A bistable flexible energy-absorbing protection structure and preparation method thereof

Abstract

A bistable flexible energy-absorbing protective structure and preparation method thereof include two upper and lower rigid horizontal layers, with a flexible intermediate layer disposed between the rigid horizontal layers, the flexible intermediate layer including a trapezoidal self-locking structure, and flexible elastic rods connected between the trapezoidal self-locking structures that are spaced opposite to each other. The preparation steps are as follows: printing the two upper and lower rigid horizontal layers using a resin material using a 3D printer; preparing an intermediate layer female mold consistent with the flexible intermediate layer composed of the flexible elastic rods and the trapezoidal self-locking structure using an acrylic plate, pouring a silicone rubber mixture into the female mold for curing and forming; and finally bonding the rigid horizontal layer to the cured flexible intermediate layer. The present invention has a simple and reliable structure, is easy to prepare, and can achieve good low-speed impact protection.

Description

Technical Field

[0001] The present invention relates to the technical field of energy-absorbing structures, and in particular to a bistable flexible energy-absorbing protective structure and a preparation method thereof. Background Art

[0002] Energy-absorbing structures have been widely used in precision device protection, vibration isolation, and anti-collision structures. When impacted, energy-absorbing structures can effectively reduce the external load on the protected object, cushioning and reducing vibration to achieve a protective effect. Traditional energy-absorbing structures are generally made of materials such as metal and ceramics. As the metal plastically deforms and the ceramics fracture, the structure is destroyed while absorbing energy, making it only usable as a single-time energy-absorbing material. To solve this problem, researchers have designed various flexible and reusable energy-absorbing structures using soft materials, such as negative stiffness honeycombs and corrugated structures. These structures immediately return to their original state after the external load is removed. This phenomenon is called monostability. However, this deformation recovery effect is very likely to cause secondary damage to the protected object. Therefore, the ideal energy-absorbing structure is bistable, that is, it can maintain its deformed state when the external load is removed.

[0003] Later, researchers designed energy-absorbing structures based on rod instability. Studies have shown that when elastic rods buckle under compression, they undergo a buckling step, manifesting as a decrease in the applied force as the load increases. If the applied force is constant pressure, the rod will deform and recover after unloading, making the rod structure monostable. If a tension segment occurs during loading, the rod can maintain its deformed state after unloading, a phenomenon known as bistability. However, for bistable rod structures, the presence of a tension segment during deformation is detrimental to energy absorption. To improve energy absorption, a common approach is to increase the rod's bearing capacity. However, rods with greater bearing capacity are less likely to trigger the bistability effect. Therefore, minimizing the tension segment, without changing the rod's bearing capacity, is an effective way to improve the rod's energy absorption efficiency.

[0004] There are currently two problems with bistable energy-absorbing structures based on rod instability: (1) The existing bistable inclined straight rod energy-absorbing structures have low energy absorption efficiency. Improving the structural energy absorption efficiency mainly involves increasing the bearing capacity by changing the geometric dimensions of the rods, but the geometric dimensions of the rods with a bistable effect are limited, that is, the bearing capacity of the rods with a bistable effect is not high. (2) The supporting structure of the rods does not participate in the energy absorption process, resulting in low mass utilization of the system. For example, patent CN106828381B designs an anti-collision beam based on a bistable unit cell structure, but the bearing capacity of its bistable unit cell rod is low when under compression; patent CN113757290B provides an energy-absorbing superstructure composed of a right-angled triangle buckling structure and a four-pointed star support structure, but the geometric dimensions of the bistable rod are limited, and the support structure does not participate in the deformation process; patent CN115238407A manufactures a foldable, variable-stiffness multi-layer energy-absorbing structure composed of oblique rods, but the energy absorption efficiency of the single-layer bistable structure is low; patent CN217463020U designs a bistable energy-absorbing device composed of a support beam, a conical shell and a cylindrical ring that can resist three-way buffering, but its unit cell structure has a complex geometric shape and a cumbersome preparation process. Summary of the Invention

[0005] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a bistable flexible energy-absorbing protection structure and a preparation method. The energy-absorbing protection structure consists of an elastic rod and a trapezoidal self-locking structure to form an energy absorption system, and a preparation method is proposed, which realizes the improvement of the structural energy absorption efficiency without changing the bearing capacity of the rod. It has a simple and reliable structure, is easy to prepare, and can achieve better low-speed impact protection function.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] A bistable flexible energy-absorbing protective structure includes two upper and lower hard horizontal layers 1, a flexible middle layer is arranged between the hard horizontal layers 1, and the flexible middle layer includes a trapezoidal self-locking structure 2. Flexible elastic rods 3 are connected between the trapezoidal self-locking structures 2 that are spaced opposite to each other.

[0008] The hard horizontal layer 1 is made of 3D printed resin material and is a rectangular horizontal plate.

[0009] The trapezoidal self-locking structure 2 is an isosceles trapezoid, the inclination angle α between the hypotenuse and the horizontal plane is 80°-85°, and the chamfer r is 0.3-0.4 mm, preferably 0.375 mm.

[0010] The inclination angle θ of the flexible elastic rod 3 to the horizontal plane is 55°-65°, and the rod slenderness ratio (width / length) is 0.15-0.2. Preferably, the inclination angle θ is 60° and the slenderness ratio is 0.2.

[0011] A method for preparing a bistable flexible energy-absorbing protective structure, characterized by comprising the following steps:

[0012] Step 1: Print two hard horizontal layers using the resin material VeroPureWhite using a 3D printer;

[0013] Step 2: Using an acrylic plate, prepare an intermediate layer female mold that is consistent with the flexible intermediate layer composed of the flexible elastic rod 3 and the trapezoidal self-locking structure 2, and pour the silicone rubber mixture into the female mold for curing and forming; the trapezoidal self-locking structure 2 is an isosceles trapezoid with an inclination angle α of 80°-85° and a chamfer r of 0.3-0.4 mm, preferably 0.375 mm; the flexible elastic rod 3 has an inclination angle θ of 55-65° and a slenderness ratio of 0.15-0.2, preferably an inclination angle θ of 60° and a slenderness ratio of 0.2;

[0014] Step 3: Bond the hard horizontal layer 1 and the cured flexible middle layer.

[0015] Compared with the prior art, the present invention has the following creative features:

[0016] (1) By designing a trapezoidal self-locking structure 2, the flexible elastic rod 3 and the trapezoidal self-locking structure 2 are combined so that the two are squeezed and deformed when subjected to low-speed impact, thereby solving the problem of low mass utilization of the bistable energy-absorbing protective structure.

[0017] (2) The friction self-locking force introduced by the trapezoidal self-locking structure 2 limits the deformation recovery of the energy absorption protection structure. Compared with the existing inclined straight rod energy absorption structure of the same size, the energy absorption efficiency of the structure is significantly improved.

[0018] (3) The present invention has a simple and reliable structure and is easy to prepare. It designs a new type of bistable flexible energy-absorbing structure, which can achieve better low-speed anti-impact protection function. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of the hard horizontal layer 1.

[0020] Figure 2 It is a structural schematic diagram of the flexible elastic rod 3 and the trapezoidal self-locking structure 2.

[0021] Figure 3 It is a negative mold diagram of the middle layer composed of a flexible elastic rod 3 and a trapezoidal self-locking structure 2.

[0022] Figure 4 Schematic diagram of the bistable energy-absorbing protection structure before and after overall deformation. DETAILED DESCRIPTION

[0023] The present invention aims to propose a high-efficiency bistable energy-absorbing protective structure and a preparation method thereof, so as to achieve the purpose of improving the structural energy absorption efficiency and mass utilization rate, and provide a new solution for the production and manufacturing of bistable energy-absorbing protective structures. The present invention is further described in detail with reference to the accompanying drawings and specific examples.

[0024] Reference Figure 3 A bistable flexible energy-absorbing protective structure comprises an upper and a lower hard horizontal layer 1, wherein the hard horizontal layer 1 is used to prevent the torsion and shear deformation of the structure. A flexible intermediate layer is provided between the hard horizontal layers 1, and the flexible intermediate layer serves as an energy-absorbing structure when subjected to low-speed impact. The flexible intermediate layer is prepared into an integral structure by the reverse molding method. Figure 2 The flexible intermediate layer includes a trapezoidal self-locking structure 2, and flexible elastic rods 3 are connected between the trapezoidal self-locking structures 2 that are spaced apart from each other. Each flexible intermediate layer has 10 flexible elastic rods 3 and 11 trapezoidal self-locking structures 2, all of which are made of silicone rubber.

[0025] Reference Figure 1 , the hard horizontal layer 1 is made of 3D printed resin material and is a rectangular horizontal plate with a length of 50 mm, a width of 3 mm, and a thickness of 15 mm;

[0026] The trapezoidal self-locking structure 2 is an isosceles trapezoid with a height h of 3.5 mm, a long side width w of 3-3.3 mm, an inclination angle α of 80°-85°, and a chamfer r of 0.3-0.4 mm, preferably 0.375 mm;

[0027] The inclination angle θ of the flexible elastic rod 3 to the horizontal plane is 55°-65°, preferably 60. The length L is 5 mm, and the width t is 0.75-1 mm, preferably 1 mm, that is, the slenderness ratio is 0.15-0.2, preferably 0.2.

[0028] A method for preparing a bistable flexible energy-absorbing protective structure, characterized by comprising the following steps:

[0029] Step 1: Print two hard horizontal layers using the 3D printer Object 350Connex3TM using the resin material VeroPureWhite.

[0030] Step 2: Use an acrylic plate to prepare an intermediate layer female mold that is consistent with the flexible intermediate layer composed of the flexible elastic rod 3 and the trapezoidal self-locking structure 2, and pour the silicone rubber mixture into the female mold to solidify and shape it;

[0031] The silicone rubber mixture is a commercial Ecoflex 00-30 product. Ecoflex 00-30 is divided into two parts, Part A and Part B. Part A and Part B are mixed in a mass ratio of 1:1, and the mixture is placed in a high-speed blender and stirred for 2 minutes.

[0032] Use a vacuum pump to remove air bubbles from the mixture for 8 minutes. Pour the mixture into the middle layer mold and place it in a 60°C oven for 4 hours to cure.

[0033] The trapezoidal self-locking structure 2 is an isosceles trapezoid with a height h of 3.5 mm, a long side width w of 3-3.3 mm, an inclination angle α of 80°-85°, and a chamfer r of 0.3-0.4 mm, preferably 0.375 mm;

[0034] The inclination angle θ of the flexible elastic rod 3 to the horizontal plane is 55°-65°, preferably 60°; the length L is 5 mm, and the width t is 0.75-1 mm, preferably 1 mm, that is, the slenderness ratio is 0.15-0.2, preferably 0.2.

[0035] Step 3: Bond the hard horizontal layer 1 and the cured flexible middle layer.

[0036] Example 1

[0037] The preparation steps of this embodiment are:

[0038] Prepare upper and lower hard horizontal layers by 3D printing;

[0039] An acrylic sheet was used to prepare a female mold for the intermediate layer, which was consistent with the flexible intermediate layer composed of the flexible elastic rod and the trapezoidal self-locking structure. The flexible elastic rod had an inclination angle θ of 60°, a length L of 5 mm, and a width t of 1 mm, i.e., a slenderness ratio of 0.2. The trapezoidal self-locking structure was an isosceles trapezoid with a height h of 3.5 mm, a long side width w of 3.3 mm, an inclination angle α of 80°, and a chamfer r of 0.375 mm.

[0040] Mix Part A and Part B of Ecoflex 00-30 in a mass ratio of 1:1, stir the mixture at high speed for 2 minutes, and extract bubbles for 8 minutes. Then pour it into the middle layer mold and cure it for 4 hours to form the mold.

[0041] Bond the upper and lower rigid horizontal layers to the cured flexible middle layer.

[0042] Example 2

[0043] The preparation steps of this embodiment are:

[0044] Prepare upper and lower hard horizontal layers by 3D printing;

[0045] An acrylic sheet was used to prepare a female mold for the intermediate layer, which was consistent with the flexible intermediate layer composed of the flexible elastic rod and the trapezoidal self-locking structure. The flexible elastic rod had an inclination angle θ of 55°, a length L of 5 mm, and a width t of 0.875 mm, i.e., a slenderness ratio of 0.175. The trapezoidal self-locking structure was an isosceles trapezoid with a height h of 3.5 mm, a long side width w of 3.15 mm, an inclination angle α of 82.5°, and a chamfer r of 0.375 mm.

[0046] Mix Part A and Part B of Ecoflex 00-30 in a mass ratio of 1:1, stir the mixture at high speed for 2 minutes, and extract bubbles for 8 minutes. Then pour it into the middle layer mold and cure it for 4 hours to form the mold.

[0047] Bond the upper and lower rigid horizontal layers to the cured flexible middle layer.

[0048] Example 3

[0049] The preparation steps of this embodiment are:

[0050] Prepare upper and lower hard horizontal layers by 3D printing;

[0051] An acrylic sheet was used to prepare a female mold for the intermediate layer, which was consistent with the flexible intermediate layer composed of the flexible elastic rod and the trapezoidal self-locking structure. The flexible elastic rod had an inclination angle θ of 65°, a length L of 5 mm, and a width t of 0.75 mm, i.e., a slenderness ratio of 0.15. The trapezoidal self-locking structure was an isosceles trapezoid with a height h of 3.5 mm, a long side width w of 3 mm, an inclination angle α of 85°, and a chamfer r of 0.375 mm.

[0052] Mix Part A and Part B of Ecoflex 00-30 in a mass ratio of 1:1, stir the mixture at high speed for 2 minutes, and extract bubbles for 8 minutes. Then pour it into the middle layer mold and cure it for 4 hours to form the mold.

[0053] Bond the upper and lower rigid horizontal layers to the cured flexible middle layer.

[0054] The above three embodiments select different values, all of which can realize the production and manufacturing of the bistable energy absorbing protection structure, and both the flexible elastic rod 3 and the trapezoidal self-locking structure 2 are squeezed and deformed when subjected to low-speed impact, solving the problem of low mass utilization of the bistable energy absorbing protection structure.

[0055] Energy absorption principle of the present invention:

[0056] Reference Figure 4The present invention designs a trapezoidal self-locking structure. In the process where the flexible elastic rod 3 and the trapezoidal self-locking structure 2 contact each other and the flexible elastic rod 3 is pressed into the self-locking structure 2, the stress level is improved. At the same time, the friction between the two dissipates a large amount of energy, thereby improving the energy absorption efficiency of the system. By utilizing the mechanism that both the flexible elastic rod 3 and the trapezoidal self-locking structure 2 participate in the deformation during the compression process, the mass utilization rate of the system is improved. When the external load is removed, the friction between the flexible elastic rod 3 and the trapezoidal self-locking structure 2 can be regarded as a self-locking force, which plays a role in hindering the recovery of structural deformation. Compared with the general oblique straight rod bistable energy absorption structure, the energy absorption efficiency is significantly improved without changing the bearing capacity of the structure. The present invention has certain guiding significance for the design of bistable energy absorption protection structures.

[0057] The above content specifically describes a bistable flexible protective structure and a manufacturing method thereof described in the present invention, and lists multiple embodiments for illustration. However, the present invention is not limited to the specific implementation contents and corresponding embodiments described above. Therefore, any improvements, equivalent modifications and replacements based on the technical points of the present invention (such as the shape of the self-locking structure, etc.) are within the scope of protection of the present invention.

Claims

1. A bistable flexible energy-absorbing protective structure, characterized in that: It comprises two upper and lower hard horizontal layers (1), a flexible middle layer is arranged between the hard horizontal layers (1), the flexible middle layer comprises a trapezoidal self-locking structure (2), and a flexible elastic rod (3) is connected between the trapezoidal self-locking structures (2) that are spaced opposite to each other; Each flexible middle layer has 10 flexible elastic rods (3) and 11 trapezoidal self-locking structures (2), all made of silicone rubber; When subjected to external load impact, the flexible elastic rod (3) will come into contact with the adjacent self-locking structure (2) and eventually be squeezed into the gap between the self-locking structures (2). Based on the principle of mechanics, when unloading, the flexible elastic rod (3) and the self-locking structure (2) will deform and interlock; The trapezoidal self-locking structure (2) is an isosceles trapezoid, the inclination angle α between the hypotenuse and the horizontal plane is 80°-85°, and the chamfer r is 0.3-0.4 mm; The inclination angle θ of the flexible elastic rod (3) to the horizontal plane is 55°-65°, and the slenderness ratio is 0.15-0.

2.

2. A bistable flexible energy absorbing protective structure according to claim 1, characterized in that: The hard horizontal layer (1) is made of 3D-printed resin material and is a rectangular horizontal plate.

3. The bistable flexible energy absorbing protective structure according to claim 1, characterized in that: The chamfer r is 0.375mm.

4. The bistable flexible energy absorbing protective structure according to claim 1, characterized in that: The inclination angle θ is 60° and the slenderness ratio is 0.

2.

5. A method for preparing a bistable flexible energy-absorbing protective structure according to any one of claims 1 to 4, characterized in that: The production steps include: Step 1: Print two hard horizontal layers using the resin material VeroPureWhite using a 3D printer; Step 2: Using an acrylic plate to prepare an intermediate layer female mold that is consistent with the flexible intermediate layer composed of the flexible elastic rod (3) and the trapezoidal self-locking structure (2), pouring the silicone rubber mixture into the female mold for solidification and molding; the trapezoidal self-locking structure (2) is an isosceles trapezoid with an inclination angle α of 80°-85° and a chamfer angle r of 0.3-0.4 mm; Step 3: Bonding the hard horizontal layer (1) and the cured and formed flexible middle layer.

Images