Magnetorheological mastic suitable for landing cushion energy absorption of vtvl reusable rockets and method of making same

Abstract

The application discloses a magneto-rheological mortar suitable for VTVL reusable rocket landing buffer energy absorption and a preparation method thereof; the magneto-rheological mortar material is mainly composed of silicone rubber, fillers, magnetizable particles and surface activators with a mass ratio of 100:100:20-100:1-5. The application adopts an elastic mortar with silicone rubber as a main component as a carrier liquid of the magneto-rheological material, and refers to the preparation process of the elastic mortar material and the magneto-rheological material to prepare a new type of magneto-rheological material, i.e., the magneto-rheological mortar, so that the magneto-rheological mortar has the characteristics of the elastic mortar and the magneto-rheological material, the sealing requirement is reduced, the active control performance is improved, the magneto-rheological mortar can be reused, and the magneto-rheological mortar becomes a new material suitable for VTVL reusable launch vehicle landing buffers.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetorheological materials, and relates to a magnetorheological mortar suitable for VTVL reusable rocket landing cushioning and energy absorption, and a preparation method thereof. Background Art

[0002] According to the structural characteristics and working principles of the buffer, the general buffer can be divided into: spring buffer, friction buffer, rubber buffer, hydraulic buffer, gas-liquid buffer, elastic clay buffer, air buffer, etc.

[0003] Classification and characteristics of buffers

[0004] Currently, the buffers suitable for VTVL reusable launch vehicle landing are mainly honeycomb buffers and gas-liquid buffers. However, the gas-liquid buffer has a complex structure and high sealing requirements, while the honeycomb buffer cannot be reused. In addition, both buffers cannot perform active stroke control and have obvious defects.

[0005] Magnetorheological materials are intelligent materials whose mechanical properties undergo rapid, continuous, and reversible changes under an applied magnetic field. When a magnetic field is applied, the magnetorheological fluid rapidly changes from liquid to solid (in milliseconds). When the field is removed, it quickly returns to liquid form. They offer strong impact resistance and excellent seismic isolation.

[0006] Existing magnetorheological materials primarily include magnetorheological fluids and magnetorheological adhesives. Magnetorheological fluids have low viscosity, making magnetizable particles prone to sedimentation and even agglomeration, and have low shear yield stress. Magnetorheological adhesives or their matrix are solid, which limits the controllable range of magnetorheological elastomers.

[0007] The performance of the clay buffer is based on the reliability of the clay material. The key to developing the clay buffer is to develop an elastic clay material that meets the performance indicators such as viscosity, compression rate, high and low temperature, and glass transition temperature.

[0008] Elastic mortar material properties Summary of the Invention

[0009] The purpose of the present invention is to address the defects in the above-mentioned prior art that the existing VTVL reusable carrier rocket landing buffer mostly uses gas-liquid, honeycomb, etc. as buffer materials. Such materials can only passively absorb energy when impacted, cannot be actively controlled, and cannot actively adjust the buffer stroke. Therefore, they are not suitable for landing scenarios on the surface of extraterrestrial planets with high stability requirements and no pre-built landing sites, and landing scenarios at sea with complex sea conditions. The present invention provides a magnetorheological mortar suitable for VTVL reusable rocket landing buffer energy absorption and a preparation method thereof.

[0010] The object of the present invention is achieved through the following technical solutions:

[0011] The invention relates to a magnetorheological mortar material, which consists of silicone rubber, filler, magnetizable particles and surfactant; the mass ratio of the silicone rubber, filler, magnetizable particles and surfactant is 100:100:20-100:1-5.

[0012] In one embodiment of the present invention, the silicone rubber comprises methylphenyl silicone oil and methyl silicone oil, mixed by weight: 20-100% methylphenyl silicone oil and 80-20% methyl silicone oil. Dimethyl silicone oil offers advantages such as large molecular spacing, low surface tension, good hydrophobicity, and excellent barrier properties. It also possesses excellent lubricity, minimal viscosity change, and excellent heat and acid resistance. It also boasts a low freezing point, relatively stable chemical properties, a high boiling point, and superior shear resistance. Methylphenyl silicone oil has a higher viscosity-temperature coefficient and a lower freezing point than methyl silicone oils of the same viscosity, as well as better flash points and compression resistance. Its viscosity changes more rapidly under the same pressure, and it exhibits excellent high and low temperature resistance, maintaining fluidity even at -70°C. Adjusting the ratio of methylphenyl silicone oil to methyl silicone oil can adjust the viscosity and density of the mortar. The determination of viscosity and density depends on the operating conditions and the type of magnetizable particles selected. Specifically, to prevent aggregation of the magnetizable particles, the density of the mortar should be as close as possible to that of the magnetized particles. In addition, the viscosity of the mortar will also affect the performance of the magnetorheological mortar. As the viscosity increases, the maximum shear stress increases, and the range of variation of the shear stress adjusted by the magnetic field decreases.

[0013] As an embodiment of the present invention, the filler mainly includes a plasticizer, a filler and a compressive agent. Adding fillers can enhance or improve the thermal conductivity, lubricity, wear resistance, tear resistance and elasticity of the buffer mortar, while reducing the cost of the mortar.

[0014] In one embodiment of the present invention, the filler comprises graphite, wollastonite powder, and white carbon black in a mass ratio of 15±5%: 30±10%: 55±15%. Wollastonite powder, with the molecular formula of Ca₃Si₃O₄, is used to increase the shape stability of the mortar, improve its tensile strength, flexural strength, and shear strength, reduce its thermal expansion coefficient, and provide uniform dispersion within the mortar. In one embodiment of the present invention, the wollastonite powder has a particle size between 4 and 50 μm.

[0015] Graphite is a type of crystalline carbon with a relatively soft, slippery texture. Adding it to cement improves the surface interface, reduces friction with the buffer, and prolongs the life of the cement. The particle size is between 4 and 50 μm. In one embodiment of the present invention, the graphite particle size is between 4 and 50 μm.

[0016] White carbon black is silicon dioxide, and the average particle size of the white carbon black used for the reinforcement in silicone oil is 20-80 nm. As one embodiment of the present invention, the average particle size of the white carbon black is 20-80 nm.

[0017] The magnetic interaction between magnetizable particles under an applied magnetic field creates the magnetorheological effect, a key component of magnetorheological materials. Magnetizable particles, the primary component of magnetorheological materials, are typically made from ferrite, nickel, cobalt, and their composites. Compared to hard magnetic materials, soft magnetic materials exhibit enhanced magnetorheological effects due to their ease of magnetization and demagnetization, low remanence, and high magnetic saturation. Carbonyl iron powder, with its high magnetic permeability and excellent soft magnetic properties, is an ideal particle for preparing magnetorheological materials.

[0018] As one embodiment of the present invention, carbonyl iron powder with an average particle size of 1-10 microns is selected to prepare magnetorheological mortar. As the content of magnetizable particles increases, the adjustable range of shear stress becomes larger, and the maximum shear stress that can be achieved becomes larger. The content of magnetizable particles affects the response sensitivity of the magnetorheological mortar to an external magnetic field. The higher the content, the greater the range of shear stress variation with the magnetic field intensity, and the greater the maximum shear stress value. In the design, different magnetizable particles can be selected, and the corresponding shear stress range and maximum shear stress need to be determined experimentally.

[0019] Due to the density difference between the carrier liquid and the magnetizable particles, the magnetizable particles in the liquid magnetorheological material are prone to sedimentation under the influence of gravity, and may even become compacted, which can affect the performance of the magnetorheological material or even cause it to fail. Therefore, various additives are required when preparing magnetorheological materials. In one embodiment of the present invention, sodium dodecylbenzenesulfonate and sodium lauryl sulfate are selected as additives (surfactants) for preparing magnetorheological mortar. Other additives with similar functions may also be used in the specific implementation of the present invention.

[0020] The present invention also relates to a method for preparing a magnetorheological mortar material; the method comprises preparing a mortar carrier liquid, surface activation of magnetizable particles, and mixing the mortar carrier liquid and the magnetizable particles to prepare the magnetorheological mortar.

[0021] As one embodiment of the present invention, the preparation of the clay carrier liquid includes: adding silicone rubber according to a set mass percentage into a mixing device, with a rotation speed range of 100~250 r / min and a temperature of 40-90°C; adding filler in small amounts in multiple times and stirring thoroughly until it is visually uniformly dispersed, continuing stirring for 4 hours, and then cooling to room temperature to obtain the clay carrier liquid.

[0022] As an embodiment of the present application, the surface activation of the magnetizable particles comprises: adding a surface active agent to the magnetizable particles, stirring at 100-500 / min, then standing for 16-32h, removing the supernatant, and drying at 40-90℃ to obtain the activated magnetizable particles. In some specific examples, taking carbonyl iron powder as the magnetizable particles, the activation is as follows: adding a surface active agent sodium dodecyl benzene sulfonate to the surface-cleaned pure carbonyl iron powder, stirring at 100-500 / min, then standing for 24h, removing the supernatant, and drying at 40-90℃ to obtain the activated carbonyl iron powder.

[0023] As an embodiment of the present application, the preparation of the magnetorheological paste comprises: mixing the paste carrier liquid and the activated magnetizable particles, stirring at 100-300r / min for 6-10h to obtain the magnetorheological paste.

[0024] The present application also relates to the use of a magnetorheological paste material in the preparation of a bumper suitable for the landing of a VTVL reusable launch vehicle.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] The present application uses an elastic paste with a specific composition of main components of silicone rubber as the carrier liquid of the magnetorheological material, and refers to the preparation process of the elastic paste material and the magnetorheological material to prepare a new type of magnetorheological material, i.e., a magnetorheological paste, which has the characteristics of both the elastic paste and the magnetorheological material, reduces the sealing requirement, improves the active control performance, and can be reused, becoming a new material suitable for the landing bumper of a VTVL reusable launch vehicle. 2) The magnetorheological paste provided by the present application has good liquid sedimentation stability, large shear yield stress, wide controllable range of magnetorheological elastomers and magnetorheological plastic bodies, and good temperature stability, which can effectively improve the landing stability of a VTVL reusable launch vehicle. DETAILED DESCRIPTION

[0027] The present application will be described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present application. These all belong to the protection scope of the present application.

[0028] Example 1

[0029] This example relates to a magnetorheological paste material, which mainly comprises silicone rubber, filler, magnetizable particles and surface active agent. The specific composition is shown in Table 1.

[0030] The preparation method of the magnetorheological cement material of the embodiment includes cement carrier liquid preparation, surface activation of magnetizable particles, and mixing of the cement carrier liquid and the magnetizable particles to prepare the magnetorheological cement. The specific steps are as follows:

[0031] (1) Cement carrier liquid preparation: silicon rubber is put into a mixing device according to a set mass percentage, the rotating speed range is 100 r / min, and the temperature is 90°C; fillers are added in small amounts for fully stirring in multiple times, until visual dispersion is uniform, then stirring is continued for 3 h, and then cooling to room temperature to obtain the cement carrier liquid;

[0032] (2) Surface activation of magnetizable particles: a surfactant is added to the magnetizable particles, stirring is performed at 100 / min, then standing is performed for 32 h, supernatant is removed, and drying is performed at 40°C to obtain the activated magnetizable particles;

[0033] (3) Preparation of magnetorheological cement: the cement carrier liquid and the activated magnetizable particles are mixed, stirring is performed at 100 r / min for 10 h to prepare the magnetorheological cement.

[0034] Embodiment 2

[0035] The embodiment relates to a magnetorheological cement material, which mainly comprises silicon rubber, fillers, magnetizable particles, and a surfactant; and the specific composition is shown in Table 1.

[0036] The preparation method of the magnetorheological cement material of the embodiment includes cement carrier liquid preparation, surface activation of magnetizable particles, and mixing of the cement carrier liquid and the magnetizable particles to prepare the magnetorheological cement. The specific steps are as follows:

[0037] (1) Cement carrier liquid preparation: silicon rubber is put into a mixing device according to a set mass percentage, the rotating speed range is 200 r / min, and the temperature is 70°C; fillers are added in small amounts for fully stirring in multiple times, until visual dispersion is uniform, then stirring is continued for 4 h, and then cooling to room temperature to obtain the cement carrier liquid;

[0038] (2) Surface activation of magnetizable particles: a surfactant is added to the magnetizable particles, stirring is performed at 300 / min, then standing is performed for 24 h, supernatant is removed, and drying is performed at 65°C to obtain the activated magnetizable particles;

[0039] (3) Preparation of magnetorheological cement: the cement carrier liquid and the activated magnetizable particles are mixed, stirring is performed at 200 r / min for 8 h to prepare the magnetorheological cement.

[0040] Embodiment 3

[0041] The embodiment relates to a magnetorheological cement material, which mainly comprises silicon rubber, fillers, magnetizable particles, and a surfactant; and the specific composition is shown in Table 1.

[0042] The preparation method of the magnetorheological mortar material of this embodiment includes preparing a mortar carrier liquid, surface activation of magnetizable particles, and mixing the mortar carrier liquid and magnetizable particles to prepare the magnetorheological mortar. The specific steps are as follows:

[0043] (1) Preparation of the clay carrier liquid: Add the silicone rubber according to the set mass percentage into the mixing equipment, with a speed range of 250 r / min and a temperature of 40°C; add the filler in small amounts several times and stir thoroughly until it is visually uniformly dispersed, continue stirring for 5 hours, and then cool to room temperature to obtain the clay carrier liquid;

[0044] (2) Surface activation of magnetizable particles: Add surfactant to the magnetizable particles, stir at 500 / min, then let it stand for 16 h, remove the supernatant, and dry at 90°C to obtain activated magnetizable particles;

[0045] (3) Preparation of magnetorheological mortar: The mortar carrier liquid and the activated magnetizable particles were mixed and stirred at 300 r / min for 6 h to prepare magnetorheological mortar.

[0046] Comparative Examples 1-6

[0047] The specific composition of the magnetorheological mortar materials involved in Comparative Examples 1-6 is shown in Table 1; the preparation is the same as in Example 1.

[0048] Performance testing methods and objectives of each embodiment:

[0049] 1. Magnetorheological effect related tests

[0050] 1. Shear stress-magnetic field strength test

[0051] Purpose: To quantify the shear yield strength and magnetic response sensitivity of magnetorheological mortar under magnetic field.

[0052] Method: Use a rotational rheometer (such as Haake MARS) or parallel plate rheometer to measure the shear stress-shear rate curve of the material at different magnetic field strengths (0-2T), focusing on the zero-field viscosity and the yield stress at saturation magnetic field (typical values ​​need to reach 10-100kPa).

[0053] Key indicators: magneto-shear yield strength, hysteresis loop area (reflecting energy loss).

[0054] 2. Dynamic Mechanical Properties Test (DMA)

[0055] Objective: To analyze the storage modulus (G'), loss modulus (G'') and damping factor (tanδ) of magnetorheological mortar under alternating magnetic field.

[0056] Methods: A sinusoidal alternating magnetic field (frequency 0.1-100 Hz) was applied in dynamic shear mode. The changes in the dynamic mechanical parameters of the material under different magnetic fields were recorded and its frequency domain response characteristics were evaluated.

[0057] Application scenario: When used in vibration damping devices, it is important to focus on the adjustable range of G' with the magnetic field (usually requiring a change of ≥10 times).

[0058] 3. Response time and cycle stability test

[0059] Objective: To verify the real-time response capability and long-term reliability of magnetorheological mortar.

[0060] method:

[0061] Response time: Use a high-speed camera or strain sensor to measure the rise / fall time of shear stress when the magnetic field switches (e.g., 0→1T) (target value ≤10ms).

[0062] Cyclic test: Perform more than 1000 loading-unloading cycles under a fixed magnetic field and monitor the shear stress decay rate (required to be ≤5%).

[0063] 2. Basic mechanical properties test

[0064] 1. Static mechanical properties

[0065] Shear strength: A uniaxial shear testing machine is used to test the shear strength (typical value 5~20kPa) and elongation at break of the material under non-magnetic field conditions.

[0066] Compression / Tensile Properties: Use a universal testing machine (such as Instron) to measure compressive strength (target ≥50kPa), elastic modulus, and Poisson’s ratio to evaluate the material’s load-bearing capacity.

[0067] 2. Thixotropy and rheological properties

[0068] Purpose: To investigate the workability and storage stability of materials in the absence of a magnetic field.

[0069] Method: Through the "rotation rate ladder test" (such as 1→100→1s -1 ), draw the viscosity-time curve, calculate the thixotropic ring area, and evaluate the shear thinning and recovery ability.

[0070] 3. Stability and environmental adaptability test

[0071] 1. Anti-settling performance test

[0072] method:

[0073] Static sedimentation: Place the clay in a transparent container and store it at room temperature for 30 days. Use a laser particle size analyzer or layered density difference to evaluate the particle sedimentation rate (required to be ≤5%).

[0074] Centrifugal acceleration test: Centrifuge at 3000 rpm for 30 minutes and observe whether there is stratification or hard precipitation.

[0075] 2. Temperature resistance and aging resistance test

[0076] Temperature cycling: Perform 10 cycles (2 hours each) within the range of -40℃~120℃, and compare the magnetorheological effect and mechanical property attenuation before and after the test.

[0077] Damp-heat aging: Store at 85°C / 85% RH for 1000 hours to detect any performance degradation caused by carrier liquid volatilization or surfactant failure.

[0078] 3. Corrosion resistance and sealing performance

[0079] Medium compatibility: Soak the putty in hydraulic oil, water or acid-base solution (pH=3~11) and test the mass change rate and mechanical property retention rate after 7 days.

[0080] Sealing test: Fill the high pressure cavity with gas (0.5MPa) and observe the leakage of the cement as the sealing material (target ≤10 -3 Pa·m 3 / s).

[0081] 4. Microstructure and composition analysis

[0082] 1. Characterization of particle dispersion

[0083] Scanning electron microscopy (SEM): Observe the distribution of magnetic particles (such as carbonyl iron, ferrite) in the carrier liquid and evaluate the coating effect of the surfactant (the particle spacing must be uniform and there must be no obvious agglomeration).

[0084] X-ray diffraction (XRD): Analyze the crystal structure of magnetic particles and the lattice changes after surfactant modification to verify the interface bonding strength.

[0085] 2. Thermal analysis (DSC / TGA)

[0086] Differential Scanning Calorimetry (DSC): Measures the phase transition temperature of the carrier fluid and evaluates the thermodynamic stability of the material at high and low temperatures.

[0087] Thermogravimetric analysis (TGA): Test the mass loss rate of the cement in the range of 200℃~600℃ to determine the thermal decomposition temperature of the carrier liquid and surfactant (the initial decomposition temperature is required to be ≥200℃).

[0088] 5. Special application scenario testing

[0089] 1. Vibration damping performance test

[0090] Purpose: To verify the energy dissipation capacity of the mortar in actual vibration reduction scenarios.

[0091] Method: Fill the vibrating table bracket with clay, apply 10~100Hz sinusoidal vibration, and use the acceleration sensor to compare the vibration amplitude attenuation rate with and without the magnetic field (required to be ≥30%).

[0092] 2. Impact cushioning performance test

[0093] Drop hammer impact test: Use a Hopkinson bar or drop hammer device to test the absorption efficiency of the cement to the impact load under the action of a magnetic field (target energy absorption rate ≥80%).

[0094] 6. Industry Standards and Specifications Reference

[0095] General standards for magnetorheological fluids: Please refer to ISO 13318 (Test methods for magnetorheological fluid properties) and GB / T 37784-2019 (Terms and definitions for magnetorheological fluids).

[0096] Engineering application testing: The aerospace field must comply with NASA TM-2002-211777 (Standard for the adaptability of magnetorheological materials to space environments). Industrial equipment applications can refer to ASTM D7318 (Test method for dynamic properties of damping materials).

[0097] These tests comprehensively assess the material properties, environmental adaptability, and engineering applicability of magnetorheological mortar, providing data support for its application in dampers, seals, smart structures, and other fields. Actual testing requires adjustment of test parameters and indicators based on specific application scenarios (e.g., high loads, extreme temperatures, etc.). The magnetorheological mortars of the present invention (including Examples 1-3) have been tested and found to meet these criteria.

[0098] In the development of a certain type of reusable rocket, a multi-stage buffer technology solution was adopted, in which the magnetorheological clay energy absorber was used as the core component for design analysis and simulation verification:

[0099] Two-stage buffer design: The landing legs integrate magnetorheological mortar energy absorbers and traditional metal crush tubes. Analysis and verification show that during the rocket landing process, the magnetorheological mortar energy absorbers can absorb 60% of the impact energy and reduce the landing speed from 3m / s to 0.75m / s, while keeping the peak load within the structural safety range.

[0100] Optimization of material ratio: By adjusting the carbonyl iron powder content and magnetic field strength (0-1.2T), the storage modulus of the magnetorheological mortar can be adjusted within the range of 0.52-3.28MPa to meet the cushioning requirements of different landing masses (20-40 tons).

[0101] Comparative experiments were conducted on Examples 1-3 and the comparative example, and the test results are shown in Table 1.

[0102] Table 1 Composition and dosage of magnetorheological mortar materials in the examples and comparative examples (g)

[0103]

[0104] In addition, in low-gravity environments such as Mars and the Moon, magnetorheological clay energy absorbers can adapt to the buffering requirements under different gravitational accelerations by adjusting the magnetic field strength. For example, when landing on Mars, the energy absorption efficiency can be increased to 92% by increasing the content of carbonyl iron powder.

[0105] Compared with purely traditional energy absorption solutions, the weight of the magnetorheological mortar energy absorber using the magnetorheological mortar of the present invention (including Examples 1-3) can be reduced by 25%, and the performance degradation after 100 cyclic impact tests is less than 5%, meeting the stringent requirements for rocket reuse.

[0106] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A magnetorheological mortar material, characterized in that: The magnetorheological mortar material mainly consists of silicone rubber, filler, magnetizable particles and surfactant; the mass ratio of the silicone rubber, filler, magnetizable particles and surfactant is: 100:100:(20-100):(1-5); The silicone rubber is composed of methylphenyl silicone oil and methyl silicone oil, wherein the methylphenyl silicone oil is 20-80 wt.%, and the methyl silicone oil is 80-20 wt.%; The filler is selected from graphite: wollastonite powder: white carbon black in a mass ratio of 15±5%:30±10%:55±15%; The magnetizable particles are carbonyl iron powder with an average particle size of 1-10 microns.

2. The magnetorheological mortar material according to claim 1, characterized in that: Include at least one of the following technical features: A. The particle size of the wollastonite powder is 4-50 μm; B. The graphite particle size is 4-50 μm; C. The average particle size of the white carbon black is 20-80 nm.

3. The magnetorheological mortar material according to claim 1, characterized in that: The surfactant is selected from at least one of sodium dodecylbenzenesulfonate and sodium lauryl sulfate.

4. A method for preparing the magnetorheological mortar material according to any one of claims 1 to 3, characterized in that: The method comprises the steps of preparing a clay carrier liquid, activating the surface of magnetizable particles, and mixing the clay carrier liquid and the magnetizable particles to prepare magnetorheological clay.

5. The method for preparing the magnetorheological mortar material according to claim 4, characterized in that: Include at least one of the following technical features: The preparation of the mortar carrier liquid comprises: adding silicone rubber according to a set mass percentage into a mixing device, with a rotation speed ranging from 100 to 250 r / min and a temperature of 40-90°C; adding filler in small amounts several times and stirring thoroughly until it is visually uniformly dispersed, continuing stirring for 3-5 hours, and then cooling to room temperature to obtain the mortar carrier liquid; The surface activation of the magnetizable particles comprises: adding a surfactant to the magnetizable particles, stirring at 100-500 / min, then standing for 16-32 hours, removing the supernatant, and drying at 40-90° C. to obtain activated magnetizable particles; The preparation of the magnetorheological mortar comprises: mixing the mortar carrier liquid and the activated magnetizable particles, and stirring at 100-300 r / min for 6-10 hours to obtain the magnetorheological mortar.

6. Use of the magnetorheological mortar material according to any one of claims 1 to 3 in preparing a buffer suitable for landing a VTVL reusable launch vehicle.

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