JP2023097542A - Method for manufacturing preform with three-dimensional shape configured by multiple preform elements - Google Patents

Abstract

To provide a preform that does not spoil dimensional accuracy of a molded body after molding by restraining shape change of a preform element and the shape change of the preform after assembling while restraining wrinkles generated caused by a difference in peripheral lengths.SOLUTION: A preform has three or more preform elements. A first preform element has a corner. A third preform element has a recess that fits the corner to eliminate springback even after assembling. In order to shape without generating wrinkles, the preform contains a thermosetting resin and reinforcing fibers divided by cutting in, and the shaping is divided into two steps of a pre-shaping step and a main shaping step according to a shaping temperature of a base material, a curvature and a bending angle of the corner of the preform element, to shape a precursor of the preform element for each sheet of release paper of a carrier. By specifying the bending angle of a bending portion of the preform element and the curvature of the corner, each preform element can be aligned without being displaced during assembly.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a prepreg preform mainly composed of reinforcing fibers and a thermosetting resin, which can be subjected to autoclave molding, press molding, and the like. More specifically, according to the present invention, it is particularly easy to manufacture a fiber-reinforced resin molded article having a three-dimensional shape, and a molded article having a complicated shape can be obtained. The present invention relates to a preform made of prepreg, which can be suitably used for aircraft members and automobile structural materials.

Fiber-reinforced resins are lightweight, high-strength, and high-rigidity, so they are used in a wide range of fields, such as sports and leisure applications such as fishing rods and golf shafts, and industrial applications such as automobiles and aircraft. For the production of the fiber-reinforced resin molded product, for example, a resin transfer molding method (RTM method) in which the matrix resin is injected into the space in the reinforcing fiber base material to which the matrix resin is not attached (dry reinforcing fiber base material) and impregnated. ) (for example, Patent Document 1). However, manufacturing costs are high, such as large-scale capital investment in base material processing and manufacturing. Therefore, from the viewpoint of manufacturing cost, a method of using a prepreg, which is an intermediate material obtained by impregnating a resin-impregnated fiber reinforcing material made of long fibers such as reinforcing fibers, as a reinforcing fiber sheet is preferably used.

A molded article made of fiber-reinforced resin can be obtained by cutting the prepreg into a desired shape, laminating, shaping, and press-molding or autoclave-molding the prepreg. In order to mold a preform made by laminating and shaping prepregs into a desired three-dimensional shape, a manufacturing method in which a plurality of preform elements are combined and molded via a preform having the approximate shape of a molded product. There is also (for example, patent document 2). However, when the preform element before assembly is formed into a desired shape, there is a problem that wrinkles are generated due to the difference in peripheral length between the base material and the mold. In order to suppress wrinkles, a technique of shaping the base material while applying tension to the preform element to shape it into a desired shape while eliminating the difference in the circumference of the base material (for example, Patent Document 3), or a technique of forming the base material in advance. There is a technique of forming a shape while suppressing tension of reinforcing fibers by making cuts in the material (for example, Patent Document 4). In addition, there is also a technique to suppress wrinkles by weakening the interlayer adhesive strength only in the bent portion to allow the interlayer to slide.

Republished WO2008/090911 Republished WO2018/147324 JP 2014-73580 A Republished WO2017/159567 Republished WO2021/106070

However, even in preform elements shaped by these conventional techniques, springback occurs in the reinforcing fibers in the base material during transportation or storage, and the shape changes before molding, resulting in a decrease in dimensional accuracy after molding. Further, there is a problem that it is difficult to align the preform elements with each other when assembling them, and that the shape of the preform changes after assembly due to the springback of the reinforcing fibers.

Accordingly, an object of the present invention is to focus on the above-described problems and to suppress the shape change of the preform element and the shape change of the preform after assembly while suppressing wrinkles caused by the difference in circumference. To manufacture a preform that does not impair the dimensional accuracy of a molded body after molding.

A preform and a method for manufacturing the same of the present invention for solving the above problems have the following configurations.
[1] A method for manufacturing a preform by combining at least three or more preform elements using a prepreg composed of a thermosetting resin and reinforcing fibers divided by cuts, and comprising at least the following (1) to (6) ) A method for manufacturing a preform having the step of
(1) A lamination step of laminating the prepregs to obtain a preform element precursor (2) Laminating the preform element precursor along a first shaping mold so that the resin viscosity in the prepreg is 10 Pa s or more Preforming step (3) of obtaining a first preform element precursor having a corner portion with a radius of curvature R1 (mm), which is heated until softened to 500 Pa·s or less and bent at a bending angle θ1 (°). The first preform element precursor is placed along the second shaping mold, the pressure is reduced to 0.1 MPa or less, and the viscosity of the resin in the prepreg is cooled to 500 Pa s or more. Obtaining a first preform element having a corner portion (R1>R2) with a radius of curvature R2 (mm) bent at θ2 (°: θ1≧θ2 and 90°≧θ2) Bonding step (5) of combining the second preform element and the third preform element precursor heated until the resin viscosity in the reform element is softened to 10 Pa·s or more and 500 Pa·s or less; third preform element forming a recess having a curvature radius of R3 (mm: R3≧R2) in the precursor to form a recess as a third preform element (6) forming a third preform to which the second preform element is joined The corner portions of the first preform element are fitted into the concave portions of the reform element, and the pressure is reduced to 0.1 MPa or less and heated until the resin viscosity in the prepreg softens to 10 Pa·S or more and 500 Pa·s or less. [2] In the (1) laminating step and (2) preforming step, and further in the steps (2) and (3), the prepreg is formed together with the release cover carried by the prepreg. A method for manufacturing a preform according to [1], wherein the preform is shaped.
[3] The preform manufacturing method according to [1] or [2], wherein the radius of curvature R1 (mm) is 8 mm or more and 10 mm or less, and the radius of curvature R2 (mm) is 2 mm or more and 4 mm or less.

According to the preform and its manufacturing method according to the present invention, it is possible to provide a preform element that does not generate wrinkles, suppresses shape change due to springback, can be aligned with high accuracy, and furthermore, has shape change due to springback even after assembly. By suppressing the , it is possible to provide a three-dimensional molded product at low cost without lowering the dimensional accuracy.

FIG. 4 is a schematic diagram of the preform after assembly; (a) A front view of the first shaping die in the pre-shaping step, and (b) a front view of the second shaping die in the main shaping step. Schematic diagram of a first preform element, comprising (a) a preform element precursor before bending deformation, (b) a preform element along the first shaping die in the pre-shaping step, (c) shows the preform element aligned with the second shaping die in this shaping step; FIG. 3 is a schematic diagram of assembled second preform elements and third preform elements, (a) second preform elements and third preform elements joined in the joining step; 3 shows a third preform element recessed with a radius of curvature in the recessing step of FIG.

When a three-dimensional complex shape is desired as a molded product using a fiber reinforced resin, generally, a plurality of cut bodies cut into the desired shape are laminated and laminated to form a preform element precursor. A preform is formed by combining shaped preform elements. The preform of the present invention has at least three or more preform elements, at least one preform element (defined as a first preform element in the present invention) has a corner portion, and at least one preform element has a corner portion. Since one preform element (defined as a third preform element in the present invention) has a recess for fitting the corner portion, springback is eliminated even after assembly.

In addition, it is characterized by containing reinforcing fibers divided by thermosetting resin and cuts for shaping without wrinkles, and shaping is performed by adjusting the resin viscosity range in the base material, that is, the shaping temperature, the preform element It is characterized in that the preform element precursor is shaped together with the release liner of the carrier in two stages, a pre-shaping process and a main shaping process, according to the curvature of the corner portion and the bending angle of the bent portion. Furthermore, by defining the bending angles of the bent portions of the preform elements and the curvatures of the corner portions, the preform elements can be aligned without misalignment during assembly.

Next, details of embodiments of the present invention will be described.

[Prepreg]
The prepreg used in the present invention is composed of reinforcing fibers and thermosetting resin.

Continuous fibers, for example, can be used as the reinforcing fibers constituting the prepreg. A preform made of prepreg using continuous fibers as reinforcing fibers can be exemplified as a high-strength structure because the strength of the fibers can be easily utilized when the molded product is exposed to a load. The prepreg using continuous fibers includes a unidirectional prepreg in which the continuous fibers are arranged in the same direction, a woven fabric prepreg in which the continuous fibers are woven, or a braid in which the continuous fibers are woven and impregnated with a resin. can be exemplified.

In prepregs using continuous fibers as reinforcing fibers, a prepreg with a plurality of incisions across the continuous fibers is used (hereinafter, such a prepreg is referred to as an incision-inserted prepreg). From the viewpoint of mechanical properties, it is more preferable to cut the unidirectional prepreg and use it as a cut-inserted prepreg. In addition, the incision-inserted prepreg can be used as a cut body in combination with a normal prepreg in which the reinforcing fibers are continuous fibers and are not incised.

When the cut-inserted prepreg is shaped, openings and deviations are likely to occur at the cut-inserted locations, and the extensibility of the prepreg in the direction of the reinforcing fibers is improved. In addition, the springback after shaping is suppressed by splitting the fibers. During compression molding, the incision insertion point is opened by the flow and the fiber bundles of the reinforcing fibers are separated from each other, so that the prepreg exhibits flexibility and fluidity is enhanced. By making the prepreg flowable in this way, the reinforcing fibers reach the ends of the molded product, and the area where the resin is excessive is reduced, and a molded product with excellent mechanical properties and appearance can be obtained. From the viewpoint of fluidity, it is preferable that the cuts are formed in the entire thickness direction of the prepreg.

The length of the reinforcing fibers cut by cutting is preferably 3 mm or more and 100 mm or less, more preferably 5 mm or more and 75 mm or less, and still more preferably 10 mm or more and 50 mm or less. By making the length of the reinforcing fiber equal to or greater than the lower limit of the above preferred range, the molded product exhibits sufficient mechanical properties. On the other hand, by making the length of the reinforcing fiber equal to or less than the upper limit of the preferred range, each constituent element of the preform element precursor can obtain sufficient fluidity during molding.

The cut length varies depending on the angle formed by the cut direction and the main axis direction of the reinforcing fibers of the prepreg, but the projected length of the reinforcing fibers in the direction orthogonal to the fibers is preferably 0.05 mm or more and 25 mm or less, and more preferably. is 0.1 mm or more and 10 mm or less, more preferably 0.15 mm or more and 5 mm or less. By setting the cut length to the lower limit value or more of the above preferred range, the opening amount of the cut insertion portion is increased, and the constituent elements of the preform element precursor exhibit sufficient fluidity. On the other hand, by setting the cut length to the upper limit value or less of the preferable range, opening of the cut insertion portion is suppressed, and a molded product excellent in appearance quality and mechanical properties can be obtained.

The volume content of the reinforcing fibers preferable for the prepreg is preferably 40% or more and less than 80%, more preferably 45% or more and less than 75%, and still more preferably 50% or more and less than 70%. As described above, the unidirectional prepreg and the incision-inserted prepreg are excellent in filling efficiency of the reinforcing fibers, and therefore are suitable for drawing out the reinforcing effect of the reinforcing fibers, and are effective in improving the rigidity of the molded product. be.

The amount of reinforcing fibers contained in the prepreg is preferably 50 g/m ² or more and less than 1000 g/m ² in terms of basis weight of reinforcing fibers in the case of forming a sheet. In a prepreg whose precursor is a small piece obtained by impregnating a reinforcing fiber bundle with a thermosetting resin or a chopped fiber bundle, if the basis weight is too small, voids in which no reinforcing fiber exists may occur in the plane of the prepreg. By setting the basis weight to be equal to or higher than the lower limit of the above preferred range, it becomes possible to eliminate the voids that are weak points in the fiber-reinforced resin. Further, if the basis weight is less than the upper limit of the preferred range, heat can be uniformly transferred to the inside during preheating for molding. The basis weight is more preferably 100 g/m ^{2 or more and less than 600 g/m 2} , still more preferably 150 g/m ^{2 or} more and less than 400 g/m ² in order to achieve both structural uniformity and heat transfer uniformity. be. The basis weight of the reinforcing fiber is measured by cutting out a 10 cm square region from the reinforcing fiber sheet, measuring the mass, and dividing by the area. The measurement is performed 10 times for different parts of the reinforcing fiber sheet, and the average value is adopted as the basis weight of the reinforcing fiber.

As the prepreg, a prepreg containing a portion where the reinforcing fibers are not impregnated with the thermosetting resin can also be used. Here, the non-impregnated portion means a portion where the thermosetting resin is not adhered to the surface of the reinforcing fiber. A portion of the prepreg that is not impregnated with a resin is impregnated with a thermosetting resin that has flowed from another portion through compression molding such as press molding, and can exhibit desired characteristics as a sound portion.

Examples of reinforcing fibers used in prepreg include carbon fiber, glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, metal fiber, natural fiber, and mineral fiber. A species or two or more species can be used in combination. Among them, carbon fibers such as polyacrylonitrile (PAN)-based, pitch-based, and rayon-based carbon fibers are preferably used from the viewpoint of high specific strength and high specific rigidity and weight reduction effect. In addition, from the viewpoint of enhancing the conductivity of the resulting molded product, reinforcing fibers coated with a metal such as nickel, copper, or ytterbium can also be used.

Thermosetting resins used in prepregs include, for example, various resins such as unsaturated polyester resins, vinyl ester resins, epoxy resins, phenol resins, urea-melamine resins, maleimide resins and polyimide resins, copolymers thereof, Examples include modified products and resins in which at least two of these are blended. Among them, an epoxy resin is preferably used from the viewpoint of the mechanical properties of the resulting molded product.

It is desirable to use a prepreg carried by a release cover. By supporting the prepreg with a mold release cover, it is possible to prevent the resin of the prepreg from adhering to the hand or the conveying device during transportation. Molded articles with favorable mechanical properties are obtained because the shape change of the precursor can be prevented. Materials for the release cover include, for example, polyolefin, polyester, polyester, polypropylene, fluororesin films, and release paper, but are not particularly limited.

In the shaping process, from the viewpoint of adhesion between the prepreg and the release cover, it is preferable to shape the prepreg together with the release cover carrying the prepreg. In the present invention, the prepreg carried by the release paper was used. The adhesion between the prepreg and the release paper, that is, the peel strength, can be set to a desired value by applying a known method for adjusting the amount of surface resin of the prepreg, the type of coating agent on the release paper, the amount of adhesion, and the amount of heat treatment. A preferable range is 50 to 2000 mN/25 mm. If the peel strength is too low, wrinkles will occur when the release paper is lifted from the substrate, and if it is too high, the release paper itself will peel off when peeled from the preform. It remains as a foreign matter during molding and deteriorates mechanical properties.

The peel strength between the prepreg and the release paper is measured by the following known method. A sheet-like prepreg carrying a release paper is cut into strips having a width of 25 mm and a length of 300 mm with the direction of the carbon fibers as the length direction to obtain a test piece. Next, the test piece is attached to a stainless steel support with a bending angle of 165° using a double-sided adhesive tape large enough to cover the entire test piece (for example, double-sided tape T4000 manufactured by Sony Chemicals Co., Ltd., width 50 mm). , with the release paper facing out. Attach another support to the lower chuck (fixed) of the tensile tester, and attach the peeled end of the release paper, which has been peeled off from the prepreg by about 10 mm in advance, to the upper chuck (movable) via a clip and metal wire. , 23° C. and 50% RH, the release paper is pulled at a tensile speed of 200 mm/min to separate from the prepreg, and the load at that time is recorded on a chart. Five peak points of the load are read from the highest point, and five points of the bottom point of the load are read from the lowest point. As the tensile tester, for example, a universal tensile tester such as Tensilon UTM-4L manufactured by Toyo Baldwin Co., Ltd. can be used.

The thickness of the release cover is desirably 50 to 100 μm or less. If it is too thin, the stiffness will be low, and the release paper itself will wrinkle, leading to wrinkles in the preform element.

[Preform Element Precursor]
The preform element precursor presented in the present invention indicates a prepreg laminate or roll obtained in a step prior to shaping (pre-shaping step). A preform element precursor is formed into a desired shape to form a preform element.

[First preform element]
The first preform elements proposed by the present invention are the parts that make up the preform. They are positioned outwardly within the preform after assembly to form the desired three-dimensional shape. A preform element precursor obtained by laminating prepregs is bent and deformed in a pre-shaping step and a main-shaping step to form a corner portion.

[Second preform element]
The second preform elements proposed by the present invention are the parts that make up the preform. In order to form the desired three-dimensional shape, they are arranged so that they are positioned outwardly within the preform after assembly. The presence or absence of corner portions is not particularly limited. The shape is not particularly limited.

[Third preform element]
The third preform element proposed by the present invention is the parts that make up the preform. In order to determine the assembly position of the first preform element and the second preform element, and play a role of positioning and fastening, it is arranged so as to contact the first preform element and the second preform element. be. Further, since it plays a role of a stopper when the first preform element springs back after assembly, it is desirable to have a shape having a concave portion with a curvature along the corner portion when assembling the first preform element. Therefore, as the preform element precursor for obtaining the third preform element, it is desirable to use a prepreg wound into a roll. It is possible to adjust the corner portion of the molded product to a desired curvature without causing voids.

[preform]
The preform proposed in the present invention is formed by assembling preform elements. A molded article can be obtained by curing the preform by press molding, autoclave molding, OoA molding, or the like.

A method for manufacturing a preform using the prepreg described so far will be described below. A preform manufacturing method according to the present invention includes the following steps (1) to (6).
(1) A lamination step of laminating the prepregs to obtain a preform element precursor (2) Laminating the preform element precursor along a first shaping mold so that the resin viscosity in the prepreg is 10 Pa s or more Preforming step (3) of obtaining a first preform element precursor having a corner portion with a radius of curvature R1 (mm), which is heated until softened to 500 Pa·s or less and bent at a bending angle θ1 (°). The first preform element precursor is placed along the second shaping die, the pressure is reduced to 0.1 MPa or less, and the viscosity of the resin in the prepreg is cooled to 500 Pa s or more. (°: θ1≧θ2 and 90°≧θ2) to obtain a first preform element having a corner portion (R1>R2) with a radius of curvature R2 (mm) (main shaping step (4) preform element) Bonding step (5) third preform element precursor by heating until the viscosity of the resin inside softens to 10 Pa s or more and 500 Pa s or less, and combining the second preform element and the third preform element precursor forming a recess having a radius of curvature of R3 (mm: R3≧R2) in the third preform element to form a recess (6) forming a third preform element to which the second preform element is joined; The corner portion of the first preform element is fitted in the concave portion of, and heated under a reduced pressure of 0.1 MPa or less until the resin viscosity in the prepreg softens to 10 Pa S or more and 500 Pa S or less, Assembly process for integration Each process will be described below.

[Cutting process]
The cut body used in the present invention is obtained by cutting a sheet-like prepreg into a predetermined shape or by arranging tape-like prepreg in the shape of a cut body. Preferred examples of the form of the prepreg include a wide sheet-like article, a narrow tape-like article, and a form obtained by laminating a plurality of these.

[Lamination process]
When one preform element precursor is composed of a plurality of prepregs, it is preferable that the fiber directions of the layers of the prepregs are made to be the same, because the fluidity in the direction perpendicular to the fibers during molding is improved. On the other hand, when the fiber directions of the layers of the prepreg constituting one cut body are different from each other, the fiber-reinforced resin is reinforced in a plurality of directions, exhibiting favorable mechanical properties. Therefore, it is also preferable that the plurality of prepreg layers are arranged such that the fiber orientations of two adjacent prepreg layers are different from each other, at least in part. Among them, fiber-reinforced resins generally have better mechanical properties in the direction of the fibers than in the direction perpendicular to the fibers, so it is preferable, for example, to arrange the fibers of two adjacent layers of prepreg so that the fibers are oriented perpendicular to each other. When the fiber directions of, for example, two adjacent prepreg layers among the prepreg layers consisting of multiple layers are arranged orthogonally to each other, the fiber orthogonal direction of one layer and the fiber direction of the other layer are the same direction, so it is favorable. Mechanical properties can be efficiently expressed. At this time, it is desirable that the release cover on the surface of the outermost layer of the preform element precursor is not peeled off so as not to deteriorate the handling property in the next step.

[Preforming process]
In the step of bending and deforming the preform element precursor along the first shaping die into the approximate shape of the first preform element, the preform element precursor is bent at a bending angle θ1 (°) and has a curvature radius of A corner portion of R1 (mm) is formed. The radius of curvature R1 (mm) is preferably 8 mm or more and 10 mm or less. The bending angle θ1 (°) is not particularly limited. Thus, it is possible to provide a wrinkle-free preform element without lifting between prepreg layers.

Preferably, the preform element precursor is heated to soften the viscosity of the resin in the precursor to 10 to 100 Pa·s before shaping. If the resin viscosity remains too high, the preform element will be too stiff to deform to the desired shape. If the viscosity of the resin becomes too low, it will soften and collapse, making it impossible to form the desired shape. In addition, as the resin hardens, it does not conform to the mold during molding, resulting in molding defects. Incidentally, it is preferable to set the heating temperature of the first shaping mold by calculating the resin viscosity in advance from the obtained resin viscosity curve by heating and measuring the resin constituting the preform in advance. The viscosity curve of the resin in the prepreg is measured using ARES-G2 manufactured by TA Instruments at a frequency of 3.14 rad/sec and a heating rate of 1.7° C./min.

At this time, it is desirable that the release cover on the surface of the outermost layer of the preform element precursor is not peeled off, but is shaped while being supported. , wrinkles are generated, and the surface quality is impaired.

The first shaping mold may have a corner portion with a bending angle θ1 (°) and a curvature R1 (mm) in accordance with the shaping shape, and the size and other shape are not particularly limited, but the preform element In order to bend the precursor at a desired position, it is preferable to have a positioning mechanism such as a groove or a step for hooking the preform element precursor. In addition, the material is not particularly limited, but since it is preferable that it has high thermal conductivity to the proform element precursor, for example, an aluminum alloy or a copper alloy can be used. It is desirable to have

The shaping method includes automatic devices such as an air system and a magnetic force system, and manual shaping, but is not particularly limited. In the present invention, as shown in FIG. 3, the end of the preform precursor is hooked on the positioning mechanism of the heated first shaping die and fixed along the shaping die, and the portion in contact with the corner of the shaping die is used as the starting point. , the floated precursor on the opposite side can be shaped by stroking multiple times to obtain a substantially shaped preform element.

[Main shaping process]
This shaping step is a step of shaping the substantially shaped preform element obtained in the pre-shaping step along a second shaping mold into a first preform element. is bent at a bending angle θ2 (°) to form a corner portion with a radius of curvature R2 (mm). The bending angle θ2 (°) is preferably 90° or less, and the curvature radius R2 The curvature (mm) is also preferably smaller than the curvature radius R3 (mm) of the recess in the finally obtained preform, that is, the corner portion of the third preform element. If the bending angle θ2 (°) is 90° or more, or if the radius of curvature R2 (mm) is larger than the radius of curvature R3 (mm), the first preform element is caught by other preform elements in the assembly process, It will not fit properly.

By shaping along the second shaping die different from the first shaping die at room temperature, the cooling time of the shaping die itself is omitted, and the cooling time of the preform element is shortened. be able to.

At this time, by cooling the preform element and the second shaping mold in a sealed space while reducing the pressure to 0.1 MPa or less, the interlayer air inside the preform element precursor that did not escape during lamination is removed, The shape can be adjusted by making the layers adhere to each other.

By cooling the preform element and solidifying the resin viscosity in the preform element to 100 Pa·s or more and making the interlayers adhere to each other, it is possible to obtain a preform element that is difficult to spring back. As in the pre-shaping step, the cooling temperature is determined by isothermally measuring the resin constituting the preform in advance, calculating backward from the obtained resin viscosity curve, and cooling the preform element in a temperature range where the resin viscosity is 100 Pa s or more. It should be demolded.

At this time, as in the pre-shaping step, it is desirable to carry the release cover on the surface of the outermost layer of the preform element without peeling it off.

The second shaping die may have a corner portion with a bending angle θ2 (°) and a curvature R2 (mm) in accordance with the shaping shape, and the size and other shapes are not particularly limited.

As with the second shaping die, the material is not particularly limited, but it is preferable that the proform element has high thermal conductivity, so aluminum alloys and copper alloys, for example, can be used.

[Joining process]
The third preform element precursor is heated to a temperature range where the viscosity of the resin in the preform element is 10 to 500 Pa·s and joined to the heated second preform element. At this time, the release cover is peeled off only at the joints of the respective preform elements. In order to join, it is important that the preform elements that have been joined once do not come off, and the heating method is not particularly limited. Another method is to join the preform elements on a heated fixture.

In addition, as described above, in order to determine the positional relationship of all preform elements when the position of the third preform element is assembled, it is preferable to mark and position the second preform element to be joined. The marking method is not particularly limited as long as it does not affect the molding. For example, a fine cut or a marker such as a resin piece may be made in the second preform element for positioning.

[Recess forming step]
For softening the resin viscosity in the second preform element and the third preform element combined in the joining process to 10 to 500 Pa s and fitting the first preform element in the assembly process, A recess having a radius of curvature R3 (mm) is formed in the third preform element. Although the method of forming the recess is not particularly limited, for example, a corner portion having a desired shape can be formed by pressing a jig having a circular cross section with a curvature radius of R3 (mm) against the third preform element. Furthermore, it is preferable to form the recess by shaping the third preform element with the cylindrical jig while reducing the pressure to 0.1 MPa or less in a closed space. In order to avoid deformation or flow of each preform element in the preform during assembly or molding and change in shape, the inside of the third preform element, which serves as a positioning mechanism, should be tightly adhered between layers. is desirable. If the second preform element or the third preform element has a complicated shape and is likely to spring back, the mold may be removed after the resin viscosity is set to 1000 Pa·s or more.

[Assembly process]
The corner portions of the first preform element obtained in the shaping step are fitted into the recesses of the second preform element and the third preform element obtained in the recess forming step. Only the part where each preform element joins is peeled off the release cover. After combining, the viscosity of the resin in the preform is softened again to 10 to 500 Pa·s while the pressure is reduced to 0.1 Mpa or less in a closed space, and the layers are adhered to each other, then cooled and removed from the mold. At this time, the preform may be assembled along the second shaping mold.

Next, the preform elements, preforms and moldings thereof according to the present invention will be described in more detail with reference to examples. The evaluation methods used in the examples of the present invention are as follows.

[Surface Quality of First Preform Element]
The maximum unevenness difference Rt (μm) of the outermost layer of the first preform element formed by bending the preform element precursor at a bending angle of 90° was measured to evaluate the surface quality. The maximum unevenness difference Rt (μm) increases due to uneven thickness due to wrinkles and resin unevenness when the release cover is peeled off. As a standard, if Rt≦80 μm, the surface quality is judged to be good. The maximum unevenness difference Rt (μm) was calculated from an undulation curve measured in accordance with JISB 0601:2013 in a direction perpendicular to the orientation direction of the carbon fibers. As the contact-type surface roughness measuring instrument, for example, a surface roughness measuring instrument SE-3500 manufactured by Kosaka Laboratory Co., Ltd. is used. A device that can be measured at 7 mN was used, and the measurement was performed by traveling 20 mm at a measurement speed of 2 mm/sec.

[Dimensional Accuracy of First Preform Element]
A first preform element formed by bending a preform element precursor at a bending angle of 90° was allowed to stand for 10 minutes, and the amount of change in bending angle was evaluated. It was considered that the greater the bending angle, the greater the shape change due to springback. It was judged that assembly could be performed without any problem if the amount of change in angle was 15° or less.

[Dimensional accuracy of preform after assembly]
After assembling the first preform element, the second preform element and the third preform element and leaving them for 10 minutes, the dimensions of three sides were measured, and the deviation between the measured values and the desired dimensions was evaluated. bottom. If the degree of deviation was within 5%, it was determined that the dimensional accuracy was good.

[Molded product evaluation]
Visual observation of the surface appearance of the molded product and microscopic observation of the inside were carried out and evaluated according to the following criteria. For internal observation, VHX6000 manufactured by Keyence was used.
◯: The surface has uniform smoothness, and there are no defects such as fiber buckling, voids, or microcracks inside.
x: Surface smoothness is uneven, or the above defects are present inside.

The prepregs used in Examples and Comparative Examples are as follows.

[Prepreg]
As the prepreg, a unidirectional prepreg using Torayca T800 yarn and 3900 series epoxy resin was used. This prepreg is referred to as prepreg A, and the properties of prepreg A are as follows.
・Carbon fiber density: 1.80 g/cm ³
・Resin content: 35%
・Thickness: 0.17mm
・Release cover: Release paper with a thickness of 50 μm is carried on the back side

[Incision insertion prepreg]
Using an automatic cutting machine for the prepreg, the average cut length (the projected length of the reinforcing fiber in the direction perpendicular to the fiber) is 0.24 mm, and the angle formed by the cutting direction and the main axis direction of the reinforcing fiber of the prepreg is 14 °. By inserting the cuts, a cut-inserted prepreg in which the cut reinforcing fibers had an average length of 25 mm was produced. Note that the cut was made to penetrate the prepreg in the thickness direction. This prepreg was designated as prepreg B. The properties other than the cut were the same as those of the prepreg A described above.

[Lamination structure]
The stack configuration of the first preform element precursor and the second preform element precursor was [45/-45/0/90] _s . The third preform element precursor varied between the examples and comparative examples.

(Example 1)
The prepreg (B) is cut to 80 mm × 300 mm, laminated so that the lamination structure is [45/0/-45/90] _s , a first preform element precursor, a second preform element precursor was made. [45/0/−45/90] Each number in _s is the angle between the longitudinal direction of the preform element precursor and the main axis direction of the reinforcing fibers, with the longitudinal direction of the preform element precursor being the direction of 0°. Represents the size (°), "s" is prepared by repeating the combination in [ ] and laminating in the reverse order, and laminating them so that they are symmetrical indicates Further, when obtaining the preform element precursor, the prepreg was laminated while peeling off the unnecessary release cover from the prepreg so that the release paper was left only on the front and back surfaces of the outermost layer.

Subsequently, the prepreg (B) was cut into a size of 50 mm×300 mm and wound so that the circumferential direction was 90° to the fiber direction to produce a roll-shaped third preform element precursor.

First, the first preform element precursor was preshaped along a first shaping die heated to 60° C. and having corner portions with a bending angle θ1=90° and a curvature R1=10 mm.

Next, the first preform element obtained in the pre-shaping step was held at room temperature, and was placed along a second shaping die having a corner portion with a bending angle θ2 = 80° and a curvature R2 = R4 mm. , This shaping was carried out by reducing the pressure to 0.1 MPa or less in a closed space.

As a result, the surface of the first preform element had no wrinkles, the maximum unevenness difference Rt (μm) was 20 μm, and the surface quality was ◯.

Furthermore, as a result of measuring the amount of change in the bending angle θ2 (°) of the first preform element, it was suppressed to 11°, and the dimensional accuracy of the first preform element was also good.

Here, the second preform element precursor obtained in the lamination step was used as a preform element as it was, and a cut line was made to mark the position where the third preform element precursor was to be joined. A third preform element precursor was bonded to the marked position of the second preform element on a tool plate heated to 60°C.

Furthermore, a columnar jig with a curvature R3 = 8 mm was placed along the third preform element precursor, and the pressure was reduced to 0.1 MPa or less in a sealed space to form corners with a curvature R3 = 8 mm. A recess was formed.

The corner portion with a curvature R2 = 4 mm of the first preform element obtained in the main shaping step is fitted into the recess with a curvature R3 = 8 mm of the third preform element obtained in the recess forming step. let me A closed space was formed on a tool plate heated to 60° C., and the pressure was reduced to 0.1 MPa or less for assembly.

As a result, the deviation of the preform dimensions from the desired dimensions was suppressed to 3% or less at the maximum, and the preform dimensional accuracy was also good.

The obtained preform was molded in an autoclave, and the cross section of the molded product after 100% curing was observed. As a result, it was confirmed that there were no voids or cracks inside the molded product, and no buckling of the fiber layer. The result was also 0.

(Example 2)
The prepreg (B) was cut, laminated and wound up in the same manner as in Example 1 to obtain first, second and third preform element precursors.

Next, the first preform element precursor was pre-shaped along a first shaping die heated to 60° C. and having corner portions with a bending angle θ1=90° and a curvature R1=8 mm.

Next, the first preform element obtained in the pre-shaping step was held at room temperature and was placed along a second shaping die having a corner portion with a bending angle θ2 = 80° and a curvature R2 = 2 mm. , This shaping was carried out by reducing the pressure to 0.1 MPa or less in a closed space.

As a result, the surface of the first preform element had no wrinkles, the maximum unevenness difference Rt (μm) was 22 μm, and the surface quality was ◯.

Furthermore, as a result of measuring the amount of change in the bending angle θ2 (°) of the first preform element, it was suppressed to 10°, and the dimensional accuracy of the first preform element was also good.

Here, the second preform element precursor obtained in the lamination step was used as a preform element as it was, and a cut line was made to mark the position where the third preform element precursor was to be joined. A third preform element precursor was bonded to the marked position of the second preform element on a tool plate heated to 60°C.

Furthermore, a columnar jig with a curvature R3 = 8 mm was placed along the third preform element precursor, and the pressure was reduced to 0.1 MPa or less in a sealed space to form corners with a curvature R3 = 8 mm. A recess was formed.

The corner portion of the first preform element having a curvature of R2 = 2 mm obtained in the main shaping step is fitted into the recess of the third preform element having a curvature of R3 = 8 mm obtained in the recess forming step. let me A closed space was formed on a tool plate heated to 60° C., and the pressure was reduced to 0.1 MPa or less for assembly.

As a result, the deviation of the preform dimensions from the desired dimensions was suppressed to a maximum of 2% or less, and the preform dimensional accuracy was also good.

The resulting preform was molded in an autoclave, and the cross section of the molded product after 100% curing was observed. As a result, it was confirmed that there were no voids or cracks inside the molded product, and no buckling of the fiber layer. was also 0.

(Comparative example 1)
The prepreg (A) was cut and laminated in the same manner as in Examples to obtain first and second preform element precursors. A third preform element precursor was laminated with [0/90] _20S in a pyramidal configuration.

Next, pre-shaping and main shaping were carried out in the same manner as in Example 2. At this time, the release paper supporting the outermost layer of the preform element precursor was peeled off, and an FEP film was used as a backing paper for shaping.

As a result, unevenness in the amount of resin occurred on the surface of the first preform element, the maximum unevenness difference Rt (μm) was 100 μm, and the surface quality was x.

Furthermore, bonding, recess formation, and assembly were carried out in the same manner as in Example 2.

As a result, the first preform element did not fit well, and the dimensions of the preform deviated from the desired dimensions by 6% at maximum, so the preform dimensional accuracy was x.

The resulting preform was molded in an autoclave, and the cross section of the molded product after 100% curing was observed. was confirmed, the molded product internal evaluation result was also x.

(Comparative example 2)
The prepreg (B) was cut, laminated and wound up in the same manner as in Example 2 to obtain first, second and third preform element precursors.

Next, the first preform element precursor is preshaped along a first shaping die heated to 60° C. and having corner portions with a bending angle θ1=90° and a curvature R1: 2 mm, The main shaping was carried out with the first shaping die as it was.

As a result, wrinkles were generated from the bent portion of the first preform element, the maximum unevenness difference Rt (μm) was 500 μm, and the surface quality was x.

Furthermore, as a result of measuring the amount of change in the bending angle θ2 (°) of the first preform element, it was suppressed to 8°, and the dimensional accuracy of the first preform element was ◯.

Furthermore, as a result of carrying out bonding, recess formation, and assembly in the same manner as in Example 2, the dimensions of the preform deviated from the desired dimensions by a maximum of 8% due to the wrinkles on the surface of the first preform element causing the assembly position to shift. , the preform dimensional accuracy was ×.

The resulting preform was molded in an autoclave, and the cross section of the molded product after 100% curing was observed. As a result, it was confirmed that there were no voids or cracks inside the molded product, and no buckling of the fiber layer. was 0.

(Comparative Example 3)
The prepreg (B) was cut, laminated and wound up in the same manner as in Example 2 to obtain first, second and third preform element precursors.

Next, preshaping was carried out in the same manner as in Example 2, and then the first preform element obtained in the preshaping step was held at room temperature, bending angle θ2 = 80°, curvature R2 = Main shaping was carried out along a second shaping mold having a corner portion of 2 mm without reducing the pressure.

As a result, the maximum unevenness difference Rt (μm) on the surface of the first preform element was 23 μm, and the surface quality was ◯. , the dimensional accuracy of the first preform element was x.

Furthermore, as a result of performing bonding, recess formation, and assembly in the same manner as in Example 2, the dimensions of the preform did not fit well due to the springback of the first preform element, and deviated from the desired dimensions by up to 13%. , the preform dimensional accuracy was x.

The resulting preform was molded in an autoclave, and the cross section of the molded product after 100% curing was observed. As a result, it was confirmed that there were no voids or cracks inside the molded product, and no buckling of the fiber layer. was 0.

(Comparative Example 4)
A first preform element was obtained by cutting and laminating the prepreg (B) in the same manner as in Example 1, followed by pre-shaping and main shaping.

As a result, the maximum unevenness difference Rt (μm) on the surface of the first preform element was 20 μm, and the surface quality was ◯. Further, since the amount of change in the bending angle θ2 (°) was also 10°, the dimensional accuracy of the first preform element was ◯.

Here, the second preform element precursor was used as a preform element as it was, and the position where the first preform element precursor was to be joined was marked with a cut line.

The corners of the first preform element with a curvature R2 = 2 mm obtained in the above main shaping step are joined along the marking positions of the second preform element, and on a tool plate heated to 60 ° C. , a closed space was formed, and the pressure was reduced to 0.1 MPa or less for assembly.

As a result, the first preform element buckled and the dimensions of the preform deviated from the desired dimensions by 10% at the maximum, so the preform dimensional accuracy was x.

The obtained preform was molded in an autoclave, and the cross section of the molded product after 100% curing was observed.

These results are summarized in Table 1.

Applications of molded articles obtained using the preform of the present invention include, for example, aircraft parts such as joint members such as stringers in automobiles and aircraft.

11 first preform element precursor 12 pre-shaped first preform element 13 main-shaped first preform element 4 release cover
5 first shaping die 6 second shaping die 7 bagging film 8 heat source

Claims (3)

A method for manufacturing a preform by combining at least three or more preform elements using a prepreg composed of a thermosetting resin and reinforcing fibers divided by cuts, the method comprising at least the following steps (1) to (6). A method for manufacturing a preform having
(1) A lamination step of laminating the prepregs to obtain a preform element precursor (2) Laminating the preform element precursor along a first shaping mold so that the resin viscosity in the prepreg is 10 Pa s or more Preforming step (3) of obtaining a first preform element precursor having a corner portion with a radius of curvature R1 (mm), which is heated until softened to 500 Pa·s or less and bent at a bending angle θ1 (°). The first preform element precursor is placed along the second shaping mold, the pressure is reduced to 0.1 MPa or less, and the viscosity of the resin in the prepreg is cooled to 500 Pa s or more. Obtaining a first preform element having a corner portion (R1>R2) with a radius of curvature R2 (mm) bent at θ2 (°: θ1≧θ2 and 90°≧θ2) Bonding step (5) of combining the second preform element and the third preform element precursor heated until the resin viscosity in the reform element is softened to 10 Pa·s or more and 500 Pa·s or less; third preform element forming a recess having a curvature radius of R3 (mm: R3≧R2) in the precursor to form a recess as a third preform element (6) forming a third preform to which the second preform element is joined The corner portions of the first preform element are fitted into the concave portions of the reform element, and the pressure is reduced to 0.1 MPa or less until the resin viscosity in the prepreg softens to 10 Pa·s or more and 500 Pa·s or less. Assembly process that heats and integrates 2. The method of manufacturing a preform element according to claim 1, wherein in the (1) lamination step and the (2) pre-shaping step, the prepreg is shaped together with a release cover carried by the prepreg. 3. The method of manufacturing a preform according to claim 1, wherein the curvature radius R1 (mm) is 8 mm or more and 10 mm or less, and the curvature radius R2 (mm) is 2 mm or more and 4 mm or less.

Images