Laminated molded body

Abstract

The present invention aims to provide a laminated molded body with improved strength characteristics against axial compressive loads. [Solution] The laminated molded body according to the present invention is a laminated molded body F formed by laminating and integrating fiber-reinforced layers AP, each containing a large number of aligned reinforcing fibers, arranged in multiple axes, wherein the fiber-reinforced layers AP include a plurality of groups of reinforcing fibers, and are set so that the fiber length directions of at least two groups of reinforcing fibers intersect each other from opposite sides with respect to the axial direction of arrangement.

Description

Technical Field

[0001] The present invention relates to a laminated molded body in which fiber reinforcement layers each containing a large number of aligned reinforcing fibers are arranged in a multi-axis direction and laminated integrally.

Background Art

[0002] A fiber-reinforced composite material is a combination of a reinforcing fiber material and a matrix material, and is a material that is lightweight, has high rigidity, and enables various functional designs. Therefore, it is used in a wide range of fields such as the aerospace field, the transportation field, the civil engineering and construction field, and the sports equipment field. In particular, fiber-reinforced plastics (FRP; Fiber Reinforced Plastics) in which reinforcing fiber materials such as carbon fibers and glass fibers are combined with thermosetting resin materials have become mainstream. In fiber-reinforced composite materials, a laminated molded body with enhanced strength in the multi-axis direction is often used by laminating prepreg sheets reinforced in one direction and setting the aligned direction of each layer in the multi-axis direction.

[0003] Since the reinforcing directions of the respective layers of the laminated molded body are different, there is a problem that delamination is likely to occur. In particular, when a thermosetting resin material such as an epoxy resin is used as the matrix, the thermosetting resin material generally has low toughness and there is a problem that delamination is likely to occur. For example, when an impact load or the like is applied to the laminated molded body, even if it seems to have no problem in appearance, delamination occurs inside the molded body, the mechanical properties of the laminated molded body are deteriorated, and it is often in a state where it is easily broken.

[0004] In Patent Document 1, in response to such problems, a fiber reinforcement layer having a thickness of 20 to 80 μm in which a reinforcing fiber material is dispersed in a thermosetting resin material serving as a matrix is laminated, and a laminated portion in which the fiber reinforcement layer is laminated and a laminated portion in which a resin layer is laminated between the layers of the fiber reinforcement layer are included. By making it a laminated molded body, it is described that the occurrence of delamination can be suppressed and good strength characteristics with improved impact resistance characteristics and fatigue life can be obtained.

[0005] Non-patent document 1 reports that when a tensile test is performed on a composite material in which aligned reinforcing fibers are dispersed in a matrix resin material, with the fiber length direction of the reinforcing fibers tilted at a predetermined angle with respect to the tensile load direction, the plasticity of the matrix resin causes the reinforcing fibers to rotate and reorient in the load direction, resulting in pseudo-ductility and increased stiffness after yielding. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 5736560 [Non-patent literature]

[0007] [Non-Patent Document 1] JDFuller et al., 'Pseudo-ductility and damage suppression in thin ply CFRP angle-ply laminates', Composites: Part A 69(2015) 64-71 [Overview of the project] [Problems that the invention aims to solve]

[0008] Patent Document 1 proposes improving impact resistance in the lamination direction by placing a resin layer between fiber-reinforced layers, but there is a need to improve strength characteristics in directions other than the lamination direction. Non-Patent Document 1 suggests that ductility in the load direction can be added by tilting the fiber length direction of the reinforcing fibers with respect to tensile load.

[0009] On the other hand, in fiber-reinforced composite materials, when the reinforcing fibers are aligned along the axial direction and a compressive load is applied in the axial direction, the reinforcing fibers deform by buckling, causing brittle fracture due to delamination. This presents a problem in that the strength properties are reduced compared to other materials such as metallic materials.

[0010] Therefore, the present invention aims to provide a laminated molded body with improved strength characteristics against axial compressive loads. [Means for solving the problem]

[0011] The laminated molded body according to the present invention is a laminated molded body formed by laminating and integrating fiber-reinforced layers, each containing a large number of aligned reinforcing fibers, arranged in multiple axes. The fiber-reinforced layer, arranged in at least one axis, includes a plurality of reinforcing fiber groups, each consisting of a large number of aligned reinforcing fibers, and is configured such that the fiber lengths of at least two of the reinforcing fiber groups intersect each other from opposite sides with respect to the axis of arrangement. Furthermore, the intersection angle of the fiber lengths of the reinforcing fiber groups with respect to the axis of arrangement is set to 20° or less. Furthermore, the fiber-reinforced layer is configured such that the fiber lengths of the reinforcing fiber groups intersect symmetrically with respect to the axis of arrangement. Furthermore, the reinforcing fiber groups consist of prepreg sheets with a thickness of 10 μm to 80 μm, in which the aligned reinforcing fibers are dispersed in a matrix resin material, and the fiber-reinforced layer is integrally formed by laminating a plurality of the prepreg sheets so that the fiber lengths of the reinforcing fibers intersect. Furthermore, resin layers are laminated between at least some of the layers of the fiber-reinforced layer. [Effects of the Invention]

[0012] The present invention, having the above-described configuration, includes a fiber-reinforced layer arranged in at least one axial direction, comprising multiple groups of reinforcing fibers consisting of a large number of aligned reinforcing fibers, and is configured so that the fiber lengths of at least two of the reinforcing fiber groups intersect each other from opposite sides with respect to the axial direction of arrangement. As a result, the initial decrease in elastic modulus is smaller compared to a unidirectional material in which the fiber lengths are aligned in the axial direction. Furthermore, under axial compressive load, the intersecting angle of the reinforcing fiber groups that intersect each other from opposite sides in the axial direction is widened, making it less likely for matrix cracks and delamination originating from them to occur. Therefore, the fracture strain before fracture occurs under compressive load is increased, making it possible to improve compressive strength.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic diagram showing an enlarged part of the cross section of the laminated molded body F which is an embodiment according to the present invention. [Figure 2] It is an explanatory diagram exemplifying the laminated state of the prepreg sheets constituting the fiber reinforced layer. [Figure 3] It is an explanatory diagram showing the arrangement state of the prepreg sheets when laminating the fiber reinforced layer in the 4-axis direction. [Figure 4] It is a schematic diagram showing an enlarged part of the cross section of a modification regarding the laminated molded body. [Figure 5] It is an explanatory diagram showing the state where a resin layer is laminated between the layers of the fiber reinforced layer arranged in the 4-axis direction. [Figure 6] It is an explanatory diagram seen from above regarding the laminated sheet. [Figure 7] It is an explanatory diagram showing the process of cutting the laminated sheet to form the laminated tape. [Figure 8] It is an explanatory diagram when manufacturing a laminated molded body using a prepreg tape in which the reinforcing fibers are aligned in the longitudinal direction. [Figure 9] It is an explanatory diagram when manufacturing a laminated molded body using a prepreg tape in which the reinforcing fibers are aligned in the longitudinal direction. [Figure 10] It is a graph showing the calculation method of various parameters. [Figure 11A] It is a graph showing the measurement results of the compression test regarding the uniaxial direction laminated molded body. [Figure 11B] It is a graph showing the measurement results of the compression test regarding the uniaxial direction laminated molded body.

Modes for Carrying Out the Invention

[0014] Embodiments of the present invention will be described below with reference to the drawings. While the embodiments described below are preferred examples for carrying out the present invention and therefore have various technical limitations, the present invention is not limited to these forms unless specifically stated in the following description to limit the present invention.

[0015] Figure 1 is a schematic diagram showing an enlarged portion of the cross-section of a laminated molded body F, which is an embodiment of the present invention. The laminated molded body F is formed by laminating and integrating fiber-reinforced layers AP1 to APn, each containing a plurality of reinforcing fiber groups made up of a large number of aligned reinforcing fibers, arranged in multiple axes.

[0016] Here, arranging the fiber reinforcement layers in multiple axes means that, when the direction perpendicular to the lamination direction of the fiber reinforcement layers is considered as the axis, each fiber reinforcement layer is set to be offset by a different angle from the reference axis, and is laminated so that it aligns with different axis directions.

[0017] In this embodiment, the fiber reinforcement layer is arranged such that the fiber lengths of at least two groups of reinforcing fibers intersect from opposite sides in the axial direction relative to the axial direction in which it is positioned. The reinforcing fiber groups whose fiber lengths intersect are arranged at different angles along the axial direction, resulting in the fiber reinforcement layer being arranged in multiple axial directions.

[0018] Furthermore, a fiber-reinforced layer comprising groups of reinforcing fibers whose fiber length directions intersect each other from opposite sides with respect to the axial direction of arrangement only needs to be arranged in at least one axial direction, and the axial direction of arrangement can be appropriately set according to the compression characteristics of the laminated molded body, etc.

[0019] The fiber-reinforced layer comprises at least two groups of reinforcing fibers arranged in different fiber length directions, with each group of reinforcing fibers arranged in layers in the lamination direction of the fiber-reinforced layer. As the groups of reinforcing fibers, for example, a prepreg sheet in which aligned reinforcing fibers are dispersed in a matrix resin material can be used, and the layer can be constructed by laminating at least two of these prepreg sheets.

[0020] Figure 2 is an explanatory diagram illustrating the lamination state of prepreg sheets constituting a fiber reinforcement layer. In the example shown in Figure 2(a), two prepreg sheets P1 and P2 are laminated together. With respect to the axial direction T of the fiber reinforcement layer, prepreg sheet P1 is positioned such that the fiber length direction S1 of the aligned reinforcing fibers within it is offset by an angle of -θ. Prepreg sheet P2 is positioned such that the fiber length direction S2 of the aligned reinforcing fibers within it is offset by an angle of +θ with respect to the axial direction T. Therefore, the reinforcing fibers in prepreg sheets P1 and P2 are aligned such that the fiber length directions S1 and S2 intersect each other from opposite sides with respect to the axial direction T.

[0021] In the example shown in Figure 2(b), two prepreg sheets P1 are stacked together with their fiber length direction offset by an angle of -θ relative to the axial direction T, and two prepreg sheets P2 are stacked together with their fiber length direction offset by an angle of +θ relative to the axial direction T, resulting in a stack of four prepreg sheets. In this example as well, the fiber length directions of the prepreg sheets are set to intersect each other from opposite sides with respect to the axial direction when viewed from the stacking direction.

[0022] In the example shown in Figure 2(c), four prepreg sheets are laminated by alternately stacking prepreg sheets P1, in which the fiber length direction is offset by an angle of -θ with respect to the axial direction T, and prepreg sheets P2, in which the fiber length direction is offset by an angle of +θ with respect to the axial direction T. In this example as well, when viewed from the lamination direction, the fiber length directions of the prepreg sheets are set to intersect each other from opposite sides with respect to the axial direction.

[0023] As illustrated in Figure 2, in the fiber reinforcement layer, the fiber lengths of the reinforcing fiber group are aligned so that they intersect each other from opposite sides with respect to the axial direction of arrangement, and it is preferable to set the fiber lengths of the reinforcing fiber group so that they intersect symmetrically with respect to the axial direction.

[0024] Furthermore, the intersection angles of each reinforcing fiber group with respect to the axial direction in the fiber length direction may be set asymmetrically at different angles from one another, and are not limited to line symmetry.

[0025] Furthermore, as long as the fiber-reinforced layer can be constructed by aligning the fiber lengths of the reinforcing fiber group so that they intersect from opposite sides, reinforcing fiber groups other than prepreg sheets may be used, and are not particularly limited. For example, by constructing a cross-laminated board, a diagonally-laminated board, or a pseudo-isotropic laminate, the fiber lengths of the reinforcing fiber group can be configured to intersect from opposite sides with respect to the axial direction.

[0026] Based on the findings described in Non-Patent Literature 1, it is thought that by setting the fiber length direction of the reinforcing fibers to intersect with the axial direction in which the fiber-reinforced layer is arranged, when a tensile load is applied in the axial direction, displacement due to rotation of the reinforcing fibers in the direction of the load will occur. As a result, the intersecting reinforcing fibers are reoriented to narrow the intersection angle, suppressing brittle fracture of the fiber-reinforced layer, increasing the fracture strain, and thus increasing the tensile strength. It is thought that this rotation of the fiber-reinforced layer does not occur only in response to tensile loads. For example, in response to compressive loads, the intersecting reinforcing fibers are reoriented to widen the intersection angle, suppressing brittle fracture of the fiber-reinforced layer, increasing the fracture strain, and consequently improving the compressive properties.

[0027] The intersection angle of the fiber length direction of the reinforcing fiber group with respect to the axial direction of the fiber-reinforced layer is preferably set to 20° or less, and more preferably to 5° to 10°, when viewed from the lamination direction. If the intersection angle is greater than 20°, the angle difference between the compressive load applied in the axial direction and the fiber length direction becomes large, making it difficult to apply the compressive load and resulting in a decrease in compressive properties.

[0028] Examples of reinforcing fibers used in the fiber reinforcement layer include high-strength, high-modulus inorganic and organic fibers used in fiber reinforcement composite materials, such as carbon fibers, glass fibers, ceramic fibers, polyoxymethylene fibers, and aromatic polyamide fibers. Multiple types of these fibers may be combined, and there are no particular limitations on their fineness. Furthermore, the reinforcing fibers may be formed into wide, thin sheets using known air-splitting methods (see, for example, Japanese Patent No. 4740131).

[0029] Examples of resin materials that form the matrix of the fiber reinforcement layer include thermosetting resin materials such as epoxy resin, unsaturated polyester resin, vinyl ester resin, and phenolic resin, or thermoplastic resin materials such as polypropylene resin, polyamide resin, polyphenylene sulfide resin, polyetherimide resin, polyetheretherketone resin, and polymer alloys formed by mixing two or more of these thermoplastic resins.

[0030] The thickness of the prepreg sheet used for the fiber reinforcement layer is preferably 10 μm to 80 μm. By reducing the layer thickness, even when the fiber length direction of the prepreg sheet is arranged to intersect with the axial direction, the reduction in the compressive strength of the fiber reinforcement layer can be suppressed due to the restraining effect between the laminated prepreg sheets.

[0031] Furthermore, when the thickness of the prepreg sheet is less than 10 μm, it becomes difficult to manufacture, laminate, and handle the prepreg sheet itself, and the number of layers required to obtain a structure of the same thickness increases. When the thickness is greater than 80 μm, the constraint effect due to the thinning of the layer decreases, resulting in a decrease in compression characteristics.

[0032] The prepreg sheet used for the fiber reinforcement layer can be manufactured using a known prepreg manufacturing apparatus that impregnates the reinforcing fiber material with a thermosetting resin material or a thermoplastic resin material. When using a thermoplastic resin material, a sheet material is formed by bonding the reinforcing fiber material to a sheet of thermoplastic resin material by heat fusion or the like, and this sheet material is used as the prepreg sheet to form the fiber reinforcement layer. The prepreg sheet can be cut to an appropriate length, and the cut prepreg sheets can be laminated by arranging them so that the fiber lengths of the reinforcing fibers intersect each other from opposite sides with respect to the axial direction.

[0033] Figure 3 is an explanatory diagram showing the arrangement of prepreg sheets when fiber reinforcement layers are laminated in four axial directions. In this example, the fiber reinforcement layers are formed by overlapping the two prepreg sheets shown in Figure 2(a), and the four fiber reinforcement layers AP1 to AP4 are laminated in four axial directions with a 90° offset between each layer.

[0034] In each fiber reinforcement layer, the fiber length direction of the reinforcing fibers of the prepreg sheet is set to intersect with the axial direction at an angle of ±5°. In fiber reinforcement layer AP1, the reinforcing fibers are aligned with the fiber length direction shifted to 40° and 50°, respectively, with respect to the axial direction of 45°. Therefore, with respect to the axial direction, the fiber length directions of the reinforcing fibers of the prepreg sheet are set to intersect with each other from opposite sides.

[0035] In the fiber-reinforced layer AP2, the reinforcing fibers of the prepreg sheet are aligned with their fiber lengths offset by -5° and 5° respectively with respect to the 0° axial direction, so that the fiber lengths of the reinforcing fibers of the prepreg sheet intersect each other from opposite sides with respect to the axial direction.

[0036] In the fiber-reinforced layer AP3, the reinforcing fibers of the prepreg sheet are aligned with the fiber length directions offset by -50° and -40° respectively with respect to the -45° axial direction, so that the fiber length directions of the reinforcing fibers of the prepreg sheet intersect each other from opposite sides with respect to the axial direction.

[0037] In the fiber-reinforced layer AP4, the reinforcing fibers of the prepreg sheet are aligned with their fiber lengths offset by 85° and 95° respectively with respect to the 90° axial direction, so that the fiber lengths of the reinforcing fibers of the prepreg sheet intersect each other from opposite sides with respect to the axial direction.

[0038] By repeatedly stacking and integrating these four-axis fiber-reinforced layers, a laminated molded body can be obtained in which the fiber lengths of the reinforcing fibers of the prepreg sheet intersect each other from opposite directions in any of the axial directions.

[0039] Figure 4 is a schematic diagram showing an enlarged portion of the cross-section of a modified example of a laminated molded body. In this example, the laminated molded body F' has resin layers TR1 to TRm laminated between at least some of the fiber reinforcement layers AP1 to APn, and by laminating the resin layers, strength properties such as impact resistance can be improved.

[0040] The resin material used for the resin layer is preferably a thermoplastic resin material, which can be used in the form of fine powder, nonwoven fabric, mesh, film, or sheet. The resin layer may also contain fine powder, sheet, metal mesh, or metal foil of nanomaterials such as CNTs (carbon nanotubes) or graphene, and is not particularly limited as long as it can be integrally molded.

[0041] The thickness of the resin layer is preferably set to 1 μm to 80 μm. If the resin layer is thinner than 1 μm, there are problems such as difficulty in manufacturing, and if it is thicker than 80 μm, the entire molded product becomes thicker, and since the resin layer itself has lower strength compared to the fiber reinforcement layer, there are problems such as a decrease in the overall compression characteristics of the molded product.

[0042] Figure 5 is an explanatory diagram showing a state in which resin layers are laminated between layers of fiber-reinforced layers arranged in the four axial directions. In this example, as shown in Figure 3, resin layers TR1 to TR4 are laminated between each of the fiber-reinforced layers AP1 to AP4, which are arranged in the four axial directions.

[0043] By repeatedly laminating and integrating layers combining such fiber-reinforced layers and resin layers, a laminated molded body can be obtained in which the fiber lengths of the reinforcing fiber groups are arranged to intersect each other from opposite sides in any axial direction.

[0044] In the example described above, the resin layer is placed between each fiber reinforcement layer, but it can also be placed every other layer, and is not particularly limited.

[0045] The laminated molded body preferably has an overall fiber volume content (Vf) of 30% to 80%, and more preferably 50% to 70%. If Vf is less than 30%, the fiber reinforcement effect of the laminated molded body will not be sufficiently obtained, and if it exceeds 80%, the amount of resin will decrease, making it easier for voids (spaces) to form in the fiber reinforcement layer, which will degrade the mechanical properties of the laminated molded body.

[0046] Laminated molded articles can be manufactured by cutting prepreg sheets to a predetermined size, laminating them one by one to form fiber-reinforced layers, and then laminating and integrating multiple fiber-reinforced layers. Alternatively, laminated molded articles can be efficiently manufactured by pre-fabricating a laminated sheet by stacking multiple prepreg sheets so that the fiber lengths of the reinforcing fibers intersect, cutting the laminated sheet to a predetermined size, and then laminating and integrating the cut laminated sheets. Laminated molded articles can also be manufactured in a similar manner by laminating multiaxial sheets or fabrics, such as non-crimped fabrics, in which fiber bundles are oriented in two or more axes, placing them in a mold, and then injecting resin.

[0047] Figure 6 is an explanatory diagram of a laminated sheet viewed from above. In this example, a laminated sheet S1 is formed by overlapping two prepreg sheets P1 and P2. Prepreg sheet P1 is set so that the fiber length direction of the reinforcing fibers is offset by an angle of +θ counterclockwise when the vertical direction is set to 0°, and prepreg sheet P2 is set so that the fiber length direction of the reinforcing fibers is offset by an angle of -θ clockwise. Therefore, when prepreg sheets P1 and P2 are overlapped and laminated to form a laminated sheet, it is possible to manufacture a laminated sheet in which the fiber length directions of the reinforcing fibers intersect each other from opposite sides in the vertical direction. In this case, the vertical direction is the axis direction in which the laminated sheet is arranged.

[0048] In this example, the axial direction of the laminated sheet is defined as the direction of the axis of symmetry where the fiber length directions of the reinforcing fibers of the prepreg sheet intersect symmetrically. However, it is not limited to the axis of symmetry; by setting the axial direction between the intersecting fiber length directions of the reinforcing fibers of the prepreg sheet, it is possible to set it so that the fiber length directions intersect from opposite sides of the axial direction.

[0049] Laminated sheets can also be formed by stacking two or more prepreg sheets, and the number of prepreg sheets is not particularly limited as long as the fiber lengths of the reinforcing fibers of at least two prepreg sheets intersect. Furthermore, when laminating resin layers between the fiber-reinforced layers as shown in Figure 4, it is possible to efficiently manufacture laminated molded products including resin layers by pre-manufacturing the laminated sheets by stacking resin sheets on top of the prepreg sheets to be laminated.

[0050] When forming laminated molded bodies into a three-dimensional shape, automated lamination technologies such as automated fiber placement (AFP) and automated tape laying (ATL) have been developed (see, for example, Japanese Patent No. 6935620). For these lamination technologies, laminated tapes obtained by cutting the aforementioned laminated sheets into tape-like strips of a predetermined width can be used.

[0051] Figure 7 is an explanatory diagram showing the process of cutting a laminated sheet to form a laminated tape. As shown in Figure 6, the laminated sheet S1 is composed of two prepreg sheets P1 and P2 laminated together, and a laminated tape U1 can be obtained by cutting the laminated sheet S1 to a predetermined width along the axial direction C. When cutting, the laminated sheet can be cut using a cutting device such as a slitter, allowing for efficient processing by cutting multiple laminated tapes simultaneously.

[0052] In this case, regarding the cutting axis C, by setting the axis between the fiber length directions of the intersecting reinforcing fiber groups of the laminated sheet, it is possible to set it so that the fiber length directions of the reinforcing fiber groups intersect each other from opposite sides with respect to the axis.

[0053] The resulting laminated tape is configured such that the fiber lengths of the reinforcing fiber groups intersect. By laminating the laminated tape so that the tape length is aligned with the axial direction, a fiber reinforcement layer can be formed, aligning the fiber lengths of the reinforcing fiber groups so that they intersect from opposite sides with respect to the axial direction of arrangement.

[0054] Laminated sheets can also be manufactured using unidirectional prepreg tape in which reinforcing fibers are aligned longitudinally. Figure 8 is a schematic diagram of a manufacturing apparatus for forming laminated sheets using unidirectional prepreg tape, and Figure 9 is an explanatory diagram showing the lamination process in Figure 8.

[0055] In this example, multiple prepreg tapes are supplied in parallel so as to be oblique to the surface of a substrate such as release paper or release film being transported at a predetermined angle in the transport direction, thereby laminating the prepreg tapes so that their fiber lengths intersect in the axial direction (transport direction). The substrate transport mechanism 20 includes an unwinding roll 21 for unwinding a sheet-like substrate R, a stage 22 for supporting the transported substrate R, and a winding roll 23 for winding the substrate R, and is configured to transport the substrate R in a predetermined transport direction F1. Above the stage 22, there are slitters 24 positioned at both ends of the substrate R to cut the prepreg tapes PT along both ends.

[0056] Multiple tape supply mechanisms 101 to 105 are arranged in parallel above the stage 22. Each tape supply mechanism includes an unwinding roll 11 for feeding out the prepreg tape PT, a pressing roller 12 for pressing the fed-out prepreg tape PT against the base material R, and a cutter 13 for cutting the fed-out prepreg tape PT. Each tape supply mechanism is movable in the width direction of the prepreg tape PT and operates to move to the other side end of the base material R if the tape supply mechanism comes off one side end.

[0057] As shown in Figure 9, the substrate R is transported along both ends, and the slitter 24 is positioned along both ends. The prepreg tape PT is supplied to the surface of the substrate R in a supply direction F2 that is oblique to the substrate transport direction F1 at an angle θ counterclockwise, as shown by the dotted line. The prepreg tapes PT supplied from each tape supply mechanism are arranged parallel to each other and are in close contact with the surface of the substrate R so as to cover it without any gaps (Figure 9(a)).

[0058] Since the prepreg tape PT is supplied obliquely in the supply direction F2 relative to the transport direction of the base material R, it will sequentially detach from the rightmost edge of the base material R, starting from the rightmost prepreg tape PT (Figure 9(b)). Therefore, by cutting the prepreg tape PT at the moment it detaches from the rightmost edge of the base material R and moving the tape supply mechanism to the leftmost position, the prepreg tape PT can be supplied obliquely, ensuring that it adheres continuously and without gaps to the surface of the base material R (Figure 9(c)).

[0059] The prepreg tape PT, which is in close contact with the surface of the base material R, is cut by the slitter 24, and the base material R, with the prepreg tape PT in one direction closely attached to both ends at an angle θ so as to be tightly packed, is wound onto the winding roll 23.

[0060] A substrate R, to which unidirectional prepreg tape PT is tightly adhered without gaps, is then laminated in the next step during transport by supplying unidirectional prepreg tape PT in a supply direction that is obliquely clockwise at an angle θ with respect to the transport direction, ensuring tight adhesion without gaps. For the lamination of prepreg tape PT, multiple tape supply mechanisms can be arranged in parallel, similar to the tape supply mechanism described above, and the prepreg tape PT can be supplied and laminated at an oblique angle θ clockwise with respect to the transport direction.

[0061] In this way, a laminated sheet can be formed by closely laminating unidirectional prepreg tapes PT onto the surface of a base material R so that they intersect from opposite sides with respect to the transport direction.

[0062] Furthermore, by arranging a tape supply mechanism that moves diagonally clockwise and a tape supply mechanism that moves diagonally counterclockwise in the transport path of the base material R, prepreg tape PT can be sequentially supplied to the base material R during transport so as to intersect with each other from opposite sides of the transport direction, thereby enabling the continuous production of laminated sheets in which the two-directional prepreg tape PT are laid in close contact and intersecting with each other. [Examples]

[0063] <About the compression test> Using a precision universal testing machine (manufactured by Shimadzu Corporation), a rectangular molded plate (78 mm long x 12.5 mm wide x 2 mm thick) was positioned so that the direction of the compressive load coincided with the axial direction, and a compression test was performed in accordance with JIS K 7018. Based on the obtained test results, the compressive strength (MPa), elastic modulus (GPa), and fracture strain (%) were determined.

[0064] <Regarding the calculation of various parameters> Based on the calculation method shown in Non-Patent Document 1, yield stress, yield strain, and ductile strain were calculated. Figure 10 is a graph showing the calculation methods for various parameters, with compressive stress (MPa) on the vertical axis and strain (%) on the horizontal axis.

[0065] Yield stress (σ Y ) and yield strain (ε YFor ), the coordinates of the intersection point between the line L2 (0.1% offset line: shown as a dotted line), which is obtained by shifting the line L1 (shown as a dotted line) representing the initial modulus of elasticity by 0.1% in the X-axis direction, and the experimentally obtained stress-strain curve (shown as a solid line) are used to determine the yield stress (σ). Y ) and yield strain (ε Y ) was calculated as follows.

[0066] Ductus strain ((ε d For ) the fracture strain and stress at fracture (compressive strength) obtained in the experiment, the strain value at the straight line L1, which represents the initial elastic modulus corresponding to the stress at fracture, was calculated, and the difference between the calculated strain value and the fracture strain value was calculated as ductile strain.

[0067] <Regarding the manufacturing of laminated sheets and laminated molded products> Matrix resin An epoxy resin material was prepared by mixing and stirring the following materials as the matrix resin material. The density of the prepared epoxy resin material was 1.20 g / cm³. 3 That was the case. • Bisphenol A type epoxy resin (jER828: manufactured by Mitsubishi Chemical Corporation) 40 parts by weight • Bisphenol A type epoxy resin (jER1001: manufactured by Mitsubishi Chemical Corporation) 60 parts by weight • Accelerator (DCMU99: manufactured by Hodogaya Chemical Co., Ltd.) 2 parts by weight • Hardener (DICY15: manufactured by Mitsubishi Chemical Corporation) 5 parts by weight The prepared epoxy resin material was applied to the top surface of release paper (manufactured by Lintec Corporation) at a basis weight of 10.8 g / m². 2 The resin sheet was then created by coating it to a coating width of 320 mm.

[0068] Reinforcement fibers As reinforcing fibers, six carbon fiber bundles (TR50S15L: manufactured by Mitsubishi Chemical Corporation) are placed at 50mm intervals, and then opened using a fiber opening device (manufactured by Hokushin Co., Ltd.) to a width of 50mm per fiber, resulting in a 300mm wide opened yarn sheet (fiber basis weight: 20g / m²). 2 I created ).

[0069] 〇 Prepreg sheet The prepared open-fiber yarn sheet and resin sheet were bonded together, and a matrix resin was impregnated into the open-fiber yarn sheet under heating and pressure using a prepreg manufacturing device (manufactured by Hokushin Co., Ltd.) to create a prepreg sheet. The resulting prepreg sheet had a thickness of 0.02 mm and a fiber volume content of 55%.

[0070] Laminated molded body The prepared prepreg sheets were stacked in a uniaxial direction by hand layup in the lamination configuration shown in Table 1, and then molded into a flat, uniaxially laminated body using an autoclave (manufactured by Ashida Seisakusho Co., Ltd.) at 130°C for 2 hours. [Table 1]

[0071] In Examples 1 to 3, prepreg sheets were laminated with alternating offsets of ±5°, ±10°, and ±15°, respectively, with respect to the axial direction, so that the fiber lengths of the prepreg sheets intersect with the axial direction. In contrast, in Comparative Example 1, the fiber lengths of the prepreg sheets were laminated so that they coincided with the axial direction, and in Comparative Example 2, a laminated sheet with a thickness of 0.24 mm, consisting of 12 prepreg sheets laminated in one direction, was laminated with alternating offsets of ±5° with respect to the axial direction.

[0072] Furthermore, the prepared prepreg sheets were laminated in four axial directions by hand layup using the lamination configuration shown in Table 2, and then processed in the same manner as the uniaxial laminated molded body to form a flat, pseudo-isotropic laminated molded body. A 0° direction compression test was performed on the obtained molded plate to evaluate its mechanical properties. [Table 2]

[0073] In Example 4, the prepreg sheets were stacked alternately with a ±5° offset in the four axial directions; in Example 5, the prepreg sheets were stacked alternately with a ±10° offset in the four axial directions; and in Example 6, the prepreg sheets were stacked with a ±15° offset in the four axial directions. Therefore, in each example, the prepreg sheets were stacked so that the fiber length directions intersected the axial directions. On the other hand, in Comparative Example 3, the prepreg sheets were stacked so that the fiber length directions coincided with the four axial directions.

[0074] <Evaluation of mechanical properties of laminated molded bodies> Figures 11A and 11B show the measurement results of compression tests on the uniaxial laminated molded body shown in Table 1. In Figures 11A and 11B, the vertical axis represents the compression load (MPa) and the horizontal axis represents the compression strain (%), with the change in compression strain shown by a thick solid line.

[0075] Figure 11A(a) shows Comparative Example 1, Figure 11A(b) shows Example 1, Figure 11B(a) shows Example 2, and Figure 11B(b) shows Example 3. Table 3 shows the compression characteristics data calculated based on the measurement results. [Table 3]

[0076] Comparing Examples 1-3 with Comparative Example 1, the elastic modulus decreased as the crossing angle increased. The decrease compared to Comparative Example 1 was approximately 1.7%, 9.4%, and 18% for crossing angles of 5°, 10°, and 15°, respectively. It can be seen that the decrease in elastic modulus was smaller when the crossing angle was 5° and 10°.

[0077] On the other hand, fracture strain tended to increase as the value of the crossing angle increased. The decrease in compressive strength compared to Comparative Example 1 was approximately 3.9%, 4.5%, and 7.6% for crossing angles of 5°, 10°, and 15°, respectively, confirming that the decrease in compressive strength due to the increase in fracture strain was smaller than the decrease in elastic modulus. In particular, the decrease in compressive strength was within 5% for crossing angles of 5° and 10°, indicating that the compressive strength was almost the same as that of Comparative Example 1.

[0078] Furthermore, when the crossing angle was 15°, there was a difference of approximately 10% between the rate of decrease in elastic modulus and compressive strength. This confirmed the effect of suppressing the decrease in compressive strength by increasing the fracture strain despite a significant decrease in elastic modulus. The tendency for fracture strain to increase as the crossing angle increases is thought to be due to the rotation of the orientation of the reinforcing fibers caused by the axial compressive load.

[0079] Comparing Example 1 with Comparative Example 2, in the case of Comparative Example 2, which has a thicker fiber reinforcement layer, the fracture strain is smaller and the compressive strength is lower, indicating that the rotation of the reinforcing fiber orientation increases as the layer thickness decreases. It is thought that thinning the reinforcing fiber layer strengthens the restraining effect between adjacent layers and increases damage tolerance, which in turn increases the degree of rotation of the reinforcing fiber orientation. In other words, it is thought that by reducing the thickness of the fiber reinforcement layer constituting the laminated molded body, the occurrence of initial damage such as cracks in the matrix resin and the resulting delamination is suppressed, the tolerance for rotation of the reinforcing fiber orientation increases, and as a result the fracture strain increases.

[0080] Next, Table 4 shows the data on the compression characteristics of the pseudo-isotropic laminated bodies, calculated based on the measurement results of Examples 4-6 and Comparative Example 3. [Table 4]

[0081] Comparative Example 3 is a typical pseudo-isotropic laminated structure, where the angles in the four axial directions of the laminate are 0°, ±45°, and 90°, and the lamination ratio for each axis is often set to 25%. In contrast, Examples 4 to 6 are laminated with fiber-reinforced layers formed by reinforcing fiber groups intersecting at predetermined intersection angles from opposite sides of the axial direction, similar to Examples 1 to 3. While this suppresses the decrease in elastic modulus and increases the fracture strain, a comparison between Examples 4 to 6 and Comparative Example 3 shows that there is almost no change in elastic modulus, while the fracture strain is significantly increased.

[0082] The fact that the decrease in elastic modulus has hardly changed is likely due to the significant influence of the restraining effect caused by the thinning of the fiber reinforcement layer. Furthermore, the restraining effect of adjacent fiber reinforcement layers tends to be stronger as the angle between layers increases. For example, comparing the case where a 90° layer and a 0° layer are adjacent to one case where a 90° layer and a 45° layer are adjacent, the restraining effect is greater in the former case. This is because when a load is applied to the 90° layer in a direction perpendicular to the reinforcing fibers (0° direction), the 0° layer, where the fiber length direction of the reinforcing fibers of the adjacent layer is in the same direction as the load direction, can withstand a larger load than the 45° layer, resulting in less strain in the 90° layer.

[0083] In Comparative Example 3, the angle between adjacent layers is always a constant 45°, and is uniform in the thickness direction. On the other hand, in Example 4, in addition to the 45° angle in the axial direction, the prepreg sheets are shifted by 10° within the fiber reinforcement layer, resulting in an overall interlayer angle of 55°, which is larger than in Comparative Example 3. Therefore, it is thought that a high restraint effect is exhibited throughout the laminated molded body due to the restraint effect within the fiber reinforcement layer and the restraint effect due to the larger interlayer angles, resulting in a larger fracture strain.

[0084] Furthermore, it can be seen that the compressive strength of Examples 4 to 6 is improved compared to Comparative Example 3. The increase in compressive strength was approximately 7.3% at a crossing angle of 5°, approximately 8.3% at 10°, and approximately 0.7% at 15°. In the case of crossing angles of 5° and 10°, it is thought that the rigidity of the fiber reinforcement layer was maintained at a high level considering the compressive characteristics of the prepreg sheet, resulting in improved compressive strength.

[0085] As shown in Comparative Example 3, in the case of a typical pseudo-isotropic laminated body, the fracture strain under compressive load is smaller compared to Examples 4-6. This compressive characteristic is thought to be due to buckling and kinking of the reinforcing fibers under compressive load, resulting in a significantly smaller fracture strain compared to that under tensile load.

[0086] In contrast, as shown in Examples 4-6, when a compressive load is applied in the 0° direction, the absence of a fiber reinforcement layer set in the fiber length direction in the same direction as the load delays the occurrence of initial damage such as buckling and kinking, resulting in a larger fracture strain. Consequently, the compressive strength is also improved, and brittle damage behavior is suppressed. [Industrial applicability]

[0087] As described above, the laminated molded body according to the present invention has a structure in which fiber-reinforced layers are laminated in which the fiber length directions of the reinforcing fiber groups are set to intersect each other from opposite sides in the axial direction with respect to the axial direction in which they are arranged. Therefore, compared to conventional laminated molded bodies, it is possible to improve the compression characteristics and apply it as a structural material, and it is also expected to be widely applied as other industrial materials. [Explanation of symbols]

[0088] F...Laminated molded body, AP...Fiber-reinforced layer, P...Prepreg sheet, S...Fiber length direction, T...Axial direction, TR...Resin layer

Claims

1. A laminated molded body formed by laminating and integrating fiber-reinforced layers, each containing a large number of aligned reinforcing fibers, arranged in multiple axes, wherein at least one fiber-reinforced layer arranged in one axis direction contains a plurality of reinforcing fiber groups, and the fiber length directions of at least two of the reinforcing fiber groups are set to intersect each other from opposite sides with respect to the axis direction of arrangement.

2. The laminated molded body according to claim 1, wherein the intersection angle of the fiber length direction of the reinforcing fiber group with respect to the axial direction in which it is arranged is set to 20° or less.

3. The laminated molded body according to claim 1 or 2, wherein the fiber-reinforced layer is set such that the fiber length direction of the reinforcing fiber group intersects symmetrically with respect to the axial direction in which it is arranged.

4. The laminated molded body according to claim 1 or 2, wherein the group of reinforcing fibers consists of a prepreg sheet with a layer thickness of 10 μm to 80 μm in which the reinforcing fibers, which are aligned, are dispersed in a matrix resin material, and the fiber reinforcement layer is integrally formed by laminating a plurality of the prepreg sheets so that the fiber lengths of the reinforcing fibers intersect.

5. The laminated molded article according to claim 1 or 2, wherein a resin layer is laminated between at least some of the fiber-reinforced layers.

6. A laminated sheet arranged axially for manufacturing the laminated molded article according to claim 1 or 2, wherein a plurality of prepreg sheets having a layer thickness of 10 μm to 80 μm, in which the reinforcing fibers are dispersed in a matrix resin material, are laminated together so that the fiber length direction of the reinforcing fibers intersects with the axial direction.

7. The laminated sheet according to claim 6, wherein a resin layer is laminated.

8. A laminated tape formed by cutting the laminated sheet described in claim 6 to a predetermined width along the axial direction.

9. A method for manufacturing a laminated sheet arranged axially to produce a laminated molded article according to claim 1 or 2, comprising stacking a plurality of prepreg sheets having a layer thickness of 10 μm to 80 μm, each containing a large number of reinforcing fibers arranged in a matrix resin material, such that the fiber length direction of the reinforcing fibers intersects the axial direction, thereby laminating and integrating them into a sheet.

10. A method for manufacturing a laminated sheet according to claim 9, wherein a resin sheet is superimposed on at least a portion of the space between the superimposed prepreg sheets.

11. A method for manufacturing a laminated tape arranged axially to produce a laminated molded body according to claim 1 or 2, comprising: stacking multiple prepreg sheets having a layer thickness of 10 μm to 80 μm, each containing a large number of reinforcing fibers arranged in a matrix resin material, such that the fiber length direction of the reinforcing fibers intersects the axial direction, thereby laminating and integrating them into a sheet to form a laminated sheet; and cutting the laminated sheet to a predetermined width along the axial direction.

12. A method for manufacturing a laminated tape according to claim 11, wherein a resin sheet is superimposed on at least a portion of the space between the superimposed prepreg sheets.

13. A method for manufacturing a laminated molded body, comprising cutting the laminated sheet described in claim 6 to a predetermined size, arranging the cut laminated sheets in a multi-axial direction and laminating them, and integrally molding the laminated laminated sheets.

14. A method for manufacturing a laminated molded body, comprising cutting the laminated tape described in claim 8 to a predetermined length, arranging the cut laminated tape so that its longitudinal direction is multiaxial, laminating the pieces, and integrally molding the laminated laminated tape.

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