CN114161738B - A method for net-size molding of low-density fiber-reinforced material components suitable for RTM process - Google Patents

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

A kind of net size of low-density fiber reinforced material components suitable for RTM process inch forming method

Technical field

The present invention relates to the technical field of composite materials, and in particular to a method for net-size molding of low-density fiber reinforced reinforced material components suitable for RTM technology.

Background technique

As the flight Mach number of aircraft gradually increases, the flight time and flight distance are extended, and the weight requirements of aircraft are also getting higher and higher. More and more lightweight and high-strength composite materials have become the focus of research on aircraft structure and thermal protection materials. Fiber-reinforced resin/precursor matrix composite materials are widely used and studied as lightweight and high-strength materials that can be prepared. The fibers used include glass fiber, carbon fiber, boron fiber, aramid fiber, etc., and the matrix includes synthetic resin, rubber, ceramic precursors, and carbon materials.

In order to ensure the weight requirements of aircraft thermal protection structures, in recent years, fiber reinforcements have gradually been replaced by fiber cloths with low-density fiber mats connected by fiber mesh tires, or reinforcements with alternating layers of fiber cloths and low-density fiber mats. Material, this method can further effectively reduce the weight of the thermal protection structure, and at the same time can meet the application under conditions of high scour and shear force.

However, during the preparation process of composite materials, due to the weak bonding strength between low-density fiber mat layers, deformation is prone to occur before operation, resulting in large deviations in profile dimensions. Especially for large-size special-shaped component products, once deformation occurs, the mold will be damaged during the mold closing process. The product surface is prone to wrinkles of different shades. These wrinkles will affect the aerodynamic shape of the aircraft during flight. In severe cases, they can cause local damage to the material, increase the temperature inside the aircraft, and affect the normal operation of internal instruments. Therefore, they need to be reserved during preparation. The allowance for surface processing results in extended product production cycles and low economic benefits. The control of surface accuracy when processing large-size special-shaped components is poor, which will ultimately affect product assembly.

Therefore, it is still necessary to solve the problem of net forming of low-density fiber reinforced porous materials through RTM, eliminate the final product profile processing, and obtain products with high profile accuracy and no wrinkles.

Contents of the invention

The technical problem to be solved by this invention is that the existing low-density fiber felt has weak bonding strength between layers and is easily deformed before operation. In view of the defects in the existing technology, a low-density fiber reinforcement reinforcement material suitable for the RTM process is provided. Method for forming net dimensions of components.

In order to solve the above technical problems, the present invention provides a method for net-size molding of low-density fiber reinforced reinforced material components suitable for RTM technology. The method includes the following steps:

(1) Mix glue raw materials and solvent to form glue;

(2) Spray the glue obtained in step (1) onto the fiber preform, and then spread and semi-dry;

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

(4) Embed the pretreated fiber reinforcement obtained in step (3) into the mold. After polishing and drying, the component is obtained by injection molding through the RTM process, curing and demoulding, and drying and moisture-proofing.

The method provided by the invention improves the bonding strength between fiber layers through the process of molding the fiber reinforcement with glue, controls the stress release during the transportation and pre-treatment of the preform, and effectively controls the surface of the reinforcement. , avoiding the problem of deformation in the subsequent RTM process.

In the present invention, the density of the fiber reinforcement is low, and its density is less than 0.15g/cm ³ ; in the existing method, high-density fiber reinforcement is mainly used, which does not need to go through the above treatment process; and in other processes, there are Fiber cloth is used as a method of fixing the layer, but this method can only be fixed on one side. The other side cannot be fixed because it is an annular inner surface or a concave side. This will still cause the stress on one side to be released and cause the prefabricated body to deform.

The meaning of the RTM process in the present invention: Resin transfer molding refers to a process technology in which low-viscosity resin flows in a closed mold, infiltrates reinforcement materials, and solidifies to form.

The meaning of net dimension forming: high-precision components can be obtained without surface processing.

The semi-drying process described in the present invention is only preliminary shaping. In order to facilitate the mold closing process, all solvents are dried after mold closing, and part of the stress is released during the entire drying process to completely fit the low-density felt to the mold.

In step (1) of the present invention, the glue raw materials and the solvent need to be mixed and dispersed until the solution becomes a homogeneous and phase-free state.

In the present invention, the fiber preform in step (2) may be a fiber reinforcement that has been formed, or may be an untreated fiber preform that needs to be spread. If it is a fiber reinforcement that has been formed, just spray glue directly on its surface, and then perform a semi-drying process, that is, the number of glue sprays in step (3) is 1 to 20 times, and The number of times of paving is 0; for the fiber preform that needs to be paved, it needs to be sprayed with glue, and then the process of paving and semi-drying is carried out, and the cycle operation is repeated until the paving is completed, that is, at this time, the steps ( 3) The number of times of spraying the glue solution is 1 to 20 times, and the number of times of spreading is 1 to 20 times.

In the present invention, after the pretreated fiber reinforcement is embedded in the mold in step (4), its surface is polished and excess material on the surface is removed before the mold is closed. The drying process not only removes the solvent, but also solidifies the glue.

The meaning of laying is: weigh and cut the fibers, and stack the fibers layer by layer in a fixed shape to a fixed thickness.

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

Preferably, the resin includes 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 can be any resin that can produce good adhesiveness, and is not limited to the resins listed above.

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

In the present invention, the glue raw materials used are selected in a targeted manner according to the matrix used. For example, if glass fiber reinforced epoxy resin is used to prepare composite materials, epoxy resin and MEK are used for compounding; if quartz fiber reinforced silica composite materials are used, silicone precursor and ethanol are used for compounding. With glue.

Preferably, the solvent described in step (1) is a solvent with a boiling point higher than 50°C.

Preferably, the solvent includes water and/or ethanol.

In the present invention, the boiling point of the solvent cannot be too low. If a solvent with a lower boiling point is selected, the solvent will evaporate too quickly, resulting in incomplete and uneven solidification between the glue and the fiber reinforcement, which will reduce the performance after final molding.

Preferably, the ratio of glue raw materials and solvents in step (1) is 1: (1-100), for example, it can 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 present invention, the ratio of the glue raw materials to the solvent is the ratio of mass to volume. The glue raw materials use the mass unit "gram", and the solvent uses the volume unit "ml". This ratio determines the concentration of the final dispersion into glue. When controlled within the above range, the glue formed will be more uniform.

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

Preferably, the amount of glue sprayed in step (2) is 100-500mL/m ³ , for example, it can be 100mL/m ³ , 200mL/m ³ , 300mL/m ³ , 400mL/m ³ or 500mL/m 3 m ³ etc. The amount of glue affects the hardness of the final formed component shell. If the amount of glue is too high, the hardness of the shell will be too high; if the amount of glue is too low, the adhesive enhancement effect will not be achieved.

The semi-drying temperature in step (2) is 30-50°C, for example, it can be 30°C, 35°C, 40°C, 45°C or 50°C, etc.

The half-drying time in step (2) is 10 to 30 minutes, for example, it can be 10 minutes, 15 minutes, 20 minutes, 25 minutes or 30 minutes.

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

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

Preferably, the method specifically includes the following steps:

(1) Mix the glue raw materials and the solvent at a ratio of 1: (1 to 100) to form a glue, in which the glue raw materials include resin or precursor, the solvent includes water and/or ethanol, and the glue raw materials and solvent are Ratio is the ratio of mass to volume;

(2) Spray the glue obtained in step (1) onto a fiber preform with a thickness of 5 to 40 mm, and then spread and semi-dry the glue. The glue spray volume is 100 to 500 mL/m ³ , and the semi-dried The temperature is 30~50℃ and the time is 10~30min;

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

(4) Embed the pretreated fiber reinforcement obtained in step (3) into the mold, grind and dry it for 2 to 10 hours and the drying temperature does not exceed the boiling point of the solvent, then use the RTM process to injection mold, solidify and demould. After demoulding, clamps are used to fix it, and then the components are obtained after drying and moisture-proofing.

Implementing the present invention has the following beneficial effects:

(1) The fiber-reinforced matrix composite material prepared by the present invention can effectively avoid wrinkles during the mold closing process;

(2) The method provided by the invention can obtain net size formed components;

(3) The surface accuracy of the components prepared by the method of the present invention is ±0.3mm;

(4) The composite materials prepared by the present invention will not affect the original material properties, such as mechanical strength.

Detailed ways

In order to make the purpose, 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. Obviously, the described embodiments are part of the embodiments of the present invention, not All examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without any creative work fall within the scope of protection of the present invention.

Example 1

(1) Mix and disperse the silica sol and water at a mass to volume ratio of 1:20 until the solution is uniform without phase separation;

(2) Take basalt wool fiber for paving. The thickness of the fiber preform to be paved is 20mm. The number of paving and glue spraying is 5 times. The amount of glue sprayed each time is 200mL/m ³ . The semi-drying temperature is 35°C and the semi-drying time is 20 minutes;

(3) Embed the covered basalt wool reinforcement into the mold, polish the surface, remove excess material and close the mold. Put the mold into an oven at 90°C for 8 hours to remove the solvent;

(4) RTM glue injection molding, demoulding after curing, fixing with clamps after demoulding, and then further drying, moisture-proof treatment, and product remainder processing to obtain components.

Example 2

(1) Mix and disperse the phenolic resin and ethanol at a mass to volume ratio of 1:20 until the solution is uniform and phase-free;

(2) Place the low-density carbon fiber reinforcement (density 0.1g/cm ³ ) on the spraying tool. The thickness of the fiber preform is 15mm, and the spray glue volume is set to 300ml/m ³ . The semi-drying temperature is 40℃, and the semi-drying time is 10 minutes;

(3) Put the dried low-density carbon fiber reinforcement into the mold, polish the surface, remove excess material and close the mold. Place the mold in an oven at 70°C for 8 hours to remove the solvent;

(4) RTM glue injection molding, demoulding after curing, fixing with clamps after demoulding, and then further drying, moisture-proof treatment, and product remainder processing to obtain components.

Example 3

(1) Mix and disperse the aluminum sol and water at a mass to volume ratio of 1:60 until the solution is homogeneous without phase separation;

(2) Take low-density alumina fiber for paving. The thickness of the fiber preform to be paved is 30mm. The number of paving and glue spraying is 10 times. The amount of glue sprayed each time is 300mL/m ³ . The semi-drying temperature is 30°C and the semi-drying time is 30 minutes;

(3) Embed the low-density alumina fiber reinforcement into the mold, polish the surface, remove excess material and close the mold. Put the mold into an oven at 85°C for 8 hours to remove the solvent;

(4) RTM glue injection molding, demoulding after curing, fixing with clamps after demoulding, and then further drying, moisture-proof treatment, and product remainder processing to obtain components.

Example 4

(1) Mix and disperse the polyimide resin and ethanol at a mass to volume ratio of 1:90 until the solution is homogeneous without phase separation;

(2) Take low-density quartz fiber reinforcement for paving. The thickness of the fiber preform to be paved is 10mm, the number of paving and glue spraying is 15 times, and the glue spraying amount each time is 400mL/m ³ . The semi-drying temperature is 50℃, and the semi-drying time is 30 minutes;

(3) Embed the quartz fiber into the mold, polish the surface, remove excess material and close the mold. Place the mold in an oven at 65°C for 9 hours to remove the solvent;

(4) RTM glue injection molding, demoulding after curing, fixing with clamps after demoulding, and then further drying, moisture-proof treatment, and product remainder processing to obtain components.

Example 5

The only difference between this embodiment and Embodiment 1 is that the thickness of the basalt wool fiber preform used in this embodiment is 50 mm, and the component is obtained after processing.

Example 6

The only difference between this embodiment and Embodiment 1 is that the thickness of the basalt wool fiber preform used in this embodiment is 2 mm, and the component is obtained after processing.

Example 7

The only difference between this embodiment and Embodiment 1 is that the amount of glue sprayed each time in step (2) of this embodiment is 600 mL/m ³ , and the component is obtained after processing.

Example 8

The only difference between this embodiment and Embodiment 1 is that the amount of glue sprayed each time in step (2) of this embodiment is 50 mL/m ³ , and the component is obtained after processing.

Example 9

The only difference between this embodiment and Embodiment 1 is that in step (1) of this embodiment, the silica sol and water are mixed and dispersed at a mass to volume ratio of 1:150, and the component is obtained after processing.

Example 10

The only difference between this embodiment and Embodiment 1 is that in step (1) of this embodiment, the silica sol and water are mixed and dispersed at a mass to volume ratio of 1:0.5, and the component is obtained after processing.

Example 11

The difference between this embodiment and Embodiment 1 is that in step (2) of this embodiment, the formed basalt wool fiber preform is used, and there is no need to lay it. Only 5 times of glue spraying are performed, and the component is obtained after final processing.

Comparative example 1

The only difference between this comparative example and Example 1 is that this comparative example does not use glue to pretreat the basalt wool fiber preform, that is, it does not include the glue spraying process in steps (1) and (2).

The components provided in the above-mentioned Examples 1-11 and Comparative Example 1 were subjected to profile testing. The test method was to directly measure the change amount of the profiled wrinkles and the profile accuracy. Among them, "≯" means no greater 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 component type variables prepared by the method provided in Examples 1-3 are lower, the precision is higher, and net-size molded components with better performance can be obtained. In Example 4, the resin ratio is low and the effect on deformation change is not obvious.

In Example 5, due to the excessive thickness, the excessive thickness leads to uneven impregnation and poor profile accuracy; in Example 6, due to the thin thickness, the glue easily penetrates the prefabricated body, affecting the stress within the prefabricated body and causing deviations in the profile.

In Example 7, the amount of glue sprayed was too high, causing the surface layer to be too hard and unable to cope with the micro-extrusion generated during the mold closing process, resulting in larger wrinkles. In Example 8, the amount of glue sprayed is too low, resulting in insufficient bonding force between fibers and easy deformation of the profile.

In Example 9 and Example 10, there is the same problem of resin content, which leads to larger deformation and reduced wrinkle accuracy.

Comparative Example 1 does not include the glue molding process, so the shape changes greatly and the accuracy is reduced.

Finally, it should be noted that the above embodiments are only used 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, those of ordinary skill in the art should understand that it can still be used Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent substitutions are made to some of the technical features; however, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (6)

1. A method for net-size molding of low-density fiber-reinforced material components suitable for RTM technology, characterized in that: the method includes the following steps: (1) Mix glue raw materials and solvent to form glue; (2) Spray the glue obtained in step (1) onto the fiber preform, and then spread and semi-dry; (3) Repeat step (2) for glue spraying 1 to 20 times and step (2) for spreading 0 to 20 times to obtain a pretreated fiber reinforcement; (4) Embed the pretreated fiber reinforcement obtained in step (3) into the mold, and after polishing and drying, the component is obtained by injection molding through the RTM process, curing and demoulding, and drying and moisture-proofing; The glue raw material in step (1) is resin or precursor; The resin includes any one or a combination of at least two of epoxy resin, polyimide resin, phenolic resin, vinyl ester resin or silicone resin; The precursor includes any one or a combination of at least two of siloxane, silica sol or aluminum sol; The ratio of glue raw materials and solvents described in step (1) is 1:(1~100); The thickness of the fiber preform in step (2) is 5 to 40 mm; The amount of glue sprayed in step (2) is 100-500mL/m ³ ; The semi-drying temperature in step (2) is 30-50°C; The half-drying time described in step (2) is 10 to 30 minutes. 2. The method according to claim 1, characterized in that: The solvent described in step (1) is a solvent with a boiling point higher than 50°C. 3. The method according to claim 2, characterized in that: The solvent includes water and/or ethanol. 4. The method according to claim 1, characterized in that: the material of the fiber preform in step (2) includes any of organic fiber needle felt, inorganic fiber needle felt, organic fiber cloth or inorganic fiber cloth. One or a combination of at least two. 5. The method according to claim 1, characterized in that: the drying time in step (4) is 2 to 10 hours and the drying temperature does not exceed the boiling point of the solvent. 6. The method according to any one of claims 1-5, characterized in that: the method includes the following steps: (1) Mix the glue raw materials and the solvent at a ratio of 1: (1 to 100) to form a glue, in which the glue raw materials include resin or precursor, the solvent includes water and/or ethanol, and the glue raw materials and solvent are Ratio is the ratio of mass to volume; (2) Spray the glue obtained in step (1) onto a fiber preform with a thickness of 5 to 40 mm, and then spread and semi-dry the glue. The glue spray volume is 100 to 500 mL/m ³ , and the semi-dried The temperature is 30~50℃ and the time is 10~30min; (3) Repeat step (2) for glue spraying 1 to 20 times and step (2) for spreading 0 to 20 times to obtain a pretreated fiber reinforcement; (4) Embed the pretreated fiber reinforcement obtained in step (3) into the mold, grind and dry it for 2 to 10 hours and the drying temperature does not exceed the boiling point of the solvent, then use the RTM process to injection mold, solidify and demould. After demoulding, clamps are used to fix it, and then the components are obtained after drying and moisture-proofing.