CN115723390A - An electrothermal composite material based on a nickel-chromium alloy wire weft-knitted structure and its preparation method - Google Patents

Abstract

The invention belongs to the field of textile composite materials, and particularly relates to an electrothermal composite material based on a nichrome wire weft knitting structure and a preparation method thereof. The structure is a five-layer structure and sequentially comprises a first composite structure layer, an adhesive film layer, an electric heating fabric layer, an adhesive film layer and a second composite structure layer; a symmetrical structure with the electrically heated fabric layer as the center in the thickness direction. The electric heating fabric layer comprises nichrome wires, terylene and aramid fibers, adhesive films are attached to the upper surface and the lower surface of the electric heating fabric layer, then glass fiber/epoxy prepreg with different laying angles is laid to form a multilayer structure, the multilayer structure is vacuumized and compacted, and the multilayer structure is placed into an autoclave to be heated and cured, so that the electric heating composite material based on the weft knitting structure is obtained. The electric heating composite material can be applied to the engineering field with electric heating requirements, such as helicopter air inlet channel anti-icing, and not only can meet the mechanical property requirements of a bearing structure, but also can provide effective heating efficiency and balance temperature.

Description

An electrothermal composite material based on a nickel-chromium alloy wire weft-knitted structure and its preparation method

technical field

The invention belongs to the field of textile composite materials, and in particular relates to an electrothermal composite material based on a nickel-chromium alloy weft-knitted structure and a preparation method thereof.

Background technique

Electrothermal anti-icing is an anti-icing method commonly used in rotorcraft engine intake ducts, tail fins and windshields. The basic principle is to convert electrical energy into heat energy through the heating element on the inner surface of the anti-icing material, and the heat is conducted to the surface of the component to increase the temperature. In order to achieve the purpose of anti-icing. Although electric heating anti-icing technology is one of the most reliable anti-icing technologies, it still has defects such as high power consumption, large thermal inertia, and repeated icing, and a series of key technical difficulties need to be overcome. In order to solve the above problems, fast thermal response, light-weight electrically heated fabrics and their composite materials are applied in electrically heated anti-icing technology.

In the context of the demand for rotorcraft lightweight technology, it is an inevitable trend for composite materials to simultaneously achieve structural performance and electrothermal functions. Electrothermal composites are advanced composite materials containing electric heating elements, ideal for rotorcraft composites.

Electrothermal composite materials are mostly fiber-reinforced composite materials, which are generally multi-layer structures made of many single-layer materials bonded together. Since the thermal and mechanical properties of the reinforcing fiber in different directions in the composite material layer are anisotropic in space, the temperature distribution is uneven during operation, and large thermal stress will be generated in and between the layers of the electrothermal anti-icing material, resulting in layer The composite structure is prone to deformation and delamination, so the electrothermal composite material should have good mechanical properties, temperature controllability and heating rate.

Contents of the invention

The invention provides a method for the integrated design and preparation of the structure and function of the electrothermal composite material from the layout design of the nickel-chromium alloy wire, the preparation of the electric heating fabric, to the design and molding of the resin-based composite material.

In order to overcome the problems of low bearing capacity, low heating rate and uneven heat distribution of the existing electrothermal composite materials, the present invention provides an electrothermal composite material based on a weft-knitted structure of nickel-chromium alloy wires and a preparation method thereof.

Technical solutions

An electrothermal composite material based on the weft-knitted structure of nickel-chromium alloy wire, which is a five-layer structure, sequentially composed of the first composite structure layer 1, the adhesive film layer 2, the electric heating fabric layer 3, the adhesive film layer 2, and the second composite structural layer 4. Composition; a symmetrical structure centered on the electric heating fabric layer 3 in the thickness direction.

Further, the electric heating fabric layer 3 includes electric heating elements and insulating fibers, the electric heating elements are nickel-chromium alloy wires, and the size of the nickel-chromium alloy wires is 0.04mm-0.2mm.

Further, the first composite structure layer 1 is composed of 4 layers of plain glass fiber/epoxy prepreg laid according to lay-up angles of 0°, 45°, 0°, and 45° respectively, and the composite structure layer adopts medium-high temperature prepreg Material, this kind of prepreg molding or thermoforming.

Further, the second composite structure layer 4 is composed of 4 layers of plain glass fiber/epoxy prepreg laid at lay-up angles of 45°, 0°, 45°, and 0° respectively.

Further, the adhesive film layer 2 is a medium-high temperature epoxy structural adhesive film, which has the same curing temperature as the resin system used in the first composite structural layer 1 and the second composite structural layer 4 .

Further, the heating of the electrically heated fabric layer 3 applies current to the tip of the reserved nickel-chromium alloy wire, and the metal wire passes current to generate Joule heat, and the surface temperature of the fabric changes.

Further, the fabric structure of the electric heating fabric layer 3 is plain stitch, rib weave, double rib weave.

Further, the nickel-chromium alloy wire and the polyester or aramid fiber are fed into a computerized flat knitting machine in parallel for weaving together, and the nickel-chromium alloy wire is placed inside the fabric.

A method for preparing an electrothermal composite material based on a nickel-chromium alloy wire weft-knitted structure, comprising the steps of:

1) Paste the adhesive film layer on the upper and lower surfaces of the electric heating fabric layer with a viscous primer;

2) Lay 4 layers of plain glass fiber/epoxy prepreg on the surface of the two layers of adhesive film to form a multi-layer structure;

3) Seal the assembled multi-layer structure with sealing tape and isolation film, and vacuum the inside of the multi-layer structure through the air felt and the vacuum bag connecting conduit;

4) Putting the vacuum multilayer structure into an autoclave for heating and curing by using a sealed vacuum bag to obtain an electrothermal composite material.

technical effect

An electrothermal composite material, comprising an electric heating fabric layer, the electric heating fabric layer includes nickel-chromium alloy wire, polyester, and aramid fiber, and an adhesive film is pasted on the upper and lower surfaces of the electric heating fabric layer, and then covered with glass with different laying angles. fiber/epoxy prepreg to form a multi-layer structure, which is vacuumed and compacted, placed in an autoclave for heating and curing, and an electrothermal composite material based on a weft-knitted structure is obtained. In the present invention, this kind of electrothermal composite material can be applied to engineering fields that require electric heating, such as anti-icing of helicopter air inlets. This kind of composite material can not only meet the mechanical performance requirements of load-bearing structures, but also provide effective heating efficiency and balance temperature.

Description of drawings

Figure 1 is a schematic diagram of the structure of the electrothermal composite material.

Figure 2 is an exploded view of Figure 1.

Figure 3 is a flow chart of the preparation method.

Detailed ways

The present invention will be further described below in conjunction with embodiment. The following descriptions are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Firstly, a computerized flat knitting machine is used to weave electrically heated fabrics. The parameters of the upper machine are 70 stitches, and the roller speed is 15. In order to improve the weaving efficiency and ensure the smooth unloading of the nickel-chromium alloy weft knitted fabric, the parameter value of the machine head speed is 10. When testing the thickness of nickel-chromium alloy weft-woven fabrics, the area of the presser foot is selected to be 100mm ² , the test time is set to 10s, the applied pressure is 20cN, and each sample is tested 5 times. In the end, we weaved a plain structure fabric with a surface density of 93.6g/ ^{cm 2} and a thickness of 0.342mm; a rib structure fabric with a surface density of 74.1g/cm ² and a thickness of 0.352mm; Rib structure fabric with a thickness of 0.550mm and a loop pitch of 1mm.

For the woven three kinds of electric heating fabrics, heating area: 0.06mm fineness nickel-chromium alloy wire and 50D aramid fiber parallel strands; insulation area: double-strand 75D polyester low elastic yarn; feeding ratio: 4/2 feeding ratio arrangement intertwined.

Figure 1 is a schematic structural diagram of the present invention, and the prepreg and adhesive film are laid up according to the exploded view of Figure 1 and Figure 2 . Lay the plain weave structure glass fiber/epoxy prepreg with an area of 300×300mm and a thickness of 0.25mm on the surface of the steel plate mold one by one according to the lay-up angle according to the lay-up angle of 0°, 45°, 0°, and 45°, and then lay the same The area thickness is 0.2mm adhesive film, the lower surface of the electric heating fabric is close to the adhesive film, and then the adhesive film and glass fiber/epoxy prepreg are laid symmetrically one by one.

After the paving is completed, a multi-layer structure is formed, and the multi-layer structure is sealed with a sealing strip and an isolation film, and the conduit is connected through an air felt and a vacuum bag, and the multi-layer structure is vacuumed at room temperature for 15 to 30 minutes for pre-compaction, and the pressure It is 0.07～0.1MPa. Subsequently, vacuum compaction was carried out again for 10-20 minutes.

Use a sealed vacuum bag to put the vacuum multi-layer structure into an autoclave for heating and curing. The specific conditions are: the autoclave is vacuumed at room temperature to maintain a vacuum degree of less than -0.097MPa, and the temperature is raised to 180°C at a rate of 30°C/hour during heating. , keep warm for 4 hours, then stop the temperature and pressure, lower the temperature with the furnace, drop the temperature below 60°C, and release the tank to obtain an electrothermal composite material with a weft-knitted structure of nickel-chromium alloy wire.

In the present invention, the electric heating fabric layer of the electric heating composite material includes electric heating elements and insulating fibers. The heating element is nickel-chromium alloy wire, and the insulating fiber is polyester or aramid fiber.

In the present invention, nickel-chromium alloy wire, polyester, and aramid fiber are co-woven to weave electric heating fabrics with plain stitch, 1+1 rib, and double rib weave structures.

In the present invention, the heat generation of the electrically heated fabric is to apply an electric current to the top of the reserved nickel-chromium alloy wire, and the electric current generates Joule heat, and the surface temperature of the fabric changes, so that the electrically heated fabric layer of the electrothermal composite material can generate heat evenly.

Example 1

The electrothermal composite material based on the weft-knitted structure of nickel-chromium alloy wire has a five-layer structure, which is composed of the first composite structure layer 1, the adhesive film layer 2, the electric heating fabric layer 3, the adhesive film layer 2, and the second composite structural layer 4. ; A symmetrical structure centered on the electric heating fabric layer 3 in the thickness direction.

Further, the electric heating fabric layer 3 includes electric heating elements and insulating fibers, the electric heating elements are nickel-chromium alloy wires, and the size of the nickel-chromium alloy wires is 0.04 mm to 0.2 mm. High strength, not easy to deform, good thermoplasticity at room temperature, non-magnetic, good corrosion resistance, long service life. The insulating fiber is polyester or aramid fiber, and the polyester or aramid fiber is 75D low elastic yarn. The polyester or aramid material has good elasticity, is not easy to wrinkle, has good heat resistance, light resistance and chemical resistance. Nickel-chromium alloy wire and insulating fiber are formed through composite braiding, which has good flexibility and adapts to irregular hyperbolic structures.

Further, the first composite structure layer 1 is composed of 4 layers of plain glass fiber/epoxy prepregs laid at angles of 0°, 45°, 0°, and 45° respectively. Prepreg, this kind of prepreg can be molded and hot-pressed. After molding, the structure is stable, uniform and repeatable. Every part produced from the mold is the same. After molding, it has good waterproof and corrosion resistance. Preferably, after co-curing with the electric heating fabric layer 3, the combination is tight and it is not easy to delaminate.

Further, the second composite structure layer 4 is formed by laying 4 layers of plain glass fiber/epoxy prepreg according to the laying angles of 45°, 0°, 45°, and 0° respectively. This laying method can increase the number of parts structural strength.

Further, the adhesive film layer 2 is a medium-high temperature epoxy structural adhesive film, which is consistent with the resin system used in the first composite structural layer 1 and the second composite structural layer 4, and has the same curing temperature. The adhesive film layer 2 The main function is to increase the adhesion between the electrothermal fabric layer 3 and the first composite structure layer 1 and the second composite structure layer 4, and increase the strength after curing.

Further, the heating function of the electrically heated fabric layer 3 is to apply a current to the top of the reserved nickel-chromium alloy wire, and the metal wire generates Joule heat when the current flows, and the surface temperature of the fabric changes. The nickel-chromium alloy wire is a good conductor of heat, so and evenly arranged, and finally the electric heating fabric layer of the electrothermal composite material can generate heat evenly.

Further, the fabric structure of the electric heating fabric layer 3 is plain stitch, rib weave, double rib weave.

Further, the nickel-chromium alloy wire and polyester or aramid fiber are fed into the computerized flat knitting machine in parallel for weaving together, and the nickel-chromium alloy wire is placed inside the fabric, which is conducive to heat transfer and does not separate from the fabric due to high-frequency vibration .

A method for preparing an electrothermal composite material based on a nickel-chromium alloy wire weft-knitted structure, comprising the steps of:

1) Paste the adhesive film layer on the upper and lower surfaces of the electric heating fabric layer with a viscous primer;

2) Lay 4 layers of plain glass fiber/epoxy prepreg on the surface of the two layers of adhesive film to form a multi-layer structure;

3) Seal the assembled multi-layer structure with sealing tape and isolation film, and vacuum the inside of the multi-layer structure through the air felt and the vacuum bag connecting conduit;

4) Putting the vacuum multilayer structure into an autoclave for heating and curing by using a sealed vacuum bag to obtain an electrothermal composite material.

Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted in an idealized or overly formal sense unless defined as herein explain. The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. An electrothermal composite material based on a nickel-chromium alloy wire weft-knitted structure is characterized in that it is a five-layer structure, which consists of the first conforming structure layer (1), adhesive film layer (2), and electric heating fabric layer (3) successively. ), an adhesive film layer (2), and a second composite structure layer (4); a symmetrical structure centered on the electric heating fabric layer (3) in the thickness direction. 2. A kind of electrothermal composite material based on nickel-chromium alloy wire weft-knitted structure according to claim 1, characterized in that, the electric heating fabric layer (3) includes electric heating elements and insulating fibers, and the electric heating elements are nickel-chromium alloy Wire, nickel-chromium alloy wire size is 0.04mm ~ 0.2mm. 3. A kind of electrothermal composite material based on nickel-chromium alloy wire weft-knitted structure according to claim 1, characterized in that, the first conforming structure layer (1) is made of 4 layers of plain glass fiber/epoxy prepreg It is laid according to the layup angles of 0°, 45°, 0°, and 45° respectively. The composite structure layer is made of medium-high temperature prepreg, which is molded or hot-pressed. 4. A kind of electrothermal composite material based on nickel-chromium alloy wire weft-knitted structure according to claim 1, characterized in that, the second composite structure layer (4) is made of 4 layers of plain glass fiber/epoxy prepreg Lay according to the laying angles of 45°, 0°, 45° and 0° respectively. 5. A kind of electrothermal composite material based on nickel-chromium alloy wire weft-knitted structure according to claim 1, characterized in that, the adhesive film layer (2) is a medium-high temperature epoxy structural adhesive film, which conforms to the first The resin systems used in the structural layer (1) and the second composite structural layer (4) are the same, and the curing temperature is the same. 6. A kind of electrothermal composite material based on nickel-chromium alloy wire weft-knitted structure according to claim 1, characterized in that, the heating of the electrically heated fabric layer (3) applies an electric current to the reserved nickel-chromium alloy wire top, When the metal wire passes current, Joule heat is generated, and the surface temperature of the fabric changes. 7. The electrothermal composite material based on the weft-knitted structure of nickel-chromium alloy wires according to claim 1, characterized in that the fabric structure of the electric heating fabric layer (3) is plain stitch, rib weave, double rib weave. 8. An electrothermal composite material based on a nickel-chromium alloy wire weft-knitted structure according to claim 1, wherein the nickel-chromium alloy wire and polyester or aramid fiber are fed into a computerized flat knitting machine in parallel for joint weaving , Nichrome wire placed inside the fabric. 9. A method for preparing an electrothermal composite material based on a nickel-chromium alloy wire weft-knitted structure, characterized in that it comprises the following steps: 1) Paste the adhesive film layer on the upper and lower surfaces of the electric heating fabric layer with a viscous primer; 2) Lay 4 layers of plain glass fiber/epoxy prepreg on the surface of the two layers of adhesive film to form a multi-layer structure; 3) Seal the assembled multi-layer structure with sealing tape and isolation film, and vacuum the inside of the multi-layer structure through the air felt and the vacuum bag connecting conduit; 4) Putting the vacuum multilayer structure into an autoclave for heating and curing by using a sealed vacuum bag to obtain an electrothermal composite material.

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