Steel fiber reinforced plastic composite materials and automotive components

Abstract

A steel sheet / fiber-reinforced plastic composite material comprising: a steel sheet; and, formed on the steel sheet, a fiber-reinforced plastic laminate in which one or more glass-fiber-reinforced plastic layers and one or more carbon-fiber-reinforced plastic layers are alternately laminated. A layer in the fiber-reinforced plastic laminate, the layer being nearest to the steel sheet, is a glass-fiber-reinforced plastic layer, and the total volume proportion VC of the carbon-fiber-reinforced plastic layers in the fiber-reinforced plastic laminate is 0.1≤VC≤0.9.

Description

[Technical Field]

[0001] The present disclosure relates to a steel fiber reinforced plastic composite material and an automotive component. [Background technology]

[0002] In the automotive field, there is a demand for both lightweight components and crashworthiness, and for this reason, high-strength steel plates, high-strength aluminum alloys, and composite materials of steel plates and fiber-reinforced plastics have been developed. In the field of steel fiber reinforced plastic composite materials, technology has been developed to bond lightweight materials such as carbon fiber reinforced plastic (CFRP) and glass fiber reinforced plastic (GFRP) to steel plates. For example, Patent Document 1 discloses a steel plate-fiber-reinforced resin composite comprising: a steel plate member made of a steel plate or a molded product of the steel plate; a first resin layer located on at least a portion of the surface of the steel plate member and composed primarily of a resin composition made of two different materials; and a second resin layer located on at least a portion of the surface of the first resin layer and composed of a fiber-reinforced resin containing reinforcing fibers in a matrix resin, wherein the resin composition of the first resin layer contains a phenoxy resin and a polyester elastomer in a mass ratio (phenoxy resin:polyester elastomer) ranging from 20:80 to 80:20, and the resin composition is observed with an atomic force microscope (AFM) equipped with a probe with a tip radius of 10 nm in an atmosphere at 25°C, and in elastic modulus phase images of multiple arbitrary 10 μm square regions, the area ratio of the portions forming a phase-separated structure due to the phenoxy resin and the polyester elastomer is 1 area % or less of the total observed area.

[0003] [Patent Document 1] International Publication No. 2022 / 014587 Summary of the Invention [Problem to be solved by the invention]

[0004] However, while carbon fiber reinforced plastics (CFRP) are strong and highly elastic, they are expensive and suffer from electrochemical corrosion problems when used on steel plates, while glass fiber reinforced plastics (GFRP) are inexpensive and offer corrosion resistance, but have poor mechanical properties. Therefore, there is a demand for steel fiber reinforced plastic composite materials that can be manufactured at low cost, that are less susceptible to electrolytic corrosion, and that have high strength.

[0005] In response to this, the present disclosure aims to provide a steel plate fiber-reinforced plastic composite material that can reduce costs, suppresses the occurrence of electrolytic corrosion, and has high strength, and an automotive component that includes the steel plate fiber-reinforced plastic composite material. [Means for solving the problem]

[0006] The means for solving the problem include the following aspects. <1> Steel plate and a fiber-reinforced plastic laminate in which one or more glass fiber-reinforced plastic layers and one or more carbon fiber-reinforced plastic layers are alternately laminated on the steel plate; In the fiber reinforced plastic laminate, the layer closest to the steel plate side is the glass fiber reinforced plastic layer, The total volume ratio V of the carbon fiber reinforced plastic layers in the fiber reinforced plastic laminate C is 0.1≦V C ≦0.9, steel plate fiber reinforced plastic composite material. <2> The fiber reinforced plastic laminate has a multilayer structure of three or more layers in which two or more glass fiber reinforced plastic layers and one or more carbon fiber reinforced plastic layers are alternately laminated. <1> The steel plate fiber reinforced plastic composite material according to claim 1. <3> the fiber-reinforced plastic laminate has a four-layer structure in which two glass-fiber-reinforced plastic layers and two carbon-fiber-reinforced plastic layers are alternately laminated, The steel plate fiber-reinforced plastic composite material according to <2>, satisfying the following condition (i) or (ii). i) The tensile strength of the steel plate is 590 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber-reinforced plastic laminate, and the total volume ratio V of the carbon fiber-reinforced plastic layer C satisfy the following conditions (A) to (C). (A) 1.1 mm ≤ t2 ≤ 2.2 mm (B) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.9 (C) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber-reinforced plastic laminate, and the total volume ratio V of the carbon fiber-reinforced plastic layer C satisfy the following conditions (D) to (F). (D) 2.1 mm ≤ t2 ≤ 5.3 mm (E) 0.2 mm ≤ t1 ≤ 0.7 mm and 0.1 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.3 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.7 ≤ V C ≤ 0.9 (F) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <4> The fiber-reinforced plastic laminate has a five-layer structure in which three layers of the glass fiber-reinforced plastic layer and two layers of the carbon fiber-reinforced plastic layer are alternately laminated, The steel plate fiber-reinforced plastic composite material according to <2>, satisfying the following condition (i) or (ii). i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber-reinforced plastic laminate, and the total volume ratio V of the carbon fiber-reinforced plastic layer C satisfy the following conditions (G) to (I). (G) 1.2 mm ≤ t2 ≤ 2.2 mm (H) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.9 (I) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layer satisfy the following conditions (J) to (L). (J) 2.1 mm ≤ t2 ≤ 5.3 mm (K) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.2 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.5 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (L) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <5> The fiber reinforced plastic laminate has a multilayer structure of 6 layers or more in which 3 or more of the glass fiber reinforced plastic layers and 3 or more of the carbon fiber reinforced plastic layers are alternately laminated, and satisfies the condition of the following i) or the following ii). The steel plate fiber reinforced plastic composite material according to <2>. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layer satisfy the following conditions (M) to (O). (M) 1.2 mm ≤ t2 ≤ 2.2 mm (N) 0.2 mm ≤ t1 ≤ 0.3 mm and 0.1 ≤ V C ≤ 0.9, or 0.3 mm < t1 ≤ 0.4 mm and 0.2 ≤ V C ≤ 0.9 (O) t1 ≤ [(0.3 × V C[(-2)×t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (P) to (R). (P) 2.1 mm ≤ t2 ≤ 5.3 mm (Q) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.2 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.5 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (R) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <6> The fiber reinforced plastic laminate has a multilayer structure of 5 or more and odd layers in which 3 or more and odd layers of the glass fiber reinforced plastic layers and 2 or more and even layers of the carbon fiber reinforced plastic layers are alternately laminated, and the middle layer of the odd - numbered glass fiber reinforced plastic layers is present at the central position in the lamination direction of the fiber reinforced plastic laminate, the steel plate fiber reinforced plastic composite material according to <4> or <5>. <7> The fiber reinforced plastic laminate has a three - layer structure in which 2 layers of glass fiber reinforced plastic layers and 1 layer of carbon fiber reinforced plastic layer are alternately laminated, and satisfies the following condition i) or the following condition ii), the steel plate fiber reinforced plastic composite material according to <2>. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (S) to (U). (S) 1.2 mm ≤ t2 ≤ 2.2 mm (T) 0.2 mm ≤ t1 ≤ 0.3 mm and 0.1 ≤ V C ≤ 0.9, or 0.3 mm < t1 ≤ 0.4 mm and 0.3 ≤ V C ≤ 0.9 (U) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layer satisfy the following conditions (V) to (X). (V) 2.1 mm ≤ t2 ≤ 5.3 mm (W) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.4 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.7 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (X) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <8> The fiber reinforced plastic laminate has a two - layer structure in which one layer of glass fiber reinforced plastic layer and one layer of carbon fiber reinforced plastic layer are laminated, and satisfies the condition of the following i) or the following ii). The steel plate fiber reinforced plastic composite material according to <1>. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layer satisfy the following conditions (a) to (c). (a) 1.2 mm ≤ t2 ≤ 2.2 mm (b) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.9 (c) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 (ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (d) to (f). (d) 2.1 mm ≤ t2 ≤ 5.3 mm (e) 0.2 mm ≤ t1 ≤ 0.7 mm and 0.1 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.3 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (f) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <9> The fiber reinforced plastic laminate has a two - layer structure in which one layer of glass fiber reinforced plastic layer and one layer of carbon fiber reinforced plastic layer are laminated, The tensile strength of the steel plate is 1180 MPa or more, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (g) and (h) of the steel plate fiber reinforced plastic composite material according to <1>. (g) 1.7 mm ≤ t2 ≤ 3.5 mm (h) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.4 <10> The steel plate fiber reinforced plastic composite material according to <1>, which is used for automotive members. <11> An automotive member comprising the steel plate fiber reinforced plastic composite material according to <1>. [Advantages of the Invention]

[0007] According to the present disclosure, a steel plate fiber reinforced plastic composite material that can reduce cost, suppress the occurrence of electrolytic corrosion, and has high strength, and an automotive member including the steel plate fiber reinforced plastic composite material can be provided. [Brief Description of the Drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view showing a steel fiber reinforced plastic composite material according to a first embodiment. FIG. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a steel fiber reinforced plastic composite material according to a second embodiment. [Figure 3] FIG. 10 is a schematic cross-sectional view showing a steel fiber reinforced plastic composite material according to a third embodiment. [Figure 4] FIG. 10 is a schematic cross-sectional view showing a steel fiber reinforced plastic composite material according to a fourth embodiment. [Figure 5] FIG. 10 is a schematic cross-sectional view showing a steel fiber reinforced plastic composite material according to a fifth embodiment. [Figure 6] 1 is a graph showing the relationship between the plastic equivalent strain and stress of the steel plate used in the examples. [Figure 7] 1 is a graph comparing test results and calculation results in Example 1. [Figure 8] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in Example 4. [Figure 9] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 5000 series Al alloy of Example 5 was used as a control material. [Figure 10] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 7000 series Al alloy of Example 5 was used as a control material. [Figure 11] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 5000 series Al alloy of Example 6 was used as a control material. [Figure 12] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 7000 series Al alloy of Example 6 was used as a control material. [Figure 13]10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 5000 series Al alloy of Example 7 was used as a control material. [Figure 14] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 7000 series Al alloy of Example 7 was used as a control material. [Figure 15] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 5000 series Al alloy of Example 8 was used as a control material. [Figure 16] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 7000 series Al alloy of Example 8 was used as a control material. [Figure 17] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 5000 series Al alloy of Example 9 was used as a control material. [Figure 18] 10 is a graph showing the relationship between the total volume ratio VC of the carbon fiber reinforced plastic layers and the maximum bending load in a test in which the 7000 series Al alloy of Example 9 was used as a control material. [Figure 19] FIG. 1 is a schematic perspective view for explaining a method for measuring the thickness of a steel plate or the like. [Figure 20] FIG. 2 is a schematic cross-sectional view for explaining a method for measuring the thickness of a steel plate. [Figure 21] FIG. 2 is a schematic cross-sectional view illustrating a method for measuring the thickness of a fiber-reinforced plastic laminate. [Figure 22] FIG. 2 is a schematic cross-sectional view for explaining a method for measuring the thickness of a CFRP layer and a GFRP layer. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment that is an example of the present disclosure will be described. In this specification, when a numerical range expressed using "to" is not preceded or followed by "greater than" or "less than," it means a range that includes these numerical values ​​as the lower and upper limits. When "to" is preceded or followed by "greater than" or "less than," it means a range that does not include these numerical values ​​as the lower or upper limit. In the present specification, the upper limit of a numerical range may be replaced by the upper limit of another numerical range, or may be replaced by a value shown in an example. The lower limit of a numerical range may be replaced by the lower limit of another numerical range, or may be replaced by a value shown in an example. Furthermore, "%" in the content means "% by mass" unless otherwise specified. The content (%) of "0 or more" means that the component is an optional component and does not need to be contained.

[0010] <Steel fiber reinforced plastic composite material> A steel plate fiber reinforced plastic composite material (hereinafter also simply referred to as "composite material") according to an embodiment of the present disclosure includes a steel plate and a fiber reinforced plastic laminate (hereinafter also simply referred to as "laminate"). The laminate is formed by alternately laminating one or more glass fiber reinforced plastic layers (hereinafter also referred to as "GFRP layers") and one or more carbon fiber reinforced plastic layers (hereinafter also referred to as "CFRP layers") on a steel plate, with the glass fiber reinforced plastic (GFRP) layer being the layer closest to the steel plate. The total volume ratio V of the carbon fiber reinforced plastic (CFRP) layers in the laminate is C is 0.1≦V C ≦0.9

[0011] Total volume ratio of CFRP layers V C This refers to the ratio of the volume of the CFRP layer to the laminate, and when there are two or more CFRP layers in the laminate, it means the ratio of the total volume of all of them.

[0012] According to the embodiments of the present disclosure, a steel fiber reinforced plastic composite material can be obtained that can reduce costs, suppresses the occurrence of electrolytic corrosion, and has high strength. More specifically, in a composite material composed of steel plate and fiber-reinforced plastic (FRP), glass fiber-reinforced plastic (GFRP) and carbon fiber-reinforced plastic (CFRP) are used together to prevent electrolytic corrosion of the steel plate and reduce the volume ratio of the CFRP layer, thereby achieving cost reduction. Furthermore, a first object of the present invention is to obtain a steel plate fiber-reinforced plastic composite material that can achieve weight reduction (component mass) while maintaining rigidity (maximum bending load) at the same level or higher compared to the prior art document, Patent Document 1 (WO 2022 / 014587). A second objective is to obtain a steel fiber reinforced plastic composite material that is superior to aluminum alloys as a competing material in terms of weight reduction (component mass) and rigidity (maximum bending load).

[0013] In contrast, in an embodiment of the present disclosure, it has been discovered that the first object can be achieved by alternately stacking one or more glass fiber reinforced plastic (GFRP) layers and one or more carbon fiber reinforced plastic (CFRP) layers as the FRP in a composite material composed of steel plates and fiber reinforced plastic (FRP), and controlling the stacking order and the volume ratio of the CFRP layers. First, glass fiber reinforced plastic (GFRP) layers are cheaper than carbon fiber reinforced plastic (CFRP) layers, so increasing the volume ratio of glass fiber reinforced plastic (GFRP) layers in the fiber reinforced plastic laminate, i.e., the volume ratio of CFRP layers V C 0.1≦V C By setting the value to ≦0.9, the price can be reduced. Furthermore, when a steel plate and a CFRP layer are placed in direct contact with each other or when they are bonded together via an adhesive resin, electrolytic corrosion can occur in the steel plate. However, by placing the GFRP layer, which is an insulator, as the layer closest to the steel plate in the fiber-reinforced plastic laminate, electrolytic corrosion can be prevented. Furthermore, the CFRP layer has a high elastic modulus, i.e., the volume ratio V C 0.1≦V C By making it ≦0.9, it is possible to expect an increase in bending rigidity and an increase in maximum bending load due to an improvement in the second moment of area.

[0014] Furthermore, the number of layers of GFRP and CFRP, the tensile strength of the steel plate, the thickness of the steel plate t1, the thickness of the laminate t2, and the volume ratio of the CFRP layer V C , as well as t1, t2 and V C It has been found that the second object can be achieved by controlling the relationship between

[0015] The fiber reinforced plastic laminate preferably has a multi-layer structure of three or more layers, in which two or more glass fiber reinforced plastic (GFRP) layers and one or more carbon fiber reinforced plastic (CFRP) layers are alternately laminated. By using a multi-layer structure of three or more layers, it becomes easier to achieve cost reduction and high strength.

[0016] In the composite material according to the embodiment of the present disclosure, an adhesive layer (e.g., adhesive resin) may be interposed between the steel plate and the laminate, or an adhesive layer may not be present. In the case where an adhesive layer is not present, the steel plate and the laminate may be bonded together by a resin contained in the GFRP layer, for example. From the viewpoint of efficiently exerting the effects of the present disclosure, the thickness of the adhesive layer (average thickness at any 10 points) is preferably 1.0 mm or less.

[0017] Furthermore, in the composite material according to the embodiment of the present disclosure, another resin layer (i.e., a resin layer other than a GFRP layer and a CFRP layer, such as an adhesive layer containing an adhesive resin) may be interposed between the glass fiber reinforced plastic (GFRP) layer and the carbon fiber reinforced plastic (CFRP) layer. However, from the viewpoint of efficiently achieving the effects of the present disclosure, it is preferable that the thickness of the other resin layer (average thickness at any 10 points) be 1.0 mm or less. Therefore, in the present disclosure, "GFRP layers and CFRP layers are alternately laminated" includes not only a case where the GFRP layers and CFRP layers are laminated in direct contact with each other without any other layer therebetween, but also a case where the GFRP layers and CFRP layers are laminated with another resin layer therebetween. Note that one GFRP layer and one CFRP layer are based on the definition of "one layer" described below.

[0018] Here, the "one" glass fiber reinforced plastic layer (GFRP layer) and the "one" carbon fiber reinforced plastic layer (CFRP layer) in the present disclosure will be described. A single CFRP layer refers to the range from one boundary of the region where carbon fiber is contained in the matrix resin to the other boundary in the stacking direction of the laminate. For example, we will explain this using a laminate in which GFRP, CFRP, and GFRP are stacked in this order from top to bottom in the stacking direction of the laminate. When observing the CFRP in the middle, a boundary (one boundary) between the region where glass fiber is contained in the matrix resin and the region where carbon fiber is contained in the matrix resin can be observed, and below that, a boundary (the other boundary) between the region where carbon fiber is contained in the matrix resin and the region where glass fiber is contained in the matrix resin can be observed. The range from this one boundary to the other boundary is considered to be one CFRP layer. Furthermore, taking a laminate in which GFRP, CFRP, CFRP, and GFRP are stacked in this order from top to bottom in the stacking direction of the laminate (i.e., two CFRPs are stacked between GFRPs), the two CFRPs in the middle are considered to be one CFRP layer. When observing the two CFRPs in the middle, one boundary can be seen between the region where glass fiber is contained in the matrix resin and the region where carbon fiber is contained in the matrix resin, and below that, the region where carbon fiber is contained in the matrix resin (two CFRPs, i.e., one CFRP layer), and further below that, the boundary (the other boundary) between the region where carbon fiber is contained in the matrix resin and the region where glass fiber is contained in the matrix resin. The range from this one boundary to the other boundary (i.e., the range of the two CFRPs) is considered to be one CFRP layer. Similarly, for one GFRP layer, it means the range from one boundary to the other boundary of the region where glass fiber is contained in the matrix resin in the stacking direction of the laminate. Therefore, even if two (or more) GFRPs are stacked in contact with each other in the stacking direction of the laminate, the range from one boundary to the other boundary of the region where glass fiber is contained in the matrix resin is considered to be one GFRP layer.

[0019] The boundaries of CFRP layers (areas containing carbon fiber in the matrix resin) and GFRP layers (areas containing glass fiber in the matrix resin) can be distinguished by differences in color using an optical microscope. Also, if it is not easy to distinguish by color differences using an optical microscope, it is possible to identify the boundaries by identifying each layer through component analysis.

[0020] -Preferred embodiment- Next, preferred aspects of the steel fiber reinforced plastic composite material according to the embodiment of the present disclosure will be described with reference to the drawings.

[0021] First aspect As shown in Fig. 1, the fiber reinforced plastic laminate according to the first embodiment has a steel plate 2 and a fiber reinforced plastic laminate 61 on the steel plate 2. An adhesive layer 4 is also provided between the steel plate 2 and the fiber reinforced plastic laminate 61. The fiber reinforced plastic laminate 61 has a four-layer structure in which two glass fiber reinforced plastic (GFRP) layers G11, G12 and two carbon fiber reinforced plastic (CFRP) layers C11, C12 are alternately laminated. In the fiber reinforced plastic laminate 61, the glass fiber reinforced plastic (GFRP) layer G11 constitutes the layer closest to the steel plate 2.

[0022] In the fiber-reinforced plastic laminate according to the first embodiment, it is preferable to satisfy the following condition i) or ii) in order to obtain a steel plate fiber-reinforced plastic composite material that is superior to an aluminum alloy as a counter material in terms of weight reduction (mass of components) and rigidity (maximum bending load): i) The tensile strength of the steel plate is 590 MPa or more and less than 1180 MPa, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layer C meets the following conditions (A) to (C). (A) 1.1mm≦t2≦2.2mm (B) 0.2mm≦t1≦0.4mm and 0.1≦V C ≦0.9 (C)t1≦[(0.3×VC [(-2)×t2 + 5.4] / 7.8

[0023] ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (D) to (F). (D) 2.1 mm ≤ t2 ≤ 5.3 mm (E) 0.2 mm ≤ t1 ≤ 0.7 mm and 0.1 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.3 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.7 ≤ V C ≤ 0.9 (F) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8

[0024] In the present disclosure, in order to achieve weight reduction and rigidity superior to those of an aluminum alloy as a counter material, it is important that the weight is less than or equal to that of the aluminum alloy and that an excellent bending load is exhibited. Therefore, the weight of the steel plate fiber reinforced plastic laminate is set to be less than or equal to that of a 5000 - series Al alloy (thickness 2 mm, width 10 mm, length 130 mm, weight 13.8 g), or less than or equal to that of a 7000 - series aluminum alloy (thickness 4 mm, width 10 mm, length 130 mm, weight 27.5 g). Therefore, the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C can be set to values within a range not exceeding the weight of each aluminum alloy. From the relationship of the specific gravities of each material constituting the composite material, the thicker the thickness t2 of the fiber reinforced plastic laminate can be as the thickness t1 of the steel plate becomes thinner. Also, due to the difference in specific gravity between GFRP and CFRP, the thicker the thickness t2 of the fiber reinforced plastic laminate becomes as the total volume ratio V C of the carbon fiber reinforced plastic layers becomes smaller, and t2 becomes smaller as V C becomes larger.

[0025] The formula expressing this relationship is calculated as follows: The composite material according to the embodiment of the present disclosure is calculated to have a mass equal to or less than that of each of the aluminum alloys described above, and as a result, t1, t2, and V C The following relation is derived: 1) When comparing with a 2mm thick 5000 series aluminum alloy, the following inequality is derived. Specific gravity of steel plate × thickness of steel plate t1 + thickness of fiber reinforced plastic t2 ≦ Specific gravity of aluminum alloy × thickness of aluminum alloy Substituting numerical values ​​into this and transforming it gives 7.8×t1+[V C ×1.7+(1-V C )×2.0]≦2.7×2 →t1≦[(0.3×V C -2)×t2+5.4] / 7.8

[0026] 2) When comparing with a 7000 series aluminum alloy with a thickness of 4 mm, the following inequality is derived, similar to 1) above. 7.8×t1+[V C ×1.7+(1-V C )×2.0]≦2.7×4 →t1≦[(0.3×V C -2)×t2+10.8] / 7.8

[0027] In this way, t1, t2, and V C The above relational expression can be obtained, and the structure of the steel fiber reinforced plastic composite material can be specified so that the mass is equal to or less than that of the aluminum alloy, which is the opposing material.

[0028] Based on this, if we determine the range where the mass is less than that of the aluminum alloy and the maximum bending load exceeds that of the aluminum alloy, the following conditions are derived. Compared to 5000 series Al alloys: 1.1mm≦t2≦2.2mm 0.2mm≦t1≦0.4mm Compared to 7000 series Al alloys: 2.1mm≦t2≦5.3mm 1)0.2mm≦t1≦0.7mm, 0.1≦V C ≦0.9 2) 0.7 mm <t1≦0.8mm、0.3≦V C ≦0.9 3) 0.8 mm <t1≦0.9mm、0.7≦V C ≦0.9 In addition, when 7000 series aluminum alloys are used as the competing material, V C Since the time t1 at which the problem-solving effect is achieved varies depending on the value of , the range of 1) to 3) is calculated.

[0029] Second aspect As shown in Fig. 2, the fiber reinforced plastic laminate according to the second embodiment has a steel plate 2 and a fiber reinforced plastic laminate 62 on the steel plate 2. An adhesive layer 4 is also provided between the steel plate 2 and the fiber reinforced plastic laminate 62. The fiber reinforced plastic laminate 62 has a five-layer structure in which three glass fiber reinforced plastic (GFRP) layers G21, G22, and G13 and two carbon fiber reinforced plastic (CFRP) layers C21 and C22 are alternately laminated. In the fiber reinforced plastic laminate 62, the glass fiber reinforced plastic (GFRP) layer G21 constitutes the layer closest to the steel plate 2.

[0030] In the fiber-reinforced plastic laminate according to the second embodiment, it is preferable to satisfy the following condition i) or ii) in order to obtain a steel plate fiber-reinforced plastic composite material that is superior to aluminum alloy as a counter material in terms of weight reduction (mass of components) and rigidity (maximum bending load). i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layer C meets the following conditions (G) to (I). (G) 1.2mm≦t2≦2.2mm (H) 0.2mm≦t1≦0.4mm and 0.1≦V C ≦0.9 (I)t1≦[(0.3×V C -2)×t2+5.4] / 7.8

[0031] ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layers satisfy the following conditions (J) to (L). (J) 2.1 mm ≤ t2 ≤ 5.3 mm (K) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.2 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.5 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (L) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8

[0032] The basis for deriving these conditions i) and ii) is the same as that of the fiber reinforced plastic laminate according to the first aspect, from the viewpoint of achieving weight reduction and rigidity superior to those of the aluminum alloy as a countermeasure material.

[0033] The fiber reinforced plastic laminate 62 according to the second aspect has three or more and an odd number of glass fiber reinforced plastic layers G21, G22, G23 and two or more and an even number of carbon fiber reinforced plastic layers C21, C22 alternately laminated, that is, it has a multilayer structure of five or more and an odd number of layers. In this multilayer structure, it is preferable that the middle layer (that is, G22) of the odd-numbered glass fiber reinforced plastic layers G21, G22, G23 is present at the central position in the lamination direction of the fiber reinforced plastic laminate 62.

[0034] In this configuration, the layer closest to the steel plate side and the layer farthest from the steel plate side in the fiber reinforced plastic laminate are GFRP layers, and the central position in the lamination direction of the fiber reinforced plastic laminate is also a GFRP layer. That is, since the fiber reinforced plastic laminate has a structure close to a symmetric structure, thermal strain due to temperature changes during molding or use can be dispersed, thereby preventing fracture due to local stress concentration.

[0035] · Third aspect As shown in FIG. 3, the fiber reinforced plastic laminate according to the third aspect has a steel plate 2 and a fiber reinforced plastic laminate 63 on the steel plate 2. Further, an adhesive layer 4 is provided between the steel plate 2 and the fiber reinforced plastic laminate 63. The fiber reinforced plastic laminate 63 has a nine-layer structure in which three or more layers (for example, five layers in FIG. 3) of glass fiber reinforced plastic (GFRP) layers G31, G32, G33, G34, G35 and three or more layers (for example, four layers in FIG. 3) of carbon fiber reinforced plastic (CFRP) layers C31, C32, C33, C34 are alternately laminated. In the fiber reinforced plastic laminate 63, the glass fiber reinforced plastic (GFRP) layer G31 constitutes the layer closest to the steel plate 2 side.

[0036] In the fiber reinforced plastic laminate according to the third aspect, from the viewpoints of weight reduction (member mass) and rigidity (maximum bending load), it is preferable to satisfy the following condition i) or the following condition ii) from the viewpoint of obtaining a steel plate fiber reinforced plastic composite material superior to an aluminum alloy as a counter material. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layers satisfy the following conditions (M) to (O). (M) 1.2 mm ≤ t2 ≤ 2.2 mm (N) 0.2 mm ≤ t1 ≤ 0.3 mm and 0.1 ≤ V C ≤ 0.9, or 0.3 mm < t1 ≤ 0.4 mm and 0.2 ≤ V C ≤ 0.9 (O) t1 ≤ [(0.3 × VC [(-2)×t2 + 5.4] / 7.8

[0037] ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layers satisfy the following conditions (P) to (R). (P) 2.1 mm ≤ t2 ≤ 5.3 mm (Q) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.2 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.5 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (R) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8

[0038] The basis for deriving these conditions i) and ii) is the same as that of the fiber reinforced plastic laminate according to the first aspect from the viewpoint of achieving weight reduction and rigidity superior to those of the aluminum alloy as the counter material.

[0039] In the fiber reinforced plastic laminate according to the third aspect as well, for the same reason as in the second aspect, it is preferable that the middle layer (that is, G33) among the odd - numbered glass fiber reinforced plastic layers G31, G32, G33, G34, G35 exists at the central position in the lamination direction of the fiber reinforced plastic laminate 63.

[0040] · Fourth aspect The fiber-reinforced plastic laminate according to the fourth aspect has a steel plate 2 and a fiber-reinforced plastic laminate 65 on the steel plate 2 as shown in FIG. 5. Further, an adhesive layer 4 is provided between the steel plate 2 and the fiber-reinforced plastic laminate 65. The fiber-reinforced plastic laminate 65 has a three-layer structure in which two layers of glass fiber-reinforced plastic (GFRP) layers G51 and G52 and one layer of carbon fiber-reinforced plastic (CFRP) layer C51 are alternately laminated. In the fiber-reinforced plastic laminate 65, the glass fiber-reinforced plastic (GFRP) layer G51 constitutes the layer closest to the steel plate 2 side.

[0041] In the fiber-reinforced plastic laminate according to the fourth aspect, from the viewpoints of weight reduction (member mass) and rigidity (maximum bending load), and in terms of obtaining a steel plate fiber-reinforced plastic composite material that is superior to an aluminum alloy as a countermeasure material, it is preferable to satisfy the following condition i) or the following condition ii). i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber-reinforced plastic laminate, and the total volume ratio V C of the carbon fiber-reinforced plastic layers satisfy the following conditions (S) to (U). (S) 1.2 mm ≤ t2 ≤ 2.2 mm (T) 0.2 mm ≤ t1 ≤ 0.3 mm and 0.1 ≤ V C ≤ 0.9, or 0.3 mm < t1 ≤ 0.4 mm and 0.3 ≤ V C ≤ 0.9 (U) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8

[0042] ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber-reinforced plastic laminate, and the total volume ratio V C of the carbon fiber-reinforced plastic layers satisfy the following conditions (V) to (X). (V) 2.1 mm ≤ t2 ≤ 5.3 mm (W) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C≤0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.4 ≤ V C ≤0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.7 ≤ V C ≤0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤0.9 (X) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8

[0043] Note that the basis for deriving these conditions (i) and (ii) is the same as that of the fiber-reinforced plastic laminate according to the first aspect, from the viewpoint of achieving weight reduction and rigidity superior to those of the aluminum alloy as the counter material.

[0044] · Fifth aspect The fiber-reinforced plastic laminate according to the fifth aspect has, as shown in FIG. 4, a steel plate 2 and a fiber-reinforced plastic laminate 64 on the steel plate 2. It also has an adhesive layer 4 between the steel plate 2 and the fiber-reinforced plastic laminate 64. The fiber-reinforced plastic laminate 64 has a two-layer structure in which one layer of glass fiber-reinforced plastic (GFRP) layer G41 and one layer of carbon fiber-reinforced plastic (CFRP) layer C41 are laminated. In the fiber-reinforced plastic laminate 64, the glass fiber-reinforced plastic (GFRP) layer G41 constitutes the layer closest to the steel plate 2 side.

[0045] In the fiber-reinforced plastic laminate according to the fifth aspect, from the viewpoint of achieving weight reduction (member mass) while maintaining the rigidity (maximum bending load) at the same level or higher compared to the prior art document Patent Document 1 (International Publication No. 2022 / 014 / 587), it is preferable to satisfy the following conditions.

[0046] The tensile strength of the steel plate is 1180 MPa or more, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber-reinforced plastic laminate, and the total volume ratio V C of the carbon fiber-reinforced plastic layer satisfy the following conditions (g) and (h). (g) 1.7 mm ≤ t2 ≤ 3.5 mm (h) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ VC ≤0.4

[0047] Furthermore, in the fiber-reinforced plastic laminate according to the fifth aspect, from the viewpoint of weight reduction (member mass) and rigidity (maximum bending load), and from the viewpoint of obtaining a steel plate fiber-reinforced plastic composite material superior to an aluminum alloy as a counter material, it is preferable to satisfy the following condition i) or the following condition ii). i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber-reinforced plastic laminate, and the total volume ratio V C satisfy the following conditions (a) to (c). (a) 1.2 mm ≤ t2 ≤ 2.2 mm (b) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.9 (c) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8

[0048] ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 (mm) of the steel plate, the thickness t2 (mm) of the fiber-reinforced plastic laminate, and the total volume ratio V C satisfy the following conditions (d) to (f). (d) 2.1 mm ≤ t2 ≤ 5.3 mm (e) 0.2 mm ≤ t1 ≤ 0.7 mm and 0.1 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.3 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (f) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8

[0049] Note that the basis for deriving these conditions i) and condition ii) is the same as that of the fiber-reinforced plastic laminate according to the first aspect, from the viewpoint of achieving weight reduction and rigidity superior to an aluminum alloy as a counter material.

[0050] Here, various measurement methods will be explained.

[0051] The thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the thicknesses of the CFRP layer and the GFRP layer that make up the laminate are measured by observing the cross section using a microscope. First, a steel fiber-reinforced plastic composite material is cut parallel to the thickness direction, and the resulting first cut surface is observed under an optical microscope. To measure the steel plate thickness t1, the thickness of the steel plate is measured at five arbitrary positions on the surface of the steel plate at the first cut surface: one at the center and two at each side of the center. This is the vertical distance from the interface between the adhesive layer and the steel plate (if an adhesive layer is present) or the interface between the steel plate and the first GFRP layer in contact with the steel plate (if no adhesive layer is present) to the other end of the steel plate. The composite material is then cut at a location shifted an arbitrary distance in the direction perpendicular to the first cut surface to form a second cut surface, and the thickness of the steel plate is measured at these five arbitrary positions in the same way as for the first cut surface. The average of the 10 steel plate thicknesses obtained from the two cut surfaces is calculated and defined as the steel plate thickness t1.

[0052] The thickness t2 of the fiber-reinforced plastic laminate is also measured in the same manner as the steel plate thickness t1. That is, a first cut surface and a second cut surface are formed in the same manner as described above, and the thickness of the fiber-reinforced plastic laminate of the steel plate is measured at ten arbitrary positions on each cut surface, one at the center and two on each side of the center. The vertical distance is measured from the interface between the adhesive layer and the first GFRP layer on the steel plate side of the fiber-reinforced plastic laminate to the other end of the fiber-reinforced plastic laminate (if an adhesive layer is present between the steel plate and the fiber-reinforced plastic laminate), or from the interface between the steel plate and the first GFRP layer on the steel plate side of the fiber-reinforced plastic laminate to the other end of the fiber-reinforced plastic laminate (if no adhesive layer is present). The average thickness of the fiber-reinforced plastic laminate measured at all ten points is calculated and designated as the fiber-reinforced plastic laminate thickness t2.

[0053] Similarly, for the thickness of the CFRP layers and GFRP layers that make up the laminate, the thickness of each CFRP layer or GFRP layer (i.e., the vertical distance from one interface to the other interface of each CFRP layer or GFRP layer) is measured at a total of 10 arbitrary positions on the first cut surface and the second cut surface, one position in the center and two positions on each side of that. The average value of the thicknesses at all 10 positions is calculated and used as the thickness of the CFRP layer or GFRP layer.

[0054] Here, the cut surfaces and measurement positions will be explained using the drawings. For example, as shown in FIG. 19, a composite material having a steel plate 2 and a fiber-reinforced plastic laminate 6 on the steel plate 2, but no adhesive layer, will be explained as an example. First, the composite material is cut parallel to the thickness direction to form a first cut surface S1. Next, the composite material is cut at a location shifted an arbitrary distance from the first cut surface S1 in a direction perpendicular to the first cut surface S1 to form a second cut surface S2. The thickness of the steel plate at the first cut surface S1 (or the second cut surface S2) is measured by measuring the vertical distance between the interfaces of the steel plate 2 at five arbitrary positions, one at the center and two at each side of the center, as shown by the arrows in Figure 20. The thickness of the fiber-reinforced plastic laminate is measured by measuring the vertical distance between the interfaces of the fiber-reinforced plastic laminate 6 at five arbitrary positions, one in the center and two on each side of the center, as shown by the arrows in Figure 21. Furthermore, in the case of a fiber-reinforced plastic laminate consisting of two CFRP layers C1, C2 and two GFRP layers G1, G2, for a total of four layers, as shown in Figure 22, the thickness of the CFRP layers and GFRP layers is measured by measuring the vertical distance between the interfaces of the CFRP layers or GFRP layers at five arbitrary positions, one at the center and two at each side from there, as indicated by the arrows in Figure 22.

[0055] Measurement values ​​should be up to the first decimal place (mm).

[0056] Confirmation of whether or not a layer corresponds to a CFRP layer and whether or not it corresponds to a GFRP layer is carried out by analyzing the types and concentrations of the components contained using nuclear magnetic resonance analysis (NMR), infrared spectroscopy analysis (IR), and energy dispersive X-ray analysis (EDS) appropriately selected, and if necessary, combining two or more of them.

[0057] Total volume ratio of carbon fiber reinforced plastic (CFRP) layers V C is the calculated volume ratio of the CFRP layer in the fiber reinforced plastic laminate. Volume ratio V C is calculated from the ratio of the thickness of the CFRP layer to the thickness t2 of the fiber-reinforced plastic laminate consisting of a CFRP layer and a GFRP layer. When there are two or more CFRP layers, it is calculated from the total thickness of each CFRP layer. As mentioned above, the thicknesses of the CFRP layer and the GFRP layer are measured by cross-sectional observation using an optical microscope. That is, for the two cut surfaces, the first and second cut surfaces, the vertical distance between the interface of each CFRP layer and GFRP layer is measured at any five points as shown above, and the average values ​​of the 10 points obtained are calculated and used as the thickness of the CFRP layer and the thickness of the GFRP layer, respectively. Then, the obtained thickness of the CFRP layer (i.e., the average value of the 10 points) is divided by the thickness t2 of the fiber-reinforced plastic laminate measured using the method mentioned above, to give the volume ratio V C The measured value shall be rounded to one decimal place.

[0058] -Composite material components- Next, each member constituting the steel fiber reinforced plastic composite material according to an embodiment of the present disclosure will be described.

[0059] Carbon fiber reinforced plastic (CFRP) layer The carbon fiber reinforced plastic used in the CFRP layer is not particularly limited, but from the viewpoint of easily increasing rigidity (e.g., maximum bending load), it is preferable that the tensile modulus is in the range of 100 GPa to 160 GPa, and more preferably 125 GPa to 160 GPa.

[0060] CFRP has, for example, a matrix resin and carbon fibers contained in the matrix resin.

[0061] (carbon fiber) Pitch-based carbon fibers and PAN-based carbon fibers can be used as the carbon fibers. The carbon fibers may contain only one type of carbon fiber, or two or more types of carbon fibers. The carbon fibers may be UD materials in which fiber bundles are aligned in one direction, cross materials in which fibers are woven in a mesh pattern, or alternating laminate materials in which UD materials are alternately laminated. Here, the thickness of the carbon fiber bundles is not particularly limited, but it is possible to increase resin impregnation by spreading them thinly using, for example, a fiber-opening technique, and it is preferable that the thickness be 100 μm to 200 μm.

[0062] The carbon fiber content of CFRP (fiber volume fraction V f From the viewpoint of ensuring strength and processability, the carbon fiber content in the CFRP is preferably 10% by volume or more and 70% by volume or less. The carbon fiber content in the CFRP is preferably 15% by volume or more, 20% by volume or more, or 30% by volume or more, and 65% by volume or less, 60% by volume or less, or 55% by volume or less. Carbon fiber content of CFRP V f The measurement method for (vol %) can be performed as follows. A CFRP layer is peeled off from a composite material to obtain a test specimen for measuring the carbon fiber content. The bone dry mass (W3) of the test specimen is measured. Next, the test specimen is immersed in 20% hydrochloric acid to dissolve the matrix resin, and the bone dry mass (W4) of the carbon fiber obtained as a residue is measured. After the measurement, the carbon fiber content W based on the mass is calculated. f (mass%) = (W4 / W3) × 100, and the density of the test piece, ρ3 (g / cm 3 ) and the density of carbon fiber ρ4 (g / cm 3 ) the carbon fiber content V in CFRP f Calculate (volume %) = Wf × (ρ3 / ρ4).

[0063] (matrix resin) The matrix resin is a resin that constitutes CFRP. The type of resin used for the matrix resin is not particularly limited, and either a thermoplastic resin or a thermosetting resin can be used. Preferably, a thermoplastic resin that has good bending strength and excellent processability is used. The type of thermoplastic resin that can be used for the matrix resin is not particularly limited, and can be selected from the group consisting of phenoxy resin, polyolefin and its acid-modified product, polypropylene, polystyrene, polymethyl methacrylate, AS resin, ABS resin, thermoplastic aromatic polyester such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate, polyimide, polyamide, polyamideimide, polyetherimide, polyethersulfone, polyphenylene ether and its modified product, polyphenylene sulfide, polyoxymethylene, polyarylate, polyether ketone, polyether ether ketone, polyether ketone ketone, thermoplastic epoxy resin, unsaturated polyester resin, phenolic resin, urethane resin, nylon, etc.

[0064] Glass fiber reinforced plastic (GFRP) layer The glass fiber reinforced plastic used in the GFRP layer is not particularly limited, but from the viewpoint of easily increasing rigidity (e.g., maximum bending load), it is preferable that the tensile modulus is in the range of 25 GPa to 60 GPa, and more preferably 45 GPa to 60 GPa.

[0065] GFRP has, for example, a matrix resin and glass fibers contained in the matrix resin.

[0066] The reinforcing fibers contained in the glass fiber reinforced plastic (GFRP) are not particularly limited, but for example, E-glass, S-glass, T-glass, etc. can be used.

[0067] The type of resin used for the matrix resin is not particularly limited, but is preferably one that exhibits insulating properties, and either a thermoplastic resin or a thermosetting resin can be used. A thermoplastic resin that has good bending strength and excellent processability is preferred. The type of thermoplastic resin that can be used for the matrix resin is not particularly limited. Examples of resins that can be used include phenoxy, polyolefins and their acid-modified products, polypropylene, polystyrene, polymethyl methacrylate, AS resin, ABS resin, thermoplastic aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate, polyimide, polyamide, polyamideimide, polyetherimide, polyethersulfone, polyphenylene ether and its modified products, polyphenylene sulfide (PPS), polyoxymethylene, polyarylate, polyether ketone, polyether ether ketone (PEEK), polyether ketone ketone, thermoplastic epoxy resins, unsaturated polyester resins, phenolic resins, urethane resins, and nylon.

[0068] ·Steel plate The steel plate is not particularly limited in terms of material, shape, thickness, etc., but is preferably one that can be formed by pressing or the like, and is preferably in the form of a thin plate.

[0069] The tensile strength of the steel sheet is preferably in the range of 270 MPa to 2000 MPa, and from the viewpoint of easily increasing rigidity (for example, maximum bending load), it is more preferably 590 MPa or more.

[0070] The steel sheet may be subjected to a surface treatment. Examples of such treatments include, but are not limited to, various plating treatments such as zinc plating and aluminum plating, chemical conversion treatments such as chromate treatment and non-chromate treatment, and physical etching such as sandblasting or chemical surface roughening treatments such as chemical etching. Furthermore, the steel sheet may be subjected to alloying of plating or multiple types of surface treatments. It is preferable that the surface treatment be at least a treatment aimed at imparting rust prevention properties.

[0071] ·Adhesive layer The adhesive layer is not particularly limited, and organic adhesives such as thermoplastic resins and thermosetting resins, and inorganic adhesives such as water glass, silicate, cement, and gypsum can be used. Alternatively, the matrix resin exuded from the glass fiber reinforced plastic may function as the adhesive without providing an adhesive layer. Bonding by an organic adhesive or matrix resin is more preferred.

[0072] -Applications- The steel fiber reinforced plastic composite material according to the embodiment of the present disclosure can be used publicly, particularly for automobile components. [Example]

[0073] The effects of the present disclosure will be specifically explained below using examples.

[0074] Example 1 -Evaluation of consistency between calculation results and experimental results First, the consistency of the experimental results obtained by simulation in the examples described below was confirmed.

[0075] 1. Creation of a three-point bending calculation model 1-1. Creation of a calculation model for steel fiber reinforced plastic composite materials A calculation model of a steel plate fiber-reinforced plastic composite material with a width of 10 mm and a length of 130 mm was created, consisting of a steel plate with a tensile strength of 590 MPa and a thickness of 0.4 mm, an adhesive resin with a thickness of 0.05 mm, and a fiber-reinforced plastic laminate with a thickness of 1.08 mm. At this time, the fiber-reinforced plastic laminate was made into a four-layer structure as shown in Figure 1, and was stacked from the steel plate side in the following order: a 0.18 mm glass fiber reinforced plastic (GFRP) layer, a 0.18 mm carbon fiber reinforced plastic (CFRP) layer, a 0.54 mm GFRP layer, and a 0.18 mm CFRP layer.

[0076] 1-2. Physical properties of each material The physical properties (density, elastic modulus, Poisson's ratio, shear coefficient, and linear expansion coefficient) of the steel plate, adhesive resin, CFRP layer, and GFRP layer that make up the steel fiber reinforced plastic composite are shown in Table 1, and a curve showing the relationship between the plastic equivalent strain of the steel plate and stress is shown in Figure 6. For CFRP and GFRP, physical properties equivalent to a fiber volume fraction (Vf) of 60% were set.

[0077] [Table 1]

[0078] 2. Preparation of three-point bending specimens [Fiber reinforced plastic laminate] A 300mm x 300mm fiber-reinforced plastic laminate was fabricated using unidirectional polyacrylonitrile (PAN)-based carbon fiber prepreg (Vf = 55%) and unidirectional glass fiber prepreg (Vf = 58%). The first layer consisted of four unidirectional glass fiber prepreg sheets, the second layer consisted of four unidirectional PAN-based carbon fiber prepreg sheets, the third layer consisted of 12 unidirectional glass fiber prepreg sheets, and the fourth layer consisted of four unidirectional PAN-based carbon fiber prepreg sheets, for a total of 24 layers, with the volume ratio of the GFRP layers being 30%. This laminated sample was hot-pressed at 3 MPa, 250°C, and 1.5 min to obtain a molded panel.

[0079] [Steel fiber reinforced plastic composite material] A GA steel plate with a tensile strength of 590 MPa, an adhesive resin sheet, and the fiber-reinforced plastic laminate were laminated in this order, and hot-pressed at 3.6 MPa, 140°C, and 1 second to obtain a steel fiber-reinforced plastic composite material. At this time, the GFRP layer of the fiber-reinforced plastic laminate and the adhesive resin sheet were adjacent to each other.

[0080] [Conditions for bending tests and bending calculations] The resulting steel fiber-reinforced plastic composite material was cut into a width of 10 mm and a length of 130 mm and subjected to a three-point bending test. The dimensions of the three-point bending tester were an indenter radius r of 5 mm, a support point radius of 15 mm, and a distance between supports of 100 mm. The test piece was placed so that the indenter was hitting the steel plate side of the steel fiber-reinforced plastic composite material. The same dimensions and measurement conditions were used for the three-point bending calculation.

[0081] 3. Comparison of calculation and experiment results A comparison of the test results and calculation results is shown in Fig. 7. Although there was a slight difference in the load during the initial stroke, the maximum load was found to be roughly the same, confirming that the calculation model created can accurately predict bending strength.

[0082] <Example 2> ( <1> (corresponding to 1. Creation of a three-point bending calculation model 1-1. Creation of a calculation model for steel fiber reinforced plastic composite materials A calculation model of a steel plate fiber-reinforced plastic composite material with a width of 10 mm and a length of 255 mm was created, consisting of a steel plate with a tensile strength of 2000 MPa and a thickness of 0.8 mm, an adhesive resin with a thickness of 0.05 mm, and a fiber-reinforced plastic laminate with a thickness of t2. At this time, the fiber reinforced plastic laminate had a three-layer structure as shown in Fig. 5, and was laminated from the steel plate side in the form of a 0.08 mm GFRP layer, a 1.2 mm CFRP layer, and a 1.1 mm GFRP layer. The physical properties of each material were the same as in Example 1.

[0083] 2. Three-point bending calculation conditions and evaluation method The three-point bending dimensions were an indenter radius r of 5 mm, a support point radius of 15 mm, and a distance between supports of 200 mm. The indenter was set so that it hit the steel plate side of the steel fiber-reinforced plastic composite, and the indentation depth was 55 mm. The evaluation criteria were the value of the maximum bending load. From the calculation results, a curve of the horizontal stroke and vertical load was calculated, and if the maximum value exceeded the maximum bending load of 433.8 N for a 7000 series Al alloy (width 10 mm, length 255 mm, thickness 4 mm), it was evaluated as "A (Good)", and if it was lower, it was evaluated as "B (Poor)".

[0084] 3. Calculation results It was confirmed that when the fiber reinforced plastic laminate had the above structure, it could withstand a load equivalent to that of the aluminum alloy, which was the opposing material.

[0085] [Table 2]

[0086] <Example 3> ( <1> (corresponding to 1. Creation of a three-point bending calculation model 1-1. Creation of a calculation model for steel fiber reinforced plastic composite materials A calculation model of a steel plate fiber-reinforced plastic composite material with a width of 10 mm and a length of 255 mm was created, consisting of a steel plate with a tensile strength of 1180 MPa and a thickness of 0.8 mm, an adhesive resin with a thickness of 0.05 mm, and a fiber-reinforced plastic laminate with a thickness of t2. The steel plate thickness t1 and the fiber reinforced plastic laminate thickness t2 are set so that the steel plate fiber reinforced plastic composite material of the present disclosure is lighter in mass than the steel plate fiber reinforced plastic composite material of the prior art document: International Publication No. 2022 / 014587. In order to further reduce costs, the thickness of the CFRP layer is set to be thinner than 1.6 mm. C The conventional configuration in WO 2022 / 014587 has a steel plate with a tensile strength of 1180 MPa and a thickness of 1.6 mm, a GFRP layer with a thickness of 0.05 mm, and a CFRP layer with a thickness of 1.6 mm. The fiber reinforced plastic laminate at this time had a two-layer structure as shown in Fig. 4. The physical properties of each material were the same as those of Example 1.

[0087] 2. Three-point bending calculation conditions and evaluation method The three-point bending dimensions were an indenter radius r of 5 mm, a support point radius of 15 mm, and a distance between supports of 200 mm. The indenter was set so that it hit the steel plate side of the steel fiber-reinforced plastic composite, and the indentation depth was 55 mm. The evaluation criteria were based on the maximum bending load value. From the calculation results, a curve of horizontal stroke and vertical load was calculated. If the maximum value was equal to or greater than the maximum bending load of 605.2 N in the prior art document, WO 2022 / 014587 (±10%), the evaluation was given an "A (Good)" rating; if it was below that range, the evaluation was given a "C (Poor)" rating. The weight reduction rate was calculated as the weight reduction rate (mass reduction rate) relative to the mass of the prior art document.

[0088] 3. Calculation results The strength of the steel plate is 1180 MPa, and the volume ratio of the CFRP layer is V C = 0.3, 0.4, three levels were set by changing t1 and t2 (Table 3). As a result of the calculation, it was confirmed that the configuration of the present disclosure can achieve lighter weight and cost reduction effects than the conventional configuration of the prior art.

[0089] [Table 3]

[0090] <Example 4> ( <2> (corresponding to 1. Creation of a three-point bending calculation model 1-1. Creation of a calculation model for steel fiber reinforced plastic composite materials A calculation model of a steel plate fiber-reinforced plastic composite material with a width of 10 mm and a length of 255 mm was created, consisting of a steel plate with a tensile strength of 590 MPa and a thickness of 0.4 mm, an adhesive resin with a thickness of 0.05 mm, and a fiber-reinforced plastic laminate with a thickness of t2. The thickness t2 of the fiber reinforced plastic laminate is set to the CFRP layer volume ratio V in the fiber reinforced plastic laminate so that the mass is equal to that of the 5000 series aluminum alloy, which is the counter material, with a width of 10 mm, a length of 255 mm, and a thickness of 2 mm. C The thickness was set to the calculated value. The fiber reinforced plastic laminate at this time had a four-layer structure as shown in Figure 1. The physical properties of each material were the same as those of Example 1.

[0091] 2. Three-point bending calculation conditions and evaluation method The three-point bending dimensions were an indenter radius r of 5 mm, a support point radius of 15 mm, and a distance between supports of 200 mm. The indenter was set so that it hit the steel plate side of the steel fiber reinforced plastic composite, and the indentation depth was 55 mm. The evaluation criteria were the value of the maximum bending load. From the calculation results, a curve of the horizontal axis stroke and vertical axis load was calculated, and if the maximum value at this time exceeded the maximum bending load of 30.7 N for 5000 series Al alloy, it was evaluated as "A (Good)", and if it was below, it was evaluated as "C (Poor)".

[0092] 3. Calculation level The strength of the steel plate is 590 MPa and the thickness is 0.4 mm. The volume ratio of the CFRP layer is V C When = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0, the thickness of the GFRP layer of the first layer (closest to the steel plate) was set to 0 mm, 0.08 mm, and 0.07 mm, resulting in a total of eight levels.

[0093] [Table 4]

[0094] 4. Calculation results The calculation results are shown in Figure 8, and the evaluation results are summarized in Table 5. No. 1 does not have a GFRP layer to prevent electrolytic corrosion, and the CFRP layer comes into contact with the steel plate via adhesive, so it can be determined that there is no electrolytic corrosion prevention effect. No. 8's maximum bending load was lower than that of the 5000 series Al alloy. These results show that the examples of the present disclosure have a mass equivalent to that of the Al alloy used as a comparative material, but exceed the maximum bending load, thereby providing an anti-galvanic corrosion effect.

[0095] [Table 5]

[0096] <Example 5> ( <3> (corresponding to 1. Creation of a three-point bending calculation model 1-1. Creation of a calculation model for 5000 series Al steel fiber reinforced plastic composite materials A calculation model of a steel plate fiber-reinforced plastic composite material with a width of 10 mm and a length of 255 mm was created, consisting of a steel plate with a tensile strength of 590 MPa and a thickness of t1, an adhesive resin with a thickness of 0.05 mm, and a fiber-reinforced plastic laminate with a thickness of t2. At this time, the fiber reinforced plastic laminate is configured as a four-layer structure as shown in Figure 1, and the thickness t2 of the fiber reinforced plastic laminate is set to the CFRP layer volume ratio V in the fiber reinforced plastic laminate so that the mass is equal to that of the 5000 series aluminum alloy, which is used as the opposing material and has a width of 10 mm, a length of 255 mm, and a thickness of 2 mm. C The thickness was set to the value calculated using the formula: Note that the physical properties of each material were the same as those of Example 1. In this example, the thickness t1 of the steel plate was set in the range of 0.2 mm≦t1≦0.5 mm, and the thickness t2 of the fiber-reinforced plastic laminate was set in the range of 0.8 mm≦t2≦2.2 mm in accordance with the change in thickness t1.

[0097] 1-2. Creation of a calculation model for 7000 series Al steel fiber reinforced plastic composite materials A calculation model of a steel plate fiber-reinforced plastic composite material was created, consisting of a steel plate with a tensile strength of 1180 MPa and a thickness of t1, an adhesive resin with a thickness of 0.05 mm, and a fiber-reinforced plastic laminate with a thickness of t2, and measuring 10 mm in width and 255 mm in length. At this time, the fiber reinforced plastic laminate is configured as a four-layer structure as shown in Figure 1, and the thickness t2 of the fiber reinforced plastic laminate is set to the CFRP layer volume ratio V in the fiber reinforced plastic laminate so that the mass is equal to that of the 7000 series aluminum alloy, which is used as the opposing material and has a width of 10 mm, a length of 255 mm, and a thickness of 4 mm. CThe thickness calculated using the formula was set. The physical properties of each material were the same as in Example 1. In this example, the thickness t1 of the steel plate was set in the range of 0.7 mm≦t1≦1.0 mm, and the thickness t2 of the fiber-reinforced plastic laminate was set in the range of 1.7 mm≦t2≦2.3 mm in accordance with the change in thickness t1.

[0098] 2. Three-point bending calculation conditions and evaluation method The three-point bending dimensions were an indenter radius r of 5 mm, a support point radius of 15 mm, and a distance between supports of 200 mm. The indenter was set so that it hit the steel plate side of the steel fiber-reinforced plastic composite, with a push-in depth of 55 mm. Evaluation criteria were based on three items: maximum bending load, electrolytic corrosion, and mass. For the maximum bending load, curves of horizontal stroke and vertical load were calculated from the calculation results. For the 5000 series Al alloy comparison, if the maximum bending load exceeded 30.7 N, and for the 7000 series Al alloy comparison, if the maximum bending load exceeded 433.8 N, an evaluation was given of "A (Good)," and if it was below that, a "B (Poor)."

[0099] 3. Calculation level [Compared to 5000 series Al alloys] The steel plate strength was standardized to 590 MPa, and the thickness of the steel plate t1 was set to 0.2, 0.4, and 0.5 so that it was equivalent in mass to the 5000 series Al alloy, and the thickness of the fiber reinforced plastic laminate t2 was set to 0.8, 1.1, and 2.2. The volume ratio of the CFRP layer V C The bending load was evaluated when the temperature was changed.

[0100] [Compared to 7000 series Al alloys] The steel plate strength was standardized to 1180 MPa, and the thickness of the steel plate t1 was set to 0.7, 0.8, 0.9, and 1.0 so that it was equivalent in mass to the 7000 series Al alloy, and the thickness of the fiber reinforced plastic laminate t2 was set to 1.7, 2.0, 2.1, and 2.3. For these, the volume ratio of the CFRP layer V C The bending load was evaluated when the temperature was changed.

[0101] [Table 6]

[0102] As shown in Table 6, the thickness of the steel plate t1 and the thickness of the fiber reinforced plastic laminate t2 are rounded to one decimal place (mm). This is because variations in the thickness of the steel plate and the fiber reinforced plastic laminate are taken into consideration. However, the formula ([(0.3 × V C -2)×t2+5.4] / 7.8, and [(0.3×V C When substituting t2 into [(-2) × t2 + 10.8) / 7.8), correct the value of t2 to three decimal places (mm) (i.e., if t2 = 1.7 mm, correct it to t2 = 1.700). Also, when comparing the calculation result of this formula with t1, correct the value of t1 to three decimal places (mm) (i.e., if t1 = 1.0 mm, correct it to t1 = 1.000). The same applies below.

[0103] 5. Calculation results The calculation results are shown in Figures 9 and 10, and the evaluation results are summarized in Table 7. These results show that materials that meet the following conditions i) or ii) have the same mass as the Al alloy of the comparison material, but exceed the maximum bending load and are effective in preventing electrolytic corrosion. Furthermore, since the problem-solving effect was achieved at 590 MPa and 1180 MPa, it can be said that the problem-solving effect is also achieved at a tensile strength between these (980 MPa). i) The tensile strength of the steel plate is 590 MPa or more and less than 1180 MPa, and the total volume ratio V of the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the carbon fiber reinforced plastic layer C meets the following conditions (A) to (C). (A) 1.1mm≦t2≦2.2mm (B) 0.2mm≦t1≦0.4mm and 0.1≦V C ≦0.9 (C)t1≦[(0.3×V C -2)×t2+5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (D) to (F). (D) 2.1 mm ≤ t2 ≤ 5.3 mm (E) 0.2 mm ≤ t1 ≤ 0.7 mm and 0.1 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.3 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.7 ≤ V C ≤ 0.9 (F) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8

[0104]

Table 7

[0105] <Example 6> (corresponding to <4> <6>) The structure of the fiber reinforced plastic laminate was a five - layer structure as shown in Fig. 2, and the method of creating the calculation model, model dimensions, calculation conditions, etc. were the same as in Example 5. In the five - layer fiber reinforced plastic laminate, it has three glass fiber reinforced plastic (GFRP) layers, and the middle layer of these GFRP layers is located at the central position in the lamination direction of the fiber reinforced plastic laminate.

[0106] 1. Calculation level The calculation level is shown in Table 8.

[0107]

Table 8

[0108] 2. Calculation results The obtained calculation results are summarized and shown in FIGS. 11 and 12, and the evaluation results are shown in Table 9. From these results, it was shown that those satisfying the following condition (i) or the following condition (ii) have an equivalent mass to the Al alloy of the countermeasure material and can obtain an overbending maximum load and an effect of preventing electric corrosion. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layer C satisfy the following conditions (G) to (I). (G) 1.2 mm ≤ t2 ≤ 2.2 mm (H) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.9 (I) t1 ≤ [(0.3 × V C −2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layer C satisfy the following conditions (J) to (L). (J) 2.1 mm ≤ t2 ≤ 5.3 mm (K) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.2 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.5 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (L) t1 ≤ [(0.3 × V C −2) × t2 + 10.8] / 7.8

[0109] [Table 9]

[0110] [Example 7] (corresponding to <5>) The structure of the fiber-reinforced plastic laminate was a nine-layer structure as shown in Fig. 3, and the method for creating the calculation model, model dimensions, calculation conditions, etc. were the same as in Example 5.

[0111] 1. Calculation level The calculation levels are shown in Table 10.

[0112] [Table 10]

[0113] 2. Calculation results The obtained calculation results are summarized in Fig. 13 and Fig. 14, and the evaluation results are shown in Table 11. From these results, it was shown that those satisfying the following condition (i) or the following condition (ii) have an equivalent mass to the Al alloy of the countermeasure material, and yet obtain an overbending maximum load and an effect of preventing electric corrosion. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber-reinforced plastic laminate, and the total volume ratio V of the carbon fiber-reinforced plastic layers C satisfy the following conditions (M) to (O). (M) 1.2 mm ≤ t2 ≤ 2.2 mm (N) 0.2 mm ≤ t1 ≤ 0.3 mm and 0.1 ≤ V C ≤ 0.9, or 0.3 mm < t1 ≤ 0.4 mm and 0.2 ≤ V C ≤ 0.9 (O) t1 ≤ [(0.3 × V C - 2) × t2 + 5.​​​​​​​​​​​≤0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.5 ≤ V C ≤0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤0.9 (R) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8

[0114]

Table 11

[0115] <Example 8> (corresponding to <7>) The structure of the fiber reinforced plastic laminate was a three - layer structure as shown in Fig. 5, and the method for creating the calculation model, model dimensions, calculation conditions, etc. were the same as in Example 5.

[0116] 1. Calculation level The calculation levels are shown in Table 12.

[0117]

Table 12

[0118] 2. Calculation results The obtained calculation results are summarized in Figs. 15 and 16, and the evaluation results are shown in Table 13. From these results, it was shown that those satisfying the following i) or the following ii) conditions have an anti - corrosion effect exceeding the bending maximum load while having the same mass as the Al alloy of the counter material. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layer satisfy the following conditions (S) to (U). (S) 1.2 mm ≤ t2 ≤ 2.2 mm (T) 0.2 mm ≤ t1 ≤ 0.3 mm and 0.1 ≤ V C ≤ 0.9, or 0.3 mm < t1 ≤ 0.4 mm and 0.3 ≤ V C≤0.9 (U)t1 ≤ [(0.3×V C −2)×t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layers satisfy the following conditions (V) to (X). (V) 2.1 mm ≤ t2 ≤ 5.3 mm (W) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.4 ≤ V C ≤ 0.9, or 0.7 mm < t1 ≤ 0.8 mm and 0.7 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (X) t1 ≤ [(0.3×V C −2)×t2 + 10.8] / 7.8

[0119]

Table 13

[0124]

Table 15

[0125] <Example 10> (corresponding to <9>) 1. Preparation of three-point bending calculation model 1-1. Preparation of calculation model for steel plate fiber reinforced plastic composite material A calculation model of a steel plate fiber-reinforced plastic composite material with a width of 10 mm and a length of 255 mm was created, consisting of a steel plate with a tensile strength of 1180 MPa and a thickness of t1, an adhesive resin with a thickness of 0.05 mm, and a fiber-reinforced plastic laminate with a thickness of t2. In addition, the conventional configurations in the prior art document, International Publication No. 2022 / 014587, were prepared as follows: a composite material having a steel plate with a tensile strength of 1180 MPa and a thickness of 1.6 mm, a GFRP layer with a thickness of 0.05 mm, and a CFRP layer with a thickness of 1.6 mm (Prior Art Document Example 1); and a composite material having a steel plate with a tensile strength of 1180 MPa and a thickness of 1.1 mm, a GFRP layer with a thickness of 0.03 mm, and a CFRP layer with a thickness of 1.1 mm (Prior Art Document Example 2). The fiber reinforced plastic laminate at this time had a two-layer structure as shown in Fig. 4. The physical properties of each material were the same as those of Example 1.

[0126] 2. Three-point bending calculation conditions and evaluation method The three-point bending dimensions were an indenter radius r of 5 mm, a support point radius of 15 mm, and a distance between supports of 200 mm. The indenter was set so that it hit the steel plate side of the steel fiber-reinforced plastic composite material, and the indentation depth was 55 mm. The evaluation criterion was the value of the maximum bending load. From the calculation results, a curve of horizontal stroke and vertical load was calculated, and the maximum value at this time was found. In addition, the weight reduction rate was calculated as the mass reduction rate relative to the mass of the 7000 series aluminum alloy.

[0127] 3. Calculation results The evaluation was based on the following criteria. · Maximum bending load: Loads below 433.8N, the maximum load for 7000 series aluminum alloys, were evaluated as "Load B (△)", and those below 300N were evaluated as "Load C (×)". Mass: Anything exceeding 27.5g, the mass of 7000 series aluminum alloys, was evaluated as "Mass C (×)". - Regarding maximum bending load and mass, if neither of the above applies, it was evaluated as "A (Good)". · Cost: CFRP layers with a thickness of over 1.6 mm were rated as "B (△)" in terms of cost, and those with a thickness of 1.6 mm or less were rated as "A (〇)". As a result of the calculation, it was confirmed that particularly excellent results were obtained in Examples 10-1 to 10-3, and that they were superior to the examples in the prior art and the 7000 series aluminum alloys.

[0128] [Table 16]

[0129] The present embodiment includes the following aspects. <1> Steel plate and a fiber-reinforced plastic laminate in which one or more glass fiber-reinforced plastic layers and one or more carbon fiber-reinforced plastic layers are alternately laminated on the steel plate; In the fiber reinforced plastic laminate, the layer closest to the steel plate side is the glass fiber reinforced plastic layer, The total volume ratio V of the carbon fiber reinforced plastic layers in the fiber reinforced plastic laminate C is 0.1≦V C ≦0.9, steel plate fiber reinforced plastic composite material. <2> The fiber reinforced plastic laminate has a multilayer structure of three or more layers in which two or more glass fiber reinforced plastic layers and one or more carbon fiber reinforced plastic layers are alternately laminated. <1> The steel plate fiber reinforced plastic composite material according to claim 1. <3> the fiber-reinforced plastic laminate has a four-layer structure in which two glass fiber-reinforced plastic layers and two carbon fiber-reinforced plastic layers are alternately laminated, Meet the following conditions i) or ii); <2> The steel plate fiber reinforced plastic composite material according to claim 1. i) The tensile strength of the steel plate is 590 MPa or more and less than 1180 MPa, and the total volume ratio V of the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the carbon fiber reinforced plastic layer C meets the following conditions (A) to (C). (A) 1.1 mm ≤ t2 ≤ 2.2 mm (B) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.9 (C) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layers satisfy the following conditions (D) to (F). (D) 2.1 mm ≤ t2 ≤ 5.3 mm (E) 0.2 mm ≤ t1 ≤ 0.7 mm and 0.1 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.3 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.7 ≤ V C ≤ 0.9 (F) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <4> The fiber reinforced plastic laminate has a five - layer structure in which three layers of the glass fiber reinforced plastic layers and two layers of the carbon fiber reinforced plastic layers are alternately laminated, and satisfies the condition of the following i) or the following ii). The steel plate fiber reinforced plastic composite material according to <2>. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layers satisfy the following conditions (G) to (I). (G) 1.2 mm ≤ t2 ≤ 2.2 mm (H) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.9 (I) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (J) to (L). (J) 2.1 mm ≤ t2 ≤ 5.3 mm (K) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.2 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.5 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (L) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <5> The fiber reinforced plastic laminate has a multilayer structure of 6 layers or more in which 3 or more of the glass fiber reinforced plastic layers and 3 or more of the carbon fiber reinforced plastic layers are alternately laminated, and satisfies the condition of the following i) or the following ii). The steel plate fiber reinforced plastic composite material according to <2>. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (M) to (O). (M) 1.2 mm ≤ t2 ≤ 2.2 mm (N) 0.2 mm ≤ t1 ≤ 0.3 mm and 0.1 ≤ V C ≤ 0.9, or 0.3 mm < t1 ≤ 0.4 mm and 0.2 ≤ V C ≤ 0.9 (O) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers Csatisfies the following conditions (P) to (R). (P) 2.1 mm ≤ t2 ≤ 5.3 mm (Q) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.2 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.5 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (R) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <6> The fiber - reinforced plastic laminate has a multilayer structure with 5 or more and odd - numbered layers in which 3 or more and odd - numbered glass fiber - reinforced plastic layers and 2 or more and even - numbered carbon fiber - reinforced plastic layers are alternately laminated, and the middle layer of the odd - numbered glass fiber - reinforced plastic layers is located at the central position in the lamination direction of the fiber - reinforced plastic laminate, the steel - plate fiber - reinforced plastic composite material according to <4> or <5>. <7> The fiber - reinforced plastic laminate has a three - layer structure in which 2 layers of glass fiber - reinforced plastic layers and 1 layer of carbon fiber - reinforced plastic layer are alternately laminated, and satisfies the following condition i) or condition ii), the steel - plate fiber - reinforced plastic composite material according to <2>. i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber - reinforced plastic laminate, and the total volume ratio V C of the carbon fiber - reinforced plastic layers satisfy the following conditions (S) to (U). (S) 1.2 mm ≤ t2 ≤ 2.2 mm (T) 0.2 mm ≤ t1 ≤ 0.3 mm and 0.1 ≤ V C ≤ 0.9, or 0.3 mm < t1 ≤ 0.4 mm and 0.3 ≤ V C ≤ 0.9 (U) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (V) to (X). (V) 2.1 mm ≤ t2 ≤ 5.3 mm (W) 0.2 mm ≤ t1 ≤ 0.6 mm and 0.1 ≤ V C ≤ 0.9, 0.6 mm < t1 ≤ 0.7 mm and 0.4 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.7 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (X) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <8> The fiber reinforced plastic laminate has a two-layer structure in which one layer of glass fiber reinforced plastic layer and one layer of carbon fiber reinforced plastic layer are laminated, The steel plate fiber reinforced plastic composite material according to <1>, which satisfies the following condition (i) or the following condition (ii). i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (a) to (c). (a) 1.2 mm ≤ t2 ≤ 2.2 mm (b) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.9 (c) t1 ≤ [(0.3 × V C - 2) × t2 + 5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t1 of the steel plate, the thickness t2 of the fiber reinforced plastic laminate, and the total volume ratio V of the carbon fiber reinforced plastic layers C satisfy the following conditions (d) to (f). (d) 2.1 mm ≤ t2 ≤ 5.3 mm (e) 0.2 mm ≤ t1 ≤ 0.7 mm and 0.1 ≤ V C ≤ 0.9, 0.7 mm < t1 ≤ 0.8 mm and 0.3 ≤ V C ≤ 0.9, or 0.8 mm < t1 ≤ 0.9 mm and 0.8 < V C ≤ 0.9 (f) t1 ≤ [(0.3 × V C - 2) × t2 + 10.8] / 7.8 <9> The fiber - reinforced plastic laminate has a two - layer structure in which one layer of glass fiber - reinforced plastic layer and one layer of carbon fiber - reinforced plastic layer are laminated. The tensile strength of the steel plate is 1180 MPa or more, and the thickness t1 of the steel plate, the thickness t2 of the fiber - reinforced plastic laminate, and the total volume ratio V C of the carbon fiber - reinforced plastic layer satisfy the following conditions (g) and (h). The steel - plate fiber - reinforced plastic composite material according to <1>. (g) 1.7 mm ≤ t2 ≤ 3.5 mm (h) 0.2 mm ≤ t1 ≤ 0.4 mm and 0.1 ≤ V C ≤ 0.4 <10> The steel - plate fiber - reinforced plastic composite material according to any one of <1> to <9>, which is used for an automotive member. <11> An automotive member comprising the steel - plate fiber - reinforced plastic composite material according to any one of <1> to <9>.

[0130] Note that the disclosure of Japanese Application No. 2023 - 060726 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference.

Explanation of Signs

[0131] 2 Steel plate 4 Adhesive layer 6, 61, 62, 63, 64, 65 Fiber - reinforced plastic laminate G1, G2, G11, G12, G21, G22, G23, G31, G32, G33, G34, G35, G41, G51, G52 Glass fiber reinforced plastic (GFRP) layer C1, C2, C11, C12, C21, C22, C31, C32, C33, C34, C41, C51 Carbon fiber reinforced plastic (CFRP) layer S1 1st cutting plane S2 2nd cutting plane

Claims

1. Steel plate and a fiber-reinforced plastic laminate having a four-layer structure in which two glass fiber-reinforced plastic layers and two carbon fiber-reinforced plastic layers are alternately laminated on the steel plate, In the fiber reinforced plastic laminate, the layer closest to the steel plate side is the glass fiber reinforced plastic layer, The total volume ratio V of the carbon fiber reinforced plastic layers in the fiber reinforced plastic laminate Ｃ is 0.1≦V Ｃ ≦0.9, A steel fiber reinforced plastic composite material that satisfies the following condition i) or the following condition ii): i) The tensile strength of the steel plate is 590 MPa or more and less than 1180 MPa, and the thickness t 1 of the steel plate, the thickness t 2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layer satisfy the following conditions (A) to (C): (A) 1.1mm≦t2≦2.2mm (B) 0.2 mm≦t 1 ≦0.4 mm and 0.1≦V C ≦0.9 (C) t 1 ≦ [(0.3×V C −2)×t 2 +5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t 1 of the steel plate, the thickness t 2 of the fiber reinforced plastic laminate, and the total volume ratio V C of the carbon fiber reinforced plastic layer satisfy the following conditions (D) to (F). (D) 2.1mm≦t2≦5.3mm (E) 0.2 mm≦t 1 ≦0.7 mm and 0.1≦V C ≦0.9, 0.7 mm<t 1 ≦0.8 mm and 0.3≦V C ≦0.9, or 0.8 mm<t 1 ≦0.9 mm and 0.7≦V C ≦0.9 (F) t 1 ≦ [(0.3×V C −2)×t 2 +10.8] / 7.8

2. A steel plate, a fiber-reinforced plastic laminate having a five-layer structure in which three glass fiber-reinforced plastic layers and two carbon fiber-reinforced plastic layers are alternately laminated on the steel plate; In the fiber reinforced plastic laminate, the layer closest to the steel plate side is the glass fiber reinforced plastic layer, a total volume ratio V C of the carbon fiber reinforced plastic layers in the fiber reinforced plastic laminate is 0.1≦V C ≦0.9; A steel fiber reinforced plastic composite material that satisfies the following condition i) or the following condition ii): i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ satisfies the following conditions (G) to (I). (G)1.2mm≦t ２ ≦2.2mm (H) 0.2mm≦t １ ≦0.4 mm and 0.1≦V Ｃ ≦0.9 (I)t １ ≦[(0.3×V Ｃ -2)×t ２ +5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ satisfies the following conditions (J) to (L). (J)2.1mm≦t ２ ≦5.3mm (K)0.2mm≦t １ ≦0.6 mm and 0.1≦V Ｃ ≦0.9, 0.6mm<t １ ≦0.7 mm and 0.2≦V Ｃ ≦0.9, 0.7mm<t １ ≦0.8 mm and 0.5≦V Ｃ ≦0.9, or 0.8 mm<t １ ≦0.9 mm and 0.8<V Ｃ ≦0.9 (L)t １ ≦[(0.3×V Ｃ -2)×t ２ +10.8] / 7.8

3. A steel plate, and a fiber reinforced plastic laminate having a multilayer structure of six or more layers in which three or more glass fiber reinforced plastic layers and three or more carbon fiber reinforced plastic layers are alternately laminated on the steel plate, In the fiber reinforced plastic laminate, the layer closest to the steel plate side is the glass fiber reinforced plastic layer, a total volume ratio V C of the carbon fiber reinforced plastic layers in the fiber reinforced plastic laminate is 0.1≦V C ≦0.9; A steel fiber reinforced plastic composite material that satisfies the following condition i) or the following condition ii): i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ satisfies the following conditions (M) to (O). (M)1.2mm≦t ２ ≦2.2mm (N) 0.2mm≦t １ ≦0.3 mm and 0.1≦V Ｃ ≦0.9, or 0.3 mm<t １ ≦0.4 mm and 0.2≦V Ｃ ≦0.9 (O)t １ ≦[(0.3×V Ｃ -2)×t ２ +5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ satisfies the following conditions (P) to (R). (P)2.1mm≦t ２ ≦5.3mm (Q) 0.2mm≦t １ ≦0.6 mm and 0.1≦V Ｃ ≦0.9, 0.6mm<t １ ≦0.7 mm and 0.2≦V Ｃ ≦0.9, 0.7mm<t １ ≦0.8 mm and 0.5≦V Ｃ ≦0.9, or 0.8 mm<t １ ≦0.9 mm and 0.8<V Ｃ ≦0.9 (R)t １ ≦[(0.3×V Ｃ -2)×t ２ +10.8] / 7.8

4. The fiber reinforced plastic laminate has a multilayer structure of five or more layers and an odd number of layers in which three or more glass fiber reinforced plastic layers and two or more even number of carbon fiber reinforced plastic layers are alternately laminated, 3. The steel plate fiber-reinforced plastic composite material according to claim 2, wherein the middle layer of the odd number of glass fiber-reinforced plastic layers is located at a central position in the lamination direction of the fiber-reinforced plastic laminate.

5. The fiber-reinforced plastic laminate has a multilayer structure of five or more layers and an odd number of layers, in which three or more layers and an odd number of layers of the glass fiber-reinforced plastic layers and two or more layers and an even number of layers of the carbon fiber-reinforced plastic layers are alternately stacked, 4. The steel plate fiber-reinforced plastic composite material according to claim 3, wherein the middle layer of the odd number of glass fiber-reinforced plastic layers is located at a central position in the lamination direction of the fiber-reinforced plastic laminate.

6. A steel plate, a fiber-reinforced plastic laminate having a three-layer structure in which two glass fiber-reinforced plastic layers and one carbon fiber-reinforced plastic layer are alternately laminated on the steel plate, In the fiber reinforced plastic laminate, the layer closest to the steel plate side is the glass fiber reinforced plastic layer, a total volume ratio V C of the carbon fiber reinforced plastic layers in the fiber reinforced plastic laminate is 0.1≦V C ≦0.9; A steel fiber reinforced plastic composite material that satisfies the following condition i) or the following condition ii): i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ satisfies the following conditions (S) to (U). (S)1.2mm≦t ２ ≦2.2mm (T)0.2mm≦t １ ≦0.3 mm and 0.1≦V Ｃ ≦0.9, or 0.3 mm<t １ ≦0.4 mm and 0.3≦V Ｃ ≦0.9 (U)t １ ≦[(0.3×V Ｃ -2)×t ２ +5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ satisfies the following conditions (V) to (X). (V)2.1≦t ２ ≦5.3#- (W)0.2mm≦t １ ≦0.6 mm and 0.1≦V Ｃ ≦0.9, 0.6mm<t １ ≦0.7 mm and 0.4≦V Ｃ ≦0.9, 0.7mm<t １ ≦0.8 mm and 0.7≦V Ｃ ≦0.9, or 0.8 mm<t １ ≦0.9 mm and 0.8<V Ｃ ≦0.9 (X)t １ ≦[(0.3×V Ｃ -2)×t ２ +10.8] / 7.8

7. A steel plate, a fiber-reinforced plastic laminate having a two-layer structure in which one glass fiber-reinforced plastic layer and one carbon fiber-reinforced plastic layer are laminated on the steel plate, In the fiber reinforced plastic laminate, the layer closest to the steel plate side is the glass fiber reinforced plastic layer, a total volume ratio V C of the carbon fiber reinforced plastic layers in the fiber reinforced plastic laminate is 0.1≦V C ≦0.9; A steel fiber reinforced plastic composite material that satisfies the following condition i) or the following condition ii): i) The tensile strength of the steel plate is 270 MPa or more and less than 1180 MPa, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ satisfies the following conditions (a) to (c). (a)1.2mm≦t ２ ≦2.2mm (b) 0.2mm≦t １ ≦0.4 mm and 0.1≦V Ｃ ≦0.9 (c)t １ ≦[(0.3×V Ｃ -2)×t ２ +5.4] / 7.8 ii) The tensile strength of the steel plate is 1180 MPa or more and 2000 MPa or less, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ satisfies the following conditions (d) to (f). (d)2.1mm≦t ２ ≦5.3mm (e) 0.2mm≦t １ ≦0.7 mm and 0.1≦V Ｃ ≦0.9, 0.7mm<t １ ≦0.8 mm and 0.3≦V Ｃ ≦0.9, or 0.8 mm<t １ ≦0.9 mm and 0.8<V Ｃ ≦0.9 (f)t １ ≦[(0.3×V Ｃ -2)×t ２ +10.8] / 7.8

8. A steel plate, a fiber-reinforced plastic laminate having a two-layer structure in which one glass fiber-reinforced plastic layer and one carbon fiber-reinforced plastic layer are laminated on the steel plate, In the fiber reinforced plastic laminate, the layer closest to the steel plate side is the glass fiber reinforced plastic layer, a total volume ratio V C of the carbon fiber reinforced plastic layers in the fiber reinforced plastic laminate is 0.1≦V C ≦0.9; The tensile strength of the steel plate is 1180 MPa or more, and the thickness t of the steel plate is １ , the thickness t of the fiber reinforced plastic laminate ２ and the total volume ratio V of the carbon fiber reinforced plastic layer Ｃ A steel fiber reinforced plastic composite material, which satisfies the following conditions (g) and (h): (g)1.7mm≦t ２ ≦3.5mm (h) 0.2mm≦t １ ≦0.4 mm and 0.1≦V Ｃ ≦0.4

9. The steel fiber reinforced plastic composite material according to any one of claims 1 to 8, which is used for an automobile member.

10. An automotive member comprising the steel fiber reinforced plastic composite material according to any one of claims 1 to 8.

Images