JP2015187202A - Fiber-reinforced composite material, method for manufacturing fiber-reinforced composite material, and method for fixing fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced composite material that can be fixed to another member by an easy method and prevents breakage or defects upon fixing, and to provide a fiber-reinforced composite material having superior strength.SOLUTION: The fiber-reinforced composite material comprises reinforcing fiber and a thermoplastic resin. The fiber-reinforced composite material has a low-density region and a high-density region, in which a density P of the low-density region and a density Q of the high-density region satisfy 1.5P<Q, and a proportion of an area occupied by the low-density region to the whole area of the fiber-reinforced composite material is 0.001 to 15%.

Description

  The present invention relates to a fiber reinforced composite material, a method for producing a fiber reinforced composite material, and a method for fixing a fiber reinforced composite material. Specifically, the present invention is a fiber-reinforced composite material including a reinforced fiber and a thermoplastic resin, and having a low density region and a high density region, and fixing the minimum necessary low density region to a fixing bracket or the like. The present invention relates to a fiber-reinforced composite material or the like that is provided for penetration of a member.

  Conventionally, metal materials such as aluminum materials have been generally used as structural materials used in fields such as sports, leisure goods, and aircraft materials. Since metal materials such as aluminum have isotropic mechanical properties, stress is not concentrated even if holes are provided when fixing to other members, etc. It is possible to fix to this member. However, since the specific gravity of the metal material is larger than that of other materials, there is a problem that the weight of the structural material is increased.

Therefore, in recent years, it has been studied to use a fiber-reinforced composite material obtained by heat-pressing a nonwoven fabric containing a reinforcing fiber such as carbon fiber or glass fiber and a thermoplastic resin as a structural material. Since such a fiber reinforced composite material has a smaller specific gravity than a metal material, the structural material can be reduced in weight. Furthermore, the fiber reinforced composite material is a very useful material having characteristics such as high strength, high elasticity, a low coefficient of thermal expansion, and no rust.
However, since the fiber reinforced composite material has high strength and high elasticity, there is a problem that it is easily broken when a screw, a rivet or the like is passed through. In recent years, when fixing a fiber reinforced composite material to other members, for the sake of efficiency, a method of directly fixing with a tapping screw, a drill screw or the like without opening a pilot hole has been frequently used. Defects such as cracks are likely to occur, which is a problem. In addition, the fiber reinforced composite material has a coefficient of thermal expansion that is significantly different from that of other materials, such as metal. Therefore, when the material is fixed to a material of another material, a local stress is generated in the fixing portion due to a temperature change, causing damage. There is also a problem that there are many cases.

  In order to solve such problems, for example, in Patent Documents 1 and 2, the inside of a fiber reinforced composite material is reduced in density, and the occurrence of cracking is suppressed by reinforcing the fiber reinforced composite material with a metal cap. Has been proposed. In the structures disclosed in Patent Documents 1 and 2, a fiber reinforced composite material (fiber reinforced plastic) is used for the outer layer portion, and a low-strength resin or a lightweight core material is used for the inner layer portion. Further, the fiber reinforced composite material is covered with a metal cap.

JP-A-5-77322 JP-A-5-69487

  However, since the structures as described in Patent Documents 1 and 2 have a low density region inside, they have a problem that they are weak against impact from the outside and their strength is not sufficient. Moreover, in order to form a structure, a high-density outer layer and a low-density inner layer must be separately prepared and bonded, which has a demerit that productivity does not increase.

  Furthermore, in the structures as described in Patent Documents 1 and 2, even when a metal cap is used, cracks occur in the fiber-reinforced composite material when the fixing member is passed through the fiber-reinforced composite material. It has become clear from the study of the present inventors that there is a case of such a case. In addition, since a metal cap is used as a reinforcing material, not only the handling property at the time of fixing is deteriorated, but also there is a problem that it conflicts with the weight reduction of the fiber-reinforced composite.

  In addition, when fixing a fiber reinforced composite material and another member, in order to prevent a crack of a fiber reinforced composite material, the method of bonding using an adhesive agent is also considered. However, pasting has the disadvantages that it takes time to cure and the productivity is low. In addition, there is a problem that it cannot be applied to places that need to be removed for repair or inspection.

  Therefore, in order to solve the problems of the prior art, the present inventors are a fiber reinforced composite material that can be fixed to another member by a simple method such as screwing, and are broken or defective at the time of fixing. The study was carried out for the purpose of providing a fiber-reinforced composite material that does not cause any problems. Furthermore, the present inventors have made studies for the purpose of providing a fiber-reinforced composite material having excellent strength in addition to having the above-described aptitude at the time of fixation.

As a result of intensive studies to solve the above problems, the present inventors have found that each of the regions in the fiber reinforced composite material including the reinforced fiber and the thermoplastic resin and having the low density region and the high density region. Fiber reinforced that can be fixed to other members by a simple method by setting the density as a specific condition, the portion where the fixing member penetrates is a low density region, and the ratio of the low density region is within a predetermined range It has been found that a fiber reinforced composite material which is a composite material and does not cause breakage or defects during fixation can be obtained. Furthermore, the present inventors have found that the fiber-reinforced composite material as described above has excellent strength, and have completed the present invention.
Specifically, the present invention has the following configuration.

[1] A fiber reinforced composite material including a reinforced fiber and a thermoplastic resin, wherein the fiber reinforced composite material has a low density region and a high density region, and the density of the low density region is P, and the high density If the density of the region is Q, 1.5P <Q, and the ratio of the low-density region to the total area of the fiber-reinforced composite material is 0.001 to 15%. Reinforced composite material.
[2] The fiber-reinforced composite material according to [1], wherein the low-density region is a region for allowing the fixing member to pass therethrough.
[3] The reinforcing fiber is composed of fibers having a fiber diameter of 20 μm or less, a glass transition temperature of 210 ° C. or more, and an elastic modulus of 50 GPa or more [1] or [2] The fiber-reinforced composite material described in 1.
[4] The fiber according to any one of [1] to [3], wherein the mass ratio of the reinforcing fiber and the thermoplastic resin is substantially constant in the entire region of the molded sheet. Reinforced composite material.
[5] The fiber reinforcement according to any one of [1] to [4], wherein a content mass ratio of the reinforcing fiber and the thermoplastic resin is 0.2: 1 to 10: 1. Composite material.
[6] The fiber-reinforced composite material according to any one of [1] to [5], wherein the fiber-reinforced composite material has a concavo-convex structure, and the highest point of the convex portion belongs to a low density region. .
[7] The fiber reinforced composite material according to any one of [1] to [6], wherein the low density region is formed as a discontinuous region in the fiber reinforced composite material.
[8] The fiber-reinforced composite material according to any one of [1] to [7], wherein the reinforcing fibers are glass fibers or carbon fibers.
[9] The fiber-reinforced composite material according to any one of [1] to [8], wherein the thermoplastic resin is polyetherimide, polycarbonate, nylon, polypropylene, or polyphenylene sulfide.
[10] The fiber-reinforced composite material according to any one of [1] to [9], wherein a through hole is further provided in the low density region.
[11] The fiber-reinforced composite material according to [10], wherein the total area of the low density region and the through hole is greater than 1 and less than or equal to 4 times the area of the through hole.
[12] A step of mixing a reinforcing fiber and a thermoplastic resin fiber, producing a nonwoven fabric sheet by a dry nonwoven fabric method or a wet nonwoven fabric method, and heating the nonwoven fabric sheet at a temperature equal to or higher than the glass transition temperature of the thermoplastic resin fiber A step of press-molding, wherein the step of heat-press molding includes a step of pressurizing a region to be penetrated through the fixing member of the nonwoven fabric sheet at a pressure lower than an average pressure. A method of manufacturing the material.
[13] The production of a fiber-reinforced composite material according to [12], wherein the heat and pressure forming step includes a step of pressing a mold having a concave portion against the nonwoven fabric sheet and performing a press process. Method.
[14] A step of mixing reinforcing fibers and thermoplastic resin fibers to produce a nonwoven fabric sheet by a dry nonwoven fabric method or a wet nonwoven fabric method, laminating a plurality of the nonwoven fabric sheets, and a glass transition temperature of the thermoplastic resin fibers Including the step of heat-press molding at the above temperature, wherein the step of heat-press molding is a low-density region by reducing the number of laminated nonwoven sheets in the region to be penetrated by the fixing member. A method for producing a fiber-reinforced composite material.
[15] The area according to any one of [12] to [14], wherein the area of the region to be penetrated by the fixing member is 0.001 to 15% of the total area of the nonwoven fabric sheet. Manufacturing method of fiber reinforced composite material.
[16] The process of [12] to [15], wherein the step of heating and pressing includes a step of heating to Tg to Tg + 100 ° C. when the glass transition temperature of the thermoplastic resin is Tg. The manufacturing method of the fiber reinforced composite material of any one of Claims 1.
[17] A fiber-reinforced composite material produced by the production method according to any one of [12] to [16].
[18] A fixing method of fixing the fiber-reinforced composite material according to any one of [1] to [11] and [17] to a fixing target member using a fixing member, wherein the fixing member is A fixing method comprising fixing the member to be fixed and the fiber reinforced composite material by passing through a low density region of the fiber reinforced composite material.
[19] The area of the low-density region that penetrates the fixing member is larger than one time with respect to the area of the through hole formed when the fixing member is penetrated through the low-density region of the fiber-reinforced composite material. The fixing method according to [18], wherein the fixing method is 4 times or less.
[20] The area of the low density region that penetrates the fixing member is 0.5 to 1 with respect to the area of the through hole formed when the fixing member is penetrated through the low density region of the fiber-reinforced composite material. The fixing method according to [18], wherein the fixing method is doubled.
[21] The fixing method according to [18], wherein a low-density region does not remain in the fiber-reinforced composite material after passing through the fixing member.
[22] A fiber-reinforced composite material fixed to the member to be fixed, obtained by the fixing method according to [19].
[23] A fiber-reinforced composite material that is obtained by the fixing method according to [20] and is fixed to the member to be fixed.

  According to the present invention, a fiber reinforced composite material can be fixed to another member by a simple method using a fixing member such as a screw or a hook. Moreover, when fixing a fiber reinforced composite material to another member, it can suppress that a damage and a defect arise. Furthermore, according to the present invention, the fiber reinforced composite material has excellent strength in addition to having the above-mentioned aptitude at the time of fixation. For this reason, the fiber reinforced composite material of this invention is used suitably as a component of all industrial products.

FIG. 1 is a plan view and a cross-sectional view showing one embodiment of the fiber-reinforced composite material of the present invention. FIG. 2 is a plan view showing another embodiment of the fiber-reinforced composite material of the present invention. FIG. 3 is an enlarged cross-sectional view showing an embodiment of a low density region included in the fiber-reinforced composite material of the present invention. FIG. 4 is a perspective view showing a state in which the fiber-reinforced composite material of the present invention and the fixing target member are fixed. FIG. 5 is a plan view showing the arrangement of holes in the aluminum plate used in the example.

  Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Fiber reinforced composite material)
The present invention relates to a fiber reinforced composite material including a reinforced fiber and a thermoplastic resin, and relates to a fiber reinforced composite material having a low density region and a high density region. Here, if the density of the low density region is P and the density of the high density region is Q, then 1.5P <Q. Moreover, the ratio for which a low density area accounts is 0.001 to 15% with respect to the whole area of a fiber reinforced composite material.
The density means a value obtained by dividing the mass of a certain region by the volume of the region, and the low density region means a region whose density is 10% or more lower than the average density. On the other hand, the high density region refers to a region other than the low density region. In the present invention, the density (P) of the low density region and the density (Q) of the high density region have a relationship of 1.5P <Q.

The low density area | region of the fiber reinforced composite material of this invention can become an area | region for penetrating a fixing member. Thus, by setting the low density region as the fixed region, the fiber-reinforced composite material can be fixed to another member (fixed target member) by a simple method such as screwing.
Moreover, the area of a low density area | region is 0.001 to 15% with respect to the total area of a fiber reinforced composite material, and the low density area | region is provided locally and limitedly. For this reason, the fiber reinforced composite material of this invention can exhibit sufficient intensity | strength. In addition, the fiber-reinforced composite material of the present invention is not damaged even when the fiber-reinforced composite material is fixed to the fixing target member using the fixing member. This is considered to be because the voids included in the low density region absorb the penetration volume of the fixing member, and prevent the breakage and crack progress due to penetration. In addition, the low density region can be appropriately deformed to increase the effective contact area and disperse the stress from the fixture.
Usually, in a fiber reinforced composite material having sufficient strength, when the fixing member is penetrated, stress is concentrated locally in the high density region, and cracks are often generated due to vibration or the like. However, in the present invention, since the low density region is locally and limitedly provided, it is possible to suppress the occurrence of breakage when penetrating the fixing member. Moreover, in this invention, the handleability at the time of fixing using a fixing member is favorable, and the fiber reinforced composite material and fixing object member of this invention can be fixed easily.

  In the high-density region included in the fiber-reinforced composite material of the present invention, at least a part of the thermoplastic resin is present in a dissolved and solidified state. In the high density region, the amount of air contained between the fibers, that is, the air gap is reduced, and each fiber is firmly bonded. As described above, the strength of the fiber-reinforced composite material is increased at a portion having fibers that are firmly bonded.

A higher density in the high-density region is preferable because the strength of the fiber-reinforced composite material can be increased. The density of the high density region is preferably 1.0~1.8g / cm ^3, more preferably ^{1.2~1.8g / cm 3, 1.3~1.8g / cm} 3 More preferably. The density of the high density region is preferably 1.0 to 1.5 g / cm ³ and more preferably 1.2 to 1.5 g / cm ³ when carbon fiber is the main reinforcing fiber. Preferably, it is 1.3-1.5 g / cm < ³ >. By setting the density of the high-density region within the above range, the strength of the fiber-reinforced composite material can be increased and the durability can be increased.

On the other hand, in the low density region, the amount of air contained between the fibers, that is, the voids is larger than in the high density region. Density of the low density regions is preferably 0.1~1.3g / cm ^3, more preferably ^{0.2~1.0g / cm 3, 0.2~0.8g / cm} 3 More preferably. By setting the density of the low density region to be equal to or lower than the above upper limit value, it is possible to effectively suppress the occurrence of cracks due to the penetration of the fixing member. In addition, by setting the density of the low density region to be equal to or higher than the above lower limit value, the reinforcing fiber and the fibrous thermoplastic resin contained in the low density region are prevented from scattering or dropping off from the fiber reinforced composite material. be able to. Further, by setting the density of the low density region to be equal to or higher than the above lower limit value, the strength around the fixing member can be maintained at a certain level or more when the fixing member is penetrated, and the fixing member is held in a stable state. It becomes possible.

  The area of the low density region may be 0.001 to 15% with respect to the total area of the fiber-reinforced composite material, preferably 0.001 to 10%, and preferably 0.001 to 8%. More preferably, it is 0.001 to 5%. The lower limit can be, for example, 0.1% or more or 1% or more with respect to the total area of the fiber-reinforced composite material. The lower limit value should be equal to or greater than the value obtained by dividing the total cross-sectional area of the fixing member penetrating the fiber reinforced composite material by the total area of the fiber reinforced composite material and multiplying by 100 (this is referred to as the fixing member penetration area ratio). Can do. Moreover, the preferable range of a lower limit and an upper limit can also be prescribed | regulated by the magnification with respect to a fixed member penetration area rate, for example, 1-4 times of a fixed member penetration area rate, Preferably it is 1-3 times, More preferably It can be defined as 1.05 to 2 times, more preferably 1.05 to 1.5 times. The area and area ratio of the low-density region of the fiber-reinforced composite material of the present invention take into account the total area of the fiber-reinforced composite material, the cross-sectional area through which the fixing member to penetrate penetrates the fiber-reinforced composite material, and the number of solids to penetrate. Is preferably determined.

In the fiber reinforced composite material of the present invention, the region other than the low density region is a high density region. That is, the area of the high-density region may be 85 to 99.99%, preferably 90 to 99.99%, and 92 to 99.99% with respect to the total area of the fiber-reinforced composite material. It is more preferable that it is 95 to 99.99%. The lower limit value can be, for example, 99.9% or less or 99% or less with respect to the total area of the fiber-reinforced composite material.
By setting the ratio of the high density region and the low density region within the above range, the fiber reinforced composite material can exhibit sufficient strength, and in addition, the fiber reinforced composite material can be fixed using a fixing member. The damage etc. at the time of fixing to are suppressed.

  FIG. 1 is a view showing an embodiment of the fiber-reinforced composite material 10 of the present invention. Fig.1 (a) has shown the top view of the fiber reinforced composite material 10 of this invention, FIG.1 (b) and (c) have shown sectional drawing of the fiber reinforced composite material 10 of this invention. As shown in FIG. 1A, the fiber reinforced composite material 10 has a low density region 12 and a high density region 14. As shown in FIG. 1 (a), the low-density region 12 is 0.001 to 15% with respect to the total area of the fiber-reinforced composite material 10, and the high-density region 14 is provided as wide as possible, thereby increasing the strength of the fiber. It can be a reinforced composite material.

  In the present invention, the low density region 12 may be formed so that the thickness of the low density region 12 is larger than the thickness of the high density region 14 as shown in FIG. Further, as shown in FIG. 1C, the low-density region 12 and the high-density region 14 may be formed to have substantially the same thickness, and the thickness of the low-density region becomes thinner than the thickness of the high-density region. You may shape | mold. Among these, from the viewpoint of ease of molding, it is preferable to mold so that the thickness of the low density region 12 is larger than the thickness of the high density region 14 as shown in FIG.

  When the thickness of the low density region 12 is thicker than that of the high density region 14 as shown in FIG. 1B, the average film thickness of the high density region 14 is preferably 0.5 to 50 mm. It is more preferably 0 to 30 mm, and further preferably 1.0 to 10 mm. Moreover, it is preferable that the average film thickness of the low density area | region 12 is 1.5-150 mm, It is more preferable that it is 2.0-90 mm, It is further more preferable that it is 2.0-30 mm.

  When the average film thickness of the low density region 12 is thicker than the average film thickness of the high density region 14 as shown in FIG. 1B, an uneven structure is formed on the surface of the fiber reinforced composite material. . In the present invention, the highest point of the convex portion of such a concavo-convex structure belongs to the low density region, and the deepest point of the concave portion belongs to the high density region. As shown in FIG. 1B, the low density region 12 constitutes a central convex portion, and the high density region 14 constitutes an end concave portion.

  In addition, the convex part of the concavo-convex structure may be subjected to cutting, and by cutting off so that the convex part is flat, the fiber reinforced composite in which the average film thickness of the low density region 12 and the high density region 14 is substantially the same. A material can be obtained. Further, a fiber-reinforced composite material in which the average film thickness of the low density region 12 is thinner than the average film thickness of the high density region 14 may be formed by further cutting a portion corresponding to the convex portion of the concavo-convex structure.

As shown in FIG. 1, the low density region 12 is preferably formed as a discontinuous region in the fiber reinforced composite. In this case, the low density region 12 is intermittently provided on the surface of the fiber reinforced composite material 10. When the low density area | region 12 is provided as a discontinuous area | region in the fiber reinforced composite material, it is preferable that the low density area | region 12 is provided with two or more in the fiber reinforced composite material. The number of low-density regions is preferably determined as appropriate in consideration of the size and shape of the fiber reinforced composite material, the shape and material of the object to be fixed, the purpose of use and environment of use of the fixed object, and the like. Usually, it is preferable that the number per unit area is within a certain range, or the number per unit outer peripheral length is within a certain range. For example, the number of low density regions is preferably 2 to 200 per 1 m ^{2 of} fiber reinforced composite material, more preferably 4 to 100, and even more preferably 8 to 60. From another viewpoint, the number of low density regions is preferably 0.5 to 50, more preferably 1 to 25, per 1 m of the outer peripheral length of the fiber reinforced composite material. More preferably, the number is -15.

  The position where the low density region is provided is not particularly limited as long as it is a suitable position as a fixing portion that penetrates the fixing member and is fixed to the fixing target member. For example, the low density region may be provided at the four corners of the fiber reinforced composite material or may be provided at the central region. In addition, when fixing the whole surface of a fiber reinforced composite material to a fixing object member, it is preferable to provide a low density area | region in at least four corners of a fiber reinforced composite material. Thereby, it becomes possible to firmly fix the fiber-reinforced composite material to the fixing target member.

  The shape of the low density region is not particularly limited, but is preferably circular as shown in FIG. Moreover, it may be a substantially rectangular shape as shown in FIG. 2 (a), and in this case, a rectangular shape with a rounded arc is preferred. Furthermore, as shown in FIG. 2B, the shape of the low density region may be a dogleg shape corresponding to the four corners. Also in this case, it is preferable that the corners of the low density region have a circular arc shape.

  The low density area | region 12 may be provided in the outer peripheral area | region, as FIG.2 (c) shows. As shown in FIG. 2C, the low density region 12 is preferably provided at a plurality of locations in the outer peripheral region in a discontinuous manner. In addition, the outer peripheral area | region of the fiber reinforced composite material 10 is an area | region including the outer periphery of the fiber reinforced composite material 10, Comprising: The area | region formed so that it may have a substantially constant width along an outer periphery. Here, when the molding sheet 10 is rectangular, the constant width means a length of 1 to 20% of the entire length of one side of the quadrangle including the width. The shape of the low-density region in the outer peripheral region is not limited to the aspect of FIG. 2. For example, a plurality of low-density regions from the center toward the outer peripheral direction may be formed radially, or a plurality of low-density regions may be formed in the outer peripheral region. The region may be formed in a zigzag manner or may be formed randomly.

  As shown in FIG. 3, a cutout portion 13 may be formed in the low density region 12. The notch portion refers to a concave portion formed in the convex portion constituting the low density region 12. The cutout portion 13 is preferably formed in a region including the central portion of the low density region 12. Further, the shape of the cutout portion 13 may be circular, and can be various shapes such as a rectangle and a line. The area of the cutout portion 13 is preferably 1 to 10% of the surface area of the low density region 12, and more preferably 1 to 5%. Such a cut-out portion 13 serves to facilitate positioning of a fixing member such as a screw or a hook. That is, by fitting the tip of a fixing member such as a screw or a hook into the notch 13, it is possible to prevent the tip of the fixing member from causing an unintended side slip at the time of fixing or preventing the fixing member from penetrating in an unintended direction. it can.

A through hole may be provided in the low density region of the fiber reinforced composite material of the present invention. Here, the through hole is a hole formed by a fixing member for fixing the fiber reinforced composite material to the fixing target member penetrating through the low density region. That is, the present invention may relate to a fiber reinforced composite material in which a fixing member is penetrated in a low density region.
In this case, the total area of the low-density region and the through-hole of the fiber reinforced composite material is preferably more than 1 and 4 or less, more preferably 1.05 to 4 times the area of the through-hole. Preferably, it is 1.2 to 3.5 times.

(Reinforced fiber)
The reinforcing fiber used in the present invention functions to increase the strength of the fiber-reinforced composite material. The reinforcing fibers are preferably composed of fibers having a fiber diameter of 20 μm or less, a glass transition temperature of 210 ° C. or more, and an elastic modulus of 50 GPa or more.

  The fiber diameter of the reinforcing fiber is preferably 0.1 to 18 μm, more preferably 2 to 16 μm, and further preferably 3 to 12 μm. By setting the fiber diameter of the reinforcing fiber within the above range, the uniformity of the mixture with the thermoplastic resin fiber can be improved, and the strength of the fiber-reinforced composite material can be increased. Moreover, it is preferable from the viewpoint of preventing the reinforcing fiber from being taken into the human body during the manufacturing process or during use.

  Moreover, it is preferable that the fiber length of a reinforced fiber is 3-30 mm, It is more preferable that it is 4-28 mm, It is further more preferable that it is 5-25 mm. By making the fiber length of the reinforcing fibers within the above range, the dispersibility of the fibers can be made uniform. In addition, the fiber diameter and fiber length of a reinforced fiber may be single, and you may blend and use the thing of a different fiber diameter and fiber length.

  The glass transition temperature of the reinforcing fiber is preferably 210 ° C or higher, more preferably 220 ° C or higher, and further preferably 230 ° C or higher. In addition, it is not necessary to provide the upper limit value of the glass transition temperature of the reinforcing fiber. By setting the glass transition temperature of the reinforcing fiber in the above range, even when the thermoplastic resin described later is heated at a temperature at which the thermoplastic resin melts, the reinforcing fiber does not melt and functions to reinforce the fiber-reinforced composite material. Can be fully demonstrated.

  The tensile elastic modulus of the reinforcing fiber is preferably 50 GPa or more, more preferably 70 GPa or more, and further preferably 80 GPa or more. Thus, by making the elastic modulus of the reinforcing fiber high, a fiber-reinforced composite material having a high elastic modulus can be obtained. In general, a fiber reinforced composite material having a high elastic modulus is often cracked when the fixing member is penetrated, but in the present invention, a low density region is provided in the fiber reinforced composite material, and the fixing member is penetrated into the low density region. It is possible to avoid the occurrence of defects such as cracks in the fiber reinforced composite material.

Examples of reinforcing fibers that can be used in the present invention include aramid fibers, glass fibers, carbon fibers, ceramic fibers, rock wool fibers, and basalt fibers. Among them, it is preferable to use glass fiber or carbon fiber from the balance of price, strength, and elastic modulus. Moreover, an aramid fiber is preferable from the point of impact resistance (toughness).
As the carbon fibers, carbon fibers such as polyacrylonitrile (PAN), petroleum / coal pitch, rayon, and lignin can be used. Among these, it is preferable to use polyacrylonitrile (PAN) -based carbon fibers from the viewpoint of productivity and mechanical properties on an industrial scale.
There are types of glass fibers such as E glass and S glass, but the types are not particularly limited. It is efficient to use E glass which is generally easily available.

  Further, as the reinforcing fiber, only one type of the above-described fibers may be used, but two or more types of fibers may be used in combination. For example, glass fibers and carbon fibers may be mixed and used, or glass fibers and ceramic fibers may be mixed and used. Furthermore, in addition to the fibers described above, metal fibers or the like may be mixed and used.

(Thermoplastic resin)
The thermoplastic resin used in the fiber-reinforced composite material of the present invention forms a binding point at the intersection of the matrix or the reinforcing fiber during the heat and pressure treatment. The thermoplastic resin is in a fibrous form prior to heat and pressure molding, and melts into a matrix by performing heat and pressure treatment. By using a fibrous thermoplastic resin in this way, the heat and pressure molding time can be shortened, and a fiber-reinforced composite material can be efficiently molded.

  The thermoplastic resin may be a fiber called a so-called super engineering plastic. Super engineering plastics are thermoplastic resins having excellent heat resistance and flame retardancy.

  As thermoplastic resins, polypropylene (PP), polycarbonate (PC), nylon 6, nylon 66, aromatic polyamide, polyethylene terephthalate (PET), polyetheretherketone (PEEK), polyamideimide (PAI), polyphenylene sulfide (PPS) ), Polyether imide (PEI), polyether ketone ketone (PEKK), and the like. Among these, it is preferable to use polycarbonate, polyetherimide, or nylon in order to obtain a fiber-reinforced composite plastic molded article having good fiber dispersibility and high strength. In order to obtain a fiber reinforced composite material having excellent chemical resistance, it is preferable to use polypropylene or polyphenylene sulfide (PPS).

In order to obtain a flame-retardant fiber-reinforced composite material, the thermoplastic resin fiber preferably has a LOI value (limit oxygen index) of 24 or more in the fiber state, and more preferably 30 or more. Here, the “LOI value (limit oxygen index)” represents the oxygen concentration necessary to continue combustion, and is a numerical value measured by the method described in JIS K7201. That is, when the limiting oxygen index is 20 or less, it indicates that combustion is performed in normal air. The LOI value (limit oxygen index) is preferably 24 or more, more preferably 30 or more, further preferably 35 or more, and particularly preferably 40 or more. By setting the LOI value (limit oxygen index) within the above range, the fiber reinforced composite material can exhibit extremely high flame retardancy.
Moreover, it is preferable that the amount of smoke during 20-minute combustion measured by the method described in ASTM E-662 of thermoplastic fibers is around 30 ds, and a sheet for fiber-reinforced plastic molded body with a very small amount of smoke can be obtained. it can.

It is preferable that the glass transition temperature of a thermoplastic resin is 120 degreeC or more from the heat resistance of a fiber reinforced composite material. The thermoplastic fiber is required to be sufficiently fluid under a temperature condition of 200 ° C. to 400 ° C. when the fiber reinforced composite material is formed. Even if the glass transition temperature of the thermoplastic resin is less than 120 ° C., it is used for applications where heat resistance is not required, or the resin has a high glass deflection temperature but a high resin deflection temperature (for example, polypropylene, nylon, etc.) , Polyphenylene sulfide resin, etc.) can be used.
In addition, the glass transition temperature of a thermoplastic resin needs to be lower than the glass transition temperature of the reinforced fiber mentioned above. Thereby, when the fiber-reinforced composite material is heated and pressurized, only the thermoplastic resin in the high-density region can be melted, and the strength of the fiber-reinforced composite material can be increased.

  It is preferable to use an amorphous thermoplastic resin because it is excellent in impact resistance and stable in quality regardless of molding conditions (cooling rate). As the amorphous thermoplastic resin, polycarbonate, polyetherimide and the like can be suitably used.

  In order to form a fiber reinforced composite material in a short time, it is necessary that the thermoplastic resin fiber used is rapidly melted at a high temperature. For this purpose, the fiber diameter of the thermoplastic resin fiber must be small. preferable. This is because when the fiber diameter is small, the number of contact points between the fibers increases, the contact area between the fibers increases, and the heat conduction becomes good. Moreover, since the heat capacity of the fiber is reduced, the amount of heat necessary for melting is reduced. The fiber diameter of the thermoplastic resin fiber used is preferably 30 μm or less, and more preferably 20 μm or less.

  Although the fiber length of a thermoplastic resin fiber is not specifically limited, It is preferable that it is 3-30 mm, It is more preferable that it is 4-28 mm, It is further more preferable that it is 5-25 mm. By setting the fiber length of the thermoplastic resin fiber within the above range, the reinforcing fiber and the thermoplastic resin fiber are uniformly mixed, so that the strength of the fiber-reinforced composite material can be increased. The fiber diameter and fiber length of the thermoplastic resin fiber may be single, or those having different fiber diameters and fiber lengths may be blended and used.

  The fiber diameter of the thermoplastic resin fiber is preferably 4 times or less of the fiber diameter of the reinforcing fiber, more preferably 3 times or less, and the fiber diameter of the thermoplastic resin fiber and the fiber diameter of the reinforcing fiber are approximately the same. More preferably it is. Thereby, the reinforcing fiber and the thermoplastic resin fiber are easily mixed uniformly. Thereby, a high-strength fiber reinforced composite material can be obtained.

  The mass ratio of the reinforcing fiber and the thermoplastic resin contained in the fiber-reinforced composite material is preferably substantially constant in the entire region of the fiber-reinforced composite material. That is, in the present invention, a fiber-reinforced composite material having a low density region locally can be obtained without changing the content ratio of the reinforcing fibers and the thermoplastic resin in the sheet. For this reason, the manufacturing process of a fiber reinforced composite material can be simplified and production cost can be suppressed. In addition, that the content ratio of the reinforcing fiber and the thermoplastic resin is substantially constant indicates that the content ratio may vary by ± 5%.

The content ratio of the reinforcing fiber and the thermoplastic resin contained in the fiber reinforced composite material is preferably 0.2: 1 to 10: 1, more preferably 0.5: 1 to 5: 1, More preferably, it is 0.7: 1-3: 1. By setting the content ratio of the reinforcing fibers and the thermoplastic resin within the above range, the strength of the fiber reinforced composite material can be increased, and the density of the low density region can be set to a preferable range.
In general, when a super engineering plastic resin is used as a thermoplastic resin, the super engineering plastic resin has a high melt viscosity. Therefore, it is difficult to uniformly disperse the reinforcing fibers when a large amount of reinforcing fibers are blended in a method such as injection molding. There is a limit to the blending ratio of reinforcing fibers. However, in the fiber-reinforced composite material of the present invention, the ratio of the reinforcing fiber and the matrix resin fiber can be set relatively freely according to the required strength.

(Binder component)
The fiber reinforced composite material of the present invention preferably further contains a binder component. The binder component is preferably contained in an amount of 0.1 to 10% by mass with respect to the total mass of the fiber-reinforced composite material, more preferably 0.3 to 10% by mass, and 0.4 to It is more preferable that it is 9 mass%, and it is especially preferable that it is 0.5-8 mass%. By making the content rate of a binder component in the said range, the intensity | strength in a manufacturing process can be raised and handling property can be improved. Note that as the amount of the binder component increases, both the surface strength and the interlayer strength increase, but conversely, the problem of odor during heat forming tends to occur. However, in the above range, there is hardly any odor problem, and a fiber-reinforced composite material that does not cause delamination even after repeated cutting steps can be obtained.

  As binder components, polyester resins such as polyethylene terephthalate and modified polyethylene terephthalate, which are generally used for nonwoven fabric production, acrylic resins, styrene- (meth) acrylate copolymer resins, urethane resins, PVA resins, and various starches , Cellulose derivative, sodium polyacrylate, polyacrylamide, polyvinylpyrrolidone, acrylamide-acrylic ester-methacrylic ester copolymer, styrene-maleic anhydride copolymer alkali salt, isobutylene-maleic anhydride copolymer alkali salt, A polyvinyl acetate resin, a styrene-butadiene copolymer, a vinyl chloride-vinyl acetate copolymer, an ethylene-vinyl acetate copolymer, a styrene-butadiene- (meth) acrylic acid ester copolymer, and the like can be used.

The binder component preferably contains a copolymer containing at least one of a repeating unit derived from a methyl (meth) acrylate-containing monomer and a repeating unit derived from an ethyl (meth) acrylate-containing monomer. Especially, it is preferable that a binder component contains the copolymer containing at least 1 among the repeating unit derived from a methyl methacrylate containing monomer and the repeating unit derived from an ethyl methacrylate containing monomer. These monomers may be copolymerized with other monomers such as styrene, vinyl acetate, acrylamide and the like.
In the present invention, “(meth) acrylate” means containing both “acrylate” and “methacrylate”, and “(meth) acrylic acid” means “acrylic acid” and “methacrylic acid”. Is meant to include both.

Furthermore, a polyester resin and a modified polyester resin are mentioned as a binder component preferable in the present invention. As the polyester resin, polyethylene terephthalate (PET) is particularly preferable. The modified polyester resin is not particularly limited as long as the melting point is lowered by modifying the polyester resin, but modified polyethylene terephthalate is preferable. As the modified polyethylene terephthalate, copolymerized polyethylene terephthalate (coPET) is preferable, and examples thereof include urethane-modified copolymerized polyethylene terephthalate. The polyester resin is preferably used because it is compatible with the thermoplastic fiber of the present invention at the time of heating and melting, so that it is difficult to impair the function of heat and resin even after cooling.
The copolymerized polyethylene terephthalate preferably has a melting point of 140 ° C. or lower, more preferably 120 ° C. or lower. Moreover, you may use the modified polyester resin as described in Japanese Patent Publication No. 1-30926. As a specific example of the modified polyester resin, a trade name “Melty 4000” (a fiber in which all fibers are copolymerized polyethylene terephthalate) manufactured by Unitika Ltd. is particularly preferable. As the core-sheath-structured binder fiber, trade name “Melty 4080” manufactured by Unitika Co., Ltd., trade name “N-720” manufactured by Kuraray Co., Ltd. and the like can be suitably used.

(Fiber-reinforced composite material manufacturing method)
The method for producing a fiber-reinforced composite material according to the present invention includes a step of mixing a reinforcing fiber and a thermoplastic resin fiber to produce a nonwoven fabric sheet by a dry nonwoven fabric method or a wet nonwoven fabric method, and a nonwoven fabric sheet made of glass of thermoplastic resin fiber. A step of heating and pressing at a temperature equal to or higher than the transition temperature. Furthermore, the step of heat-pressing includes a step of pressing a 0.001 to 15% region of the nonwoven fabric sheet at a pressure lower than the average pressure.

  In the process of producing a nonwoven fabric sheet, a dry nonwoven fabric method or a wet nonwoven fabric method is used. The dry nonwoven fabric method is a method in which chopped strands obtained by cutting reinforcing fibers and thermoplastic resin fibers into a certain length are dispersed in air and trapped in a net to form a web. The wet nonwoven fabric method is a method in which chopped strands in which reinforcing fibers and thermoplastic resin fibers are cut to a certain length are dispersed in a solvent, and then the solvent is removed to form a web. Among these, the airlaid method of the dry nonwoven fabric method is preferably used in that a bulky high basis weight sheet can be obtained. On the other hand, the wet nonwoven fabric method is suitable in that it is easy to obtain a uniform and wide sheet.

  In the nonwoven fabric sheet, there are voids in the sheet due to the thermoplastic resin and the reinforcing fibers crossing each other. For this reason, the nonwoven fabric sheet is different from the nonwoven fabric in which the resin is completely filled between the fibers formed by the melting method, solvent method, dry powder coating method, powder suspension method, resin film impregnation method, etc. It is supple and drapeable. As a result, the nonwoven sheet used in the production method of the present invention can be stored and transported in the form of winding, and can be heat-pressed after being placed along a curved mold. Are better. Further, when processed into a fiber reinforced composite material, it is possible to form a low density region and a high density region.

  When making a nonwoven fabric sheet contain a binder component, it can mix in the process of manufacturing a nonwoven fabric sheet. Alternatively, the binder component can be applied to the sheet by a spraying method, a coating method or an impregnation method after the nonwoven fabric sheet is formed. In addition, it is preferable that a binder component is contained so that it may concentrate on both surface layers of a nonwoven fabric sheet. Thereby, scattering, fluffing, and dropping off of the surface fibers can be suppressed, and a fiber-reinforced composite material having excellent handling properties can be obtained. Moreover, it is preferable that the binder is contained also in the inside (middle layer) of the nonwoven fabric of the sheet in order to maintain the interlayer strength of the sheet.

  The step of heat and pressure molding is a step of heat and pressure treatment at a temperature equal to or higher than the glass transition temperature of the thermoplastic resin fiber, and a step of applying pressure while heating to a temperature at which at least a part of the thermoplastic resin flows. is there. The heating temperature is preferably a temperature range in which the thermoplastic resin fibers flow and the reinforcing fibers do not melt. By setting it as such a temperature range, the intensity | strength of a fiber reinforced composite material can be raised. Specifically, when the glass transition temperature of the thermoplastic resin is 100 ° C. or higher, the specific heating temperature is preferably Tg to Tg + 100 ° C., and preferably Tg to Tg + 50 ° C. when the glass transition temperature is Tg. More preferred.

  The step of heat and pressure forming includes a step of pressing a 0.001 to 15% region of the nonwoven fabric sheet at a pressure lower than the average pressure. That is, in the heating and pressing step, a distribution is given to the pressure applied to the nonwoven fabric sheet. Thus, the area | region pressurized by low pressure rather than an average pressure turns into a low density area | region, and an area | region other than that turns into a high density area | region. The average pressure applied in the heating and pressing step is preferably 2 to 20 MPa, and a pressure of 0 to 4 MPa is preferably applied to the 0.001 to 15% region of the nonwoven fabric sheet. Note that no pressure may be applied to the low density region, and the pressure treatment may be performed so that a pressure lower than the average pressure is applied.

  The rate of temperature rise until reaching the desired holding temperature is preferably 3 to 20 ° C./min. The holding time at the desired hot press temperature is 1 to 30 minutes, and then the temperature at which the fiber-reinforced composite material is taken out (200 ° C. It is preferable to set it as a cooling rate of 3-20 degree-C / min, maintaining a pressure until below. Further, although the production efficiency is slightly lowered, it is also preferable from the viewpoint of improving the strength to cool slowly by air cooling from the holding temperature of the hot press to the glass transition temperature of the thermoplastic resin at 0.1 to 3 ° C./min. It is also possible to perform hot press molding using rapid heating and rapid cooling (heat and cool) molding, in which case the temperature rise and cooling rate are 30 to 500 ° C./min, respectively. Furthermore, when using an infrared heater, it can be heated at 150 to 600 ° C., preferably 200 to 500 ° C. for 1 to 30 minutes, and then molded at an average pressure of 30 to 150 MPa. In this case, it is preferable that a pressure of 0.1 to 20 MPa is applied to the 0.001 to 15% region of the nonwoven fabric sheet.

In order to obtain a fiber-reinforced composite material having a low density and a high density region in the process of heat and pressure molding, a mold having a concave portion at a position corresponding to a region where the low density region is to be obtained is pressed against the nonwoven fabric sheet. It is preferable to perform press working. Specifically, the heat and pressure treatment can be performed by pressing a mold having a preheated recess against the nonwoven fabric sheet. The concave portion of the mold means a portion where a space can be formed between the mold and the nonwoven fabric sheet when the mold is brought into contact with the nonwoven fabric sheet, and a low density region is formed at a portion corresponding to the concave portion. The Rukoto. On the other hand, in the area | region of the metal mold | die in which the recessed part is not formed, almost no space is formed between a metal mold | die and a nonwoven fabric sheet, A high pressure is provided and a high-density area | region will be formed. In addition, the area of the recessed part of the metal mold | die used for the manufacturing method of this invention is 0.001 to 15% with respect to the area of the whole metal mold | die. Here, the area of the recess means the projected area of the recess.
In the present invention, the shape of the concave portion of the mold can be variously changed, so that the shape of the low density region can be freely changed, and the area of the low density region is appropriately within the range of 0.001 to 15%. Can be changed.

  In the production method of the present invention, one non-woven fabric sheet may be subjected to heat and pressure treatment, and a laminate obtained by laminating a plurality of non-woven fabric sheets so as to have a desired thickness is subjected to heat and pressure treatment. Also good. By processing a laminate of multiple non-woven sheets, it is possible to effectively form a low density region, and defects such as cracks occur when the fixing member penetrates into the low density region of the fiber reinforced composite material. Can be prevented. Furthermore, the strength of the fiber-reinforced composite material itself can be increased by processing a laminate in which a plurality of nonwoven fabric sheets are laminated.

  In addition, in order to obtain a fiber reinforced composite material having a low density and a high density region in the process of heat and pressure molding, a low density region is obtained when heat and pressure treatment is performed on a laminate in which a plurality of nonwoven fabric sheets are laminated. You may heat-press-process, after reducing the number of lamination | stacking of the nonwoven fabric sheet of the position corresponding to the site | part which is going to be reduced. The area where the number of stacked layers is reduced becomes a low density area due to a small amount of material in the area. On the other hand, in a region where the number of stacked layers is not reduced, a high-density region is formed.

(Fixing method)
The present invention relates to a fixing method for fixing a fiber-reinforced composite material to a fixing target member using a fixing member. In the fixing method of the present invention, the fixing member is passed through the low density region of the fiber reinforced composite material, and the fixing target member and the fiber reinforced composite material are fixed.

  FIG. 4 is a perspective view illustrating a state in which the fiber-reinforced composite material and the fixing target member are fixed. As shown in FIG. 4, the fixing member 20 penetrates the low density region 12 of the fiber reinforced composite material 10. Furthermore, by moving the fiber reinforced composite material 10 and the fixing member 20 in the direction of the arrow in FIG. 4, the fixing member 20 penetrates the fixing target member 30, and the fiber reinforced composite material 10 and the fixing target member are fixed. .

  Examples of the fixing member include general members used as screws and scissors. Specific examples include nails, wood screws, tapping screws, drill screws, nutters, rivets, blind rivets and the like.

  The area of the low density region that penetrates the fixing member is greater than 1 and less than or equal to 4 times the area of the through hole formed when the fixing member is penetrated through the low density region of the fiber reinforced composite material. Is more preferable, 1.05 to 4 times is more preferable, and 1.2 to 3.5 times is more preferable. When the through holes are formed in the low density region, the area of the low density region means the total area of the low density region and the area of the through holes.

  Further, the area of the low density region through which the fixing member penetrates may be equal to or smaller than the area of the through hole formed when the fixing member is passed through the low density region of the fiber reinforced composite material. Specifically, the area of the low density region that penetrates the fixing member is 0.5 to 1 times the area of the through hole formed when the fixing member is penetrated through the low density region of the fiber-reinforced composite material. It may be. When the area of the low density region is equal to or smaller than the area of the through hole, the through hole is also formed in the high density region around the low density region. In such a case, the low-density region may not exist in the fiber-reinforced composite material after passing through the fixing member.

When fixing a fiber reinforced composite material to a fixing member, it is preferable to employ a method of fixing directly without opening a pilot hole from the viewpoint of efficiency. That is, the fixing method of the present invention preferably includes a step of penetrating the fixing member while perforating the low-density region of the fiber-reinforced composite material.
On the other hand, a pilot hole may be provided in advance in the fiber reinforced composite material. The fixing method of the present invention may include a step of passing the fixing member through a prepared pilot hole.

  The present invention also relates to a fiber reinforced composite material obtained by the fixing method as described above and fixed to a member to be fixed.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

(Example 1)
40 parts of glass fiber having a fiber diameter of 6 μm and a fiber length of 18 mm (glass transition temperature of 300 ° C. or higher, elastic modulus of 80 GPa), 15 μm of polyetherimide (PEI) fiber (Fiber Innovation Technology, fiber length of 12 mm) ) 50 parts, 10 parts of core-sheath binder fiber (Kuraray N-720) using modified PET (melting point: 110 ° C.) for the sheath and PET fiber for the core were put into water. The amount of water was 200 times the weight of the input fibers (fiber slurry concentration 0.5%).
To this slurry, “Emanon 3199” (trade name, Kao Co., Ltd.) as a dispersant was added to 1 part by mass with respect to 100 parts by mass of the fiber and stirred to obtain a fiber slurry in which the fibers were uniformly dispersed in water. Prepared.
A wet web was formed from the fiber slurry by a wet papermaking method, followed by heat drying at 180 ° C. to prepare a nonwoven fabric having a weight per unit area of 450 g / m ² with the binder amount shown in Table 1.
After laminating 6 sheets of this 30 cm square, a 30 mm square aluminum plate having a diameter of 5 mm and a depth of 4 mm has four corners and the center of each side as shown in FIG. 5 (a = 28.5 cm, b = 30 cm) is placed on one side and a 30 cm square aluminum plate is placed on the other side, heated and pressurized at a pressure of 2 MPa and a temperature of 280 ° C., and then cooled. A fiber reinforced composite material was prepared.
The density of the high-density region is 1.3 g / cm ^3, the density of the low density regions was 0.43 g / cm ^3. The total area of the low-density region is 1.55 cm ^2, was 0.17% of the total area of the fiber reinforced composite material (900 cm ^2). In addition, the thickness of the high density region was 2 mm, and the thickness of the low density region was 6 mm.
Eight low-density regions of the fiber-reinforced composite material are formed by stacking 30-cm square fiber-reinforced composite materials with this low-density region on an aluminum frame with an outer size of 30-cm square made of 1.5-cm square aluminum pipes. A tapping screw having a diameter of 3 mm was screwed in and fixed to the aluminum frame.

(Example 2) A nonwoven fabric sheet was prepared in the same manner as in Example 1.
Three sheets of this nonwoven fabric sheet were laminated, 3 sheets of 30 cm square, 3 sheets of 30 cm square sheets with 4 holes and 8 holes of 5 mm in diameter arranged in the center of each side, and a total of 6 sheets. Thereafter, 30 cm square aluminum plates were applied to both sides, and after heating and pressing at a pressure of 2 MPa and a temperature of 280 ° C., cooling was performed to prepare a fiber-reinforced composite material.
The density of the high density region was 1.3 g / cm ³ , and the density of the low density region was 0.65 g / cm ³ . The total area of the low-density region is 1.55 cm ^2, was 0.17% of the total area of the fiber reinforced composite material (900 cm ^2). In addition, the thickness of the high density region was 2 mm, and the thickness of the low density region was 4 mm.
This fiber reinforced composite material was fixed to an aluminum frame in the same manner as in Example 1.

(Example 3)
A fiber-reinforced composite material fixed to an aluminum frame was prepared in the same manner as in Example 1 except that the polyetherimide fiber of Example 1 was replaced with polycarbonate fiber.

Example 4
40 parts of carbon fiber (HT110 manufactured by Toho Tenax) (glass transition temperature of 300 ° C. or higher) having a fiber length of 6 mm, a fiber diameter of 7 μm, and an elastic modulus of 240 GPa, and a polyetherimide (PEI) fiber having a fiber diameter of 15 μm (manufactured by Fiber Innovation Technology), fiber 10 parts of core-sheath binder fiber (Kuraray N-720) using modified PET (melting point: 110 ° C.) for the sheath part and PET fiber for the core part were put into water. The amount of water was 200 times the weight of the input fibers (fiber slurry concentration 0.5%).
To this slurry, “Emanon 3199” (trade name, Kao Co., Ltd.) as a dispersant was added to 1 part by mass with respect to 100 parts by mass of the fiber and stirred to obtain a fiber slurry in which the fibers were uniformly dispersed in water. Prepared.
A wet web was formed from the fiber slurry by a wet papermaking method, followed by heat drying at 180 ° C. to prepare a nonwoven fabric having a weight per unit area of 450 g / m ² with the binder amount shown in Table 1.
After laminating 6 sheets of this non-woven fabric in 30 cm square, 8 holes with a diameter of 5 mm and a depth of 2 mm were drilled in 4 corners and the center of each side on a 30 cm square aluminum plate in the arrangement as shown in FIG. An object was placed on one side, and a 30 cm square aluminum plate was placed on the other side. After heat and pressure treatment at a pressure of 10 MPa and a temperature of 280 ° C., the product was cooled to prepare a fiber-reinforced composite material.
The density of the high density region was 1.5 g / cm ³ and the density of the low density region was 0.75 g / cm ³ . The total area of the low-density region is 1.55 cm ^2, was 0.17% of the total area of the fiber reinforced composite material (900 cm ^2). In addition, the thickness of the high density region was 2 mm, and the thickness of the low density region was 6 mm.
This low-density region, 30cm square fiber reinforced composite material, is stacked on an outer 30cm square aluminum frame made of 1.5cm square aluminum pipe, and 8 low density regions of fiber reinforced composite material. A tapping screw having a diameter of 3 mm was screwed in and fixed to the aluminum frame.

(Comparative Example 1)
In place of the 30 cm square aluminum plate of Example 1 having 8 holes with a diameter of 5 mm and a depth of 4 mm in the four corners and the center of each side, as shown in FIG. 5, a 30 cm square aluminum plate without holes. A fiber reinforced composite material having no low density region was prepared in the same manner as in Example 1 except that it was used, and a tapping screw was screwed into the same position as the tapping screw in Example 1 to fix it to an aluminum frame. .

(Comparative Example 2)
In place of the 30 cm square aluminum plate of Example 1 having 8 holes with a diameter of 5 mm and a depth of 4 mm in the four corners and the center of each side, as shown in FIG. 5, a 30 cm square aluminum plate without holes. A fiber reinforced composite material having a thickness of 4 mm and a low density (0.65 g / cm ³ ) as a whole was prepared in the same manner as in Comparative Example 1 except that the pressure was changed to 0.5 MPa. A tapping screw was screwed into the same position as the screw and fixed to the aluminum frame.

(Comparative Example 3)
In place of the 30 cm square aluminum plate of Example 3 with 8 holes with a diameter of 5 mm and a depth of 4 mm in the four corners and the center of each side in the arrangement as shown in FIG. 5, a 30 cm square aluminum plate without holes. A fiber reinforced composite material having no low density region was prepared in the same manner as in Example 1 except that it was used, and a tapping screw was screwed into the same position as the tapping screw in Example 1 to fix it to an aluminum frame. .

(Comparative Example 4)
In place of the 30 cm square aluminum plate of Example 4 with 8 holes with a diameter of 5 mm and a depth of 4 mm in the four corners and the center of each side, as shown in FIG. 5, a 30 cm square aluminum plate without holes. A fiber reinforced composite material (density 1.5 g / cm ³ ) without a low density region was produced in the same manner as in Example 4 except that it was used, and the tapping screw was screwed into the same position as the tapping screw of Example 1. What was fixed to the aluminum frame was produced.

(Comparative Example 5)
In place of the 30 cm square aluminum plate of Example 4 with 8 holes with a diameter of 5 mm and a depth of 4 mm in the four corners and the center of each side, as shown in FIG. 5, the diameter is 5 mm on the 30 cm square aluminum plate. The density of the high-density region is 1.5 g, as in Example 4, except that an aluminum plate having 8 holes of 0.7 mm in depth arranged at the four corners and the center of each side with 8 holes arranged as shown in FIG. 5 is used. / cm ^3, and that the density of the lower density region to produce a fiber-reinforced composite material is 1.1 g / cm ^3, was fixed to an aluminum frame is screwed tapping screw in the same position as tapping screw of example 1 Was made.

(Evaluation method)
<Damage when fixed>
A fixed part, that is, a part into which the tapping screw was screwed, was visually observed through a magnifying glass 10 times to determine whether there was crack breakage, and evaluated according to the following criteria.
○: The fiber reinforced composite material was not damaged.
Δ: Cracks occurred in the fiber reinforced composite material.
X: The fiber reinforced composite material was cracked.

<Strength>
Place the fiber reinforced composite material fixed on the aluminum frame horizontally on the concrete floor so that the aluminum frame is on the bottom, and let the steel ball of 3cm diameter fall naturally from the height 30cm vertically above the center of the frame, crack, Whether or not there was any damage was visually observed using a 10-fold magnifier and evaluated according to the following criteria.
○: No crack breakage was observed.
(Triangle | delta): The crack damage was recognized by the fixed part periphery.
X: Crack breakage was observed in the fiber reinforced composite material.

  When the density of the low-density region is P and the density of the high-density region is Q, the ratio of the low-density region satisfies the relationship of 1.5P <Q and the low-density region occupies the total area of the fiber-reinforced composite material. It was confirmed that the fiber reinforced composite materials of the examples of 0.001 to 15% did not break at the time of fixation and had sufficient strength. On the other hand, even if it has the fiber reinforced composite material of Comparative Examples 1 to 4 that does not have two regions, a high density region and a low density region, or two regions, the relationship of 1.5P <Q is not satisfied. The fiber-reinforced composite material of Comparative Example 5 has problems such as damage during fixation and insufficient strength.

  According to the present invention, a fiber reinforced composite material can be fixed to another member by a simple method using a fixing member such as a screw or a hook. Moreover, when fixing a fiber reinforced composite material to another member, it can suppress that a damage and a defect arise. Furthermore, according to the present invention, the fiber reinforced composite material has excellent strength in addition to having the above-mentioned aptitude at the time of fixation. For this reason, the fiber reinforced composite material of this invention is used suitably as a component of all industrial products, and its industrial applicability is high.

DESCRIPTION OF SYMBOLS 10 Fiber reinforced composite material 12 Low density area | region 13 Notch part 14 High density area | region 20 Fixing member 30 Fixing target member 40 Hole

Claims (23)

  A fiber reinforced composite material including a reinforced fiber and a thermoplastic resin, wherein the fiber reinforced composite material has a low density region and a high density region, and the density of the low density region is P, and the density of the high density region Where Q is 1.5P <Q, and the ratio of the low density region to the total area of the fiber reinforced composite material is 0.001 to 15%. .   The fiber-reinforced composite material according to claim 1, wherein the low density region is a region for allowing a fixing member to pass therethrough.   3. The fiber reinforced fiber according to claim 1, wherein the reinforcing fiber is composed of a fiber having a fiber diameter of 20 μm or less, a glass transition temperature of 210 ° C. or more, and an elastic modulus of 50 GPa or more. Composite material.   The fiber-reinforced composite material according to any one of claims 1 to 3, wherein the content ratio of the reinforcing fiber and the thermoplastic resin is substantially constant in the entire region of the molded sheet.   The fiber-reinforced composite material according to any one of claims 1 to 4, wherein a content mass ratio of the reinforcing fibers and the thermoplastic resin is 0.2: 1 to 10: 1.   The fiber-reinforced composite material according to any one of claims 1 to 5, wherein the fiber-reinforced composite material has a concavo-convex structure, and the highest point of the convex portion belongs to a low density region.   The fiber-reinforced composite material according to claim 1, wherein the low-density region is formed as a discontinuous region in the fiber-reinforced composite material.   The fiber reinforced composite material according to claim 1, wherein the reinforcing fiber is a glass fiber or a carbon fiber.   The fiber-reinforced composite material according to claim 1, wherein the thermoplastic resin is polyetherimide, polycarbonate, nylon, polypropylene, or polyphenylene sulfide.   The fiber reinforced composite material according to any one of claims 1 to 9, wherein a through hole is further provided in the low density region.   11. The fiber-reinforced composite material according to claim 10, wherein a total area of the low density region and the through hole is greater than 1 and less than or equal to 4 times the area of the through hole.   A step of mixing a reinforcing fiber and a thermoplastic resin fiber, and producing a nonwoven fabric sheet by a dry nonwoven fabric method or a wet nonwoven fabric method, and heating and pressing the nonwoven fabric sheet at a temperature equal to or higher than the glass transition temperature of the thermoplastic resin fiber The step of heating and pressing includes a step of pressing a region to be penetrated through the fixing member of the nonwoven fabric sheet at a pressure lower than an average pressure. Method.   The method for producing a fiber-reinforced composite material according to claim 12, wherein the heat and pressure forming step includes a step of pressing a mold having a concave portion against the nonwoven fabric sheet to perform press processing.   A step of mixing a reinforcing fiber and a thermoplastic resin fiber, producing a nonwoven fabric sheet by a dry nonwoven fabric method or a wet nonwoven fabric method, laminating a plurality of the nonwoven fabric sheets, and a temperature equal to or higher than the glass transition temperature of the thermoplastic resin fiber Including the step of heat-press molding, wherein the step of heat-press molding is a low-density region by reducing the number of laminated nonwoven sheets in the region where the fixing member is to be penetrated. Manufacturing method of fiber reinforced composite material.   The fiber-reinforced composite material according to any one of claims 12 to 14, wherein an area of a region through which the fixing member is to penetrate is 0.001 to 15% of a total area of the nonwoven fabric sheet. Manufacturing method.   The process according to any one of claims 12 to 15, wherein the step of heating and pressing includes a step of heating to Tg to Tg + 100 ° C, where Tg is a glass transition temperature of the thermoplastic resin. The manufacturing method of the fiber reinforced composite material of description.   The fiber reinforced composite material manufactured by the manufacturing method of any one of Claims 12-16.   It is a fixing method which fixes the fiber reinforced composite material of any one of Claims 1-11 and 17 to a fixing object member using a fixing member, Comprising: The said fixing member is the low density of the said fiber reinforced composite material A fixing method, wherein the fixing target member and the fiber reinforced composite material are fixed by penetrating through a region.   The area of the low density region that penetrates the fixing member is greater than 1 and less than or equal to 4 times the area of the through hole formed when the fixing member is penetrated through the low density region of the fiber reinforced composite material. The fixing method according to claim 18, wherein:   The area of the low density region that penetrates the fixing member is 0.5 to 1 times the area of the through hole that is formed when the fixing member is penetrated through the low density region of the fiber-reinforced composite material. The fixing method according to claim 18.   The fixing method according to claim 18, wherein a low density region does not remain in the fiber-reinforced composite material after passing through the fixing member.   A fiber-reinforced composite material fixed to the member to be fixed, obtained by the fixing method according to claim 19.   A fiber-reinforced composite material, which is obtained by the fixing method according to claim 20 and is fixed to the member to be fixed.

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