U.S. patent application number 13/487867 was filed with the patent office on 2012-11-29 for method of producing a 3d textile structure and semi-finished fiber product made of fiber composites.
This patent application is currently assigned to SGL CARBON SE. Invention is credited to FLORIAN H. GOJNY, HEIDE GOMMEL, THOMAS PUTZ, TOBIAS SCHMIDT.
Application Number | 20120301695 13/487867 |
Document ID | / |
Family ID | 43759767 |
Filed Date | 2012-11-29 |
United States Patent
Application |
20120301695 |
Kind Code |
A1 |
GOJNY; FLORIAN H. ; et
al. |
November 29, 2012 |
METHOD OF PRODUCING A 3D TEXTILE STRUCTURE AND SEMI-FINISHED FIBER
PRODUCT MADE OF FIBER COMPOSITES
Abstract
A three-dimensional (3D) textile structure with contours that
are matched to the 3D textile structure is formed by folding a 2D
textile structure. The three-dimensional textile structure has a
areal weight of 100-5000 g/m.sup.2. A semi-finished
three-dimensional fiber product is formed by infiltrating the 3D
textile structure with thermosetting and/or thermoplastic resins
and cured to form the three-dimensional semi-finished fiber
product. The semi-finished product is then usable to produce leaf
springs or profiles for the aerospace field, for the automobile
field, for wind energy, and for sports articles.
Inventors: |
GOJNY; FLORIAN H.;
(Kelkheim, DE) ; GOMMEL; HEIDE; (AUGSBURG, DE)
; PUTZ; THOMAS; (WESTENDORF, DE) ; SCHMIDT;
TOBIAS; (AUGSBURG, DE) |
Assignee: |
SGL CARBON SE
WIESBADEN
DE
|
Family ID: |
43759767 |
Appl. No.: |
13/487867 |
Filed: |
June 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2010/068875 |
Dec 3, 2010 |
|
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13487867 |
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Current U.S.
Class: |
428/219 ; 28/100;
428/221 |
Current CPC
Class: |
B29C 70/207 20130101;
B29C 53/04 20130101; B29B 11/16 20130101; Y10T 428/249921 20150401;
B29C 70/222 20130101 |
Class at
Publication: |
428/219 ;
428/221; 28/100 |
International
Class: |
D03D 13/00 20060101
D03D013/00; D04H 13/00 20060101 D04H013/00; D04H 3/04 20120101
D04H003/04; D04B 1/00 20060101 D04B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 4, 2009 |
DE |
10 2009 047 491.9 |
Claims
1. A method for producing a 3D textile structure, the method which
comprises providing a 2D textile structure and forming the 3D
textile structure having contours matched to the 3D textile
structure by folding the 2D textile structure.
2. The method according to claim 1, wherein the contours are one or
both of tracks or knitting patterns.
3. The method according to claim 1, wherein the folding step
comprises folding in a concertina manner.
4. The method according to claim 1, which comprises forming the 2D
textile structure with fold-assisting gaps to assist constructing
the semi-finished fiber product to the shape close to the final
contour.
5. The method according to claim 1, wherein the 2D textile
structure is selected from the group consisting of scrim, woven
fabric, networks, knitwear, felts, nonwovens, and combinations
thereof.
6. The method according to claim 1, wherein the 2D textile
structures are selected from the group consisting of glass fibers,
carbon fibers, aramid fibers, ceramic fibers, polymer fibers, metal
fibers or mixtures and combinations thereof.
7. The method according to claim 6, wherein at least one fiber
layer consists of more than 70 wt. % of fibers selected from carbon
fibers, precursor fibers of carbon fibers, ceramic fibers and
mixtures thereof, relative to a total weight of the respective
fiber layer.
8. The method according to claim 7, wherein the at least one fiber
layer consists of more than 87 wt. % of the selected fibers.
9. The method according to claim 8, wherein the at least one fiber
layer consists of more than 98 wt. % of the selected fibers.
10. The method according to claim 1, wherein the textile structure
consists of at least 50% of fibers in a principal direction of
loading of the three-dimensional semi-finished fiber product to be
produced.
11. The method according to claim 1, which comprises coating or
impregnating the textile structure with a matrix system or with a
plurality of matrix systems.
12. The method according to claim 11, wherein a content of the
matrix system for coating and/or impregnating the two-dimensional
textile structure ranges from 0% to 70%.
13. The method according to claim 11, wherein the textile structure
contains soluble polymers.
14. The method according to claim 1, which comprises transforming
the textile structure into a three-dimensional semi-finished fiber
product by applying strengthening methods selected from the group
of chemical, physical, and mechanical strengthening methods.
15. A three-dimensional textile structure, comprising a 3D
structure formed from a 2D textile structure having contours
matched to the 3D textile structure by folding the 2D textile,
wherein the 3D structure has a weight per unit area of 100-5000
g/m.sup.2.
16. The three-dimensional textile structure according to claim 15,
wherein the weight of the 3D structure is 500-2300 g/m.sup.2.
17. The three-dimensional textile structure according to claim 15,
wherein the weight per unit area is locally adapted by selectively
reducing or increasing an amount of fiber in the two-dimensional
fiber structure or by a separate process step.
18. A semi-finished three-dimensional fiber product, comprising a
3D structure manufactured by the method according to claim 1,
infiltrated with thermosetting and/or thermoplastic resins and
cured to form the three-dimensional semi-finished fiber
product.
19. The semi-finished three-dimensional fiber product according to
claim 15 configured for producing leaf springs or profiles for the
aerospace field, for the automobile field, for wind energy, and for
sports articles.
20. The three-dimensional textile structure according to claim 15,
wherein the two dimensional structure is already adapted to the
shape of the three-dimensional semi-finished fiber product close to
the final contour.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation, under 35 U.S.C.
.sctn.120, of copending international application
PCT/EP2010/068875, filed Dec. 3, 2010, which designated the United
States; this application also claims the priority, under 35 U.S.C.
.sctn.119, of German patent application No. DE 10 2009 047 491.9,
filed Dec. 4, 2009; the prior applications are herewith
incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a method for producing a 3D
textile structure and a semi-finished fiber product made of fiber
composites and the use thereof.
[0003] In order to produce composite materials, fibers can be used
in the form of woven or non-woven textile structures and in the
form of individual, loose fibers. Use of woven fabrics has the
advantages that fibers can be introduced in large quantities and
with a comparatively uniform distribution in the composite
material. In addition, the use of a woven fabric has the advantage
that the fibers are present in bound form in the woven fabric and
usually do not require any further fastening to one another. It is
a disadvantage however that the production of a woven fabric is
associated with high costs, in particular if sensitive or
difficult-to-weave fibers are used.
[0004] Compared to woven fabrics, fiber scrims have the advantage
that these can usually be manufactured far more cost-effectively.
At the same time, however, fiber scrims have only a very poor
cohesion which makes any processing of fiber scrims, particularly
on an industrial scale, very difficult. In order to improve the
cohesion of fiber scrims, for example, fiber layers can be
adhesively bonded, linked or woven by hot-melting binding threads
or interconnected by needling.
[0005] However, joining fiber layers by needling only results in
fiber scrims capable of withstanding comparatively low loading
while joining by adhesive bonding or by using hot-melting binding
threads brings with it the risk that at higher temperatures
cohesion of the fiber scrim is no longer given in sufficient
strength since the adhesive or the hot-melting binding threads melt
or decompose.
SUMMARY OF THE INVENTION
[0006] It is accordingly an object of the invention to provide a
method of producing a 3D textile structure and semi-finished fiber
product made of fiber composites which overcome various
disadvantages of the heretofore-known devices and methods of this
general type and which provides for an improved method that makes
it easier to produce three-dimensional semi-finished fiber products
made of fiber composites and in which the individual starting
material components of the composite material, i.e. the fiber
material component, the matrix material component and the fastener
components are matched to one another.
[0007] In other words, it is an object of the invention to provide
a method for producing a 3D textile structure (three-dimensional
semi-finished fiber product, preform) having contours matched to
the 3D textile structure by folding a 2D textile structure.
[0008] With the foregoing and other objects in view there is
provided, in accordance with the invention, a method for producing
a 3D textile structure, the method comprises providing a 2D textile
structure and forming the 3D textile structure having contours
matched to the 3D textile structure by folding the 2D textile
structure.
[0009] In a preferred embodiment of the invention, the contours are
tracks and/or knitting patterns. The structure is preferably folded
in a concertina manner.
[0010] The 2D textile structure has fold-assisting gaps which make
it easier to construct the semi-finished fiber product to the shape
close to the final contour.
[0011] It is preferred for the 2D textile structure to be selected
from the group consisting of scrim, woven fabric, networks,
knitwear, felts, nonwovens, combinations of the same and other
two-dimensional structures.
[0012] According to the invention, the 2D textile structures may
consist of glass fibers, carbon fibers, aramid fibers, ceramic
fibers, other polymer fibers, metal fibers or mixtures of the
aforesaid fibers.
[0013] In accordance with a preferred embodiment of the invention,
at least one fiber layer consists of more than 70 wt. %, preferably
more than 87 wt. %, particularly preferably more than 98 wt. % of
fibers, selected from carbon fibers, precursor fibers of carbon
fibers, ceramic fibers and mixtures thereof, relative to the total
weight of the particular fiber layer.
[0014] Advantageously, the textile structure consists of at least
50% of fibers in the principal direction of loading of the
three-dimensional semi-finished fiber product to be produced.
[0015] It is particularly advantageous if the textile structure is
coated and/or impregnated with a matrix system or with several
matrix systems. The content of the matrix system for coating and/or
impregnating the two-dimensional textile structure is at least 0%
to 70%.
[0016] In accordance with an additional feature of the invention,
the textile structure contains soluble polymers.
[0017] In accordance with another feature of the invention, the
textile structure can be transformed into a three-dimensional
semi-finished fiber products by applying of chemical, physical
and/or mechanical strengthening methods.
[0018] With the above and other objects in view there is also
provided, in accordance with the invention, a three-dimensional
textile structure having a weight per unit area of 100-5000
g/m.sup.2, preferably 500-2300 g/m.sup.2, which can be obtained by
a method according to one or more of the preceding claims.
[0019] The weight per unit area may be locally adapted by reducing
or increasing the amount of fiber in the two-dimensional fiber
structure or by a separate process step.
[0020] The three-dimensional semi-finished fiber product may be
infiltrated and cured with thermosetting and/or thermoplastic
resins.
[0021] In a preferred implementation, the three-dimensional
semi-finished fiber products as described herein are used to
produce leaf springs or profiles for the aerospace field, for the
automobile field, for wind energy, and/or sports articles.
[0022] In accordance with a concomitant feature of the invention,
the two dimensional structure is already adapted to the shape of
the three-dimensional semi-finished fiber product close to the
final contour.
[0023] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0024] Although the invention is illustrated and described herein
as embodied in production of a 3D textile structure and
semi-finished fiber product made of fiber composites, it is
nevertheless not intended to be limited to the details shown, since
various modifications and structural changes may be made therein
without departing from the spirit of the invention and within the
scope and range of equivalents of the claims.
[0025] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0026] FIG. 1 shows the folding of scrims in 2D structures; and
[0027] FIG. 2 shows the folding of scrims in 3D structures.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The figures of the drawing show in an explanatory and
non-restrictive manner a fiber-scrim reinforced composite material
according to the invention and a plurality of fiber scrims produced
as intermediate products during the process according to the
invention.
[0029] A 2D structure comes about in a woven fabric by the crossing
of warp and weft threads at right angles. In a scrim a 2D structure
is achieved by one or more fiber layers being arranged one above
the other with different fiber orientation and interconnected by
means of a warp thread system.
[0030] The folding is particularly preferably accomplished in a
concertina manner as a result of which the textile semi-finished
product is achieved. In so doing, the 2D structure is in each case
folded into itself by means of the inserted fold contours so that
the same side of the product always meets. A zigzag fold is thus
produced similar to a concertina.
[0031] It is further particularly preferred that the 2D textile
structure has fold-assisting gaps which make it easier to construct
the semi-finished fiber product to the shape close to the final
contour.
[0032] The preferred textile structure is selected from the group
consisting of scrim, woven fabric, networks, knitwear, felts,
nonwovens, combinations of the same and other two-dimensional
structures (e.g., films).
[0033] The scrim is optionally coated with a binder so that after
the folding process, a stabilized preform such as a leaf spring,
for example, is obtained by a thermal forming process.
[0034] The textile structure preferably consists of glass fibers,
carbon fibers, aramid fibers, ceramic fibers, other polymer fibers
(e.g. polyester, HD polyethylene or polyamides), metal fibers or
mixtures of the foregoing fibers.
[0035] The term "carbon fiber" as used within the framework of the
present specification comprises any carbon fiber which was
manufactured starting from a carbon-containing starting material
fiber, for example, a polyacrylonitrile-based fiber, a
polyacetylene-based fiber, a polyphenylene-based fiber, a
pitch-based fiber or a cellulose-based fiber, where this term can
in particular comprise fibers having a carbon content of more than
75 wt. %, preferably more than 85 wt. %, preferably more than 92
wt. %, in each case relative to the total weight of the fiber.
[0036] Manufacturing methods for polyacrylonitrile fibers,
pre-oxidized polyacrylonitrile fibers and carbon fibers
manufactured from these are described, for example, in the
publication by E. Fizter, L. M. Manocha, "Carbon Reinforcements and
Carbon/Carbon Composites", Springer Verlag, Berlin, 1998, ISBN
3-540-62933-5, p. 10-24 and in the patent documents U.S. Pat. No.
4,001,382, U.S. Pat. No. 6,326,451, EP 0 384 299 B1 and U.S. Pat.
No. 6,054,214.
[0037] Methods for manufacturing phenol resin fibers and the
manufacture of binding threads from these threads are known to
those of skill in the pertinent art. In addition, such methods are
described, for example, in German published patent applications DE
2 308 827 and DE 2 328 313.
[0038] For example, oxide and/or non-oxide fibers based on one or
more compounds comprising at least one, preferably at least two, of
the elements carbon, silicon, boron, titanium, zirconium, tungsten,
aluminum and nitrogen, can be used as ceramic fibers, for example,
for fiber layers.
[0039] The term "fiber layer" as used in the present application
comprises any layer or ply of fibers of any materials or material
mixtures. A fiber layer can in particular comprise a unidirectional
layer or setting layer, that is a fiber layer which, for example,
comprises a plurality of filaments or yarns which usually extend
parallel or substantially parallel in one direction. This can be
accomplished, for example, by spreading out a cable or an arbitrary
parallel arrangement of filaments or yarns. In addition, the term
fiber layer also comprises fiber layers having an arbitrary
arrangement or arbitrary profile of filaments or fiber sections of
shorter length, for example, a nonwoven layer. In particular, the
fiber layers can also have different length and/or width dimensions
or a different shape.
[0040] Preferably the ceramic fibers consist completely or of at
least 90 wt. % relative to the total weight of the ceramic fibers
of compounds comprising at least two of the elements carbon (C),
silicon (Si), boron (B), titanium (Ti), zirconium (Zr), tungsten
(W), aluminum (Al) and nitrogen (N).
[0041] In particular, ceramic fibers can be used in which the sum
of the content of C, Si, B, N, Al, Zr, Ti, W is more than 50 wt. %,
preferably more than 83 wt. %, preferably more than 85 wt. %, in
particular more than 95 wt. % of the total weight of the ceramic
fibers, where the content of one or more of C, Si, B, N, Al, Zr,
Ti, W can be 0 wt. %.
[0042] For example, fibers, in particular fibers highly resistant
to elevated temperatures, based on Si, C, B, N, Al or compounds
thereof (where these fibers are designated, for example, in German
patent DE 197 11 829 C1 as "Si/C/B/N fibers") and in particular
ceramic fibers based on compounds comprising at least two of these
elements are used. Such fibers are described, for example in German
patent DE 197 11 829 C1.
[0043] Ceramic fibers can comprise, for example, at least one
compound selected from aluminum oxide, zirconium oxide, SiNC,
SiBNC, SiC, B.sub.4C, BN, Si.sub.3N.sub.4, TiC, WC and mixtures
thereof, or can consist completely of this or of at least 90 wt. %,
preferably of at least 93 wt. % in relation to the total weight of
fibers. In particular, ceramic fibers can comprise basalt fibers
and/or glass fibers or a mixture hereof with other ceramic
fibers.
[0044] The contours are particularly preferably tracks and/or
knitting patterns which allow the intended folding. This is
accomplished by omitting one or more fiber yarns in each case in
the 0.degree. direction or by splitting the textile by modifying
the connecting knitting threads.
[0045] As a result of the scrim according to the invention having
tracks introduced in the longitudinal and/or transverse direction,
the folding is in particular made possible in the case of heavy
scrims.
[0046] A single fiber layer or unidirectional layer can have an
area-related weight in the range of, for example, 50 g/m.sup.2 to
500 g/m.sup.2, preferably in a range of 150 g/m.sup.2 to 2000
g/m.sup.2. Depending on the desired end product, it can be
particularly preferred to select one or more fiber layers or
unidirectional layers having an area-related weight of at least 305
g/m.sup.2.
[0047] When using carbon fibers and/or precursor fibers, both
fibers which were obtained starting from polyacrylonitrile but also
starting from pitch or phenol resin fibers yielded a fiber layer
having a very good mechanical loading capacity.
[0048] The diameter of the filaments of at least one fiber layer or
unidirectional layer, preferably of all fiber layers or
unidirectional layers, can lie in a range of, for example, from 6
to 8 .mu.m.
[0049] At least one fiber layer preferably consists of more than 70
wt. %, further preferably more than 87 wt. %, particularly
preferably more than 98 wt. % of fibers, selected from carbon
fibers, precursor fibers of carbon fibers, ceramic fibers and
mixtures thereof, relative to the total weight of the particular
fiber layer.
[0050] In addition to carbon fibers, their precursor fibers and
ceramic fibers, the fiber layers can comprise any fibers which a
person skilled in the art can select on the basis of his general
technical knowledge and the teaching of the present invention.
[0051] The textile structure preferably consists of at least 50% of
fibers in the principal direction of loading of the
three-dimensional semi-finished fiber product to be produced.
[0052] The two-dimensional textile structure is preferably coated
and/or impregnated with a matrix system or with several matrix
systems (liquid/solid) after knitting.
[0053] The content of the matrix system for coating and/or
impregnating the two-dimensional textile structure is preferably at
least 0% to 70%. The textile structure preferably contains soluble
polymers (e.g. PVA, polyphenoxy).
[0054] The textile structure can be transformed into a
three-dimensional semi-finished fiber product (preform) by applying
chemical, physical (chemical reaction, pressure and/or temperature)
and/or mechanical strengthening methods (sewing, needling).
[0055] The two-dimensional (quasi two-dimensional) textile
structure having a weight per unit area of 100-5000 g/m.sup.2,
preferably 500-2300 g/m.sup.2, can be obtained by a method
according to one or more of the preceding claims.
[0056] The weight per unit area is preferably locally adapted by
reducing or increasing the amount of fiber in the two-dimensional
(quasi-two-dimensional) fiber structure or by a separate process
step.
[0057] The three-dimensional semi-finished fiber product can be
infiltrated and cured with thermosetting and/or thermoplastic
resins.
[0058] Fiber scrims having very advantageous properties can be
obtained, for example, if at least one fiber layer, in particular a
unidirectional layer, preferably all the fiber layers, have a
number of filaments which lies in the range of 0.5 K (500
filaments) to 500 K (500,000 filaments). Preferably, the number of
filaments of a fiber layer or unidirectional layer lies in a range
of 1 K (1000 filaments) to 400 K (400,000 filaments), preferably in
a range of 12 K (12,000 filaments) to 60 K (60,000 filaments).
[0059] Fiber scrims having advantageous material properties and
comparatively low manufacturing costs can further be obtained if
one or more fiber layers, in particular unidirectional layers are
used, which comprises polymer fibers, in particular organic polymer
fibers, or mixtures thereof. In some applications, it can also
prove advantageous to use polyacrylonitrile-based fibers,
viscose-based fibers, to produce at least one fiber layer. One,
two, three or more of the fiber layers can, for example, consist
completely or of at least 80 wt. % of polyacrylonitrile fibers
and/or viscose fibers relative to the total weight of fibers in the
fiber layer.
[0060] Fiber scrims having different material properties can be
obtained by producing fiber scrims comprising two, three, four,
five, six, seven, eight or arbitrarily more fiber layers and/or
unidirectional layers. In order to achieve highly loadable material
it can be advantageous if one unidirectional layer extends in a
different longitudinal direction from the unidirectional layer
located in each case above and/or below this unidirectional layer.
Preferably all the unidirectional layers in a fiber scrim extend in
a respectively different longitudinal direction. it can be
advantageous here if at least the longitudinal direction of one
unidirectional layer forms an angle of at least 30.degree.,
preferably at least 45.degree., preferably at least 60.degree., in
particular 85-90.degree. to the longitudinal direction of at least
one following unidirectional layer.
[0061] If the unidirectional layers each have different
longitudinal directions from one another, biaxial fiber scrims are
obtained when using two unidirectional layers, triaxial fiber
scrims are obtained when using three unidirectional layers,
quadraxial fiber scrims are obtained when using four unidirectional
layers.
[0062] Preferably when using two or more unidirectional layers, the
two or more other unidirectional layers are arranged in such a
manner that their respective longitudinal directions form angles
having opposite signs to the 0.degree. direction, where the
magnitude of the angles can be the same (and the angles can, for
example, be +60.degree./-60.degree. or) +45.degree./-45.degree. or
different or their respective longitudinal directions to the
0.degree. direction are at angles of 0.degree. and 90.degree..
[0063] Preferably a 0/90 scrim is produced on a scrim machine, in
which at least 90% of the fibers, particularly preferably 95% of
the fibers are disposed in the 0.degree. direction. The width and
the fiber weight per unit area of the scrim according to the
invention is determined by the fiber titer (fiber tester) used, the
layer structure provided, the resulting number of layers and their
width.
[0064] It is a surprising advantage of the method according to the
invention that the total width of a, for example, fast-running
scrim machine can be used. This is, for example also a particular
advantage compared with ribbon looms.
[0065] Resins which are particularly suitable for impregnating
fiber scrims are, for example, phenol resins, epoxide resins,
benzoxane resins, cyanate ester resins, polyester/vinyl ester
resins, furan resins, polyamide resins, polyimide resins,
polyacrylate resins, derivatives therefrom and mixtures
thereof.
[0066] In addition, inorganic impregnating agents can be used for
impregnating the fiber scrim, where, for example, liquid silicon,
SiC precursor polymers, in particular silazanes, SiC precursor
oligomers and mixtures thereof are particularly suitable for
impregnating the fiber scrim.
[0067] The term "SiC precursor polymer" as used within the
framework of the present specification describes any compound
having a molecular mass of more than about 300 g/mol which
comprises silicon, as well as carbon and/or nitrogen and for
example, can have a content of 10 to 99 wt. % of Si, relative to
the total weight of the compound. The term "SiC precursor oligomer"
as used within the framework of the present invention describes any
compound which comprises silicon, as well as carbon and/or
nitrogen, which has at least two silicon atoms and has a molecular
mass of up to and including about 300 g/mol, and for example, can
have a content of 10 to 99 wt. % of Si, relative to the total
weight of the compound. Preferably a SiC precursor polymer or a SiC
precursor polymer is at least partially converted into SiC when
heated to a temperature of more than 150.degree. C. in an inert
atmosphere.
[0068] When impregnating fiber scrims, for example, very good
results can be obtained by using at least one compound selected
from the group consisting of oligosilazanes, polysilazanes,
oligocarbosilazanes, polycarbosilazanes, oligosilanes, polysilanes,
oligoborocarbosilazanes, polyborocarbosilazanes,
methyl-oligosiloxanes, methyl-polysiloxanes, oligocarbosilanes,
polycarbosilanes, oligoborosilazanes, polyborosilazanes,
oligo(dialkyl)silicones, poly(dialkyl)silicones, oligosiloxanes,
polysiloxanes, for example poly(dialkyl)siloxanes, such as
poly(dimethyl)siloxanes, for example, poly(diaryl)siloxanes, such
as poly(diphenyl)siloxanes, for example,
poly(monoalkyl-monoaryl)siloxanes, such as
poly(monomethyl-monophenyl)siloxanes, derivatives thereof and
mixtures thereof. The terms oligosilazanes, oligocarbosilazanes,
oligosilanes, oligoborocarbosilazanes, methyl-oligosiloxanes,
oligocarbosilanes, oligoborosilazanes, oligo(dialkyl)silicones,
oligosiloxanes, etc. comprise any oligomer coming under the term,
which is constructed from at least two monomer units, that is, any
oligomer beginning with one dimer as far as compounds having a
molecular weight up to an including about 300 g/mol.
[0069] The terms polysilazanes, polycarbosilazanes, polysilanes,
polyborocarbosilazanes, methyl-polysiloxanes, polycarbosilanes,
polyborosilazanes, poly(dialkyl)silicones, polysiloxanes, etc.
comprise any polymer falling under the term that has a molecular
weight of more than about 300 g/mol.
[0070] A fiber scrim can additionally be impregnated with inorganic
impregnating agents and also with resins, preferably synthetic
resins. For example, neighboring sections of a fiber scrim can be
impregnated with one or more inorganic impregnating agents and/or
with one of more resins. For example, an impregnation can
additionally be accomplished in several layers or in a sequence of
impregnating processes using one or more inorganic impregnating
agents and/or using one or more resins and/or an impregnation can
be made using mixtures of one or more inorganic impregnating agents
and resins. The choice of curing conditions takes into account the
requirements of the selected impregnating agent.
[0071] The curing of the impregnated fiber scrim can take place in
a curing temperature range of at least 40.degree. C., at a curing
temperature in the range of 50 to 260.degree. C., preferably 80 to
200.degree. C. The curing can preferably take place before
commencement of and/or at least during a subperiod of the curing
time under pressure, for example, by pressing at least one surface
section of at least one surface of the impregnated fiber scrim with
a pressing tool. The curing time can, for example, be at least 1
minute, preferably between 10 minutes and 8 hours, preferably
between 15 minutes and 3 hours. The curing time under pressure can,
for example, be in a range of at least 1 minute, preferably between
10 minutes and 8 hours, preferably between 15 minutes and 3 hours.
The pressing pressure can, for example, be at least 0.01 MPa,
preferably 0.01 MPa to 100 MPa.
[0072] The content of resin and/or inorganic impregnating agents,
relative to the total weight of the non-impregnated fiber scrim,
can lie in a range of 5 to 85 wt. %, preferably of 25 to 65 wt. %,
particularly preferably of 30 to 45 wt. %.
[0073] The fiber scrim can, for example, be impregnated as far as
saturation of the fiber scrim. In particular, liquid resins or
molten resins ("hot melt resin") can be used, which can for example
comprise phenol resins.
[0074] The curing and impregnation can be carried out using any
method known for this to the person skilled in the art. Very
advantageous results can be obtained if the impregnation is carried
out by dipping in a dipping bath or by means of a film transfer
method. For example, these process steps can be carried out
continuously, that is, the woven fabric can, for example, be
unrolled from a roll, passed through one or more furnaces having a
suitable temperature and atmosphere such as, for example,
400.degree. C. or more in an inert atmosphere and then passed
further through a resin bath and/or a bath containing inorganic
impregnating agent, and/or roll calendars and/or another
impregnating device. A curing can then take place, where a
composite material is obtained whose matrix is reinforced by a
fiber scrim, for example, a carbon fiber scrim. The curing process
step can be carried out both continuously and discontinuously. The
cured resin and/or the cured inorganic impregnating agent fulfils
several functions in the composite material obtained after the
curing. Firstly, the resin makes connections between the cables and
threads of the fiber scrim and fixes their position in the woven
fabric. Depending on the application of the composite material, the
fiber scrim can be embedded in a matrix comprising cured resin
and/or inorganic impregnating agent, completely or in sections
and/or it can be covered with a film of resin and/or inorganic
impregnating agent merely covering individual fibers, completely or
in sections and/or it can be free of resin in sections. The cured
binder additionally effects a mechanical reinforcement of the fiber
scrim.
[0075] After the curing and/or pressing, a fiber-scrim-reinforced
composite material or a fiber-scrim-reinforced composite material
product can be obtained.
[0076] A fiber-scrim-reinforced composite material product within
the framework of the present application designates a partially or
preferably completely cured fiber-scrim-reinforced composite
material which has optionally been subject to further processing
steps, for example, cutting to size, shape cutting etc. Within the
framework of the present application a cured fiber-scrim-reinforced
composite material is also designated as green body.
[0077] Optionally, the partially or completely cured
fiber-scrim-reinforced composite material, even without an
interposed step of obtaining, or the partially or completely cured
fiber-scrim-reinforced composite material product can undergo
further process steps such as, inter alia, a thermal treatment, for
example, for carbonizing or graphitizing or an extensive heating
and/or pressing.
[0078] A thermal treatment can be carried out in a first
temperature range (frequently also designated as "carbonization")
and can, for example, be carried out by heating with the exclusion
of oxidizing substances, i.e. either in an inert atmosphere, in
protective gas or by enveloping the material to be combusted with a
substance acting as a getter, which binds oxidizing media,
especially oxygen, at a temperature or in a temperature range from
about 800.degree. C. to about 1250.degree. C., preferably from
850.degree. C. to 950.degree. C., in particular from 880.degree. C.
to 920.degree. C. The thermal treatment in the first temperature
range can take place during a time interval of, for example, at
least 30 minutes, preferably of at least 8 hours, in particular
from 30 minutes to 96 hours. Any method known to the person skilled
in the art can be used for the thermal treatment in a first
temperature range ("carbonization") within the framework of the
teaching of the present invention, for example, a solid phase
pyrolysis. In order to achieve a good coke yield, a heating-up
phase can be executed first, for example, with a comparatively
small temperature gradient in the range from 300 to 600.degree. C.
at a maximum of 4.degree. C. per hour or coking is carried out
under pressure. The final temperature in this process step cannot
exceed, for example, 1250.degree. C.
[0079] Both a completely and also an only partially cured
fiber-scrim-reinforced composite material can be subjected to the
thermal treatment in a first temperature range.
[0080] After the thermal treatment in the first temperature range,
a composite material is obtained whose matrix comprises carbon and
is reinforced with a carbon fiber woven fabric ("carbon fiber
reinforced carbon", CFC).
[0081] Alternatively to the thermal treatment in a first
temperature range or additionally to this, in particular after
this, a thermal treatment can be carried out in a second
temperature range (frequently also designated as "graphitization").
The thermal treatment in a second temperature range
("graphitization") can be carried out by any method known for this
to the person skilled in the art. In particular, heating can be
carried out in an inert atmosphere at a temperature in the range
from about 1251.degree. C. to 3000.degree. C., preferably from
1800.degree. C. to 2200.degree. C. during a time interval of, for
example, at least about 30 minutes, preferably of at least 8 hours,
in particular from 30 minutes to 96 hours.
[0082] During a thermal treatment in the first and/or second
temperature range, the resin layer shrinks as a result of the
weight loss due to the cleaving of volatile components. The
composite material obtained after the thermal treatment is
characterized by a high temperature resistance.
[0083] After the thermal treatment of the fiber-scrim-reinforced
composite material or composite material product, a thermally
treatment fiber-scrim-reinforced composite material or composite
material product can be obtained. Optionally the composite material
obtained after one or more thermal treatments in a first and/or
second temperature range, in particular a composite material
comprising fiber-scrim-reinforced carbon can be additionally
subjected once or several times to an after-treatment, in
particular an after-treatment in which the composite material is
impregnated at least once, in particular is impregnated with a
carbonizable agent, and/or is subjected at least one again to a
thermal treatment in a first and/or second temperature range (which
is usually designated as after burn). The post-compaction, in
particular the steps of impregnation and thermal treatment, can
fundamentally be carried out by any method known for this to the
person skilled in the art within the framework of the teaching of
the present invention. The term post-compaction as used within the
framework of the present invention designates any treatment of a
material or workpiece which results in a maintaining of or increase
in the density of the treated material or workpiece. Advantageously
an increase in the density can be accomplished by such
aftertreatment. The impregnation and the thermal treatment can
particularly advantageously be carried out under the conditions
explained hereinbefore and hereinafter. The so-called vacuum
pressure method can be used, for example, for the impregnation.
[0084] All substances known for an impregnation of parts comprising
carbon or consisting thereof, can be used as impregnating agents,
for example, substances having a coke yield of more than 30 weight
percent, for example, synthetic resins, in particular thermosetting
resins or pitches and derivatives derived therefrom as well as
mixtures or resins and pitches and/or pitch derivatives. In
particular, phenol resins of the novolak or resol type, furan
resins or impregnating pitches can be used. A thermal treatment in
a first and/or second temperature range as defined previously
following the impregnation, so-called after-burning, is carried out
with the exclusion of oxidising substances, in particular in an
inert atmosphere.
[0085] Prior to and/or after the thermal treatment in a first
and/or second temperature range, a heating or cooling of, for
example, 8 to 10 hours, for example to room temperature (20.degree.
C.) can be carried out. Example and preferred time intervals and
temperature ranges for a thermal treatment in a first and/or second
temperature range are explained in detail hereinbefore. In this
process step one or several carbon shells should be applied to the
already existing shell and after the first carbonization step,
cracks and pores still present in the first shell should be closed.
Depending on the intended protective effect for the fibers, this
impregnation and after-burning process can take place several
times, preferably once to three times.
[0086] It can be advantageous for optimisation of the composite
material in specific applications if a first thermal treatment in a
first temperature range in which carbonization can take place is
followed by a thermal treatment in a second temperature range in an
inert atmosphere in which graphitization takes place. However, the
execution of such a measure is merely optional. Usually the end
temperature of 3000.degree. C., in particular 2400.degree. C., is
not exceeded during graphitisation.
[0087] It is preferable to work at temperatures from 1800 to
2200.degree. C. All known graphitization processes can be used for
this step.
[0088] The post-compaction described hereinbefore which comprises
firstly an impregnation and then a burning process can be repeated
once or several times.
[0089] The number of post-compactions to be carried out is
dependent on the desired target density of the carbon
fiber-reinforced carbon ceramic and can be carried out once or
several times, for example, twice, three times or four times or
more, preferably in a directly successive manner. Preferably the
steps of impregnation and subsequent burning are each carried out
three times. After post-compaction, densities for example of
1.30-1.60 g/cm.sup.3, preferably of 1.30-1.55 g/cm.sup.3 can be
achieved.
[0090] Furthermore, the composite material comprising
fiber-scrim-reinforced carbon obtained after one or more thermal
treatments and/or post-compacted as explained hereinbefore can
optionally be provided with a gas phase coating by the CVD method
(CVD=chemical vapor deposition) or by the CVI method (CVI=chemical
vapor infiltration) with protective layers of high-melting
substances such as pyrocarbon, TiC, TiN or SiC. Any CVD/CVI method
known to a person skilled in the art can be used within the
framework of the preceding invention. CVD/CVI methods are, for
example, taught in the document DE 39 33 039 A1 or in the
publication E. Fitzer et. al., Chemie-Ingenieur-Technik 57, No. 9,
p. 737-746 (1985).
[0091] In addition, the composite material comprising
fiber-scrim-reinforced carbon obtained after a thermal treatment in
a first and/or second temperature range and/or post-compacted as
explained hereinbefore and/or additionally coated by the CVD method
or by the CVI method can be subjected to siliconizing. Such a
process is described for example in the publication E. Fitzer et.
al., Chemie-Ingenieur-Technik 57, No. 9, p. 737-746 (1985).
[0092] Siliconization can be carried out within the framework of
the present invention by any method known to a person skilled in
the art. Composite materials of particularly high quality can be
obtained, for example, if the siliconization is carried out in the
temperature range from 1450.degree. C. to 2200.degree. C.,
preferably in the temperature range from 1650.degree. C. to
1750.degree. C. in an inert atmosphere. In particular it is
possible to work in the temperature range from 1650.degree. C. to
1750.degree. C. in vacuum. After reaching the siliconization
temperature, the time interval for infiltration and reacting to
give SiC can be at least 10 minutes, for example, 10 minutes to 1
hour.
[0093] In the case of siliconization without using vacuum,
siliconization can be carried out in particular at temperatures
from 2100.degree. C. to 2200.degree. C. in an inert atmosphere. The
total of infiltration and reaction time also during a
siliconization without using vacuum can be at least 10 minutes, for
example, between 10 minutes and one hour.
[0094] Advantageously the previously described siliconizations can
be carried out using the so-called wick technique. In this case,
the bodies to be siliconized lie on porous highly absorbent carbon
bodies in relation to the silicon, whose lower part stands in
liquid silicon. The silicon then rises through this wick body into
the bodies to be siliconized without the latter having a direct
connection with the silicon bath.
[0095] The previously explained steps of post-compaction, in
particular by impregnation and optional, subsequent thermal
treatment in a first and/or second temperature range,
siliconization and gas-phase coating can each be repeated once or
several times and combined with one another in any sequence.
[0096] Composite materials having particularly high quality can be
obtained, for example, if, following the step of curing and
optionally pressing the impregnated fiber scrim and a thermal
treatment in a first temperature range in which carbonization can
take place, the previously described steps of impregnation and
thermal treatment in a first and/or second temperature range
through which post-compaction can be achieved, are executed at
least once, preferably once to three times, preferably three
times.
[0097] Optionally a siliconization or a gas-phase coating or a
siliconization followed by a gas-phase coating can then
additionally be carried out. The gas-phase coating can in
particular be carried out with carbon or carbon-comprising
mixtures, by means of a CVD or CVI process, as described
hereinbefore.
[0098] The three-dimensional semi-finished fiber product is
preferably used for leaf springs or profiles (e.g. T profiles or
stringers) for the aerospace field, for the automobile field, for
wind energy and sports articles as a result of the low weight, the
high flexibility and loading capacity.
[0099] The textile structure is preferably already adapted or
machined (e.g. contour machining or cutouts) in the two-dimensional
(quasi two-dimensional) textile structure to the shape of the
three-dimensional semi-finished fiber product close to the final
contour.
* * * * *