JP5095016B1 - Shock absorbing member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a high-speed flying object capable of breaking a small piece or shock stress wave generated by crushing and reliably preventing it from falling to the back side, and being lightweight and easily manufactured An impact absorbing member that is extremely useful as a component material of the tool is provided.
Disposed between a plurality of first sheet-like members 5 having a thickness of 0.1 to 50 mm made of ceramics containing 60% by mass or more of boron carbide, and adjacent first sheet-like members 5; A ceramic bonded body 15 having a bonding layer for bonding adjacent first sheet-like members 5, and the bonding layer is made of at least one metal selected from the group consisting of aluminum, copper, silver, and gold. This is an impact absorbing member 50 made of a joining material.
[Selection] Figure 1A

Description

  The present invention relates to an impact-absorbing member mainly composed of a joined body obtained by joining members made of ceramics. More specifically, it is extremely useful as a component material for protective equipment, etc., which has the characteristics of being extremely hard and high in strength while being lightweight, and having the function of absorbing the energy of high-speed flying objects with high efficiency. The present invention relates to a shock absorbing member.

  In recent years, many proposals have been made on members that are excellent in impact energy absorption and the like, which are mainly composed of ceramics. For example, Patent Document 1 describes a protective member in which an impact receiving portion made of ceramics containing boron carbide as a main component and a base made of ceramics containing silicon nitride as a main component are combined with a bonding layer made of resin. ing. Patent Document 2 describes an impact absorbing member in which a partially stabilized zirconia sheet and a sheet made of boron carbide, mullite, or the like are laminated and bonded with an epoxy resin or the like.

  On the other hand, it is known that not only the impact absorbing member but also a highly functional structural material can be obtained by laminating members made of materials such as ceramics. For example, Patent Document 3 discloses a thermal shock that includes a base material made of ceramics or a sintered alloy, an intermediate layer made of ceramics, and an outermost layer made of ceramics whose thermal expansion coefficient is smaller than the thermal expansion coefficient of the base material. A laminated sintered body useful as a strong cutting tool is described. In addition, it is described that alumina, silicon nitride, boron nitride, silicon carbide, and the like are appropriately combined as the ceramic constituting the substrate and the outermost layer.

  Patent Document 4 describes a laminated structure sintered body useful as a cutting tool used under severe conditions, including metals, ceramics such as alumina, and cermet. Further, Patent Document 5 discloses a silicon nitride sintered body having a laminated structure in which a porous silicon nitride layer and a dense silicon nitride layer are laminated and has a high tolerance for impact force, stress, or strain. Is described.

JP 2008-275208 A JP 2010-210217 A JP-A-4-319435 JP 7-137199 A JP-A-9-169571

  In any of the above-described prior arts, a material having different characteristics or a material having different characteristics such as porosity even if the same material is combined is intended to express a target function. That is, conventionally, a member having desired characteristics has been obtained by selecting and combining a plurality of materials each having unique characteristics. However, there is a possibility that the manufacturing process becomes complicated and disadvantageous in terms of cost, or industrially impeded. For example, the protective member described in Patent Document 1 is heavier than, for example, a member composed only of boron carbide, and further has a problem in terms of strength. Moreover, the impact-absorbing member described in Patent Document 2 has a problem that it is heavier than a member composed only of boron carbide.

  Furthermore, the laminated sintered body described in Patent Document 3 is heavy as an impact absorbing member, and is manufactured under conditions such that firing is performed under pressure, so that it is difficult to increase the size. Moreover, since the laminated structure sintered body described in Patent Document 4 is manufactured using the chemical reaction heat of silicon, it is difficult to control the temperature and the like, and it is also difficult to increase the size. In addition, the silicon nitride sintered body described in Patent Document 5 has problems in terms of cost and size, and also has problems in stably supplying materials.

  The present invention has been made in view of such problems of the prior art, and the problem is that the high-speed flying object can be destroyed and the energy of the small pieces generated by being crushed Providing a shock absorbing member that is extremely useful as a component of protective equipment and can be easily manufactured with a light weight that can prevent the shock stress wave from coming back to the back side. There is to do.

The present inventors have a result of intensive studies to achieve the above object, a plurality of first sheet-like member having a predetermined thickness made of ceramics, by joining using a bonding material containing aluminum, the problems Has been found to be possible to achieve the present invention.

That is, according to the present invention, the following impact absorbing member is provided.
[1] A plurality of first sheet-like members having a thickness of 0.1 to 50 mm made of ceramics containing 60% by mass or more of boron carbide and the adjacent first sheet-like members are adjacent to each other. wherein a first bonding layer for bonding the sheet-like member to each other, comprising a ceramic joined body having the bonding layer, the shock-absorbing member made of a bonding material containing aluminum.
[2] The impact-absorbing member according to [1], wherein 2 to 1000 sheets of the first sheet-like member are stacked in the thickness direction.
[3] The impact absorbing member according to [2], wherein the thickness of the first sheet-like member increases stepwise from the front side to the back side of the ceramic joined body.
[4] One or more second sheet-like members made of silicon carbide, mullite, or alumina, wherein the ceramic joined body is disposed by being laminated on the first sheet-like member via the joining layer. The shock absorbing member according to [2] or [3].
[5] The impact absorbing member according to any one of [1] to [4], wherein the bonding layer has a thickness of 0.001 to 1 mm.
[6] The impact-absorbing member according to any one of [1] to [5], further including a receiving layer that is disposed on the back side of the ceramic bonded body and receives a fragment generated at the time of breakage.

  The impact absorbing member of the present invention is a thin and lightweight plate-like member, but can sufficiently absorb the kinetic energy of the colliding high-speed flying object. Furthermore, it is possible to destroy the colliding high-speed flying object, minimizing the energy of the small pieces generated by being crushed, and reliably preventing the shock wave from escaping to the back side (back). it can. And since it can manufacture simply, it is excellent also economically. In particular, by appropriately combining the thickness of the sheet-like member (plate-like member) made of ceramics containing boron carbide and the number of laminated layers, the kinetic energy of the high-speed flying object compared to the members described in Patent Documents 1 and 2 above. An impact-absorbing member having high functionality and high functionality in which the outermost surface is difficult to break when a high-speed flying object collides is provided.

It is a fragmentary sectional view showing typically one embodiment of an impact-absorbing member of the present invention. FIG. 1B is a partially enlarged view of the shock absorbing member shown in FIG. 1A. It is a fragmentary sectional view showing typically other embodiments of an impact-absorbing member of the present invention. It is a fragmentary sectional view showing typically other embodiment of an impact-absorbing member of the present invention typically.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments for carrying out the present invention. In the prior art, boron carbide is simply selected as a constituent material of the shock absorbing member from the viewpoints of weight reduction, high strength, and high hardness. On the other hand, the present inventors efficiently absorb the kinetic energy of the high-speed flying object in order to make the member capable of exhibiting an excellent function as a protector while maintaining light weight, It has come to the recognition that it is important to ensure that damage to people, vehicles, etc. existing inside the shock absorbing member due to the fragments generated at the time of high-speed flying object collision can be reduced. And the present inventors performed various examination about the boron carbide as a constituent material of an impact-absorbing member from this recognition.

  As a result, a plurality of sheet-like (thin plate-like) members made of ceramics whose main component is boron carbide are laminated, and a joined body obtained by low-temperature joining with a specific metal is a plate of the same thickness that is not joined ( It was found that the impact absorption ability is significantly different from that of the non-bonded body. Such a joined body statically exhibited almost the same mechanical characteristics as a non-joined body. However, this joined body can destroy the high-speed flying object at the time of collision with the high-speed flying object, and at the same time, can absorb the kinetic energy of the high-speed flying object with high efficiency. Further, since the surface is finely broken, the spread of the shock wave is suppressed, and the shape of the surface on which the high-speed flying object collides can be easily maintained. In addition, the impact absorbing member of the present invention can destroy the colliding high-speed flying object by joining a plurality of sheet-like members with a joining material containing a specific metal, and at the same time, the shock wave passing through the impact absorbing member. It is considered that the progress is hindered by a high stress field existing inside the ceramic joined body. Further, as a result of the study, the present inventors have found that the kinetic energy of a high-speed flying object can be converted into surface energy more efficiently by making the sheet-like member thinner and increasing the number of laminated sheets.

  Boron carbide has been conventionally used as a constituent material for impact absorbing members. However, since boron carbide is an extremely expensive material, it has been used only in situations where high-speed flying objects having extremely high kinetic energy can collide. On the other hand, the impact absorbing member of the present invention can reduce the thickness of the ceramic joined body obtained by joining a plurality of sheet-like members containing boron carbide. For this reason, it is possible to reduce the weight and greatly contribute to cost reduction. That is, as a result of weight reduction, energy consumption during movement or transportation during use can be reduced. For this reason, the burden on a human body or a vehicle can be reduced. Furthermore, since the sheet-like member can be thinned, it is possible to shorten the time for the firing process and the like. Further, even when the surface is formed with an uneven surface, it is extremely advantageous in terms of cost. Therefore, the manufacturing cost is lower than that of a conventional shock absorbing member, and its practical value is extremely high. Therefore, the impact absorbing member of the present invention is expected to be employed in various technical fields as well as in situations where high-speed flying objects may collide.

  FIG. 1A is a partial cross-sectional view schematically showing an embodiment of the shock absorbing member of the present invention. FIG. 1B is a partially enlarged view of the impact absorbing member shown in FIG. 1A. As shown in FIGS. 1A and 1B, the shock absorbing member 50 of the present embodiment includes a bonding layer 65 disposed between a plurality of first sheet-like members 5 made of ceramics and an adjacent first sheet-like member. And a ceramic joined body 15 having the following. The 1st sheet-like member 5 is laminated | stacked and arrange | positioned in the thickness direction. The joining layer 65 joins the adjacent first sheet-like members 5 together. The ceramic which is a constituent material of the first sheet-like member 5 contains boron carbide in an amount of 60% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. By laminating the first sheet-like member formed of ceramics containing boron carbide, extremely excellent shock absorption can be obtained. In addition, although the upper limit of the ratio of the boron carbide contained in ceramics is not specifically limited, It is most preferable that it is 100 mass%.

  The thickness of the 1st sheet-like member 5 is 0.1-50 mm, Preferably it is 1-10 mm. If the thickness of the first sheet-like member is less than 0.1 mm, it may be too thin to be practical in production. On the other hand, if the thickness of the first sheet-like member is more than 50 mm, the impact absorbability is lowered.

  The number of the first sheet-like members constituting the ceramic bonded body is not particularly limited as long as it is plural, but is usually 2 to 1000, preferably 5 to 50. If the number of first sheet-like members stacked is too small, the effect obtained by stacking may be insufficient. On the other hand, when the number of laminated first sheet-like members is too large, the effect reaches a peak and the obtained ceramic joined body becomes heavy, and the handleability as a protective device tends to be lowered.

  Boron carbide contained in the ceramics constituting the first sheet-like member 5 has high hardness and low specific gravity. For this reason, the 1st sheet-like member 5 arrange | positioned on the outermost surface which a high-speed flying object collides can destroy the high-speed flying object which collided by the characteristic of boron carbide. The ceramic joined body 15 formed by laminating and joining a plurality of first sheet-like members exhibits the mechanical characteristics of boron carbide and has a high stress field at the joining interface. For this reason, when the high-speed flying object collides, the kinetic energy of the high-speed flying object is absorbed by the first sheet-like member 5 being finely broken. In addition, it is preferable that the relative density of the 1st sheet-like member consisting of boron carbide is a dense material of 89% or more. As described above, a ceramic joined body obtained by laminating and joining a plurality of first sheet-like members made of ceramics mainly composed of boron carbide has a high stress field therein. This stress field deflects a shock wave at the time of collision of a high-speed flying object passing through the ceramic bonded body. Thereby, the impact to the inside of the shock absorbing member of the present invention is remarkably reduced.

  The bonding layer 65 is formed of a bonding material. In the present invention, the bonding layer is formed of a bonding material containing at least one metal selected from the group consisting of aluminum, copper, silver, and gold in consideration of strength, specific gravity, process simplicity, and the like. Moreover, the bending strength of the ceramic joined body 15 constituting the impact absorbing member 50 of the present embodiment is preferably 100 MPa or more. In addition, the “bending strength” in the present specification means a physical property value of a ceramic joined body including a joint portion measured by a four-point bending method.

  The thickness of the bonding layer 65 is preferably 0.001 to 1 mm, more preferably 0.005 to 0.1 mm, and preferably 0.01 to 0.05 mm. Note that the thickness of the bonding layer can be adjusted by changing the amount (thickness) of the bonding material used. If the thickness of the bonding layer is less than 0.001 mm, the bonding strength may be insufficient. On the other hand, if the thickness of the bonding layer is more than 1 mm, the bonding strength may be insufficient due to the excessive amount of metal and the ceramic floating.

  Since boron carbide is lightweight and has a low fracture toughness value, it breaks up more finely when an impact is applied. For this reason, boron carbide is suitable as a material for constituting the shock absorbing member of the present invention. In addition, the present inventors have already developed the technique which produces boron carbide economically (refer international publication 2008/153177). If this technique is utilized, not only a sheet-like member but various shaped members made of boron carbide can be provided at a lower cost. Furthermore, the present inventors have already developed an industrially useful technique for joining members made of boron carbide (see Japanese Patent Application No. 2010-253236). If this technology is used, application to a wider range of impact absorbing members is expected.

  In the impact-absorbing member of the present invention, it is preferable that the ceramic joined body further includes one or more second sheet-like members arranged by being laminated on the first sheet-like member via a joining layer. Examples of the material constituting the second sheet-like member include ceramics such as silicon carbide, mullite, and alumina. When a ceramic joined body is configured by combining the second sheet-like member made of these ceramics with the first sheet-like member, the impact on the inside (human body, vehicle, etc.) of the second sheet-like member is further mitigated. Therefore, it is more useful as a component of the protective equipment. This is because the second sheet-shaped member made of the above ceramics has a high ability to convert the kinetic energy of the high-speed flying object into surface energy.

  FIG. 2 is a partial cross-sectional view schematically showing another embodiment of the impact absorbing member of the present invention. The impact absorbing member 55 of the embodiment shown in FIG. 2 includes a ceramic joined body 15 in which a plurality of first sheet-like members 5 are joined via a joining layer (not shown), and a back surface side of the ceramic joined body 15. And a receiving layer made up of the third sheet-like member 30 and the fourth sheet-like member 40. By providing such a receiving layer on the back side of the ceramic joined body, it is possible to more reliably receive debris generated by breakage of the ceramic joined body and make it less likely to penetrate through the back side. FIG. 2 shows a state in which the receiving layer 70 composed of the third sheet-like member 30 and the fourth sheet-like member 40 is arranged. However, the receiving layer 70 is composed only of the third sheet-like member. Alternatively, it may be composed of only the fourth sheet-like member.

  Examples of the material constituting the third sheet-like member 30 include high-strength fibers such as aramid fibers. Moreover, as a material which comprises the 4th sheet-like member 40, the metal with small specific gravity like aluminum and magnesium can be mentioned. These materials constituting the third sheet-like member and the fourth sheet-like member are often provided in a plate shape and are preferable materials because of their low cost. In addition, the 4th sheet-like member comprised with the metal etc. is good to arrange | position on the side (back side) furthest from the outermost surface which opposes the person or vehicle etc. used as protection object.

  FIG. 3 is a partial cross-sectional view schematically showing still another embodiment of the impact absorbing member of the present invention. The impact absorbing member 60 of the embodiment shown in FIG. 3 includes a ceramic joined body 25, and a third sheet-like member 30 and a fourth sheet-like member that are disposed on the back side of the ceramic joined body 25 and serve as a receiving layer. 40. And this ceramic joined body 25 is comprised so that the thickness of the 1st sheet-like members 10 and 20 may increase in steps toward the back surface side from the surface side. Thus, by increasing (thickening) the thickness of the sheet-like members 10 and 20 stepwise from the front surface side to the back surface side, a distribution occurs in the inherent stress field. For this reason, the propagation direction of the shock wave generated at the time of the collision of the high-speed flying object is changed, and the size of the ceramic piece generated by the breakage of the ceramic bonded body is controlled, and the scattering to the back side is more effectively prevented. The

  A case is assumed in which a high-speed flying object collides with the surface side of the impact absorbing member 60 shown in FIG. In this case, the high-speed flying object colliding with the first sheet-like member 10 is destroyed, and the ceramic containing boron carbide constituting the first sheet-like member 10 is finely destroyed. For this reason, the kinetic energy of the high-speed flying object is efficiently absorbed. Moreover, the thicker 1st sheet-like member 20 arrange | positioned at the back side of the 1st sheet-like member 10 is damaged by the attenuated shock wave, and a big fragment is formed. As a result, the kinetic energy of the high-speed flying object is almost completely absorbed. The fragments generated by the breakage of the ceramic joined body 25 are absorbed by the third sheet-like member 30 and the fourth sheet-like member 40 which are the receiving layers 70 disposed on the back side of the ceramic joined body 25, and Do not penetrate to the side. The ceramic joined body 25 is configured such that the thickness of the first sheet-like members 10 and 20 increases stepwise from the front surface side toward the back surface side, thereby making the thickness of the ceramic joined body 25 thinner. This makes it possible to significantly reduce the weight of the shock absorbing member 60 while maintaining the same or higher function than the conventional one.

  As described above, the first sheet-like member 5 constituting the impact absorbing member 50 shown in FIG. 1A is arranged in a stacked manner in the thickness direction. However, in the present invention, the plurality of first sheet-like members are not limited to being stacked and arranged in the thickness direction, and may be arranged in the horizontal direction, for example. When a plurality of first sheet-like members are arranged side by side in the horizontal direction, the bonding layer is arranged between the end faces (narrow end faces) of the adjacent first sheet-like members, and the adjacent first sheet-like members are arranged. Join each other. By comprising in this way, it becomes possible to make the shape of the impact-absorbing member of this invention into a bending shape. For this reason, for example, it is possible to easily obtain an impact-absorbing member molded in accordance with a bent shape such as a human shoulder or elbow.

  In the ceramic joined body constituting the impact absorbing member of the present invention, for example, a joining material containing a metal such as aluminum is interposed in a portion where the first sheet-like member members are joined together. What is necessary is just to arrange | position to the predetermined location so that the thickness of a joining material may be set to 1 mm or less in general. Moreover, what is necessary is just to arrange | position a joining material in the state in any one of foil, a paste, and a vapor deposition layer, for example. If it hold | maintains in this state and the part to join at least in the inert atmosphere or air | atmosphere in vacuum conditions is heated at the temperature of 600-1500 degreeC, a ceramic joined body can be obtained.

  In addition, (1) When heating in vacuum conditions, it is good to heat at least the part to join at the temperature of 600-1200 degreeC. Moreover, (2) When heating in inert atmosphere, it is good to heat at least the part to join at the temperature of 600-1500 degreeC. Further, (3) when heating in the atmosphere, at least the part to be joined should be heated at a temperature of 600 ° C. or higher and lower than 800 ° C.

  Since aluminum has good wettability with boron carbide, it is considered that aluminum can be easily distributed uniformly on the joint surface. Aluminum forms various compounds with boron carbide to form aluminum boride and a compound of aluminum, carbon and boron. For this reason, when a bonding material containing 90% by mass or more of aluminum is interposed between the first sheet-like members and heated at a temperature equal to or higher than the melting point of aluminum while maintaining this state, the aluminum is uniform on the bonding surface. In this state, it is considered that a bonding layer in which boron carbide and aluminum react to form a mixture is formed. That is, in the bonding layer, aluminum is not present alone, but aluminum boride, aluminum borohydride, and the like are generated and mixed together. As a result, the first sheet-like shape is formed through the bonding layer. The members are firmly joined together. For this reason, it is presumed that a ceramic joined body which has a joining strength of 100 MPa or more, which is almost close to the strength of ceramics composed only of boron carbide, which could not be obtained by the conventional technique can be obtained.

In the bonding layer formed as described above, metallic aluminum; Al ₃ BC, Al ₃ B ₄₈ C ₂ , AlB ₁₂ C ₂ , Al ₈ B ₄ C ₇ , Al ₂ B ₅₁ C ₈ , AlB ₄₀ C ₄ , and any of the aluminum borides represented by AlB ₂₄ C ₄ ; any of the aluminum borides represented by AlB ₂ , AlB ₁₀ , and AlB ₁₂ . The ceramic joined body obtained as described above has, for example, cracks and / or pores on the surface of the first sheet-like member in the joining layer, and the joining material inside these cracks and pores. Has penetrated. For this reason, the adjacent first sheet-like members are firmly integrated by the anchor effect of the bonding material that has penetrated into the cracks and pores.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

(Production of first sheet-like member)
After filling commercially available boron carbide (B ₄ C) powder into a 9 cm square mold and pressurizing at a pressure of 200 kg / cm ² , hydrostatic pressing is performed at a pressure of 1000 kg / cm ² , and after firing and processing A boron carbide molded body having a thickness of 0.1 to 50 mm was obtained. The boron carbide powder used had an average particle size of 0.8 μm and a purity of 99.5% (excluding oxygen content of 1.2% and nitrogen content of 0.2%). The obtained boron carbide molded body was placed in a firing furnace in which aluminum and silicon were arranged, and was fired under normal pressure at 2200 ° C. for 4 hours while flowing argon (Ar) gas to obtain a fired body. The fired bodies obtained so as to have a thickness of 0.1 to 50 mm were ground using a diamond grindstone to obtain 7 cm square first sheet-like members made of boron carbide. All of the obtained first sheet-like members were extremely dense with a relative density of 95% or more.

(Preparation of receiving layer)
A plurality of 1 mm thick sheets composed of aramid fibers (Kevlar: registered trademark, manufactured by DuPont) made of a commercially available aromatic aramid resin are laminated and integrated with an epoxy resin, a thickness of 3 mm, A 7 cm square third sheet-like member was prepared. In addition, an aluminum metal plate having a thickness of 4 mm and a 7 cm square was prepared and used as a fourth sheet-like member.

Example 1
100 sheets of a first sheet-like member having a thickness of 0.1 mm were laminated with an aluminum film (purity: 99%) having a thickness of 10 μm interposed therebetween to obtain a laminate. The obtained laminate was heated in vacuum at 100 ° C. for 2 hours, and the first sheet-like member was joined to obtain a ceramic joined body having a thickness of 10 mm. The obtained ceramic joined body was used as an impact absorbing member (Example 1).

(Examples 2 to 5, Comparative Example 1)
Except that the thickness and number of sheets of the first sheet-like member are as shown in Table 1, the impact absorbing member that is a ceramic joined body (Examples 2 to 5 and Comparative Example 1) in the same manner as in Example 1 above. Got.

(Comparative Example 2)
A first sheet-like member having a thickness of 10 mm that was not joined using an aluminum film was used as an impact absorbing member (Comparative Example 2).

(Impact fracture test (1))
An impact fracture test was performed using a gas accelerator that transmits the pressure of the compressed gas to the flying object and causes the flying object that passed through the launch tube to collide with the sample. As the flying object, bearing steel having a diameter of 4 mmφ was used. In addition, the flying object collided and penetrated the sample (impact absorbing member) at almost the speed of sound, and the damaged volume (cm ³ ) and the average diameter (mm) of the generated small pieces were measured. The results are shown in Table 1.

(Evaluation)
As shown in Table 1, the thinner the first sheet-like member, the smaller the damaged volume at the location destroyed on the cone, and the smaller the average diameter of the small pieces produced by the destruction (Examples 1-5, Comparative Examples). 2). However, since the impact absorbing member of Comparative Example 1 (thickness of the first sheet-like member = 0.05 mm) was damaged such that the joining surfaces of the first sheet-like members were peeled off, It was impossible to measure the average diameter of the small pieces. In addition, it was found that the impact absorbing member of Comparative Example 2 composed of only the first sheet-like member having a thickness of 10 mm that was not joined had a large damaged volume because large pieces were scattered backward. The impact absorbing member of Comparative Example 2 was obtained by laminating 100 sheets of the first sheet-like member having a thickness of 0.1 mm, whereas cracks occurred indefinitely on the surface where the flying object collided. In the shock absorbing member of Example 1, almost no vertical and horizontal cracks were observed.

(Example 6)
Twenty first sheet-like members having a thickness of 5 mm were laminated with an aluminum film (purity: 99%) having a thickness of 10 μm interposed therebetween to obtain a laminate. The obtained laminate was heated in vacuum at 100 ° C. for 2 hours, and the first sheet-like member was joined to obtain a ceramic joined body having a thickness of 100 mm. The obtained ceramic joined body was used as an impact absorbing member (Example 6).

(Examples 7 to 9)
Except that the thickness and number of sheets of the first sheet-like member were as shown in Table 2, impact-absorbing members (Examples 7 to 9), which were ceramic joined bodies, were obtained in the same manner as in Example 6 described above.

(Comparative Example 3)
A first sheet-like member having a thickness of 100 mm, which was not joined using an aluminum film, was used as an impact absorbing member (Comparative Example 3).

(Impact fracture test (2))
A destructive test was performed in the same procedure as the “impact destructive test (1)” except that the flying object collided with the sample (impact absorbing member) at a speed about three times the speed of sound. In any of the impact absorbing members (Examples 6 to 9 and Comparative Example 3), the flying object did not penetrate. Therefore, the surface on which the flying object collided was visually observed to determine “crack degree” and “crack interval”. Was evaluated. The results are shown in Table 2.

(Evaluation)
As shown in Table 2, the impact absorbing member of Comparative Example 3 had many cracks and the crack spacing was narrow. On the other hand, in the impact absorbing members of Examples 6 to 9, the more the number of the first sheet-like members stacked, and the thinner the first sheet-like member, the fewer cracks generated and the wider the interval. It is clear that this tends to be

(Example 10)
The ceramic joined body (thickness 10 mm) produced in Example 3, a sheet made of aramid fibers, laminated with an epoxy resin (thickness 10 mm), and an aluminum metal plate (thickness 10 mm) The impact absorbing member (Example 10) having a layer structure as shown in FIG. 1B was laminated in order.

(Comparative Example 4)
The first sheet-like member having a thickness of 10 mm used in Comparative Example 2, a sheet made of aramid fibers, laminated with an epoxy resin (thickness 10 mm), and an aluminum metal plate (thickness 10 mm) Were laminated in this order to produce an impact absorbing member (Comparative Example 4).

(Evaluation)
The impact absorbing member of Example 10 and Comparative Example 4 was subjected to the aforementioned “impact breaking test (1)”. As a result, the flying object was destroyed on the surface of any shock absorbing member. However, the back surface (aluminum metal plate) of the shock absorbing member was in a different situation. In the impact absorbing member of Comparative Example 4, a hole having a diameter of about 2 mm was formed in the aluminum metal plate. On the other hand, in the impact absorbing member of Example 10, no change in appearance was observed in the aluminum metal plate.

(Example 11)
Four first sheet-like members having a thickness of 0.5 mm were laminated with an aluminum film (purity: 99%) having a thickness of 10 μm interposed therebetween. Furthermore, five 1 mm-thick first sheet-like members were laminated with a 10 μm-thick aluminum film (purity: 99%) interposed therebetween to obtain a laminate. The obtained laminate was heated in vacuum at 100 ° C. for 2 hours, and the first sheet-like member was joined to obtain a ceramic joined body having a thickness of 7 mm. The obtained ceramic joined body, sheets made of aramid fibers are laminated, a sheet integrated with an epoxy resin (thickness 10 mm), and an aluminum metal plate (thickness 10 mm) are laminated in this order, and FIG. An impact absorbing member (Example 11) having a layer structure as shown was produced.

(Evaluation)
The impact absorbing member of Example 11 was subjected to the aforementioned “impact fracture test (1)”. As a result, the flying object was destroyed on the surface of the impact absorbing member, and no change in the appearance of the aluminum metal plate was observed.

  From the above results, it has been found that by using a ceramic joined body obtained by joining a larger number of thinner first sheet-like members, higher shock absorption is exhibited.

  The shock absorbing member of the present invention exhibits a high shock absorption equivalent to or higher than that of the conventional product, and can be made thinner, so that it is lighter than the conventional product and is suitable as a material for forming a protective device. is there. As an application example of the impact absorbing member of the present invention, it is possible to reliably reduce the impact that may be exerted on human bodies, vehicles, etc. from various high-speed flying bodies, while suppressing the burden on human bodies, vehicles, etc. And various protective products such as a robot arm that can be moved at high speed.

5, 10, 20: first sheet-like member 15, 25: ceramic joined body 30: third sheet-like member 40: fourth sheet-like member 50, 55, 60: shock absorbing member 65: joining layer 70: Receptive layer

Claims (6)

A plurality of first sheet-like members having a thickness of 0.1 to 50 mm made of ceramics containing 60% by mass or more of boron carbide;
A ceramic joined body that is disposed between the adjacent first sheet-like members and has a joining layer that joins the adjacent first sheet-like members;
The bonding layer is, the shock absorbing member made of a bonding material containing aluminum.   The impact-absorbing member according to claim 1, wherein 2 to 1000 sheets of the first sheet-like member are laminated and arranged in the thickness direction.   The impact absorbing member according to claim 2, wherein the thickness of the first sheet-like member increases stepwise from the front surface side to the back surface side of the ceramic joined body.   The ceramic joined body further includes one or more second sheet-like members made of silicon carbide, mullite, or alumina, which are disposed to be laminated on the first sheet-like member via the joining layer. The impact absorbing member according to 2 or 3.   The impact absorbing member according to any one of claims 1 to 4, wherein the bonding layer has a thickness of 0.001 to 1 mm.   The impact-absorbing member according to any one of claims 1 to 5, further comprising a receiving layer that is disposed on a back surface side of the ceramic joined body and receives a fragment generated at the time of breakage.

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