Composite manufacturing method and tool

1 . A method for manufacturing a composite structure, the method comprising the following steps:

a) providing at least two partially cured fiber reinforced polymer (FRP) parts;

b) forming an ensemble by joining the at least two partially cured FRP parts by bringing into contact a first bonding portion of a first partially cured FRP part with a second bonding portion of a second partially cured FRP part;

c) providing a mold comprising a first mold part and a second mold part configured for coupling with each other, such that an inner chamber is defined when the first and second mold parts are coupled to each other, said inner chamber being configured to house the ensemble inside, wherein:

the first mold part is provided with a first pressing surface, and

the second mold part is provided with a second pressing surface, such that the first and second pressing surfaces are configured to be arranged facing each other when the first and second mold parts are coupled to each other;

d) coupling the first and second mold parts such that the ensemble is housed within the inner chamber defined by said first and second mold parts, providing at least two inflatable bellows, and controlling an internal pressure of each of the at least two inflatable bellows to adjust a pressure exerted on at least one of the first partially cured FRP part and the second partially cured FRP part by each of the at least two inflatable bellows, wherein:

the first pressing surface presses against the first bonding portion of the first partially cured FRP part,

the second pressing surface presses against the second bonding portion of the second partially cured FRP part,

such that a pressure exerted by the first and second pressing surfaces presses the first and second bonding portions against each other,

each of the at least two inflatable bellows are disposed in non-contracting relationship with one another,

and each of the at least two inflatable bellows exerts a different pressure on the at least one of the first partially cured FRP part and the second partially cured FRP part by differentiated control of the internal pressure of each of the at least two inflatable bellows, wherein a resilient caul is arranged between each of the inflatable bellows and the first or second bonding portion, such that each of the resilient cauls corresponds in size to a corresponding one of the at least two inflatable bellows;

e) producing a vacuum in the inner chamber; and

f) curing the ensemble under vacuum and temperature.

2 . The method according to claim 1 further comprising, before step a), manufacturing each partially cured FRP part by applying a partial curing cycle, wherein the partial curing cycle is performed:

at a lower temperature compared to a temperature required to complete a curing cycle according to which the partially cured FRP parts are completely cured, or

during a shorter time compared to a time required to complete a curing cycle according to which the partially cured FRP parts are completely cured, or

both.

3 . The method according to claim 1 , further comprising, before step b), performing a surface treatment on

the first bonding portion,

the second bonding portion, or

both.

4 . The method according to claim 3 , wherein the surface treatment is performed by at least one of the following methods:

plasma projection,

corona discharge,

grit blasting,

laser abrading,

any combination of these methods.

5 . The method according to claim 1 , wherein step b) comprises applying pressure to bring the first bonding portion and the second bonding portion into contact; and applying a partial curing cycle, wherein the partial curing cycle is performed:

at a lower temperature compared to a temperature adapted to complete a curing cycle according to which the partially cured FRP parts are completely cured,

during a shorter time compared to a time adapted to complete a curing cycle according to which the partially cured FRP parts are completely cured, or

both.

6 . The method according to claim 1 , wherein the vacuum in step e) is generated through at least one vacuum valve arranged on at least one of the first and second mold parts, wherein said vacuum valve establishes a fluidic communication between the inner chamber and an exterior of the first and second mold parts.

7 . The method according to claim 1 , wherein step e) comprises providing:

a vacuum bag covering, at least partially, a joint area between the first and second mold parts; and

sealing means configured to seal a connection between said vacuum bag and the first and second mold parts.

8 . The method according to claim 1 , wherein step f) comprises introducing the mold configured to house the ensemble in an oven.

9 . The method according to claim 1 , wherein step f) comprises heating by means of heating means integrated in the first or the second mold parts, or both.

10 . The method according to claim 1 , further comprising, after curing the ensemble according to step f), cooling down the ensemble.

11 . The method according to claim 1 ,

wherein the first partially cured FRP part is a substantially flat panel, and wherein the first mold part is provided with a pneumatic circuit configured to air-tightly communicate a vacuum system with the inner chamber through at least one vacuum valve, and

wherein, in step d) the substantially flat panel is arranged on the first mold part covering at least one vacuum valve; and

vacuum is applied through the vacuum valve, fixing the substantially flat panel to the first mold part by the suction generated.

12 . The method according to claim 11 ,

wherein the second partially cured FRP part is an omega-profile stringer configured to be joined to the substantially flat panel through two foot portions of the omega-profile stringer which are configured to contact two corresponding of the bonding portions of said substantially flat panel, such that a material-free enclosure is defined between the two foot portions of the omega-profile stringer, an inner side of the omega-profile stringer, and a portion of a surface of the substantially flat panel located between the two bonding portions contacting the foot portions of the omega-profile stringer;

wherein, in step d) the ensemble is arranged such that at least one vacuum valve is arranged contacting the portion of the substantially flat panel defined between the two bonding portions contacting the foot portions of the omega-profile stringer.

13 . A method for manufacturing a composite structure, the method comprising the following steps:

a) providing at least two partially cured fiber reinforced polymer (FRP) parts;

b) forming an ensemble by joining the at least two partially cured FRP parts by bringing into contact a first bonding portion of a first partially cured FRP part with a second bonding portion of a second partially cured FRP part, wherein the first partially cured FRP part is a substantially flat panel;

c) providing a mold comprising a first mold part and a second mold part configured for coupling with each other, such that an inner chamber is defined when the first and second mold parts are coupled to each other, said inner chamber being configured to house the ensemble inside, wherein:

the first mold part is provided with a first pressing surface,

the second mold part is provided with a second pressing surface, such that the first and second pressing surfaces are configured to be arranged facing each other when the first and second mold parts are coupled to each other, and

the first mold part is provided with a pneumatic circuit configured to air-tightly communicate a vacuum system with the inner chamber through at least one vacuum valve;

d) coupling the first and second mold parts such that the ensemble is housed within the inner chamber defined by said first and second mold parts, wherein:

the first pressing surface presses against the first bonding portion of the first partially cured FRP part,

the second pressing surface presses against the second bonding portion of the second partially cured FRP part, such that a pressure exerted by the first and second pressing surfaces presses the first and second bonding portions against each other,

the substantially flat panel is arranged on the first mold part covering at least one vacuum valve, and

vacuum is applied through the vacuum valve, fixing the substantially flat panel to the first mold part by the suction generated;

e) producing a vacuum in the inner chamber; and

f) curing the ensemble under vacuum and temperature.

14 . The method according to claim 1 , wherein each of the at least two inflatable bellows is in direct contact with either: the first pressing surface and the first bonding portion of the first partially cured FRP part, or the second pressing surface and the second bonding portion of the second partially cured FRP part.