Shock absorbers and energy absorption devices

Abstract

To improve an energy absorption character of a shock absorption body.SOLUTION: A shock absorption body is formed as a laminate of a first resin layer made of first resin, and a second resin layer made of second resin with a compression elastic ratio smaller than that of the first resin, and includes 3 or more interfaces between the first resin layer and the second resin layer. A difference in a compression elastic ratio between the first resin and the second resin is 20% or more of the compression elastic ratio of the second resin. When the shock absorption body is divided into three in a lamination direction of the first resin layer and the second resin layer, and designated as a first laminate part, a second laminate part and a third laminate part sequentially from one end side in the lamination direction, at least two laminate parts among three laminate parts from the first laminate part to the third laminate part have both of the first resin and the second resin, and the first laminate part and the third laminate part have different volume ratio of the first resin and the second resin.SELECTED DRAWING: Figure 1

Description

Technical Field

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[0001] The present disclosure relates to a shock absorber and an energy absorption device.

Background Art

[0002] Conventionally, resin members having various shapes have been proposed as shock absorbers for absorbing shock energy. For example, in Patent Document 1, as an energy absorption member composed of a composite material in which resin is reinforced with fibers, a plurality of layers having different elastic moduli are laminated along a direction orthogonal to the crushing direction, and one end portion in the crushing direction is inclined with respect to the pressing surface of a pressing member for crushing the member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the energy absorption member described in Patent Document 1 above, the initial characteristics when absorbing shock energy in the crushing direction are improved by the end structure and end shape of the member. However, in such a shock absorber that performs such energy absorption, not only the initial characteristics but also further improvement in the energy absorption characteristics of the entire shock absorber has been desired.

Means for Solving the Problems

[0005] The present disclosure can be realized in the following forms. (1) According to one embodiment of the present disclosure, an impact absorber is provided. The impact absorber is formed as a laminate of a first resin layer made of a first resin and a second resin layer made of a second resin having a lower compressive modulus than the first resin, and has three or more interfaces between the first resin layer and the second resin layer, the difference in compressive modulus between the first resin and the second resin is 20% or more of the magnitude of the compressive modulus of the second resin, and when the impact absorber is divided into three equal parts in the lamination direction of the first resin layer and the second resin layer, and in order from one end in the lamination direction, the first laminated part, the second laminated part and the third laminated part, at least two of the three laminated parts from the first laminated part to the third laminated part contain both the first resin and the second resin, and the volume ratio of the first resin and the second resin is different between the first laminated part and the third laminated part. This type of shock absorber can enhance the energy absorption capacity of the shock absorber and improve its performance by satisfying the following requirements: having at least three interfaces between the first resin layer and the second resin layer; the difference in compressive modulus between the first and second resins being 20% ​​or more of the compressive modulus of the second resin; having both the first and second resins in at least two of the three laminated sections from the first to the third laminated section; and having different volume ratios of the first and second resins in the first and third laminated sections. (2) In the impact absorber of the above form, each of the first resin and the second resin may contain 30% by mass or more of a common resin component. With such a configuration, the adhesion at the interface between adjacent first resin layers and second resin layers can be improved. (3) In the above-described form of impact absorber, the common resin component may be polyamide. With this configuration, polyamide is relatively resistant to brittle fracture and can withstand a relatively large load relative to the amount of deformation, so by using polyamide as the common resin component, it becomes easier to improve the overall performance of the impact absorber. (4) In the impact absorber of the above form, at least one of the first resin and the second resin may contain 5 parts by weight or more of modified elastomer when the total amount of other components other than the modified elastomer is 100 parts by weight. With such a configuration, it becomes easy to lower the compressive modulus of the first resin and the second resin and adjust it to a desired compressive modulus. (5) In the impact absorber of the above form, the volume ratio of the first resin in the second laminated portion may be the same as the volume ratio of the first resin in either the first laminated portion or the third laminated portion, or it may be a value between the volume ratio of the first resin in the first laminated portion and the volume ratio of the first resin in the third laminated portion. With such a configuration, the effect of increasing the energy absorption amount of the impact absorber can be enhanced. (6) According to another embodiment of the present disclosure, an energy absorption device is provided, comprising a plurality of shock absorbers as described in any one of (1) to (5). This type of energy absorption device can disperse and absorb impact energy, thereby increasing its impact absorption capacity. This disclosure can be implemented in various forms other than those described above, for example, in the form of a method for manufacturing an impact absorber or a method for absorbing energy using an impact absorber. [Brief explanation of the drawing]

[0006] [Figure 1] A schematic perspective view showing the structure of the shock absorber. [Figure 2] An explanatory diagram showing the load-displacement diagrams of the shock absorber, the first structure, and the second structure. [Figure 3] An explanatory diagram relating to the measurement of the compressive modulus of the first resin. [Figure 4] An explanatory diagram relating to the measurement of the compressive modulus of the second resin. [Figure 5] A schematic perspective view showing the structure of the shock absorber in sample S2. [Figure 6] A schematic perspective view showing the structure of the shock absorber in sample S3. [Figure 7]Perspective view schematically showing the structure of the shock absorber of Sample S4. [Figure 8] Perspective view schematically showing the structure of the shock absorber of Sample S5. [Figure 9] Perspective view schematically showing the structure of the shock absorber of Sample S6. [Figure 10] Perspective view schematically showing the structure of the shock absorber of Sample S7. [Figure 11] Perspective view schematically showing the structure of the shock absorber of Sample S8. [Figure 12A] Explanatory drawing showing the detailed structure of Samples S1 to S12. [Figure 12B] Explanatory drawing showing the detailed structure of Samples S1 to S12. [Figure 13] Explanatory drawing showing the work amount and breaking strain of Samples S1 to S8. [Figure 14] Explanatory drawing showing the result of the compression test conducted on Sample S1. [Figure 15] Explanatory drawing showing the result of the compression test conducted on Sample S2. [Figure 16] Explanatory drawing showing the result of the compression test conducted on Sample S3. [Figure 17] Explanatory drawing showing the result of the compression test conducted on Sample S4. [Figure 18] Explanatory drawing showing the result of the compression test conducted on Sample S5. [Figure 19] Explanatory drawing showing the result of the compression test conducted on Sample S6. [Figure 20] Explanatory drawing showing the result of the compression test conducted on Sample S7. [Figure 21] Explanatory drawing showing the result of the compression test conducted on Sample S8.

Modes for Carrying Out the Invention

[0007] FIG. 1 is a perspective view schematically showing an example of the configuration of a shock absorber 10 as an embodiment of the present disclosure. The shock absorber 10 of the present embodiment can be used as a shock absorber that receives shock energy and absorbs the shock energy by deforming in the direction of the shock energy. The shock absorber 10 of the present embodiment enhances the performance as a shock absorber by laminating two types of resin layers having specific properties in a specific arrangement.

[0008] The shock absorber 10 of the present embodiment is formed as a laminate of a first resin layer 21 made of a first resin and a second resin layer 22 made of a second resin, and has three or more interfaces between the first resin layer 21 and the second resin layer 22. That is, the shock absorber 10 includes a total of four or more first resin layers 21 and second resin layers 22, and includes two or more first resin layers 21 and two or more second resin layers 22, respectively. The second resin has a smaller compression elastic modulus than the first resin and is a softer resin than the first resin. In the present embodiment, the difference in the compression elastic modulus between the first resin and the second resin is 20% or more of the magnitude of the compression elastic modulus of the second resin. In FIG. 1 and FIGS. 5 to 11 described later, for the purpose of specifying directions, XYZ axes orthogonal to each other are shown. The Z-axis indicates the vertical direction, and the X-axis and Y-axis indicate the horizontal direction. The Z-axis direction corresponds to the lamination direction of the first resin layer 21 and the second resin layer 22. In FIG. 1, when the assumed direction of the shock energy is the -Z-axis direction, the state in which the shock absorber 10 is arranged for shock absorption is shown. However, the shock absorber 10 may be arranged in a different direction. For example, the shock absorber 10 may be arranged so that the assumed shock energy and the above lamination direction are parallel.

[0009] Figure 1 shows the shock absorber 10 divided into three equal parts in the lamination direction, and each of the three parts is shown as the first laminated section 11, the second laminated section 12, and the third laminated section 13, in order from the +Z axis side (vertically upward side). In the shock absorber 10, at least two of the three laminated sections are provided with both the first resin and the second resin. The reason why it is stated as "provided with both the first resin and the second resin" rather than "provided with both the first resin layer 21 and the second resin layer 22" is that it includes cases where the boundary between adjacent laminated sections is located in the middle of the lamination direction in either the first resin layer 21 or the second resin layer 22.

[0010] Furthermore, in the shock absorber 10, the volume ratio of the first resin to the second resin differs between the first laminated section 11 and the third laminated section 13. Figure 1 shows that the third laminated section 13, which is positioned vertically downward (Z-axis direction), has a higher volume ratio of the first resin than the first laminated section 11, which is positioned vertically upward.

[0011] In this case, it is preferable that the volume ratio of the first resin in the second laminated section 12 is the same as the volume ratio of the first resin in either the first laminated section 11 or the third laminated section 13, or a value between the volume ratio of the first resin in the first laminated section 11 and the volume ratio of the first resin in the third laminated section 13. Furthermore, in each layer from the first laminated section 11 to the third laminated section 13, it is preferable that the volume ratio of the first resin is higher towards the end on the side where the third laminated section 13 is located, that is, towards the end on the lower vertical (Z-axis) side. Moreover, in the shock absorber 10, it is preferable that more than half of the total volume of the shock absorber 10 is composed of the first resin, which is a resin with a higher compressive modulus.

[0012] The compressive modulus of the first resin and the second resin are preferably, for example, 300 MPa or more, more preferably 400 MPa or more, and even more preferably 500 MPa or more. Furthermore, the compressive modulus of the first resin and the second resin are preferably 15,000 MPa or less, more preferably 14,000 MPa or less, and even more preferably 13,000 MPa or less. Such compressive modulus can be appropriately set depending on the magnitude of the impact energy to be absorbed by the impact absorber 10 and the manner in which the impact force is applied.

[0013] Furthermore, as previously described, in this embodiment, the difference in compressive modulus between the first resin and the second resin is 20% or more of the compressive modulus of the second resin, but it is preferable to make it 300% or less of the compressive modulus of the second resin.

[0014] Various resins can be used as the first and second resins, but for example, various crystalline polymers and polycarbonates represented by polyolefins such as polypropylene and polyethylene, polyamides such as polyamide 6 and polyamide 66, polyesters such as polyethylene terephthalate, or amorphous polymers such as polymethyl methacrylate can be suitably used. Alternatively, a polymer blend obtained by mixing multiple types of polymers selected from these polymers may be used. Furthermore, the first and second resins may be obtained by further mixing a soft resin such as an elastomer with the various polymers or polymer blends mentioned above. Alternatively, the first and second resins may be resin compositions further mixed with components other than resin components, such as inorganic fillers such as glass fibers. The first and second resins should be appropriately selected to satisfy the conditions related to the compressive modulus described above.

[0015] Preferably, each of the first and second resins described above contains 30% by mass or more of a common resin component. By including a common resin component in the first and second resins in this way, the adhesion at the interface between adjacent first resin layers 21 and second resin layers 22 can be improved. From the viewpoint of improving the adhesion at the interface between adjacent first resin layers 21 and second resin layers 22, it is more preferable that each of the first and second resins contains 40% by mass or more of the common resin component, and even more preferable that it contains 50% by mass or more. As the common resin component between adjacent first resin layers 21 and second resin layers 22, it is desirable to use, for example, polyamide. Polyamide generally has a relatively low tendency to undergo brittle fracture from the viewpoint of compressive modulus, and can secure a relatively large load relative to the amount of deformation, making it suitable for use as a base material for shock absorbers.

[0016] At least one of the first and second resins described above may contain 5 parts by weight or more of modified elastomer when the total amount of other components other than the modified elastomer is 100 parts by weight. By adding the modified elastomer in this way, it becomes easy to lower the compressive modulus of the first and second resins and adjust them to a desired compressive modulus. The amount of modified elastomer added to the first and second resins can be appropriately adjusted, for example, within a range of 50 parts by weight or less when the total amount of other components other than the modified elastomer is 100 parts by weight.

[0017] The shock absorber 10 can be manufactured, for example, using a 3D printer (three-dimensional molding device). Among 3D printers, fused deposition modeling (FDM) is preferred because it offers a relatively high degree of freedom in selecting resin materials. Using a 3D printer makes it easy to produce shock absorbers 10 of a desired shape, and it also makes it easy to produce shock absorbers 10 by laminating a larger number of first resin layers 21 and second resin layers 22. However, the method of manufacturing the shock absorber 10 is not particularly limited, and it is sufficient as long as it is possible to form a structure by laminating first resin layers 21 and second resin layers 22 composed of different resins, namely the first resin and the second resin. For example, the first resin layer 21 and the second resin layer 22 may be manufactured one by one by injection molding, and then each layer may be bonded together in a desired order.

[0018] The shock absorber 10 shown in Figure 1 is cylindrical, but the shape of the shock absorber 10 may be other than cylindrical. For example, it may be cylindrical. In addition to shapes where the cross-section (the plane parallel to the XY plane in Figure 1 and perpendicular to the stacking direction) is circular, such as cylindrical or cylindrical shapes, various shapes can be adopted, such as shapes where the cross-section is triangular, quadrilateral, or other polygonal. Furthermore, the diameter of the cross-section may change in the stacking direction. For example, as shown in Figure 7 later, the overall outer shape may be a cone shape or a frustocone shape that widens towards the bottom. In this way, when the shape of the shock absorber 10 is such that the side surface of the shock absorber 10 is inclined with respect to the installation surface, the angle that the side surface of the shock absorber 10 makes with respect to the installation surface when viewed from the side (viewed from a direction perpendicular to the Z axis) can be, for example, 45° to 135°. Such a shape can be easily manufactured using the 3D printer described above.

[0019] The size of the shock absorber 10, that is, the area and height of the cross-section of the shock absorber 10, can be appropriately set according to the magnitude of the impact energy that the shock absorber 10 is expected to receive and the types of the first and second resins. Here, for example, when the shock absorber 10 is formed in a cylindrical shape, the aspect ratio (ratio of height to diameter of base) of the shock absorber 10 is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less, from the viewpoint of suppressing buckling.

[0020] As described above, the impact absorber 10 of this embodiment can increase the energy absorption capacity of the impact absorber and improve its performance by satisfying the following requirements: having three or more interfaces between the first resin layer 21 and the second resin layer 22; the difference in compressive modulus between the first resin and the second resin being 20% ​​or more of the magnitude of the compressive modulus of the second resin; having both the first resin and the second resin in at least two of the three laminated sections from the first laminated section 11 to the third laminated section 13; and having different volume ratios of the first resin and the second resin in the first laminated section 11 and the third laminated section 13.

[0021] Figure 2 is an explanatory diagram showing an example of a load-displacement diagram obtained by fabricating an impact absorber 10 as shown in Figure 1, a first structure having the same external shape as the impact absorber 10 but composed only of the first resin, and a second structure having the same external shape as the impact absorber 10 but composed only of the second resin, and then conducting compression tests on these structures. As shown in Figure 2, in the first structure made of the first resin, which has a relatively large compressive modulus, the initial slope and maximum load in the load-displacement diagram are relatively large, and the amount of displacement until fracture (crush) is relatively small. In this case, even if the maximum load is relatively large, the total amount of work (amount of energy that can be absorbed) is limited because the amount of displacement until fracture (crush) is relatively small. Also, in the second structure made of the second resin, which has a relatively small compressive modulus, the initial slope and maximum load in the load-displacement diagram are relatively small, and the amount of displacement until fracture (crush) is relatively large (less likely to fracture). In this case, even if the displacement until fracture (collapse) is relatively large, the total amount of work (amount of energy that can be absorbed) is limited because the maximum load is relatively small. In contrast, in the impact absorber 10 of this embodiment, although the maximum load is smaller than that of the first structure, the initial tilt is smaller and the displacement until fracture (collapse) is relatively large. Also, the load when the displacement is large is larger than that of the second structure. As a result, it becomes possible to secure a larger total amount of work (amount of energy that can be absorbed). The specific configuration of the impact absorber 10 shown in Figure 2 and the details of the compression test will be explained in the embodiments described later.

[0022] In an impact absorber constructed using a first resin and a second resin, the principle by which the arrangement of the first resin and the second resin as described above can increase the amount of energy that the impact absorber can absorb is not clear, but for example, it can be considered as follows. That is, in the impact absorber 10 of this embodiment, the effect of slowing down the increase in initial load is enhanced because there is a large amount of the second resin, which is a soft material, at one end of the structure that receives the impact force (in the impact absorber 10 of this embodiment shown in Figure 1, the end on the +Z axis side). Also, by having a large amount of the first resin, which is a hard material, at the other end of the structure (in the impact absorber 10 of this embodiment shown in Figure 1, the end on the -Z axis side), the load when the amount of displacement becomes large can be increased more significantly, and as a result, it becomes possible to secure a large amount of overall work (amount of energy that can be absorbed).

[0023] Furthermore, in the impact absorber 10 of this embodiment, there are three or more interfaces between the first resin layer 21 and the second resin layer 22, which have different compressive moduli. As a result, stress concentration within the impact absorber 10 can be alleviated, and the impact absorber 10 can be deformed without damaging its structure, thereby increasing the overall amount of work (amount of energy that can be absorbed). Moreover, at the interface between the first resin layer 21 and the second resin layer 22, the impact absorber 10 can be easily deformed in a direction perpendicular to the direction in which the impact force is applied (Z-axis direction). Energy can also be absorbed by this deformation in the perpendicular direction. Therefore, by securing more of these interfaces, structural damage to the impact absorber 10 can be suppressed, and the overall amount of work (amount of energy that can be absorbed) can be increased.

[0024] Furthermore, when using an impact absorber to absorb impact energy, the impact absorption capacity can be enhanced by devising the shape of the impact absorber used. However, in the impact absorber 10 of this embodiment, the impact absorption capacity is enhanced by the compressive modulus (hardness) of the laminated resins and the arrangement of each resin layer. Therefore, according to the impact absorber 10 of this embodiment, the constraints on the shape for absorbing impact energy can be reduced, and the degree of freedom in shape can be increased.

[0025] When using the impact absorber 10 of this embodiment to configure an energy absorption device for absorbing impact force, the energy absorption device may consist of a single impact absorber 10, or it may consist of multiple impact absorbers 10. By providing multiple impact absorbers 10, the impact energy can be dispersed and absorbed, thereby increasing the impact absorption capacity. When providing multiple impact absorbers 10, it is desirable to align the orientation of the impact absorbers 10 with respect to the installation surface. [Examples]

[0026] <First resin and second resin> The following two types of materials were used as the constituent materials of the first resin and the second resin. • Polyamide 6 (hereinafter referred to as "PA6"): CM1017 manufactured by Toray Industries, Inc. • Modified ethylene-butylene elastomer (hereinafter referred to as "m-EBR"): Toughmer (registered trademark) MH7020, manufactured by Mitsui Chemicals, Inc.

[0027] (Preparation of the first resin) PA6 was fed into a twin-screw extruder (Technovel Co., Ltd., twin-screw extruder, KZW15-60MG) at a feeding rate of 1 kg / h, and kneaded under conditions of a kneading temperature of 250°C and a screw rotation speed of 72 rpm to produce a 3D modeling filament (hereinafter referred to as "first resin material") with a diameter of approximately 1.7 mm.

[0028] (Adjustment of the second resin) PA6 was fed into a twin-screw extruder (Technovel Co., Ltd., twin-screw extruder, KZW15-60MG) at a feeding rate of 0.7 kg / h and m-EBR at a feeding rate of 0.3 kg / h. Mixing was carried out under conditions of a mixing temperature of 250°C and a screw rotation speed of 72 rpm to produce a 3D modeling filament (hereinafter referred to as "second resin material") with a diameter of approximately 1.7 mm.

[0029] (Measurement of compressive modulus) Using a 3D printing device (FLASHFORGE Creator Pro2), the first resin material described above was molded into a cube shape with a side length of 8 mm to produce a first resin component for measuring the compressive modulus of the first resin. Similarly, using a 3D printing device (FLASHFORGE Creator Pro2), the second resin material described above was molded into a cube shape with a side length of 8 mm to produce a second resin component for measuring the compressive modulus of the second resin.

[0030] Compression tests were conducted using the first and second resin components described above, and the compressive moduli of the first and second resins were measured. The compression tests were performed using a universal testing machine (Instron, material testing machine, model 4302) with a displacement speed of 2.0 [mm / min], a maximum displacement of 1 [mm], and 3 trials. In the stress [MPa]-displacement [mm] diagram obtained from the compression tests, the slope amount in the displacement range from 0.2 mm to 0.4 mm (range from 2.5% to 5.0% of the total height) was defined as the compressive moduli [MPa].

[0031] Figure 3 is an explanatory diagram for measuring the compressive modulus of the first resin, and Figure 4 is an explanatory diagram for measuring the compressive modulus of the second resin. Figures 3(A) and 4(A) are stress-displacement diagrams, with hatching indicating the range used in the calculation of the modulus. Figures 3(B) and 4(B) show the measurement results of the compressive modulus, showing the measured values ​​from three measurements, the average value, and the standard deviation, respectively. As shown in Figures 3 and 4, the difference in compressive modulus between the first and second resins is more than 20% of the compressive modulus of the second resin.

[0032] <Manufacturing of various shock absorbers> Using the first and second resin materials described above, impact absorbers with various arrangements of the first resin layer 21 and the second resin layer 22 were fabricated, and their impact absorption capabilities were evaluated. Here, eight types of resin structures, described below as Samples S1 to S8, were fabricated as impact absorbers.

[0033] Figures 5 to 11 are schematic perspective views showing the configuration of each of the shock absorbers for samples S2 to S8. The configuration of sample S1 is shown in Figure 1, which was described earlier.

[0034] Each shock absorber was formed into a cylindrical shape using a 3D printing device (FLASHFORGE Creator Pro2). Specifically, samples S1-S3 and S5-S8 were fabricated by stacking 60 annular resin layers with a thickness of 0.2 mm to create cylindrical objects. The external dimensions of the cylindrical resin structures are 12 mm in height, 10 mm in diameter, and 1 mm in thickness. Sample S4 was similarly formed into a cylindrical shape with a height of 12 mm and a thickness of 1 mm by stacking 60 annular resin layers with a thickness of 0.2 mm, but the diameter of the cross-section changes linearly from 12 mm to 8 mm (towards the +Z axis). Hereafter, the 0.2 mm thick annular resin layers formed by the 3D printer will be referred to as "unit layers," the unit layer formed by the first resin will be referred to as the "first unit layer," and the unit layer formed by the second resin will be referred to as the "second unit layer."

[0035] Figures 12A and 12B are explanatory diagrams showing the detailed configuration of samples S1 to S8. Specifically, they indicate whether each unit layer constituting each sample, which consists of 60 layers of annular resin as described above, is a first unit layer or a second unit layer. Here, the uppermost layer (the layer at the +Z-axis end shown in Figure 1) is designated as unit layer number 1, and the lowermost layer (the layer at the -Z-axis end shown in Figure 1) is designated as unit layer number 60, indicating the order of arrangement of the first and second unit layers. The first laminated section 11 is composed of unit layers numbered 1 to 20, the second laminated section 12 is composed of unit layers numbered 21 to 40, and the third laminated section 13 is composed of unit layers numbered 41 to 60. Furthermore, the first resin layer 21 mentioned above refers to a single unit of first unit layers arranged continuously, and the second resin layer 22 refers to a single unit of second unit layers arranged continuously.

[0036] Sample S1 shown in Figure 1 has the configuration shown in Figures 12A and 12B, and the volume ratio of the first resin to the second resin in the first laminated section 11, the second laminated section 12, and the third laminated section 13 (ratio of the number of first unit layers to the number of second unit layers) is (first resin:second resin) = 1:9, 5:5, and 9:1, respectively.

[0037] Similarly, in sample S2 shown in Figure 5, the volume ratio of the first resin to the second resin in the first laminated section 11, the second laminated section 12, and the third laminated section 13 (ratio of the number of first unit layers to the number of second unit layers) is (first resin:second resin) = 5:5, 9:1, and 9:1, respectively.

[0038] In sample S3 shown in Figure 6, the volume ratios of the first resin to the second resin in the first laminated section 11, the second laminated section 12, and the third laminated section 13 (ratio of the number of first unit layers to the number of second unit layers) are (first resin:second resin) = 5:5, 9:1, and 10:0, respectively.

[0039] In sample S4 shown in Figure 7, the ratio of the first resin to the second resin (the ratio of the number of first unit layers to the number of second unit layers) in the first laminated section 11, the second laminated section 12, and the third laminated section 13 is (first resin:second resin) = 5:5, 9:1, and 9:1, respectively. Even in sample S4, which has a flared shape as shown in Figure 7, the volume ratio of the first resin to the second resin differs between the first laminated section 11 and the third laminated section 13. Furthermore, the volume ratio of the first resin in the second laminated section 12 is the same as the volume ratio of the first resin in either the first laminated section 11 or the third laminated section 13, or it is a value between the volume ratio of the first resin in the first laminated section 11 and the volume ratio of the first resin in the third laminated section 13.

[0040] In sample S5 shown in Figure 8, the volume ratio of the first resin to the second resin in the first laminated section 11, the second laminated section 12, and the third laminated section 13 (ratio of the number of first unit layers to the number of second unit layers) is (first resin:second resin) = 5:5, 5:5, and 5:5, respectively. Sample S5 is a comparative example because the volume ratio of the first resin to the second resin is the same when comparing the first laminated section 11 and the third laminated section 13.

[0041] In sample S6 shown in Figure 9, the volume ratios of the first resin and the second resin in the first laminated section 11, the second laminated section 12, and the third laminated section 13 (ratio of the number of first unit layers to the number of second unit layers) are (first resin:second resin) = 0:10, 5:5, and 10:0, respectively. Sample S6 is a comparative example because it has only one interface between the first resin layer 21 (unit layers numbered 31-60) and the second resin layer 22 (unit layers numbered 1-30).

[0042] In sample S7 shown in Figure 10, the volume ratio of the first resin to the second resin in the first laminated section 11, the second laminated section 12, and the third laminated section 13 (ratio of the number of first unit layers to the number of second unit layers) is (first resin:second resin) = 5:5, 10:0, and 10:0, respectively. Sample S7 is a comparative example because only the first laminated section 11, which is one of the three laminated sections from the first laminated section 11 to the third laminated section 13, contains both the first and second resins.

[0043] In sample S8 shown in Figure 11, the volume ratio of the first resin to the second resin (ratio of the number of first unit layers to the number of second unit layers) in the first laminated section 11, the second laminated section 12, and the third laminated section 13 are (first resin:second resin) = 3:7, 9:1, and 3:7, respectively. Sample S8 is a comparative example because the volume ratio of the first resin to the second resin is the same in the first laminated section 11 and the third laminated section 13.

[0044] <Evaluation by compression test> (Evaluation method) Compression tests were performed on each sample using a universal testing machine (Instron, material testing machine, model 4302) with a displacement speed of 2.0 [mm / min], a maximum displacement of 8 [mm], and 3 trials. The work done [N·m] was determined from the area ([N] × [m]) enclosed by the graph in the load-displacement diagram obtained from the compression test. The fracture strain [%] was recorded as the measured value at the time of fracture if the sample fractured before reaching the maximum displacement, and as 66% or higher if the sample did not fracture when reaching the maximum displacement.

[0045] Figure 13 is an explanatory diagram summarizing the magnitude of work and fracture strain obtained for samples S1 to S8 as described above. Figures 14 to 21 are explanatory diagrams showing the results of the compression tests performed on samples S1 to S8. Figures 14(A) to 21(A) show load-displacement diagrams, and Figures 14(B) to 21(B) summarize the work values ​​obtained from the above load-displacement diagrams, along with their average value and standard deviation. In Figure 13, the average work value for each sample shown in Figures 14(B) to 21(B) is shown.

[0046] The impact absorber 10, the first structure, and the second structure shown in Figure 2, as described above, are samples formed in a cylindrical shape using a 3D printing device (Creator Pro2, FLASHFORGE) with the first resin material and the second material described above, similar to samples S1 to S8, and were manufactured under the same conditions as samples S1 to S3 and samples S5 to S8. The impact absorber 10 shown in Figure 2, as with sample 1, has volume ratios of the first resin and the second resin in the first laminated section 11, the second laminated section 12, and the third laminated section 13, respectively (ratio of the number of first unit layers to the number of second unit layers) of (first resin:second resin) = 1:9, 5:5, and 9:1. Figure 2 shows the results of compression tests performed on these impact absorbers 10, the first structure, and the second structure under the conditions described above.

[0047] As shown in Figures 13 and 14-17, samples S1-S4 that satisfy all three requirements—(a) having three or more interfaces between the first resin layer 21 and the second resin layer 22, (b) having both the first resin and the second resin in at least two of the three laminated sections from the first laminated section 11 to the third laminated section 13, and (c) having different volume ratios of the first resin and the second resin in the first laminated section 11 and the third laminated section 13—did not fracture even when the strain (displacement) exceeded 66% and demonstrated high work capacity.

[0048] As shown in Figures 13 and 18-21, samples S5-S8, which did not meet at least one of the three requirements (a)-(c) described above, showed lower work output compared to samples S1-S4. In particular, sample S7 fractured with a relatively small displacement.

[0049] This disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from its spirit. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be replaced or combined as appropriate in order to solve some or all of the above-mentioned problems, or to achieve some or all of the above-mentioned effects. Furthermore, if a technical feature is not described as essential in this specification, it can be deleted as appropriate.

[0050] This disclosure can also be implemented in the following forms: [Application Example 1] It is a shock absorber, It is formed as a laminate of a first resin layer made of a first resin and a second resin layer made of a second resin having a lower compressive modulus than the first resin, and has three or more interfaces between the first resin layer and the second resin layer. The difference in compressive modulus between the first resin and the second resin is 20% or more of the magnitude of the compressive modulus of the second resin. When the impact absorber is divided into three equal parts in the lamination direction of the first resin layer and the second resin layer, and these are designated as the first laminated section, the second laminated section, and the third laminated section in order from one end in the lamination direction, at least two of the three laminated sections from the first laminated section to the third laminated section are provided with both the first resin and the second resin, The volume ratio of the first resin to the second resin is different in the first laminated portion and the third laminated portion. Shock absorber. [Application Example 2] The shock absorber described in Application Example 1, Each of the first resin and the second resin contains 30% by mass or more of a common resin component. Shock absorber. [Application Example 3] The shock absorber described in Application Example 2, The common resin component is polyamide. Shock absorber. [Application Example 4] An impact absorber as described in any one of the application examples 1 to 3, At least one of the first resin and the second resin contains 5 parts by weight or more of modified elastomer when the total amount of other components other than the modified elastomer is 100 parts by weight. Shock absorber. [Application Example 5] An impact absorber as described in any one of the application examples 1 to 4, The volume ratio of the first resin in the second laminate is the same as the volume ratio of the first resin in either the first laminate or the third laminate, or it is a value between the volume ratio of the first resin in the first laminate and the volume ratio of the first resin in the third laminate. Shock absorber. [Application Example 6] The system comprises multiple shock absorbers as described in any one of the application examples 1 to 5. Energy absorption device. [Explanation of Symbols]

[0051] 10…Shock absorber 11…First layer 12…Second layer 13…Third layer 21...First resin layer 22…Second resin layer

Claims

1. It is a shock absorber, It is formed as a laminate of a first resin layer made of a first resin and a second resin layer made of a second resin having a lower compressive modulus than the first resin, and has three or more interfaces between the first resin layer and the second resin layer. The difference in compressive modulus between the first resin and the second resin is 20% or more of the magnitude of the compressive modulus of the second resin. When the impact absorber is divided into three equal parts in the lamination direction of the first resin layer and the second resin layer, and these are designated as a first laminated section, a second laminated section, and a third laminated section in order from one end in the lamination direction, at least two of the three laminated sections from the first laminated section to the third laminated section are provided with both the first resin and the second resin, The volume ratio of the first resin to the second resin is different in the first laminated portion and the third laminated portion. Shock absorber.

2. The shock absorber according to claim 1, Each of the first resin and the second resin contains 30% by mass or more of a common resin component. Shock absorber.

3. The shock absorber according to claim 2, The common resin component is polyamide. Shock absorber.

4. The shock absorber according to claim 1, At least one of the first resin and the second resin contains 5 parts by weight or more of modified elastomer when the total amount of other components other than the modified elastomer is 100 parts by weight. Shock absorber.

5. The shock absorber according to claim 1, The volume ratio of the first resin in the second laminate is the same as the volume ratio of the first resin in either the first laminate or the third laminate, or it is a value between the volume ratio of the first resin in the first laminate and the volume ratio of the first resin in the third laminate. Shock absorber.

6. A plurality of shock absorbers according to any one of claims 1 to 5 Energy absorption device.

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