CN114161738B

CN114161738B - Method for net size forming of low-density fiber reinforcement material component suitable for RTM (resin transfer molding) process

Info

Publication number: CN114161738B
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: 2023-10-13
Anticipated expiration: 2041-11-29
Also published as: CN114161738A

Abstract

The invention provides a method for net size forming of a low-density fiber reinforcement material component, which is suitable for an RTM process; the method comprises the following steps: (1) mixing a glue solution raw material with a solvent to form a glue solution; (2) Spraying the glue solution obtained in the step (1) onto the fiber preform, and then paving and semi-drying; (3) Repeating the step (2) of spraying the glue solution for 1-20 times and the step (2) of laying 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 performing injection molding, curing and demolding, drying and moisture prevention by an RTM (resin transfer molding) process to obtain a member; the method solves the problem that the low-density fiber reinforcement reinforced porous material is net-shaped in an RTM mode, and can cancel the final product profile processing to obtain a high-profile-precision wrinkle-free product.

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 method for net-size forming of a low-density fiber reinforcement member applicable to an RTM (resin transfer molding) process.

Background

Along with the gradual rise of the flight Mach number of the aircraft, the flight time and the flight distance are prolonged, the weight requirement on the aircraft is also higher and higher, and more light high-strength composite materials become the research focus of the aircraft structure and the thermal protection materials. And fiber reinforced resin/precursor matrix composites are widely used and studied as light weight, high strength materials that can be prepared. The used fiber comprises glass fiber, carbon fiber, boron fiber, aramid fiber and the like, and the matrix comprises synthetic resin, rubber, ceramic precursor, carbon material and the like.

In order to ensure the weight requirement of the aircraft heat protection structure, in recent years, fiber reinforcement is gradually replaced by fiber cloth into a low-density fiber felt formed by connecting fiber net tyres or a reinforcement material formed by alternately arranging fiber cloth and low-density fiber felt layers, and the method can not only further effectively reduce the weight of the heat protection structure, but also can meet the application under the conditions of high scouring and shearing force.

However, in the preparation process of the composite material, as the bonding strength between the low-density fiber felt layers is weak, deformation is easy to occur before operation, so that the dimensional deviation of the molded surface is larger, especially for large-size special-shaped component products, once deformation occurs, folds with different depths are easy to occur on the molded surface of the product in the mold closing process, the folds can influence the pneumatic appearance in the flight process of the aircraft, the material can be locally damaged when serious, the temperature in the aircraft is increased, the normal operation of internal instruments is influenced, and therefore, the molded surface machining allowance is required to be reserved during the preparation, the production period of the product is prolonged, the economic benefit is low, the molded surface precision of the large-size special-shaped component during processing is controlled poorly, and finally the assembly of the product can be influenced.

Therefore, the problem that the low-density fiber reinforcement reinforced porous material is net-shaped in an RTM mode still needs to be solved, the final product profile processing is canceled, and a high-profile precision wrinkle-free product is obtained.

Disclosure of Invention

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

In order to solve the technical problem, the invention provides a method for net-size forming of a low-density fiber reinforcement material member suitable for an RTM process, which comprises the following steps:

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

(2) Spraying the glue solution obtained in the step (1) onto the fiber preform, and then paving and semi-drying;

(3) Repeating the step (2) of spraying the glue solution for 1-20 times and the step (2) of laying 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 carrying out injection molding, curing and demolding, drying and moisture-proof by an RTM process to obtain the 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, and the stress release in the process of carrying out the pre-treatment and the process of transporting the preform is controlled, so that the body shape surface of the reinforcement is effectively controlled, and the problem of deformation in the subsequent RTM process is avoided.

In the invention, the fiber reinforcement has low density, and the density is less than 0.15g/cm ³ The method comprises the steps of carrying out a first treatment on the surface of the In the existing method, a high-density fiber reinforcement is mainly used, and the treatment process is not needed; in other processes, a method of using a fiber cloth as a fixing layer is adopted, but the method can only fix one side, and the other side cannot be fixed due to an annular inner molded surface or a concave side, so that stress on one side is released, and a preform is deformed.

The meaning of the RTM process according to the invention is: resin transfer molding refers to a process technique in which a low viscosity resin flows in a closed mold, wets the reinforcing material, and cures.

Net size shaping means: high-precision components can be obtained without profile processing.

The semi-drying process is only preliminary shaping, and in order to facilitate the mold closing process, the solvent is completely dried after mold closing, and part of stress is released in the complete drying process, so that the low-density felt is completely attached to the mold.

In the step (1) of the invention, the glue solution raw material and the solvent are required to be mixed and dispersed until the solution is in a uniform and non-phase-separated state.

In the present invention, the fiber preform in the step (2) may be an already molded fiber reinforcement or an untreated fiber preform that needs to be laid. If the fiber reinforcement is formed, spraying glue solution on the surface of the fiber reinforcement directly, and then performing semi-drying, wherein the glue solution spraying time in the step (3) is 1-20 times, and the spreading time is 0 times; and for the fiber preform to be laid, the glue solution is sprayed, then the processes of laying and semi-drying are carried out, and the repeated circulation operation is carried out until the laying is completed, namely, the glue solution spraying time in the step (3) is 1-20 times, and the laying time is 1-20 times.

In the invention, after the pretreated fiber reinforcement body is embedded into the die in the step (4), the surface of the fiber reinforcement body is polished, and after the surplus material on the surface is removed, the die is closed. In the drying process, not only the solvent can be removed, but also the solidification of the glue solution can be realized.

The meaning of paving is: the fibers are weighed and cut and laminated to a fixed thickness layer by layer in a fixed shape.

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

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

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

In the invention, the glue raw material used is selected in a targeted manner according to the matrix used. For example, if a glass fiber reinforcement is used to reinforce an epoxy resin to prepare a composite material, the epoxy resin and butanone are used to prepare a glue; if the silica composite material is reinforced by adopting the quartz fiber reinforcement, the organosilicon 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 volatilizes too quickly, the solidification between the glue solution and the fiber reinforcement is incomplete and uneven, and the performance of the final molded product is reduced.

Preferably, the ratio of the glue raw material to the solvent in the step (1) is 1 (1-100), for example, may be 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, etc. 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 gram, and the solvent uses the volume unit of milliliter. The concentration of the finally dispersed glue solution is determined by the ratio, and when the concentration is controlled within the above range, the formed glue solution is 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 glue solution sprayed in the step (2) has the glue solution amount of 100-500 mL/m ³ For example, it may be 100mL/m ³ 、200mL/m ³ 、300mL/m ³ 、400mL/m ³ Or 500mL/m ³ Etc. The amount of glue can affect the hardness of the final formed component housing. If the pectin liquid amount is too high, the hardness of the shell is too high; if the pectin liquid amount is too low, the effect of enhancing the adhesion cannot be achieved.

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

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

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

Preferably, the drying time in step (4) is 2 to 10 hours and the drying temperature is not more than 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 a proportion of 1 (1-100), 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 and the solvent is the mass-volume ratio;

(2) Spraying the glue solution obtained in the step (1) onto a fiber preform with the thickness of 5-40 mm,then laying and semi-drying, wherein the spraying amount of the glue solution is 100-500 mL/m ³ The semi-drying temperature is 30-50 ℃ and the semi-drying time is 10-30 min;

(4) Embedding the pretreated fiber reinforcement obtained in the step (3) into a mold, polishing, drying for 2-10 hours, and performing injection molding, curing and demolding by an RTM (resin transfer molding) process after the temperature of the drying is not higher than the boiling point of a solvent, fixing by a clamp after demolding, and drying and dampproofing 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 die assembly process;

(2) The method provided by the invention can obtain a net-size forming member;

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

(4) The composite material prepared by the method can not influence the original material properties, such as mechanical strength and the like.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Example 1

(1) Silica sol and water are mixed according to the mass to volume ratio of 1:20, mixing and dispersing until the solution is uniform and is not split;

(2) Spreading basalt cotton fiber with a fiber preform thickness of 20mm, spreading and spraying glue for 5 times, wherein the glue spraying amount is 200mL/m each time ³ . The semi-drying temperature is 35 ℃,half-drying time is 20min;

(3) Embedding the paved basalt cotton reinforcement into a mould, polishing the surface, removing the surplus and then closing the mould. Putting the die into a baking oven at 90 ℃ for 8 hours for solvent removal;

(4) RTM glue injection molding, demoulding after solidification, fixing by using a clamp after demoulding, and further drying, dampproof treatment and product allowance processing to obtain the component.

Example 2

(1) Phenolic resin and ethanol are mixed according to the mass to volume ratio of 1:20, mixing and dispersing until the solution is uniform and is not split;

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

(3) And sleeving the dried low-density carbon fiber reinforcement into a die, polishing the surface, removing the surplus materials, and then closing the die. Putting the die into a baking oven at 70 ℃ for 8 hours to remove the solvent;

Example 3

(1) The aluminum sol and water are mixed according to the mass to volume ratio of 1:60, mixing and dispersing until the solution is uniform and is not split;

(2) Spreading low density alumina fiber with thickness of 30mm, spreading and spraying glue for 10 times, and spraying glue 300mL/m each time ³ . The half-drying temperature is 30 ℃, and the half-drying time is 30min;

(3) Embedding the low-density alumina fiber reinforcement into a mold, polishing the surface, removing the surplus and then closing the mold. Putting the die into an oven at 85 ℃ for 8 hours for solvent removal;

Example 4

(1) Polyimide resin and ethanol are mixed according to the mass to volume ratio of 1:90, mixing and dispersing until the solution is uniform and is not split;

(2) Spreading low density quartz fiber reinforcement with thickness of 10mm, spreading and spraying glue 15 times, each time with glue spraying amount of 400mL/m ³ . The half-drying temperature is 50 ℃, and the half-drying time is 30min;

(3) And embedding the quartz fiber into a mold, polishing the surface, removing the surplus and then closing the mold. Putting the die into a 65 ℃ oven for 9 hours for solvent removal;

Example 5

The present example differs from example 1 only in that the basalt cotton fiber preform used in this example was 50mm thick, and a member was obtained after processing.

Example 6

The present example differs from example 1 only in that the basalt cotton fiber preform used in this example was 2mm thick, and a member was obtained after processing.

Example 7

The difference between the present embodiment and embodiment 1 is that the amount of the adhesive sprayed in the step (2) of the present embodiment is 600mL/m ³ And (5) processing to obtain the component.

Example 8

The difference between the present embodiment and embodiment 1 is that the amount of glue sprayed in step (2) of the present embodiment is 50mL/m ³ And (5) processing to obtain the component.

Example 9

The difference between this example and example 1 is only that the mass to volume ratio of silica sol and water in step (1) of this example is 1:150, mixing and dispersing, and processing to obtain the component.

Example 10

The difference between this example and example 1 is only that the mass to volume ratio of silica sol and water in step (1) of this example is 1: and 0.5, mixing and dispersing, and processing to obtain the component.

Example 11

The difference between this example and example 1 is that the molded basalt cotton fiber preform is used in step (2) of this example, and the molded basalt cotton fiber preform is not required to be laid, but is subjected to glue spraying only 5 times, and the molded basalt cotton fiber preform is finally processed to obtain a member.

Comparative example 1

The comparative example differs from example 1 only in that the basalt cotton fiber preform was not pretreated with the dope, i.e., the process of spraying the dope in step (1) and step (2) was not included in the comparative example.

The components provided in examples 1-11 and comparative example 1 above were subjected to profile testing by directly measuring the amount of change in the variant wrinkles and the profile accuracy. Wherein ". Times.no." means no greater than.

The test results are shown in table 1:

TABLE 1

As can be seen from the results of the above examples and comparative examples, the method of examples 1-3 provides lower component variation, higher precision, and a net-size molded component with better performance. In example 4, the resin proportion was low, and the effect on the change of the strain was not significant.

In the embodiment 5, the thickness is too large, so that the impregnation is uneven and the profile precision is poor; in example 6, the glue easily penetrates the preform due to the thinner thickness, and the stress in the preform is affected to cause deviation of the profile.

In example 7, too high a glue spray amount resulted in too hard a surface layer, and the glue spray amount could not be matched with micro extrusion generated in the mold closing process, resulting in large wrinkles. Example 8 has too low a spray, resulting in insufficient inter-fiber adhesion and a deformable profile.

In example 9 and example 10, there was a problem of the resin content as well, and the deformation was large, and the wrinkle accuracy was low.

Comparative example 1 does not include the process of molding the dope, the deformation is large, and the accuracy is reduced.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the 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 scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for net-size shaping of a low-density fiber reinforcement member suitable for use in an RTM process, characterized by: the method comprises the following steps:

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

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

the glue solution raw material in the step (1) is resin or precursor;

the resin comprises any one or a combination of at least two of epoxy resin, polyimide resin, phenolic resin, vinyl ester resin or organic silicon resin;

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

the ratio of the glue solution raw material to the solvent in the step (1) is 1 (1-100);

the thickness of the fiber preform in the step (2) is 5-40 mm;

the glue solution sprayed in the step (2) has the glue solution amount of 100-500 mL/m ³ ；

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

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

2. The method according to claim 1, characterized in that:

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

3. The method according to claim 2, characterized in that:

the solvent comprises water and/or ethanol.

4. The method according to claim 1, characterized in that: the material of the fiber preform in the step (2) comprises any one or a combination of at least two of an organic fiber needled felt, an inorganic fiber needled felt, an organic fiber cloth or an inorganic fiber cloth.

5. The method according to claim 1, wherein: and (3) drying in the step (4) for 2-10 hours at a temperature not exceeding the boiling point of the solvent.

6. The method of any one of claims 1-5, wherein: the method comprises the following steps:

(2) Spraying the glue solution obtained in the step (1) onto a fiber preform with the thickness of 5-40 mm, then paving, semi-drying and spraying the glue solutionThe amount is 100-500 mL/m ³ The semi-drying temperature is 30-50 ℃ and the semi-drying time is 10-30 min;