A co-curing forming process method of a C-type PMI foam sandwich structure composite material

Abstract

The application discloses a kind of C-type PMI foam sandwich structure composite material co-curing forming process method, including PMI foam machine adds, PMI foam drying, sheet positioning and pasting, PMI foam adaptation, encapsulation and curing and the like steps.Inside and outside layer foam are all circular arc concave structure, first convex surface machine adds, then 180 ° overturns positioning concave surface machine adds;Foam is wrapped with air-permeable felt when drying, and air-permeable felt edge is fixed with pressure-sensitive tape;Prepreg, foam positioning and pasting are carried out with the aid of laser projector, and removable calibration film is used to assist adaptation during the period.The forming process of the application is simple, high in operability, low in manufacturing cost, and has important engineering application significance.The forming process of the application can ensure high integrity of foam under pressure, high accuracy of inside and outside layer foam position, high adhesion of prepreg and foam, and the quality of the formed radome is good, and the whole meets the design requirements of high strength and high wave transmission.

Description

Technical Field

[0001] This invention relates to the field of composite material co-curing molding technology, and in particular to a co-curing molding process for a C-type PMI foam sandwich structure composite material. Background Technology

[0002] The rapid development of avionics airborne communication technology has placed higher demands on its supporting aviation equipment. Airborne satellite communication radomes require lightweight, high strength, and high wave transmission. Sandwich structures, due to their high specific strength, high specific modulus, and fatigue resistance, are often used as important structural materials in engineering applications. Considering wave transmission performance requirements, PMI foam is often used as the core material for radomes. The sandwich structure of the radome contains many dielectric interfaces and is composed of different types of materials, mainly distinguished by the letters A, B, and C.

[0003] Traditional sandwich radomes are mostly A-layer structures, often employing a co-bonding molding process. This involves molding the skin separately and then bonding it to the core material with adhesive. In this process, the interface conformity between the cured skin and the core material, as well as the bonding pressure parameters, can significantly impact the bonding quality, thus affecting the radome's structural strength, wave transmission performance, and other properties, resulting in a shorter service life. Furthermore, the process is complex, time-consuming, and costly. Therefore, it is necessary to explore a co-curing molding process for C-type multi-layer structures. Summary of the Invention

[0004] The purpose of this invention is to provide a co-curing molding process for C-type PMI foam sandwich structure composite materials to solve the defects in the molding of A-type sandwich structure radomes.

[0005] To address the aforementioned technical problems, this invention provides a co-curing molding process for C-type PMI foam sandwich structure composite materials, comprising the following steps:

[0006] Step A: PMI foam layer pre-processing. The convex surfaces of the outer and inner foam layers and the flipping positioning reference edge are pre-processed using machining equipment, so that the processed outer and inner foam layers can be flipped 180° according to the flipping positioning reference edge, and the concave surface can be processed with the help of a female die cutting and drilling tool.

[0007] Step B: Drying the PMI foam layer. First, clean the processed outer and inner foam layers, then wrap them with breathable felt and dry them.

[0008] Step C: Positioning and laying of the sheet material. During the preparation of the PMI foam layer, the antenna radome female mold forming fixture is cleaned simultaneously. After cleaning, starting from the bottom of the antenna radome female mold forming fixture, the outer skin, outer foam, middle skin, inner foam and inner skin are laid in sequence, and adhesive film is laid between the layers for connection.

[0009] Step D: PMI foam layer adaptation. The outer and inner foam layers are adapted before formal installation. A verification mold is placed on the surface of the foam concave adhesive film. The foam that has been cleaned and dried in step B is positioned and pre-compacted using a laser projector. When the verification mold meets the following three characteristics: complete compaction, foam texture appears in all areas of the surface, and the foam texture does not exceed the three characteristics of the foam laser projection area, the foam and the material sheet are highly fitted and accurately positioned without slippage. After the adaptation is completed, the verification mold is removed and the foam is formally installed.

[0010] Step E: Encapsulation and curing. Place the release film, breathable felt and vacuum bag on the surface of the parts that have been laid in step C for encapsulation and vacuum to keep them sealed. Send the encapsulated parts and tooling into an autoclave for curing and shaping.

[0011] Preferably, in step A, in addition to processing the convex surface, the PMI foam layer preprocessing process also requires processing the flipping positioning reference edge, which serves as the positioning reference for the 180° flipping of the outer or inner foam layer and the processing of the concave surface.

[0012] Preferably, in step B, the drying temperature of the outer foam and the inner foam is 60℃~130℃, the heat preservation time is 120min~180min, and the drying method is to wrap them with breathable felt and fix the edges with pressure-sensitive tape to avoid heat deformation of the foam.

[0013] Preferably, in step C, during the positioning and laying of the sheet material, venting material is placed in the spare area of ​​the part every 1 to 3 layers, and pre-compaction is performed every 1 to 3 layers. The pre-compaction vacuum degree is ≥-90kpa and the time is ≥15min.

[0014] Preferably, the size of the verification mold used in step D is larger than the adhesive film and can be removed.

[0015] Preferably, in step D, the pre-compaction vacuum degree of foam adaptation is ≥-90kPa and the time is ≥15min; the adaptation is completed when the verification film is completely compacted, foam patterns appear in all areas of the surface, and the foam patterns do not exceed the foam laser projection area.

[0016] Preferably, in step E, the sealing and leak testing vacuum is -80 kPa to -95 kPa, the curing parameters are atmospheric pressure, curing pressure is 300 kPa to 500 kPa, curing temperature is 120℃ to 180℃, and the holding time is 90 min to 180 min.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. The molding process of this invention can ensure high integrity of the foam under pressure, high accuracy of the inner and outer foam positions, and high adhesion between the foam and the prepreg.

[0019] 2. The radome formed using the molding process of this invention has good quality and meets the design requirements of high strength and high wave transmission as a whole;

[0020] 3. The molding process of this invention is simple, highly operable, and has low manufacturing cost, making it of significant engineering application value. Attached Figure Description

[0021] Figure 1 This is a sheet laying diagram of the C-type PMI foam sandwich structure composite material co-cured and molded according to the present invention;

[0022] Figure 2 This is the foam layer adaptation and laying diagram provided by the present invention.

[0023] In the diagram: 1. Antenna radome female mold forming fixture; 2. Outer skin; 3. Adhesive film; 4. Outer foam layer; 5. Middle skin layer; 6. Inner foam layer; 7. Inner skin layer; 8. Verification mold. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0025] In the description of this invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] In addition, the features, operations, and characteristics described in the specification can be combined in any suitable manner to form various embodiments. Similarly, the steps or actions described in the method can be rearranged in a manner that is readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the purpose of clearly describing a particular embodiment and are not necessarily required orders, unless otherwise stated that a particular order must be followed. Example

[0028] This invention provides a co-curing molding process for C-type PMI foam sandwich structure composite materials, comprising the following steps:

[0029] Step A: PMI foam layer pre-processing. The convex surfaces of the outer foam 4 and inner foam 6 and the flipping positioning reference edge are pre-processed by machining equipment, so that the processed outer foam 4 and inner foam 6 can be flipped 180° according to the flipping positioning reference edge, and the concave surface is processed with the help of the female die cutting and drilling tool.

[0030] Step B: Drying the PMI foam layer. First, clean the processed outer foam 4 and inner foam 6, then wrap them with breathable felt and dry them.

[0031] Step C: Positioning and laying the sheet materials, such as... Figure 1 As shown, during the preparation of the PMI foam layer, the antenna radome female mold forming fixture 1 is cleaned simultaneously; after cleaning, starting from the bottom of the antenna radome female mold forming fixture 1, the outer skin 2, outer foam 4, middle skin 5, inner foam 6 and inner skin 7 are laid in sequence, and adhesive film 3 is laid between the layers for connection.

[0032] Step D: PMI foam layer adaptation, such as Figure 2 As shown, the outer foam 4 and inner foam 6 are pre-fitted before formal installation. A verification mold 8 is placed on the surface of the adhesive film 3 on the concave side of the foam. The foam that has been cleaned and dried in step B is positioned and pre-compacted with the help of a laser projector. When the verification film 8 meets the three characteristics of being fully compacted, having foam texture in all areas of the surface, and the foam texture not exceeding the area of ​​the foam laser projection, the foam and the material sheet are highly fitted and the position is accurate without slippage. After the fitting is completed, the verification film 8 is removed and the foam is formally installed.

[0033] Step E: Encapsulation and curing. Place the release film, breathable felt and vacuum bag on the surface of the parts that have been laid in step C for encapsulation and vacuum to keep them sealed. Send the encapsulated parts and tooling into an autoclave for curing and shaping.

[0034] Specifically, in step A, in addition to processing the convex surface, the PMI foam layer preprocessing process also requires processing the flipping positioning reference edge, which serves as the positioning reference for the 180° flipping of the outer foam 4 or the inner foam 6 and the processing of the concave surface.

[0035] Specifically, in step B, the drying temperature of the outer foam 4 and the inner foam 6 is 60℃~130℃, the heat preservation time is 120min~180min, and the drying method is to wrap them with breathable felt and fix the edges with pressure-sensitive tape to avoid heat deformation of the foam.

[0036] Specifically, in step C, during the positioning and laying of the sheet material, venting material is placed in the spare area of ​​the part every 1 to 3 layers, and pre-compaction is performed every 1 to 3 layers. The pre-compaction vacuum degree is ≥-90kpa and the time is ≥15min.

[0037] Specifically, the verification mold 8 used in step D is larger than the adhesive film 3 and is removable.

[0038] Furthermore, the pre-compaction vacuum degree of the foam adapter is ≥-90kPa, and the time is ≥15min; the adapter is completed when the verification membrane 8 is completely compacted, foam patterns appear in all areas of the surface, and the foam patterns do not exceed the foam laser projection area.

[0039] Specifically, in step E, the sealing and leak testing vacuum is -80kpa to -95kpa, the curing parameters are atmospheric pressure, curing pressure is 300kpa to 500kpa, curing temperature is 120℃ to 180℃, and the holding time is 90min to 180min.

[0040] The molding process of this invention is simple, highly operable, and low in manufacturing cost, and has significant engineering application value. The molding process of this invention can ensure the high integrity of the foam under pressure, the high accuracy of the inner and outer foam positions, the high degree of adhesion between the foam and the prepreg, and the good quality of the molded radome, which meets the design requirements of high strength and high wave transmission.

[0041] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A process for co-curing of a sandwich structure of C-PMI foam composite material, characterized in that, Comprising the following steps: Step A: PMI foam layer pre-processing, pre-processing the convex surface of the outer foam (4) and the inner foam (6) and the turning positioning reference edge by machining equipment, for subsequent 180° turning of the processed outer foam (4) and inner foam (6) according to the turning positioning reference edge, and processing the concave surface by means of a negative mold cutting drilling tool; Step B: PMI foam layer drying, first clean the processed outer foam (4) and inner foam (6), then wrap them with air-permeable felt and dry them; Step C: Material positioning and laying, clean the radome negative mold forming tool (1) during the preparation of the PMI foam layer; after cleaning, lay the outer skin (2), outer foam (4), middle skin (5), inner foam (6) and inner skin (7) in turn from the bottom of the radome negative mold forming tool (1), and lay adhesive film (3) between the layers for connection; Step D: PMI foam layer adaptation, the outer foam (4) and the inner foam (6) are pre-adapted before formal laying, a layer of verification film (8) is placed on the adhesive film (3) surface of the foam concave surface, and the cleaned and dried foam in step B is positioned and laid by means of a laser projector and pre-compacted, when the verification film (8) meets the three characteristics of complete compaction, all areas on the surface appearing foam lines, and foam lines not exceeding the foam laser projection area, the foam is highly attached to the material and the position is accurate without slipping, after the adaptation is completed, the verification film (8) is removed, and the foam is formally laid; Step E: Encapsulation and curing, the surface of the part laid in step C is sequentially placed with a release film, air-permeable felt and a vacuum bag for encapsulation and vacuum holding, and the encapsulated part and tooling are sent into a hot press tank for curing and forming.

2. A co-forming process method of a C-PMI foam sandwich structure composite material according to claim 1, wherein, In step A, in addition to processing the convex surface, the turning positioning reference edge needs to be processed during the pre-processing of the PMI foam layer, which serves as the positioning reference for the 180° turning of the outer foam (4) or the inner foam (6) and the processing of the concave surface.

3. A co-forming process for C-PMI foam sandwich structure composites as claimed in claim 1, wherein, In step B, the drying temperature of the outer foam (4) and the inner foam (6) is 60℃~130℃, the holding time is 120min~180min, the drying method is to wrap with air-permeable felt and fix the edge with pressure-sensitive tape to avoid foam thermal deformation.

4. A co-forming process for C-PMI foam sandwich structure composites as claimed in claim 1, wherein, In step C, during the material positioning and laying, exhaust material is placed every 1~3 layers in the part excess area, and pre-compaction is performed every 1~3 layers, with a pre-compaction vacuum degree of ≥-90kpa and a time of ≥15min.

5. A co-forming process for C-PMI foam sandwich structure composite materials as claimed in claim 1, wherein, The verification film (8) used in step D is larger in size than the adhesive film (3) and can be removed.

6. A co-forming process for C-PMI foam sandwich structure composites as recited in claim 1, wherein, In step D, the pre-compaction vacuum degree of the foam adaptation is ≥-90kpa, and the time is ≥15min; when the verification film (8) is completely compacted, all areas on the surface appear foam lines, and the foam lines do not exceed the foam laser projection area, the adaptation is completed.

7. A co-forming process for C-PMI foam sandwich structure composites as claimed in claim 1, wherein, In step E, the encapsulation leak detection vacuum is-80kpa~-95kpa, the curing parameters are atmospheric, the curing pressure is 300kpa~500kpa, the curing temperature is 120℃~180℃, and the holding time is 90min~180min.

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