CN-122008578-A - High-efficiency mold-free molding method for polyimide composite honeycomb core

Abstract

The invention discloses a high-efficiency non-molding preparation method of a polyimide composite material honeycomb core, which comprises the steps of selecting a high-compactness two-dimensional fabric, preprocessing the fabric by using a polyamic acid solution to optimize an interface and apply matrix load of 0.7-0.9wt%, preparing node bonding glue solution with high viscosity (400-520 Pa.s), precisely coating the node glue on a preset node position of the fabric by a quantitative coating technology, hot-pressing and curing the node glue to form an undeployed 'white honeycomb' preform, mechanically expanding the white honeycomb to a designed shape and size by using a reusable dimension tool, and carrying out impregnation and curing of polyimide resin on the expanded honeycomb under the support of the tool to finally obtain the polyimide composite material honeycomb core. The invention thoroughly eliminates the traditional core mold laying and demolding procedures, and realizes the continuous, high-efficiency and low-cost near-net forming preparation of the large-size and thin-wall polyimide honeycomb core.

Inventors

• TAO JIE
• CHEN XI
• XIANG JUNXIAN
• LI HUAGUAN

Assignees

• 南京航空航天大学

Dates

Publication Date

20260512

Application Date

20260204

Claims (8)

1. 1. The high-efficiency mold-free preparation method of the polyimide composite honeycomb core is characterized by comprising the following steps of: s1, fabric pretreatment, namely selecting a dense two-dimensional fabric with small space between warp and weft yarns, carrying out impregnation pretreatment on the fabric by using a polyamic acid solution, and then drying to remove the solvent, so that the fabric obtains a polyamic acid load of 0.7-0.9wt%; S2, preparing node adhesive, namely adding filler and rheology modifier based on a polyimide matrix to prepare node adhesive solution with the viscosity of 400-520 Pa.s; S3, node coating and pre-curing, namely precisely coating the node glue solution configured in the step S2 on a preset bonding node area of the fabric pretreated in the step S1 by a quantitative coating means; S4, white honeycomb forming, namely, carrying out involution and positioning on the fabric coated with the node adhesive, and applying hot-pressing pressure to solidify the node adhesive to form an undeployed white honeycomb preform; s5, expanding the honeycomb dimension, namely placing the white honeycomb preform obtained in the step S4 into a reusable dimension tool, expanding the white honeycomb along a preset crease by mechanical means, and shaping the white honeycomb preform from the dimension tool to the designed geometric shape and dimension of the honeycomb; And S6, resin impregnation and final curing, namely under the support of a dimensional tooling, carrying out vacuum auxiliary impregnation of polyimide resin on the unfolded and shaped honeycomb, controlling the resin load, then carrying out stepped heating curing, and removing the tooling to obtain the polyimide composite material thin-wall honeycomb core.
2. 2. The high-efficiency non-molding method of the polyimide composite honeycomb core according to claim 1, wherein in the step S1, the two-dimensional fabric is a glass fiber, carbon fiber or aramid fiber fabric woven in plain, twill or satin, and the surface density is 80-200 g/m2.
3. 3. The high-efficiency molding-free method of the polyimide composite honeycomb core according to claim 1, wherein in the step S1, the solid content of the polyamic acid solution is 5-15%, the pretreatment adopts a dipping-rolling or spraying process, and the drying temperature is 80-120 ℃.
4. 4. The high-efficiency molding-free method of a polyimide composite honeycomb core according to claim 1, wherein in the step S2, the node glue solution uses thermoplastic or thermosetting polyimide resin as a matrix, and fumed silica or organic bentonite is added as a rheology modifier, and the viscosity range is strictly controlled to be 400-520 pa.s.
5. 5. The method for high-efficiency molding-free of a polyimide composite honeycomb core according to claim 1 or 4, wherein the node glue solution is coated by screen printing, gravure printing or precise dispensing technology to realize quantitative and positioning control.
6. 6. The efficient mold-free preparation method of the polyimide composite honeycomb core according to claim 1, wherein in the step S4, the temperature of the hot press curing is 180-220 ℃, the pressure is 0.5-2.0 MPa, and the time is 20-60 minutes.
7. 7. The method of claim 1, wherein in step S5, the dimensional tooling is a split mold or a combined modular mold with a negative cavity of the honeycomb, and the material is metal or composite.
8. 8. The high-efficiency non-molding method of the polyimide composite material honeycomb core according to claim 1, wherein in the step S6, the polyimide resin is PMR type or ethynyl end-capped polyimide resin, a vacuum auxiliary resin transfer molding process is adopted in the impregnation process, and the final curing system is raised from 150 ℃ to 250-320 ℃ in a step manner, and the heat and pressure are maintained.

Description

High-efficiency mold-free molding method for polyimide composite honeycomb core Technical Field The invention relates to the technical field of manufacturing of high-performance composite material honeycomb structures, belongs to a high-performance composite material honeycomb structure forming technology, and particularly relates to a high-efficiency non-molding preparation method of a polyimide composite material honeycomb core. Background The continuous fiber reinforced composite honeycomb structure has extremely high specific strength, specific rigidity, excellent fatigue resistance and designability, and is widely applied as a light bearing or heat insulation structural member in the fields of aerospace, rail transit, high-end equipment and the like. Among them, polyimide-based composite materials are the first choice materials in extreme environments due to their excellent high temperature, irradiation and dielectric properties. Conventional polyimide composite thin-wall honeycomb cores are typically prepared by a "mandrel forming process". The process comprises the steps of wrapping or laying reinforcing fiber fabrics outside a hexagonal core mould made of a large number of metal or composite materials, and finally dissolving or removing the core mould to obtain the honeycomb core through a series of processes of resin impregnation, sleeving, solidification and the like. The method has the advantages that the process principle is visual, but inherent defects are that firstly, when a large-size honeycomb core is prepared, thousands of core moulds are required to be laid, aligned and finally removed, the process is extremely complicated, the production efficiency is low, the cost is high, secondly, the demolding process is extremely easy to damage the thin-wall honeycomb cells, the product qualification rate is difficult to ensure, and finally, the manufacturing, maintenance and management of the core moulds per se also increase the additional cost and complexity. Therefore, the prior art has urgent need for a new method capable of getting rid of the dependence on a large number of entity core molds and realizing the preparation of the polyimide composite material thin-wall honeycomb core with high efficiency, high quality and near net shape. Based on the composite material liquid forming technology principle, a non-molding preparation process is developed, and the method has important significance for promoting engineering application of the high-performance structural material. Disclosure of Invention The invention aims to overcome the defects of the existing core mold forming method and provides a high-efficiency mold-free preparation method of a polyimide composite material thin-wall honeycomb core. According to the method, through the technical routes of node adhesive prefabrication, dimensional tooling shaping and liquid resin impregnation curing, the steps of laying and removing a core mold are thoroughly omitted, and the rapid, continuous and low-damage manufacturing of the large-size thin-wall honeycomb core is realized. In order to achieve the above purpose, the present invention adopts the following technical scheme: a high-efficiency mold-free preparation method of a polyimide composite honeycomb core comprises the following steps: (1) Fabric pretreatment, namely selecting a two-dimensional woven fabric with high compactness as a reinforcement body, and pretreating the two-dimensional woven fabric by using a low-concentration polyamic acid solution. The pretreatment aims at forming an extremely thin polyimide matrix precoat on the surface of the fiber, and the coating can improve the interface combination of the fiber and the subsequent impregnating resin and endow the fabric with certain stiffness and node glue impregnation controllability. The method is characterized in that the polyamide acid solid load of the pretreated fabric is precisely controlled to be 0.7-0.9wt% by controlling the technological parameters. The loading range is the result of repeated experimental optimization, namely, less than 0.7 percent, insufficient pretreatment effect, limited improvement of interface and stiffness, and more than 0.9 percent, the fabric is too stiff, the subsequent folding and unfolding performances are affected, and the resin impregnation is possibly hindered. (2) Node adhesive preparation and coating, namely preparing a high-viscosity polyimide-based adhesive for bonding honeycomb nodes. The key point is that the viscosity of the glue solution is strictly controlled within a high-viscosity non-flowing state range of 400-520 Pa.s. The viscosity range ensures that the glue solution can stably maintain the shape of a preset glue point after being coated on the pretreated fabric, and excessive flowing or penetration does not occur, so that the bonding area and the bonding thickness are accurately controlled, and the consistency of the node strength is ensured. The coating adopts quantitative tech