U.S. patent application number 13/834072 was filed with the patent office on 2013-09-05 for methods of rtm molding.
This patent application is currently assigned to Mitsubishi Heavy Industries, Ltd.. The applicant listed for this patent is MITSUBISHI HEAVY INDUSTRIES, LTD., TORAY INDUSTRIES, INC.. Invention is credited to Kazuaki Kitaoka, Shigeru Nishiyama, Hiroshi Odani, Toshihide Sekido, Masahiko Shimizu.
Application Number | 20130228956 13/834072 |
Document ID | / |
Family ID | 32097011 |
Filed Date | 2013-09-05 |
United States Patent
Application |
20130228956 |
Kind Code |
A1 |
Sekido; Toshihide ; et
al. |
September 5, 2013 |
METHODS OF RTM MOLDING
Abstract
A method of RTM molding including placing a reinforcing fiber
substrate in a mold, placing a resin distribution medium having a
resin flow resistance lower than a resin flow resistance of said
reinforcing fiber substrate on a surface of said reinforcing fiber
substrate opposite said mold, providing a degasification medium
comprising a gas permeation film and a gas permeable substrate
between said reinforcing fiber substrate and said mold, and
injecting a resin into said mold through said resin distribution
medium after pressure in said mold is reduced by evacuation,
whereby the injected resin is impregnated into said reinforcing
fiber substrate by evacuating said resin injected from a
degasification space formed between said gas permeation film and
said mold.
Inventors: |
Sekido; Toshihide; (Otsu,
JP) ; Kitaoka; Kazuaki; (Ehime, JP) ; Odani;
Hiroshi; (Ehime, JP) ; Nishiyama; Shigeru;
(Nagoya, JP) ; Shimizu; Masahiko; (Nagoya,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TORAY INDUSTRIES, INC.
MITSUBISHI HEAVY INDUSTRIES, LTD. |
Tokyo
Tokyo |
|
JP
JP |
|
|
Assignee: |
Mitsubishi Heavy Industries,
Ltd.
Tokyo
JP
Toray Industries, Inc.
Tokyo
JP
|
Family ID: |
32097011 |
Appl. No.: |
13/834072 |
Filed: |
March 15, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10530263 |
Jun 6, 2005 |
8420002 |
|
|
PCT/JP2003/012947 |
Oct 9, 2003 |
|
|
|
13834072 |
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Current U.S.
Class: |
264/511 |
Current CPC
Class: |
B29C 70/547 20130101;
B29C 70/548 20130101; B29C 45/0005 20130101; B29C 70/443 20130101;
B29C 70/68 20130101 |
Class at
Publication: |
264/511 |
International
Class: |
B29C 45/00 20060101
B29C045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 9, 2002 |
JP |
2002-295932 |
Oct 9, 2002 |
JP |
2002-295933 |
Oct 9, 2002 |
JP |
2002-295934 |
Oct 28, 2002 |
JP |
2002-312454 |
Claims
1. A method of RTM molding comprising: placing a reinforcing fiber
substrate in a mold, placing a resin distribution medium having a
resin flow resistance lower than a resin flow resistance of said
reinforcing fiber substrate on a surface of said reinforcing fiber
substrate opposite said mold, providing a degasification medium
comprising a gas permeation film and a gas permeable substrate
between said reinforcing fiber substrate and said mold, and
injecting a resin into said mold through said resin distribution
medium after pressure in said mold is reduced by evacuation,
whereby the injected resin is impregnated into said reinforcing
fiber substrate by evacuating said resin injected from a
degasification space formed between said gas permeation film and
said mold.
2. The method according to claim 1, wherein said reinforcing fiber
substrate comprises a laminate of reinforcing fiber materials.
3. The method according to claim 1, wherein said gas permeation
film has a releasability capable of being delaminated from a molded
product after molding.
4. The method according to claim 1, wherein at least two resin
injection gates are disposed above said resin distribution medium,
and resin injection is carried out simultaneously from at least two
resin injection gates adjacent to each other, or from all resin
injection gates.
5. The method according claim 1, wherein at least one evacuation
route is provided in said mold in addition to an evacuation route
from said degasification space formed between said gas permeation
film and said mold.
6. The method according to claim 2, wherein said gas permeation
film has a releasability capable of being delaminated from a molded
product after molding.
7. The method according to claim 2, wherein at least two resin
injection gates are disposed above said resin distribution medium,
and resin injection is carried out simultaneously from at least two
resin injection gates adjacent to each other, or from all resin
injection gates.
8. The method according to claim 3, wherein at least two resin
injection gates are disposed above said resin distribution medium,
and resin injection is carried out simultaneously from at least two
resin injection gates adjacent to each other, or from all resin
injection gates.
9. The method according claim 2, wherein at least one evacuation
route is provided in said mold in addition to an evacuation route
from said degasification space formed between said gas permeation
film and said mold.
10. The method according claim 3, wherein at least one evacuation
route is provided in said mold in addition to an evacuation route
from said degasification space formed between said gas permeation
film and said mold.
11. The method according claim 4, wherein at least one evacuation
route is provided in said mold in addition to an evacuation route
from said degasification space formed between said gas permeation
film and said mold.
Description
RELATED APPLICATIONS
[0001] This is a divisional application of U.S. application Ser.
No. 10/530,263 filed Apr. 5, 2005, which is a .sctn.371 of
International Application No. PCT/JP2003/012947, with an
international filing date of Oct. 9, 2003 (WO 2004/033176 A1,
published Apr. 22, 2004), which is based on Japanese Patent
Application Nos. 2002-295932, filed Oct. 9, 2002, 2002-295933,
filed Oct. 9, 2002, 2002-295934, filed Oct. 9, 2002, and
2002-312454, filed Oct. 28, 2002, the subject matter of which is
incorporated by reference.
TECHNICAL FIELD
[0002] This disclosure relates to improvement of a method of Resin
Transfer Molding (hereinafter, referred to as "RTM") for molding a
structural material of a fiber reinforced plastic (hereinafter,
referred to as "FRP"), and specifically, to a method of RTM molding
in which it is possible to mold a thick material and, further, it
is possible to improve a quality of surface property or to increase
a fiber volume content (hereinafter, also referred to as "Vf") of
an FRP molded material to be molded. Although the title refers to
"methods of RTM molding" the methods include both a molding method
for RTM itself and a method of producing an FRP molded material
using the molding method.
BACKGROUND
[0003] Although FRP has been used in various fields, as a method of
producing an FRP structural material, general is a so-called
"prepreg/autoclave molding" method wherein, after a preform having
a shape of a structural material to be molded is formed beforehand
by prepregs, the preform is cured in an autoclave set at a
predetermined condition in temperature and pressure. However,
recently a method of RTM molding reduces production costs, and that
method is developed gradually. Many methods are proposed as RTM
molding methods of producing panels and beam materials which are
structural members for airplanes or architecture requiring high
strength, lightweight and low cost or of producing FRP molded
products such as outer panels of vehicles. For example, there are a
methods of RTM molding for molding a large FRP structural material
(for example, JP-A 12-145042) and a method of RTM molding using a
resin distribution medium (for example, U.S. Pat. No.
5,052,906).
[0004] In the method of RTM molding disclosed in JP-A 12-145042,
peel plys/resin distribution media are disposed on both surfaces of
a reinforcing fiber substrate comprising a laminate of reinforcing
fiber materials, the whole thereof is covered with a bag material,
and a resin injection gate and an evacuation gate for reducing a
pressure are provided relative to the inside covered with the bag
material. In this state, under a condition of a room temperature or
a heated atmosphere, a resin is injected from the resin injection
gate while being reduced in pressure by evacuating the inside of
the bag material through the evacuation gate. The resin flows from
the upper surface side to the lower surface side of the reinforcing
fiber substrate or from the lower surface side to the upper surface
side to impregnate the resin into the reinforcing fiber substrate.
After completion of impregnation, the resin is cured at room
temperature or under a heated atmosphere condition and, after
curing, the molded product is taken out from the mold by removing
the bag material.
[0005] As the problem in the above-described molding method,
although resin distribution media are disposed on both surfaces of
the reinforcing fiber substrate, because the resin impregnation is
basically carried out from one surface side relative to the
reinforcing fiber substrate, there is a limit in the distance
capable of being impregnated in the thickness direction of the
substrate. Therefore, if the reinforcing fiber substrate is too
thick, a predetermined impregnation becomes impossible.
[0006] It is known that permeability of resin into the reinforcing
fiber substrate can be determined generally by the following
equation.
I=(.epsilon./(1-.epsilon.)) (.alpha.P/2).times..intg.[dt
(.mu.(t)t)] [0007] I: permeability, s: resistance of substrate, a:
constant, [0008] P: vacuum pressure in substrate, .mu.(t):
viscosity, [0009] t: expiration time
[0010] Permeability corresponds to a distance (thickness) of resin
impregnation into the substrate.
[0011] With respect to resin impregnation into a reinforcing fiber
substrate, although the constant and viscosity in the
above-described equation are different depending on the kinds of
the substrate and the resin, because the impregnation distance is
astringent accompanying with expiration of time and, further, there
occurs an increase of the viscosity and the resin gradually becomes
a gel, a limit is generated in the distance in which the resin can
impregnate and, if the thickness of the reinforcing fiber substrate
is a certain thickness or more, it becomes impossible to impregnate
the resin any longer in the above-described conventional
method.
[0012] To impregnate the resin into a thick reinforcing fiber
substrate, it is considered to impregnate the resin into the
reinforcing fiber substrate from both the resin distribution media
on both surfaces of the reinforcing fiber substrate. In the
above-described molding method, however, because the resin
distribution media having substantially the same shape and property
are disposed on both surfaces, when merely the resin is impregnated
from both surface sides, the resin is impregnated in the thickness
direction of the substrate simultaneously and, in a same manner,
voids are hard to be pushed out in the side directions, and the
voids are likely to be enclosed in the substrate. If the voids are
enclosed, it is difficult to obtain a target property of a molded
product. To avoid such an enclosure of voids, the resin
impregnation is carried out basically from one surface side.
[0013] Further, as another problem on the above-described molding
method, it is difficult to obtain good flatness on the design
surface of the molded product. Namely, the above-described resin
distribution medium is formed as a member having a relatively large
surface irregularity with a low resistance for gas permeation to
increase the resin distribution property. However, if the resin
distribution media having such a relatively large surface
irregularity are disposed on both surfaces of the reinforcing fiber
substrate and the molding is carried out in this condition, the
relatively large surface irregularity of the resin distribution
medium is reflected to the design surface which is one surface of
the molded product. As a result, the designability is damaged and
an irregularity is formed on the surface of the molded product.
Therefore, there is a problem that the properties such as
aerodynamic property decrease.
[0014] To solve such problems, it is considered to use a resin
distribution medium having a small surface irregularity, but if
done so, the resistance for gas permeation becomes too great and, a
target resin distribution property cannot be obtained. Further,
because gas permeation from the reinforcing fiber substrate at the
time of evacuation also deteriorates, the vacuum degree does not
increase and it becomes difficult to completely impregnate the
resin in the thickness direction particularly for a thick
substrate.
[0015] Thus, although the degree of the irregularity of the resin
distribution medium affects the resin distribution and gas
permeation performances, the irregularity of the resin distribution
medium for improving resin distribution and gas permeation
performances (a relatively large irregularity) and the irregularity
of the resin distribution medium for improving the surface property
of the molded product (a relatively small irregularity) are in a
relationship opposite to each other. Therefore, in a conventional
method wherein substantially the same resin distribution media are
disposed on both surfaces of a reinforcing fiber substrate, it is
difficult to achieve both an increase in the resin impregnation
property and improvement of the surface property of a molded
product and it becomes particularly difficult in the molding using
a thick reinforcing fiber substrate.
[0016] To improve quality on the surface property of a molded
product, a condition is frequently employed wherein a gas permeable
material is not disposed on a tool surface side. In such a case,
however, because the gas permeation in the substrate deteriorates
and the vacuum degree does not increase, reduction in impregnation
may occur.
[0017] In the method of RTM molding disclosed in U.S. Pat. No.
5,052,906, a reinforcing fiber substrate is placed on a mold and a
resin distribution medium is disposed at a position opposite the
mold, a resin injection port and an evacuation port are disposed,
they are covered with a bag material from the upper side, and a
matrix resin is injected where the inside of a cavity is reduced in
pressure by evacuation. The flowing-in route of the resin into the
substrate is formed as a route in which the resin is distributed
mainly from the injection port along the surface direction of the
substrate disposed in the mold and the distributed resin is
impregnated in the thickness direction of the substrate.
[0018] In the above-described method, when the resin injection is
carried out at a so-called "high Vf" condition where the fiber
volume content (Vf) of the reinforcing fiber substrate is 55% or
more, namely, at a condition where a gap between reinforcing fibers
is small, although the fiber volume content of a final molded
product itself becomes high, the impregnation property of the resin
into the molded product is poor. Therefore, in the case of a thick
molded product having a plate thickness of, for example, 25 mm or
more, the resin does not reach the corners of the molded product
and only a product having a defect due to a resin non-impregnated
portion is produced as a structural material.
[0019] On the other hand, in the case where the Vf of the
reinforcing fibers is, for example, 45% and the gap between
reinforcing fibers is relatively great, because the fiber volume
content of the final molded product becomes low although a good
resin impregnation property can be obtained, only a product having
poor strength and lightweight property can be obtained. Namely, the
resin impregnation property and the fiber volume content Vf are in
a relationship opposite each other and it is difficult to achieve
both improvement of the resin impregnation property and increase
the fiber volume content together. Moreover, although it is
preferred depending on a molded product to control the fiber volume
content from the necessity of stabilization of the quality, it is
also difficult to satisfy such a requirement.
[0020] Further, although usually the reinforcing fiber substrate is
formed as a laminate of a plurality of reinforcing fiber materials
to obtain an FRP molded product with a predetermined thickness, as
to the thickness direction, that is, as to the direction
perpendicular to the lamination surface in the reinforcing fiber
material laminate, the resistance against the resin flow is
generally high and there is a limit in the reaching distance of the
resin being impregnated in the thickness direction of the
substrate. Therefore, in a case where it is required to increase
the number of lamination of the reinforcing fiber materials such as
a case of planning to mold a high-strength product, it may be
difficult to completely impregnate the resin into the corners of
the reinforcing fiber material laminate and, consequently, an FRP
structural material having a certain thickness or more
substantially cannot be molded.
[0021] Accordingly, there is a need to provide a method of RTM
molding (method of producing an FRP) which can mold even a thick
FRP structural material with a good resin impregnation property,
and which can realize improvement of the surface quality, increase
of the lightweight property and achievement of an excellent
strength.
SUMMARY
[0022] We provide a method of RTM molding wherein a reinforcing
fiber substrate is placed in a mold, resin distribution media each
exhibiting a resin flow resistance lower than a resin flow
resistance of the reinforcing fiber substrate are placed on both
surfaces of the reinforcing fiber substrate and, after a pressure
in the mold is reduced by evacuation, a resin is injected into the
mold through the resin distribution media to impregnate the
reinforcing fiber substrate with the resin injected, is
characterized in that a resin flow resistance of a first resin
distribution medium placed on a first surface of the reinforcing
fiber substrate is set lower than a resin flow resistance of a
second resin distribution medium placed on a second surface of the
reinforcing fiber substrate, and the evacuation is carried out
through the second resin distribution medium while the resin is
injected into the first resin distribution medium to impregnate the
reinforcing fiber substrate with the resin injected (a first
method) is provided.
[0023] Namely, in our method of RTM molding, an intentional
large/small relationship is given to the resin flow resistances of
the resin distribution media placed on both surfaces of the
reinforcing fiber substrate. In practice, the resin flow resistance
can be determined by measuring a gas permeation resistance and
determining it as a value corresponding to the measured gas
permeation resistance. Alternatively, because the permeability
generally shown by the following equation has the same meaning as
that of the resin flow resistance, such a value may be
employed.
L (2.beta.PK.times..intg.[dt (.mu.(t)t)] [0024] L: impregnation
distance (m) [0025] K: permeability (m.sup.2) [0026] .beta.:
constant [0027] P: vacuum pressure in substrate (kg/m.sup.2) [0028]
.mu.(t): viscosity (kgs/m.sup.2) [0029] t: expiration time
[0030] Although the reinforcing fiber substrate may be a single
layer or may be formed as a laminate of a plurality of reinforcing
fiber materials, because our methods of RTM molding are suitable
particularly for molding a thick product, namely, molding to
impregnate a resin into a thick reinforcing fiber substrate, our
target is mainly where a reinforcing fiber substrate comprising a
laminate of a plurality of reinforcing fiber materials is used.
[0031] In this method of RTM molding, it is preferred that the
resin flow resistance of the above-described second resin
distribution medium is set lower than the resin flow resistance of
the above-described reinforcing fiber substrate. By this, because
the resin flow resistance (gas permeation resistance) of the second
resin distribution medium is suppressed sufficiently low as
compared with the resin flow resistance (gas permeation resistance)
of the reinforcing fiber substrate although the resin flow
resistance (gas permeation resistance) of the second resin
distribution medium is higher than the resin flow resistance (gas
permeation resistance) of the first resin distribution medium,
reduction of the vacuum degree in the substrate due to
deterioration of gas permeation from the reinforcing fiber
substrate is suppressed and damage to the resin impregnation into a
thick reinforcing fiber substrate can be avoided.
[0032] Further, it is preferred that the resin flow resistance of
the above-described first resin distribution medium is set at 1/3
of the resin flow resistance of the reinforcing fiber substrate or
less because the resin can be distributed into the medium quickly.
Further, more preferably, it is set at 1/10 or less to distribute
the resin more quickly. By this, the distribution property of the
resin injected into the first resin distribution medium in the
surface direction of the reinforcing fiber substrate is ensured to
be sufficiently high, the resin injected into the first resin
distribution medium is quickly impregnated in the thickness
direction of the reinforcing fiber substrate while the resin is
distributed quickly in a direction along the surface. Under such a
condition where the resin flow resistance of the first resin
distribution medium and the resin flow resistance of the second
resin distribution medium are satisfied, the large/small
relationship is given to the resin flow resistance of the first
resin distribution medium and the resin flow resistance of the
second resin distribution medium.
[0033] Further, in our methods of RTM molding, it is preferred that
a peel ply capable of being removed together with a resin
distribution medium after molding is interposed between at least
one resin distribution medium and the reinforcing fiber substrate.
By this, the resin distribution medium can be easily delaminated.
However, after releasing the molded product from the mold, at least
one resin distribution medium may be left in the molded product
without delaminating it from the molded product. In this case, the
peel ply is not necessary for the side where the resin distribution
medium is left.
[0034] Further, in our methods of RTM molding, a method may be
employed wherein a porous sheet is interposed between at least one
resin distribution medium and the reinforcing fiber substrate. This
porous sheet has a function different from that of the
above-described peel ply, and it is a sheet that suppresses
transfer of the irregularity of the resin distribution medium to
the reinforcing fiber substrate side while maintaining the resin
distribution function of the resin distribution medium. Therefore,
the sheet is preferably disposed on the design surface side of the
molded product.
[0035] Further, in our methods of RTM molding, at least one resin
distribution medium may be formed by providing a groove as a resin
flow path on an inner surface of the mold. In this case, even if a
separate resin distribution medium is not made, it is possible to
use the inner surface of the mold itself as a resin distribution
medium.
[0036] Further, in our method of RTM molding, it is preferred that
injection of a resin is started also through the second resin
distribution medium before the above-described resin reaches the
above-described second surface. Namely, from this time, the resin
impregnation from both surfaces is substantially started.
[0037] Further, in our methods of RTM molding, a method can be
employed wherein, in the case where at least two resin injection
gates are disposed above the first resin distribution medium, the
resin injection is carried out simultaneously from at least two
resin injection gates adjacent to each other, or from all resin
injection gates. Since evacuation through the second resin
distribution medium as well as the resin injection are carried out
simultaneously while the quick resin impregnation is achieved,
generation of resin non-impregnation portions can be prevented.
[0038] Further, our methods of RTM molding from the viewpoint of
molding provide a particularly excellent design surface. Namely,
our method of RTM molding is characterized in that a reinforcing
fiber substrate is placed in a mold, a resin distribution medium
exhibiting a resin flow resistance lower than a resin flow
resistance of the reinforcing fiber substrate is placed on a
surface of the reinforcing fiber substrate opposite the mold, a
degasification medium comprising a gas permeation film and a gas
permeable substrate is provided between the reinforcing fiber
substrate and the mold, a resin is injected into the mold through
the resin distribution medium after pressure in the mold is reduced
by evacuation and the resin injected is impregnated into the
reinforcing fiber substrate by evacuating the resin injected from a
degasification space formed between the gas permeation film and the
mold (a second method).
[0039] In this second method, the above-described reinforcing fiber
substrate comprises, for example, a laminate of reinforcing fiber
materials.
[0040] Further, in the above-described second method, it is
preferred that the above-described gas permeation film has a
releasability capable of being delaminated from a molded product
after molding.
[0041] Further, in the above-described second method, particularly
in the case where a product with a wide area is molded, it is
preferred that at least two resin injection gates are disposed
above the resin distribution medium, and resin injection is carried
out simultaneously from at least two resin injection gates adjacent
to each other, or from all resin injection gates.
[0042] Furthermore, in the above-described second method,
particularly in a case where a product with a wide area is molded,
it is also preferred that at least one evacuation route is provided
in the mold in addition to an evacuation route from the
degasification space formed between the gas permeation film and the
mold.
[0043] In the above-described method of RTM molding (the first
method), the resin is injected into the first resin distribution
medium having a lower resin flow resistance, and the injected resin
is quickly impregnated into the reinforcing fiber substrate in the
thickness direction while the resin is distributed quickly and
broadly in a direction along the first surface of the reinforcing
fiber substrate. Then, basically the inside of the mold is reduced
in pressure by evacuation via the second resin distribution medium
having a higher resin flow resistance, and the above-described
injected resin is impregnated into the reinforcing fiber substrate
having an evacuated and pressure-reduced condition. At that time,
since the resin flow resistance (gas permeation resistance) of the
second resin distribution medium is suppressed sufficiently low as
compared to the resin flow resistance (gas permeation resistance)
of the reinforcing fiber substrate although it is higher than the
resin flow resistance (gas permeation resistance) of the first
resin distribution medium, it is suppressed to reduce the vacuum
degree in the substrate by deterioration of gas permeation from the
reinforcing fiber substrate. Quick resin impregnation can thus be
ensured. Therefore, even for a thick reinforcing fiber substrate, a
sufficiently good resin impregnation can be ensured. Since the
resin flow resistance (gas permeation resistance) of the second
resin distribution medium is set higher than that of the first
resin distribution medium, the second resin distribution medium can
be formed as a medium with a small irregularity as compared to the
first resin distribution medium and, even if a transfer of the
surface form of this second resin distribution medium to the
surface of a molded product occurs, the degree of the irregularity
on the surface of the molded product ascribed to the transfer can
be suppressed. Therefore, by setting this surface side to be a
design surface side, a desirable design surface of the molded
product having a small irregularity can be obtained.
[0044] In a molding requiring resin impregnation into a further
thick reinforcing fiber substrate, in particular, in the case where
it is difficult to impregnate the resin sufficiently up to the
surface at the second resin distribution medium side of the
reinforcing fiber substrate only by the above-described resin
impregnation from the first resin distribution medium side into the
reinforcing fiber substrate (in the case exceeding the conventional
resin impregnation limit), before the resin impregnated from the
first resin distribution medium side into the reinforcing fiber
substrate reaches the second surface of the reinforcing fiber
substrate, the resin injection through the second resin
distribution medium can be started. By this resin injection from
the second resin distribution medium side, the resin impregnation
can be supplemented for a portion in which the resin is hardly
impregnated into the reinforcing fiber substrate sufficiently, that
is, for a portion of the second surface side, and it becomes
possible to impregnate the resin sufficiently over the entire
region of the reinforcing fiber substrate in the thickness
direction. Namely, in this process, the resin impregnation in the
thickness direction of the reinforcing fiber substrate is carried
out mainly by impregnation from the first resin distribution medium
side, and a lack of impregnation is supplemented by impregnation
from the second resin distribution medium side. Further, because a
large/small relationship is given between the gas permeation
resistances (resin flow resistances) of the first and second resin
distribution media, while a quick resin impregnation is carried out
from the first resin distribution medium side, in the second resin
distribution medium side, the resin impregnation is supplemented,
and voids pushed out from the first resin distribution medium side
by the impregnated resin are pushed out at a relatively slow speed
toward side portions, that is, in a direction along the second
surface of the reinforcing fiber substrate, without being enclosed
in the reinforcing fiber substrate by the resin impregnated from
the second resin distribution medium side. As a result, in spite of
resin impregnation from both surface sides, it can be avoided to
enclose voids in the reinforcing fiber substrate and, besides, the
resin impregnation at the second surface side is supplemented and,
therefore, it becomes possible to well mold a thick material
without the problem of accompanying void enclosures. Moreover, in
this case, by setting the second resin distribution medium side to
be a design surface as described above, an excellent design surface
with small irregularity can be obtained at the same time. Namely,
molding of a thick material and improvement of the surface quality
can be both achieved.
[0045] Further, the aforementioned method of RTM molding (the
second method) is effective for the following cases. Namely, in the
case where a flatness of a molded surface (a design surface) at the
mold side is further required, and in a molding where a resin
impregnation into a thick and broad-area reinforcing fiber
substrate is required, in particular, a degasification medium
comprising a gas permeation film and a gas permeable substrate can
be provided between the reinforcing fiber substrate and the surface
of the mold as means for always effectively operating the
degasification route from any portion of the mold surface. By this,
at the time of resin injection, even if there is a difference in
time for the resin to reach the lower surface side (design surface
forming side) of the reinforcing fiber substrate and a portion late
in impregnation is liable to occur, by evacuation from the
degasification formed between the gas permeation film and the mold,
finally it becomes possible to completely impregnate the resin over
the entire surface. Consequently, a design surface along the mold
surface and good in flatness can be obtained,
[0046] Further, in the case where the resin is injected
simultaneously from at least adjacent resin injection gates or from
all resin injection gates, although usually there occur regions in
which resin flows overlap and in which evacuation is hard and
non-impregnated portions are frequently generated, in the
above-described method, because a degasification route is always
ensured, finally it becomes possible to completely impregnate the
resin over the entire surface.
[0047] Further, the gas permeation film, for example, preferably
has fine holes on the surface and forms a flat surface. If such a
film is employed, together with using a thin and small-irregularity
substrate as the above-mentioned gas permeable substrate, the
surface quality of a molded product can be improved.
[0048] Further, we also provide the following method of RTM molding
from the viewpoint of high V.sub.f molding. Namely, the method of
RTM molding wherein a reinforcing fiber substrate is placed in a
mold, a resin injection line and an evacuation line each
communicating with an inside of the mold are provided, pressure in
the mold is reduced by evacuation and a resin is injected into the
mold and impregnated into the reinforcing fiber substrate to form
an FRP molded material, is characterized in that, after the resin
is impregnated into the reinforcing fiber substrate to achieve a
fiber volume content lower than a target fiber volume content of
the FRP molded material, injection of resin is stopped and,
thereafter, evacuation of resin is continued until reaching the
target fiber volume content (a third method). Namely, when the
resin is cured after the resin flows over the entire area of the
substrate and impregnated, before the resin is cured, evacuation of
resin is continued until reaching the target fiber volume content
and excessive resin is evacuated from the inside of the reinforcing
fiber substrate, thereby realizing a method of RTM molding capable
of increasing the fiber volume content up to the target value.
[0049] In this method of RTM molding, a method can be employed
wherein, after injection of resin is stopped, at least one line of
resin injection lines is changed to an evacuation line, and
evacuation of resin is continued until reaching the target fiber
volume content.
[0050] The above-described target fiber volume content is
preferably, for example, in a range of 55 to 65% to achieve a high
Vf. In this case, in consideration of decreasing the amount of
waste resin to the extent possible and increasing the resin
impregnation property, the above-described fiber volume content
lower than the target fiber volume content is preferably, for
example, in a range of 45 to 60%. Furthermore, in the case where
the resin impregnation property is required to be further
increased, it is preferably in a range of 45 to 55%.
[0051] In this method of RTM molding, the above-described
reinforcing fiber substrate can be formed as a preform having a
fiber volume content, which is a rate of a volume of reinforcing
fibers relative to a bulk volume of the reinforcing fiber
substrate, lower than the target fiber volume content. In
particular, as the reinforcing fiber substrate, a woven fabric
preformed at an arbitrary fiber volume content within a range lower
than the target fiber volume content, or a laminate can be used.
The laminate may be formed by laminating layers of reinforcing
fibers by an arbitrary number and, a structure, where reinforcing
fiber layers are bonded to each other, is more preferable because a
stability is given to the fiber volume content.
[0052] In the above-described method of RTM molding, the
determination whether reaching the target fiber volume content or
not can be carried out, for example, by measurement of the
thickness of the reinforcing fiber substrate, and it may be
determined whether an excessive resin is evacuated and removed by a
predetermined amount or not by measuring this thickness during the
continuation of the resin evacuation.
[0053] Further, in the above-described method of RTM molding, it is
possible to preset the injection amount of the resin or the
evacuation amount. Namely, a method can be employed wherein an
injection amount of resin corresponding to the fiber volume content
lower than the target fiber volume content is preset, and the
injection of resin is stopped at the time reaching the injection
amount preset. Further, a method can be employed wherein an
evacuation amount to reach the target fiber volume content is
preset relative to an injection amount of resin, and the evacuation
of resin is stopped at the time reaching the evacuation amount
preset.
[0054] Further, in the above-described method of RTM molding, it is
preferred that at least one layer of the reinforcing fiber
substrate comprises a carbon fiber layer to obtain a high-strength
and lightweight FRP molded material. This carbon fiber layer can be
formed as a woven fabric, for example, a unidirectional woven
fabric in which carbon fibers are oriented unidirectionally.
[0055] In the above-described method of RTM molding (the third
method), because the resin is first impregnated into the
reinforcing fiber substrate so that the fiber volume content
becomes lower than the target fiber volume content of the FRP
molded material, the porosity is high, the resin is impregnated
sufficiently over the entire area of the reinforcing fiber
substrate and, at that time, generation of resin non-impregnated
portions can be prevented. After such resin impregnation, the resin
injection is stopped and, thereafter, by the time when the resin is
cured, evacuation of resin is continued until reaching the target
fiber volume content, and excessive resin is evacuated from the
inside of the reinforcing fiber substrate, thereby achieving a
target high Vf of the molded material.
[0056] Further, we also provide the following method of RTM molding
as another method. Namely, the method of RTM molding is
characterized in that a plurality of reinforcing fiber materials
are laminated in a mold to form a reinforcing fiber material
laminate and a resin is impregnated into the reinforcing fiber
material laminate by injecting a resin in a direction from an end
surface of the reinforcing fiber material laminate along a laminate
surface while reducing pressure in the mold by evacuation (a fourth
method). Namely, the resin is injected from the end surface of the
reinforcing fiber material laminate mainly into a portion between
layers of the reinforcing fiber materials and the resin injected is
impregnated into respective reinforcing fiber materials.
[0057] In this fourth method, the resin is injected from the end
surface of the reinforcing fiber material laminate in the direction
along the laminate surface, first, the resin is injected quickly
into a portion between the layers of the reinforcing fiber
materials forming the reinforcing fiber material laminate, which is
low in flow resistance and, thereafter, the resin is impregnated
from the portion between the layers in the thickness direction of
the respective reinforcing fiber materials, namely, in the
lamination direction of the reinforcing fiber materials and,
therefore, the matrix resin can be quickly injected and impregnated
over the entire reinforcing fiber material laminate. Therefore,
even if the molded material to be molded has a large thickness, the
limit in thickness such as a conventional limit does not exist and
the aforementioned problems can be solved. Namely, it is recognized
that the resin flow resistance in the direction parallel to the
surfaces of the reinforcing fiber materials is about 1/5- 1/10 of
the resin flow resistance in the direction perpendicular to the
surfaces of the reinforcing fiber materials, according to our
experiments, although it is different depending on the kinds of the
reinforcing fiber material and the resin, and the resin
distribution speed in the direction parallel to the surfaces of the
reinforcing fiber materials is very fast as compared to that in the
perpendicular direction. However, because there exist lower limits
in flow resistance of reinforcing fiber material and in resin
viscosity and there exists a limit in distance at which the resin
can progress between the layers, the molding condition is
considered that the distance required for the resin to progress
between the layers should be about 600 mm or less. Thus, by
impregnating the resin from the end surface of the reinforcing
fiber material laminate in the direction along the laminate surface
through the portions between layers, the restriction in thickness
of the reinforcing fiber material laminate substantially does not
exist and the molding can be well carried out up to a thick molded
material. Further, because basically it is not necessary to dispose
a resin distribution medium in this molding portion, the
irregularity of the resin distribution medium is not transferred,
the surface property can be improved and a great decrease in cost
can be achieved by saving the processes of preparing and removing
the resin distribution medium.
[0058] Further, in the above-described fourth method, if the gross
length of the reinforcing fiber material laminate (in the case
where there is a bend or/and a curve, it is a total length along
the shape) is 600 mm or less, it is possible to impregnate the
resin sufficiently into the respective reinforcing fiber materials
by the above-described resin injection from the above-described end
surface into the portions between layers. Namely, if this length is
more than 600 mm, the resin is hardly impregnated and there is a
fear that a resin non-impregnated portion is generated. In the case
where the length is 300 mm or less, the resin impregnation becomes
possible in a shorter time and such a condition is more
preferable.
[0059] Further, in the above-described fourth method, if the resin
viscosity at a temperature for liquid resin injection is maintained
in a range of 10 to 1500 mPas during a time from starting resin
impregnation to expiration of one hour, a resin impregnation in a
short period of time is possible. Namely, if the resin viscosity is
less than 10 mPas, because the resin viscosity is too low, although
the resin is quickly permeated in the portions between layers in
the direction along the laminate surface, particularly in a case
where the reinforcing fiber material is formed from a strand and
the like, because the resin impregnation from the portion around
the strand toward the inside of the strand progresses substantially
simultaneously, a resin non-impregnated portion is liable to occur
in the strand. On the other hand, if the resin viscosity is more
than 1500 mPas, because the resin viscosity is too high, the
distance for resin permeation in the portions between layers in the
direction along the laminate surface decreases and the resin is
hardly impregnated into the respective reinforcing fiber materials,
and a resin non-impregnated portion is liable to occur. Therefore,
it is preferred that the resin viscosity at the temperature of
liquid resin injection is maintained in a range of 10 to 1500 mPas
during the time from starting of the resin impregnation to
expiration of one hour,
[0060] The sectional shape of the reinforcing fiber material
laminate is not particularly restricted, and it may be a
rectangular, C-type, I-type, L-type, Z-type, T-type, J-type or hat
shape, other than a flat plate shape. Further, in the case of a
reinforcing panel formed from a skin material (a skin plate
material) and a stringer material (a beam material), the skin
material is frequently formed in a simple flat plate shape, but the
stringer material is frequently formed in a relatively complicated
shape, and in such a case, our methods are suitably applied
particularly to the part of forming the stringer material. For
example, in the case where the reinforcing fiber material laminate
comprises a part that forms a stringer material having a section of
a rectangular, C-type, I-type, L-type, Z-type, T-type, J-type or
hat shape, and a part that forms a skin material, our methods are
suitable particularly for molding of this part to form the stringer
material. Namely, after the resin is injected from the end surface
of the part to form the stringer material of the laminate mainly
into portions between layers of the respective reinforcing fiber
materials, the resin injected is impregnated into the entire part
to form the stringer material. These parts that form the stringer
material and parts that form the skin material may be molded
integrally. Because the resin is injected from the end surface of
the part that forms the stringer material, restriction in thickness
of the stringer material does not exist and, because it is not
necessary to dispose a resin distribution medium, an improvement of
surface property and a decrease in great cost due to saving of the
preparing operation and the removing operation of the resin
distribution medium, can be achieved. In this case, a method can be
employed wherein, for the part that forms the skin material, the
resin is impregnated in the thickness direction while being
distributed in the direction along the surface of the part that
forms the skin material via a resin distribution medium and a
reinforcing panel formed from the skin material and the stringer
material is molded integrally.
[0061] Furthermore, in the above-described fourth method, a method
can be employed wherein an upper mold provided with a resin
distribution medium or a resin flow path groove is further disposed
on the end surface of the reinforcing fiber material laminate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0062] FIG. 1 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0063] FIG. 2 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0064] FIG. 3 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0065] FIG. 4 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0066] FIG. 5 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0067] FIG. 6 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0068] FIG. 7 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0069] FIG. 8 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0070] FIG. 9 is a schematic vertical sectional view of one example
of a molding apparatus used for a method of RTM molding.
[0071] FIG. 10 is a schematic vertical sectional view of one
example of a molding apparatus used for a method of RTM
molding.
[0072] FIG. 11 is a schematic vertical sectional view of one
example of a molding apparatus used for a method of RTM
molding.
EXPLANATION OF SYMBOLS
[0073] 1: mold [0074] 2: breather [0075] 3, 3a, 3b: peel ply [0076]
4: reinforcing fiber substrate [0077] 4A, 4B, 4C, 4D: reinforcing
fiber material laminate [0078] 4a, 4b: end surface of laminate
[0079] 5, 5a, 5b: resin distribution medium [0080] 6, 6a, 6b, 6d,
6e, 6i, 6k, 6l: evacuation gate [0081] 6c, 6f, 6g, 6h, 6j, 6m, 6n,
6o: resin injection gate [0082] 7: sealant [0083] 8: bag material
[0084] 9, 41, 42, A1, A2, A3, A4, A5, B1, B2: valve [0085] 10:
matrix resin [0086] 11 vacuum pump [0087] 12: resin pot [0088] 13:
vacuum trap [0089] 14: shape fixing jig [0090] 20: porous sheet
[0091] 21: dial gauge [0092] 23: gas permeable material [0093] 30:
mold groove for resin distribution [0094] 50: gas permeation film
[0095] 51: gas permeable substrate [0096] 52: seal tape [0097] 53:
degasification port [0098] 54: degasification medium
DETAILED DESCRIPTION
[0099] Hereinafter, we will explain our methods referring to the
drawings.
[0100] FIG. 1 is a schematic vertical sectional view of a molding
apparatus used for a method of RTM molding. A mold 1 forming a base
is made, for example, from a stainless steel or an aluminum alloy,
or another metal for mold or an FRP and formed in, for example, a
flat-plate like shape. The shape of the mold 1 is processed
depending on the shape of a desired molded product and is not
particularly restricted.
[0101] In this example, a breather 2 is disposed on mold 1 as a
second resin distribution medium. The "breather" has a resin flow
resistance lower than a flow resistance of a resin flowing in a
reinforcing fiber substrate although its resin flow resistance is
not low as the flow resistance of the aforementioned conventional
resin distribution medium. The surface irregularity (surface
roughness) of breather 2 is preferably 1.3 times or less of the
surface irregularity (surface roughness) of the reinforcing fiber
substrate. As breather 2, concretely, a surface mat, a plain weave
woven fabric or a mesh woven fabric comprising glass fibers or
carbon fibers which are reinforcing fibers and having a low weight
(100 g/m.sup.2 or less), or a woven fabric or a knit fabric
comprising synthetic fibers and having a large denier (200 denier
or more), is preferred.
[0102] A peel ply 3a is placed on breather 2. Peel ply 3a is laid
to easily remove media and the like from a molded material, and as
peel ply 3a, for example, a woven fabric having a releasing
function such as a NYLON taffeta is used.
[0103] A reinforcing fiber substrate 4 is placed on peel ply 3a. In
this example, reinforcing fiber substrate 4 is formed as a laminate
of a plurality of reinforcing fiber materials, in particular, a
plurality of reinforcing fiber woven fabrics. Our method is
suitable particularly for the molding using such a thick
reinforcing fiber substrate 4 laminated with a plurality of
reinforcing fiber materials. However, even in the case where a
reinforcing fiber substrate comprising a single reinforcing fiber
material is used, of course, our method can be applied and, also in
such a case, our method is suitable particularly for the molding
using a thick reinforcing fiber substrate.
[0104] A first resin distribution medium 5 is placed on reinforcing
fiber substrate 4 via peel ply 3b. First resin distribution medium
5 has an irregularity on the surface and, in this example, the
medium has a resin flow resistance of 1/10 or less of the resin
flow resistance of reinforcing fiber substrate 4 (reinforcing fiber
material laminate). A large/small relationship in resin flow
resistance is given between first resin distribution medium 5 and
breather 2 as a second resin distribution medium, and the resin
flow resistance of breather 2 is set higher than the resin flow
resistance of first resin distribution medium 5. As first resin
distribution medium 5, concretely, a mesh woven fabric made of
polyethylene or polypropylene resin and having a mesh size of #400
or less is preferred. As the result of such a disposition, first
resin distribution medium 5 is disposed relative to the first
surface of reinforcing fiber substrate 4 and breather 2 as the
second resin distribution medium is disposed relative to the second
surface at the opposite side.
[0105] The whole of the materials thus disposed on mold 1 is
covered with a bag material 8. Although bag material 8 comprises a
gas-tight material for forming a pressure-reduced cavity, for this
bag material 8, in consideration of thermal resistance and the
like, for example, a NYLON film is preferably used. A resin
injection gate 6c is provided relative to first resin distribution
medium 5 in the inside covered with bag material 8, and evacuation
gates 6a, 6b to reduce the pressure of the inside by evacuation are
provided relative to breather 2 provided as the second resin
distribution medium. These gates 6a, 6b, 6c are formed, for
example, by using C channel materials made of aluminum and the
like, and these channel materials connect to external members via
plastic tubes. A sealant 7 made of a synthetic rubber with a high
adhesive property is interposed between the edge portion of bag
material 8 and mold 1 and, by sealing therebetween, flowing in of
air from outside is prevented to maintain a pressure-reduced
condition of the inside of bag material 8. A thermoplastic resin 10
prepared as an FRP matrix resin to be impregnated is stored in a
resin pot 12 made of a plastic, and by opening a valve 9 at an
appropriate timing, the resin is injected via resin injection gate
6c. The inside of the cavity covered with bag material 8 is
maintained at a pressure-reduced condition by a vacuum pump 11 via
evacuation gates 6a, 6b. By forming bag material 8 as a double bag
having a first bag material and a second bag material covering the
first bag material, an air leakage can be prevented and, as a
result, the fiber volume content (Vf) of reinforcing fibers can be
increased.
[0106] Further, even if bag material 8 is a single bag, the air
leakage can be prevented by disposing sealant 7 at the outer edge
portion as a parallel double disposition style and an effect
similar to that due to the double bag can be obtained. In this
case, the amount used for sub materials and the attachment time can
be reduced rather than those in the double bag system and has the
merit of performing the molding more inexpensively.
[0107] In the molding apparatus shown in FIG. 1, although ply
3b/resin distribution medium 5 are disposed on reinforcing fiber
substrate 4 and peel ply 3a/breather 2 are disposed under the
reinforcing fiber substrate 4 as in a conventional molding, it may
be carried out that, after molding without disposing peel ply 3a,
breather 2 is left in the molded material as it is.
[0108] The molding in this example is carried out as follows.
[0109] Under room temperature or a heated atmosphere, the laminate
having a structure shown in FIG. 1 is placed on mold 1 (a tool),
and the whole of the materials and members including resin
injection gate 6c disposed at the upper side and evacuation gates
6a, 6b disposed at the lower side is covered with bag material 8.
In this state, when the resin is injected from resin injection gate
6c while the inside of bag material 8 is reduced in pressure by the
evacuation through evacuation gates 6a, 6b, while matrix resin 10
is quickly distributed in first resin distribution medium 5 in a
direction along the upper surface of reinforcing fiber substrate 4,
the resin flows in a direction from the upper surface toward the
lower surface and is impregnated into the reinforcing fiber
substrate 4. After resin impregnation is finished, the resin is
cured under room temperature or a heated atmosphere and,
thereafter, bag material 8 is delaminated and the molded material
is released from the mold. Thereafter, peel plies 3a, 3b, resin
distribution medium 5 and breather 2 are released and removed from
the molded product. However, as one example, breather 2 may be left
in the molded product as it is.
[0110] In this molding, because the resin flow resistance of first
resin distribution medium 5 is set low, the resin injected into the
first resin distribution medium 5 is quickly impregnated into
reinforcing fiber substrate 4 in the thickness direction while the
resin is distributed in the direction along the first surface of
the reinforcing fiber substrate 4 quickly and sufficiently broadly.
Although the inside of bag material 8 is evacuated via breather 2
provided as the second resin distribution medium to reduce the
pressure in the bag material 8, because the resin flow resistance
(gas permeation resistance) of breather 2 is sufficiently
suppressed compared to the resin flow resistance (gas permeation
resistance) of reinforcing fiber substrate 4 although it is higher
than the resin flow resistance (gas permeation resistance) of first
resin distribution medium 5, the reduction of vacuum degree in the
substrate due to the deterioration of gas permeability from the
reinforcing fiber substrate can be suppressed and a quick resin
impregnation property can be ensured. Therefore, even for a thick
reinforcing fiber substrate 4, a sufficiently good resin
impregnation property from the side of first resin distribution
medium 5 can be ensured. Further, since the resin flow resistance
(gas permeation resistance) of breather 2 is set higher than that
of first resin distribution medium 5, the breather 2 can be formed
as a medium having a small irregularity as compared with the first
resin distribution medium 5. Therefore, even if the surface pattern
of such a breather 2 is transferred to the surface of a molded
product, the degree of irregularity of the surface of the molded
product due to the transfer can be suppressed. Namely, while a good
resin impregnation property can be ensured, the irregularity of the
surface of the molded product at the second resin distribution
medium side can be suppressed. By setting this surface side of the
molded product having a small irregularity at a design surface
side, a molded product having a desirable surface property can be
obtained. Namely, it is possible to extinguish the traces of the
medium which have been present in the tool surface side of the
molded product by curing of the resin in the conventional
method.
[0111] FIG. 2 is a schematic vertical sectional view of a molding
apparatus according to a second example of our method, and FIG. 2
shows an example wherein, instead of the breather, a resin
distribution medium 5a and a porous sheet 20 are disposed on one
surface of the reinforcing fiber substrate. FIG. 3 is a schematic
vertical sectional view of a molding apparatus according to a third
example of our method, and FIG. 3 shows an example wherein, instead
of the resin distribution medium disposed on the surface of the
mold in FIG. 2, the surface of the mold itself is formed as a resin
distribution medium of the resin injection side by processing
grooves on the mold. Hereinafter, only points different from the
apparatus shown in FIG. 1 will be explained.
[0112] Symbol 20 indicates a porous sheet and, as the material of
porous sheet 20, it is preferred to use a metal thin plate material
(aluminum or stainless steel material), a steel punching metal with
a thickness of 0.1 mm or more, a resin film with a thickness of 0.2
mm or more (a NYLON, polyester, polyethylene, polypropylene or
polyimide film), or an FRP sheet with a thickness of 0.2 mm or
more. Although the hole is preferred to be circular-type from the
viewpoint of processing, the shape is not particularly limited. To
almost extinguish the traces of the porous sheet on the surface of
a molded material after delaminating the porous sheet 20 from the
molded material, the hole diameter is preferably 3 mm or less and
more preferably 1.5 mm or less. The arrangement of the holes may be
either random or regular. Although a desirable pitch of the holes
varies depending on the specification of the reinforcing fiber
substrate to be used, it is preferably 15 mm or less, more
preferably 10 mm or less. The functions required for porous sheet
20 are as follows. The flatness is required to be equal to the
surface roughness required for a final product or more, the
stiffness is required to be a stiffness so that the influence of
the irregularity of the resin distribution medium is not reflected,
and many holes are opened so that the resin can be passed while the
above-described stiffness can be maintained. Symbol 30 indicates
grooves processed on the mold, and it is preferred that each groove
30 has a width of 0.5 mm to 5 mm and a depth of 1 mm to 6 mm and a
pitch of the grooves is in a range of 2 mm to 25 mm, and the
sectional shape is formed as a rectangular, reverse trapezoid or
triangular shape. More preferably, the sectional shape of the
groove is a rectangular shape having a width of about 1 mm and a
depth of about 3 mm, and the pitch of the grooves is about 8
mm.
[0113] In the molding apparatus shown in FIG. 2, peel ply 3a/porous
sheet 20/second resin distribution medium 5a are disposed in this
order from the side contacting reinforcing fiber substrate 4 on the
lower surface of the reinforcing fiber substrate 4. However, the
arrangement of porous sheet 20 and peel ply 3a may be reversed.
Further, in the molding apparatus shown in FIG. 2, as another
example, as shown in FIG. 3, without using resin distribution
medium 5a, grooves for resin injection (example shown in the
figure) or for evacuation may be provided on the tool surface
(molding surface). In this case, because it becomes possible to
perform the resin injection or the evacuation more uniformly over
the entire surface rather than the case using the above-described
resin distribution medium, a good product with less voids or
defects can be obtained easily and stably. On the upper surface of
reinforcing fiber substrate 4, peel ply 3b/resin distribution
medium 5 as used in the conventional method, or those similar to
those disposed at the lower surface side of the reinforcing fiber
substrate 4, may be disposed, and thereafter, the molding is
carried out in a manner similar to that shown in FIG. 1.
[0114] FIG. 4 is a schematic vertical sectional view of a molding
apparatus according to a fourth example of our method, and FIG. 4
shows an example wherein two evacuation gates 6d, 6e to reduce the
pressure are provided on the reinforcing fiber substrate shown in
FIG. 3, and the resin is injected from both sides of the
reinforcing fiber substrate by switching one gate 6d to a resin
injection port on the way. Hereinafter, only points different from
the apparatuses shown in FIGS. 1-3 will be explained.
[0115] Evacuation gate 6d is switched to the resin injection port
on the way of the molding. When it is used as an evacuation gate,
after valve 42 is closed, valve 41 is opened, and when it is
switched to a resin injection gate, after valve 41 is closed, valve
42 is opened.
[0116] In the molding apparatus shown in FIG. 4, under room
temperature or a heated atmosphere, reinforcing fiber substrate 4
is placed on the surface of the mold (tool) processed with grooves
30 via porous sheet 20 and peel ply 3a, and the whole of the
materials and members including evacuation gates 6d, 6e disposed in
plural on the upper surface side to reduce the pressure and the
resin injection gate (grooves 30) disposed on the lower surface
side is covered with the bag material. In this state, when valve 41
is opened, valve 42 and valve 9 are closed, while the inside of bag
material 8 is evacuated and reduced in pressure by evacuation
through the evacuation gate, valve 9 is opened and the resin is
injected into grooves 30 provided as the resin injection gate,
matrix resin 10 flows and is impregnated from the lower surface to
the upper surface of reinforcing fiber substrate 4. In the case
where the thickness of reinforcing fiber substrate 4 is 10 mm or
more, depending on the combination of the resin and the reinforcing
fiber substrate, it is difficult to impregnate the resin completely
up to the upper surface. Therefore, when the resin cannot be well
impregnated up to the upper surface, before the resin reaches the
upper surface of reinforcing fiber substrate 4, valve 41 can be
closed and valve 42 can be opened, thereby switching at least one
of the evacuation gates at the upper surface side (evacuation gate
6d in FIG. 4) to a resin injection gate. When switched to a resin
injection gate, the resin is injected also from the upper surface
side, and the above-described lack of the resin impregnation can be
supplemented. At the same time, because the resin flows from the
side of gate 6d to the side of evacuation gate 6e, voids can be
pushed out in the direction toward evacuation gate 6e accompanying
with this resin flow. Namely, while a quick resin impregnation is
carried out from the side of grooves 30 of the mold provided as the
first resin distribution medium, the lack of resin impregnation
relative to the upper surface side of thick reinforcing fiber
substrate 4 and, at the same time, voids are pushed out toward the
side direction and the enclosure of the voids in the reinforcing
fiber substrate 4 can be prevented. As a result, the molding using
thick reinforcing fiber substrate 4, in which it has been difficult
to sufficiently impregnate the resin because of the existence of a
limit thickness for impregnation, becomes possible, and at the same
time, by avoiding the enclosure of voids at the time of the
molding, it becomes possible to ensure a good quality of the molded
product.
[0117] After impregnation is finished, although the resin is cured
under room temperature or a heated atmosphere, porous sheet 20
having an appropriate stiffness interrupts the influence of the
irregularity of the medium itself and a curing drop of the resin
stored in the medium which occurs at the time of curing. Therefore,
the surface property of the tool surface side of the molded product
taken out after delaminating porous sheet 20/peel plies 3a,
3b/resin distribution medium 5 after releasing from the mold is
exhibited as a surface property to which the flatness of the tool
surface is almost reflected.
[0118] FIG. 5 is a schematic vertical sectional view of a molding
apparatus used for a method of RTM molding according to a fifth
example of our method and, although the basic portions are the same
as those in the aforementioned examples, it is different in that a
degasification medium 54 comprising gas permeation film 50, gas
permeable substrate 51 and seal tape 52 is provided on mold 1, and
evacuation can be carried out from the degasification space formed
between the gas permeation film 50 and the mold 1 through
degasification port 53. Hereinafter, as to the molding method
according to this example, only points different from the
aforementioned embodiments will be explained.
[0119] First, under room temperature or a heated atmosphere,
reinforcing fiber material laminate 4 is placed on the surface of
mold 1 (tool), the whole of the materials and members including
resin injection gate 6f disposed on the upper side and gas
permeation film 50 and gas permeable substrate 51 disposed between
mold 1 and laminate 4 is covered with bag material 8. In this case,
all of the outer edge of gas permeation film 50 is sealed by
adhering it to the mold surface with seal tape 52. In this state,
evacuation is carried out by vacuum pump 11, while the inside of
bag material 8 is reduced in pressure by evacuation through gas
permeation film 50 and the degasification space, the resin is
injected from resin injection gate 6f and, whereby matrix resin 10
is distributed quickly in first resin distribution medium 5 in the
direction along the upper surface of reinforcing fiber substrate 4
(a plane direction) and flows from the upper surface toward the
lower surface of the reinforcing fiber substrate 4 and the resin is
impregnated into the reinforcing fiber substrate 4. After
impregnation is finished, the resin is cured under room temperature
or a heated atmosphere and, thereafter, bag material 8 is
delaminated and the molded material is released from the mold.
[0120] As gas permeation film 50, any material may be used as long
as gas can be permeated but a resin and a liquid cannot be
permeated such as a fine porous sheet or resin film or a substrate
formed by coating a fine porous membrane onto a paper or fabric.
Further, a film having a flatness on its surface can achieve a good
surface quality of a molded product. Furthermore, although it is
desirable that gas permeation film 50 has a releasing property as
the case may be, it is possible to integrate it with a molded
product.
[0121] Gas permeable substrate 51 preferably has a good gas
permeability to increase the impregnation property and preferably
has an irregularity as little as possible to improve the flatness
of a molded product.
[0122] In this method of RTM molding, since, after the pressure in
mold 1 is reduced by evacuation, while the resin is injected into
the mold 1 through resin distribution medium 5, the injected resin
can be impregnated into reinforcing fiber substrate 4 while being
evacuated from the degasification space formed between gas
permeation film 50 and mold 1, the resin can be quickly and
sufficiently broadly on the molding surface at the mold side which
becomes a design surface and a design surface having an excellent
quality can be molded. Besides, by using a film with fine gas holes
and having a high flatness as gas permeation film 50, a design
surface having an extremely small irregularity and a high flatness
can be molded. Therefore, even for a thick reinforcing fiber
material laminate 4, a good resin impregnation can be achieved over
the entire laminate and, as described above, a design surface
having an extremely small irregularity and a high flatness can be
obtained.
[0123] FIG. 6 shows a sixth example. This example is an application
example of the fifth example shown in FIG. 5. This method is a
method of injecting a resin from at least two adjacent resin
injection gates among a plurality of resin injection gates 6g, 6h,
and is effective for a large molded product having a wide area.
Although laminate 5 is formed in a flat-plate like shape in FIG. 6,
even in the case of a molded product having a projection or a
variation in thickness or a laminate difficult to control a resin
flow such as a curved plate, it becomes possible to distribute a
resin over the entire material.
[0124] As to the evacuation route (evacuation ports 53) from the
degasification space formed between gas permeation film 59 and mold
1, a plurality of those are provided and, even in a large molded
product, a sufficient evacuation becomes possible. Further, as
needed, evacuation gate 6a (an evacuation route) can be provided in
addition to the above-described evacuation route from the
degasification space and this can be served to the control of
impregnation direction at the time of resin injection or the
evacuation of excessive resin after resin impregnation.
[0125] FIG. 7 shows an example of a molding apparatus used for a
method of RTM molding according to a seventh example of our method.
In FIG. 7, mold 1 forming a base is made, for example, from a
stainless steel or an aluminum alloy, or another metal for mold or
an FRP, and formed in, for example, a flat-plate like shape.
Reinforcing fiber substrate 4 is placed in this mold 1, in the
figure, on mold 1. Reinforcing fiber substrate 4 is formed, for
example, as a laminate of a plurality of reinforcing fiber woven
fabrics. In this example, medium 5 for distributing a resin is
placed on reinforcing fiber substrate 4 via peel ply 3. Resin
distribution medium 5 preferably has a resin flow resistance of
1/10 or less of the resin flow resistance in reinforcing fiber
substrate 4 and, concretely, a mesh woven fabric made of
polyethylene or polypropylene resin and having a mesh size of #400
or less is preferred. The whole of the materials thus disposed on
mold 1 is covered with bag material 8 comprising a gas-tight
material. As bag material 8, in consideration of gas-tight property
and thermal resistance, for example, a NYLON film is preferably
used. Sealant 7 made of a synthetic rubber with a high adhesive
property prevents air from flowing in from outside so that a
pressure-reduced condition of the inside of bag material 8 can be
maintained. If bag material 8 is formed as a double bag having a
first bag material and a second bag material covering the first bag
material, an air leakage can be prevented and m as a result, the
V.sub.f can be increased.
[0126] Resin injection port 6j and evacuation port 6i for reducing
the pressure in bag material 8 by evacuation are provided in the
sealed bag material 8, and the respective ports connect to a resin
injection line and an evacuation line. For resin injection port 6j
and evacuation port 6i, for example, aluminum C channel materials
can be used. These channel materials may connect to external
members via plastic tubes forming the resin injection line and the
evacuation line. A thermoplastic resin 10 prepared as a matrix
resin for an FRP molded material is stored in a resin pot, for
example. Vacuum trap 13 accumulates excessive resin evacuated from
the molded material through evacuation port 6i. Vacuum pump 11
evacuates from the inside covered with bag material 8 through
vacuum trap 13 and evacuation port 6i and maintains a
pressure-reduced condition in the inside. Peel ply 3 is interposed
to easily remove resin distribution medium 5 from the molded
material and, for example, a woven fabric having a releasing
function such as a NYLON taffeta is used.
[0127] Although the material of the reinforcing fibers forming
reinforcing fiber substrate 4 is not particularly restricted, for
example, glass fibers, carbon fibers, aramide fibers or the like
can be raised. Further, a hybrid structure using or laminating two
or more kinds of these fibers may be employed. Further, a sandwich
structure interposing a core material such as a foam material or a
hollow core between reinforcing fiber layers may be used. As
reinforcing fiber substrate 4, it is preferred to use a woven
fabric which is preformed at an arbitrary fiber content lower than
a target fiber content or a laminate. For example, the woven fabric
is preferably formed as a two-dimensional or three-dimensional
structure, and the laminate may be a laminate in which an arbitrary
number of woven fabrics are laminated, and a preform in which woven
fabrics are bonded to each other is more preferred from the
viewpoint of stabilization of fiber content.
[0128] As resin distribution medium 5, for example, a mesh-like
material may be used, and a structure may be also employed wherein
a resin flow path is formed on mold 1 by grooves and the like and
the surface of the mold 1 formed with the resin flow path itself is
formed as a resin distribution medium. Further, it is possible to
use the reinforcing fiber substrate itself as a resin distribution
medium. As the matrix resin, for example, a polyester resin, a
vinylester resin, an epoxy resin, a phenol resin or the like can be
raised.
[0129] FIG. 8 shows a molding apparatus used for a method of RTM
molding according to an eighth example of our method, and shows an
apparatus wherein a substantial resin distribution medium is formed
on the lower surface side of the reinforcing fiber substrate by
processing grooves on the mold instead of disposing a resin
distribution medium separately and the thickness (thickness
corresponding to the thickness of the molded material or the
reinforcing fiber substrate impregnated with the resin) can be
measured by a dial gauge during evacuation of resin. Points
different from the apparatus shown in FIG. 7 are as follows.
[0130] Dial gauge 21 measures the thickness of the reinforcing
fiber substrate during evacuation of resin. Grooves 30 are
processed on the mold to distribute the resin instead of a resin
distribution medium and it is preferred that each groove 30 has a
width of 0.5 mm to 5 mm and a depth of 1 mm to 6 mm, the
arrangement pitch of the grooves is 2 mm to 25 mm, and the
cross-sectional shape of the groove is a reverse trapezoid, a
triangle or the like. More preferably, the width is about 1 mm, the
depth is about 3 mm, the sectional shape is rectangular, and the
pitch is about 8 mm. As a measurement device other than dial gauge
21 that measures the thickness of the molded product, a micrometer
or laser measuring device can be raised.
[0131] First, reinforcing fiber substrate 4 is placed on the
molding surface of mold 1 and, thereon, peel ply 3 for releasing
(for example, a NYLON taffeta) and gas permeable material 23 (a
polyester nonwoven fabric) are disposed.
[0132] As reinforcing fiber substrate 4, it is preferred to use a
woven fabric preformed at an arbitrary fiber content lower than a
target fiber volume content or a laminate. Because, when a resin is
impregnated, it can be controlled at an arbitrary fiber content,
and the impregnation is good and can be stabilized.
[0133] Further, relative to reinforcing fiber substrate 4, resin
injection port 6j and evacuation port 6i are disposed, for example,
at the end portion and the central portion (FIG. 8) or at both end
portions (FIG. 7), and thereto a resin injection line and an
evacuation line are connected, respectively. These resin injection
port 6j are the resin injection line and evacuation port 6i and the
evacuation line are provided at least one line, respectively. Next,
bag material 8 is covered over the whole of the respective members
laminated on mold 1 from the upper side, and the portion
therearound is sealed by sealant 7 relatively to outside to
maintain the inside of reinforcing fiber substrate 4 and the like
at a pressure-reduced condition. Then, valves A1, A2 are closed,
valve A3 is opened, and the inside evacuated by vacuum pump 11
through evacuation port 6i, a vacuum line and vacuum trap 13, and
the inside of the cavity (the inside covered with bag material 8)
is reduced in pressure at 0.1 MPa or less.
[0134] Next, mold 1 is placed in an oven for heating, and the whole
of the mold is heated up to a predetermined temperature. After mold
1 is heated up to the predetermined temperature, valve A1 is
opened, and resin 10 injected into the cavity through resin
injection port 6j. The resin is distributed in gas permeable
material 23 toward the evacuation line, and the resin in the gas
permeable material 23 is started to be impregnated into reinforcing
fiber substrate 4. Then, when the resin is impregnated over the
entire area in the substrate 4 or when a predetermined amount of
resin is injected even if the resin is not impregnated over the
entire area in the substrate 4, valve A1 is closed and the supply
of resin stopped. It is desirable that the fiber volume content
V.sub.f at the time of this stopping of resin injection is set in a
range of 45% to 60%, more preferably, in a range of 50% to 55%.
This is due to suppressing resin loss due to evacuation as little
as possible. Then, resin evacuation to resin trap 13 is carried out
through evacuation port 6i communicated the vacuum line and resin
injection port 6j after valve A2 is opened until reaching the
predetermined fiber volume content. Although the resin evacuation
may be continued until the resin becomes gel or the resin is cured,
the evacuation is carried out until finally reaching the target
fiber volume content of 55% to 65%. To set the target fiber volume
content in such a range is because, for example, in the case of
members for airplanes, it is necessary to set the V.sub.f at 55% or
more from the comparison in cost and performance with metal
materials and, further, if the fiber volume content becomes a high
V.sub.f more than 65%, problems are liable to occur such as void
generation by bad impregnation, reduction in shear strength between
layers in the molded material, etc.
[0135] Our target fiber volume content V.sub.f can be set, for
example, by the following method.
[0136] Namely, it is possible to estimate the fiber volume content
of the molded material from the thickness of the reinforcing fiber
substrate by the following equation.
V.sub.fFAW.times.PLY/(.rho..times.t) [0137] V.sub.f: fiber volume
content (%) [0138] FAW: weight of reinforcing fiber material
forming the reinforcing fiber substrate (g/cm.sup.2) [0139] PLY:
lamination number of reinforcing fiber materials [0140] .rho.:
density of reinforcing fiber substrate (g/cm.sup.3) [0141] t:
thickness (cm)
[0142] A method may be employed wherein a device that measures the
thickness of the laminate (reinforcing fiber substrate) is disposed
beforehand, and when the thickness reaches a thickness
corresponding to the target fiber volume content while the
thickness of the laminate is measured, valves A2 and A3 are closed.
Alternatively, because the fiber volume content can be defined by
the amounts of fibers and resin in the laminate, a method can be
also employed wherein the amount of resin injection and the amount
of evacuation corresponding to the predetermined fiber volume
content is preset, the resin injection is stopped at the time
reaching the target injection amount, and at the stage reaching the
target evacuation amount, the resin evacuation is stopped.
[0143] Thereafter, the resin is cured at a predetermined
temperature and period of time. After curing is finished, all the
submembers including the gas permeable material and members used
for the resin injection and evacuation lines together with the bag
material and the peel ply are removed and, finally, a molded
product is released from the surface of the mold. The molded
material obtained is served to an aftercuring at predetermined
temperature and period of time, as needed.
[0144] FIG. 9 shows an example of a molding apparatus used for a
method of RTM molding according to a ninth example of our method.
In FIG. 9, mold 1 forming a base is made, for example, from a
stainless steel or an aluminum alloy or another metal for mold or
an FRP and formed in, for example, a flat-plate like shape. Where
mold 1 is thus formed as a flat-plate like mold, although a
concave-type cavity is not necessary, depending on the shape of a
molded product to be molded, a concave-type cavity is formed in
mold 1. Reinforcing fiber material laminate 4A is placed in this
mold 1, in the figure, on mold 1. Reinforcing fiber material
laminate 4A is formed as a laminate of a plurality of reinforcing
fiber materials 4 and each reinforcing fiber material 4 comprises,
for example, a reinforcing fiber woven fabric. Symbols 4a, 4b
indicate the respective end surfaces of reinforcing fiber material
laminate 4A formed in a thick flat plate-like shape. Relative to
these end surfaces 4a, 4b, resin distribution medium 5 for
distributing a resin is disposed via peel ply 3. Peel ply 3 is
disposed to cover the whole of reinforcing fiber material laminate
4A. This resin distribution medium 5 preferably has a low resin
flow resistance of 1/10 or less of the resin flow resistance in
reinforcing fiber material laminate 4A and, concretely, a mesh
woven fabric made of polyethylene or polypropylene resin and having
a mesh size of #400 or less is preferred. The whole of the
materials thus disposed on mold 1 is covered with bag material 8
comprising a gas-tight material. As bag material 8, in
consideration of gas-tight property and thermal resistance, for
example, a NYLON film is preferably used. Sealant 7 made of a
synthetic rubber with a high adhesive property prevents the flowing
in of air from outside so that a pressure-reduced condition of the
inside of bag material 8 can be maintained. Peel ply 3 is laid to
easily remove resin distribution medium 5 and the like from a
molded material, and as peel ply 3, for example, a woven fabric
having a releasing function such as a NYLON taffeta can be
used.
[0145] Resin injection port 6m and evacuation port 6k that reduces
pressure in bag material 8 by evacuation are provided in the sealed
bag material 8 and the respective ports are connected to a resin
injection line and an evacuation line. For resin injection port 6m
and evacuation port 6k, for example, aluminum C channel materials
can be used, and these channel materials may connect to external
members via plastic tubes forming the resin injection line and the
evacuation line. A thermoplastic resin 10 prepared as a matrix
resin for an FRP molded material is stored in a plastic pot, for
example. Vacuum trap 13 accumulates an excessive resin evacuated
from the molded material through evacuation port 6k. Vacuum pump 11
evacuates from the inside covered with bag material 8 through
vacuum trap 13 and evacuation port 6k, and maintains a
pressure-reduced condition in the inside. Valves A1, B1 are
provided for opening/closing the tubes of the resin injection line
and the evacuation line, and for these, for example, joints with
valves or pinch-off pliers can be used. By forming bag material 8
in a double-bag system having a first bag material and a second bag
material covering the first bag material, an air leakage can be
prevented and, as a result, the volume content of the reinforcing
fibers (Vf) can be increased.
[0146] FIG. 10 shows a molding apparatus used for a method of RTM
molding according to a tenth example of our method, and shows an
apparatus for molding a molded material with an integral composite
formation comprising a stringer material with a composite shape,
particularly with an I-type cross section, and a flat plate-like
skin material, as a fiber reinforced resin molded material with a
so-called "skin/stringer" integral structure. Point different from
the apparatus shown in FIG. 9 are as follows.
[0147] A laminate 4B (reinforcing fiber material laminate) of
reinforcing fiber woven fabrics having a flat-plate like cross
section forms a part that forms a skin material, and a laminate 4C
(reinforcing fiber material laminate) of reinforcing fiber woven
fabrics having an I-type cross section forms a part that forms a
stringer material. Evacuation port 6l that reduces pressure and
resin injection port 6n that injects resin are provided, and C
channel materials made of aluminum are preferably used for these
ports. The channel materials connect to external members via
plastic tubes. Jigs 14 are provided to fix reinforcing fiber
material laminate 4C forming the part that forms the stringer
material at a C-type shape from both sides, respectively, and for
the jigs 14, for example, metals or foamed cores can be used. A5,
A4 are valves for opening/closing the tubes and, for these valves,
for example, joints with valves or pinch-off pliers can be used.
The injected resin flows in resin distribution medium 5 disposed
over the exposed upper surface portion of part that forms the skin
material 4B and the lower end surface portions of the reinforcing
fiber material laminate of part that forms the stringer material 4C
with an I-type cross section, and the resin is impregnated mainly
in the thickness direction relatively to the part that forms the
skin material 4B, and impregnated in the direction toward the
portions between layers (a direction along the surface of the
laminate of the reinforcing fiber materials) from the end surfaces
of the reinforcing fiber material laminate relatively to the part
that forms the stringer material 4C.
[0148] FIG. 11 shows a molding apparatus used for a method of RTM
molding according to an eleventh example of our method, and shows
an apparatus for molding a reinforcing fiber material laminate
having a step. 4D is a reinforcing fiber material laminate disposed
partially on the upper surface of the laminate of reinforcing fiber
materials 4 similar to those shown in FIG. 9. The injected resin
flows in resin distribution medium 5 disposed to extend up to one
end surface of reinforcing fiber material laminate 4D and the resin
is permeated in the lamination direction (thickness direction)
relative to the thin plate portion (a portion where the laminate 4D
is not laminated) and impregnated in the direction parallel to the
lamination direction (namely, the direction toward the portions
between layers) from the end surface of the reinforcing fiber
material laminate 4D via the resin distribution medium 5 disposed
on the surface perpendicular to the lamination direction relative
to the thick plate portion (a portion where the laminate 4D is
laminated).
[0149] Next, our methods are carried out as follows, using the
above-described respective apparatuses. The methods will be
explained with respect to the apparatus shown in FIG. 9, which
shows a basic example. First, a plurality of reinforcing fiber
materials 4 are laminated on the molding surface of mold 1 to form
reinforcing fiber material laminate 4A and, thereon, peel ply 3 for
releasing (for example, NYLON taffeta) is disposed to cover the
whole of the laminate 4A. In this case, the outer edge of peel ply
3 is disposed to reach up to sealant 7 as shown in FIG. 9. Next,
resin distribution medium 5 is disposed near both end portions of
reinforcing fiber material laminate 4A to extend up to both end
surfaces 4a, 4b of the laminate 4A and, further, thereon, resin
injection port 6m and evacuation port 6k are disposed,
respectively. Then, the whole of these materials is covered with
bag material 8 (bag film) and the portion between the edge portion
and mold 1 is sealed by sealant 7 over the entire
circumference.
[0150] Because the preparation for molding is completed by the
above-described operations, valve A1 is closed and vacuum pump 11
operates. Next, valve B1 is opened and the inside of the cavity
(the inside of bag material b) is evacuated from evacuation port 6k
through vacuum trap 13. Next, the whole of the members on mold 1 is
heated to a predetermined molding temperature. When the temperature
of mold 1 is increased to the predetermined molding temperature,
valve A4 is opened and matrix resin 10 injected through resin
injection port 6m by the reduced pressure in bag material 8. After
the resin 10 is distributed through one resin distribution medium
5, first, the resin flows quickly in the portions between layers of
reinforcing fiber material laminate 4A having a low flow resistance
and the resin reaches the opposite end portion of the laminate 4A.
When the flow resistances of the respective portions between layers
become at a balanced condition, then, the resin is impregnated in
the thickness direction of the respective reinforcing fiber
materials 4 from the respective portions between layers, namely in
the lamination direction of reinforcing fiber materials 4, and at
the time when the flow resistance reaches a balanced condition, the
resin is impregnated uniformly over the entire area of the
reinforcing fiber material laminate 4A. At the time confirming that
the predetermined amount of resin has been injected, the supply of
the resin is stopped by closing valve A1. Thereafter, the resin is
cured at predetermined temperature and period of time. After
finishing the curing, all the sub members including the resin
distribution medium and the members used for resin injection and
evacuation ports together with the bag material and the peel ply
(releasing woven fabric) are removed from the surface of the molded
material and, finally, the molded material is released from the
surface of the mold. The molded material obtained is sent for
aftercuring at a predetermined temperature and period of time, as
needed.
EXAMPLES
[0151] Hereinafter, we will explain our methods based on
examples.
Example 1
[0152] In the molding apparatus for RTM shown in FIG. 1, breather 2
(glass fiber surface mat, weight: 80 g/m.sup.2) was placed on the
molding surface of mold 1, evacuation gates 6a, 6b were disposed at
both end portions, and vacuum pump was connected. Peel ply 3a was
disposed on breather 2 and, thereon, reinforcing fiber substrate 4
comprising carbon fiber woven fabrics (produced by Toray
Industries, Inc., plain weave fabric CO6343 using carbon fibers
T300, weight: 200 g/m.sup.2) laminated by 120 plies was disposed.
At that time, although peel ply 3a between breather 2 and
reinforcing fiber substrate 4 may be omitted, this structure is
allowed on the premise that the breather is left in a product after
molding and, in such a case, a carbon fiber mesh woven fabric is
desirable as the breather.
[0153] Peel ply 3b was disposed on reinforcing fiber substrate 4,
thereon resin distribution medium 5 of a polypropylene mesh
material (produced by Tokyo Polymer Corporation, "Netron"TSX-400P)
was disposed and, thereon, resin injection gate 6c was disposed and
connected to resin pot 12 via valve 9. The whole of these members
was covered with bag material 8 (bag sheet), and the
circumferential portion sealed by sealant 7 (although omitted in
the figure, a double-bag system was employed). Valve 9 was closed,
the inside of the cavity covered with bag material 8 was evacuated
and reduced in pressure by vacuum pump 11. The whole was heated at
60.degree. C. in an oven and that state was maintained for one
hour. When thermoplastic epoxy matrix resin 10 (the resin viscosity
at 60.degree. C. (injection temperature): 200 mPas, the resin
viscosity after expiration of one hour at 60.degree. C.: 300 mPas)
was stored in resin pot 12 and valve 9 was opened, while the matrix
resin 10 was distributed into the medium 5 through the resin
injection line, the resin was impregnated in the thickness
direction from the upper side toward the lower side, the substrate
with a thickness of about 25 mm was completely impregnated with the
resin without generating a non-impregnated portion. After resin
impregnation, about 50 minutes after, valve 9 was closed to stop
the supply of the resin, the whole was heated up to 130.degree. C.
at about 2/min., and that state was held for 2 hours, the matrix
resin was cured. Thereafter, the temperature was lowered to room
temperature at about 2.degree. C./min. and the whole was taken out
from the mold and the bag material 8 removed. By delaminating the
peel ply from the cured material, the cured resin on the surface of
the molded product, the medium and the breather were removed. A
surface good in surface flatness was obtained for the surface
having contacted with the breather, although an irregularity was
observed on the surface having contacted with the medium.
Example 2
[0154] In the molding apparatus for RTM shown in FIG. 2, on the
molding surface of mold 1, medium 5a of a polypropylene mesh
material (produced by Tokyo Polymer Corporation, "Netron"TSX-400P)
was disposed, and on the circumferential portion thereof,
evacuation gates 6a, 6b were placed and connected to vacuum pump
11. Porous sheet 20 (stainless steel punching metal with a
thickness of 0.2 mm, in which holes each having a diameter of 1 mm
were processed at a pitch of 10 mm) was disposed on the medium 5a.
Thereon, peel ply 3a was disposed and, thereon, reinforcing fiber
substrate 4 comprising carbon fiber woven fabrics (produced by
Toray Industries, Inc., plain weave fabric CO6343 using carbon
fibers T300, weight: 200 g/m.sup.2) laminated by 120 plies was
disposed.
[0155] Peel ply 3b was disposed on reinforcing fiber substrate 4.
Thereon, medium 5b was disposed and, thereon, resin injection port
6c was disposed and connected to resin pot 12 via valve 9 as a
resin injection gate. At that time, a porous sheet may be disposed
between peel ply 3b and medium 5b. The whole of these members was
covered with bag material 8 by a double bag system and the
circumferential portion sealed by sealant 7. Valve 9 was closed,
the inside of the cavity covered with bag material 8 was reduced in
pressure by vacuum pump 11, and the whole heated at 60.degree. C.
in an oven. That state was maintained for one hour. When
thermoplastic epoxy matrix resin 10 (the resin viscosity at
60.degree. C. (injection temperature): 200 mPas, the resin
viscosity after expiration of one hour at 60.degree. C.: 300 mPas)
was stored in resin pot 12 and valve 9 opened, while the matrix
resin 10 was distributed into the upper medium 5b through the resin
injection line, the resin was impregnated in the thickness
direction of carbon fiber woven fabric laminate 4 from the upper
side toward the lower side, and the reinforcing fiber material
laminate 4 with a thickness of about 25 mm was completely
impregnated with the resin without generating a non-impregnated
portion. After resin impregnation, valve 9 was closed to stop the
supply of resin, the whole was heated up to 130.degree. C. at about
2/min., and that state was held for 2 hours. The matrix resin was
cured and, thereafter, the temperature was lowered to room
temperature at about 2.degree. C./min., and the whole was taken out
from the mold and the bag material 8 was removed. As a result of
removing the peel ply from the cured material and removing the
cured resin, the medium and the porous sheet, a surface good in
surface flatness was obtained for the surface having contacted with
the porous sheet, although an irregularity was observed on the
surface having contacted with the medium.
Example 3
[0156] In the molding apparatus for RTM shown in FIG. 3, using the
mold processed with #-type grooves 30 for resin distribution (a
groove having a rectangular cross section with a width of 1 mm and
a depth 3 mm and the pitch of the grooves is 8 mm), resin pot 12
was connected to the grooves via valve 9. Porous sheet 20
(stainless steel punching metal with a thickness of 0.2 mm, in
which holes each having a diameter of 1 mm were processed at a
pitch of 10 mm) was disposed on the molding surface. Thereon, peel
ply 3a was disposed, and thereon, reinforcing fiber substrate 4
comprising carbon fiber woven fabrics (produced by Toray
Industries, Inc., plain weave fabric CO6343 using carbon fibers
T300, weight: 200 g/m.sup.2) laminated by 120 plies was disposed.
Peel ply 3b was disposed on reinforcing fiber substrate 4. Thereon,
medium 5 of a polypropylene mesh material (produced by Tokyo
Polymer Corporation, "Netron"TSX-400P) was disposed and, thereon,
evacuation gate 6 was placed and connected to vacuum pump 11. The
whole of those members were covered with bag material 8 by a double
bag system and the circumferential portion was sealed by sealant 7.
Valve 9 was closed, the inside of the cavity covered with bag
material 8 reduced in pressure by vacuum pump 11, and the whole was
heated at 60.degree. C. in an oven and the state was maintained for
one hour. When thermoplastic epoxy matrix resin 10 (the resin
viscosity at 60.degree. C. (injection temperature): 200 mPas, the
resin viscosity after expiration of one hour at 60.degree. C.: 300
mPas) was stored in resin pot 12 and valve 9 opened, while the
matrix resin 10 was distributed into the molding surface with
grooves through the resin injection line, the resin was impregnated
in the thickness direction of carbon fiber woven fabric laminate 4
from the lower side toward the upper side, and the laminate 4 with
a thickness of 25 mm was completely impregnated with the resin
without generating a non-impregnated portion. After resin
impregnation, valve 9 was closed to stop the supply of the resin,
the whole was heated to 130.degree. C. at about 2.degree. C./min.,
and that state was held for 2 hours. The matrix resin was cured
and, thereafter, the temperature lowered to room temperature at
about 2.degree. C./min., and the whole was taken out from the mold
and the bag material 8 removed. By delaminating the peel ply from
the cured material, the cured resin adhered on the surface of the
molded product, the medium and the porous sheet were removed and
the surface of the molded product appeared, and a surface good in
surface flatness was obtained for the surface having contacted with
the porous sheet, although an irregularity, which was a trace of
the medium, was observed on the surface having contacted with the
medium.
Example 4
[0157] In the molding apparatus for RTM shown in FIG. 4, using the
mold processed with #-type grooves 30 for resin distribution (a
groove having a rectangular cross section with a width of 1 mm and
a depth 3 mm and the pitch of the grooves is 8 mm), resin pot 12
was connected to the grooves via valve 9. Porous sheet 20
(stainless steel punching metal with a thickness of 0.2 mm, in
which holes each having a diameter of 1 mm were processed at a
pitch of 15 mm) was disposed on the molding surface. Thereon, peel
ply 3a was disposed and, thereon, reinforcing fiber substrate 4
comprising carbon fiber woven fabrics (produced by Toray
Industries, Inc., unidirectional woven fabric using carbon fibers
T800S, weight: 190 g/m.sup.2) laminated by 128 plies was disposed.
Peel ply 3b was disposed on reinforcing fiber substrate 4. Thereon,
medium 5 of a polypropylene mesh material (produced by Tokyo
Polymer Corporation, "Netron"TSX-400P) was disposed and, thereon,
evacuation gates 6d, 6e were placed and connected to vacuum pump
11. The whole of those members was covered with bag material 8 by a
double bag system and the circumferential portion sealed by sealant
7. Valve 9 was closed, the inside of the cavity covered with bag
material 8 was reduced in pressure by vacuum pump 11, and the whole
heated at 60.degree. C. in an oven and that state maintained for
one hour. When thermoplastic epoxy matrix resin 10 (the resin
viscosity at 60.degree. C. (injection temperature): 200 mPas, the
resin viscosity after expiration of one hour at 60.degree. C.: 300
mPas) was stored in resin pot 12 and valve 9 was opened, while the
matrix resin 10 was distributed into the molding surface with
grooves through the resin injection line, the resin was impregnated
in the thickness direction of carbon fiber woven fabric laminate 4
from the lower side toward the upper side. However, when that state
is held, at the time when the impregnation progresses to a position
of about 2/3 of the thickness of reinforcing fiber substrate 4, the
resin impregnation becomes astringent.
[0158] Accordingly, when the resin was impregnated up to a position
of 1/2 of the thickness of reinforcing fiber substrate 4, valve 41
was stopped, valve 42 opened and evacuation gate 6d switched to a
resin injection gate. The resin injected from gate 6d was
distributed in distribution medium 5 in a direction toward
evacuation gate 6e, and the resin impregnated into the substrate in
the downward direction via the inside of the medium 5. Finally, the
resin was impregnated over the entire area of the inside of the
substrate. Then, valve 9, 42 were closed to stop the supply of the
resin.
[0159] The whole was heated to 130.degree. C. at about 2.degree.
C./min. and that state held for 2 hours. The matrix resin was cured
and, thereafter, the temperature lowered to room temperature at
about 2.degree. C./min., and the whole was taken out from the mold
and the bag material 8 was removed. By delaminating the peel ply
from the cured material, the cured resin adhered on the surface of
the molded product, the medium and the porous sheet were removed
and the surface of the molded product appeared, and a surface good
in surface flatness was obtained for the surface having contacted
with the porous sheet, although an irregularity, which was a trace
of the medium, was observed on the surface having contacted with
the medium.
Example 5
[0160] In the molding apparatus for RTM shown in FIG. 5, as gas
permeable substrate 51 on the molding surface of mold 1, "peel ply
#60001" produced by a US company, Richmond Corporation, was
disposed and, thereon, a vapor permeable release film "E3760" which
was used in "T.S.B. System" produced by a US company, Richmond
Corporation, was disposed as gas permeation film 50 having a
releasing property, and all the circumference sealed by a nitfurone
tape 52 having a thermal resistance. The degasification space
surrounded by gas permeation film 50 and mold 1 was connected to
vacuum pump 11 through degasification port 53 provided in the mold
1.
[0161] Successively, reinforcing fiber substrate 4 (thickness:
about 25 mm) comprising carbon fiber woven fabrics (produced by
Toray Industries, Inc., plain weave fabric CO6343 using carbon
fibers T300, weight: 200 g/m.sup.2) laminated by 120 plies was
disposed on gas permeation film 50.
[0162] Next, peel ply 3b was disposed on reinforcing fiber
substrate 4. Thereon, resin distribution medium 5 of a
polypropylene mesh material (produced by Tokyo Polymer Corporation,
"Netron"TSX-400P) was disposed and, thereon, resin injection gate
6f was placed and connected to resin pot 12 via valve 9. The whole
of those members was covered with bag material 8 and the
circumferential portion sealed by sealant 7. Valve 9 was closed,
the inside of the cavity covered with bag material 8 was evacuated
and reduced in pressure by vacuum pump 11, and the whole heated at
70.degree. C. in an oven and that state maintained for one hour.
When thermoplastic epoxy matrix resin 10 (the resin viscosity at
70.degree. C. (injection temperature): 130 mPas, the resin
viscosity after expiration of one hour at 70.degree. C.: 320 mPas)
was stored in the resin pot and valve 9 opened, while the matrix
resin 10 was distributed into the medium 5 through the resin
injection line, the resin was impregnated in the thickness
direction of reinforcing fiber substrate 4 from the upper side
toward the lower side. In this case, if gas permeation film 50 does
not exist, the gas present near the lower surface of the substrate
is not well exhausted, the surface of the molded material obtained
becomes "pockmarked-like", but, in this example, by providing gas
permeation film 50, a degasification space was formed between the
film and mold 1, the above-described gas was completely degasified
from the entire area of the lower surface of reinforcing fiber
substrate 4 through gas permeable substrate 51 and, therefore, in
spite of the thickness of the substrate of 25 mm, the resin was
completely impregnated without any non-impregnated portion and, in
particular, the surface quality was remarkably improved. After
resin impregnation, at the stage where a predetermined amount of
resin was injected, valve 9 was closed to stop the supply of the
resin, the whole heated to 130.degree. C. at about 2.degree.
C./min, and that state held for 2 hours. The matrix resin was
cured. Thereafter, the temperature was lowered to room temperature
at about 2.degree. C./min. and the whole was taken out from the
mold and the bag material 8 removed. The lower surface of the cured
molded product was obtained as a surface having a good surface
flatness by delaminating gas permeation film 50.
Example 6
[0163] In the molding apparatus for RTM shown in FIG. 6, similarly
to Example 5, as gas permeable substrate 51 on the molding surface
of mold 1, "peel ply #60001" produced by a US company, Richmond
Corporation, was disposed and, thereon, a vapor permeable release
film "E3760", which was used in "T.S.B. System" produced by a US
company, Richmond Corporation, was disposed as gas permeation film
50 having a releasing property, and all the circumference was
sealed by a nitfurone tape 52 having a thermal resistance. The
degasification space surrounded by gas permeation film 50 and mold
1 was connected to vacuum pump 11 through degasification port 53
provided in the mold 1.
[0164] Successively, reinforcing fiber substrate 4 (thickness:
about 25 mm) comprising carbon fiber woven fabrics (produced by
Toray Industries, Inc., plain weave fabric CO6343 using carbon
fibers T300, weight: 200 g/m.sup.2) laminated by 120 plies was
disposed on gas permeation film 50. At that time, evacuation gate
6a was disposed also on one side of the lower surface of the
reinforcing fiber substrate.
[0165] Peel ply 3b was disposed on reinforcing fiber substrate 4.
Thereon, resin distribution medium 5 of a polypropylene mesh
material (produced by Tokyo Polymer Corporation, "Netron"TSX-400P)
was disposed and, thereon, two resin injection gates 6g, 6h were
placed and connected to resin pot 12 via valve 9. The whole of
those members was covered with bag material 8 and the
circumferential portion sealed by sealant 7. Valve 9 was closed,
the inside of the cavity covered with bag material 8 evacuated and
reduced in pressure by vacuum pump 11, and the whole heated at
70.degree. C. in an oven and that state maintained for one hour.
When thermoplastic epoxy matrix resin 10 (the resin viscosity at
70.degree. C. (injection temperature): 130 mPas, the resin
viscosity after expiration of one hour at 70.degree. C.: 320 mPas)
was stored in the resin pot and valve 9 opened, while the matrix
resin 10 flowed in medium 5 simultaneously through two resin
injection lines and the resin was distributed on the surface, the
resin impregnated in the thickness direction of reinforcing fiber
substrate 4 from the upper side toward the lower side, and the
substrate with a thickness of about 25 mm was impregnated
completely without any non-impregnated portion.
[0166] At that time, although the resin reached the lower surface
of reinforcing fiber substrate 4 quickly in the area immediately
under injection gates 6g, 6h, namely, the resin reached slowly in
the lower surface of the reinforcing fiber substrate in the
intermediate area positioned between the two gates, finally the
resin was completely impregnated by evacuation due to the
degasification route of gas permeation film 50.
[0167] After resin impregnation, at the stage where a predetermined
amount of resin was injected, valve 9 was closed to stop the supply
of the resin, the whole heated to 130.degree. C. at about 2/min.,
and that state held for 2 hours. The matrix resin was cured. The
time for resin impregnation was short by the evacuation also
through evacuation gate 6a, as compared to that in Example 5.
[0168] Thereafter, the temperature was lowered to room temperature
at about 2/min., and the whole was taken out from the mold and the
bag material 8 removed. The lower surface of the cured molded
product was obtained as a surface having a good surface flatness by
delaminating gas permeation film 50.
Example 7
[0169] In the molding apparatus for RTM shown in FIGS. 7 and 8, a
carbon fiber woven fabric cut at a length of 500 mm and a width of
500 mm was laid up on mold 1 comprising a stainless steel flat
plate. A reinforcing fiber material used to form a reinforcing
fiber substrate was a unidirectional woven fabric CZ8431DP (weight:
190 g/m.sup.2) of "TORAYCA" T800S produced by Toray Industries,
Inc., and it was laminated by 128 plies totally. Peel ply 3 (NYLON
taffeta) and resin distribution medium 5 (polypropylene mesh
material) were disposed on the reinforcing fiber substrate 4, resin
injection port 6j and evacuation port 6i were disposed relative to
the substrate, the whole of these members was covered with bag
material 8 (NYLON film) and the circumferential portion sealed by
sealant 7 made of a synthetic rubber having a high adhesive
property (the bag was applied as a double bag system although
omitted in the figure).
[0170] In this state, valves A1, A2 were closed, valve A3 opened,
and the evacuation carried out through the evacuation port via the
vacuum line and vacuum trap 13 to reduce pressure in the cavity to
0.1 MPa or less. Thereafter, the mold was placed in an electric
oven and the inside of the oven heated at 60.degree. C. After the
temperature of the whole of reinforcing fiber substrate reached
60.degree. C., valve A1 was opened and matrix resin 10 injected
through resin injection port 6j at a vacuum pressure. As the resin,
an epoxy resin (the resin viscosity at 60.degree. C. (injection
temperature): 200 mPas, the resin viscosity after expiration of one
hour at 60.degree. C.: 300 mPas) was used. The injected resin was
impregnated into the substrate 4 while flowing in resin
distribution medium 5 having a low flow resistance. At the time
when the resin was injected by a predetermined amount of 3650
cm.sup.3, valve A1 was closed to stop the supply of the resin. At
that time, the fiber volume content of the substrate capable of
being estimated from the thickness of the reinforcing fiber
substrate was about 48%.
[0171] Next, valve A2 was opened, the resin injection line opened
to the vacuum side via the vacuum trap and excessive resin in the
reinforcing fiber substrate was evacuated into the vacuum trap 13
from the end portion of the reinforcing fiber substrate.
Thereafter, at the time when the evacuation amount of the resin
reached a predetermined amount of 1150 cm.sup.3, valves A2, A3 were
closed to stop the supply of the resin. Then, the temperature in
the electric oven was elevated to 130.degree. C., heated and cured
for about two hours. After heat-curing, the sub members such as the
bag material were removed, CFRP (carbon fiber reinforced plastic)
molded material was released from the molding surface. As the
result of determination of the fiber volume content of the CFRP
molded material at positions of the resin injection side, the
evacuation side and an intermediate point therebetween, they were
in a range of 57.2% to 58.2%. Namely, as compared to the time
before resin evacuation immediately after resin impregnation, the
fiber volume content could be increased to the range of the target
value.
Example 8
[0172] In the above, a carbon fiber woven fabric 4 cut at a length
of 500 mm and a width of 500 mm was laid up on mold 1 comprising a
stainless steel flat plate on which #-type grooves 30 (width: 1 mm,
depth: 4 mm, pitch: 15 mm) were processed as a flow path of resin.
The carbon fiber woven fabric 4 was a unidirectional woven fabric
CZ8431DP (weight: 190 g/m.sup.2) of "TORAYCA" T800S produced by
Toray Industries, Inc., and laminated by 128 plies totally. On this
substrate, gas permeable material 23 (polyester non-woven fabric)
was disposed via peel ply 3 and, thereon, evacuation port 6i was
disposed. Further, resin injection port 6j was disposed on the
grooves 30 for resin flow path formed on mold 1, the whole of these
members was covered with bag material 8 (NYLON film) by a double
bag system and the circumferential portion sealed by sealant 7 made
of a synthetic rubber having a high adhesive property.
[0173] In that state, valves A1, A2 were closed, valve A3 opened
and evacuation was carried out through evacuation port 6i via the
vacuum line and vacuum trap 13 to reduce the pressure in the cavity
to 0.1 MPa or less. Thereafter, the mold was placed in an electric
oven and the inside of the oven heated at 60.degree. C. After the
temperature of the whole of the reinforcing fiber substrate reached
60.degree. C., valve A1 was opened and matrix resin 10 injected
through resin injection port 6j at a vacuum pressure. The epoxy
resin of Example 1 was used. The injected resin was distributed in
the grooves for distributing resin and the resin in the grooves was
impregnated into the substrate. As the result of measuring the
thickness after the resin was impregnated into the whole of the
reinforcing fiber substrate, it was 28.1 mm, and the fiber volume
content was 48%.
[0174] Next, valve A1 was closed and valve A2 opened, and excessive
resin in the reinforcing fiber substrate was evacuated into vacuum
trap 13. In this example, the target fiber volume content of the
CFRP molded material was set at 55 to 60%. Since it was recognized
from the experimental result beforehand that the curing shrinkage
of the molded material in the thickness direction was about 1.2%,
at the time when the thickness became 23.8 mm, valves A2, A3 were
closed to stop evacuation of the resin. Thereafter, the temperature
in the oven was elevated to 130.degree. C., heated and cured for
about two hours. After heat-curing, the sub members such as the bag
material were removed and, as the result of taking out the CFRP
molded material from the molding surface, a CFRP molded material
having a fiber volume content of 57.1 to 59.3% (thickness: 23.5 mm)
within a range of the above-described target fiber volume content
could be obtained.
Example 9
[0175] Our method was applied to the molding of a thick flat plate.
In the apparatus shown in FIG. 9, a carbon fiber woven fabric 4
(reinforcing fiber material) cut at a length of 300 mm and a width
of 300 mm was laid up on mold 1, comprising a stainless steel flat
plate, by 128 plies, to form reinforcing fiber material laminate 4A
having a total thickness of about 25 mm. The reinforcing fiber
material was a unidirectional woven fabric CZ8431DP (weight: 190
g/m.sup.2) of "TORAYCA" T800S produced by Toray Industries, Inc.
Further, peel ply 3 (NYLON taffeta) was disposed on reinforcing
fiber material laminate 4A, resin distribution medium 5
(polypropylene mesh material) were disposed relative to both end
surfaces 4a, 4b of the laminate 4A, resin injection port 6m and
evacuation port 6k were disposed to communicate with both ends of
the laminate 4A, the whole of those members was covered with bag
material 8 (NYLON film) (by a double bag system, although omitted
in the figure) and the circumferential portion was sealed by
sealant 7 made of a synthetic rubber having a high adhesive
property.
[0176] Then, valve A1 was closed, valve B1 opened and evacuation
port 6k was communicated with the vacuum line via vacuum trap 13
communicated with the evacuation line, and the pressure in the
cavity reduced to 0.1 MPa or less.
[0177] Thereafter, the mold was placed in an electric oven and the
inside of the oven was heated at 60.degree. C. After the
temperature of the whole of reinforcing fiber substrate reached
60.degree. C., valve A1 was opened and matrix resin 10 injected
through resin injection port 6m under a pressure-reduced atmosphere
with 0.08 to 0.1 MPa. As the injected resin, an epoxy resin (the
resin viscosity at 60.degree. C. (injection temperature): 200 mPas,
the resin viscosity after expiration of one hour at 60.degree. C.:
300 mPas) was used. The injected resin first flowed in resin
distribution medium 5 having a low flow resistance, and at the time
reaching the end of reinforcing fiber material laminate 4A, the
resin flowed therefrom mainly in the laminate 4A in the direction
along the lamination surface of the laminate 4A and, thereafter,
the resin was impregnated in the thickness direction and this resin
flow was observed from the above position of transparent bag
material 8.
[0178] At the time when the predetermined amount of resin was
injected, valve A1 was closed to stop the supply of the resin.
Thereafter, the temperature in the oven was elevated to 130.degree.
C., heated and cured for about two hours. After heat-curing, the
sub members such as the bag material 8 were removed and the CFRP
molded material was taken out from the molding surface. As a
result, the CFRP molded material was completely impregnated with
resin in spite of a relatively small thickness of 25 mm. Further,
the surface property of the molded material was flat.
Example 10
[0179] Our method was applied to the molding of a skin/stringer
integrally structural material. In the apparatus shown in FIG. 10,
a carbon fiber woven fabric 4 (reinforcing fiber material) cut at a
length of 500 mm and a width of 500 mm was laid up on mold 1 to
form reinforcing fiber material laminate 4B. The reinforcing fiber
material was a unidirectional woven fabric (weight: 190 g/m.sup.2)
of "TORAYCA" T800S produced by Toray Industries, Inc., and
laminated by 128 plies totally (hereinafter, referred to as
"reinforcing fiber material laminate for forming a skin material
4B"). Next, a carbon fiber woven fabric 4 cut at a width of 98 mm
and a length of 500 mm was placed by 32 plies using jig 14 for
fixing a C-type shape. Another laminate of the carbon fiber woven
fabric 4 was further prepared and the two laminates were disposed
to form a structure back to back symmetrically with jigs 14
disposed at both sides to form a reinforcing fiber material
laminate having an I-type cross section. It was placed on the
reinforcing fiber material laminate that forms a skin material 4B
which had been already been laid up. Then, on the I-type
reinforcing fiber material laminate, a carbon fiber woven fabric 4
cut at a width of 66 mm and a length of 500 mm was laid up by 32
plies (hereinafter, the reinforcing fiber material laminate placed
on the reinforcing fiber material laminate that forms a skin
material 4B is referred to as "reinforcing fiber material laminate
that forms a stringer material 4C").
[0180] Next, peel ply 3 (NYLON taffeta), resin distribution medium
5 (polypropylene mesh material), resin injection ports 6m, 6n and
evacuation ports 6k, 6l were disposed on these reinforcing fiber
material laminates, as shown in FIG. 10. Then, the whole of those
members was covered with bag material 8 (NYLON film) by a double
bag system, and the circumferential portion sealed by sealant 7
made of a synthetic rubber having a high adhesive property. As to
evacuation, valves A4, A5 were closed, valves B1, B2 opened and
evacuation ports 6k, 6l opened via vacuum trap 13 communicated with
the vacuum line, and the pressure in the cavity reduced to 0.1 MPa
or less.
[0181] After bagging and the pressure reducing were finished, the
mold was placed in an electric oven and the inside of the oven was
heated at 70.degree. C. When the temperature of the whole of the
reinforcing fiber material laminate reached 70.degree. C., valves
A4, A5 were opened and matrix resin 10 injected through resin
injection ports 6m, 6n under a pressure-reduced condition. An epoxy
resin (the resin viscosity at 70.degree. C. (injection
temperature): 130 mPas, the resin viscosity after expiration of one
hour at 60.degree. C.: 320 mPas) was used. The injected resin
flowed in the resin distribution medium having a low flow
resistance and was impregnated into the substrate. Although the
resin was impregnated in the thickness direction relative to the
reinforcing fiber material laminate that forms a skin material 4B,
relative to the reinforcing fiber material laminate that forms a
stringer material 4C, the resin flowed in the direction of portions
between layers of the laminate from the end surface of the lower
side of the I-type reinforcing fiber material laminate, and was
impregnated mainly in the thickness direction of the respective
reinforcing fiber materials (namely, the thickness direction of the
I-type reinforcing fiber material laminate) after being permeated
into the I-type reinforcing fiber material laminate. At the time
when the predetermined amount of resin was injected, valves A4, A5
were closed to stop the supply of the resin. Thereafter, the
temperature in the oven was elevated to 130.degree. C., heated and
cured for about two hours. After heat-curing, the sub members such
as the bag material 8 were removed and the CFRP molded material was
taken out from the molding surface. In the CFRP molded material
obtained, the resin was completely impregnated particularly up to
the corners of the stringer part. Further, the surface property of
the stringer part was flat.
Example 11
[0182] Our method was applied to the molding of a panel with a
step. In the apparatus shown in FIG. 11, a carbon fiber woven
fabric 4 (produced by Toray Industries, Inc., plain weave fabric
CO6343 using carbon fibers T300, weight: 190 g/m.sup.2) cut at a
length of 500 mm and a width of 500 mm was laid up by 24 plies on
mold 1 of an aluminum flat plate, and thereon, the carbon fiber
woven fabric cut at a length of 150 mm and a width of 500 mm was
laid up by 56 plies was laid up as a thick plate portion, to form
reinforcing fiber material laminate 4D. As shown in FIG. 11, on the
whole of the reinforcing fiber material laminate, peel ply 3 (NYLON
taffeta) was disposed, resin distribution medium 5 (polypropylene
mesh material) was disposed to extend up to one end surface of the
reinforcing fiber material laminate 4D, resin injection port 6o and
evacuation ports 6a, 6b were disposed as shown in FIG. 11, the
whole of these members covered with bag material 8 (NYLON film) by
a double bag system, and the circumferential portion sealed by
sealant 7 made of a synthetic rubber having a high adhesive
property. Valves B1, B2 were opened at a condition where valves A1,
A2 were closed and the pressure in the cavity was reduced to 0.1
MPa or less by vacuum pump 11 through the vacuum line via vacuum
trap 13.
[0183] Thereafter, the mold was placed in an electric oven and the
inside of the oven heated at 70.degree. C. Valve A1 was opened, and
matrix resin 10 (an epoxy resin (the resin viscosity at 70.degree.
C. (injection temperature): 130 mPas, the resin viscosity after
expiration of one hour at 60.degree. C.: 320 mPas)) injected
through resin injection port 6o under a pressure-reduced condition.
Although the injected resin flowed in the resin distribution medium
5 having a low flow resistance and permeated and impregnated into
the thin plate portion in the lamination direction, as to the thick
plate portion, the resin permeated into the portions between layers
of the laminate through the part of the resin distribution medium
disposed in the direction of the surface perpendicular to the
lamination direction and, then, the resin was impregnated in the
thickness direction of the laminate. At the time when flowing out
of the resin from evacuation port 6b was observed, valve B2 was
closed and valve A2 opened, the resin injection was carried out.
Next, at the time when flowing out of the resin from evacuation
port 6a was observed, valves A1, A2 were closed to stop resin
injection, the electric oven was heated to 130.degree. C., and the
resin cured for about two hours at a constant temperature
condition. After heat-curing, the sub members such as the bag
material 8 were removed and the CFRP molded material taken out from
the molding surface. In the CFRP molded material obtained, the
resin was completely impregnated particularly as to all portions of
the thin plate portion and the thick plate portion, and the surface
property of the stringer part was flat.
INDUSTRIAL APPLICATIONS
[0184] Our methods of RTM molding are suitable particularly for
molding of a thick FRP structural material and an FRP structural
material having an excellent designability, or having excellent
lightweight property and strength by increase of fiber volume
content, can be molded.
* * * * *