Co-curing molding process method for C-type PMI foam sandwich structure composite material

Abstract

The invention discloses a co-curing molding process method for a C-type PMI foam sandwich structure composite material. The co-curing molding process method comprises the steps of PMI foam machining, PMI foam drying, material sheet positioning and paving, PMI foam matching, packaging and curing and the like. The inner-layer foam and the outer-layer foam are each of an arc inwards-concave structure, convex face machining is conducted firstly, and then 180-degree overturning positioning concave face machining is conducted; the air-permeable felt is wrapped when the foam is dried, and the edge of the air-permeable felt is fixed by pressure-sensitive adhesive tape; positioning paving of the prepreg and the foam is carried out by means of a laser projector, and a removable verification film is used for assisting in adaptation during the period. The forming technology is simple in technological process, high in operability and low in manufacturing cost and has important engineering application significance, high integrity of foam under the pressure effect and high fitting degree of the foam and the prepreg can be guaranteed through the forming technology, the positions of the foam on the inner layer and the foam on the outer layer are high in accuracy, the quality of the formed radome is good, and the service life of the radome is prolonged. And the design requirements of high strength and high wave transmission are integrally met.

Description

Technical Field

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

[0002] The rapid development of avionics airborne communication technology has put forward higher requirements for its supporting aviation equipment. Airborne satellite communication antenna covers are required to be light weight, high strength, and high wave transmittance. Sandwich structures are often used as important structural materials in engineering applications due to their high specific strength, high specific modulus, and fatigue resistance. Combined with the requirements for wave transmittance performance, PMI foam is often used as the core material of the antenna cover. The antenna cover sandwich structure contains many dielectric interfaces and is composed of different types of materials, which are mainly distinguished by letters A, B, and C.

[0003] Traditional sandwich structure radomes are mostly A-layer structures, and most of them adopt a co-bonding molding process, that is, the skin is molded separately, and then it is connected to the core material by gluing. In this process method, the surface fit of the cured skin and the core material bonding interface, the bonding pressure parameters, etc. are likely to have a significant impact on the bonding quality, thereby affecting the structural strength, wave transmission and other properties of the radome, resulting in a shorter service life. In addition, the process flow is complex, the cycle is long, and the manufacturing cost is high. Therefore, it is necessary to explore a co-curing molding process for C-type multi-sandwich structures. Summary of the invention

[0004] The object of the present invention is to provide a co-curing molding process method for a C-type PMI foam sandwich structure composite material to solve the defects of A-type sandwich structure antenna cover molding.

[0005] In order to solve the above technical problems, the present invention provides a co-curing molding process of a C-type PMI foam sandwich structure composite material, comprising the following steps: Step A: Pre-processing of the PMI foam layer, using machining equipment to process the convex surface of the outer foam layer and the inner foam layer and the turning positioning reference edge in advance, so that the outer foam layer and the inner foam layer that have been processed can be turned over 180 degrees according to the turning positioning reference edge, and the inner concave surface can be processed by using a female die cutting and drilling tooling; Step B: Drying the PMI foam layer. First, clean the processed outer foam and inner foam, then wrap them with breathable felt and dry them. Step C: Position and lay the sheet, and clean the radome female mold forming tooling simultaneously during the preparation of the PMI foam layer; after cleaning, lay the outer skin, outer foam, middle skin, inner foam and inner skin in sequence from the bottom of the radome female mold forming tooling, and lay adhesive films between the layers for connection; Step D: PMI foam layer adaptation. The outer foam and the inner foam are pre-adapted before formal paving. A calibration mold is placed on the film surface of the concave surface 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 calibration film meets the three characteristics of complete compaction, foam texture appears in all areas of the surface, and the foam texture does not exceed the foam laser projection area, the foam and the sheet are highly fitted and the position is accurate without slipping. After the adaptation is completed, the calibration film is removed and the foam is formally paved; Step E: Packaging and curing. In step C, the surface of the parts that have been laid is placed with an isolation film, a breathable felt and a vacuum bag in turn for packaging and evacuation to keep the seal. The packaged parts and tooling are sent to the autoclave for curing and molding.

[0006] Preferably, in step A, in addition to processing the convex surface, the PMI foam layer pre-processing also requires processing the flip positioning reference edge as a positioning reference for 180° flipping of the outer foam or inner foam and concave surface processing.

[0007] Preferably, in step B, the drying temperature of the outer foam and the inner foam is 60°C to 130°C, the insulation time is 120min to 180min, and the drying method is to wrap them with breathable felt and fix the edges with pressure-sensitive tape to avoid thermal deformation of the foam.

[0008] Preferably, in step C of positioning and paving the sheet, exhaust material is placed in the part margin area every 1 to 3 layers, and pre-compaction is performed every 1 to 3 layers, with the pre-compaction vacuum degree ≥-90 kPa and the time ≥15 min.

[0009] Preferably, the calibration mold used in step D is larger than the adhesive film and is removable.

[0010] Preferably, in step D, the foam adaptation pre-compaction vacuum degree is ≥-90kpa, and the time is ≥15min; the adaptation is completed when the verification film is completely compacted, foam lines appear in all areas of the surface, and the foam lines do not exceed the foam laser projection area.

[0011] Preferably, in step E, the packaging leak detection vacuum is -80 kpa to -95 kpa, the curing parameters are open to the atmosphere, the curing pressure is 300 kpa to 500 kpa, the curing temperature is 120° C. to 180° C., and the insulation time is 90 min to 180 min.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The molding process of the present invention can ensure the high integrity of the foam under pressure, the high accuracy of the positions of the inner and outer foam layers, and the high fit between the foam and the prepreg; 2. The antenna cover formed by the molding process of the present invention has good quality and meets the design requirements of high strength and high wave transmission as a whole; 3. The molding process of the present invention is simple, highly operable, and has low manufacturing cost, and has important engineering application significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a sheet laying diagram of the co-curing molding of the C-type PMI foam sandwich structure composite material provided by the present invention; Figure 2 The foam layer provided by the present invention is adapted to the paving pattern.

[0014] In the figure: 1. Radome female mold forming tooling; 2. Outer skin; 3. Adhesive film; 4. Outer foam; 5. Middle skin; 6. Inner foam; 7. Inner skin; 8. Calibration mold. DETAILED DESCRIPTION

[0015] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the drawings are in very simplified form and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0016] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0017] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0018] In addition, the features, operations, and characteristics described in the specification can be combined in any appropriate manner to form various embodiments. Similarly, the steps or actions described in the method can also be adjusted in order in a manner that can be easily seen by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for the purpose of describing a certain embodiment, and are not necessarily such sequences, unless otherwise stated that a certain sequence must be followed. Example

[0019] The present invention provides a co-curing molding process for a C-type PMI foam sandwich structure composite material, comprising the following steps: Step A: Pre-processing of the PMI foam layer, in which the convex surface of the outer foam layer 4 and the inner foam layer 6 and the turning positioning reference edge are processed by machining equipment in advance, so that the processed outer foam layer 4 and the inner foam layer 6 can be turned over 180 degrees according to the turning positioning reference edge, and the inner concave surface can be processed by using a female die cutting and drilling tool; 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; Step C: Position and lay the sheet, such as Figure 1 As shown, the antenna cover female mold forming tool 1 is cleaned synchronously during the preparation of the PMI foam layer; after the cleaning is completed, the outer skin 2, the outer foam 4, the middle skin 5, the inner foam 6 and the inner skin 7 are laid in sequence from the bottom of the antenna cover female mold forming tool 1, and the adhesive film 3 is laid between the layers for connection; Step D: PMI foam layer fit, such as Figure 2 As shown, the outer foam 4 and the inner foam 6 are pre-fitted before formal paving, and a layer of calibration mold 8 is placed on the surface of the adhesive film 3 on the concave surface of the foam. The foam that has been cleaned and dried in the paving step B is positioned with the help of a laser projector and pre-compacted. When the calibration film 8 meets the three characteristics of complete compaction, foam texture appears in all areas of the surface, and the foam texture does not exceed the foam laser projection area, the foam and the sheet are highly fitted and the position is accurate without slipping. After the adaptation is completed, the calibration film 8 is removed and the foam is formally paved; Step E: Packaging and curing. In step C, the surface of the parts that have been laid is placed with an isolation film, a breathable felt and a vacuum bag in turn for packaging and evacuation to keep the seal. The packaged parts and tooling are sent to the autoclave for curing and molding.

[0020] Specifically, in step A, in addition to processing the convex surface, the PMI foam layer pre-processing also needs to process the flip positioning reference edge as a positioning reference for 180° flipping of the outer foam layer 4 or the inner foam layer 6 and concave surface processing.

[0021] Specifically, in step B, the drying temperature of the outer foam 4 and the inner foam 6 is 60°C to 130°C, the insulation time is 120min to 180min, and the drying method is to wrap them with breathable felt and fix the edges with pressure-sensitive tape to avoid thermal deformation of the foam.

[0022] Specifically, in step C of positioning and laying the material sheets, exhaust material is placed in the part margin area every 1 to 3 layers, and pre-compacting is performed every 1 to 3 layers, with the pre-compacting vacuum degree ≥-90 kPa and the time ≥15 min.

[0023] Specifically, the verification mold 8 used in step D is larger than the adhesive film 3 and can be removed.

[0024] Furthermore, the foam is pre-compacted with a vacuum degree of ≥-90 kPa for ≥15 min; the adaptation is completed when the verification film 8 is fully compacted, foam lines appear in all areas of the surface, and the foam lines do not exceed the foam laser projection area.

[0025] Specifically, in step E, the packaging leak detection vacuum is -80kpa~-95kpa, the curing parameters are open to the atmosphere, the curing pressure is 300kpa~500kpa, the curing temperature is 120°C~180°C, and the insulation time is 90min~180min.

[0026] The molding process of the present invention is simple, highly operable, and has low manufacturing cost, and has important engineering application significance. The molding process of the present invention can ensure the high integrity of the foam under pressure, the high accuracy of the positions of the inner and outer layers of foam, the high fit between the foam and the prepreg, and the quality of the antenna cover after molding is good, and the overall design requirements of high strength and high wave transmission are met.

[0027] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A co-curing molding process for a C-type PMI foam sandwich structure composite material, characterized in that: The steps include: Step A: Pre-processing the PMI foam layer, in which the convex surface of the outer foam layer (4) and the inner foam layer (6) and the turning positioning reference edge are processed in advance by machining equipment, so that the processed outer foam layer (4) and the inner foam layer (6) can be turned over 180 degrees according to the turning positioning reference edge, and the inner concave surface can be processed by using a female die cutting and drilling tool; Step B: Drying the PMI foam layer, first cleaning the processed outer foam layer (4) and inner foam layer (6), then wrapping them with breathable felt and drying them; Step C: Positioning and laying the material pieces, while simultaneously cleaning the radome female mold forming tooling (1) during the preparation of the PMI foam layer; after the cleaning is completed, laying the outer skin (2), outer foam layer (4), middle skin (5), inner foam layer (6) and inner skin (7) in sequence from the bottom of the radome female mold forming tooling (1), and laying adhesive films (3) between the layers for connection; Step D: PMI foam layer adaptation. The outer foam layer (4) and the inner foam layer (6) are pre-adapted before formal paving. A layer of calibration mold (8) is placed on the surface of the adhesive film (3) on the concave surface 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 calibration film (8) meets the three characteristics of complete compaction, foam texture appears in all areas of the surface, and the foam texture does not exceed the foam laser projection area, the foam and the sheet are highly fitted and the position is accurate without slipping. After the adaptation is completed, the calibration film (8) is removed and the foam is formally paved. Step E: Packaging and curing. In step C, the surface of the parts that have been laid is placed with an isolation film, a breathable felt and a vacuum bag in turn for packaging and evacuation to keep the seal. The packaged parts and tooling are sent to the autoclave for curing and molding.

2. A co-curing molding process for a C-type PMI foam sandwich structure composite material according to claim 1, characterized in that: In step A, in addition to processing the convex surface, the PMI foam layer pre-processing also requires processing the flip positioning reference edge, which serves as a positioning reference for 180° flipping of the outer foam layer (4) or the inner foam layer (6) and concave surface processing.

3. A co-curing molding process for a C-type PMI foam sandwich structure composite material according to claim 1, characterized in that: In step B, the outer layer foam (4) and the inner layer foam (6) are dried at a temperature of 60°C to 130°C and a heat preservation time of 120 min to 180 min. The drying method is to wrap them with breathable felt and fix the edges with pressure-sensitive tape to prevent thermal deformation of the foam.

4. A co-curing molding process for a C-type PMI foam sandwich structure composite material according to claim 1, characterized in that: In step C, during the positioning and laying of the sheet, exhaust material is placed in the part margin area every 1 to 3 layers, and pre-compacting is performed every 1 to 3 layers. The pre-compacting vacuum degree is ≥-90 kPa, and the time is ≥15 min.

5. A co-curing molding process for a C-type PMI foam sandwich structure composite material according to claim 1, characterized in that: The calibration mold (8) used in step D is larger than the adhesive film (3) and can be removed.

6. A co-curing molding process for a C-type PMI foam sandwich structure composite material according to claim 1, characterized in that: In step D, the foam adaptation pre-compaction vacuum degree is ≥-90 kPa, and the time is ≥15 min. When the verification film (8) is completely compacted, foam lines appear in all areas of the surface, and the foam lines do not exceed the foam laser projection area, the adaptation is completed.

7. A co-curing molding process for a C-type PMI foam sandwich structure composite material according to claim 1, characterized in that: In step E, the packaging leak detection vacuum is -80kpa~-95kpa, the curing parameters are open to the atmosphere, the curing pressure is 300kpa~500kpa, the curing temperature is 120℃~180℃, and the insulation time is 90min~180min.

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