Interlayer toughening method for thermosetting polymer composite material

Abstract

The invention discloses a thermosetting polymer composite material interlayer toughening method which comprises the following steps: at room temperature, mixing a part of resin matrix and thermoplastic resin to prepare a component I; mixing the residual resin matrix with the curing agent and the accelerant to prepare a component II; respectively pouring the two components into a three-roller grinder, continuously grinding for three times, and dispersing and mixing at a high speed to obtain toughened resin; pouring toughened resin into a film coating machine, and uniformly coating release paper with the toughened resin to obtain a toughened resin film; cutting the prepreg and the toughened resin film into the same size; a layer of toughening resin film is laid on the single side of the surface of the prepreg, the prepreg subjected to film pasting sequentially passes through a hot pressing roller of a prepreg machine, and the prepreg subjected to interlayer toughening is obtained. The thermoplastic resin toughening component is used for toughening on the basis of prepreg matrix resin, the problem of resin compatibility is avoided, and the influence of the toughening component on the matrix resin is reduced by adopting a room-temperature mixing mode.

Description

Technical Field

[0001] The invention relates to the technical field of composite materials, and in particular to a method for toughening the interlayers of thermosetting polymer composite materials. Background Art

[0002] Thermosetting composites are the most widely used composite materials. They have high specific strength and high specific stiffness and are widely used in some high-end material application fields, such as aerospace, shipbuilding, wind power energy and other fields.

[0003] There is generally no fiber reinforcement between the layers of composite laminates, and the load is transferred only by the bonding between the thermosetting resin matrix. However, the thermosetting resin itself is brittle, so the strength along the thickness direction and between the layers is low. After being subjected to a low-energy impact, matrix cracks and delamination damage will occur inside the laminate structure. This type of damage has very small surface damage and is difficult to observe with the naked eye, but the internal delamination will continue to expand during subsequent use, causing a serious decrease in the strength and stiffness of the composite laminate structure, and has never caused premature failure of related structural performance.

[0004] How to suppress delamination damage and improve the impact damage and delamination resistance of composite laminate structures has always been the focus of research in composite aircraft structure design and analysis. Common methods include matrix toughening and laminate sewing, but these methods may increase the manufacturing cost of composite materials and may also cause losses in other properties.

[0005] Interlaminar toughening is a technology that avoids the above problems. Interlaminar toughening is to add a thin layer of toughening material to the composite laminate to improve the fracture toughness and damage tolerance of the composite. The main research directions at present are nanostructure toughening and thermoplastic resin toughening.

[0006] Nanostructure toughening is achieved through the use of molecular self-assembly technology through nanostructures such as short fibers and carbon nanotubes, but most of them are still in the research stage. There are many problems in terms of processability and dispersibility, and the cost is high, which is not conducive to industrial application.

[0007] Thermoplastic resin toughening is the main method currently used. For example, patent CN108943888A composites thermoplastic resin on an open-pore low-density foam sheet, and directly adds it between carbon fiber plies as an intercalation layer to increase the toughening effect between composite structures; patent CN102505355A sprays thermoplastic resin through solution spinning and deposits it into non-woven fabric, which is then dried to form a fiber nonwoven toughening material, thereby realizing the manufacture of toughened materials.

[0008] Moreover, the distribution of interlayer toughening resin affects the final failure mode of the material. Patent CN101760965A uses thermoplastic toughening agent in powder form and directly fills it in the interlayer space of the composite material. Although the operation is simple, this method is affected by the composite material molding process and has certain requirements on the resin matrix. Therefore, inserting the second phase material layer between the composite material layers in a better form is the focus of the research. Summary of the invention

[0009] In order to solve the above problems, the present invention provides a method for toughening the interlayers of thermosetting polymer composite materials, which uses a thermoplastic resin toughening component for toughening, avoids resin compatibility problems, reduces the influence of the toughening component on the matrix resin, and achieves toughening of the interlayers of the composite material without causing a decrease in other properties.

[0010] To this end, the technical solution of the present invention is: a method for toughening the interlayers of a thermosetting polymer composite material, comprising the following steps:

[0011] 1) Preparation of toughened resin:

[0012] 1.1) Prepare 100 parts of resin matrix, 1.0-6.5 parts of curing agent, 0.5-3.5 parts of accelerator and 10-50 parts of thermoplastic resin, wherein the resin matrix and the prepreg are the same system resin;

[0013] 1.2) At room temperature, a portion of the resin matrix and the thermoplastic resin are mixed to prepare component one; the remaining resin matrix is ​​mixed with a curing agent and an accelerator to prepare component two;

[0014] 1.3) Pour component 1 and component 2 into a three-roll mill respectively and grind them three times continuously;

[0015] 1.4) Dispersing and mixing the ground component 1 and component 2 at high speed to obtain a toughened resin;

[0016] 2) pouring the toughening resin into a coating machine, and evenly coating the toughening resin on the release paper to obtain a toughening resin film;

[0017] 3) Preparing prepreg, cutting the prepreg and toughening resin film into the same size;

[0018] 4) Lay a layer of toughening resin film on one side of the prepreg surface, and pass the prepregs with film pasting through the hot pressing rollers of the prepreg machine one by one, and the gap between the hot pressing rollers gradually becomes smaller;

[0019] 5) Laying the prepreg-toughened resin layer-prepreg is performed to obtain a prepreg with interlayer toughening.

[0020] On the basis of the above scheme and as a preferred scheme of the above scheme: if the prepreg is an epoxy resin system, the resin matrix is ​​epoxy resin, or if the prepreg is a bismaleimide resin system, the resin matrix is ​​bismaleimide resin.

[0021] On the basis of the above scheme and as a preferred scheme of the above scheme: the thermoplastic resin is a mixture of one or more of polysulfone, polyethersulfone and polyetherketone, and the particle size of the thermoplastic resin is 65-80 μm.

[0022] On the basis of the above scheme and as a preferred scheme of the above scheme: in the step 1.2), 80 parts of the resin matrix and the thermoplastic resin are mixed to prepare component one; the remaining 20 parts of the resin matrix are mixed with the curing agent and the accelerator to prepare component two.

[0023] On the basis of the above scheme and as a preferred scheme of the above scheme: in the step 2), after the toughening resin is evenly applied to the release paper, a layer of PE film is added on the surface and then rolled up.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. Based on the idea of ​​off-site toughening, a thermoplastic resin toughening component is used on the basis of the prepreg matrix resin for toughening to avoid resin compatibility problems. At the same time, the toughened resin matrix is ​​prepared by room temperature mixing to reduce the influence of the toughening component on the matrix resin, so as to achieve interlayer toughening of the composite material without causing a decrease in other properties.

[0026] 2. The toughening resin is prepared by mixing at room temperature, which can avoid the concentration of the toughening component being too high after heating and dissolving, reduce the migration of components due to concentration differences, and thus ensure the performance of the prepreg matrix resin and its composite materials.

[0027] 3. Prepare toughening resin according to the prepreg matrix resin system. Resins of the same system are beneficial to the internal molding quality of the laminate, achieve the effect of interlayer toughening, and will not affect other properties of the composite material.

[0028] 4. Use a coating machine to prepare a film with uniform thickness. The molding quality of the film affects the distribution of the toughening components. The toughened film should be stably controlled at 20g / m 2 The film form can realize the designability of the laminate structure, and the operation is simple, which is conducive to the industrial use of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram of the preparation process of the toughened adhesive film of the present invention;

[0030] Figure 2 This is the surface image of the untoughened prepreg;

[0031] Figure 3 Surface diagram of toughened prepreg.

[0032] Marked in the figure are: release paper 1, first feeding roller 2, feeding roller 3, toughening resin 4, second feeding roller 5, PE film 6, and winding roller 7. DETAILED DESCRIPTION

[0033] In the description of the present invention, it should be noted that directional words, such as the terms "center", "lateral (X)", "longitudinal (Y)", "vertical (Z)", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating directions and positional relationships are based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of narrating the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and cannot be understood as limiting the specific scope of protection of the present invention.

[0034] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. Therefore, the definition of "first" and "second" features can explicitly or implicitly include one or more of the features. In the description of the present invention, "several" and "a number" mean two or more, unless otherwise clearly and specifically defined.

[0035] Example 1

[0036] The method for toughening the interlayers of a thermosetting polymer composite material described in this embodiment comprises the following steps:

[0037] 1) Preparation of toughened resin:

[0038] 1.1) Prepare 100 parts of epoxy resin, 4 parts of curing agent, 1.5 parts of accelerator and 30 parts of polyethersulfone;

[0039] 1.2) Mix 80 parts of epoxy resin and 30 parts of polyethersulfone at room temperature to prepare component one, and mix 20 parts of epoxy resin with 4 parts of curing agent and 1.5 parts of accelerator to prepare component two;

[0040] 1.3) Pour component 1 and component 2 into a three-roll mill respectively and grind them three times continuously;

[0041] 1.4) The ground components 1 and 2 are dispersed and mixed uniformly at high speed to obtain a toughened resin.

[0042] 2) Pour the toughened resin into the coating machine. When the temperature is about 60°C and the resin viscosity is maintained at about 20 Pa.s, quickly coat the film and evenly coat the toughened resin on the release paper. The film surface density is 20g / m 2 ; Add a layer of PE film on the surface and then roll it up. Figure 1 As shown, the release paper 1 is fed in from the first feeding roller 2, with a feeding roller 3 in the middle, and a toughening resin 4 is added in the middle of the feeding roller 3 so that the toughening resin 4 is spread flat on the release paper 1, and then a PE film 6 is fed in from the second feeding roller 5, and the PE film 6 is spread on the surface of the toughening resin 4, and finally rolled up by the winding roller 7.

[0043] 3) Prepare a T300 grade epoxy prepreg and cut the prepreg and toughened resin film into the same size;

[0044] 4) A layer of toughening resin film is laid on one side of the prepreg surface, and the prepreg with film is passed through the hot pressing rollers of the prepreg machine at 40°C one by one, and the gap between the hot pressing rollers gradually becomes smaller to obtain the prepreg with film toughening.

[0045] at the same time, Figure 2 This is the surface diagram of the untoughened prepreg. Figure 3 To toughen the prepreg surface, at room temperature, a film made of toughened resin is attached to the prepreg surface through a steel roller of an impregnation machine. Figure 3 It can be seen that the toughening film attached to the surface of the prepreg has toughening components evenly distributed on the surface of the prepreg, and can form an ideal phase separation structure during the curing process to achieve the specified toughening effect.

[0046] Example 2

[0047] The prepreg obtained in Example 1 after film lamination was used to prepare tensile, compression and post-impact compression test pieces according to the plying specified by the American standard, and was cured and formed in an autoclave. The entire molding process was evacuated to 0.095 MPa, pressurized to 0.3 MPa, raised from room temperature to 80°C, and kept warm for 60 minutes, then raised to 120°C, kept warm for 120 minutes, and finally naturally cooled to below 60°C, released the pressure, and taken out of the autoclave to finally obtain the toughened prepreg test piece.

[0048] Comparative Example 1

[0049] Take T300-grade epoxy prepreg of the same specification, prepare tensile, compression and post-impact compression test pieces according to the layup specified by the American standard, and cure and mold in an autoclave. The entire molding process is vacuumed to 0.095MPa, pressurized to 0.3MPa, raised from room temperature to 80℃, kept warm for 60min, then raised to 120℃, kept warm for 120min, and finally naturally cooled to below 60℃, released the pressure, and taken out of the autoclave to finally obtain the untoughened prepreg test piece.

[0050] The toughened prepreg test piece prepared in Example 2 and the untoughened prepreg test piece prepared in Comparative Example 1 were subjected to corresponding mechanical property tests, and the results are shown in Table 1. The results show that the 0° tensile strength and 0° compressive strength of the toughened composite material are not much different, the 0° tensile modulus and 0° compressive modulus are reduced, and the compressive strength after impact is increased by about 15%.

[0051] Table 1

[0052] Test Project After toughening Before toughening Test Standards 0° tensile strength / MPa 908 925 ASTMD3039 0° tensile modulus / GPa 58.8 62.3 ASTMD3039 0° compression strength / MPa 495 506 ASTMD6641 0° compression modulus / GPa 51.2 56.0 ASTMD6641 Compression strength after impact / MPa 262 223 ASTMD7136 / 7137

[0053] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for toughening interlayers of thermosetting polymer composite materials, characterized in that: The following steps are involved: 1) Preparation of toughened resin: 1.1) Prepare 100 parts of resin matrix, 1.0-6.5 parts of curing agent, 0.5-3.5 parts of accelerator and 10-50 parts of thermoplastic resin, wherein the resin matrix and the prepreg are the same system resin; 1.2) At room temperature, a portion of the resin matrix and the thermoplastic resin are mixed to prepare component one; the remaining resin matrix is ​​mixed with a curing agent and an accelerator to prepare component two; 1.3) Pour component 1 and component 2 into a three-roll mill respectively and grind them three times continuously; 1.4) Dispersing and mixing the ground component 1 and component 2 at high speed to obtain a toughened resin; 2) pouring the toughening resin into a coating machine, and evenly coating the toughening resin on the release paper to obtain a toughening resin film; 3) Preparing prepreg, cutting the prepreg and toughening resin film into the same size; 4) Lay a layer of toughening resin film on one side of the prepreg surface, and pass the prepregs with film pasting through the hot pressing rollers of the prepreg machine one by one, and the gap between the hot pressing rollers gradually becomes smaller; 5) Laying the prepreg-toughened resin layer-prepreg is performed to obtain a prepreg with interlayer toughening.

2. The method for toughening the interlayers of a thermosetting polymer composite material according to claim 1, characterized in that: If the prepreg is an epoxy resin system, the resin matrix is ​​epoxy resin; or if the prepreg is a bismaleimide resin system, the resin matrix is ​​bismaleimide resin.

3. The method for toughening the interlayers of a thermosetting polymer composite material according to claim 1, characterized in that: The thermoplastic resin is a mixture of one or more of polysulfone, polyethersulfone and polyetherketone, and the particle size of the thermoplastic resin is 65-80 μm.

4. The method for toughening the interlayers of a thermosetting polymer composite material according to claim 1, characterized in that: In the step 1.2), 80 parts of the resin matrix and the thermoplastic resin are mixed to prepare component one; and the remaining 20 parts of the resin matrix and the curing agent and the accelerator are mixed to prepare component two.

5. The method for toughening the interlayers of a thermosetting polymer composite material according to claim 1, characterized in that: In the step 2), after the toughening resin is evenly applied to the release paper, a layer of PE film is added on the surface and then rolled up.

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