readily
apparent to those skilled in this art. For example, employing
ceramic matrices such as a hydroxyapatite ceramic minerals and
reinforcing hollow fibers containing bio-compatible crack repairing
adhesives may be used in joint replacements or as shaped articles
for prosthetic devices. In this manner, biomedical embodiments for
the smart matrix composite materials possessing the self-repair
properties may be used to provide improved or extended fuselage to
prosthetic devices and bone replacements. Stress load fractures
occurring within the artificial bone or joint segment will
self-repair in accordance with the principles of this
invention.
[0128] In still another embodiment of the present invention, the
overall matrices may be used in building applications to provide
some seismic resistance or earthquake-proof properties to the
structures. More particularly, the response of a solid matrix
material containing rigid-filled fibers or liquid-filled fibers may
vary in response to seismic waves. Rheological fluids and
electrorheological fluids are known which are stiff in one
condition, and thereafter upon application of electrical current,
may become fluid or liquid. These fillings within reinforcing
fibers may be intentionally changed periods of seismic activity in
response to, for example, a sensor switch to liquefy or fluidize
building structures to better withstand seismic vibration activity
without causing brittleness. In the liquefied electrorheological
state, the overall matrix composite may be better able to withstand
energy vibration than might be encountered in the solid rigid
composite structure.
[0129] In still another aspect of the invention, it is known that
alkali reactions are sometimes caused within cementitious matrix
materials when aggregate reacts with matrix causes an expansion of
the aggregate against the matrix. This causes internal stresses to
develop within the matrix composite or shaped article, which
usually appears as cracks within the matrix. The use of the smart
fibers in accordance with the present invention containing
adhesives will repair some of these cracks. In addition, instead of
adhesives these smart fibers may be filled with pH modification
agents such as acidic agents to neutralize the alkali reaction. In
addition, fibers filled with the alkali reaction inhibiting acidic
modifying agent may be used in combination with the matrix repair
adhesive filled smart fibers in accordance with this invention.
[0130] In accordance with this invention, the matrix selected may
vary, for example, Ribtec.TM. mats of stainless steel fibers may be
slurry infiltrated with cement, hollow fibers for repair may be
included. Under loading, the mat causes the cement to form
microcracks, which in accordance with this invention releases the
repair adhesives into the matrix to provide a repaired high
toughness composite material. Depending on the matrix selected,
different fiber properties may be desired, for example, in rigid
matrix materials such as cementitious set materials or Sintrex
ceramic materials more flexible fibers may be desirable, whereas in
polymer matrices having inherent elasticity or flexibility, more
rigid fibers such as glass or metal fibers may be desired. In
addition, it may be desired to use fibers which become brittle over
time. Fibers may be connected to each other with flexible parts to
ensure that they do not break prematurely during mixing or
compounding. Furthermore, chemicals which survive the long periods
of time and which survive repeated temperature variations may also
be used as the modifying agents. Although several different matrix
materials have been disclosed or suggested herein, others may still
be used by those skilled in this art. Although a number of
different kinds of fibers have also been described, still other
fibers might also be used by those skilled in this art in
accordance with the principles of this invention. Different
modifying agents and different mechanisms for selective release of
the modifying agent in response to an external stimuli or internal
stresses caused by other external occurrences might also be
developed and designed by those skilled in the art given the
principles provided herein. Accordingly, all such obvious
modifications may be made herein without departing from the scope
and spirit of the present invention as defined by the appended
claims.
* * * * *