An additive manufacturing method for strain rate enhanced composite gel

Abstract

This invention relates to an additive manufacturing method for strain rate-enhanced composite gels, comprising: a) polymerizing silicone oil, boric acid, and octanoic acid at high temperature to prepare a shear-hardening gel; b) introducing the shear-hardening gel into a polyvinyl alcohol aqueous solution and adding chitosan particles, followed by ball milling to obtain a composite gel precursor; c) printing the composite gel precursor using pneumatic extrusion combined with a triaxial motion control system, and then obtaining the composite gel through freeze-thaw treatment. This composite gel precursor is propelled from the nozzle by air pressure in a pneumatic extruder, and the triaxial motion control system enables the deposition of arbitrary two-dimensional patterns and the stacking of three-dimensional structures, overcoming the limitations of traditional strain rate-enhanced composite gels formed by molding and injection molding methods, and endowing it with greater molding freedom and higher molding precision in additive manufacturing.

Description

Technical Field

[0001] This invention belongs to the field of smart materials technology, specifically relating to an additive manufacturing method for strain rate-enhanced composite gels. Background Technology

[0002] Strain rate reinforced composite gels are a class of smart materials capable of rapidly and continuously adjusting their mechanical properties, such as modulus, stiffness, and damping, in response to external mechanical excitation frequencies. They have been widely used in impact protection and vibration control. However, traditional strain rate reinforced composite gels suffer from complex molding conditions and low precision. Chinese patent CN115772323A discloses a composite material with a strain rate reinforcing effect, obtained by blending a shear-thickening gel with silicone rubber and then high-temperature molding. Chinese patent CN114015182A discloses an impact-resistant composite hydrogel, prepared by cross-linking induced by ultraviolet irradiation. Additive manufacturing provides a feasible solution for optimizing the molding freedom and precision of strain rate reinforced composite gels.

[0003] Additive manufacturing, or 3D printing, is an emerging processing technology that obtains three-dimensional structural materials by layer-by-layer deposition. It boasts advantages such as high freedom, high precision, and fast processing speed, and typically includes direct ink writing (DIW), photopolymerization (DLP), fused deposition modeling (FDM), and selective laser sintering (SLS). However, due to the high damping factor of composite gel precursors, interlayer fusion and structural collapse can occur during layer-by-layer deposition, making the additive manufacturing of strain rate-enhanced composite gels extremely challenging. Therefore, to promote the application of strain rate-enhanced composite gels in direct ink writing 3D printing, performance enhancement through directional structural design, and other fields, it is necessary to develop an additive manufacturing method for strain rate-enhanced composite gels. Summary of the Invention

[0004] This invention improves upon the shortcomings of traditional technologies by providing an additive manufacturing method for strain rate reinforced composite gels. This method overcomes the limitations of traditional compression molding and injection molding methods for producing strain rate reinforced composite gels, granting them greater molding freedom and higher molding precision. The prepared strain rate reinforced composite gel exhibits high performance within 10... -1 -10 1 The elastic modulus is significantly improved at Hertzian shear frequency, and the printed structure can be widely used in fields such as impact protection.

[0005] An additive manufacturing method for a strain rate-enhanced composite gel according to the present invention includes the following steps:

[0006] a) Silicone oil, boric acid and octanoic acid are polymerized at high temperature to prepare a shear-hardening gel;

[0007] b) Introduce the shear-hardening gel prepared in step a) into a polyvinyl alcohol aqueous solution, add chitosan particles, and ball mill to obtain a composite gel precursor;

[0008] c) The composite gel precursor prepared in step b) is printed by pneumatic extrusion combined with a triaxial motion control system, and then the composite gel is obtained by freeze-thaw treatment.

[0009] Further, in step a), the raw material ratio is silicone oil: boric acid: octanoic acid = 10-40 g: 0.5-2 g: 25 μL; preferably, the raw material ratio is silicone oil: boric acid: octanoic acid = 10-40 g: 1 g: 25 μL.

[0010] Further, in step a), the high-temperature polymerization reaction temperature is 140–200 degrees Celsius; preferably, the high-temperature polymerization reaction temperature is 140–180 degrees Celsius.

[0011] Further, in step b), the specific preparation steps of the composite gel precursor are as follows: uniformly disperse the shear-hardening gel in ethanol to obtain a shear-hardening gel ethanol solution; dissolve polyvinyl alcohol in deionized water to obtain a polyvinyl alcohol aqueous solution; uniformly mix the shear-hardening gel ethanol solution and the polyvinyl alcohol aqueous solution to obtain a mixed system; add chitosan to the aforementioned mixed system, and obtain a homogeneous composite gel precursor by mechanical ball milling.

[0012] Further, in step b), the concentration of shear-hardening gel in the shear-hardening gel ethanol solution is 0.2 to 0.6 g / mL; preferably, the concentration of shear-hardening gel in the shear-hardening gel ethanol solution is 0.4 to 0.6 g / mL.

[0013] Further, in step b), the polyvinyl alcohol aqueous solution contains 6-18% polyvinyl alcohol by mass; preferably, the polyvinyl alcohol aqueous solution contains 6-14% polyvinyl alcohol by mass.

[0014] Further, in step b), the mass ratio of chitosan to the polyvinyl alcohol aqueous solution is 0 to 14:100; preferably, the mass ratio of chitosan to the polyvinyl alcohol aqueous solution is 8 to 14:100.

[0015] Further, in step b), the ratio of the shear-hardening gel ethanol solution to the polyvinyl alcohol aqueous solution is 10-30 ml: 100 g; preferably, the ratio of the shear-hardening gel ethanol solution to the polyvinyl alcohol aqueous solution is 15-25 ml: 100 g.

[0016] Further, in step b), the specific preparation steps of the composite gel precursor are as follows: the shear-hardening gel is dispersed in ethanol by ultrasonic treatment at a power of 53 kHz; polyvinyl alcohol is dissolved in deionized water by high-temperature mechanical stirring at a temperature of 90 degrees Celsius and a rotation speed of 400 rpm; 20 ml of the shear-hardening gel ethanol solution is added to 100 g of polyvinyl alcohol aqueous solution and mechanically stirred to mix it evenly at a rotation speed of 400 rpm; chitosan is added to the above-mentioned mixture and the homogeneous composite gel precursor is obtained by mechanical ball milling at a frequency of 20 Hz for 48 hours.

[0017] Further, in step c), the printing principle is a direct ink writing 3D printing process, and the pneumatic extruder control system controls the three-axis movement of the nozzle through automatic computer-aided design software, with an extrusion air pressure of 0.1-0.5 MPa and a printing speed of 3-50 mm / s; preferably, the printing principle is a direct ink writing 3D printing process, and the pneumatic extruder control system controls the three-axis movement of the nozzle through automatic computer-aided design software, with an extrusion air pressure of 0.1-0.3 MPa and a printing speed of 3-30 mm / s.

[0018] Further, in step c), the specific operation steps of the freeze-thaw treatment are as follows: transfer the printed composite gel precursor to a freezer at -20 degrees Celsius, freeze for 12 hours, and then thaw at room temperature for 4 hours.

[0019] The beneficial effects of this invention are:

[0020] (1) An additive manufacturing method for strain rate enhanced composite gel of the present invention can prepare a gel precursor with extrudable molding characteristics through high temperature crosslinking and mechanical blending. The precursor can be deposited with arbitrary two-dimensional patterns and stacked with three-dimensional structures by a pneumatic extruder under a three-axis motion control system. This overcomes the limitations of traditional strain rate enhanced composite gels formed by compression molding and injection molding, and gives it a large degree of molding freedom and high molding precision in additive manufacturing.

[0021] (2) The process steps of the present invention are convenient, the materials are easy to form, and the strain rate enhanced gel structure can be freely designed and precisely printed, giving full play to the synergistic effect of the matrix strain rate enhancement characteristics and the structural impact resistance characteristics, and can be widely used in the field of impact protection. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the mixing of the shear-hardening gel ethanol solution and the polyvinyl alcohol aqueous solution of the present invention;

[0023] Figure 2 This is a schematic diagram illustrating the preparation of the composite gel precursor of the present invention;

[0024] Figure 3This is a schematic diagram of the printing of the composite gel precursor of the present invention;

[0025] In the diagram, 1 is a three-necked flask, 2 is a stirring rod, 3 is an oil bath, 4 is oil for the oil bath, 5 is a polyvinyl alcohol aqueous solution, 6 is a shear-hardening gel ethanol solution, 7 is a ball mill jar, 8 is a ball mill, 9 is chitosan, 10 is a blend of shear-hardening gel and polyvinyl alcohol solution, 11 is a pneumatic extruder control system, 12 is a barrel, 13 is an air duct, 14 is an air compressor, and 15 is a composite gel precursor.

[0026] Figure 4 Viscosity-shear rate curves of composite gel precursors with different ratios according to the present invention;

[0027] Figure 5 The viscosity-shear rate curve of the shear-hardening gel of the present invention is shown.

[0028] Figure 6 The damping factor-shear stress curves of composite gel precursors with different ratios according to the present invention are shown.

[0029] Figure 7 The damping factor-shear stress curve of the shear-hardening gel of the present invention;

[0030] Figure 8 The elastic modulus-shear frequency curves of the composite gels with different ratios of the present invention are shown.

[0031] Figure 9 This is the elastic modulus-shear frequency curve of the shear-hardening gel of the present invention. Detailed Implementation

[0032] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0033] A. The specific methods for steady-state shear testing of composite gel precursors with different ratios are as follows: Figure 4 , Figure 5 )

[0034] The composite gel precursor was molded into cylinders with a diameter of 20 mm and a thickness of 1 mm, and tested using a commercial rotational rheometer (Physica MCR 302, Anton Paar Co., Austria) in steady-state shear mode at a shear rate of 10. -2 ~10 2 / second. Furthermore, the shear rate in Example 5 was 10... -3 ~10 0 / Second.

[0035] B. The specific methods for the oscillation shear test of composite gel precursors with different ratios are as follows: Figure 6 , Figure 7 )

[0036] The composite gel precursor was molded into cylinders with a diameter of 20 mm and a thickness of 1 mm. Testing was conducted using a commercial rotational rheometer (Physica MCR 302, Anton Paar Co., Austria) in oscillatory shear mode at a shear frequency of 1 Hz and a shear stress of 10 Ω. -1 ~10 4 Pa, the shear stress in Example 5 is 10 Pa. 1 ~10 5 Pa.

[0037] C. The specific methods for the oscillation shear test of composite gels with different ratios are as follows: Figure 8 , Figure 9 )

[0038] The composite gel precursor was molded into cylinders with a diameter of 20 mm and a thickness of 1 mm. Testing was performed using a commercial rotational rheometer (Physica MCR 302, Anton Paar Co., Austria) in oscillatory shear mode with a shear strain of 0.1% and a shear frequency of 10 Hz. -1 ~10 1 Hertz, the shear frequency of Example 5 is 10 Hz. -1 ~10 2 hertz.

[0039] like Figure 1 As shown, the shear-hardened gel ethanol solution 6 was added to the polyvinyl alcohol aqueous solution 5 and placed in a three-necked flask 1. Under 90°C oil bath conditions, the mixture was stirred at 400 rpm until homogeneous. The three-necked flask 1 was placed in an oil bath 3 containing oil 4 for the oil bath. A stirring rod 2 was installed inside the three-necked flask 1. Figure 2 As shown, the premixed shear-hardening gel and polyvinyl alcohol solution blend 10 was transferred to a ball mill jar 7 containing a ball mill 8, and then chitosan 9 was added. The mixture was mechanically ball-milled at a frequency of 20 Hz for 48 hours to obtain a homogeneous composite gel precursor.

[0040] like Figure 3 As shown, the composite gel precursor 15 is added to the barrel 12 of a pneumatic extruder. The barrel is connected to an air compressor 14 via an air guide pipe 13. When the air compressor is running, the precursor is extruded through the nozzle at the end of the pneumatic extruder under air pressure. The extrusion air pressure can be adjusted by the air compressor, and the printing speed can be adjusted in real time by the pneumatic extruder control system 11. An automatic computer-aided design software is used to establish the printing model and slicing pattern, and control the nozzle movement path, thereby achieving the deposition of arbitrary two-dimensional patterns and the accumulation of three-dimensional structures.

[0041] like Figure 4 , 5As shown, Examples 1-4 exhibit shear-thinning characteristics in steady-state shear tests, meaning the viscosity of the system decreases with increasing shear rate, which is beneficial for smooth extrusion of the wire under external air pressure. In Example 5, the viscosity remains relatively stable at low shear rates but decreases rapidly at high shear rates, which is detrimental to smooth wire extrusion and can easily lead to non-extrusion or uneven wire distribution. Therefore, it is not suitable for the additive manufacturing method proposed in this invention.

[0042] like Figure 6 , 7 As shown, Examples 1-5 exhibited yielding behavior in the oscillating shear test; that is, when the shear stress was below a certain critical value, the damping factor remained stable, but above this critical value, the damping factor increased rapidly. Examples 1-4 at 10 0 The damping factors under shear stresses of 1.00, 0.84, 0.82, and 0.62 were respectively. The damping factor before yielding was no higher than 1, indicating that the elastic characteristics of the system were dominant, which was beneficial for suppressing the mutual fusion of extruded wires and ensuring on-demand molding. Example 5 at 10... 2 The damping factor under shear stress is 1.02, and the damping factor before yielding is higher than 1, indicating that the viscous characteristics of the system are dominant and the extruded wires tend to merge with each other. Therefore, it is not suitable for the additive manufacturing method proposed in this invention.

[0043] like Figure 8 , 9 As shown, Examples 1-3 and Example 5 exhibited a strain rate enhancement effect in the oscillating shear test, that is, the elastic modulus increased with the increase of the shear frequency. Examples 1-3 showed a strain rate enhancement effect at 10 Hz. -1 ~10 1 The increases in elastic modulus at Hertzian shear frequencies were 5.16, 10.13, and 12.64 kPa, respectively. Example 5 showed an increase in elastic modulus at 10... -1 and 10 2 The increase in elastic modulus at the Hertz shear frequency is 283.00 kPa. Example 4 exhibits virtually no strain rate enhancement effect in the oscillating shear test at 10... -1 ~10 1 The increase in elastic modulus at the Hertz shear frequency is 0.73 kPa, therefore it is not applicable to the additive manufacturing method proposed in this invention.

[0044] Example 1

[0045] Preparation of shear-hardening gel: The raw materials used were silicone oil (Dow Corning linear silicone oil PMX-0156, molecular weight ~4000), boric acid, and n-octanoic acid. The ratio of silicone oil, boric acid, and n-octanoic acid was 20 g: 1 g: 25 μL. After the silicone oil and boric acid were mixed evenly, they were placed in an oven at 160°C for high-temperature polymerization for 2 hours. After the silicone oil solidified, n-octanoic acid was added, and heating was continued for 15 minutes. The mixture was then removed and allowed to cool naturally to room temperature to obtain the shear-hardening gel.

[0046] Preparation of the composite gel precursor: First, the shear-hardening gel was dispersed in ethanol by ultrasonic treatment at 53 kHz to obtain a shear-hardening gel ethanol solution 6 with a concentration of 0.5 g / mL. Then, polyvinyl alcohol (polyvinyl alcohol 1750±50, degree of polymerization 1700, degree of alcoholysis 50% from Sinopharm Chemical Reagent Co., Ltd.) was dissolved in deionized water under a stirring speed of 400 rpm in a 90°C oil bath to obtain a 6% (w / w) polyvinyl alcohol aqueous solution 5. Subsequently, 20 mL of the shear-hardening gel ethanol solution 6 was added to 100 g of the polyvinyl alcohol aqueous solution 5, and stirred at 400 rpm in a 90°C oil bath to ensure uniform mixing. Finally, the premixed shear-hardening gel and polyvinyl alcohol solution blend 10 was transferred to a ball mill jar 7, and then 12 g of chitosan 9 was added. The mixture was mechanically ball-milled at a frequency of 20 Hz for 48 hours to obtain a homogeneous composite gel precursor.

[0047] Additive fabrication of composite gel precursor: The composite gel precursor 15 is added to the barrel 12 of a pneumatic extruder. The barrel is connected to an air compressor 14 via an air guide pipe 13. When the air compressor is running, the precursor is extruded through the nozzle at the end of the pneumatic extruder under air pressure. The extrusion pressure is 0.1 MPa, and the printing speed is 3 mm / s. The extrusion pressure can be adjusted by the air compressor, and the printing speed can be adjusted in real time by the pneumatic extruder control system 11. An automated computer-aided design software is used to establish the printing model and slicing pattern, controlling the nozzle movement path to achieve the deposition of arbitrary two-dimensional patterns and the stacking of three-dimensional structures. Finally, the printed composite gel precursor is transferred to a -20°C freezer for 12 hours, then removed and thawed at room temperature for 4 hours to obtain a composite gel with strain rate enhancement effect.

[0048] The prepared composite gel precursor exhibited shear-thinning properties in steady-state shear tests, meaning that the viscosity of the system decreased with increasing shear rate, especially at 10... -2 and 10 2 The viscosities at shear rates of 10 / second were 2.34 and 0.02 kPa·s, respectively; in the oscillating shear test, it exhibited yielding behavior, meaning that the damping factor increased rapidly after the shear stress exceeded the critical value, reaching a value of 10. 0 and 10 3 The damping factors under Pascal shear stress were 1.00 and 1.15, respectively; the prepared composite gel exhibited a strain rate enhancement effect at 10 Pascals. -1 and 10 1 The elastic moduli at Hertz shear frequencies are 2.16 and 7.32 kPa, respectively.

[0049] Example 2

[0050] Preparation of shear-hardening gel: The raw materials used were silicone oil (Dow Corning linear silicone oil PMX-0156, molecular weight ~4000), boric acid, and n-octanoic acid. The ratio of silicone oil, boric acid, and n-octanoic acid was 20 g: 1 g: 25 μL. After the silicone oil and boric acid were mixed evenly, they were placed in an oven at 160°C for high-temperature polymerization for 2 hours. After the silicone oil solidified, n-octanoic acid was added, and heating was continued for 15 minutes. The mixture was then removed and allowed to cool naturally to room temperature to obtain the shear-hardening gel.

[0051] Preparation of the composite gel precursor: First, the shear-hardening gel was dispersed in ethanol by ultrasonic treatment at 53 kHz to obtain a shear-hardening gel ethanol solution 6 with a concentration of 0.5 g / mL. Then, polyvinyl alcohol (polyvinyl alcohol 1750±50, degree of polymerization 1700, degree of alcoholysis 50% from Sinopharm Chemical Reagent Co., Ltd.) was dissolved in deionized water under a stirring speed of 400 rpm in a 90°C oil bath to obtain a 10% (w / w) polyvinyl alcohol aqueous solution 5. Subsequently, 20 mL of the shear-hardening gel ethanol solution 6 was added to 100 g of the polyvinyl alcohol aqueous solution 5, and stirred at 400 rpm in a 90°C oil bath to ensure uniform mixing. Finally, the premixed shear-hardening gel and polyvinyl alcohol solution blend 10 was transferred to a ball mill jar 7, and then 12 g of chitosan 9 was added. The mixture was mechanically ball-milled at a frequency of 20 Hz for 48 hours to obtain a homogeneous composite gel precursor.

[0052] Additive fabrication of composite gel precursor: The composite gel precursor 15 is added to the barrel 12 of a pneumatic extruder. The barrel is connected to an air compressor 14 via an air guide pipe 13. When the air compressor is running, the precursor is extruded through the nozzle at the end of the pneumatic extruder under air pressure. The extrusion pressure is 0.1 MPa, and the printing speed is 3 mm / s. The extrusion pressure can be adjusted by the air compressor, and the printing speed can be adjusted in real time by the pneumatic extruder control system 11. An automated computer-aided design software is used to establish the printing model and slicing pattern, controlling the nozzle movement path to achieve the deposition of arbitrary two-dimensional patterns and the stacking of three-dimensional structures. Finally, the printed composite gel precursor is transferred to a -20°C freezer for 12 hours, then removed and thawed at room temperature for 4 hours to obtain a composite gel with strain rate enhancement effect.

[0053] The prepared composite gel precursor exhibited shear-thinning properties in steady-state shear tests, with a shear-thinning effect at 10... -2 and 10 2 The viscosities at shear rates of 10 / second were 9.55 and 0.01 kPa·s, respectively; they exhibited yielding behavior in oscillating shear tests, and at 10 0 and 10 3 The damping factors under Pascal shear stress were 0.84 and 0.89, respectively; the prepared composite gel exhibited a strain rate enhancement effect at 10 Pascals. -1 and 101 The elastic moduli at the Hertz shear frequency are 8.82 and 18.95 kPa, respectively.

[0054] Example 3

[0055] Preparation of shear-hardening gel: The raw materials used were silicone oil (Dow Corning linear silicone oil PMX-0156, molecular weight ~4000), boric acid, and n-octanoic acid. The ratio of silicone oil, boric acid, and n-octanoic acid was 20 g: 1 g: 25 μL. After the silicone oil and boric acid were mixed evenly, they were placed in an oven at 160°C for high-temperature polymerization for 2 hours. After the silicone oil solidified, n-octanoic acid was added, and heating was continued for 15 minutes. The mixture was then removed and allowed to cool naturally to room temperature to obtain the shear-hardening gel.

[0056] Preparation of the composite gel precursor: First, the shear-hardening gel was dispersed in ethanol by ultrasonic treatment at 53 kHz to obtain a shear-hardening gel ethanol solution 6 with a concentration of 0.5 g / mL. Then, polyvinyl alcohol (polyvinyl alcohol 1750±50, degree of polymerization 1700, degree of alcoholysis 50% from Sinopharm Chemical Reagent Co., Ltd.) was dissolved in deionized water under a stirring speed of 400 rpm in a 90°C oil bath to obtain a 14% (w / w) polyvinyl alcohol aqueous solution 5. Subsequently, 20 mL of the shear-hardening gel ethanol solution 6 was added to 100 g of the polyvinyl alcohol aqueous solution 5, and stirred at 400 rpm in a 90°C oil bath to ensure uniform mixing. Finally, the premixed shear-hardening gel and polyvinyl alcohol solution blend 10 was transferred to a ball mill jar 7, and then 12 g of chitosan 9 was added. The mixture was mechanically ball-milled at a frequency of 20 Hz for 48 hours to obtain a homogeneous composite gel precursor.

[0057] Additive fabrication of composite gel precursor: The composite gel precursor 15 is added to the barrel 12 of a pneumatic extruder. The barrel is connected to an air compressor 14 via an air guide pipe 13. When the air compressor is running, the precursor is extruded through the nozzle at the end of the pneumatic extruder under air pressure. The extrusion pressure is 0.3 MPa, and the printing speed is 30 mm / s. The extrusion pressure can be adjusted by the air compressor, and the printing speed can be adjusted in real time by the pneumatic extruder control system 11. An automated computer-aided design software is used to establish the printing model and slicing pattern, controlling the nozzle movement path to achieve the deposition of arbitrary two-dimensional patterns and the stacking of three-dimensional structures. Finally, the printed composite gel precursor is transferred to a -20°C freezer for 12 hours, then removed and thawed at room temperature for 4 hours to obtain a composite gel with strain rate enhancement effect.

[0058] The prepared composite gel precursor exhibited shear-thinning properties in steady-state shear tests, with a shear-thinning effect at 10... -2 and 10 2The viscosities at shear rates of 10 / second were 23.96 and 0.02 kPa·s, respectively; it exhibited yielding behavior in oscillating shear tests, and at 10 0 and 10 3 The damping factors under shear stress were 0.82 and 0.86, respectively; the prepared composite gel exhibited a strain rate enhancement effect at 10... -1 and 10 1 The elastic moduli at the Hertz shear frequency are 20.05 and 32.69 kPa, respectively.

[0059] Example 4

[0060] Preparation of the composite gel precursor: First, polyvinyl alcohol (polyvinyl alcohol 1750±50, degree of polymerization 1700, degree of alcoholysis 50% from Sinopharm Chemical Reagent Co., Ltd.) was dissolved in deionized water under a stirring speed of 400 rpm in a 90°C oil bath to obtain a 14% (w / w) polyvinyl alcohol aqueous solution 5. Then, 100 g of polyvinyl alcohol solution 5 was transferred to a ball mill jar 7, and 12 g of chitosan 9 was added. The mixture was mechanically ball-milled at a frequency of 20 Hz for 48 hours to obtain a homogeneous composite gel precursor.

[0061] Additive fabrication of composite gel precursor: The composite gel precursor 15 is added to the barrel 12 of a pneumatic extruder. The barrel is connected to an air compressor 14 via an air guide pipe 13. When the air compressor is running, the precursor is extruded through the nozzle at the end of the pneumatic extruder under air pressure. The extrusion pressure is 0.3 MPa, and the printing speed is 30 mm / s. The extrusion pressure can be adjusted by the air compressor, and the printing speed can be adjusted in real time by the pneumatic extruder control system 11. An automated computer-aided design software is used to establish the printing model and slicing pattern, controlling the nozzle movement path to achieve the deposition of arbitrary two-dimensional patterns and the stacking of three-dimensional structures. Finally, the printed composite gel precursor is transferred to a -20°C freezer for 12 hours, then removed and thawed at room temperature for 4 hours to obtain a composite gel with strain rate enhancement effect.

[0062] The prepared composite gel precursor exhibited shear-thinning properties in steady-state shear tests, with a shear-thinning effect at 10... -2 and 10 2 The viscosities at shear rates of 6.27 kPa·s and 0.01 kPa·s were respectively; it exhibited yielding behavior in oscillating shear tests, and at 10 0 and 10 3 The damping factors under shear stress were 0.62 and 0.94, respectively; the prepared composite gels basically did not exhibit strain rate enhancement effects at 10... -1 and 10 1 The elastic moduli at the Hertz shear frequency are 3.87 and 4.60 kPa, respectively.

[0063] Example 5

[0064] Preparation of shear-hardening gel: The raw materials used were silicone oil (Dow Corning linear silicone oil PMX-0156, molecular weight ~4000), boric acid, and n-octanoic acid. The ratio of silicone oil, boric acid, and n-octanoic acid was 20 g: 1 g: 25 μL. After the silicone oil and boric acid were mixed evenly, they were placed in an oven at 160°C for high-temperature polymerization for 2 hours. After the silicone oil solidified, n-octanoic acid was added, and heating was continued for 15 minutes. The mixture was then removed and allowed to cool naturally to room temperature to obtain the shear-hardening gel.

[0065] The prepared shear-hardening gel exhibited relatively stable viscosity at low shear rates during steady-state shear tests, but its viscosity decreased rapidly at higher shear rates. At 10... -3 and 10 0 The viscosities at shear rates of 10 / second were 36.13 and 29.60 kPa·s, respectively, which is unfavorable for pneumatic extrusion; it exhibited yielding behavior in oscillating shear tests, and at 10 2 and 6×10 5 The damping factors under Pascal shear stress were 1.02 and 1.09, respectively, and their damping factors were always greater than 1, indicating that the behavior was mainly viscous. Therefore, the extruded wires would fuse together, making them unsuitable for the additive manufacturing method proposed in this invention. The prepared composite gel exhibited a significant strain rate enhancement effect at 10 Pascal shear stress. -1 and 10 2 The elastic moduli at the Hertz shear frequency are 2.95 and 285.95 kPa, respectively.

[0066] The preferred embodiments of the present invention have been described in detail above. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention. Those skilled in the art should understand that modifications and equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention should be included within the scope of the claims of the present invention.

Claims

1. An additive manufacturing method for a strain rate-enhanced composite gel, characterized in that: The method includes the following steps: (1) Silicone oil, boric acid and octanoic acid are polymerized at high temperature to prepare a shear-hardening gel; (2) The shear-hardening gel prepared in step (1) is introduced into a polyvinyl alcohol aqueous solution and chitosan particles are added. The mixture is then ball-milled to obtain a composite gel precursor. (3) The composite gel precursor prepared in step (2) is printed by pneumatic extrusion combined with a triaxial motion control system, and then the elastomer is obtained by freeze-thaw treatment.

2. The additive manufacturing method for a strain rate-enhanced composite gel according to claim 1, characterized in that: In step (1), the raw material ratio is silicone oil: boric acid: octanoic acid = 10~40 g: 0.5~2 g: 25 μL; the high-temperature polymerization reaction temperature is 140~200 degrees Celsius.

3. The additive manufacturing method for a strain rate-enhanced composite gel according to claim 1, characterized in that: In step (2), the specific preparation steps of the composite gel precursor are as follows: uniformly disperse the shear-hardening gel in ethanol to obtain a shear-hardening gel ethanol solution; dissolve polyvinyl alcohol in deionized water to obtain a polyvinyl alcohol aqueous solution; uniformly mix the shear-hardening gel ethanol solution and the polyvinyl alcohol aqueous solution to obtain a mixed system; add chitosan to the aforementioned mixed system and obtain a homogeneous composite gel precursor by mechanical ball milling.

4. The additive manufacturing method for a strain rate-enhanced composite gel according to claim 3, characterized in that: In step (2), the concentration of shear-hardening gel in the shear-hardening gel ethanol solution is 0.2~0.6 g / mL; the mass fraction of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 6~18%; the mass ratio of chitosan to polyvinyl alcohol aqueous solution is 8~14:100; and the ratio of shear-hardening gel ethanol solution to polyvinyl alcohol aqueous solution is 10~30 mL:100 g.

5. The additive manufacturing method for a strain rate-enhanced composite gel according to claim 1, characterized in that: In step (3), the printing principle is direct ink writing 3D printing process. The pneumatic extruder control system controls the three-axis movement of the nozzle through automatic computer-aided design software. The extrusion air pressure is 0.1~0.5 MPa and the printing speed is 3~50 mm / s.

6. The additive manufacturing method for a strain rate-enhanced composite gel according to claim 1, characterized in that: In step (3), the specific operation steps of the freeze-thaw treatment are as follows: transfer the printed composite gel precursor to a freezer at -20 to -18 degrees Celsius, freeze it, take it out, and then thaw it at room temperature.

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