Method for improving interface performance of aramid fiber laminated plate composite material through high-temperature pretreatment

Abstract

The invention provides a method for improving the interface performance of an aramid fiber laminate composite material through high-temperature pretreatment and a preparation process of the aramid fiber laminate composite material, and relates to the field of performance improvement of composite materials. Comprising the following steps: S1, heating aramid fibers at 150-300 DEG C for 3-15 minutes, and immediately taking out the aramid fibers; s2, fully and uniformly coating epoxy resin on the aramid fiber obtained in the step S1; and S3, carrying out molding treatment on the aramid fiber obtained in S2 to obtain the aramid fiber composite material with improved interface performance. The simple high-temperature pretreatment method is adopted, the number of polar functional groups on the surface of the aramid fiber is increased, the resin impregnation degree of the aramid fiber and the bonding performance between fiber-resin interfaces are improved, and the interlaminar shear strength of the composite material is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material performance improvement, and in particular to a method for improving the interface performance of aramid fiber laminate composite materials through high-temperature pretreatment. Background Art

[0002] Fiber-reinforced polymer-based composites are widely used in aerospace, automotive, civil engineering, and sports equipment due to their excellent properties such as light weight, high strength, and corrosion resistance. Aramid fiber has the characteristics of high strength, high modulus, low density, and high temperature resistance, making it an ideal reinforcement phase for the preparation of high-performance fiber-reinforced composites. The high crystallinity and dense hydrogen bond network of aramid fiber give it excellent mechanical properties and chemical stability, but also make its surface smooth and chemically inert, making it difficult to form a good interface with the resin matrix. These characteristics limit the performance of aramid fiber composites. Pretreatment of the fiber can effectively improve the fiber-resin interface performance.

[0003] At present, the main method for improving the interfacial properties of aramid composite materials is through fiber modification. The existing modification methods are mainly divided into the following four categories: (1) physical modification methods, including plasma activation treatment, ultraviolet radiation treatment and ultrasonic treatment; (2) chemical modification methods, covering surface hydrolysis in acid / alkali media, direct fluorination treatment and chemical grafting; (3) nanostructure modification methods, involving carbon nanotube deposition, metal oxide nanoparticles and inorganic nanoparticles surface loading technology; (4) functional coating treatment methods.

[0004] Although existing methods can improve the interfacial properties of aramid composites to varying degrees under laboratory conditions, most of them rely on complex chemical reagents, long-term treatment or multi-step processes, and have problems such as damage to the fiber surface structure, high cost, and poor environmental friendliness. Therefore, a simple and economical fiber processing method is urgently needed. Summary of the Invention

[0005] This invention addresses the problem of insufficient fiber-resin interface performance in the prior art and aims to provide a simple and economical high-temperature pretreatment method that can significantly improve the interface bonding strength and overall performance of the composite material. Specifically: A method for improving the interfacial properties of aramid fiber composite materials by high-temperature pretreatment, comprising: Step S1, heating the aramid fiber at 150-300° C. for 3-15 minutes and then immediately taking it out; Step S2, fully and evenly coating the aramid fiber obtained in S1 with epoxy resin; Step S3: molding the aramid fiber / resin mixture obtained in S2 to obtain an aramid fiber composite material with improved interface performance.

[0006] Preferably, in step S1, the aramid fiber is selected from fiber precursors or fabrics composed of precursors.

[0007] Preferably, in step S1, the aramid fibers are selected from a single-layer fabric or a composite structure multi-layer aramid fabric formed by stacking in different orientations.

[0008] Preferably, in step S1, the heating temperature is 150-240°C.

[0009] Preferably, in step S1, the heating time is 5-10 minutes.

[0010] Preferably, in step S3, the aramid fiber laminate composite material is formed by a molding method selected from hot pressing molding, vacuum infusion molding, hand lay-up molding or pultrusion molding.

[0011] Preferably, in step S3, when the molding method is hot pressing, the hot pressing equipment is a servo hot press; the hot pressing pressure is 1.0-1.5 MPa, the hot pressing temperature is 80-200°C, the heating rate is 1-5°C / min, and the entire hot pressing process lasts 60-180 minutes (i.e., from the start of heating to the end). Obviously, different resin systems will have different hot pressing temperature parameters and hot pressing time, and those skilled in the art can further optimize and adjust them based on this.

[0012] Preferably, the present invention also obtains an aramid fiber laminate composite material with improved interface performance.

[0013] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least: The present invention significantly improves the interlaminar mechanical properties of aramid fibers by adopting a simple method of pre-treating aramid fibers by heating them before molding, and further controlling the process conditions during the pre-treatment process. The method of the present invention is simple and can be used as a pre-process for any aramid fiber laminate composite material molding method without the need for complex methods and chemical reagents, thereby effectively solving the problem of insufficient fiber-resin interface performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0015] Figure 1 This is a comparison chart of the interlaminar shear strength of different aramid fiber composite materials of the present invention.

[0016] Figure 2This is a diagram showing the changes in element content of the aramid II fiber precursor of the present invention at different holding temperatures, wherein (a) represents carbon, (b) represents nitrogen, and (c) represents oxygen. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0018] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as an "exemplary" in the present invention should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplary" is intended to present concepts in a concrete manner. Furthermore, in the embodiments of the present invention, "and / or" can mean both or either of the two.

[0019] In the embodiments of the present invention, "image" and "picture" may sometimes be used interchangeably. It should be noted that, when the distinction between them is not emphasized, the meanings they convey are the same. "of," "corresponding," and "corresponding" may sometimes be used interchangeably. It should be noted that, when the distinction between them is not emphasized, the meanings they convey are the same.

[0020] In the embodiments of the present invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript form such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0021] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0022] Example 1

[0023] Cut the aramid II fiber unidirectional fabric into 300mm 300mm, placed in a constant temperature oven at 180℃ for 15 minutes, then removed and allowed to cool. The epoxy resin system was evenly applied to the high-temperature pretreated aramid fiber fabric. Then, unidirectional aramid fiber laminates were made, with 6 layers of fiber fabric per board. Placed in a mold sprayed with a release agent, it was placed in a servo hot press. The pressure was set to 1.2MPa, and the curing process was carried out according to the process of 150℃ / 180min and the heating temperature was increased by 5℃ / min. After cooling to room temperature in the hot press, the mold was removed to obtain the aramid fiber composite material.

[0024] Comparative Example 1

[0025] Cut the aramid II fiber unidirectional fabric into 300mm 300mm, evenly apply the epoxy resin system to untreated aramid fiber fabric. Then, create unidirectional aramid fiber laminates, with six layers of fabric per panel. Place the laminate in a mold sprayed with a release agent and place it in a servo hot press. Set the pressure to 1.2MPa and cure at 150°C / 180min, increasing the temperature by 5°C / min. Allow the laminate to cool to room temperature in the hot press and then demold to obtain the aramid fiber composite material.

[0026] Interlaminar shear strength test

[0027] The interlaminar shear performance test of the aramid fiber composite material prepared in Example 1 was carried out. According to the standard ASTM D2344, the fiber composite board was cut into 5 pieces with a length of 18 mm along the fiber direction. 6mm 3mm test specimens were tested for interlaminar properties using a servo universal testing machine with a 12mm support span, at a loading rate of 1.0mm / min. According to the standard, the average of the test results was used as the interlaminar shear strength. The interlaminar shear strength of the prepared aramid fiber composite was measured to be 39.88MPa.

[0028] The aramid fiber composite material prepared in Comparative Example 1 was subjected to interlaminar shear performance testing using the same method, and the interlaminar shear strength was measured to be 14.87 MPa.

[0029] In-situ XPS testing

[0030] In-situ heating X-ray photoelectron spectroscopy (XPS) characterization test was carried out on aramid II fiber precursor. Four characteristic temperature points were selected, namely room temperature (about 25℃), 150℃, 180℃ and 240℃, and kept warm for 10 minutes for surface element scanning analysis. The evolution law of atomic concentration distribution was obtained as follows: Figure 2 As shown. The results show that as the temperature increases, the proportion of carbon begins to decrease, reaching the lowest proportion at 180°C. When the temperature continues to rise to 240°C, the proportion of carbon recovers, but is still lower than the normal temperature environment. The change pattern of nitrogen and oxygen elements is opposite to that of carbon. The proportion of elements continues to increase from room temperature to 180°C, and decreases slightly when the temperature rises to 240°C but is higher than the result at room temperature. The increase in the proportion of nitrogen and oxygen elements indicates that more polar functional groups containing nitrogen / oxygen elements appear on the fiber surface. These functional groups can increase the impregnation degree of the resin and form a strong interfacial bond with the resin matrix, thereby improving the interlaminar performance of the aramid fiber laminate composite material.

[0031] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for improving the interface properties of aramid fiber laminate composite materials by high temperature pretreatment, characterized in that: include: Step S1, heating the aramid fiber at 150-300° C. for 3-15 minutes and then immediately taking it out; Step S2, fully and evenly coating the aramid fiber obtained in S1 with epoxy resin; Step S3: molding the aramid fiber / resin mixture obtained in S2 to obtain an aramid fiber laminate composite material with improved interface performance.

2. The method according to claim 1, characterized in that In step S1, the aramid fiber material is selected from one of the following forms: aramid fiber precursor or a fabric composed of aramid fiber precursor.

3. The method according to claim 1, characterized in that In step S3, the aramid fiber laminate composite material is formed by a molding method selected from hot pressing molding, vacuum infusion molding, hand lay-up molding or pultrusion molding.

4. The method according to claim 3, characterized in that In step S3, when the forming method is hot pressing, the hot pressing equipment is a servo hot press.

5. Aramid fiber composite material obtained by the method according to any one of claims 1 to 4.

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