Patent Description:
Composite materials have been widely applied in the aerospace field because of their advantages such as high specific stiffness, ease of design and integral molding. In the field of aircraft, composite materials have been used to manufacture main force-bearing components such as wing skins (also known as wing panels), fuselages, horizontal stabilizers, ailerons, vertical tails, sidewall panels, bulkheads, wing ribs. Among them, wall panels have been widely used in the main force-bearing structure of the fuselage. The bonding area between the stringers and the skin in the U-shaped panel is larger than that in the T-shaped panel, which directly affects the bonding quality of the entire wall panel structure. In addition, with the existing preforming and process method the dimensional tolerance of the wall panel is difficult to be guaranteed, and so the positioning accuracy of the stringers do not meet the requirement. Further relevant technologies are discussed in the patent application publications: <CIT>, <CIT>, and <CIT>.

The claimed invention provides a manufacturing method of a U-shaped stringer fabricated preformed structure as defined in the attached independent claim <NUM>. The manufacturing method improves the efficiency of laying a U-shaped prepreg layer on a skin layer, reduces the manufacturing cost of the mold, improves the corner quality of the stringer, ensures the product quality and precision, and simplifies the technological process. Further improvements are provided in the dependent claims.

The claimed invention provides also a manufacturing method of a U-shaped stringer wall panel structure. The manufacturing method improves the efficiency of laying a U-shaped prepreg layer on a skin layer, reduces the manufacturing cost of the mold, improves the corner quality of the stringer, ensures the product quality and precision, and simplifies the technological process.

One embodiment provides a manufacturing method of a U-shaped stringer fabricated preformed structure. The method adopts a mold for preforming of the U-shaped stringer. The mold includes a base, a rigid mold and an elastic mold. The rigid mold is detachably arranged on the base. The rigid mold is of a U-shaped structure, and is wrapped around the three adjacent external sidewall surfaces of the base. The elastic mold is arranged on the rigid mold. The elastic mold is of a U-shaped structure, and is wrapped on the external sidewall surface of the rigid mold.

The rigid mold is installed on the base.

A multi-layer structure is laid on the rigid mold, and the multi-layer structure is cured and milled to form the elastic mold having a U-shaped structure.

A prepreg layer is laid on the elastic mold, a U-shaped prepreg layer is formed by performing vacuum preloading on the prepreg layer, and a U-shaped stringer preformed structure is formed by the base, the rigid mold, the elastic mold and the U-shaped prepreg layer.

Multiple U-shaped stringer preformed structures are distributed in a horizontal direction, and an intermediate interlayer is disposed between two adj acent U-shaped stringer preformed structures.

One embodiment provides a manufacturing method of a U-shaped stringer wall panel structure. a U-shaped stringer fabricated preformed structure is manufactured using the manufacturing method of a U-shaped stringer fabricated preformed structure described above.

The base is removed from the U-shaped stringer fabricated preformed structure.

A skin tooling laid with a skin layer is placed in the horizontal direction.

The U-shaped stringer fabricated preformed structure in which the base is removed is rotated <NUM> degrees and then placed on the skin layer.

Vacuum packaging is performed on the U-shaped prepreg layer and the skin layer, and the U-shaped prepreg layer and the skin layer are co-cured or co-bound and molded at a given temperature and pressure.

The skin tooling, multiple rigid molds and multiple elastic molds are removed.

The mold for preforming of a U-shaped stringer in the embodiments will be described below with reference to <FIG>.

The mold for preforming of the U-shaped stringer includes a base <NUM>, a rigid mold <NUM> and an elastic mold <NUM>. The rigid mold <NUM> is detachably arranged on the base <NUM>. The rigid mold <NUM> is of a U-shaped structure, and is wrapped on the three adjacent external sidewall surfaces of the base <NUM>. The elastic mold <NUM> is arranged on the rigid mold <NUM>. The elastic mold <NUM> is of a U-shaped structure, and is wrapped on the external sidewall surface of the rigid mold <NUM>.

The mold for preforming of the U-shaped stringer is an important basis for manufacturing the U-shaped stringer wall panel structure. The mold reduces the manufacturing cost of the mold, indirectly improves the efficiency of laying the U-shaped prepreg layer <NUM> on the skin layer <NUM>, improves the corner quality of the stringer, ensures the product quality and precision, and simplifies the technological process.

The rigid mold <NUM> is of a U-shaped structure, which ensures the positioning and longitudinal collimation of the stringer. The elastic mold <NUM> is of a U-shaped structure, and its thermal expansion ensures the effective transmission of the normal pressure on fiber layers at the corners and the triangular areas of the U-shaped stringer, avoiding defects such as fiber delamination and voids caused by failure of full pressure transmission and ensuring the quality of the U-shaped stringer wall panel structure. Exemplarily, the elastic mold <NUM> adopts the structure form of AIRPAD rubber sheet + prepreg layer + AIRPAD rubber sheet. In some embodiments, the elastic mold <NUM> can select other structure forms according to specific requirements.

Optionally, the base <NUM> includes a bottom portion <NUM> and a raised portion <NUM>. The raised portion <NUM> is connected to the bottom portion <NUM>. The rigid mold <NUM> is wrapped on the external sidewall surface of the raised portion <NUM> and two opposite external sidewall surfaces of the bottom portion <NUM>. The raised portion <NUM> has a width gradually decreased in a direction away from the bottom portion11.

Exemplarily, since the raised portion <NUM> has the width gradually decreased in the direction away from the bottom portion11, it can be known that the raised portion <NUM> has a ladder structure having a narrow top and a wide bottom, which facilitates the operator to remove the rigid mold <NUM> from the base <NUM>. In addition, the bottom portion <NUM> and the raised portion <NUM> may be integrally formed, or can be fixedly connected by welding, bonding or other methods.

Optionally, one of the base <NUM> and the rigid mold <NUM> is provided with a clamping slot, and the other is provided with a clamping protrusion <NUM> matching the clamping slot.

Exemplarily, the base <NUM> and the rigid mold <NUM> are provided with matching connectors of the clamping slot and the clamping protrusion <NUM>, so that the stability of the rigid mold <NUM> placed on the base <NUM> is improved and the rigid mold <NUM> is not easy to loosen, thereby improving the product quality and precision. In other embodiments, the connection between the base <NUM> and the rigid mold <NUM> is not limited to the matching manner of the clamping slot and the clamping protrusion <NUM>, and the connection manner can be selected according to specific conditions.

Optionally, external sidewall corners of the rigid mold <NUM> are arc-shaped. Optionally, the external sidewall corners of the rigid mold <NUM> are arc-shaped, which ensures the positioning and longitudinal collimation of the stringer.

Optionally, inner sidewall corners and external sidewall corners of the elastic mold <NUM> are arc-shaped. In this embodiment, inner sidewall corners and external sidewall corners of the elastic mold <NUM> are arc-shaped, which ensures the effective transmission of the applied pressure on the stringer structure during the curing process, and effectively reduces the stress concentration at corners of the U-shaped prepreg layer <NUM>, thereby avoiding the defects on the U-shaped prepreg layer <NUM> such as the delamination and voids, and ensuring the quality of the U-shaped stringer wall panel structure.

The manufacturing method of a U-shaped stringer fabricated preformed structure in the embodiments is described in accordance with <FIG> and <FIG>.

The manufacturing method of the U-shaped stringer fabricated preformed structure adopts the mold for preforming of the U-shaped stringer, and includes the following steps.

In S1, the rigid mold <NUM> is installed on the base <NUM>.

In S2, a multi-layer structure is laid on the rigid mold <NUM>, and the multi-layer structure is cured and milled to form the elastic mold <NUM> having a U-shaped structure.

In S3, a prepreg layer is laid on the elastic mold <NUM>, a U-shaped prepreg layer <NUM> is formed by performing vacuum preloading on the prepreg layer, and a U-shaped stringer preformed structure is formed by the base <NUM>, the rigid mold <NUM>, the elastic mold <NUM> and the U-shaped prepreg layer <NUM>.

In S4, multiple U-shaped stringer preformed structures are distributed in a horizontal direction, and an intermediate interlayer <NUM> is disposed between two adjacent U-shaped stringer preformed structures.

In this embodiment, the manufacturing method of a U-shaped stringer fabricated preformed structure improves the efficiency of laying the U-shaped prepreg layer <NUM> on the skin layer <NUM>, reduces the manufacturing cost of the mold, improves the corner quality of the stringer, ensures the product quality and precision, and simplifies the technological process. The step that multiple U-shaped stringer preformed structures are distributed in a horizontal direction and an intermediate interlayer <NUM> is disposed between two adjacent U-shaped stringer preformed structures in S4 facilitates positioning, makes stringer axis and straightness to be easily ensured, and improves the product quality and precision. In addition, the multi-layer structure in S2 can be a structure of AIRPAD rubber sheet + prepreg layer + AIRPAD rubber sheet.

Compared with the related art, the manufacturing method has the following beneficial effects: the rigid mold <NUM> is installed on the base <NUM>; a multi-layer structure is laid on the rigid mold <NUM>, and the multi-layer structure is cured and milled to form the elastic mold <NUM> having a U-shaped structure; a prepreg layer is laid on the elastic mold <NUM>, a U-shaped prepreg layer <NUM> is formed by performing vacuum preloading on the prepreg layer, and in this case, a U-shaped stringer preformed structure is formed by the base <NUM>, the rigid mold <NUM>, the elastic mold <NUM> and the U-shaped prepreg layer <NUM>; and multiple U-shaped stringer preformed structures are distributed in a horizontal direction, and an intermediate interlayer <NUM> is disposed between two adjacent U-shaped stringer preformed structures. The manufacturing method of the U-shaped stringer fabricated preformed structure improves the efficiency of laying the U-shaped prepreg layer <NUM> on the skin layer <NUM>, reduces the manufacturing cost of the mold, improves the corner quality of the stringer, ensures the product quality and precision, and simplifies the technological process.

Advantageously, the U-shaped prepreg layer <NUM> is a composite material. The composite material has the advantages of high stiffness, ease of design, and easy of integral molding.

Optionally, in S4, each intermediate interlayer <NUM> is fixedly connect every two U-shaped prepreg layers <NUM>. Exemplarily, since the U-shaped prepreg layer <NUM> is cured, if two adjacent U-shaped prepreg layers <NUM> are directly bonded, the connection of the two U-shaped prepreg layers <NUM> are unstable. The intermediate interlayer <NUM> is used as a medium to connect the two U-shaped prepreg layers <NUM>, ensuring the connection stability of the two U-shaped prepreg layers <NUM>. Each of intermediate interlayers <NUM> in multiple U-shaped prepreg layers <NUM> is fixedly connected to two U-shaped prepreg layers <NUM>, which facilitates the subsequent operation for positioning multiple U-shaped prepreg layers <NUM> and other components, so that it is unnecessary to position each U-shaped prepreg layer <NUM> separately, thereby improving the positioning precision and efficiency.

Optionally, bottom surfaces of the bases <NUM> of the multiple U-shaped stringer preformed structures are coplanar, which facilitates positioning, makes stringer axis and straightness to be easily ensured, and improves the product quality and precision.

Optionally, there is a gap between each U-shaped prepreg layer <NUM> and the intermediate interlayer <NUM>, and the gap is filled with a filler <NUM>. In this embodiment, the filler <NUM> is filled in the gap between the U-shaped prepreg layer <NUM> and the intermediate interlayer <NUM> and fully compacted, which effectively transfers the applied pressure, controls the defects such as delamination and voids, and ensures the dimensional precision and product quality. Generally, the filler <NUM> is spill strips, and in other embodiments of the present application, the filler <NUM> will not be limited to spill strips and may be selected according to specific requirements.

The manufacturing method of a U-shaped stringer wall panel structure in the embodiment is described in accordance with <FIG>,<FIG> and <FIG>.

The manufacturing method of the U-shaped stringer wall panel structure includes the following steps.

In Q1, the base <NUM> is removed from the U-shaped stringer fabricated preformed structure.

In Q2, a skin tooling <NUM> laid with the skin layer <NUM> is placed in the horizontal direction.

In Q3, the U-shaped stringer fabricated preformed structure in which the base <NUM> is removed is rotated <NUM> degrees and then placed on the skin layer <NUM>.

In Q4, vacuum packaging is performed on the U-shaped prepreg layer <NUM> and the skin layer <NUM>, and the U-shaped prepreg layer <NUM> and the skin layer <NUM> are co-cured or co-bound and molded at a given temperature and pressure.

In Q5, the skin tooling <NUM>, multiple rigid molds <NUM> and multiple elastic molds <NUM> are removed.

In this embodiment, the base <NUM> is removed from the U-shaped stringer fabricated preformed structure, the skin tooling laid with the skin layer <NUM> is placed in the horizontal direction, the U-shaped stringer fabricated preformed structure in which the base <NUM> is removed is rotated <NUM> degrees and then placed on the skin layer <NUM>, vacuum packaging is performed on the U-shaped prepreg layer <NUM> and the skin layer <NUM>, the U-shaped prepreg layer <NUM> and the skin layer <NUM> are co-cured or co-bound and molded at a given temperature and pressure, the skin tooling <NUM>, the rigid mold <NUM> and the elastic mold <NUM> are removed, and finally the U-shaped stringer wall panel structure is obtained. The manufacturing method of the U-shaped stringer wall panel structure improves the efficiency of laying the U-shaped prepreg layer <NUM> on the skin layer <NUM>, reduces the manufacturing cost of the mold, improves the corner quality of the stringer, ensures the product quality and precision, and simplifies the technological process. In Q4, the U-shaped prepreg layer <NUM> and the skin layer <NUM> are completely laminated, their bounding area is relatively large, and the stability between the two is strong, which effectively avoids the debonding of the stringer and ensures the quality of the U-shaped stringer wall panel structure.

Exemplarily, the range of the given temperature is typically <NUM> to <NUM> and the range of the pressure is typically <NUM>,<NUM> kPa to <NUM>,<NUM> kPa (<NUM> to <NUM> standard atmosperic pressures). In other embodiments, ranges of the given temperature and pressure can be adjusted depending on specific conditions.

The manufacturing method of the U-shaped stringer wall panel structure of a specific embodiment is described below.

In a first step, the rigid mold <NUM> is installed on the base <NUM>.

In a second step, a multi-layer structure is laid on the rigid mold <NUM>, and the multi-layer structure is cured and milled to form the elastic mold <NUM> having a U-shaped structure.

In a third step, a prepreg layer is laid on the elastic mold <NUM>, a U-shaped prepreg layer <NUM> is formed by performing vacuum preloading on the prepreg layer, and a U-shaped stringer preformed structure is formed by the base <NUM>, the rigid mold <NUM>, the elastic mold <NUM> and the U-shaped prepreg layer <NUM>.

In a fourth step, multiple U-shaped stringer preformed structures are distributed in a horizontal direction, and an intermediate interlayer <NUM> is disposed between two adjacent U-shaped stringer preformed structures, in which each intermediate interlayer <NUM> is fixedly connect to every two U-shaped prepreg layers <NUM>, bottom surfaces of the bases <NUM> of multiple U-shaped stringer preformed structures arecoplanar, there is a gap between each U-shaped prepreg layer <NUM> and the intermediate interlayer <NUM>, and the gap is filled with spill strips, such that a U-shaped stringer fabricated preformed structure is formed.

In a fifth step, the base <NUM> is removed from the U-shaped stringer fabricated preformed structure.

In a sixth step, the skin tooling <NUM> laid with the skin layer <NUM> is placed in the horizontal direction.

In a seventh step, the U-shaped stringer fabricated preformed structure in which the base <NUM> is removed is rotated <NUM> degrees and then placed on the skin layer <NUM>.

In an eighth step, vacuum packaging is performed on the U-shaped prepreg layer <NUM> and the skin layer <NUM>, and the U-shaped prepreg layer <NUM> and the skin layer <NUM> are co-cured or co-bound and molded at a given temperature and pressure.

In a ninth step, the skin tooling <NUM>, multiple rigid molds <NUM> and multiple elastic molds <NUM> are removed.

In the description of the specification, the description of reference terms "an embodiment", "some embodiments" and the like means that a specific feature, structure, material, or characteristic described in connection with the embodiment or the example is included in at least one embodiment or example. In the specification, the illustrative description of the preceding terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any suitable manner in one or more embodiments or examples.

Furthermore, it is to be understood that orientations or position relations indicated by terms such as "upper", "lower", "left", "right", "vertical", and "horizontal" are orientations or position relations based on the drawings. These orientations or position relations are intended only to facilitate the description and simplify the description and not to indicate or imply that a device or element referred to must have such specific orientations or must be configured or operated in such specific orientations. Thus, these orientations or position relations are not to be construed as limiting.

Claim 1:
A manufacturing method of a U-shaped stringer fabricated preformed structure, the manufacturing method adopting a mold for preforming of a U-shaped stringer, wherein the mold for preforming of a U-shaped stringer comprises:
a base (<NUM>);
a rigid mold (<NUM>), detachably arranged on the base (<NUM>), the rigid mold (<NUM>) being of a U-shaped structure and wrapping around three adjacent external sidewall surfaces of the base (<NUM>); and
an elastic mold (<NUM>), arranged on the rigid mold (<NUM>), the elastic mold (<NUM>) being of a U-shaped structure and wrapping around external sidewall surfaces of the rigid mold (<NUM>);
and wherein manufacturing method of a U-shaped stringer fabricated preformed structure comprises:
installing the rigid mold (<NUM>) on the base (<NUM>);
laying a multi-layer structure on the rigid mold (<NUM>), and curing and milling the multi-layer structure to form the elastic mold (<NUM>) having a U-shaped structure;
laying a prepreg layer on the elastic mold (<NUM>), forming a U-shaped prepreg layer (<NUM>) by performing vacuum preloading on the prepreg layer, and forming a U-shaped stringer preformed structure by the base (<NUM>), the rigid mold (<NUM>), the elastic mold (<NUM>), and the U-shaped prepreg layer (<NUM>); and
distributing a plurality of U-shaped stringer preformed structures in a horizontal direction, and disposing an intermediate interlayer (<NUM>) between every two adjacent U-shaped stringer preformed structures.