Multiscale structural design method for self-healing composites with high energy loss modulus

Abstract

The present invention discloses a multi-scale structural design method for a self-healing composite material with a high energy dissipation modulus. After epoxy resin and glutaric anhydride are cross-linked and cured, an ester exchange reaction occurs under the catalysis of zinc acetylacetonate to obtain a self-healing resin, so that the macromolecules of the exchangeable network exhibit complementary and interlocking interactions, forming an intermolecular thermodynamic equilibrium state; nanoparticles are used as fillers and doped into the self-healing resin matrix to improve the stiffness and damping performance, thereby serving as a structural damping phase material; cast iron is used as the structural phase material, and the energy of the bending wave is concentrated at the minimum thickness through a structural phase whose thickness gradually changes according to a power law function, generating dynamic deformation. This deformation is pressed into the structural damping phase, causing the structural damping phase material to relax, generate inelastic deformation, dissipate mechanical energy, and complete irreversible energy dissipation. The structural phase using cast iron as the material ensures the stiffness performance of the material, thereby achieving improved damping performance while ensuring high stiffness of the material.

Description

Technical Field

[0001] The present invention belongs to the field of composite materials, and more specifically, relates to a multi-scale structural design method of a self-healing composite material with a high energy loss modulus. Background Art

[0002] Mechanical vibration is a common problem in aerospace, automotive and other fields, and the energy generated by vibration needs to be dissipated through the material. Therefore, for most structural materials, it is crucial to have both high stiffness and high damping. The stiffness of a material refers to the ability of a structure to resist elastic deformation when subjected to force, while the damping of a material refers to the conversion of mechanical energy into heat or other energy through inelastic deformation. However, stiffness and damping are usually two mutually exclusive properties, that is, materials with good stiffness usually have poor damping properties (such as metals), and materials with high loss factors tend to be weak in stiffness (such as rubber). Structural damping composite materials aim to achieve both high stiffness and high damping properties, and to achieve a balance between their structural function and damping properties.

[0003] In order to characterize the comprehensive performance of stiffness and damping of structural damping composite materials, the product of elastic modulus E (storage modulus E' is used in dynamic conditions) and loss factor tanδ (or η) (E×η, also known as energy dissipation modulus) is used as the figure of merit to characterize the comprehensive performance of stiffness and damping of structural damping composite materials. The energy dissipation modulus limit value of traditional engineering materials and biomaterials is about 600 MPa.

[0004] The essence of composite material damping is the emergence of two or more components complementing, interacting, and constraining each other according to a specific structural arrangement. Therefore, the damping phenomenon is essentially the interaction between the component structures, namely the structural hysteresis effect. This is because the interaction forces between elementary particles at the microscopic level are conservative (reversible), but materials constructed from a large number of elementary particles through multi-scale, multi-level substructuring methods have internal adhesion, sliding, and indentation effects, resulting in inelastic deformation that can dissipate mechanical energy (irreversible), thereby transforming the microscopic conservative system into a damped non-conservative system. It is worth noting that the dissipation of mechanical energy is inevitably accompanied by changes in the storage modulus (dynamic stiffness). Therefore, the structural hysteresis effect can also be viewed as a combined phenomenon of stiffness and damping.

[0005] In order to reduce the adverse vibration of traditional engineering materials and biomaterials in engineering, the damping performance of the material is often improved at the expense of the stiffness performance. However, there is still a lack of reasonable design methods to resolve the conflict between material stiffness and damping. Summary of the Invention

[0006] In response to the above-mentioned deficiencies or improvement needs of the prior art, the present invention provides a multi-scale structural design method for a self-healing composite material with a high energy loss modulus. In order to obtain a high energy loss modulus structure, the problem of the inability to balance the damping and stiffness properties of structural damping composite materials is solved from multiple scale designs. To achieve the above-mentioned objectives, according to a first aspect of the present invention, a multi-scale structural design method for a self-healing composite material with a high energy loss modulus is provided, comprising:

[0007] S1, mixing epoxy resin and multi-walled carbon nanotubes and stirring, then adding zinc acetylacetonate, and stirring under heating conditions until the zinc acetylacetonate powder is completely dissolved;

[0008] S2, cooling the mixed solution obtained in S1, adding glutaric anhydride and stirring to obtain a structural damping phase solution;

[0009] S3, injecting the structural damping phase solution into a mold, heating and curing it, and then demoulding it to obtain a structural damping phase specimen;

[0010] S4, pasting the structural damping phase specimen into the groove of the structural phase to obtain a self-healing composite unit cell;

[0011] In which, the shape of the mold is the same as that of the structural phase specimen, the material of the structural phase specimen is cast iron, and the curved surface of the groove gradually changes according to the power law function; the structural phase specimen and the structural damping phase specimen are both symmetrical about the center plane of the self-healing composite material unit cell; the center plane is a cross section passing through the center point of the self-healing composite material.

[0012] Preferably, in S1, the epoxy resin and the multi-walled carbon nanotubes are mixed and stirred for 3 hours under a mechanical stirrer at a rotation speed of 1500 to 2000 r / min.

[0013] Preferably, in S1, after zinc acetylacetonate is added, magnetic stirring is performed at a speed of 700 r / min, and heating is performed to 150° C. while stirring until the zinc acetylacetonate powder is completely dissolved.

[0014] Preferably, in S2, the mixed solution obtained in S1 is cooled to 50°C, glutaric anhydride is added, and the mixture is electromagnetically stirred at a speed of 700 r / min until a homogeneous system is formed to obtain a structural damping phase solution.

[0015] Preferably, in S3, the temperature rising and curing process is: 100°C for 2 hours—130°C for 2 hours—160°C for 1 hour.

[0016] Preferably, in S3, before performing temperature raising and curing, the process further includes: performing a vacuum treatment.

[0017] Preferably, in S3, before injecting the structural damping phase solution into the mold, the process further includes: applying a layer of release agent on the surface of the mold, and then placing the mold in a vacuum constant temperature box and heating it at 50° C. for 30 minutes.

[0018] According to a second aspect of the present invention, a self-healing composite material with a high energy loss modulus is provided. The self-healing composite material is prepared by the method described in the first aspect.

[0019] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0020] The multi-scale design method of the self-healing composite material structure with high energy dissipation modulus provided by the present invention can improve the damping performance of the material while ensuring high stiffness. The multi-scale design mechanism is as follows: Figure 1 As shown:

[0021] On a microscopic scale, by adding a curing agent, discrete molecular clusters are effectively aggregated together so that the cross-linking density of the polymer network is increased. In addition, there need to be enough catalysts to catalyze the transesterification reaction and introduce a self-healing function. For self-healing materials, the introduction of weaker dynamic reversible covalent bonds causes the polymer to preferentially break when subjected to a tensile external force, and automatically repairs and forms a new chain. The reconnection of the polymer chain is also an energy-consuming process. In the present invention, epoxy resin and glutaric anhydride are cross-linked and cured, and then an ester exchange reaction occurs under the catalysis of zinc acetylacetonate to obtain a self-healing resin, so that the macromolecules of the self-healing resin exchangeable network appear complementary, interlocking and other interactions, forming an intermolecular thermodynamic equilibrium state. Therefore, when mechanical energy is applied, the suspended chains on the nanoscale will produce phenomena such as slippage, entanglement, and diffusion, thereby increasing the viscous damping between the molecular chains.

[0022] At the mesoscopic scale, nanoparticles can effectively inhibit the generation and expansion of microcracks. At the same time, through chemical bonds or physical adsorption on polymer chains, the particles and the polymer network extend and cross-link, eliminating the interfacial energy difference between the two, thereby achieving the purpose of increasing rigidity and toughness. Therefore, nanoparticles are used as fillers and doped into the self-healing resin matrix to improve the stiffness and damping properties of the self-healing material. In the present invention, a healing resin (EP) is used as the matrix phase and multi-walled carbon nanotubes (MWCNTs) are used as the reinforcing phase. A structural damping phase material (MWCNTs / EP) is prepared by doping the reinforcing phase into the matrix phase. Although there is an internal force between the two phases, an equilibrium state can be reached through mutual complementation, interaction and compatibility. The strain generated at this time is elastic strain. However, when there is an external force, the system is in a non-equilibrium state, and the material will produce additional inelastic strain. Since carbon nanotubes and self-healing resins have different elastic moduli, stress jumps will occur at the interface. The material will produce a relaxing "driving force", resulting in adhesion, sliding and indentation effects between interfaces, thereby providing sufficient interface damping to increase dissipation and ensure the stiffness performance of the material, thereby completing the composite characteristic structure design of the material at the mesoscopic scale.

[0023] At the microscopic scale, according to the wave equation for flexural waves, as the thickness of a structure decreases during vibration, the wave velocity decreases, the wavelength decreases, and the wave amplitude increases. When the thickness of the structure decreases to zero, the wave velocity reaches zero, and the wave cannot propagate further, achieving zero reflection. Energy is concentrated at the minimum thickness point, causing the structure to dynamically deform. This deformation provides the "driving force" for relaxation of the structural damping phase, thereby utilizing the structural damping phase material to achieve energy dissipation. In the present invention, cast iron is used as the structural phase material. Through a structural phase whose thickness gradually changes according to a power-law function, the energy of the flexural wave is concentrated at the minimum thickness point, generating dynamic deformation. This deformation presses into the structural damping phase, providing the "driving force" for relaxation, transforming the microscopic conservative system into a damped non-conservative system. This causes the structural damping phase material to relax, produce inelastic deformation, and dissipate mechanical energy, thereby achieving irreversible energy dissipation. Furthermore, the cast iron structural phase also ensures the material's stiffness performance.

[0024] On a macroscopic scale, the self-healing composite unit cell is periodically expanded according to structures such as beams or plates. When an external driving force is applied, the mechanical energy of the non-conservative system is dissipated through the structural damping phase of multiple self-healing composite unit cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A diagram showing the loss mechanism of the self-healing composite material provided by an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of a unit cell of a self-healing composite material provided by an embodiment of the present invention;

[0027] Figure 3 An axonometric view of a structural phase specimen of a unit cell of a self-healing composite material provided by an embodiment of the present invention;

[0028] Figure 4 A top view of a unit cell matrix phase of a self-healing composite material provided by an embodiment of the present invention;

[0029] Figure 5 A cross-sectional view of a unit cell matrix phase of a self-healing composite material provided by an embodiment of the present invention;

[0030] Figure 6 is the graph of the power law function;

[0031] Figure 7 An isometric view of a damping phase specimen of a self-healing composite unit cell structure provided by an embodiment of the present invention;

[0032] Figure 8 A diagram showing a calculation model for the unit cell loss factor of a self-healing composite material provided by an embodiment of the present invention;

[0033] Figure 9 A diagram showing a calculation model for the elastic modulus of a unit cell of a self-healing composite material provided in an embodiment of the present invention;

[0034] Figure 10 A diagram of calculation results provided by an embodiment of the present invention;

[0035] Figure 11 A comparison chart of energy loss modulus provided by an embodiment of the present invention;

[0036] Figure 12 This is a position diagram of the self-healing composite material provided by an embodiment of the present invention in the stiffness and damping diagram. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0038] An embodiment of the present invention provides a multi-scale structural design method for a self-healing composite material with a high energy loss modulus, comprising:

[0039] S1, mixing epoxy resin and multi-walled carbon nanotubes and stirring, then adding zinc acetylacetonate, and stirring under heating conditions until the zinc acetylacetonate powder is completely dissolved;

[0040] S2, cooling the mixed solution obtained in S1, adding glutaric anhydride and stirring to obtain a structural damping phase solution;

[0041] S3, injecting the structural damping phase solution into a mold, heating and curing it, and then demoulding it to obtain a structural damping phase specimen;

[0042] S4, pasting the structural damping phase specimen into the groove of the structural phase to obtain a self-healing composite unit cell;

[0043] In which, the shape of the mold is the same as the shape of the structural phase, the material of the structural phase specimen is cast iron, and the curved surface of the groove gradually changes according to the power law function; the structural phase specimen and the structural damping phase specimen are both symmetrical about the center plane of the self-healing composite material unit cell; the center plane is a cross section passing through the center point of the self-healing composite material.

[0044] Preferably, in S1, the epoxy resin and the multi-walled carbon nanotubes are mixed and stirred for 3 hours under a mechanical stirrer at a rotation speed of 1500 to 2000 r / min.

[0045] Preferably, in S1, after zinc acetylacetonate is added, magnetic stirring is performed at a speed of 700 r / min, and heating is performed to 150° C. while stirring until the zinc acetylacetonate powder is completely dissolved.

[0046] Preferably, in S2, the mixed solution obtained in S1 is cooled to 50°C, glutaric anhydride is added, and the mixture is electromagnetically stirred at a speed of 700 r / min until a homogeneous system is formed to obtain a structural damping phase solution.

[0047] Preferably, in S3, the temperature rising and curing process is: 100°C for 2 hours—130°C for 2 hours—160°C for 1 hour.

[0048] Preferably, in S3, before performing the temperature-raising and curing, the method further includes: performing a vacuum treatment to remove bubbles in the structural damping phase solution.

[0049] Preferably, in S3, before injecting the structural damping phase solution into the mold, the process further includes: applying a layer of release agent on the surface of the mold, and then placing the mold in a vacuum constant temperature box and heating it at 50° C. for 30 minutes.

[0050] Specifically, first, the structural phase specimen of the self-healing composite material is designed:

[0051] The structural diagram of the self-healing composite material unit cell is shown in Figure 2 As shown, the unit cell consists of a structural phase and a structural damping phase that are symmetrical about its central plane. The overall size is 880mm×880mm×245mm. The axonometric diagram of the structural phase specimen is shown in Figure 3 As shown, the top view of the structural phase specimen is as follows Figure 4, the cross-sectional view is as follows Figure 5 , the profile curve is a power law function such as Figure 6 As shown, the power law function is:

[0052]

[0053] Where b is the power-law polynomial coefficient, m is the thickness variation exponent, and h1 is the cutoff thickness. In the present invention, to achieve better energy concentration, b is set to 1, m is set to 2, h1 is set to 0m, r1 = 0.04m, r2 = 0.35m, and r3 = 0.4m. The internal groove of the structural phase and the outer surface of the structural damping phase have the same power-law curve, so the structural phase can be used as a mold for the structural damping phase.

[0054] Secondly, a structural damping phase solution of a self-healing composite material is designed. The structural damping phase solution has a self-healing resin (EP) as a matrix, multi-walled carbon nanotubes (MWCNTs) as a reinforcement phase, glutaric anhydride as a curing agent, and zinc acetylacetonate as a catalyst. The steps include:

[0055] (1) Calculate the mass of each material: Calculate the mass of the self-healing resin, glutaric anhydride and zinc acetylacetonate that needs to be added based on the mass of the required structural damping phase material and the molecular weights of the self-healing resin, glutaric anhydride and zinc acetylacetonate.

[0056] (2) Preparation of a homogeneous solution: Add the calculated multi-walled carbon nanotubes to a beaker, then pour epoxy resin into the beaker and mix. Stir the mixed solution under a mechanical stirrer for 3 hours at a speed of 1500-2000 r / min to ensure that the epoxy resin and MWCNT are fully mixed and form a homogeneous mixed solution. Then, add the weighed zinc acetylacetonate (catalyst) to the mixed solution. Stir the solution in the beaker magnetically at a speed of 700 r / min and heat to 150°C while stirring until the zinc acetylacetonate powder is completely dissolved.

[0057] (3) Adding curing agent: Let it stand at room temperature to cool down and measure its temperature with a thermometer. When the temperature drops below 80°C, place the beaker on a heating device and set the temperature to 50°C. Add glutaric anhydride and stir electromagnetically at 700 r / min until a homogeneous system is formed.

[0058] Finally, a structural damping phase with self-healing resin as the matrix and multi-walled carbon nanotubes as the reinforcement phase is prepared, and it is pasted into the groove of the structural phase to obtain a self-healing composite material unit cell.

[0059] (4) Heating the mold: Apply a layer of release agent on the surface of the structural damping phase mold, and then place the mold in a vacuum constant temperature box and heat it at 50°C for 30 minutes to help remove the subsequent bubbles. The structure of the structural damping phase mold is the same as that of the structural phase specimen.

[0060] (5) Injection molding: Use a syringe to draw in the prepared solution (try to suck in the solution at the bottom of the beaker, and there will be bubbles on the surface of the solution) and inject it into the mold.

[0061] (6) Vacuum to remove bubbles: Wear linen gloves, place the mold after injection molding into a vacuum drying oven, turn on the power switch, close the piston, and open the vacuum switch until the air pressure drops to -93KPa. Turn off the power, maintain the air pressure for 10 minutes, then open the piston to release air. Perform the vacuum treatment 2-3 times.

[0062] (7) Heating and curing: The temperature in the vacuum constant temperature box is adjusted, and the solution curing process is as follows: 100℃2h—130℃ / 2h—160℃ / 1h.

[0063] (8) Demolding: After the curing is completed, wait for the vacuum drying oven to cool to room temperature, then wear gloves and take the mold out of the constant temperature oven. After demolding, you will get Figure 7 Structural damping phase specimen of the self-healing composite material shown.

[0064] Finally, the above-mentioned structural damping phase specimen is pasted on Figure 3 The structure shown in the groove of the specimen is obtained as shown in the figure. Figure 8 The self-healing composite unit cell shown in the figure can be periodically expanded according to structures such as beams or plates based on actual application requirements.

[0065] The following is a calculation example, which verifies through numerical analysis that the multi-scale design method of the self-healing composite material with a high energy loss modulus of the present invention can improve the damping performance while ensuring high stiffness.

[0066] 1. Numerical calculation model

[0067] The overall spatial dimensions of the self-healing composite unit cell are 880mm × 880mm × 245mm. The structural phase material is cast iron (Iron), and the structural damping phase material is a new composite material MWCNTs / EP, which is based on a self-healing resin and doped with nanofillers such as carbon nanotubes. The structural damping phase specimen is pasted into the groove of the structural phase specimen. The modal strain energy method is used to calculate the loss factor of the periodic composite unit cell. The calculation model is as follows: Figure 8 The Young's modulus is calculated by multi-cell loading (five periodic cells). The calculation model is as follows: Figure 9 As shown in the figure, for comparative purposes, a control group was constructed using a unit cell composed of cast iron, rubber, and MWCNTs / EP as the dual-phase materials, as well as a unit cell composed of cast iron as the matrix material and aluminum (Al) as the structural damping material. The finite element software COMSOL was used to numerically analyze these structures and calculate the energy dissipation modulus.

[0068] 2. Analysis of calculation results

[0069] Depend on Figure 10 It can be seen that the self-healing composite unit cell with MWCNTs / EP as the structural damping phase material and cast iron as the structural phase material can achieve efficient accumulation of bending wave energy. Figure 11 It can be seen that the energy dissipation modulus of the self-healing composite unit cell is significantly higher than that of other control groups. According to the calculation results, the energy dissipation modulus of the self-healing composite near the modal order 25 is about 1.37GPa, the elastic modulus is 130GPa, which is much higher than the elastic modulus of the structural damping phase material MWCNTs / EP 1613MPa, and the loss factor is 0.11, which is much higher than the loss factor of the matrix material IRON 0.0006. The self-healing composite unit cell has both high stiffness and high damping performance, which is significantly higher than Figure 12 The figure of merit for the medium dissipation modulus is 600 MPa. Therefore, the unit cell of this self-healing composite material can utilize a specially configured structural phase to collect bending waves into a designated area. Then, through indentation deformation, it provides a driving force for relaxation of the structural damping phase material. This allows for efficient energy dissipation through the viscous damping and interfacial damping of the structural damping phase material, MWCNTs / EP, resulting in a high dissipation modulus for the overall structure.

[0070] In summary, the self-healing composite material with self-healing resin as the base material, carbon nanotubes doped with nanofillers as the structural damping phase material, and cast iron as the material and special configuration structure as the structural phase has a high energy loss modulus and self-healing function, can take into account the mechanical properties of high stiffness and high damping, and has high application value in vibration and noise reduction engineering.

[0071] An embodiment of the present invention provides a self-healing composite material with a high energy loss modulus. The self-healing composite material is prepared by the method described in any of the above embodiments.

[0072] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-scale structural design method for a self-healing composite material with a high energy loss modulus, characterized in that: include: S1, mixing epoxy resin and multi-walled carbon nanotubes and stirring, then adding zinc acetylacetonate, and stirring under heating conditions until the zinc acetylacetonate powder is completely dissolved; S2, cooling the mixed solution obtained in S1, adding glutaric anhydride and stirring to obtain a structural damping phase solution; S3, injecting the structural damping phase solution into a mold, heating and curing it, and then demoulding it to obtain a structural damping phase specimen; S4, pasting the structural damping phase specimen into the groove of the structural phase specimen to obtain a self-healing composite material unit cell; The shape of the mold is the same as that of the structural phase, the material of the structural phase specimen is cast iron, and the curved surface of the groove changes gradually according to a power law function. The structural phase specimen and the structural damping phase specimen are both symmetrical about the central plane of the self-healing composite unit cell; the central plane is a cross section passing through the center point of the self-healing composite material.

2. The method according to claim 1, wherein In S1, the epoxy resin and multi-walled carbon nanotubes were mixed and stirred under a mechanical stirrer for 3 h at a speed of 1500-2000 r / min.

3. The method according to claim 1 or 2, wherein: After zinc acetylacetonate was added to S1, magnetic stirring was performed at a speed of 700 r / min and heating was performed to 150°C while stirring until the zinc acetylacetonate powder was completely dissolved.

4. The method according to claim 1, wherein In S2, the mixed solution obtained in S1 was cooled to 50°C, glutaric anhydride was added, and the mixture was electromagnetically stirred at a speed of 700 r / min until a homogeneous system was formed to obtain a structural damping phase solution.

5. The method according to claim 1 or 4, wherein: In S3, before the temperature-raising and curing, the process further includes: performing a vacuum treatment.

6. The method according to claim 1 or 4, wherein: In S3, before injecting the structural damping phase solution into the mold, the method further includes: applying a layer of release agent on the surface of the mold, and then placing the mold in a vacuum constant temperature box and heating it at 50° C. for 30 minutes.

7. A self-healing composite material with high energy loss modulus, characterized in that: The self-healing composite material is prepared by the method according to any one of claims 1 to 6.

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