Shape memory composite material and method for producing the same

Abstract

The application provides a shape memory composite material and a preparation method thereof, and belongs to the technical field of composite materials.The shape memory composite material comprises an upper composite layer, an intermediate layer and a lower composite layer which are sequentially stacked, the upper composite layer and the intermediate layer and the intermediate layer and the lower composite layer are connected through polyurethane film layers respectively, the upper composite layer comprises an upper carbon fiber fabric layer and a plurality of polyurethane film layers which are stacked on the carbon fiber fabric layer, the intermediate layer comprises a plurality of glass fiber fabric layers which are stacked and connected through polyurethane film layers, and the lower composite layer comprises a plurality of polyurethane film layers which are stacked and a lower carbon fiber fabric layer which is stacked on the polyurethane film layers.The shape memory composite material prepared by the application has good mechanical strength, good deformation capacity and shape memory function.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, specifically to a shape memory composite material and its preparation method. Background Technology

[0002] Shape memory materials, a novel type of smart material that emerged in the last century, can respond to deformations caused by mechanical forces under certain stimuli, such as heating or electrical stimulation, thus recovering the deformation caused by mechanical forces. Therefore, they have broad application prospects in the aerospace field. They can be mainly divided into three categories: shape memory alloys (SMAs), shape memory ceramics (SMCs), and shape memory polymer composites (SMPCs). Although shape memory alloys and shape memory ceramics can achieve stable deployment, overcoming the problem of poor stability in traditional space deployable structures, they still suffer from high mass and low stored strain. In contrast, shape memory polymer composites can achieve higher stored strain and strain recovery capabilities, as well as deployment stability, while also possessing advantages such as low density and light weight. Therefore, shape memory polymer composites are considered ideal materials for novel space deployable structures.

[0003] Shape memory polymer composites are mainly composed of a shape memory polymer matrix and reinforcing or functional phases. The most commonly used reinforcing or functional phases fall into three categories: particles, chopped fibers, and continuous fibers. Particle-filled shape memory composites are typically used as functional materials to achieve shape memory effects through different driving mechanisms, such as electro-driven mechanisms. Chopped fiber-reinforced shape memory composites offer improved mechanical properties compared to particle-filled composites, but compared to continuous fibers as reinforcing phases, they not only present dispersion issues during preparation but also fail to meet the mechanical performance requirements for large-scale structural materials. Therefore, when used as structural materials, continuous fibers are primarily employed as reinforcing phases. Carbon fiber, as a type of continuous fiber, possesses advantages such as high specific strength, high specific modulus, and high thermal conductivity. Thus, carbon fiber shape memory composites prepared using carbon fiber as reinforcement are the most widely used type of shape memory polymer composite.

[0004] Existing carbon fiber reinforced shape memory composites are mostly made by using polymers with shape memory function and continuous carbon fibers to prepare prepregs and then molding and curing them or by using RTM process. Moreover, carbon fiber reinforced shape memory composites have large overall stiffness and small failure strain above the material's shape memory transition temperature, resulting in poor material deformation capacity, low folding efficiency, and significant limitations in application, and cannot meet the needs of large deformation. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned technical problems by proposing a shape memory composite material and its preparation method. The shape memory composite material prepared by this invention not only has good mechanical strength, but also good deformation capacity and shape memory function.

[0006] The technical solution of this invention is implemented as follows:

[0007] A shape memory composite material includes an upper composite layer, an intermediate layer, and a lower composite layer stacked sequentially, wherein the upper composite layer and the intermediate layer, and the intermediate layer and the lower composite layer are respectively connected by polyurethane film layers.

[0008] Preferably, the upper composite layer includes an upper carbon fiber fabric layer and several polyurethane film layers stacked on the carbon fiber fabric layers, the middle layer includes several stacked glass fiber fabric layers connected by polyurethane film layers, and the lower composite layer includes several stacked polyurethane film layers and a lower carbon fiber fabric layer stacked on the polyurethane film layers.

[0009] In existing technologies, combining carbon fiber fabric with shape memory polymers can significantly enhance the mechanical strength of shape memory polymers. However, the resulting shape memory composite material has high overall stiffness and low failure strain above the shape memory transition temperature, leading to poor deformation capacity, low folding efficiency, and significant limitations in its application, failing to meet the requirements for large deformations. To address this issue, the present invention provides a multi-layered composite structure for the shape memory composite material. Furthermore, by adding a glass fiber fabric layer to the structure and combining it with a polyurethane shape memory polymer, and by employing a combination of 45° and 0° plain weave glass fiber fabrics, the elastic modulus of the material can be effectively reduced, thus lowering its stiffness, improving its deformation capacity, and expanding the application range of the shape memory composite material.

[0010] Preferably, the upper carbon fiber fabric layer in the upper composite layer is a 3K plain weave carbon fiber fabric, and the number of polyurethane film layers stacked on the upper carbon fiber fabric layer is 3.

[0011] Preferably, the intermediate layer has four layers of glass fiber fabric, and the glass fiber fabric layers at the top and bottom of the intermediate layer are 0° plain weave glass fiber fabric, while the glass fiber fabric in the two middle layers is 45° plain weave glass fiber fabric.

[0012] Preferably, the lower composite layer has 3 polyurethane film layers and the lower carbon fiber fabric layer is a 3K plain weave carbon fiber fabric.

[0013] A method for preparing shape memory composite materials includes the following steps:

[0014] A polytetrafluoroethylene (PTFE) release cloth is laid on a clean metal base plate. Then, from bottom to top, the lower composite layer, polyurethane film layer, intermediate layer, polyurethane film layer, and upper composite layer are laid in sequence. The metal base plate is then placed on a molding machine platform for hot pressing. The hot pressing parameters are: pressure 2-10 MPa, temperature 80-160℃, and time 30-60 min. After cooling to below 45℃, the shape memory composite material is obtained.

[0015] The present invention employs a thin-film lamination method in its molding process, which involves alternately stacking shape memory thermoplastic films and continuous fiber fabrics, and then preparing shape memory composite materials through hot pressing. By controlling the molding pressure and temperature, the melt is ensured to penetrate between the fiber layers without flowing between the fiber fabric layers. Compared with resin vacuum injection molding and resin transfer molding, the shape memory composite materials prepared by this method have advantages such as simple process, high production efficiency, controllable resin content, and low porosity of the composite material.

[0016] Preferably, the method for preparing the polyurethane film layer includes the following steps:

[0017] 1) Add nano-silica to the hydrolysate of epoxy silane coupling agent and stir to react to obtain coupling agent modified nano-silica. Add the coupling agent modified nano-silica to tetraethylenepentamine solution and heat to react to obtain aminated nano-silica.

[0018] 2) Mix polypropylene glycol, dichlorodiphenylmethane diamine and aminated nano-silica evenly, then add tetrahydrofuran, heat to 50-55℃, then add isocyanate and stir to react;

[0019] 3) Pour the above reaction solution into a mold, and then perform vulcanization and curing in sequence to obtain a polyurethane film layer.

[0020] Preferably, the glass fiber fabric layer in the intermediate layer undergoes a modification treatment, including the following steps:

[0021] 1) Polyvinyl acetate was added to anhydrous ethanol and heated and stirred to dissolve it, resulting in a polyvinyl acetate solution. Then, sodium hydroxide solution was added dropwise to partially alcoholyze the polyvinyl acetate, resulting in an alcoholyzed polyvinyl acetate solution.

[0022] 2) Add glutaraldehyde to the alcoholysis polyvinyl acetate solution and stir evenly. Then immerse the glass fiber fabric in the solution, add hydrochloric acid solution to adjust the pH of the solution to acidic, heat to 40°C and react for 8 minutes. After taking out the glass fiber fabric, dry it to obtain the glass fiber fabric intermediate.

[0023] 3) Place the glass fiber fabric intermediate in a sodium hydroxide solution, then heat to react, remove the glass fiber fabric intermediate and dry it to obtain the final product.

[0024] In the technical solution of this invention, as described above, by combining a glass fiber fabric layer with a polyurethane shape memory polymer, the stiffness of the shape memory polymer material is reduced and the material's deformability is improved. However, due to the poor bonding between the glass fiber fabric and the polyurethane shape memory polymer, the improvement effect of the glass fiber fabric on the deformability of the polyurethane shape memory polymer is limited. To solve this problem, this invention further modifies the glass fiber fabric. First, sodium hydroxide solution is added dropwise to a polyvinyl acetate solution, causing partial hydrolysis of the polyvinyl acetate and loading of hydroxyl groups. Then, the cross-linking effect of glutaraldehyde is used to cause the hydrolyzed polyvinyl acetate to undergo a cross-linking reaction on the glass fiber fabric. Finally, the hydrolysis of sodium hydroxide is used again to fully hydrolyze the polyvinyl acetate on the glass fiber fabric to generate hydroxyl groups, thereby loading a large number of hydroxyl groups onto the surface of the glass fiber fabric. On the other hand, in the polyurethane film preparation process, this invention incorporates aminated nano-silica into the polyurethane shape memory polymer. The hydrogen bonding force generated between the amino groups in the polymer and the hydroxyl groups on the surface of the glass fiber fabric is used to improve the bonding force between the glass fiber fabric layer and the polyurethane shape memory polymer, thereby reducing the stiffness of the shape memory polymer material and further improving the material's deformability.

[0025] Preferably, the amount of glutaraldehyde added in step 2) is 0.8-1.6 wt% of the alcoholysis polyvinyl acetate solution.

[0026] To improve the deformability of shape memory polymers, this invention requires the crosslinking of a sufficient amount of hydrolyzed polyvinyl acetate onto glass fiber fabric. This allows the glass fiber fabric to carry sufficient hydroxyl groups to form hydrogen bonds with the amino groups in the polymer, thereby enhancing the bonding ability between the two. Therefore, this invention controls the addition of glutaraldehyde to be greater than 0.8 wt% of the hydrolyzed polyvinyl acetate solution. Unexpectedly, during the experiment, it was found that when the addition of glutaraldehyde exceeded 1.6 wt%, the shape memory performance (shape recovery rate) of the material decreased significantly. This may be because excessive crosslinking of hydrolyzed polyvinyl acetate on the glass fiber fabric leads to a reduction in the hard segment content in the polyurethane structure, thus causing a decrease in the shape memory performance of the material. Therefore, this invention controls the addition of glutaraldehyde to be 0.8-1.6 wt% of the hydrolyzed polyvinyl acetate solution.

[0027] Preferably, the heating temperature in step 3) is 40-45℃ and the heating reaction time is 2-3h.

[0028] The present invention has the following beneficial effects:

[0029] 1) This invention sets up a multi-layer structure for the memory composite material, and adds a glass fiber fabric layer to the structure, combining the glass fiber fabric layer with the polyurethane shape memory polymer. At the same time, the glass fiber fabric adopts a combination of 45° glass fiber plain weave fabric and 0° glass fiber plain weave fabric, which can effectively reduce the elastic modulus of the material, that is, reduce the stiffness of the material, improve the deformation capacity of the material, and expand the application range of the memory composite material.

[0030] 2) The molding process of this invention adopts the film lamination method, that is, shape memory thermoplastic film and continuous fiber fabric are stacked alternately, and then the shape memory composite material is prepared by hot pressing. By controlling the molding pressure and temperature, it is ensured that the melt can enter between the fiber layers, but will not flow between the fiber fabric layers.

[0031] 3) During the preparation of polyurethane films, aminated nano-silica is doped into polyurethane shape memory polymers. The hydrogen bonding between the amino groups in the polymer and the hydroxyl groups on the surface of the modified glass fiber fabric is utilized to improve the bonding force between the glass fiber fabric layer and the polyurethane shape memory polymer, thereby reducing the stiffness of the shape memory polymer material and further improving the material's deformability. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the shape memory composite material of the present invention.

[0033] Figure Labels

[0034] The upper composite layer 100, the middle layer 200, the lower composite layer 300, the polyurethane film layer 400, the upper carbon fiber fabric layer 101, the glass fiber fabric layer 201, and the lower carbon fiber fabric layer 301. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In a specific embodiment of the present invention, the 3K plain weave carbon fiber fabric is a T300 grade continuous carbon fiber fabric with a surface density of 200 g / m², and the surface density of the glass fiber plain weave fabric is 400 g / m².

[0037] The shape memory composite material comprises an upper composite layer 100, an intermediate layer 200, and a lower composite layer 300 stacked sequentially. The upper composite layer is connected to the intermediate layer, and the intermediate layer is connected to the lower composite layer, respectively, by polyurethane film layers 400. The upper composite layer includes an upper carbon fiber fabric layer 101 and three polyurethane film layers 400 stacked on top of the carbon fiber fabric layer. The upper carbon fiber fabric layer is a 3K plain weave carbon fiber fabric. The intermediate layer comprises four layers of glass fiber fabric 201 stacked together, connected by polyurethane film layers 400. The top and bottom glass fiber fabric layers in the intermediate layer are 0° plain weave glass fiber fabric, while the glass fiber fabric in the two middle layers is 45° plain weave glass fiber fabric. The lower composite layer comprises three layers of polyurethane film layers 400 stacked together and a lower carbon fiber fabric layer 301 stacked on top of the polyurethane film layer. The lower carbon fiber fabric layer is a 3K plain weave carbon fiber fabric.

[0038] Example 1

[0039] A method for preparing shape memory composite materials includes the following steps:

[0040] A polytetrafluoroethylene (PTFE) release cloth is laid on a clean metal base plate. Then, from bottom to top, three layers of polyurethane film, a lower carbon fiber fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, an upper carbon fiber fabric layer, and the three layers of polyurethane film are laid in sequence. The metal base plate is then placed on a molding press platform for hot pressing. The hot pressing parameters are: pressure 8 MPa, temperature 130°C, time 50 min, and then cooled to 40°C to obtain the shape memory composite material.

[0041] The method for preparing a polyurethane thin film layer includes the following steps:

[0042] 1) Add silane coupling agent KH560 to deionized water at a mass ratio of 1:30, heat to 50℃, and stir to obtain epoxy silane coupling agent hydrolysate. Then add nano silica to epoxy silane coupling agent hydrolysate at a mass-volume ratio of 1g / 50mL, stir and react for 2h to obtain coupling agent modified nano silica.

[0043] The coupling agent-modified nano-silica was added to a 3% tetraethylenepentamine aqueous solution at a mass-volume ratio of 1 g / 60 mL, heated to 80 °C, and stirred for 3 h to obtain aminated nano-silica.

[0044] 2) Mix polypropylene glycol, dichlorodiphenylmethane diamine and aminated nano-silica evenly according to a mass ratio of 20:5:3, then add tetrahydrofuran, with a mass-volume ratio of 1 g / 500 mL of polypropylene glycol to tetrahydrofuran, heat to 53 °C, then add isocyanate, with a mass ratio of 1:2 of polypropylene glycol to isocyanate, and stir for 20 min.

[0045] 3) Pour the above reaction solution into a mold, vulcanize at 80°C for 3 hours, and then cure at room temperature for 10 days to obtain a polyurethane film layer.

[0046] The fiberglass plain weave fabric layer undergoes modification treatment, including the following steps:

[0047] 1) Add polyvinyl acetate to anhydrous ethanol, heat and stir to dissolve, prepare a polyvinyl acetate solution with a mass concentration of 5%, and then add an ethanol solution with a concentration of 30wt% sodium hydroxide dropwise for alcoholysis for 20min. The volume ratio of sodium hydroxide solution to polyvinyl acetate solution is 1:30.

[0048] 2) Add glutaraldehyde to the alcoholysis polyvinyl acetate solution, the amount of glutaraldehyde added is 1.4 wt% of the alcoholysis polyvinyl acetate solution, stir evenly, and then immerse the glass fiber fabric in the above solution at a bath ratio of 1:50. Add hydrochloric acid solution to adjust the pH value of the solution to 3, heat to 40℃ and react for 8 minutes. After taking out the glass fiber fabric, dry it at 70℃ to obtain the glass fiber fabric intermediate.

[0049] 3) Place the glass fiber fabric intermediate in a 20wt% sodium hydroxide aqueous solution at a bath ratio of 1:30, then heat to 45℃ and react for 2.5h. After removing the glass fiber fabric intermediate, dry it at 50℃ to obtain the final product.

[0050] Example 2

[0051] A method for preparing shape memory composite materials includes the following steps:

[0052] A polytetrafluoroethylene (PTFE) release cloth is laid on a clean metal base plate. Then, from bottom to top, three layers of polyurethane film, a lower carbon fiber fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, an upper carbon fiber fabric layer, and the three layers of polyurethane film are laid in sequence. The metal base plate is then placed on a molding machine platform for hot pressing. The hot pressing parameters are: pressure 3 MPa, temperature 90°C, time 40 min, and then cooled to 40°C to obtain a shape memory composite material.

[0053] The method for preparing a polyurethane thin film layer includes the following steps:

[0054] 1) Add silane coupling agent KH560 to deionized water at a mass ratio of 1:30, heat to 50℃, and stir to obtain epoxy silane coupling agent hydrolysate. Then add nano silica to epoxy silane coupling agent hydrolysate at a mass-volume ratio of 1g / 50mL, stir and react for 2h to obtain coupling agent modified nano silica.

[0055] The coupling agent-modified nano-silica was added to a 3% tetraethylenepentamine aqueous solution at a mass-volume ratio of 1 g / 60 mL, heated to 80 °C, and stirred for 3 h to obtain aminated nano-silica.

[0056] 2) Mix polypropylene glycol, dichlorodiphenylmethane diamine and aminated nano-silica evenly according to a mass ratio of 20:5:3, then add tetrahydrofuran, with a mass-volume ratio of 1 g / 500 mL of polypropylene glycol to tetrahydrofuran, heat to 53 °C, then add isocyanate, with a mass ratio of 1:2 of polypropylene glycol to isocyanate, and stir for 20 min.

[0057] 3) Pour the above reaction solution into a mold, vulcanize at 80°C for 3 hours, and then cure at room temperature for 10 days to obtain a polyurethane film layer.

[0058] The fiberglass plain weave fabric layer undergoes modification treatment, including the following steps:

[0059] 2) Add polyvinyl acetate to anhydrous ethanol, heat and stir to dissolve, prepare a polyvinyl acetate solution with a mass concentration of 5%, and then add an ethanol solution with a concentration of 30wt% sodium hydroxide dropwise for alcoholysis for 20min. The volume ratio of sodium hydroxide solution to polyvinyl acetate solution is 1:30.

[0060] 2) Add glutaraldehyde to the alcoholysis polyvinyl acetate solution, the amount of glutaraldehyde added is 1.0 wt% of the alcoholysis polyvinyl acetate solution, stir evenly, and then immerse the glass fiber fabric in the above solution at a bath ratio of 1:50. Add hydrochloric acid solution to adjust the pH value of the solution to 3, heat to 40℃ and react for 8 minutes. After taking out the glass fiber fabric, dry it at 70℃ to obtain the glass fiber fabric intermediate.

[0061] 3) Place the glass fiber fabric intermediate in a 20wt% sodium hydroxide aqueous solution at a bath ratio of 1:30, then heat to 45℃ and react for 2.5h. After removing the glass fiber fabric intermediate, dry it at 50℃ to obtain the final product.

[0062] Example 3

[0063] A method for preparing shape memory composite materials includes the following steps:

[0064] A polytetrafluoroethylene (PTFE) release cloth is laid on a clean metal base plate. Then, from bottom to top, three layers of polyurethane film, a lower carbon fiber fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, an upper carbon fiber fabric layer, and the three layers of polyurethane film are laid in sequence. The metal base plate is then placed on a molding press platform for hot pressing. The hot pressing parameters are: pressure 2 MPa, temperature 130°C, time 30 min, and then cooled to 40°C to obtain a shape memory composite material.

[0065] The method for preparing a polyurethane thin film layer includes the following steps:

[0066] 1) Add silane coupling agent KH560 to deionized water at a mass ratio of 1:30, heat to 50℃, and stir to obtain epoxy silane coupling agent hydrolysate. Then add nano silica to epoxy silane coupling agent hydrolysate at a mass-volume ratio of 1g / 50mL, stir and react for 2h to obtain coupling agent modified nano silica.

[0067] The coupling agent-modified nano-silica was added to a 3% tetraethylenepentamine aqueous solution at a mass-volume ratio of 1 g / 60 mL, heated to 80 °C, and stirred for 3 h to obtain aminated nano-silica.

[0068] 2) Mix polypropylene glycol, dichlorodiphenylmethane diamine and aminated nano-silica evenly according to a mass ratio of 20:5:3, then add tetrahydrofuran, with a mass-volume ratio of 1 g / 500 mL of polypropylene glycol to tetrahydrofuran, heat to 53 °C, then add isocyanate, with a mass ratio of 1:2 of polypropylene glycol to isocyanate, and stir for 20 min.

[0069] 3) Pour the above reaction solution into a mold, vulcanize at 80°C for 3 hours, and then cure at room temperature for 10 days to obtain a polyurethane film layer.

[0070] The fiberglass plain weave fabric layer undergoes modification treatment, including the following steps:

[0071] 3) Add polyvinyl acetate to anhydrous ethanol, heat and stir to dissolve, prepare a polyvinyl acetate solution with a mass concentration of 5%, and then add an ethanol solution with a concentration of 30wt% sodium hydroxide dropwise for alcoholysis for 20min. The volume ratio of sodium hydroxide solution to polyvinyl acetate solution is 1:30.

[0072] 2) Add glutaraldehyde to the alcoholysis polyvinyl acetate solution, the amount of glutaraldehyde added is 1.2 wt% of the alcoholysis polyvinyl acetate solution, stir evenly, and then immerse the glass fiber fabric in the above solution at a bath ratio of 1:50. Add hydrochloric acid solution to adjust the pH value of the solution to 3, heat to 40℃ and react for 8 minutes. After taking out the glass fiber fabric, dry it at 70℃ to obtain the glass fiber fabric intermediate.

[0073] 3) Place the glass fiber fabric intermediate in a 20wt% sodium hydroxide aqueous solution at a bath ratio of 1:30, then heat to 45℃ and react for 2.5h. After removing the glass fiber fabric intermediate, dry it at 50℃ to obtain the final product.

[0074] Example 4

[0075] A method for preparing shape memory composite materials includes the following steps:

[0076] A polytetrafluoroethylene (PTFE) release cloth is laid on a clean metal base plate. Then, from bottom to top, three layers of polyurethane film, a lower carbon fiber fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, an upper carbon fiber fabric layer, and the three layers of polyurethane film are laid in sequence. The metal base plate is then placed on a molding press platform for hot pressing. The hot pressing parameters are: pressure 10 MPa, temperature 160°C, time 60 min. After cooling to below 45°C, a shape memory composite material is obtained.

[0077] The method for preparing a polyurethane thin film layer includes the following steps:

[0078] 1) Add silane coupling agent KH560 to deionized water at a mass ratio of 1:30, heat to 50℃, and stir to obtain epoxy silane coupling agent hydrolysate. Then add nano silica to epoxy silane coupling agent hydrolysate at a mass-volume ratio of 1g / 50mL, stir and react for 2h to obtain coupling agent modified nano silica.

[0079] The coupling agent-modified nano-silica was added to a 3% tetraethylenepentamine aqueous solution at a mass-volume ratio of 1 g / 60 mL, heated to 80 °C, and stirred for 3 h to obtain aminated nano-silica.

[0080] 2) Mix polypropylene glycol, dichlorodiphenylmethane diamine and aminated nano-silica evenly according to a mass ratio of 20:5:3, then add tetrahydrofuran, with a mass-volume ratio of 1 g / 500 mL of polypropylene glycol to tetrahydrofuran, heat to 55 °C, then add isocyanate, with a mass ratio of 1:2 of polypropylene glycol to isocyanate, and stir for 20 min.

[0081] 3) Pour the above reaction solution into a mold, vulcanize at 80°C for 3 hours, and then cure at room temperature for 10 days to obtain a polyurethane film layer.

[0082] The fiberglass plain weave fabric layer undergoes modification treatment, including the following steps:

[0083] 4) Add polyvinyl acetate to anhydrous ethanol, heat and stir to dissolve, prepare a polyvinyl acetate solution with a mass concentration of 5%, and then add an ethanol solution with a concentration of 30wt% sodium hydroxide dropwise for alcoholysis for 20min. The volume ratio of sodium hydroxide solution to polyvinyl acetate solution is 1:30.

[0084] 2) Add glutaraldehyde to the alcoholysis polyvinyl acetate solution, the amount of glutaraldehyde added is 1.6 wt% of the alcoholysis polyvinyl acetate solution, stir evenly, and then immerse the glass fiber fabric in the above solution at a bath ratio of 1:50. Add hydrochloric acid solution to adjust the pH value of the solution to 3, heat to 40℃ and react for 8 minutes. After taking out the glass fiber fabric, dry it at 70℃ to obtain the glass fiber fabric intermediate.

[0085] 3) Place the glass fiber fabric intermediate in a 20wt% sodium hydroxide aqueous solution at a bath ratio of 1:30, then heat to 50℃ and react for 3 hours. After removing the glass fiber fabric intermediate, dry it at 50℃ to obtain the final product.

[0086] Example 5

[0087] A method for preparing shape memory composite materials includes the following steps:

[0088] A polytetrafluoroethylene (PTFE) release cloth is laid on a clean metal base plate. Then, from bottom to top, three layers of polyurethane film, a lower carbon fiber fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 45° glass fiber plain weave fabric layer, a polyurethane film layer, a 0° glass fiber plain weave fabric layer, a polyurethane film layer, an upper carbon fiber fabric layer, and the three-layer polyurethane film layer are laid in sequence. The metal base plate is then placed on a molding press platform for hot pressing. The hot pressing parameters are: pressure 2 MPa, temperature 80°C, time 30 min, and then cooled to below 45°C to obtain a shape memory composite material.

[0089] The method for preparing a polyurethane thin film layer includes the following steps:

[0090] 1) Add silane coupling agent KH560 to deionized water at a mass ratio of 1:30, heat to 50℃, and stir to obtain epoxy silane coupling agent hydrolysate. Then add nano silica to epoxy silane coupling agent hydrolysate at a mass-volume ratio of 1g / 50mL, stir and react for 2h to obtain coupling agent modified nano silica.

[0091] The coupling agent-modified nano-silica was added to a 3% tetraethylenepentamine aqueous solution at a mass-volume ratio of 1 g / 60 mL, heated to 80 °C, and stirred for 3 h to obtain aminated nano-silica.

[0092] 2) Mix polypropylene glycol, dichlorodiphenylmethane diamine and aminated nano-silica evenly according to a mass ratio of 20:5:3, then add tetrahydrofuran, with a mass-volume ratio of 1 g / 500 mL of polypropylene glycol to tetrahydrofuran, heat to 50 °C, then add isocyanate, with a mass ratio of 1:2 of polypropylene glycol to isocyanate, and stir for 20 min.

[0093] 3) Pour the above reaction solution into a mold, vulcanize at 80°C for 3 hours, and then cure at room temperature for 10 days to obtain a polyurethane film layer.

[0094] The fiberglass plain weave fabric layer undergoes modification treatment, including the following steps:

[0095] 5) Add polyvinyl acetate to anhydrous ethanol, heat and stir to dissolve, prepare a polyvinyl acetate solution with a mass concentration of 5%, and then add an ethanol solution with a concentration of 30wt% sodium hydroxide dropwise for alcoholysis for 20min. The volume ratio of sodium hydroxide solution to polyvinyl acetate solution is 1:30.

[0096] 2) Add glutaraldehyde to the alcoholysis polyvinyl acetate solution, the amount of glutaraldehyde added is 0.8 wt% of the alcoholysis polyvinyl acetate solution, stir evenly, and then immerse the glass fiber fabric in the above solution at a bath ratio of 1:50. Add hydrochloric acid solution to adjust the pH value of the solution to 3, heat to 40℃ and react for 8 minutes. After taking out the glass fiber fabric, dry it at 70℃ to obtain the glass fiber fabric intermediate.

[0097] 3) Place the glass fiber fabric intermediate in a 20wt% sodium hydroxide aqueous solution at a bath ratio of 1:30, then heat to 40℃ and react for 2 hours. After removing the glass fiber fabric intermediate, dry it at 50℃ to obtain the final product.

[0098] Comparative Example 1

[0099] The difference between Comparative Example 1 and Example 1 is as follows:

[0100] In the preparation of shape memory composite materials, the lower carbon fiber fabric layer and the lower carbon fiber fabric layer are not stacked, and the remaining operation steps are the same as in Example 1.

[0101] Comparative Example 2

[0102] The difference between Comparative Example 2 and Example 1 is as follows:

[0103] No glass fiber plain weave fabric layers are stacked during the preparation of shape memory composite materials.

[0104] The remaining operating steps are the same as in Example 1.

[0105] Comparative Example 3

[0106] The difference between Comparative Example 3 and Example 1 is as follows:

[0107] Step 1) is omitted during the preparation of the polyurethane thin film layer.

[0108] Replace the aminated nano-silica in step 2) with ordinary nano-silica.

[0109] The remaining operating steps are the same as in Example 1.

[0110] Comparative Example 4

[0111] The difference between Comparative Example 4 and Example 1 is as follows:

[0112] The fiberglass plain weave fabric layer has not undergone any modification treatment.

[0113] The remaining operating steps are the same as in Example 1.

[0114] Comparative Example 5

[0115] The difference between Comparative Example 5 and Example 4 is as follows:

[0116] In the modification treatment method of glass fiber plain weave fabric layer,

[0117] The amount of glutaraldehyde added was 1.7 wt% of the alcoholysis polyvinyl acetate solution.

[0118] The remaining operating steps are the same as in Example 4.

[0119] Performance testing

[0120] 1. Mechanical strength test:

[0121] The sheet-like shape memory composite material was cut into dumbbell shapes according to GB / T1040-92 standard, with a length L = 115 mm, a length L1 = 33 mm for the middle parallel narrow strip, a width W = 25 mm at the end, a width W0 = 6 mm for the narrow section, and a sample thickness D = 2 mm. The tensile strength of the shape memory composite material was tested according to GB / T9341-2008 test method (tensile rate 2 mm / min), and the impact resistance of the shape memory composite material was tested according to GB / T1043.1-2008 (pendulum energy 4 J). The test structure is shown in Table 1.

[0122] Table 1:

[0123]

[0124] 2. Stiffness test

[0125] The stiffness of shape memory composites is characterized by the elastic modulus. The larger the elastic modulus, the higher the stiffness of the shape memory composite. The elastic modulus was tested according to the method in GB / T 1040.1-2006, and the test results are shown in Table 2.

[0126] Table 2

[0127]

[0128] 3. Shape memory performance test

[0129] The shape memory properties of composite materials were tested using the bending method. The specific method involved cutting the sample into strips of 100mm x 20mm x 2mm and heating them in an oven at a predetermined temperature for 5 minutes to soften them. To ensure uniform deformation, the strips were placed in a 10mL beaker and bent into a "U" shape, with the bending angle recorded as 180°. The beaker was then quickly placed in an ice-water bath (5℃) and cooled for 5 minutes. The strips were then removed and left at room temperature for 2 hours. The shape recovery of the sample was observed, and the bending angle at this point was recorded as N1. Finally, the strips were placed back into the oven at the predetermined temperature, and the timing was started to observe the angle recovery until the angle no longer changed; this bending angle was recorded as N2. The shape fixation and shape recovery of the material were calculated using the following formula:

[0130] Shape fixation (%) = N1 / 180° x 100%;

[0131] Shape resilience (%) = (180° - N2) / 180° x 100%;

[0132] The test and calculation results are shown in Table 3.

[0133] Table 3:

[0134]

[0135] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A shape memory composite material, characterized in that, The system comprises an upper composite layer (100), an intermediate layer (200), and a lower composite layer (300) stacked sequentially. The upper composite layer is connected to the intermediate layer, and the intermediate layer is connected to the lower composite layer, respectively, by polyurethane film layers (400). The upper composite layer includes an upper carbon fiber fabric layer (101) and several polyurethane film layers (400) stacked on the carbon fiber fabric layer. The intermediate layer includes several stacked glass fiber fabric layers (201), which are connected to each other by polyurethane film layers (400). The lower composite layer includes several stacked polyurethane film layers (400) and a lower carbon fiber fabric layer (301) stacked on the polyurethane film layer. The intermediate layer has four layers of glass fiber fabric, and the top and bottom layers of glass fiber fabric in the intermediate layer are 0° plain weave fabric, while the two middle layers are 45° plain weave fabric. The method for preparing the polyurethane thin film layer includes the following steps: 1) Add nano-silica to the hydrolysate of epoxy silane coupling agent and stir to react to obtain coupling agent modified nano-silica. Add the coupling agent modified nano-silica to tetraethylenepentamine solution and heat to react to obtain aminated nano-silica. 2) Mix polypropylene glycol, dichlorodiphenylmethane diamine and aminated nano-silica evenly, then add tetrahydrofuran, heat to 50-55℃, then add isocyanate and stir to react; 3) Pour the above reaction solution into a mold, and then perform vulcanization and curing in sequence to obtain a polyurethane film layer; The glass fiber fabric layer in the intermediate layer undergoes a modification treatment, including the following steps: 1) Polyvinyl acetate was added to anhydrous ethanol and heated and stirred to dissolve it, resulting in a polyvinyl acetate solution. Then, sodium hydroxide solution was added dropwise to partially alcoholyze the polyvinyl acetate, resulting in an alcoholyzed polyvinyl acetate solution. 2) Add glutaraldehyde to the alcoholysis polyvinyl acetate solution and stir well. Then immerse the glass fiber fabric in the solution, add hydrochloric acid solution to adjust the pH of the solution to acidic, heat to 40℃ and react for 8 minutes. Remove the glass fiber fabric and dry it to obtain the glass fiber fabric intermediate. The amount of glutaraldehyde added is 0.8-1.6 wt% of the alcoholysis polyvinyl acetate solution. 3) Place the glass fiber fabric intermediate in a sodium hydroxide solution, then heat it to react. After removing the glass fiber fabric intermediate, dry it to obtain the final product.

2. The shape memory composite material according to claim 1, characterized in that, The upper carbon fiber fabric layer in the upper composite layer is a 3K plain weave carbon fiber fabric, and the polyurethane film layer stacked on the upper carbon fiber fabric layer has 3 layers.

3. The shape memory composite material according to claim 1, characterized in that, The lower composite layer has three polyurethane film layers, and the lower carbon fiber fabric layer is a 3K plain weave carbon fiber fabric.

4. The shape memory composite material according to claim 1, characterized in that, The heating temperature in step 3) of the modified glass fiber fabric layer in the intermediate layer is 40-45℃, and the heating reaction time is 2-3h.

5. A method for preparing a shape memory composite material as described in any one of claims 1-4, characterized in that, Includes the following steps: A polytetrafluoroethylene (PTFE) release cloth is laid on a clean metal base plate. Then, from bottom to top, the lower composite layer, polyurethane film layer, intermediate layer, polyurethane film layer, and upper composite layer are laid in sequence. The metal base plate is then placed on a molding machine platform for hot pressing. The hot pressing parameters are: pressure 2-10 MPa, temperature 80-160℃, and time 30-60 min. After cooling to below 45℃, the shape memory composite material is obtained.

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