CN116277595A - High-performance thermoplastic prepreg infiltration mold and application method thereof - Google Patents

Abstract

The invention relates to the field of B29B11/10, in particular to a high-performance thermoplastic prepreg infiltration mold and a use method thereof. The resin pressure of the infiltration mold directly comes from the pressure of the melt pump, and the pressure directly acts on the fiber without indirectly increasing the resin pressure by increasing the fiber tension, so that the infiltration pressure can be increased under the effect of ensuring smaller fiber tension, thereby ensuring smaller fiber damage, realizing double-sided impregnation of the fiber in a molten pool, shortening the resin infiltration stroke, improving the infiltration efficiency from another aspect and reducing the pore content of the prepreg.

Description

High-performance thermoplastic prepreg infiltration mold and application method thereof

Technical Field

The invention relates to the field of B29B11/10, in particular to a high-performance thermoplastic prepreg infiltration mold and a using method thereof.

Background

Compared with the metal material, the resin-based composite material has the advantages of high specific strength and high specific modulus, the thermosetting composite material is used in many cases at present, and compared with the thermosetting composite material, the high-performance thermoplastic composite material has the advantages of good impact toughness, fatigue resistance, repairability and the like, and meanwhile, the low-cost automatic manufacturing of the composite material can be realized through an automatic laying in-situ forming process. The thermoplastic prepreg is an intermediate material for preparing a thermoplastic composite material, and the high-performance thermoplastic prepreg takes high-performance thermoplastic resin (such as Polyaryletherketone (PAEK) resin) as a matrix, continuous fibers (such as carbon fibers) as reinforcements, and continuous sheets with a certain thickness (0.1 mm-1 mm) and resin content (30% -50%), and the thermoplastic prepreg is required to have extremely low pore content and less fiber damage in an in-situ molding process. However, high performance thermoplastic resins typically have a relatively high melting temperature (e.g., 343 ℃ for polyetheretherketone (PEEK, one of PAEKs)) and a relatively high melt viscosity (typically greater than 300pa·s), and hot melt processes are typically used to prepare high performance thermoplastic prepregs by subjecting the resin to pressure for a period of time sufficient to wet the resin into the fibers. However, due to the high viscosity of the resin, the resin is difficult to fully infiltrate the fibers in a limited infiltration time, so that more pore defects exist in the prepared prepreg, and when the pressure is increased, the prepreg is severely damaged, and the prepreg is cracked.

The presoaking process of the continuous fiber reinforced high-performance thermoplastic composite materials in the prior art generally comprises a melting infiltration method, a slurry method, a powder infiltration method and the like. The method is characterized in that the resin is heated and melted and then is soaked into fiber bundles in a mold, so that the resin is fully soaked into fibers, the hot melting method is characterized in that the design of the soaking mold is simple to operate, the resin content is easy to control, the resin is difficult to fully soak fibers, particularly the resin with higher viscosity, the problems of high pore content, serious fiber damage, low mechanical property of materials, easiness in cracking of the prepreg and the like are caused. In the slurry method, high-performance thermoplastic resin (such as PEEK) is difficult to dissolve in common organic solvents, resin powder can be dispersed in a gum dipping system, continuous carbon fibers are oriented through rollers, the resin powder is attached to the surfaces of the fibers through the gum dipping system under the action of a traction system, the resin enters the fiber bundles under the action of the pressure of the rollers, and finally, the winding is completed by heating and shaping. In addition, before the carbon fiber enters the heating system, the upper surface and the lower surface can be covered with a release film to prevent the resin powder from falling off, and the release film is peeled off after the heating is finished. The powder suspension technology has the advantages of short residence time of the resin in a molten state, small weight loss, high infiltration efficiency and low cost, and is suitable for mass production. However, if the dispersant is not completely removed, the properties of the product are affected to some extent, and the technique requires a high particle size of the resin powder. In the powder method, the resin is firstly required to be made into tiny resin powder, the fiber is dispersed, the resin powder is adsorbed on the surface of the carbon fiber through the electrostatic action, and then the resin is melted through a high-temperature box to obtain the prepreg. By means of electrostatic adsorption, the high viscosity of the resin does not affect the adsorptivity, so that the infiltration effect is not affected. The powder method can accurately control the resin content, has good infiltration effect and small damage to fibers, but requires small particle size of the resin powder, so that the manufacturing cost is high.

Through the analysis, the thermoplastic prepreg prepared by the different methods is beneficial and disadvantageous, and the aim is that the thermoplastic prepreg prepared by the melt infiltration method is generally considered to be the simplest and most commonly used method, but the problem of the thermoplastic prepreg prepared by the melt infiltration method is also a main factor limiting the popularization and application of the thermoplastic composite material.

Patent US11118292 describes a infiltration mold which is supplied with resin from above and employs a dendritic resin runner to allow uniform distribution of the resin in the width direction of the prepreg, but does not describe how to ensure adequate infiltration of the resin into the fibers and how to reduce prepreg cracking problems.

Patent CN105904611B describes an ultrathin continuous fiber reinforced thermoplastic resin prepreg and a preparation method thereof, the method is to utilize secondary infiltration to realize full infiltration of resin and fiber, a secondary infiltration module comprises a front high-temperature heating roller, a rear high-temperature heating roller and a small arc-shaped hot plate between the two, the secondary infiltration method is adopted to make equipment more complex, the resin and the fiber are difficult to completely infiltrate, the resin content and the prepreg crack are difficult to control, and fiber damage cannot be avoided.

Patent CN110142892a discloses a long fiber reinforced thermoplastic composite material infiltration mold and infiltration process, by adopting a liftable upper press roller combined with a static lower press roller, resin overflow holes for providing resin are arranged on the contact surfaces of the upper press roller and the lower press roller with fibers, and the infiltration efficiency and effect of the fibers can be improved by continuously and uniformly adding the resin overflow holes on the press rollers. The invention is mainly used for preparing long fiber reinforced thermoplastic composite materials, but not continuous fiber reinforced plastic prepregs, and has the main function of rapidly cleaning residual resin in a die, and can improve the infiltration degree, but can not be used for producing continuous fiber reinforced thermoplastic prepregs with extremely low pore content requirements.

Patent CN111267374a discloses a novel fiber tension adjustable thermoplastic composite material impregnating device, the device is provided with a die, a shell body can mechanically move up and down, and the tension of a fiber bundle is adjusted, so that the fiber impregnating effect is changed, however, for polyether-ether-ketone thermoplastic resin, the fiber tension is only adjusted, the resin is difficult to fully infiltrate into the fiber, and the purpose of preparing the prepreg with low pore content can be realized only by comprehensively adjusting the fiber tension, the resin pressure, the impregnating time and the like.

Patent CN113043568B discloses a prepreg hot-melt infiltration mold, which further comprises a preheating mold at the inlet side and a transition die lip at the outlet side for insulating the prepreg, wherein the mold utilizes the combination of a cone shape and a wave shape to make the extrusion force of a fiber wave crest from small to large, thereby facilitating the melt infiltration of the fiber and plastic resin and reducing the abrasion damage of the fiber and the mold. However, this mold does not solve the problem of cracking in the continuous production of prepregs.

Patent CN206551304U discloses a continuous fiber reinforced plastic infiltration mold, the inside of the mold is provided with four cylindrical pins, and the part of each cylindrical pin in the mold cavity is of a bending structure, the bending directions of the first two cylindrical pins are the same as , the bending directions of the second two circular operation pins are the same, and the bending directions of the first two cylindrical pins and the bending directions of the second two cylindrical pins are in symmetrical structure arrangement. The fiber bundles are sequentially contacted with the four bending structures from left to right, the contact surface is an arc surface, the unfolding width of the fiber yarn bundles can be increased, the adjacent fibers can be expanded mutually, the curvature of the contact surface of the continuous fiber yarn bundles and the cylindrical pins can be adjusted, and the fiber dispersing effect can be improved. The disadvantage of this invention is that the bundles may be bunched (the bundles slip to both sides) on the curved cylindrical pins, thus making the prepreg crack more severe.

Through the analysis, the prior art focuses on how to improve the wettability of the resin to the fibers, but omits the problems of low damage to the fibers, no cracking of the prepreg and the like while improving the wettability of the resin to the fibers, and in fact, the problems are common problems of the high-performance thermoplastic prepreg at present, namely (1) the resin cannot fully infiltrate the fibers; (2) The fiber damage is serious, the prepreg is cracked seriously, and the high-quality prepreg cannot be continuously and stably produced; (3) non-uniform fiber distribution in the prepreg.

Disclosure of Invention

The high-performance thermoplastic prepreg prepared by the hot melting method can cause the resin to hardly infiltrate the fiber completely due to high viscosity of the resin, and the problems of fiber damage, prepreg cracking and the like can occur in the prepreg preparation process, and the following modes can only be adopted for improving the infiltration effect of the resin on the fiber:

(1) And the soaking time is prolonged. Extending the infiltration time is beneficial to increasing the infiltration depth, but this can reduce the production efficiency or lead to excessively long infiltration dies;

(2) The infiltration pressure is increased. Increasing the pressure is beneficial to obtaining a larger infiltration driving force, but for an open infiltration mold, a larger infiltration pressure is difficult to obtain, and a common practice is to use a wavy infiltration mold, but the wavy infiltration mold is limited for increasing the infiltration pressure, if only the increase of the infiltration pressure is pursued, new problems such as serious fiber damage, prepreg cracking and the like are brought about;

(3) The double-sided dipping is adopted, so that the resin stroke in the prepreg can be shortened by half, and the dipping effect can be improved in the same time under the same conditions.

In order to increase the resin impregnation pressure and ensure that the fibers can be improved in degree of impregnation and uniformity of fiber distribution while being low in damage and free from cracking of the prepreg, a first aspect of the present invention provides a high-performance thermoplastic prepreg impregnation die, which comprises an upper die 1, a lower die front part 2 and a lower die rear part 3, wherein the upper die 1 is provided with a die press head 10, the die press head 10 and the lower die front part 2 form a resin molten pool 5, and a resin inlet 7 is arranged below the resin molten pool 5.

The inventor sets up the mould pressure head on the last mould, and the mould pressure head can be with resin molten pool extrusion U-shaped structure, and the mould pressure head pushes down the fibre, and when the molten resin got into the resin molten pool from the resin entry, this pressure was directly acted on the fibre, and great infiltration pressure can make the molten resin infiltrate the fibre more fast, improves the infiltration degree. The molten resin wets the fiber under the action of pressure, and the fiber is tightly attached to the die pressing head above the resin molten pool, so that the fiber is ensured not to be scattered under the action of larger pressure, and damage caused by overlarge tension is avoided, which is an important guarantee that the prepreg is not cracked and the fiber is uniformly distributed. The die pressing head above the resin molten pool presses down the fibers, so that the fibers are completely immersed in the molten resin, the effect of double-sided dipping is indirectly achieved, the dipping stroke of the molten resin can be shortened, the dipping degree is improved, the fibers are completely immersed in the molten resin, and the influence of tiny fluctuation of the resin supply amount on the resin content of the prepreg can be reduced.

As a preferred embodiment, the mould further comprises a mould inlet 8 and a mould outlet 9, the mould inlet 8 having a height which is higher than or equal to the height of the mould outlet 9.

As a preferred embodiment, the upper and lower mold parts 1 and 3 form a wave-shaped resin impregnation zone 11.

The heights of the resin molten pool and the wavy resin infiltration area are lower than those of the mold inlet and the mold outlet, so that molten resin is favorable for filling the mold cavity, and the infiltration effect is improved.

The number of the wavy resin soaking areas is adjusted according to the viscosity of the resin, preferably, the number of the wavy resin soaking areas is 2-20, and more preferably, 5-15.

As a preferred embodiment, each apex of the wavy resin impregnated area 11 has a circular arc shape.

As a preferred embodiment, the upper apex of the wavy resin infusion zone 11 is lower in height than the height of the die inlet 8 and the height of the die outlet 9.

As a preferred embodiment, the resin bath 5 is a U-shaped resin bath.

As a preferred embodiment, each corner of the resin pool 5 is rounded, and the radius of the rounded corner is R5-R10.

Preferably, the radius of the fillet is R5.

As a preferred embodiment, the resin is fed upward into the resin bath 5 from the lower part of the resin inlet 7.

As a preferred embodiment, the inside of the mold is provided with a heating unit and a temperature sensor, and the outside is provided with a heat-insulating component.

The second aspect of the invention provides a use method of a high-performance thermoplastic prepreg infiltration mold, which comprises the following steps:

s1, heating the die to the prepreg processing temperature, and preserving heat;

s2, opening the upper die 1, penetrating the spread fiber from the die inlet 8 and penetrating out from the die outlet 9;

s3, covering the upper die 1, starting the extruder, extruding molten resin into a resin molten pool 5 from a resin inlet 7, and infiltrating fibers;

s4, starting a traction motor to enable the fibers to move along the fiber running direction under the action of the traction motor, fully soaking the fibers by molten resin in the movement process, reducing the temperature outside the die, and solidifying the resin to form the thermoplastic prepreg.

Compared with the prior art, the invention has the following beneficial effects:

(1) Improving the infiltration effect and reducing the fiber damage

According to the analysis, to increase the impregnation effect, only by increasing the impregnation pressure, extending the impregnation time or adopting a double-sided impregnation method, the conventional mold form needs to increase the impregnation pressure, and generally needs to increase the fiber tension, and extending the impregnation time generally means extending the mold length or reducing the rate, and increasing the fiber tension or extending the mold length can seriously damage the fiber, reduce the mechanical properties of the material, and reduce the rate can reduce the production efficiency, which is not beneficial to mass production of prepregs. According to the infiltration mold, the resin pressure is directly from the pressure of the melt pump, and the pressure directly acts on the fibers without indirectly increasing the resin pressure by increasing the fiber tension, so that the infiltration pressure can be increased under the effect of ensuring smaller fiber tension, and smaller fiber damage can be ensured;

(2) Avoid the prepreg from cracking and ensure the uniform distribution of the fibers

In the existing mold form, resin is extruded from a die into the mold, and as the resin passes through the fibers, the fibers that have been spread may be spread by the resin, forming gaps that may not only lead to cracking of the prepreg, but also to uneven distribution of the fibers in the width direction of the prepreg. In the mold, the fibers are tightly attached to the mold pressure head at the place where the resin applies pressure, so that the fibers have certain constraint force in the width direction and cannot be scattered by the resin, the cracking of the prepreg can be avoided, and the uniform distribution of the fibers in the width direction of the prepreg can be ensured.

Drawings

Fig. 1 is a structural diagram of a high-performance thermoplastic prepreg infiltration mold according to the present invention, wherein 1 is an upper mold, 2 is a lower mold front, 3 is a lower mold rear, 4 is a fiber, 5 is a resin pool, 6 is a molten resin, 7 is a resin inlet, 8 is a mold inlet, 9 is a mold outlet, 10 is a mold ram, 11 is a wave-shaped resin infiltration zone, and 12 is a fiber running direction.

Fig. 2 is a cross-sectional view of the carbon fiber reinforced polyetheretherketone prepreg prepared in example 1.

Detailed Description

The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only 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

Referring to fig. 1, the present embodiment provides a preparation method of a carbon fiber reinforced Polyetheretherketone (PEEK) prepreg, which specifically includes the following steps: .

S1, connecting the front part of a lower die of an infiltration die with a resin supply module;

s2, heating the die to the prepreg forming temperature, and preserving heat for 30min;

s3, opening the upper die 1, penetrating the spread fiber from the die inlet 8 and penetrating out from the die outlet 9;

s4, covering the upper die 1, starting the extruder, extruding PEEK resin in a molten state into a resin molten pool 5 from a resin inlet 7, and infiltrating fibers;

s5, starting a traction motor to enable the fibers to move along the fiber running direction under the action of the traction motor, fully soaking the fibers by the PEEK resin in a molten state in the movement process, reducing the temperature outside the die, and solidifying the PEEK resin to form the thermoplastic prepreg.

Performance testing

The thermoplastic prepreg prepared by the infiltration mold and the method has the advantages that the resin content is 35%, the pore content is less than 0.5%, the appearance and the internal quality of the prepreg are good, the cross section of the prepared prepreg is shown in figure 2, a cross section image of the prepreg is shown between two broken lines in the figure, a circular area is a fiber cross section, the rest gray areas are resin matrixes, the pore content of the prepreg is lower (less than 0.5%), the distribution of the resin and the fiber is uniform, the thickness of the prepreg is uniform, and the thickness of the prepreg is between 0.14 and 0.15 mm.

The mechanical properties of the composite material prepared by using the prepreg and adopting an autoclave process are shown in table 1, and as can be seen from table 1, the mechanical properties of the composite material are good.

The resin content test method refers to: HB 7736.5

The pore content testing method refers to: GB/T3365

0 ° tensile strength test method reference: ASTM D3039

The 0 ° flexural strength test method refers to: Q/6S 2708

Interlayer shear strength test method reference: ASTM D2344

Test item	Test results
		Tensile strength at 0 degree	2712MPa
Flexural Strength at 0 degree	1463MPa
		Interlaminar shear Strength	106MPa

While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that various modifications and adaptations can be made without departing from the principles of the present invention, and such modifications and adaptations are intended to be comprehended within the scope of the present invention.

Claims (10)

1. A high-performance thermoplastic prepreg infiltration mold, which comprises an upper mold (1), a lower mold front part (2) and a lower mold rear part (3), and is characterized in that the upper mold (1) is provided with a mold press head (10), the mold press head (10) and the lower mold front part (2) form a resin molten pool (5), and a resin inlet (7) is arranged below the resin molten pool (5).

2. A high performance thermoplastic prepreg infiltration mold according to claim 1, characterized in that the mold further comprises a mold inlet (8) and a mold outlet (9), the height of the mold inlet (8) being higher than or equal to the height of the mold outlet (9).

3. A high performance thermoplastic prepreg infiltration mold as claimed in claim 1, wherein the upper (1) and lower (3) mold rear parts form a wave-shaped resin infiltration zone (11).

4. A high performance thermoplastic prepreg infiltration mold according to claim 3, in which each apex of the undulating resin infiltration region (11) is circular arc-shaped.

5. A high performance thermoplastic prepreg impregnation die according to claim 4, characterized in that the upper apex height of the undulating resin impregnation zone (11) is lower than the height of the die inlet (8) and the height of the die outlet (9).

6. A high performance thermoplastic prepreg infiltration mold as in claim 1, wherein the resin melt pool (5) is a U-shaped resin melt pool.

7. A high performance thermoplastic prepreg infiltration mold as claimed in claim 1, characterized in that each corner of the resin bath (5) is rounded, the radius of the rounded corner being R5-R10.

8. A high performance thermoplastic prepreg infiltration mold as claimed in claim 1, characterized in that the resin is fed up into the resin bath (5) from the lower part of the resin inlet (7).

9. The high-performance thermoplastic prepreg infiltration mold as claimed in claim 1, wherein the mold is internally provided with a heating unit and a temperature sensor, and externally provided with a heat-insulating member.

10. A method of using the high performance thermoplastic prepreg infiltration mold of claim 1, comprising the steps of:

s1, heating the die to the prepreg processing temperature, and preserving heat;

s2, opening the upper die (1), penetrating the fiber subjected to yarn spreading from the die inlet (8) and penetrating out from the die outlet (9);

s3, covering the upper die (1), starting the extruder, extruding molten resin into a resin molten pool (5) from a resin inlet (7), and infiltrating fibers;

s4, starting a traction motor to enable the fibers to move along the fiber running direction under the action of the traction motor, fully soaking the fibers by molten resin in the movement process, reducing the temperature outside the die, and solidifying the resin to form the thermoplastic prepreg.

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