CN114161738A

CN114161738A - Method for net size forming of low-density fiber reinforcement material component suitable for RTM (resin transfer molding) process

Info

Publication number: CN114161738A
Application number: CN202111473450.9A
Authority: CN
Inventors: 张鸶鹭; 徐沛; 陈玉铃; 孙景景; 张贝贝; 张凡; 李文静
Original assignee: Aerospace Research Institute of Materials and Processing Technology
Current assignee: Aerospace Research Institute of Materials and Processing Technology
Priority date: 2021-11-29
Filing date: 2021-11-29
Publication date: 2022-03-11
Anticipated expiration: 2041-11-29
Also published as: CN114161738B

Abstract

The invention provides a net size forming method of a low-density fiber reinforcement material component, which is suitable for an RTM (resin transfer molding) process; the method comprises the following steps: (1) mixing the glue solution raw material with a solvent to form a glue solution; (2) spraying the glue solution obtained in the step (1) on a fiber preform, and then spreading and semi-drying; (3) spraying the glue solution in the step (2) for 1-20 times and spreading the glue solution in the step (2) for 0-20 times to obtain a pretreated fiber reinforcement; (4) embedding the pretreated fiber reinforcement obtained in the step (3) into a mold, polishing and drying, and then performing glue injection molding, curing demolding, drying and moisture prevention by using an RTM (resin transfer molding) process to obtain a component; the method provided by the invention solves the problem of net molding of the low-density fiber reinforcement reinforced porous material in an RTM (resin transfer molding) mode, and can cancel the final molded surface processing of the product to obtain the product with high molded surface precision and no wrinkles.

Description

Method for net size forming of low-density fiber reinforcement material component suitable for RTM (resin transfer molding) process

Technical Field

The invention relates to the technical field of composite materials, in particular to a net size forming method of a low-density fiber reinforcement material component, which is suitable for an RTM (resin transfer molding) process.

Background

With the increasing of the flying mach number of the aircraft, the extension of the flying time and the flying distance, the weight requirement of the aircraft is higher and higher, and more light-weight high-strength composite materials become the research focus of the structure and the thermal protection materials of the aircraft. The fiber reinforced resin/precursor matrix composite material is widely applied and researched as a light high-strength material which can be prepared. The fiber used includes glass fiber, carbon fiber, boron fiber, aramid fiber and the like, and the matrix includes synthetic resin, rubber, ceramic precursor, carbon material and the like.

In order to meet the weight requirement of an aircraft thermal protection structure, in recent years, fiber reinforcements are gradually replaced by low-density fiber felts formed by connecting fiber net tires with fiber cloth or reinforcement materials formed by alternating fiber cloth and low-density fiber felt layers.

However, in the process of preparing the composite material, because the bonding strength between low-density fiber felt layers is weak, deformation is easy to occur before operation, so that the size deviation of the molded surface is large, particularly for large-size special-shaped component products, once deformation occurs, wrinkles with different depths are easy to occur on the molded surface of the product in the mold closing process, the wrinkles can influence the pneumatic appearance in the flying process of an aircraft, and can cause local damage of the material when serious, the temperature in the aircraft is increased, and the normal work of internal instruments is influenced, so that the processing allowance of the molded surface needs to be reserved during preparation, the production cycle of the product is prolonged, the economic benefit is low, the precision control of the molded surface during processing of the large-size special-shaped component is poor, and finally the product assembly is influenced.

Therefore, the problem of net molding of the low-density fiber reinforcement porous material in an RTM manner still needs to be solved, and the final product profile processing is eliminated, so that a product with high profile precision and no wrinkles is obtained.

Disclosure of Invention

The invention aims to solve the technical problems that the existing low-density fiber felt is weak in interlayer bonding strength and easy to deform before operation, and provides a method for net size forming of a low-density fiber reinforcement material component suitable for an RTM (resin transfer molding) process aiming at the defects in the prior art.

In order to solve the above technical problem, the present invention provides a method for net-size forming of a low-density fiber-reinforced member suitable for RTM process, the method comprising the steps of:

(1) mixing the glue solution raw material with a solvent to form a glue solution;

(2) spraying the glue solution obtained in the step (1) on a fiber preform, and then spreading and semi-drying;

(3) spraying the glue solution in the step (2) for 1-20 times and spreading the glue solution in the step (2) for 0-20 times to obtain a pretreated fiber reinforcement;

(4) and (4) embedding the pretreated fiber reinforcement obtained in the step (3) into a mold, polishing and drying, and then performing resin injection molding, curing demolding, drying and moisture prevention by using an RTM (resin transfer molding) process to obtain a component.

According to the method provided by the invention, the bonding strength between fiber layers is improved through the process of molding the fiber reinforcement by the glue solution, the stress release in the processes of transportation and pretreatment in the process of processing the prefabricated body is controlled, the molded surface of the reinforcement is effectively controlled, and the problem of deformation in the subsequent RTM process is avoided.

In the present invention, the fiber reinforcement has a low density of less than 0.15g/cm³(ii) a In the prior art, the high-density fiber reinforcement is mainly used, and the treatment process is not needed; while other processes have been described using fiber cloth as the anchoring layer, the method can only anchor one side, while the other side cannot anchor due to the annular inner profile or the concave side, which still results in stress relief on one side and deformation of the preform.

The RTM process of the invention has the following meanings: resin transfer molding refers to a process technique in which a low viscosity resin flows in a closed mold, infiltrates a reinforcing material, and is cured.

Net shape meaning: a high-precision member can be obtained without performing profile processing.

The semi-drying process is only primary shaping, so that in order to facilitate the die closing process, all drying of the solvent is carried out after die closing, and a part of stress is released in all drying processes, so that the low-density felt is completely attached to the die.

In the step (1) of the invention, the glue solution raw material and the solvent need to be mixed and dispersed until the solution becomes a uniform and non-phase separation state.

In the present invention, the fiber preform in step (2) may be a fiber reinforcement that has been formed, or may be a fiber preform that has not been treated and needs to be laid. If the fiber reinforcement is formed, directly spraying glue solution on the surface of the fiber reinforcement, and then performing a semi-drying process, wherein the glue solution spraying frequency in the step (3) is 1-20 times, and the spreading frequency is 0 time; and for the fiber preform to be paved, spraying glue solution, then performing paving and semi-drying processes, and repeating the circulating operation until the paving is completed, namely the spraying frequency of the glue solution in the step (3) is 1-20 times, and the paving frequency is 1-20 times.

In the invention, after the pretreated fiber reinforcement is embedded into the mold in the step (4), the surface of the fiber reinforcement is polished, and after the excess on the surface is removed, the mold is closed. The drying process can not only remove the solvent, but also realize the solidification of the glue solution.

The meaning of the overlay is: weighing and cutting the fibers, and superposing the fibers layer by layer to a fixed thickness according to a fixed shape.

Preferably, the glue solution raw material in the step (1) is resin or a precursor.

Preferably, the resin comprises any one of an epoxy resin, a polyimide resin, a phenolic resin, a vinyl ester resin or a silicone resin or a combination of at least two thereof. The resin used in the present invention may be any resin that can produce good tackiness, and is not limited to the above-listed resins.

The precursor comprises any one of siloxane, silica sol or aluminum sol or the combination of at least two of the siloxane, the silica sol and the aluminum sol. Precursors useful in the present invention include, but are not limited to, the above listed precursors.

In the invention, the glue solution raw materials are selected in a targeted manner according to the used matrix. For example, if the glass fiber reinforcement reinforced epoxy resin is used for preparing the composite material, the epoxy resin and butanone are used for preparing glue; if the silica composite material reinforced by the quartz fiber reinforcement is adopted, the organic silicon precursor and ethanol are adopted for glue preparation.

Preferably, the solvent in step (1) is a solvent having a boiling point higher than 50 ℃.

Preferably, the solvent comprises water and/or ethanol.

In the invention, the boiling point of the solvent cannot be too low, if the solvent with the lower boiling point is selected, the solvent is volatilized too fast, the glue solution and the fiber reinforcement are not cured completely and are not uniform, and the performance of the final formed fiber is reduced.

Preferably, the ratio of the glue solution raw material to the solvent in the step (1) is 1 (1-100), and may be, for example, 1:1, 1:2, 1:10, 1:20, 1:25, 1:30, 1:43, 1:50, 1:60, 1:70, 1:80, 1:90, or 1: 100. In the invention, the ratio of the glue solution raw material to the solvent is the ratio of mass to volume, the glue solution raw material uses the mass unit of 'g' and the solvent uses the volume unit of 'ml'. This ratio determines the concentration of the final dispersion into a glue solution, and when it is controlled within the above range, the formed glue solution becomes more uniform.

Preferably, the thickness of the fiber preform in the step (2) is 5 to 40mm, and may be, for example, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, or the like.

Preferably, the amount of the glue solution sprayed on the glue solution in the step (2) is 100-500 mL/m³For example, it may be 100mL/m³、200mL/m³、300mL/m³、400mL/m³Or 500mL/m³And the like. The amount of glue affects the hardness of the final formed component casing. If the glue solution amount is too high, the hardness of the shell is too high; if the amount of the glue solution is too low, the effect of strengthening the adhesion cannot be achieved.

The temperature of the semi-drying in the step (2) is 30-50 ℃, for example, 30 ℃, 35 ℃, 40 ℃, 45 ℃ or 50 ℃ and the like,

the half drying time in the step (2) is 10-30 min, for example, 10min, 15min, 20min, 25min or 30 min.

Preferably, the material of the fiber preform in the step (2) comprises any one of an organic fiber needle felt, an inorganic fiber needle felt, an organic fiber cloth or an inorganic fiber cloth or a combination of at least two of the organic fiber needle felt, the inorganic fiber needle felt, the organic fiber cloth or the inorganic fiber cloth.

Preferably, the drying time in the step (4) is 2-10 h, and the drying temperature does not exceed the boiling point of the solvent.

Preferably, the method specifically comprises the following steps:

(1) mixing a glue solution raw material and a solvent according to the proportion of 1 (1-100) to form a glue solution, wherein the glue solution raw material comprises resin or a precursor, the solvent comprises water and/or ethanol, and the proportion of the glue solution raw material to the solvent is the ratio of mass to volume;

(2) spraying the glue solution obtained in the step (1) onto a fiber preform with the thickness of 5-40 mm, and then spreading and semi-drying, wherein the spraying amount of the glue solution is 100-500 mL/m³The temperature of the semi-drying is 30-50 ℃, and the time is 10-30 min;

(4) and (4) embedding the pretreated fiber reinforcement obtained in the step (3) into a mold, polishing and drying for 2-10 hours at a temperature not exceeding the boiling point of a solvent, injecting glue for molding through an RTM (resin transfer molding) process, curing and demolding, fixing by using a clamp after demolding, and drying and preventing moisture to obtain the component.

The implementation of the invention has the following beneficial effects:

(1) the fiber reinforced matrix composite material prepared by the method can effectively avoid wrinkles in the mold closing process;

(2) the method provided by the invention can obtain net-size forming components;

(3) the precision of the molded surface of the component prepared by the method is +/-0.3 mm;

(4) the composite material prepared by the method cannot influence the original material properties such as mechanical strength and the like.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example 1

(1) Mixing silica sol and water in a mass-to-volume ratio of 1:20, mixing and dispersing until the solution is uniform and does not separate phases;

(2) taking basalt rock wool fiber to pave, wherein the thickness of a fiber preform to be paved is 20mm, the paving and glue spraying times are 5 times, and the glue spraying amount is 200mL/m each time³. The semi-drying temperature is 35 ℃, and the semi-drying time is 20 min;

(3) and embedding the paved basalt wool reinforcement into a mold, polishing the surface, removing excess materials, and then closing the mold. Placing the mould into a drying oven at 90 ℃ for processing for 8h to remove the solvent;

(4) RTM glue injection molding, demolding after curing, fixing by using a clamp after demolding, further drying, damp-proof treatment and product allowance processing to obtain the component.

Example 2

(1) Mixing phenolic resin and ethanol in a mass-to-volume ratio of 1:20, mixing and dispersing until the solution is uniform and does not separate phases;

(2) a low-density carbon fiber reinforcement (density of 0.1 g/cm)³) Placing on a spraying tool, setting the thickness of the fiber preform to be 15mm and the glue spraying amount to be 300ml/m³. The semi-drying temperature is 40 ℃, and the semi-drying time is 10 min;

(3) and sleeving the dried low-density carbon fiber reinforcement into a mold, polishing the surface, removing the excess, and then closing the mold. Placing the mould into an oven at 70 ℃ for treatment for 8h to remove the solvent;

Example 3

(1) Mixing aluminum sol and water in a mass-to-volume ratio of 1:60, mixing and dispersing until the solution is uniform and does not separate phases;

(2) spreading low-density alumina fiber with a thickness of 30mm, spreading and spraying for 10 times (300 mL/m) each time³. The semi-drying temperature is 30 ℃, and the semi-drying time is 30 min;

(3) embedding the low-density alumina fiber reinforcement into a mold, polishing the surface, removing the excess, and closing the mold. Placing the mould into an oven at 85 ℃ for treatment for 8h to remove the solvent;

Example 4

(1) Mixing polyimide resin and ethanol in a mass-to-volume ratio of 1:90, mixing and dispersing until the solution is uniform and does not separate phases;

(2) spreading a low-density quartz fiber reinforcement, wherein the thickness of a fiber preform to be spread is 10mm, the spreading and glue spraying times are 15 times, and the glue spraying amount is 400mL/m each time³. The semi-drying temperature is 50 ℃, and the semi-drying time is 30 min;

(3) and embedding the quartz fiber into a mold, polishing the surface, removing the excess, and then closing the mold. Placing the mould into a drying oven at 65 ℃ for treatment for 9h to remove the solvent;

Example 5

The present example is different from example 1 only in that the basalt rock wool fiber preform used in the present example has a thickness of 50mm and is processed to obtain a member.

Example 6

This example is different from example 1 only in that the basalt rock wool fiber preform used in this example had a thickness of 2mm and was processed to obtain a member.

Example 7

The difference between this example and example 1 is that the amount of glue sprayed per time in step (2) of this example is 600mL/m³And processing to obtain the component.

Example 8

The difference between this example and example 1 is only that the amount of glue sprayed per time in step (2) of this example is 50mL/m³And processing to obtain the component.

Example 9

The present example is different from example 1 only in that, in step (1) of the present example, the ratio of silica sol to water in mass to volume is 1: 150, and processing to obtain the component.

Example 10

The present example is different from example 1 only in that, in step (1) of the present example, the ratio of silica sol to water in mass to volume is 1: 0.5, mixing and dispersing, and processing to obtain the member.

Example 11

The difference between this example and example 1 is that the basalt rock wool fiber preform molded in step (2) of this example was used, and no coating was required, and only 5 times of glue spraying was performed, and a member was obtained after final processing.

Comparative example 1

The present comparative example is different from example 1 only in that the basalt rock wool fiber preform is not pretreated with glue solution in the present comparative example, that is, the glue spraying process in the step (1) and the step (2) is not included.

The members provided in examples 1 to 11 and comparative example 1 were subjected to a profile test by directly measuring the amount of change in the profile wrinkles and the profile accuracy. Wherein the meaning of not more than is not more than.

The test results are shown in table 1:

TABLE 1

It can be seen from the results of the above examples and comparative examples that the part types produced by the methods provided in examples 1-3 have lower variability, higher accuracy and better net-shape formed parts can be obtained. In example 4, the resin ratio was low, and the effect on the deformation change was not significant.

In example 5, the impregnation is not uniform due to the excessively large thickness and the excessively large thickness, and the profile accuracy is poor; in example 6, the glue solution easily penetrates through the preform due to the thin thickness, and the stress in the preform is influenced to cause the profile to deviate.

In example 7, the surface layer was too hard due to an excessively high amount of sprayed glue, and the surface layer could not be matched with a slight squeeze generated in the mold closing process, resulting in a large wrinkle. Example 8 the amount of sprayed glue was too low, resulting in insufficient inter-fiber bonding and a deformed profile.

In example 9 and example 10, the resin content was also problematic, which resulted in a large pattern and a low wrinkle accuracy.

Comparative example 1 does not include a process of forming a glue solution, the form becomes larger, and the accuracy is reduced.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A method for net size forming of a low-density fiber reinforcement member suitable for RTM process is characterized in that: the method comprises the following steps:

2. The method of claim 1, wherein: in the step (1), the glue solution raw material is resin or a precursor.

3. The method of claim 2, wherein: the resin comprises any one or the combination of at least two of epoxy resin, polyimide resin, phenolic resin, vinyl ester resin or organic silicon resin;

the precursor comprises any one of siloxane, silica sol or aluminum sol or the combination of at least two of the siloxane, the silica sol and the aluminum sol.

4. The method of claim 1, wherein: the solvent in the step (1) is a solvent with the boiling point higher than 50 ℃;

preferably, the solvent comprises water and/or ethanol.

5. The method of claim 1, wherein: the ratio of the glue solution raw material to the solvent in the step (1) is 1 (1-100).

6. The method of claim 1, wherein: and (3) in the step (2), the thickness of the fiber preform is 5-40 mm.

7. The method according to claim 1, wherein the glue solution sprayed in step (2) is glueThe liquid amount is 100 to 500mL/m³；

The temperature of the semi-drying in the step (2) is 30-50 ℃;

and (3) the half drying time in the step (2) is 10-30 min.

8. The method of claim 1, wherein: the material of the fiber preform in the step (2) comprises any one or a combination of at least two of organic fiber needled felt, inorganic fiber needled felt, organic fiber cloth or inorganic fiber cloth.

9. The method of claim 1, wherein: in the step (4), the drying time is 2-10 h, and the drying temperature does not exceed the boiling point of the solvent.

10. The method according to any one of claims 1-9, wherein: the method comprises the following steps: