U.S. patent application number 14/741981 was filed with the patent office on 2015-10-08 for wrinkle control method and tool therefor.
The applicant listed for this patent is AIRBUS OPERATIONS LIMITED. Invention is credited to Timothy SANDERSON, Stephen WILLIAMS.
Application Number | 20150283766 14/741981 |
Document ID | / |
Family ID | 45475602 |
Filed Date | 2015-10-08 |
United States Patent
Application |
20150283766 |
Kind Code |
A1 |
WILLIAMS; Stephen ; et
al. |
October 8, 2015 |
WRINKLE CONTROL METHOD AND TOOL THEREFOR
Abstract
A method for forming a laminate component, the method comprising
the steps of: a) providing a tool having a moulding surface; b)
arranging a stack of ply layers on the moulding surface of the
tool; and c) moulding the stack of ply layers over the moulding
surface in a moulding process, wherein the tool has a wrinkle
control feature in its moulding surface for managing the
development of wrinkle in the ply layers during the moulding
process, and wherein the wrinkle control feature cooperates with
the stack of ply layers during the moulding process to produce a
local surface undulation in a nominal surface of the laminate
component nearest the tool to either prevent wrinkling in the ply
layers or initiate wrinkling in one or more of the ply layers at a
predetermined location. Also, a tool having a wrinkle control
feature, and a laminate component so formed.
Inventors: |
WILLIAMS; Stephen; (EBBW
VALE, GB) ; SANDERSON; Timothy; (Bristol,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AIRBUS OPERATIONS LIMITED |
Bristol |
|
GB |
|
|
Family ID: |
45475602 |
Appl. No.: |
14/741981 |
Filed: |
June 17, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13671809 |
Nov 8, 2012 |
9067371 |
|
|
14741981 |
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Current U.S.
Class: |
156/196 |
Current CPC
Class: |
B29C 70/46 20130101;
B29C 70/462 20130101; B29C 70/56 20130101; B29C 70/30 20130101;
B29L 2031/001 20130101; B29L 2031/3076 20130101; B29L 2031/3085
20130101; B29C 70/88 20130101; B29C 70/54 20130101; Y10T 428/24612
20150115; Y10T 156/1002 20150115; Y10T 428/24446 20150115 |
International
Class: |
B29C 70/46 20060101
B29C070/46; B29C 70/54 20060101 B29C070/54 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 23, 2011 |
GB |
1120219.9 |
Claims
1. A method for forming a laminate component, the method comprising
the steps of: a) providing a tool having a moulding surface; b)
arranging a stack of ply layers on the moulding surface of the
tool; and c) moulding the stack of ply layers over the moulding
surface in a moulding process, wherein the moulding surface is
shaped such that the surface of the laminate component nearest the
tool when the stack of ply layers are arranged on the moulding
surface of the tool substantially conforms to a nominal surface of
the laminate component, and wherein the tool has a wrinkle control
feature in its moulding surface for managing the development of
wrinkle in the ply layers during the moulding process, and wherein
the wrinkle control feature cooperates with the stack of ply layers
during the moulding process to produce a local surface undulation
in the surface of the laminate component nearest the tool that
deviates from the nominal surface of the laminate component to
either prevent wrinkling in the ply layers or initiate wrinkling in
one or more of the ply layers at a predetermined location.
2. A method according to claim 1 wherein the wrinkle control
feature comprises a recess extending into the moulding surface of
the tool.
3. A method according to claim 1 wherein the wrinkle control
feature comprises a protrusion extending out from the moulding
surface of the tool.
4. A method according to claim 1 wherein the wrinkle control
feature provides an increased path length over a region of the
moulding surface which accommodates excess material in at least one
of the ply layers.
5. A method according to claim 1 wherein the wrinkle control
feature accommodates sufficient excess material in at least one of
the ply layers to prevent wrinkling of the ply.
6. A method according to claim 1 wherein the wrinkle control
feature initiates wrinkling in at least one of the ply layers at a
predetermined location adjacent the wrinkle control feature.
7. A method according to claim 1 wherein the wrinkle control
feature initiates wrinkling in at least one of the ply layers at a
predetermined location remote from the wrinkle control feature.
8. A method according to claim 1 wherein the wrinkle control
feature has a height which varies across its extent.
9. A method according to claim 1 wherein the wrinkle control
feature has a width which varies across its extent.
10. A method according to claim 1 wherein the wrinkle control
feature is substantially dart or arrowhead shaped.
11. A method according to claim 1 wherein the wrinkle control
feature extends to an edge of the moulding surface of the tool.
12. A method according to claim 1 comprising a plurality of wrinkle
control features.
13. A method according to claim 12 wherein at least some of the
wrinkle control features are adjacent one another.
14. A method according to claim 1 wherein the moulding surface has
a complex three-dimensional shape.
15. A method according to claim 1 wherein the tool is elongate and
has a longitudinal direction, and the shape of the moulding surface
varies in the longitudinal direction.
16. A method according to claim 1 wherein the tool is a male mould
tool.
17. A method according to claim 1 performed repeatedly using the
same or a similar tool to produce a plurality of substantially
identical laminate components.
18. A method according to claim 1 wherein the laminate component so
formed has a complex three-dimensional shape.
19. A method according to claim 1 wherein the laminate component so
formed has an L-section or a C-section.
20. A method according to claim 1 wherein the laminate component so
formed is an aircraft component.
21. A method according to claim 20 wherein the aircraft component
is a wing spar.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation application of
U.S. Ser. No. 13/671,809, filed Nov. 8, 2012, which is based on,
and claims priority from, British Application Number 1120219.9,
filed Nov. 23, 2011, the disclosures of which are hereby
incorporated by reference herein in their entirety.
FIELD OF THE INVENTION
[0002] The invention relates to a tool for forming a laminate
component, a method for forming a laminate component, and a
laminate component so formed.
BACKGROUND OF THE INVENTION
[0003] Laminate components may be formed by arranging a stack of
ply layers on a mould tool, allowing the stack of plies to deform
to the shape of the tool and then curing the plies to produce a
solid consolidated component. When a laminate stack is folded over
a complex three-dimensional moulding surface of the tool, some of
the ply layers may be forced to contract or expand depending on the
nature of the surface curvature. If the ply layers comprise a
material which has minimal ability to contract, for example carbon
fibre or Kevlar or glass fibre in a composite material, the
geometry may cause wrinkling in the ply layers of the finished
laminate component.
[0004] Wrinkles in the plies of composite laminate components are
undesirable because wrinkles may lead to voids, discontinuities and
resin rich or resin poor regions in the component. These defects
may result in reduced performance of the component, for example
reduced strength and stiffness, and may affect the durability of
the component. A composite component having wrinkle in its ply
layers may, therefore, perform less well than the intended
component according to the design shape of the component without
wrinkle
[0005] The development of wrinkle, especially wrinkle affecting
external plies of the laminate stack, may also lead to reduced
accuracy of surfaces of the component, presenting a particular
problem if wrinkle develops on a surface which is designed to
engage with other components, and may require concessionary work to
be carried out before the finished component can be accepted.
[0006] Wrinkle may develop in an unpredictable manner such that,
when multiple composite components are formed using the same or
similar tools, the components may exhibit different wrinkle
characteristics. For example, the extent of wrinkle and the
location or locations at which wrinkle develops in each component
may vary. This unpredictable nature of wrinkle development leads to
non-standard (and therefore time consuming) inspection, correction
and justification work, and makes it difficult to produce
substantially identical components having predictable features and
properties.
[0007] For these reasons, it is generally desirable to eliminate or
control the development of wrinkle within the laminate stack during
the moulding process, so that the shape and properties of the
component produced may be optimised and so that multiple components
produced to the same design can be made substantially
identical.
SUMMARY OF THE INVENTION
[0008] A first aspect of the invention provides a tool having a
moulding surface for forming a component by laminating a stack of
ply layers which are arranged on the moulding surface of the tool
during a moulding process, the tool comprising a wrinkle control
feature in its moulding surface for managing the development of
wrinkle in the ply layers, wherein the wrinkle control feature is
arranged to cooperate with the stack of ply layers during the
moulding process to produce a local surface undulation in a nominal
surface of the laminate component nearest the tool to either
prevent wrinkling in the ply layers or initiate wrinkling in one or
more of the ply layers at a predetermined location.
[0009] A further aspect of the invention provides a method for
forming a laminate component, the method comprising the steps of:
a) providing a tool having a moulding surface; b) arranging a stack
of ply layers on the moulding surface of the tool; and c) moulding
the stack of ply layers over the moulding surface in a moulding
process, wherein the tool has a wrinkle control feature in its
moulding surface for managing the development of wrinkle in the ply
layers during the moulding process, and wherein the wrinkle control
feature cooperates with the stack of ply layers during the moulding
process to produce a local surface undulation in a nominal surface
of the laminate component nearest the tool to either prevent
wrinkling in the ply layers or initiate wrinkling in one or more of
the ply layers at a predetermined location.
[0010] The invention is advantageous in that it allows the
development of wrinkle during moulding of a laminate component to
be controlled. By producing a local surface undulation in a nominal
surface of the laminate component nearest the tool, the problems
associated with uncontrolled wrinkle in the laminate may be
eliminated or at least significantly reduced.
[0011] The nominal surface of the laminate component is the design
surface of the component. The local surface undulations are known,
predictable changes to that design shape that are considered an
acceptable result of the manufacturing process. The wrinkle that
would otherwise develop due to the shape of the moulding surface of
the tool may be either eliminated entirely, or the wrinkle may be
reduced or moved into predictable and/or less problematic location,
so that the deterioration in performance compared to the intended
design shape of the component without wrinkle is reduced or
eliminated. The structure and properties of the component are,
therefore, more predictable, and so the component may be more
accurately analysed, optimised and manufactured.
[0012] The ply layers may be fibrous ply layers, for example plies
containing fibres of carbon or glass or Kevlar or any other
suitable material. The plies may be prepreg plies, or may be dry
fibre plies. The fibre plies may be unidirectional, woven, or any
other suitable type of fibre plies.
[0013] The tool may be used to form a component using any
manufacturing process in which a composite component is shaped by
interaction with a tool having a moulding surface. For example, the
ply layers may be arranged on the tool as a stack of plies or
alternatively the individual ply layers may be arranged over the
tool sequentially one after the other. In either case the plies may
be arranged on the tool manually or in an automated process or in a
semi-automated process.
[0014] The tool may be a male or female tool. A male tool have a
generally convex shape onto which the plies are laid, whereas a
female tool has a generally concave shape into which the plies are
laid.
[0015] The laminate stack may be provided with a removable peel ply
layer between structural plies and the moulding surface of the tool
during the forming process. The peel ply layer may be removed from
the laminate stack when the laminate component and the tool are
separated or before the finished component is accepted.
Alternatively, the ply layers may be arranged on the tool without a
peel ply layer.
[0016] The wrinkle control feature may comprise a recess.
Alternatively, the wrinkle control feature may comprise a
protrusion, or may comprise both a recess and a protrusion. The
wrinkle control feature is adapted to provide an increased path
length over a region of the moulding surface to accommodate excess
material in at least one of the ply layers. By increasing the path
length in a region where the ply layers would otherwise be expected
to contract more than the material properties will allow, the
tendency for these plies to wrinkle will be reduced.
[0017] The wrinkle control feature may be adapted to accommodate
sufficient excess material in at least one of the ply layers so as
to prevent wrinkling of the ply.
[0018] The wrinkle control feature may be adapted to initiate
wrinkling in at least one of the ply layers at a predetermined
location adjacent the wrinkle control feature. Alternatively, the
wrinkle initiated by the wrinkle control feature may be at a
predetermined location remote from the wrinkle control feature.
[0019] The wrinkle control feature may, therefore, be used to
prevent or minimise wrinkle in regions of the composite component
in which it is particularly desirable to prevent wrinkle from
occurring, for example surfaces experiencing particular stress
concentrations or surfaces which are designed to engage with other
components.
[0020] The wrinkle control feature may have a height which varies
across its extent.
[0021] The wrinkle control feature may have a width which varies
across its extent.
[0022] The wrinkle control feature may be substantially dart or
arrowhead shaped. Alternatively, the wrinkle control feature may be
substantially trapezoidal, crescent shaped, elliptical,
rectangular, or have any other shape which acts to produce the
desired surface undulation in the nominal surface of the laminate
component to control wrinkling in the ply layer(s).
[0023] The wrinkle control feature may extend to an edge of the
moulding surface of the tool. The wrinkle control feature may
extend towards a corner of the moulding surface, and may extend up
to the corner or only part of the way between an edge of the
moulding surface and a corner of the moulding surface.
Alternatively, the wrinkle control feature may be located at any
position on the moulding surface of the tool in which it can
effectively manage the development of wrinkle in the laminate
stack.
[0024] The wrinkle control feature may have a dimension (e.g.
height) that is small, preferably no more than the thickness of 10
individual plies, and preferably less than the thickness of 5
individual plies.
[0025] The tool may comprise a plurality of wrinkle control
features, and at least some of the wrinkle control features may be
adjacent one another.
[0026] The moulding surface of the tool may have a complex
three-dimensional shape. A complex three-dimensional shape has a
cross section which varies in all three dimensions.
[0027] The tool may be elongate and have a longitudinal direction,
and the shape of the moulding surface may vary in the longitudinal
direction. The change in shape may be include a change due to a
curve or kink in the longitudinal axis of the tool. The tool may,
therefore, be adapted to produce a component having a longitudinal
axis and a varying cross section in the direction of its
longitudinal axis, or a curve or kink in its longitudinal axis.
[0028] The method may be performed repeatedly using the same or a
similar tool to produce a plurality of substantially identical
laminate components. The components produced may have predictable,
uniform wrinkle characteristics so that the variation between the
components is less than would be the case if they had been formed
using a tool without a wrinkle control feature so that unmanaged
wrinkle was allowed to develop in each component.
[0029] By producing components which are substantially identical,
it is possible to reduce the variation in structure analysis and
performance of components formed using the same or similar tools,
and to simplify and standardise any necessary inspection,
correction and justification work.
[0030] The method may be used to form a component having a complex
three-dimensional shape. In particular, the component may have an
L-section or a C-section. The component may be an aircraft
component, and in particular may be a wing spar. The wing spar may
have a C-section or two L-sections attached together to form a
C-section. Alternatively, a tool or method according to the
invention may be used to form any laminate component for use in any
other application.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 illustrates a plan view of an aircraft;
[0032] FIG. 2 illustrates a cross section through the aircraft wing
along A-A in FIG. 1 showing the front and rear C-section spars;
[0033] FIGS. 3a-3e illustrate a process for manufacturing a
laminate component, which is one of the C-section wing spars;
[0034] FIG. 4a illustrates the tool used in the process, and FIG.
4b shows a portion of the tool;
[0035] FIG. 5a-5c illustrate wrinkle development in laminate
stacks;
[0036] FIG. 6a illustrates a wrinkle control feature in the
moulding surface of the tool, and
[0037] FIG. 6b illustrates a plurality of alternative wrinkle
control features;
[0038] FIG. 7a illustrates a laminate component formed using the
tool and having a local surface undulation produced by the wrinkle
control feature, and FIG. 7b shows a portion of the laminate
component; and
[0039] FIG. 8a-8c illustrates alternative arrangements of wrinkle
control features.
DETAILED DESCRIPTION OF EMBODIMENT(S)
[0040] FIG. 1 illustrates an aircraft 1 having a fuselage 2 and
wings 3, 4. The wing 3 has a wing box 4, shown in section A-A
through the wing 3 in FIG. 2, comprising a front spar 5, a rear
spar 6, an upper wing cover 7 and a lower wing cover 8. The wing
covers 7, 8 provide upper and lower aerodynamic surfaces and the
spars 5, 6 are composite C-section beams which support the wing
covers.
[0041] The front spar 5 has a longitudinal axis running span-wise
along its length and a cross section which varies along the
direction of the longitudinal axis. The spar is formed by a
moulding process, as indicated in FIG. 3, by: [0042] a) laying up
multiple fibrous ply layers 9 to form a laminate 10 stack on a
lay-up table 11 (FIG. 3a); and [0043] b) heating the laminate stack
with a heating system 12 (FIG. 3b); and [0044] c) providing a tool
20 (FIG. 3c) having a moulding surface with a controlled shape
designed to cooperate with the laminate stack 10 to form the spar
5; and [0045] d) arranging the laminate stack 10 on the moulding
surface of the tool 20 and moulding the laminate stack over the
moulding surface of the tool (FIG. 3d); and [0046] e) curing the
laminate stack 10 to produce a solid, consolidated component 10'
(FIG. 3e)
[0047] The laminate stack 10 has a first surface 10a which is
nearest the tool during the moulding process and a second surface
10b which opposes the first surface. The laminate stack 10 may
additionally be provided with a removable peel ply layer on its
first surface 10a. Alternatively no peel ply layer may be used. The
peel ply layer sits between the first surface of the laminate stack
10 and the tool 20 during the moulding process and is removed from
the laminate stack 10 before the spar 5 is accepted.
[0048] During the moulding process, the first surface 10a
cooperates with the moulding surface of the tool 20, and
substantially takes the shape of the moulding surface so that the
laminate stack assumes the intended shape of the cured component
10'.
[0049] The tool 20, shown in FIG. 4a, has a longitudinal axis L and
a cross section which varies in the direction of the longitudinal
axis, and the spar 5 formed on the tool has a corresponding
longitudinal axis and a varying cross section in the direction of
its longitudinal axis. The span-wise variation in the height and
depth of a spar may be significant, for example the height
variation may be well over a metre in large aircraft, and a spar
may additionally include a change in direction via a kink or a
curve along its length. The three-dimensional design shape of the
moulding surface of the tool 20 results in wrinkle developing in
the laminate stack 10 when it is arranged on the tool during the
moulding process described above, which cannot be eliminated while
maintaining a structurally optimised design for the spar 5.
[0050] Wrinkle in the ply layers may be in the form of a loop or
kink or fold or a combination of these, and may affect one or more
ply layers. For example, wrinkle may take the form of a loop (or
loops) 30 or fold 31 in an individual ply layer, as indicated in
laminate stack 10' in FIG. 5a; or a loop 32 or fold 33 in a
plurality of ply layers, as indicated in laminate stack 10'' in
FIG. 5b; or a loop 34 extending through an entire laminate stack,
as indicated in laminate stack 10''' in FIG. 5c. As previously
explained in the background section, the uncontrolled development
of wrinkle within the laminate stack is disadvantageous because it
leads to reduced structural performance, less accurate surfaces,
non-uniformity of components and time consuming inspection,
correction and justification work.
[0051] In order to manage the development of wrinkle within the
laminate stack 10 during the moulding process, the tool 20 is
provided with a wrinkle control feature 21 on its moulding surface,
as shown in FIG. 6 and FIG. 4b. The wrinkle control feature 21 is
adapted to cooperate with the first surface 10a of the laminate
stack to produce a predictable surface feature 14 (a local surface
undulation in the nominal surface of the cured component) in the
first surface, shown in FIG. 7a and FIG. 7b. The development of the
surface feature acts to minimise the impact of wrinkle on the
second surface 10b, and to reduce uncontrolled wrinkle developing
at the first surface. The wrinkle control feature is also adapted
to minimise its own effect on the optimisation of the design shape
of the component, and to minimise its own effect and that of the
wrinkle on the shape of the second surface 10b.
[0052] The wrinkle control feature 21 is a recess 22 which
cooperates with the laminate stack during the moulding process, and
is adapted to accommodate excess material from the laminate stack.
As can be seen from FIG. 6, the width and height of the wrinkle
control feature varies across its extent, and the recess is a
substantially dart or arrowhead shaped indentation extending from
adjacent an edge of the moulding surface of the tool 20 towards a
corner 23 of the tool. The arrow head shaped recess 22 tapers in
dimensions towards the corner 23. The recess may extend to the
corner 23 or may alternatively extend part of the way from the edge
of the moulding surface towards the corner as required.
[0053] In alternative embodiment, the wrinkle control feature may
not be arrowhead shaped but may be some other shape. Several
alternative shapes for wrinkle control features 21', 21'', 21'''
and 21''' are shown adjacent each other on a tool 20' in FIG. 6b.
Wrinkle control feature 21' is arrow head shaped and extends part
of the way from the edge of the moulding surface of the tool 20' to
the corner 23. Wrinkle control feature 21'' is generally elliptical
and has curved sides and a curved tip. Wrinkle control feature
21''' is trapezoidal and has a flat tip. Wrinkle control feature
21'''' is rectangular in shape. The alternative wrinkle control
feature designs of 6b are just some of the possible alternative
designs to the arrow head shaped feature previously described and
are given as non-limiting examples.
[0054] The optimum geometry and location of the wrinkle control
feature in a function of the shape of the moulding surface of the
tool and the materials used to form the component. The optimum
type, shape, dimensions and location of a wrinkle control feature
may, therefore, vary significantly depending on the component being
formed. For each specific component design, the optimum wrinkle
control feature geometry and location may be determined by
simulation or by trial and error. In this way, the wrinkle control
feature may be optimised separately for each application to achieve
the most effective control of the development of wrinkle across a
range of composite components.
[0055] When the laminate stack 10 is arranged on the tool 20, as
shown in FIG. 3d, and the laminate stack 10 conforms around corner
23, some regions of the laminate stack experience a contraction due
to the complex, 3-dimensional nature of the tool. Because the
fibrous ply layers 9 have minimal ability to contract, the ply
layers tend to buckle and form wrinkles initiated by the wrinkle
control feature 21 adjacent the first surface 10a.
[0056] Excess material from some of the ply layers 9 at or near the
first surface 10a is received by the recess 22, so that a
controlled surface feature 14 is generated at the first surface, as
shown in FIG. 7b. The surface feature 14 is a predictable wrinkle
which is initiated at a predictable location defined by the wrinkle
control feature 21. The induced wrinkle may be contained entirely
within the recess 22, or extend out from the wrinkle control
feature 21 at which it is induced.
[0057] In an alternative embodiment, instead of inducing a wrinkle,
the wrinkle control feature 21 may be adapted to provide an
increased path length over a region of the moulding surface for at
least one of the ply layers adjacent the first surface sufficient
to prevent wrinkle altogether. In this case, when the ply layers 9
adjacent the first surface 10a begin to contract, the additional
path length provided on the moulding surface of the tool 20
accommodates the excess material in the ply layers adjacent the
first surface to reduce or prevent wrinkle
[0058] By accommodating excess material from one or more ply layers
adjacent the first surface 10a and forming a surface feature or
induced wrinkle at or near the wrinkle control feature 21 provided
on the tool 20, the wrinkle control feature acts to prevent or
reduce wrinkle in the laminate stack 10 in regions remote from the
wrinkle control feature. In this way, the extent and location of
wrinkle within the component 10' may be managed. The management of
wrinkle includes reducing the extent of wrinkle and controlling its
location so that wrinkle can be reduced or prevented in regions in
which it is particularly desirable to achieve an accurate,
predetermined surface, for example datum surfaces of the spar 5 for
mounting other components including upper and lower wing covers 7,
8 and ribs.
[0059] The tool 20 may be used to form a plurality of spars 5. Each
of the spars 5 has a predictable surface feature 14 produced by the
wrinkle control feature 21, and the surface features of the spars 5
are all substantially identical. In addition, the generation of the
surface features 14 acts to manage the development of wrinkle in
the laminate stacks of spars 5 as each of the spars are formed, so
that the spars each benefit from the positive effects of managing
wrinkle as described above. Because the managed development of
wrinkle in the spars 5 is predictable, the spars are more similar
to each other than a group of spars formed on an equivalent tool
without a wrinkle control feature, which would experience
un-managed and unpredictable wrinkle In this way, the invention
also enables a plurality of spars 5 to be formed having minimal
variation between the spars.
[0060] In an alternative embodiment, a tool 40 for forming a spar
which is substantially similar to the spar 5 previously described
may be provided with a wrinkle control feature 41 comprising two
recesses 42 adjacent each other, as shown in FIG. 8a. The multiple
adjacent recesses of such an arrangement act similarly to the
wrinkle control feature previously described but produce a
plurality of surface features and therefore more extensive local
surface undulation with respect to the nominal surface of the
laminate component. By using multiple recesses, the amount of
excess material accommodated by the wrinkle control feature may be
increased, or the required extent of each of the recesses may be
reduced. By using multiple, smaller recesses 42 in the place of the
single larger recess 22 previously discussed, the effect of the
wrinkle control feature of the shape of the spar 5 is minimised,
because the extent of the surface features produced is reduced.
[0061] In an alternative embodiment, a tool 40' for forming a spar
which is substantially similar to the spar 5 previously described
may be provided with a wrinkle control feature 41' comprising more
than two recesses 42 adjacent each other, as shown in FIG. 8b,
providing similar benefits to the embodiment shown in FIG. 8a.
[0062] In an alternative embodiment, a tool 40'' for forming a spar
which is substantially similar to the spar 5 previously described
may be provided with a wrinkle control feature 41'' comprising a
protrusion 43 or a control feature 41''' comprising a protrusion
and 43 and a recess 42, as shown in FIG. 8c. The protrusion 43 acts
to initiate a predictable, controlled wrinkle at a location defined
by the wrinkle control feature 41' which acts to manage the
development of wrinkle in the laminate stack of the spar.
[0063] Rear spar 6 may equally be formed using a tool having a
wrinkle control feature or wrinkle control features as described
above. Rear spar 6 may, like spar 5, be a straight spar, or
alternatively may comprise a kink or bend.
[0064] Any number of wrinkle control features, each comprising a
recess or recesses and/or a protrusion or protrusions may be
provided on the tool.
[0065] In the embodiments described above, the wrinkle control
feature is provided on the moulding surface of a male tool.
However, in another embodiment, a wrinkle control feature may be
provided on the moulding surface of a female tool. A wrinkle
control feature provided on a female tool may be adapted to control
the development of wrinkle in the same way as any of the
embodiments already described.
[0066] In the embodiments described above, the ply layers are laid
up to form a ply stack which is then arranged on the tool. However,
in another embodiment, the ply layers may be arranged on the tool
sequentially, so that the ply stack is assembled on the tool. The
laminate stack or individual ply layers may be arranged on the tool
by hand or in an automated or semi-automated process.
[0067] Although the invention has been described above with
reference to one or more preferred embodiments, it will be
appreciated that various changes or modifications may be made
without departing from the scope of the invention as defined in the
appended claims.
* * * * *