U.S. patent application number 12/794487 was filed with the patent office on 2010-11-04 for method and device for the production of tubular structural components.
Invention is credited to Hauke Lengsfeld, Volker Reye.
Application Number | 20100276069 12/794487 |
Document ID | / |
Family ID | 40679895 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100276069 |
Kind Code |
A1 |
Lengsfeld; Hauke ; et
al. |
November 4, 2010 |
METHOD AND DEVICE FOR THE PRODUCTION OF TUBULAR STRUCTURAL
COMPONENTS
Abstract
The present invention provides a method for the production of a
tubular structural component. A tubular moulding tool having an
inner mould surface which is shaped corresponding to an outer
surface of the structural component is provided. A support surface
of an expandable support which is formed such that in an unexpanded
state, it fills the moulding tool, leaving an expansion spacing of
the support surface to the mould surface, is covered with a tubular
fibre-woven fabric. After the support has been arranged in the
moulding tool, the fibre-woven fabric is pressed against the mould
surface by expanding the support and is infiltrated by a curable
matrix. From another point of view, a device is provided for the
production of a tubular structural component.
Inventors: |
Lengsfeld; Hauke; (Helmste,
DE) ; Reye; Volker; (Hamburg, DE) |
Correspondence
Address: |
JENKINS, WILSON, TAYLOR & HUNT, P. A.
3100 Tower Blvd., Suite 1200
DURHAM
NC
27707
US
|
Family ID: |
40679895 |
Appl. No.: |
12/794487 |
Filed: |
June 4, 2010 |
Current U.S.
Class: |
156/156 ;
156/494 |
Current CPC
Class: |
B29D 23/001 20130101;
Y02T 50/40 20130101; B30B 5/02 20130101; B29C 70/48 20130101; B29C
70/446 20130101; B29C 70/541 20130101; B29C 33/505 20130101; B29K
2307/04 20130101; B29C 70/345 20130101; B29C 70/36 20130101; B29L
2023/22 20130101; B29L 2031/3082 20130101; B29K 2105/089 20130101;
B29C 70/443 20130101; Y02T 50/43 20130101 |
Class at
Publication: |
156/156 ;
156/494 |
International
Class: |
B29C 70/56 20060101
B29C070/56; B32B 37/10 20060101 B32B037/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2007 |
DE |
10 2007 060 029.3 |
Nov 12, 2008 |
EP |
PCT/EP2008/065355 |
Claims
1. A method for producing a tubular structural component,
comprising the steps of: providing a tubular moulding tool which
has an inner mould surface shaped corresponding to an outer surface
of the structural component; covering with a tubular fibre-woven
fabric a support surface of an expandable support which is formed
such that in an unexpanded state, it fills the moulding tool while
leaving an expansion spacing of the support surface to the mould
surface; arranging the support in the moulding tool; pressing the
fibre-woven fabric against the mould surface by expanding the
support with radial expansion of the fibre-woven fabric; and
infiltrating the fibre-woven fabric with a curable matrix.
2. The method according to claim 1, wherein the support surface is
covered such that fibres of a fibre layer of the fibre-woven fabric
run diagonally around the support.
3. The method according to claim 1, wherein after the support has
been covered, the tubular fibre-woven fabric has a greater length
than the structural component.
4. The method according to claim 1, wherein the support comprises a
pressure membrane, the support being expanded by the production of
a pressure differential between an inner region of the support and
an intermediate region between the pressure membrane and the
moulding tool.
5. The method according to claim 4, wherein to produce the pressure
differential, the pressure in the inner region of the support is
increased above atmospheric pressure.
6. The method according to claim 4, wherein to produce the pressure
differential, the pressure in the intermediate region is reduced
below atmospheric pressure.
7. The method according to claim 1, wherein furthermore a step of
arranging a reinforcing element between the support surface and the
fibre-woven fabric is provided.
8. The method according to claim 7, wherein furthermore a step of
guiding the reinforcing element, during the expansion of the
support, in a radial direction of the moulding tool is
provided.
9. The method according to claim 7, wherein the reinforcing element
is arranged between the support surface and the fibre-woven fabric
as a pre-impregnated or non-impregnated semi-finished fibre
product.
10. The method according to claim 7, wherein the reinforcing
element is arranged between the support surface and the fibre-woven
fabric as a pre-cured semi-finished fibre product.
11. The method according to claim 7, wherein the reinforcing
element is arranged in a correspondingly configured recess in the
support surface.
12. Method according to claim 7, wherein furthermore a placeholder
is arranged in a cavity between the reinforcing element and the
tubular fibre-woven fabric.
13. The method according to claim 12, wherein the placeholder has a
membrane sheath and furthermore a step of expanding the placeholder
by increasing a pressure in the membrane sheath is provided.
14. A device for producing a tubular structural component,
comprising: a tubular moulding tool which has an inner mould
surface shaped corresponding to an outer surface of the structural
component; an expandable support which is formed such that, in an
unexpanded state, it fills the moulding tool while leaving an
expansion spacing between a support surface of the support and the
mould surface, the expansion spacing amounting to 1 to 10 cm; a
means for expanding the support such that when the support surface
is covered with a tubular fibre-woven fabric and when the support
is arranged in the moulding tool, the support surface radially
expands the fibre-woven fabric and presses it against the mould
surface; and a means for infiltrating the fibre-woven fabric with a
curable matrix.
15. The device according to claim 14, wherein the support comprises
a pressure membrane, the expansion means being configured to
produce a pressure differential between an inner region of the
support and an intermediate region between the pressure membrane
and the moulding tool.
16. The device according to claim 15, wherein the expansion means
comprises a compressor for increasing a pressure in the inner
region of the support above atmospheric pressure.
17. The device according to claim 15, wherein the expansion means
comprises a vacuum pump for reducing a pressure in the intermediate
region below atmospheric pressure.
18. The device according to claim 14, wherein the support comprises
a recess for inserting a reinforcing element.
19. The device according to claim 18, wherein furthermore a means
for guiding the reinforcing element, during the expanding of the
support, in a radial direction of the moulding tool is
provided.
20. The device according to claim 19, wherein the guiding means
comprises at least one guide cover for fitting to at least one end
of the moulding tool and/or of the support, the guide cover having
a guide slot running in a radial direction of the tubular moulding
tool for guiding the reinforcing element.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of PCT/EP2008/065355 and
claims the benefit of U.S. Provisional Application No. 61/007,492,
filed Dec. 13, 2007 and German Patent Application No. 10 2007 060
029.3, filed Dec. 13, 2007, the entire disclosures of which are
herein incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method and a device for
the production of a tubular structural component, in particular a
fuselage barrel section of an aircraft or spacecraft.
[0003] Although the present invention and the problem on which it
is based can be applied to any tubular structural components with
any cross-sectional shapes, they will be described in detail in
respect of the production of fuselage barrel sections of
aircraft.
[0004] In the construction of aircraft fuselage, particularly for
commercial aircraft, it is usual to prefabricate tubular or
barrel-shaped fuselage sections individually and to assemble them
into the finished fuselage in a subsequent final assembly.
Materials which are used to an increasing extent are fibre
composite materials, for example carbon fibre reinforced plastics
materials (CFRP) which make it possible to achieve a high stability
of the sections with a relatively low weight.
[0005] A fuselage barrel section based on fibre composite materials
is produced according to a conventional method using a winding body
as a positive mould, onto which layers of a fibre material
pre-impregnated with a resin matrix (prepreg) are wound and
subsequently cured, for example by a heat treatment. The fibre
placement or winding procedure is very time-intensive due to the
size of the component and to different fibre directions of the
prepreg layers.
[0006] Since it is possible for slight differences in diameter of
adjacent fuselage barrel sections to impede the final assembly, the
winding body has to have a high dimensional accuracy and must not
expand any further after the fibre placement procedure, for example
during a heat treatment. At the same time, it is necessary to
configure the winding body such that it can be split or collapsed,
so that after the curing procedure, it can be contracted inwards by
splitting or collapsing and can be removed from the fuselage barrel
section. The provision of a winding body which combines these
characteristics is associated with high costs.
[0007] In order to obtain a fuselage barrel section which has a
smooth outer surface and correspondingly advantageous aerodynamic
characteristics, pressure sheets are also applied for the curing
procedure. In this case, there must not be any auxiliary material,
for example tear-off or ventilation fabric between the pressure
sheet and prepeg-woven fabric as this would result in a rough
surface of the fuselage barrel section. In general, it is not
possible to remove excess resin or air from the space between the
winding body and the pressure sheets. However, an inadequate
removal of resin or air results in porous and thus low-quality
components.
[0008] Further problems are caused in that the thickness of the
prepeg-woven fabric is reduced during the curing procedure by the
so-called setting path, which is to be considered during shaping
and when the pressure sheets are pressed on. However, the setting
path of the prepreg material can vary as a function of the material
charge and thus, for example when there is a charge with a
relatively long setting path, this can give rise to porosity. Since
the internal diameter of the fuselage barrel section is
predetermined in a fixed manner by the external diameter of the
winding body, the external diameter of the fuselage barrel section
is reduced during the gradual setting of the prepreg interlaid
scrim. Consequently, the prepeg-woven fabric is pushed together in
the peripheral direction of the section, which readily results in
an undesirable waviness of the fibres.
SUMMARY OF THE INVENTION
[0009] It is therefore the object of the present invention to
achieve a high quality at a low cost when tubular structural
components and in particular fuselage barrel sections are
produced.
[0010] This object is achieved according to the invention by a
method for the production of a tubular structural component which
has the features of claim 1 and by a device for the production of a
tubular structural component which has the features of claim
14.
[0011] The idea on which the present invention is based is to use
for the production of the structural component a moulding tool
which is also tubular and is configured as a negative mould, i.e.
it has an inner mould surface which is a negative of the outer
surface to be formed of the structural component. The term
"tubular" as used herein is not restricted to tubes with a circular
cross section, but explicitly includes tubes with elliptical,
rectangular or other randomly shaped cross sections, in which case
the cross section does not need to be constant over the length of
the tubes, but can be narrowed, widened or shaped in another
way.
[0012] In order to arrange fibre-woven fabrics on the inner surface
of the moulding tool, a support is also provided which can be
expanded, in other words can be selectively brought at least into
an expanded and an unexpanded state. In the unexpanded state, the
shape of the support is smaller than the space described by the
inner surface of the moulding tool such that the support can be
arranged in this state inside the moulding tool. In so doing, there
remains between the inner surface of the moulding tool and an outer
surface of the support a minimum spacing which is termed here the
expansion spacing.
[0013] The outer surface of the support which opposes the inner
surface of the moulding tool when the support is arranged in the
moulding tool serves as a support surface which supports the
fibre-woven fabric to be processed during the production process.
The fibre-woven fabric is provided in tubular form and arranged on
the support surface such that the support surface is covered by the
tubular fibre-woven fabric. For example, the tubular fibre-woven
fabric is pulled over the support while the support, in the
unexpanded state, is freely accessible outside the moulding
tool.
[0014] The support is then arranged in the moulding tool such that
the support surface covered by the tubular fibre-woven fabric is
opposite the inner surface of the moulding tool, the expansion
spacing which is reduced by the thickness of the fibre-woven fabric
remaining between the fibre-woven fabric and the inner surface. The
support is then expanded, as a result of which this remaining
spacing is shrunk to zero and the fibre-woven fabric is pressed
against the inner surface of the moulding tool by the support
surface of the expanded support. In a final step, the fibre-woven
fabric held between the support surface and the inner surface of
the moulding tool is infiltrated by a curable matrix.
[0015] The use of a negative mould which reproduces the outer
contour of the fuselage barrel section makes it possible to observe
the desired external dimensions with a high degree of accuracy. The
moulding tool can be configured without a considerable constructive
expense in one piece or in a simple manner such that it can be
opened outwards or can be disassembled. The setup of the
fibre-woven fabric on the support, regardless of the moulding tool
and curing tool, makes it possible to provide a plurality of
supports suitable for a given moulding tool and to alternately
charge one of the supports with fibre-woven fabric outside the
moulding tool, while another support is located in the moulding
tool for curing. In this manner, it is possible to use the moulding
tool and, if appropriate, a curing station in a continuous manner,
which reduces the production costs and shortens dead time.
[0016] The use of fibre-woven fabric which is infiltrated by a
separately provided matrix affords further advantages in terms of
time and greater freedom in the construction of the structural
components which have been produced compared to the conventional
use of prepregs. Fibre undulations are prevented due to the fact
that the fibre-woven fabric is stretched by the expansion of the
support in the peripheral direction.
[0017] According to a preferred development, the expansion spacing
is between 1 and 10 cm, for example approximately 5 cm. With such a
spacing, sufficient clearance remains between the support surface
and the inner surface of the moulding tool in order to move the
support into and out of the moulding tool in a particularly fast
and contact-free manner, while on the other hand the tubular
fibre-woven fabric is prevented from being overstretched during the
expanding procedure.
[0018] According to a preferred development, the support surface is
covered such that fibres of a fibre layer of the fibre-woven fabric
run diagonally around the support. This advantageously allows the
tubular fibre-woven fabric to expand radially, the angle of
inclination of the fibres changing without the fibres being
overstretched in their longitudinal direction. After the support
has been covered, the tubular fibre-woven fabric is preferably
longer than the structural component, such that when the support is
expanded radially, the fibre-woven fabric is able to contract in
its longitudinal direction, while still completely covering the
support surface.
[0019] According to a preferred development, the support comprises
a pressure membrane, the support being expanded by the production
of a pressure differential between an inner region of the support
and an intermediate region between the pressure membrane and the
moulding tool. The pressure membrane exerts on the tubular
fibre-woven fabric a uniform contact pressure which can be
precisely adjusted by the pressure differential, over the entire
inner surface of the tubular moulding tool, which allows a
particularly uniform shaping of the wall of the structural
component.
[0020] To produce the pressure differential, the pressure in the
inner region of the support is preferably increased above
atmospheric pressure. Suitable compression devices can be
accommodated inside the support, so that when the support is
arranged in the moulding tool, the support can be expanded without
sealing off the intermediate region, for example. Alternatively or
in addition, to produce the pressure differential, the pressure in
the intermediate region between the pressure membrane and the
moulding tool is decreased below atmospheric pressure. This allows
the inner region to be made accessible, for example for inspection
purposes. The pressure membrane does not need to be configured for
high absolute pressures.
[0021] According to a preferred development, a step is furthermore
provided for arranging a reinforcing element between the support
surface and the fibre-woven fabric. This makes it possible to
connect the reinforcing element, for example a stringer, to be
connected to the structural component in a single operation with
the production of the structural component. The reinforcing element
is preferably guided in at least one guide slot which runs in a
radial direction of the tubular moulding tool, while the support is
being expanded. The reinforcing element is thus guided precisely
into the desired connecting position without tilting.
[0022] According to a preferred development, the reinforcing
element is arranged between the support surface and the fibre-woven
fabric as a pre-impregnated or non-impregnated semi-finished fibre
product. The reinforcing element is connected by jointly
infiltrating the reinforcing element and the wall of the tubular
structural component and by a joint curing process.
[0023] According to another preferred development, the reinforcing
element is arranged between the support surface and the fibre-woven
fabric as a pre-cured semi-finished fibre product. This allows the
co-bonding of the reinforcing element with the wall of the tubular
structural component, in which case for example the curable matrix
with which the tubular fibre-woven fabric is infiltrated, acts as
an adhesive.
[0024] According to a preferred development, the reinforcing
element is arranged in a correspondingly configured recess in the
support surface. This facilitates the charging of the support with
the reinforcing element.
[0025] According to a preferred development, a placeholder is
arranged in a cavity between the reinforcing element and the
tubular fibre-woven fabric. During the curing procedure when the
reinforcing element is subjected to the mutual pressure of the
support surface and the inner surface of the moulding tool, this
placeholder keeps the desired cavity of the reinforcing element
free. The placeholder preferably has a membrane sheath, in which
case a step is furthermore provided for expanding the placeholder
by increasing a pressure in the membrane sheath. A placeholder
which can be expanded in this manner can be contracted again after
the curing procedure and can therefore be easily removed.
[0026] According to a preferred development of the device according
to the invention, at least one guide cover is provided for
positioning on at least one end of the moulding tool ad/or of the
support. The guide cover has a guide slot which runs in a radial
direction of the tubular moulding tool and is to guide the
reinforcing element. During the expansion of the support, the
guiding slot guides the reinforcing element precisely in a radial
direction into the desired position on the inside of the structural
component, irrespective of the shape of the reinforcing element and
the shape of the support surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] In the following, the invention is described in detail on
the basis of embodiments with reference to the accompanying figures
of the drawings.
[0028] FIG. 1A-C are schematic perspective views of a device for
the production of a fuselage barrel section of an aircraft
according to a first embodiment of the invention;
[0029] FIG. 2A-G are cross-sectional views of details of a device
according to a second embodiment during the production of a tubular
structural component; and
[0030] FIG. 3A-D are cross-sectional views of details of a device
according to a third embodiment during the production of a tubular
structural component.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0031] In the figures, the same reference numerals denote the same
or functionally identical components, unless indicated
otherwise.
[0032] FIG. 1A to 1C are three schematic perspective views of a
device for the production of a fuselage barrel section of an
aircraft, each of the three figures showing different steps of a
production method. The fuselage barrel section to be produced is
approximately in the shape of a cylinder barrel, the cross section
typically differing from the ideal circular shape and changing over
the length of the section.
[0033] FIG. 1A shows a tubular moulding tool 102 with an inner
surface 106 which is shaped corresponding to the desired shape of
the outer surface of the fuselage barrel section to be produced.
The moulding tool 102 is a so-called negative mould, because its
inner surface 106 forms a negative shape for the outer surface of
the fuselage barrel section. Next to the moulding tool 102 is a
support 110 for supporting a tubular fibre-woven fabric 114.
[0034] The support 110 is of an approximately cylindrical shape,
having approximately the same length as the moulding tool 102 and
an external diameter which is slightly smaller than the internal
diameter of the moulding tool. Consequently, it can be arranged
both inside and outside the moulding tool 102. The support 110
comprises an inner frame which defines the illustrated shape and
its lateral surface 108 is covered by a resilient pressure membrane
which separates an inner region of the support from the outside in
a pressure-tight manner. For the simple, contact-free insertion of
the support inside the moulding tool, the support and/or the
moulding tool can be provided with rollers for example (not
shown).
[0035] The surface of the pressure membrane arranged around the
lateral surface 108 of the approximately cylindrical support 110
forms a support surface 108 which supports the tubular fibre-woven
fabric 114 during the production of the fuselage barrel section. At
the start of the production method, the support 110 is arranged
outside the moulding tool 102. The tubular fibre-woven fabric 114
is cut to size and drawn over the support 110 until it completely
covers the support surface 108. The fibre-woven fabric 114 used is,
for example a non-woven fabric, for example a so-called NCF
(non-crimped fabric) which consists of carbon fibres or other
suitable fibres and can be reinforced locally according to
constructive details of the fuselage section to be produced. The
fibre-woven fabric 114 comprises a plurality of fibre layers of
different orientations in which the fibres 116 run diagonally, as
shown by way of example, i.e. spirally around the periphery of the
support 110. In further fibre layers (not shown), fibres run at
other inclination angles diagonally or parallel to the longitudinal
direction of the support 110.
[0036] The length 118 of the cut tubular fibre-woven fabric 114 is
greater than the length of the support 110 and of the moulding tool
102, such that the fibre-woven fabric 114 not only covers the
support surface 108 of the support 110, but projects beyond the
support 110 at both ends thereof.
[0037] FIG. 1B shows a subsequent step of the production method in
which the support 110 covered by the fibre-woven fabric 114 has
been moved into the moulding tool 102. Since the diameter of the
support 110 is smaller than the internal diameter of the moulding
tool 102, the support 110 fits into the moulding tool 102 without
the support surface 108 contacting the inner surface 106 of the
moulding tool. Instead, the support surface 108 and the inner
surface 106 of the moulding tool 102 run approximately parallel, a
minimum spacing 112 of, for example 5-10 cm remaining at any point
between them. The fibre-woven fabric 114 covering the support
surface 108 projects at both ends out of the moulding tool 102 due
to its length 118.
[0038] FIG. 1C shows a further step of the production method in
which a compressor 205 has produced an excess pressure in the inner
region of the support 110. The pressure membrane, forming the
support surface, of the support is inflated by the excess pressure,
such that the support 110 is expanded radially beyond the
dimensions of its inner frame. The radial expansion of the support
110 stretches the tubular fibre-woven fabric 114 in the direction
of the periphery of the support 110. At the same time, due to the
fibres 116 which run diagonally around the support, the tubular
fibre-woven fabric 114 has contracted in its longitudinal direction
up to a shortened length 119. In this respect, the tubular
fibre-woven fabric 114 had initially been cut generously such that
it still completely covered the support surface even with its
shortened length.
[0039] In the illustrated expanded state of the support 110, the
pressure membrane presses the fibre-woven fabric 114 against the
inner surface 108 of the moulding tool due to the excess pressure
in the inner region of the support 110. In a further step, the
fibre-woven fabric, fixed in this manner, is infiltrated by a
liquid, curable resin matrix 115, for example in that the resin
matrix is introduced from one end of the moulding tool 102, as
indicated by arrows, into the gap between the pressure membrane and
the moulding tool 102.
[0040] The resin matrix is then cured, for example by a heat
treatment. The excess pressure is discharged from the inner region
of the support 110, so that the support 110 returns into its
original, unexpanded state and can easily be removed from the
moulding tool 102. The finished fuselage barrel section is removed
from the moulding tool 102. Sections which are moulded such that
they taper towards one end are removed from the moulding tool 102,
for example in the direction of the other end. Alternatively, the
moulding tool 102 can be configured in two or more parts, such that
it can be opened for the finished section to be removed.
[0041] A further embodiment of the production method will now be
described in more detail with reference to FIG. 2A-G. FIG. 2A-G are
each cross-sectional views of a detail of the periphery of the
support 110 for different steps of the method.
[0042] FIG. 2A shows the mentioned detail of the support 110 in a
starting state in which a fibre-woven fabric has not yet been
arranged on the support surface 108 and the support 110 is outside
the moulding tool 102. The support 110 comprises a rigid support
frame 111 with a substantially circular cross section. The support
frame 111 is formed from aluminium, for example and has on its
surface a large number of small holes for charging with vacuum
and/or excess pressure, which have not been shown here to improve
clarity. A slot-like recess 210 is configured in one location of
its periphery to later receive a reinforcing element. The periphery
of the support frame 111 is flattened in an edge region 211 on both
sides of the recess 210.
[0043] The surface of the support frame 111 is covered by a
pressure membrane 200 which extends over the entire lateral surface
of the overall approximately cylindrical support frame 111 and is
connected to the surface of the support frame 111 in a
pressure-tight manner at the edges of the lateral surface. An inner
region 202 between the pressure membrane 200 and the support frame
111 is therefore sealed off in a pressure-tight manner from the
exterior. The pressure membrane 200 is configured as a plastics
material film, for example.
[0044] FIG. 2B shows a state of the support 110 of FIG. 2A after a
vacuum pump 204 has been connected to the interior 202 and has
evacuated it via the fine holes 213 in the surface of the support
frame 111, of which only one hole 213 is shown here by way of
example. The vacuum in the interior 202 tightly suctioned the
pressure membrane against the support frame 111. In particular, the
pressure membrane follows the contour of the support frame 111 as
far as into the recess 120.
[0045] In FIG. 2C, a reinforcing element 208 with a T-shaped
profile, as used for example in aircraft construction as a
so-called T-stringer, has been inserted into the recess 120. The
horizontal bar 209 of the T-shaped profile rests inside the
flattened area 211 against the support frame 111 covered by the
pressure membrane 200.
[0046] In FIG. 2D, the pressure membrane 200 has been covered by a
tubular fibre-woven fabric 114 consisting of carbon fibres. The
outer surface 108 of the pressure membrane 200 acts as the support
surface 108, supporting the fibre-woven fabric 114, of the support
110. The reinforcing element 208 is included between the support
surface 108 and the fibre-woven fabric 114 and is held in the
recess 210. Since the horizontal bar 209 of the T-shaped profile is
also in a concealed position inside the flattened area 111, the
fibre-woven fabric 114 does not have a bulge above the reinforcing
element 208, but follows a gentle curve.
[0047] FIG. 2E shows the support 110 which has been prepared in
this manner and has been charged with the reinforcing element 208
and the fibre-woven fabric 114, after it has been pushed into a
tubular moulding tool 102. The support 110 is smaller than the
interior of the moulding tool 102 and is configured corresponding
to the shape of said moulding tool to the extent that a spacing 112
always remains between its support surface 108 and the surface 106
of the moulding tool. In other words, the support surface 108 and
the mould surface 106 run parallel to one another in the spacing
112 in the illustrated state. On the other hand, the fibre-woven
fabric 114 and the pressure membrane 200 as well as the pressure
membrane and the support frame 111 contact one another and are
shown at a distance from one another in FIG. 2B-E merely for the
sake of clarity.
[0048] FIG. 2F shows the support 110 arranged in the moulding tool
102 after the interior 202 between the support frame 111 and the
pressure membrane 200 has been connected to a compressor 205 and
has been subjected to excess pressure through the fine holes 203.
The excess pressure has inflated the pressure membrane 200 such
that it has expanded in a radial direction 212 as far as the
surface 106 of the moulding tool 102. Both the pressure membrane
and the fibre-woven fabric have been stretched by the expansion.
The reinforcing element 208 and the fibre-woven fabric 114 have
been guided by the expanding pressure membrane 200 to the mould
surface 106 and, in the illustrated state, are pressed against the
mould surface 106 with uniform contact pressure provided by the
excess pressure. During the expansion procedure, the reinforcing
element 208 has been guided through the recess 120 in a radial
direction 112 and, in the illustrated state, is also still held in
the recess 120, as in a guide slot, and is thus positioned
precisely.
[0049] FIG. 2G shows the state after the space between the pressure
membrane 200 and the moulding tool 102 has been filled with a
curable matrix system 115. The matrix 115 has infiltrated both the
fibre-woven fabric 114 and the fibre material of the reinforcing
element 208, as indicated by the hatching. The excess pressure in
the inner region 202 of the support 110 is maintained during the
subsequent curing procedure by a heat treatment. The excess
pressure is then discharged and the finished fuselage barrel
section 100 is removed from the moulding tool 102.
[0050] FIG. 3A-D show another embodiment of the production method.
The figures are again each cross-sectional views of details of the
periphery of the support 110 for different steps of the method.
[0051] FIG. 3A shows a state corresponding to FIG. 2B in which a
pressure membrane 200 has been arranged tightly along the surface
of a support frame 111, for example likewise by evacuating the
interlying inner region of the support. As in the above embodiment,
a recess 120 for a reinforcing element is configured in the support
frame 111, said recess having here, however, the shape of a wide,
trapezoidal trough.
[0052] In the state shown in FIG. 3B, a reinforcing element 208
which is formed from prepreg and has an .OMEGA.-shaped profile, a
so-called .OMEGA. stringer has been arranged in the recess 210. A
cavity 304 to be configured in the finished fuselage barrel section
under the .OMEGA.-shaped profile of the stringer 208 is filled here
by a placeholder 300 which is formed in this case by way of example
from a membrane sheath 301 filled with compressed air. A tubular
fibre-woven fabric 114 covers the support surface 108 formed by the
pressure membrane 200, the foot portion 306 of the .OMEGA. stringer
and the outwardly facing side of the placeholder 300.
[0053] In the state shown in FIG. 3C, the support 110 prepared thus
has been arranged in a tubular moulding tool 102. An expansion
spacing 112 remains between the support surface 106 and the mould
surface, as in the embodiment described above. In order to expand
the support 110, its inner region 202 is subjected to excess
pressure and/or the intermediate region 206 located between the
pressure membrane 200 and the moulding tool 102 is subjected to
vacuum. In order to be able to guide the .OMEGA. stringer 208
precisely in a radial direction 212 during the expansion procedure,
a guide pin 502 is anchored in the placeholder 300 at both ends of
the .OMEGA. stringer 208. Said guide pin slides in a radially 212
running guide slot 302 which is recessed in a guide cover 500
respectively fitted to the ends of the moulding tool 102.
[0054] FIG. 3D shows a state in which the pressure membrane presses
the tubular fibre-woven fabric 114 together with the .OMEGA.
stringer 208 and the included placeholder 300 against the inner
surface 106 of the moulding tool 102 by the applied pressure
differential between inner region 202 and intermediate region 206.
In subsequent steps, the fibre-woven fabric 114 and the .OMEGA.
stringer 208 are jointly infiltrated by a resin matrix and cured.
In so doing, the introduced matrix and the resin material contained
in the prepreg of the .OMEGA. stringer 208 are combined. After a
curing heat treatment, the excess pressure in the inner region 202
and the vacuum in the intermediate region 206 are discharged and
the cured fuselage barrel section is removed from the moulding tool
102. After the excess pressure in the interior of the placeholder
300 has also been released, said placeholder is removed below the
.OMEGA. stringer 208 in order to free its cavity 304.
[0055] Although the present invention has been presently described
using preferred embodiments, it is not restricted thereto, but can
be modified in many different ways.
[0056] For example, reinforcing elements of various other profiles
can be used. It is possible to produce fuselage barrel sections and
other tubular structural components with complex, tapering cross
sections, door and window openings.
LIST OF REFERENCE NUMERALS
[0057] 100 structural component [0058] 102 moulding tool [0059] 104
outer surface [0060] 106 mould surface [0061] 108 support surface
[0062] 110 support [0063] 111 frame [0064] 112 expansion spacing
[0065] 114 fibre-woven fabric [0066] 115 matrix [0067] 116 fibres
[0068] 118 length of the fibre-woven fabric before expansion [0069]
119 length of the fibre-woven fabric after expansion [0070] 200
pressure membrane [0071] 202 inner region [0072] 203 hole [0073]
204 vacuum pump [0074] 205 compressor [0075] 206 intermediate
region [0076] 208 reinforcing element [0077] 209 horizontal portion
[0078] 210 recess [0079] 211 flattened area [0080] 212 radial
direction [0081] 300 placeholder [0082] 301 membrane sheath [0083]
302 guide slot [0084] 304 cavity [0085] 306 foot portion [0086] 500
guide cover [0087] 502 guide pin
* * * * *