A shape memory composite assembly without an external heating component

Abstract

The application discloses a shape memory composite component without external heating components, which comprises a plurality of resin-based carbon fiber layers, the projection shape of the composite material in the thickness direction is rectangular, two electrode sheets are arranged in the resin-based carbon fiber layers, and the two electrode sheets are arranged between two resin-based carbon fiber layers, the layer angles of the two resin-based carbon fiber layers on the two sides of the electrode sheets are both 0° direction, and the two electrode sheets are away from and respectively arranged at the two ends of the 0° direction; the electrode sheets are provided with openings, and the electrode sheets are connected with wires. The shape memory composite material structure is provided with electrodes, the carbon fiber electric heating performance is used to complete temperature rise to realize shape recovery of the shape memory composite material. The problems of invasion of the heating components into the deformation space of the shape memory structure, reduction of the deformation capacity of the structure, increase of the folding stress of the shape memory composite material and material damage caused by the folding stress are effectively solved.

Description

Technical Field

[0001] This invention relates to the fields of shape memory composite materials and carbon fiber electric heating technology, and particularly to a shape memory composite material component that does not require an external heating component. Background Technology

[0002] Resin-based shape memory composites are a class of smart materials that combine the shape memory function of shape memory resins with the excellent mechanical properties of fiber reinforcements. Shape memory composite structures prepared from these materials can recover their original shape from a deformed intermediate state under external stimuli (physical factors such as temperature, light, humidity, and magnetic fields), exhibiting a shape memory effect. As a smart material capable of active deformation, shape memory composites offer numerous advantages over shape memory alloys and shape memory ceramics, including ease of molding, low density, large deformation capacity, and the ability to be fabricated over large areas. They are highly suitable for use as materials for deployable structures and have promising applications in the aerospace field.

[0003] Currently, the fabrication and application of thermotropic shape memory composites are quite widespread, achieving their shape memory effect through temperature changes. A typical thermotropic shape memory cycle usually includes steps such as heating, loading and deformation, holding the load while cooling, unloading to complete the shaping, and heating to restore the shape. Figure 6 As shown.

[0004] In the process of thermo-induced shape memory cycling, the heating of deformable structures usually requires the attachment of heating components to their outer surfaces. However, the attached heating components are at risk of detaching during repeated heating, cooling, and deformation of the shape memory structure, preventing the structure from reaching its shape recovery temperature. Furthermore, the increased thickness and stiffness of the heating components significantly increase the stress caused by the large strain when the shape memory composite material closes, which encroaches on the deformation space of the shape memory structure, reduces its deformation capacity, and severely limits the feasibility of using multiple shape memory composite materials together. Summary of the Invention

[0005] In view of the defects or deficiencies of the prior art, the present invention provides a shape memory composite material component that does not require an external heating component.

[0006] To this end, the shape memory composite material component without external heating provided by the present invention includes multiple layers of resin-based carbon fiber layup. The projected shape of the composite material in its thickness direction is rectangular to ensure that the electrode plates uniformly transmit current to the cross-section of the composite material, i.e., the deformation region. Two electrode plates are provided in the multiple layers of resin-based carbon fiber layup, and the two electrode plates are located between two layers of resin-based carbon fiber layup. At the same time, the electrode plates are located in the non-deformation region of the composite material. The layup angle of the two layers of resin-based carbon fiber layup on both sides of the electrode plates and adjacent to the electrode plates is 0°, which is located on the straight line of the length of the rectangle. Meanwhile, the two electrode plates are far apart and located at the two ends of the 0° direction. The electrode plates are provided with openings, and the two electrode plates are made of the same material and have the same structure. Each electrode plate is connected to a wire, which passes through the carbon fiber layup.

[0007] The shape memory composite material structure of the present invention has built-in electrodes, which can uniformly transfer current to carbon fibers and use the electrothermal properties of carbon fibers to complete the heating to achieve the shape recovery of the shape memory composite material.

[0008] An alternative approach is to include 2n layers of resin-based carbon fiber layup, where n is a natural number greater than or equal to 1; the two electrode sheets are located between the upper n layers of resin-based carbon fiber layup and the lower n layers of resin-based carbon fiber layup.

[0009] An alternative approach is that the electrode sheet has at least one opening, and the total area of ​​the opening is 25% to 35% of the area of ​​the electrode sheet.

[0010] An alternative approach is to create a rectangular hole on the electrode sheet, with the length and width of the rectangular hole aligned with the length and width of the rectangle projected onto the thickness direction of the composite material.

[0011] An alternative approach is to maintain a distance between the edges of each electrode sheet and the edge of the composite material. By optimizing this distance, the deformation area between the two electrode sheets can be ensured to complete the heating and deformation process. A further alternative is that, in the 0° direction of the layup direction, the distance between the outer edge of the electrode sheet and the edge of the composite material is 2%-18% of the width of the projected rectangle of the composite material along its thickness direction; and in the 90° direction of the layup direction, the distance is 2%-18% of the width of the projected rectangle of the composite material along its thickness direction.

[0012] The present invention also provides a method for preparing the above-mentioned shape memory composite material component, the method comprising:

[0013] Step 1: Lay up the layers below the electrode sheets, and then place the two electrode sheets at both ends of the top layer;

[0014] Step 2: Lay up the layer above the electrode sheet, make wire holes in the layer at the corresponding positions of the electrode sheet, and then fill the wire holes with silicone pads to obtain the intermediate body;

[0015] Step 3: Pre-compress the intermediate body, then lay absorbent material at the two wire holes, and then lay a non-porous release film in the area between the absorbent materials at both ends.

[0016] Step 4: Lay a layer of porous release film on the adhesive-absorbing material and the non-porous release film, then pre-press, and then heat-press to cure;

[0017] Step 5: After curing, remove the porous release liner, non-porous release liner, adhesive absorbent material, and silicone pad to expose the wire holes. Then, install wires at the two wire holes respectively, and solder the two wires to the two electrode plates respectively.

[0018] An optional approach is to use room temperature for pre-compression, a vacuum degree of 1 Pa to 10 Pa, and a pre-compression time of 10 min to 20 min.

[0019] Alternatively, the adhesive-absorbing material may include a release cloth and an adhesive-absorbing cloth, with the adhesive-absorbing cloth positioned above the release cloth.

[0020] An alternative is to use an autoclave for hot pressing and curing.

[0021] The shape memory composite structure of the present invention has built-in electrodes, which can use its own carbon fibers as electric heating elements. In the application of shape memory structure, there is no need to add an additional electric heating component, which simplifies the system structure. The carbon fibers used as heating components are an integral part of the shape memory composite structure itself, and there is no risk of them falling off due to repeated temperature rises and falls and deformations of the structure.

[0022] Furthermore, the composite material component of the present invention does not have the effect of the increased thickness caused by the heating component and the influence of the stiffness of the heating component itself on the shrinking, thus avoiding the significant increase in stress when the shape memory smart composite material shrinks. At the same time, it avoids the encroachment of the heating component on the deformation space when the shape memory structure shrinks and the impact on the deformation capacity, making it possible to use multiple shape memory composite materials together. Attached Figure Description

[0023] Figure 1 The shape and dimensions (in mm) of the resin-based carbon fiber shape memory composite material component disclosed in Example 1.

[0024] Figure 2 The electrode sheet structure in the scheme disclosed in Example 1.

[0025] Figure 3 Example 4 discloses the projection structure and dimensions of a component with a circular arc cross-section in its own thickness direction.

[0026] Figure 4 The electrode sheet structure in the disclosed scheme of Example 4.

[0027] Figure 5 This is a schematic diagram of the appearance of the component prepared in Example 4.

[0028] Figure 6 This is a schematic diagram of the thermally induced shape memory cycle process of shape memory materials. Detailed Implementation

[0029] Unless otherwise specified, the scientific and technical terms used in this article are intended for understanding by those skilled in the art.

[0030] In the resin-based carbon fiber shape memory composite material of the present invention, two electrode sheets are placed at both ends of the material length direction (0° direction of the layup direction); the composite material is prepared using a continuous carbon fiber reinforced unidirectional tape prepreg; the direction determined by the two electrodes is defined as the 0° direction, the two unidirectional tapes (or layups) located above and below the two electrode sheets are in the 0° direction, and these two unidirectional tapes are in the middle position among all layups.

[0031] In the specific solution, highly conductive materials are used as electrode sheets and placed at both ends of the resin-based carbon fiber shape memory smart composite sheet. Two layers of 0° direction continuous carbon fiber reinforced unidirectional tape prepreg are used to cover and connect the electrode sheets at both ends. The 0° direction continuous carbon fiber realizes both the material reinforcement function and the conductive heating function.

[0032] The electrode sheet is made of a highly conductive material; the electrode sheet has openings to ensure sufficient interlayer peel strength in certain areas. Preferably, the total area of ​​all openings is 25% to 35% of the electrode sheet area; more preferably, the openings are rectangular, and the length and width of the rectangular openings are consistent with the length and width directions of the rectangle projected onto the thickness direction of the composite structure (e.g., ...). Figure 1 In the component structure shown, the length of the composite material and the length of the rectangular holes on the electrode sheet are both set in the horizontal direction shown in the figure, and the width of the composite material and the width of the rectangular holes on the electrode sheet are both set in the vertical direction shown in the figure, in order to facilitate current conduction. The rectangular holes are centrally distributed on the electrode sheet, and multiple rectangular holes are evenly spaced.

[0033] The specific pre-compression and curing conditions in the preparation process depend on the resin-based carbon fiber material itself, and the diameter of the wire hole depends on the wire thickness and welding process requirements. In the preparation process, silicone pads are used to pre-fill the holes to prevent the wire holes from being filled with resin after curing, so that the holes do not need to be opened again. The adhesive absorption treatment is to take into account that the contact resistance between the electrode sheet and the composite material is too large, and the deformation area of ​​the composite material cannot rise to the forming temperature.

[0034] The present invention will be further explained and illustrated below through embodiments. The present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0035] It should be noted that, unless otherwise specified, all components and devices in this invention are based on components and devices known in the prior art.

[0036] Example 1:

[0037] This embodiment discloses a carbon fiber shape memory composite material component that does not require an external heating component. In this embodiment, a unidirectional tape prepreg of shape memory epoxy resin and T700 continuous carbon fiber is used for layup (in this embodiment, the mass content of epoxy resin is 43% and the mass content of T700 carbon fiber is 57%; the materials of each layup are the same).

[0038] like Figure 1 As shown, the composite material component (or each layup 1) in this embodiment is a rectangular plate with a length of 202 mm and a width of 23 mm, and the specific layup is [-45° / 45° / 90° / 0°]s; both electrode sheets 2 are made of copper sheets with a thickness of 0.1 mm; as Figure 2 As shown, the outer contour of each electrode sheet is a rectangle with a length of 18 mm and a width of 15 mm. Each electrode sheet has four rectangular holes, each hole being a rectangle with a length of 9 mm and a width of 2 mm (in this embodiment, the total area of ​​the holes on each electrode sheet is 26.7% of the area of ​​the electrode sheet). The distance between adjacent holes in the width direction of the composite material is 2 mm, and the holes are evenly distributed in the center on the electrode sheet.

[0039] The preparation method of the composite material in this embodiment:

[0040] 1) After completing the first four layups (layups below the electrode sheets), place the two electrode sheets at both ends of the 0° layup, with a distance of 2.5 mm from the edge in the layup width direction (10.9% of the composite layup width) and a distance of 4 mm from the edge in the layup length direction (17.4% of the composite layup width). The specific positions are as follows: Figure 1 As shown;

[0041] 2) Lay up the top layer (the last 4 layers) of the electrode sheet. Make holes in the last 4 layers at the corresponding positions of the electrode sheet to form wire holes. The holes are rectangles with a length of 5mm and a width of 3mm. The length and width of the wire holes are in the same direction as the length and width of the electrode sheet. The wire holes are centered along the width of the layup and 5mm away from the edge of the layup length. After the layup is completed, fill the gap with a silicone pad to form the intermediate body.

[0042] 3) Pre-compress the intermediate (at room temperature, vacuum degree of 5Pa, pre-compression time of 10min), and then perform local adhesive absorption treatment at the wire hole. The specific method is to lay a layer of release cloth and a layer of adhesive absorption cloth at each wire hole separately. The adhesive absorption material is laid in an area with a depth of 32mm in the layup length direction.

[0043] 4) After the adhesive absorbent material is laid, lay a layer of non-porous release film in the area between the two ends of the adhesive absorbent material on the layer, and then lay a layer of porous release film on the whole.

[0044] 5) Next, pre-press at room temperature for 10 minutes (vacuum degree of 5 Pa), and then cure in a hot autoclave (hold at 100℃ for 2 hours, hold at 150℃ for 4 hours, apply pressure of 0.6 MPa); after curing, remove the silicone pad, adhesive absorbent, non-porous separator and porous separator, and then weld wires to the electrode plates at both ends.

[0045] When the carbon fiber shape memory composite material prepared by the method disclosed in this embodiment is used, the two electrode plates are connected to the positive and negative terminals of a power supply respectively via wires. Testing showed that under an input voltage of 4.50V, the material can heat from room temperature to 130℃ within 5 minutes (the temperature measurement point is located on the surface of the composite structure, at the midpoint of its length and width). Furthermore, the carbon fiber shape memory composite material prepared by the method disclosed in this embodiment can meet its requirements for shape memory through electrothermal heating. Figure 6 As shown (i.e., heating from room temperature to 130°C within 5 minutes, followed by deformation using a mandrel (specifically, the mandrel is positioned against the middle region of the material, and the material on both sides of the mandrel is bent 180°; the outer diameter of the mandrel is 30mm, as shown) Figure 6 As shown), the loading is kept cooled to room temperature (natural cooling), unloading is completed to complete the shaping, and the temperature is raised from room temperature to 130°C within 5 minutes to complete the shape recovery. The heating requirements in the thermal shape memory cycle are completed to complete the shaping at high temperature and the shape recovery after heating.

[0046] Example 2:

[0047] This embodiment differs from Embodiment 1 in that each opening on the electrode sheet is a rectangle with a length of 11.8 mm and a width of 2 mm (the total area of ​​the openings on the electrode sheets in this embodiment is 35% of the electrode sheet area). Testing showed that under an input voltage of 4.50 V, the material in this embodiment can be heated from room temperature to 130°C within 5 minutes (the temperature measurement point is located on the surface of the composite structure, at the midpoint of its length and width). Furthermore, the carbon fiber shape memory composite material prepared by the method disclosed in this embodiment can meet its requirements for shape memory through electrothermal heating. Figure 6 The heating requirement in the thermally induced shape memory cycle is shown, which completes the shaping at high temperature and the shape recovery after heating.

[0048] Example 3:

[0049] This embodiment differs from Embodiment 1 in that the distance between the electrode sheet and the edge along the length direction of the layup is 2 mm (8.7% of the composite layup width), and the distance between the electrode sheet and the edge along the width direction of the layup is 1.5 mm (6.5% of the composite layup width). Testing showed that at an input voltage of 4.50V, the middle region of the outer surface of the material in this embodiment can be heated from room temperature to 130°C within 5 minutes. Furthermore, the carbon fiber shape memory composite material prepared by the method disclosed in this embodiment can meet its requirements for shape memory through electrothermal heating. Figure 6 The heating requirement in the thermally induced shape memory cycle is shown, which completes the shaping at high temperature and the shape recovery after heating.

[0050] Comparative example:

[0051] The difference between this comparative example and Example 1 is that the distance between the electrode sheet and the edge along the layup length direction is 0.25 mm (1.1% of the composite material width), and the distance between the electrode sheet and the edge along the layup width direction is also 0.25 mm (1.1% of the composite material width). Testing showed that at an input voltage of 4.50V, the material in this example could only reach 130°C in the electrode region due to the gradually increasing contact resistance between the electrode sheet and the carbon fibers in the composite material during heating. The intermediate deformation region of the material could not reach a higher temperature, thus failing to complete the shaping process and subsequent shape recovery during the thermo-induced shape memory cycle through electrothermal heating.

[0052] Example 4:

[0053] This embodiment discloses another carbon fiber shape memory composite material component that does not require an external heating component. The layup material in this embodiment is the same as in Embodiment 1. Figure 3 As shown, the cross-section of the composite material layup 1 in this embodiment is an arc with a radius of 30 mm (i.e., the radius of the circle containing the arc is 30 mm), and the layup length is 284 mm (the projected rectangle of the layup in its own thickness direction has a length of 284 mm and a width of 45 mm). The specific layup is [-45° / 45° / 90° / 0°]s. The electrode sheet 2 is made of copper sheet with a thickness of 0.03 mm. The specific geometric parameters of each electrode sheet are as follows: Figure 4 As shown, the outer contour of each copper sheet is a rectangle with a length of 42mm and a width of 15mm. Ten rectangular holes are made, each hole being a rectangle with a length of 9mm and a width of 2mm (the hole area accounts for 28.6% of the electrode sheet area). The spacing between adjacent holes is 2mm, and the holes are evenly distributed in the center on the copper sheet.

[0054] The preparation method disclosed in this embodiment is as follows:

[0055] 1) After completing the first four layers, place two copper plates at both ends of the 0° layup, 1.5mm from the edge of the layup width direction (3.3% of the width of the layup projection rectangle) and 3mm from the edge of the layup length direction (6.7% of the width of the layup projection rectangle). The specific positions of the copper electrodes are as follows: Figure 3 As shown;

[0056] 2) Lay the lower layers, and make holes at the corresponding positions of the electrode sheet in the last 4 layers to form wire holes. The wire holes are rectangles with a length of 5mm and a width of 3mm. The length and width of the wire holes are in the same direction as the length and width of the electrode sheet. The wire holes are centered along the width of the layer and 4mm away from the edge of the length of the layer. After the layer is laid, fill the wire holes with silicone pads to obtain the intermediate body.

[0057] 3) Pre-compress the intermediate (at room temperature, vacuum degree of 5Pa, pre-compress time of 15min). After pre-compressing, perform local adhesive absorption treatment at the electrode. The method is to lay a layer of release cloth and a layer of adhesive absorption cloth separately at the electrode. The depth of the adhesive absorption material layer in the length direction is 30mm.

[0058] 4) After the adhesive-absorbing material is laid, lay a layer of non-porous release film in the area between the two ends of the adhesive-absorbing material on the layer; then lay a layer of porous release film on the entire layer.

[0059] 5) Perform pre-compression at room temperature for 15 minutes (vacuum degree of 5 Pa), followed by curing in an autoclave; after curing, weld wires to the electrodes at both ends, and the finished product is as follows. Figure 5 As shown.

[0060] The carbon fiber shape memory composite material structure prepared by the method disclosed in this embodiment can be heated from room temperature to 130°C within 5 minutes under an input voltage of 5.00V, thus meeting its requirements. Figure 6 The temperature rise requirement during the thermally induced shape memory cycle is shown.

[0061] The parts of this invention not described in detail are common knowledge to those skilled in the art.

Claims

1. A shape memory composite material component that does not require an external heating element, comprising multiple layers of resin-based carbon fiber layup, characterized in that, The composite material has a rectangular projection shape along its thickness direction to ensure that the electrode plates uniformly transmit current to the cross-section of the composite material, i.e., the deformation region. Two electrode plates are disposed within the multilayer resin-based carbon fiber layup, with the two electrode plates located between two layers of resin-based carbon fiber layup. Simultaneously, the electrode plates are located in the non-deformation region of the composite material. The layup angle of the two resin-based carbon fiber layup layers adjacent to the electrode plates is 0°, which lies along the length of the rectangle. The two electrode plates are far apart and located at opposite ends of the 0° direction. The electrode plates have openings, and the two electrode plates are made of the same material and have the same structure. Each electrode plate is connected to a wire, which passes through the carbon fiber layup. The electrode sheet has at least one opening, and the total area of ​​the openings is 25% to 35% of the electrode sheet area. A rectangular hole is made on the electrode sheet, and the length and width of the rectangular hole are consistent with the length and width of the rectangle projected in the thickness direction of the composite material. The edge of each electrode sheet is separated from the edge of the composite material. By optimizing the distance between the edge of the electrode sheet and the edge of the composite material, it is ensured that the deformation area between the two electrode sheets completes the heating and deformation.

2. The shape memory composite material component without external heating element according to claim 1, characterized in that, It includes 2n layers of resin-based carbon fiber layup, where n is a natural number greater than or equal to 1; the two electrode sheets are located between the upper n layers of resin-based carbon fiber layup and the lower n layers of resin-based carbon fiber layup.

3. The shape memory composite material component without external heating element according to claim 1, characterized in that, In the 0° direction of the layup direction, the distance between the outer edge of the electrode sheet and the edge of the composite material accounts for 2%-18% of the width of the projected rectangle of the composite material along its own thickness direction; in the 90° direction of the layup direction, the distance between the outer edge of the electrode sheet and the edge of the composite material accounts for 2%-18% of the width of the projected rectangle of the composite material along its own thickness direction.

4. The method for preparing the shape memory composite material component according to claim 1, characterized in that, The methods include: Step 1: Lay up the layers below the electrode sheets, and then place the two electrode sheets at both ends of the top layer; Step 2: Lay up the layer above the electrode sheet, make wire holes in the layer at the corresponding positions of the electrode sheet, and then fill the wire holes with silicone pads to obtain the intermediate body; Step 3: Pre-compress the intermediate body, then lay absorbent material at the two wire holes, and then lay a non-porous release film in the area between the absorbent materials at both ends. Step 4: Lay a layer of porous release film on the adhesive-absorbing material and the non-porous release film, then pre-press, and then heat-press to cure; Step 5: After curing, remove the porous release liner, non-porous release liner, adhesive absorbent material, and silicone pad to expose the wire holes. Then, install wires at the two wire holes respectively, and solder the two wires to the two electrode plates respectively.

5. The method for preparing the shape memory composite material component according to claim 4, characterized in that, The pre-compression temperature is room temperature, the vacuum degree is 1Pa-10Pa, and the pre-compression time is 10min-20min.

6. The method for preparing the shape memory composite material component according to claim 4, characterized in that, The adhesive-absorbing material includes a release cloth and an adhesive-absorbing cloth, with the adhesive-absorbing cloth positioned above the release cloth.

7. The method for preparing the shape memory composite material component according to claim 4, characterized in that, Thermo-curing is performed using an autoclave.

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