Note: Descriptions are shown in the official language in which they were submitted.
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WO 2011/067390 Al
PRODUCTION OF A 3D TEXTILE STRUCTURE AND SEMI-FINISHED
FIBRE PRODUCT MADE OF FIBRE COMPOSITES
The present invention relates to a method for producing
a 3D textile structure and a semi-finished fibre
product made of fibre composites and the use thereof.
In order to produce composite materials, fibres can be
used in the form of woven or non-woven textile
structures and in the form of individual, loose fibres.
Use of woven fabrics has the advantages that fibres 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 fibres 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 fibres are used.
Compared to woven fabrics, fibre scrims have the
advantage that these can usually be manufactured far
more cost-effectively. At the same time, however, fibre
scrims have only a very poor cohesion which makes any
processing of fibre scrims, particularly on an
industrial scale, very difficult. In order to improve
the cohesion of fibre scrims, for example, fibre layers
can be adhesively bonded, linked or woven by hot-
melting binding threads or interconnected by needling.
However, joining fibre layers by needling only results
in fibre scrims capable of withstanding comparatively
low loading whilst joining by adhesive bonding or by
using hot-melting binding threads brings with it the
risk that at higher temperatures cohesion of the fibre
scrim is no longer given in sufficient strength since
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the adhesive or the hot-melting binding threads melt or
decompose.
In the present field of technology, there is therefore
a need for the development of another method that makes
it easier to produce three-dimensional semi-finished
fibre products made of fibre composites and in which
the individual starting material components of the
composite material, i.e. the fibre material component,
the matrix material component and the fastener
components are matched to one another.
Appended figures show in an explanatory and non-
restrictive manner a fibre-scrim reinforced composite
material according to the invention and a plurality of
fibre scrims produced as intermediate products during
the method according to the invention:
Fig. 1 shows the folding of scrims in 2D structures.
Fig. 2 shows the folding of scrims in 3D structures.
It is therefore the object of the invention to provide
a method for producing a 3D textile structure (three-
dimensional semi-finished fibre product, preform)
having contours matched to the 3D textile structure by
folding a 2D textile structure.
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 fibre
layers being arranged one above the other with
different fibre orientation and interconnected by means
of a warp thread system.
The folding is particularly preferably accomplished in
a concertina manner as a result of which the textile
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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.
It is further particularly preferred that the 2D
textile structure has fold-assisting gaps which make it
easier to construct the semi-finished fibre product to
the shape close to the final contour.
The textile structure preferably consists of the group
of scrim, woven fabric, networks, knitwear, felts,
nonwovens, combinations of the same and other two-
dimensional structures (e.g. films).
The scrim is optionally coated with a binder so that
after the folding process, a stabilised preform such as
a leaf spring, for example, is obtained by a thermal
forming process.
The textile structure preferably consists of glass
fibres, carbon fibres, aramid fibres, ceramic fibres,
other polymer fibres (e.g. polyester, HD polyethylene
or polyamides), metal fibres or mixtures of the
aforesaid fibres.
The term "carbon fibre" as used within the framework of
the present application comprises any carbon fibre
which was manufactured starting from a carbon-
containing starting material fibre, for example, a
polyacrylonitrile-based fibre, a polyacetylene-based
fibre, a polyphenylene-based fibre, a pitch-based fibre
or a cellulose-based fibre, where this term can in
particular comprise fibres having a carbon content of
more than 75 wt.., preferably more than 85 wt.o,
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preferably more than 92 wt.., in each case relative to
the total weight of the fibre.
Manufacturing methods for polyacrylonitrile fibres,
pre-oxidised polyacrylonitrile fibres and carbon fibres
manufactured from these are explained, 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 documents US 4,001,382, US 6,326,451, EP 0 384
299 B1 and US 6,054,214.
Methods for manufacturing phenol resin fibres and the
manufacture of binding threads from these threads are
known to the person skilled in the art. In addition,
such methods are described, for example, in the
documents DE 2 308 827 and DE 2 328 313.
For example, oxide and/or non-oxide fibres based on one
or more compounds comprising at least one, preferably
at least two, of the elements carbon, silicon, boron,
titanium, zirconium, tungsten, aluminium and nitrogen,
can be used as ceramic fibres, for example, for fibre
layers.
The term "fibre layer" as used in the present
application comprises any layer or ply of fibres of any
materials or material mixtures. A fibre layer can in
particular comprise a unidirectional layer or setting
layer, that is a fibre 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 fibre layer also comprises fibre layers having an
arbitrary arrangement or arbitrary profile of filaments
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or fibre sections of shorter length, for example, a
nonwoven layer. In particular, the fibre layers can
also have different length and/or width dimensions or a
different shape.
Preferably the ceramic fibres consist completely or of
at least 90 wt.o relative to the total weight of the
ceramic fibres of compounds comprising at least two of
the elements carbon (C), silicon (Si), boron (B),
titanium (Ti), zirconium (Zr), tungsten (W), aluminium
(Al) and nitrogen (N).
In particular, ceramic fibres can be used in which the
sum of the content of C, Si, B, N, Al, Zr, Ti, W is
more than 50 wt.o, preferably more than 83 wt.a,
preferably more than 85 wt.a, in particular more than
95 wt.% of the total weight of the ceramic fibres,
where the content of one or more of C, Si, B, N, Al,
Zr, Ti, W can be 0 wt.a.
For example, fibres, in particular fibres highly
resistant to elevated temperatures, based on Si, C, B,
N, Al or compounds thereof (where these fibres are
designated, for example, in the document DE 197 11 829
C1 as "Si/C/B/N fibres") and in particular ceramic
fibres based on compounds comprising at least two of
these elements are used. Such fibres are described, for
example in the document DE 197 11 829 Cl.
Ceramic fibres can comprise, for example, at least one
compound selected from aluminium oxide, zirconium
oxide, SiNC, SiBNC, SiC, B4C, BN, Si3N4, TiC, WC and
mixtures thereof, or can consist completely of this or
of at least 90 wt.o, preferably of at least 93 wt.a in
relation to the total weight of fibres. In particular,
ceramic fibres can comprise basalt fibres and/or glass
fibres or a mixture hereof with other ceramic fibres.
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The contours are particularly preferably tracks and/or
knitting patterns which allow the intended folding.
This is accomplished by omitting one or more fibre
yarns in each case in the 00 direction or by splitting
the textile by modifying the connecting knitting
threads.
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.
A single fibre layer or unidirectional layer can have
an area-related weight in the range of, for example,
50 g/m2 to 500 g/m2, preferably in a range of 150 g/m2
to 2000 g/m2. Depending on the desired end product, it
can be particularly preferred to select one or more
fibre layers or unidirectional layers having an area-
related weight of at least 305 g/m2.
When using carbon fibres and/or precursor fibres, both
fibres which were obtained starting from
polyacrylonitrile but also starting from pitch or
phenol resin fibres yielded a fibre layer having a very
good mechanical loading capacity.
The diameter of the filaments of at least one fibre
layer or unidirectional layer, preferably of all fibre
layers or unidirectional layers, can lie in a range of,
for example, from 6 to 8 pm.
At least one fibre layer preferably consists of more
than 70 wt.o, further preferably more than 87 wt.o,
particularly preferably more than 98 wt.o of fibres,
selected from carbon fibres, precursor fibres of carbon
fibres, ceramic fibres and mixtures thereof, relative
to the total weight of the particular fibre layer.
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In addition to carbon fibres, their precursor fibres
and ceramic fibres, the fibre layers can comprise any
fibres which a person skilled in the art can select on
the basis of his general technical knowledge and the
teaching of the present invention.
The textile structure preferably consists of at least
500 of fibres in the principal direction of loading of
the three-dimensional semi-finished fibre product to be
produced.
The two-dimensional textile structure is preferably
coated and/or impregnated with a matrix system or with
several matrix systems (liquid/solid) after knitting.
The content of the matrix system for coating and/or
impregnating the two-dimensional textile structure is
preferably at least 0% to 700. The textile structure
preferably contains soluble polymers (e.g. PVA,
polyphenoxy).
The textile structure can be transformed into a three-
dimensional semi-finished fibre product (preform) by
applying chemical, physical (chemical reaction,
pressure and/or temperature) and/or mechanical
strengthening methods (sewing, needling).
The two-dimensional (quasi two-dimensional) textile
structure having a weight per unit area of 100-
5000 g/m2, preferably 500-2300 g/m2, can be obtained by
a method according to one or more of the preceding
claims.
The weight per unit area is preferably locally adapted
by reducing or increasing the amount of fibre in the
two-dimensional (quasi-two-dimensional) fibre structure
or by a separate process step.
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The three-dimensional semi-finished fibre product can
be infiltrated and cured with thermosetting and/or
thermoplastic resins.
Fibre scrims having very advantageous properties can be
obtained, for example, if at least one fibre layer, in
particular a unidirectional layer, preferably all the
fibre 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
fibre 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).
Fibre scrims having advantageous material properties
and comparatively low manufacturing costs can further
be obtained if one or more fibre layers, in particular
unidirectional layers are used, which comprises polymer
fibres, in particular organic polymer fibres, or
mixtures thereof. In some applications, it can also
prove advantageous to use polyacrylonitrile-based
fibres, viscose-based fibres, to produce at least one
fibre layer. One, two, three or more of the fibre
layers can, for example, consist completely or of at
least 80 wt.. of polyacrylonitrile fibres and/or
viscose fibres relative to the total weight of fibres
in the fibre layer.
Fibre scrims having different material properties can
be obtained by producing fibre scrims comprising two,
three, four, five, six, seven, eight or arbitrarily
more fibre 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
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below this unidirectional layer. Preferably all the
unidirectional layers in a fibre 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 300, preferably at least 45 , preferably at
least 60 , in particular 85-900 to the longitudinal
direction of at least one following unidirectional
layer.
If the unidirectional layers each have different
longitudinal directions from one another, biaxial fibre
scrims are obtained when using two unidirectional
layers, triaxial fibre scrims are obtained when using
three unidirectional layers, quadraxial fibre scrims
are obtained when using four unidirectional layers.
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 00 direction, where the magnitude of the
angles can be the same (and the angles can, for
example, be +60 /-60 or +45 /-45 ) or different or
their respective longitudinal directions to the 00
direction are at angles of 0 and 90 .
Preferably a 0/90 scrim is produced on a scrim machine,
in which at least 900 of the fibres, particularly
preferably 95% of the fibres are disposed in the 0
direction. The width and the fibre weight per unit area
of the scrim according to the invention is determined
by the fibre titre used, the layer structure provided,
the resulting number of layers and their width.
It is a surprising advantage of the method according to
the invention that the total width of a, for example,
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fast-running scrim machine can be used. This is, for
example also a particular advantage compared with
ribbon looms.
Resins which are particularly suitable for impregnating
fibre 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.
In addition, inorganic impregnating agents can be used
for impregnating the fibre scrim, where, for example,
liquid silicon, SiC precursor polymers, in particular
silazanes, SiC precursor oligomers and mixtures thereof
are particularly suitable for impregnating the fibre
scrim.
The term "SiC precursor polymer" as used within the
framework of the present invention 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
to 99 wt. 0-6 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.o 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 C in
an inert atmosphere.
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When impregnating fibre 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.
The terms polysilazanes, polycarbosilazanes,
polysilanes, polyborocarbosilazanes, methyl-
polysiloxanes, polycarbosilanes, polyborosilazanes,
poly(dialkyl)silicones, polysiloxanes, etc. comprise
any polymer coming under the term that has a molecular
weight of more than about 300 g/mol.
A fibre scrim can additionally be impregnated with
inorganic impregnating agents and also with resins,
preferably synthetic resins. For example, neighbouring
sections of a fibre scrim can be impregnated with one
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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.
The curing of the impregnated fibre scrim can take
place in a curing temperature range of at least 40 C,
at a curing temperature in the range of 50 to 260 C,
preferably 80 to 200 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 fibre 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.
The content of resin and/or inorganic impregnating
agents, relative to the total weight of the non-
impregnated fibre scrim, can lie in a range of 5 to
85 wt.., preferably of 25 to 65 wt.o, particularly
preferably of 30 to 45 wt.o.
The fibre scrim can, for example, be impregnated as far
as saturation of the fibre scrim. In particular, liquid
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resins or molten resins ("hot melt resin") can be used,
which can for example comprise phenol resins.
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 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 fibre scrim, for example, a
carbon fibre 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
fibre scrim and fixes their position in the woven
fabric. Depending on the application of the composite
material, the fibre 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 fibres,
completely or in sections and/or it can be free of
resin in sections. The cured binder additionally
effects a mechanical reinforcement of the fibre scrim.
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After the curing and/or pressing, a fibre-scrim-
reinforced composite material or a fibre-scrim-
reinforced composite material product can be obtained.
A fibre-scrim-reinforced composite material product
within the framework of the present application
designates a partially or preferably completely cured
fibre-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 fibre-
scrim-reinforced composite material is also designated
as green body.
Optionally, the partially or completely cured fibre-
scrim-reinforced composite material, even without an
interposed step of obtaining, or the partially or
completely cured fibre-scrim-reinforced composite
material product can undergo further process steps such
as, inter alia, a thermal treatment, for example, for
carbonising or graphitising or an extensive heating
and/or pressing.
A thermal treatment can be carried out in a first
temperature range (frequently also designated as
"carbonisation") 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 oxidising
media, especially oxygen, at a temperature or in a
temperature range from about 800 C to about 1250 C,
preferably from 850 C to 950 C, in particular from
880 C to 920 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
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hours. Any method known to the person skilled in the
art can be used for the thermal treatment in a first
temperature range ("carbonisation") 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 C at
a maximum of 4 C per hour or coking is carried out
under pressure. The final temperature in this process
step cannot exceed, for example, 1250 C.
Both a completely and also an only partially cured
fibre-scrim-reinforced composite material can be
subjected to the thermal treatment in a first
temperature range.
After the thermal treatment in the first temperature
range, a composite material is obtained whose matrix
comprises carbon and is reinforced with a carbon fibre
woven fabric ("carbon fibre reinforced carbon", CFC).
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 "graphitisation"). The thermal
treatment in a second temperature range
("graphitisation") 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 C to 3000 C, preferably from 1800 C to 2200 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.
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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 characterised by a high
temperature resistance.
After the thermal treatment of the fibre-scrim-
reinforced composite material or composite material
product, a thermally treatment fibre-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 fibre-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 carbonisable
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
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vacuum pressure method can be used, for example, for
the impregnation.
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.
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 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 carbonisation step, cracks and pores still
present in the first shell should be closed. Depending
on the intended protective effect for the fibres, this
impregnation and after-burning process can take place
several times, preferably once to three times.
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
carbonisation can take place is followed by a thermal
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treatment in a second temperature range in an inert
atmosphere in which graphitisation takes place.
However, the execution of such a measure is merely
optional. Usually the end temperature of 30000C, in
particular 2400 C, is not exceeded during
graphitisation. It is preferable to work at
temperatures from 1800 to 2200 C. All known
graphitisation processes can be used for this step.
The post-compaction described hereinbefore which
comprises firstly an impregnation and then a burning
process can be repeated once or several times.
The number of post-compactions to be carried out is
dependent on the desired target density of the carbon
fibre-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/cm3, preferably of 1.30-1.55 g/cm3 can be
achieved.
Furthermore, the composite material comprising fibre-
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 vapour
deposition) or by the CVI method (CVI = chemical vapour
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 Al or in the publication E.
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Fitzer et. al., Chemie-Ingenieur-Technik 57, No. 9, p.
737-746 (1985)
In addition, the composite material comprising fibre-
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).
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 C to 2200 C, preferably in the
temperature range from 1650 C to 1750 C in an inert
atmosphere. In particular it is possible to work in the
temperature range from 1650 C to 1750 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.
In the case of siliconization without using vacuum,
siliconization can be carried out in particular at
temperatures from 2100 C to 2200 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.
Advantageously the previously described siliconizations
can be carried out using the so-called wick technique.
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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.
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.
Composite materials having particularly high quality
can be obtained, for example, if, following the step of
curing and optionally pressing the impregnated fibre
scrim and a thermal treatment in a first temperature
range in which carbonisation 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.
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.
The three-dimensional semi-finished fibre 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
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as a result of the low weight, the high flexibility and
loading capacity.
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 fibre product close to the final contour.
