JP2010018723A - Incised prepreg substrate, prepreg layered product, and fiber-reinforced plastic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a prepreg substrate having sufficient flowability and molding followability of a complex shape and exhibiting excellent dynamic physical property applicable to a structure material, low ununiformness property and excellent dimension stability when it is made to a fiber-reinforced plastic, a layered product of the prepreg substrate, and a fiber-reinforced plastic obtained by solidifying the layered product. <P>SOLUTION: A plurality of intermittent incised parts are inserted to the whole surface of the prepreg substrate comprising a carbon fiber aligned in one direction and a matrix resin containing a thermosetting resin as a main component with a predetermined angle and projection length in a direction crossing the carbon fiber. The incised prepreg substrate is divided such that all carbon fibers become substantially the predetermined carbon fiber length by the incised parts. The incised prepreg substrate is provided with the predetermined CAI strength, dent depth and tensile strength. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a prepreg base material that has good fluidity and molding followability, and exhibits excellent mechanical properties applicable to structural materials, its low variation, and excellent dimensional stability when it is made into a fiber reinforced plastic. And a laminate thereof, and a fiber reinforced plastic obtained by solidifying the laminate. More specifically, for example, the present invention relates to a prepreg base material that is an intermediate base material of fiber reinforced plastic suitably used for aircraft members and the like, a laminate thereof, and a fiber reinforced plastic obtained by solidifying the laminate.

  Fiber reinforced plastic consisting of reinforced fiber and matrix resin is attracting attention in industrial applications because it has high specific properties, high specific modulus, excellent mechanical properties, weather resistance, chemical resistance, etc. The demand is increasing year by year.

  As a method for molding fiber reinforced plastics with high functional properties, a semi-cured intermediate base material impregnated with a matrix resin is laminated on a continuous reinforcing fiber called a prepreg base material, and an autoclave (high temperature and high pressure kettle) is used. Autoclave molding in which a matrix resin is solidified by heating and pressurizing to form a fiber reinforced plastic is most commonly performed. In recent years, for the purpose of improving production efficiency, RTM (resin transfer molding) molding, in which a continuous fiber base previously shaped into a member shape is impregnated with a matrix resin and solidified, has been performed. The fiber reinforced plastics obtained by these molding methods have excellent mechanical properties because they are continuous fibers. Further, since the continuous fibers are regularly arranged, it is possible to design the mechanical properties required by the arrangement of the base material, and the variation in the mechanical properties is small. However, on the other hand, since it is a continuous fiber, it is difficult to form a complicated shape such as a three-dimensional shape, and it is mainly limited to members close to a planar shape. In addition, when a foreign object collides with the fiber reinforced plastic, the inside of the fiber reinforced plastic is damaged, but the dent is not easily generated in the damaged part, and it is difficult to find the damaged part only by visual inspection. there were.

  On the other hand, as a molding method suitable for a complicated shape such as a three-dimensional shape, there is SMC (sheet molding compound) molding. SMC molding is performed by heating and pressurizing a semi-cured SMC sheet obtained by impregnating a chopped strand cut to about 25 mm with a matrix resin, which is a thermosetting resin, using a heating press. In many cases, before pressing, the SMC sheet is cut smaller than the shape of the molded body, placed on a mold, and stretched (flowed) into the shape of the molded body by pressing to perform molding. Therefore, it is possible to follow a complicated shape such as a three-dimensional shape by the flow. In addition, by using short fibers, the amount of dents at the foreign object collision portion is increased as compared with fiber reinforced plastic using continuous fibers. However, since SMC inevitably causes distribution unevenness and orientation unevenness of chopped strands in the sheeting process, the mechanical properties deteriorate or the variation of the values increases. Furthermore, due to uneven distribution and alignment unevenness of the chopped strands, warpage, sink marks and the like are likely to occur particularly in a thin member, which may be unsuitable as a structural material.

In order to fill the drawbacks of the above-described materials, a base material that can flow and reduce the variation in mechanical properties by cutting into a prepreg base material composed of continuous fibers and a thermoplastic resin is disclosed ( For example, Patent Documents 1 and 2). However, compared with SMC, the mechanical properties are greatly improved and the variation is small, but it cannot be said that the strength is sufficient for application as a structural material. Compared with a continuous fiber base material, since it has a configuration including a defect called a notch, the notch which is a stress concentration point becomes a starting point of fracture, and in particular, there is a problem that tensile strength and tensile fatigue strength are lowered.
Japanese Unexamined Patent Publication No. 63-247010 Japanese Patent Laid-Open No. 9-254227

  In view of the background of such prior art, the present invention has good fluidity and molding followability of a complicated shape, and when it is made of fiber reinforced plastic, it is easy to visually confirm the foreign matter collision point and is applied to a structural material. An object of the present invention is to provide a prepreg base material that exhibits possible excellent mechanical properties, low variation thereof, and excellent dimensional stability, a laminate thereof, and a fiber-reinforced plastic obtained by solidifying the laminate.

The present invention employs the following means in order to solve such problems. That is, in a prepreg base material composed of carbon fibers aligned in one direction and a matrix resin mainly composed of a thermosetting resin, a plurality of intermittently in a direction crossing the carbon fiber over the entire surface of the prepreg base material. A notch is inserted, the absolute value Θ of the angle between the notch and the carbon fiber is in the range of 2 to 25 °, and the projected length Ws obtained by projecting the notch in the vertical direction of the carbon fiber is Within the range of 0.1 to 1.5 mm, substantially all the carbon fibers are divided by the incision, and the fiber length L of the carbon fibers divided by the incision is in the range of 10 to 100 mm. The thickness H of the prepreg base material into which the cuts are inserted is 30 to 300 μm, the fiber volume content Vf is in the range of 45 to 65%, and the prepreg base material into which the cuts are inserted is designated as ASTM. D7137 / D7137M- In a laminated structure according to 05, using an autoclave, the pressure was 6 kg / cm ² , the temperature was increased from 25 ° C. at a temperature increase rate of 1.5 ° C./min, and reached 180 ° C. and held for 2 hours to cure the resin, When molded into a flat fiber reinforced plastic described in ASTM D7137 / D7137M-05, the CAI strength measured according to ASTM D7137 / D7137M-05 is 200 to 400 MPa, and the dent depth is 0.18 to 2 mm. It is a cut prepreg base material that is expressed and further exhibits a tensile strength of 450 to 850 MPa measured according to JIS-7073 (1988).

  Further, the prepreg base is formed by stacking a plurality of prepreg base materials in which carbon fibers are aligned in one direction, and the carbon fibers are aligned in one direction. The material is molded into a predetermined shape using the prepreg laminate in which the fiber directions of the prepreg base material are aligned and integrated in at least two directions, the cut prepreg base material, or the prepreg laminate, A fiber reinforced plastic is preferable.

  According to the present invention, excellent fluid physical properties that can be applied to a structural material, having good fluidity, molding followability of complex shapes, and making it easy to visually confirm the location of a foreign object collision when used as a fiber reinforced plastic. In addition, a prepreg base material that exhibits low variation and excellent dimensional stability, a laminate thereof, and a fiber reinforced plastic obtained by solidifying the laminate can be obtained.

  The present inventors have excellent fluidity, molding followability of complicated shapes, and when used as a fiber reinforced plastic, a prepreg base material that exhibits excellent mechanical properties, low variation, and excellent dimensional stability. In order to obtain As a result, as a prepreg base material, a specific cutting pattern is inserted into a specific base material called a prepreg base material composed of reinforcing fibers and matrix resin aligned in one direction, and the prepreg base material is laminated, It has been clarified that a fiber-reinforced plastic having excellent mechanical properties applicable to structural materials, small variations, and stable dimensional accuracy can be obtained by pressure molding. Further, the fiber reinforced plastic of the present invention is characterized in that the amount of dents at the foreign object collision portion is likely to be large, and the damaged portion is easy to visually identify, and can be applied as an aircraft member that particularly requires such a feature. I found out.

  In this invention, the prepreg base material which consists of matrix resin which has as a main component the carbon fiber and thermosetting resin which were aligned in one direction is used. In addition, the prepreg base material used in the present invention is not completely impregnated in the fiber, in addition to the reinforcing fiber aligned in one direction and the base material in which the reinforcing fiber base material is completely impregnated with the resin. A resin semi-impregnated base material integrated in a state (semi-preg: hereinafter, sometimes referred to as a semi-impregnated prepreg base material) is included. In the prepreg base material according to the present invention, since the reinforcing fibers are aligned in one direction, it is possible to design a molded body having arbitrary mechanical properties by controlling the orientation in the fiber direction.

  Examples of the reinforcing fiber used in the cut prepreg base material of the present invention include organic fibers such as aramid fiber, polyethylene fiber, polyparaphenylene benzoxador (PBO) fiber, glass fiber, carbon fiber, silicon carbide fiber, and alumina. Examples thereof include inorganic fibers such as fibers, Tyranno fibers, basalt fibers, and ceramic fibers, metal fibers such as stainless fibers and steel fibers, and reinforcing fibers that use boron fibers, natural fibers, modified natural fibers, and the like as fibers. Among them, carbon fiber is particularly lightweight among these reinforcing fibers, and has particularly excellent properties in specific strength and specific modulus, and is also excellent in heat resistance and chemical resistance. It is suitable for members such as aircraft and automobiles that are desired to be made. Among these, PAN-based carbon fibers that can easily obtain high-strength carbon fibers are preferable. In the present specification, unless otherwise specified, in terms of fibers or terms including fibers (for example, “fiber direction” and the like), the fibers represent carbon fibers.

  Examples of the matrix resin used for the notched prepreg base material of the present invention include, for example, epoxy resins, unsaturated polyester resins, vinyl ester resins, phenol resins, epoxy acrylate resins, urethane acrylate resins, phenoxy resins, alkyd resins, urethane resins, Thermosetting resins such as maleimide resin and cyanate resin, polyamide, polyacetal, polyacrylate, polysulfone, ABS, polyester, acrylic, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene, polypropylene, polyphenylene sulfide ( PPS), polyetheretherketone (PEEK), liquid crystal polymer, vinyl chloride, polytetrafluoroethylene and other fluororesins, silicone and other thermoplastic resins It is below. Among these, it is particularly preferable to use a matrix resin whose main component is a thermosetting resin. Since the matrix resin is mainly composed of a thermosetting resin, the cut prepreg base material has tackiness at room temperature, and when the base material is laminated, it is integrated with the upper and lower base materials by adhesion, and is intended. It can shape | mold, keeping the laminated structure as it was. On the other hand, in the case of a thermoplastic resin prepreg base material that does not have tack at room temperature, the base materials slip when the prepreg base materials are laminated. It becomes reinforced plastic. In particular, when molding with a mold having an uneven portion, the difference appears remarkably.

  Furthermore, since the incised prepreg base material of the present invention composed of a thermosetting resin has excellent drapability at room temperature, for example, when molding using a mold having an uneven portion, the uneven portion is preliminarily aligned with the unevenness. Pre-shaping can be easily performed. This pre-shaping improves moldability and facilitates flow control.

  Furthermore, in the prepreg base material of the present invention, a plurality of intermittent cuts are inserted in the direction across the carbon fibers on the entire surface of the prepreg base material, and substantially all the carbon fibers are cut by the cuts. The fiber length L of the carbon fiber divided by the cut is in the range of 10 to 100 mm, and the absolute value Θ between the cut and the carbon fiber is in the range of 2 to 25 °. The projected length Ws obtained by projecting the cut in the vertical direction of the carbon fiber is in the range of 0.1 to 1.5 mm, and the thickness H of the prepreg base material into which the cut is inserted is 30 to 300 μm. The fiber volume content Vf is in the range of 45 to 65%. In the present invention, “substantially all of the carbon fibers are divided by the incision” means that the area where the continuous fibers not divided by the incision of the present invention are aligned occupies the prepreg base material area. Indicates less than 5% of the percentage. Hereinafter, unless otherwise specified, a prepreg base material having a cut on the entire surface of the present invention is referred to as a cut prepreg base material.

  In the present invention, the fiber length L is an incision closest to the fiber direction in which an arbitrary incision and an incision equivalent to the arbitrary incision have a projected length Ws projected in the vertical direction of the carbon fiber. It refers to the length of the fiber that is divided by (a pair of cuts). Here, “projection length Ws projected by the cut in the vertical direction of the carbon fiber” is, as shown in FIG. 1, with the cut as the projection plane in the vertical direction of the carbon fiber (vertical direction 2 of the carbon fiber). It refers to the length when projected perpendicularly to the projection plane from the cut (fiber longitudinal direction 1). By making cuts in the entire surface of the prepreg base material and making the fiber length L of the carbon fibers in the base material all 100 mm or less, the fiber can flow during molding, especially in the longitudinal direction of the fiber, making it complicated. Excellent shape following capability. When there is no notch, that is, when only continuous fibers are used, a complicated shape cannot be formed because the fibers do not flow in the fiber longitudinal direction. When the fiber length L is less than 10 mm, the fluidity is further improved. However, even if other requirements are satisfied, the high mechanical properties necessary as a structural material cannot be obtained. Considering the relationship between fluidity and mechanical properties, it is more preferably in the range of 20 to 60 mm. There are also fibers shorter than the fiber length L that is cut and divided other than the pair of cuts, but the fewer the fibers of 10 mm or less, the better. More preferably, the area where the fibers of 10 mm or less are aligned is smaller than 5% of the ratio of the prepreg base material area.

  Further, it is a major feature of the present invention that the absolute value of the angle Θ formed by the notch and the carbon fiber is in the range of 2 to 25 °. Even if the absolute value of Θ is larger than 25 °, fluidity can be obtained, and higher mechanical properties can be obtained as compared with conventional SMC, etc., but in particular, when the absolute value of Θ is 25 ° or less. Significant improvement in mechanical properties. On the other hand, if the absolute value of Θ is smaller than 2 °, sufficient fluidity and mechanical properties can be obtained, but it is difficult to make a stable cut. That is, when the incision lies on the fiber, the fiber easily escapes from the blade when making the incision, and in order to make the fiber length L 100 mm or less, the absolute value of Θ is more than 2 ° If it is small, at least the shortest distance between the cuts will be less than 0.9 mm, resulting in poor production stability. In addition, when the distance between the cuts is small as described above, there is a problem that handling at the time of stacking becomes difficult. In view of the relationship between the ease of controlling the cutting and the mechanical characteristics, it is more preferably in the range of 5 to 15 °. Note that Θ in the present invention means that when an arbitrary point on the cut is a point X, if the angle formed by the fiber longitudinal direction and the cut at the point X is θ (X), Θ is θ (X ) Is the average value on the notch, that is, the value given by (Equation 1). Here, as shown in FIG. 8, the end points of the incision are point A and point B, the points A and B are connected, the curve along the incision is C, and the curve C at the point X is very small. The line segment is ds.

  The length Ws projected in the vertical direction of the carbon fiber is preferably in the range of 30 μm to 100 mm. When Ws is 30 μm or less, it is difficult to control the cutting, and it is difficult to ensure that L is 10 to 100 mm over the entire surface of the prepreg base material layer. That is, if there is a fiber that is not cut by cutting, the fluidity of the base material is remarkably lowered. However, if a large amount of cutting is made, there is a problem that a portion where L is less than 10 mm appears. Furthermore, when trying to insert a cut by pressing the blade against the prepreg base material, the carbon fiber may meander in the direction perpendicular to the fiber at the time of cutting and escape from the blade, so that the fiber may not be cut well. In order to reduce the influence of such fiber escape, Ws is preferably 0.1 mm or more. More preferably, by setting Ws to 0.2 mm or more, it becomes possible to insert the cut into the prepreg base material without leaving more continuous fibers.

  On the other hand, from the viewpoint of mechanical properties, the length Ws projected in the vertical direction of the carbon fiber is preferably 1.5 mm or less. In the present invention, since the absolute value of the absolute value Θ of the angle formed by the cut and the carbon fiber is 2 to 25 °, the projection length Ws can be reduced with respect to the cut length. Therefore, even a very small cut of 1.5 mm or less can be provided industrially stably. By reducing Ws, the amount of fibers cut by each cutting is reduced, and strength improvement is expected. In particular, when Ws is 1.5 mm or less, a great improvement in strength is expected. In addition, the longer the cut length, the easier it is for the base material notches to open during the laminating operation, and the handleability of the base material is greatly reduced. If the cut is 1.5 mm or less, the cut is less likely to open during the laminating operation, and a cut prepreg base material with good substrate handling properties is obtained.

  Moreover, the cut prepreg base material of the present invention may be in close contact with the tape-like support. The notched prepreg base material in close contact with the tape-like support can retain its form even if all the fibers are cut by the incision, and the fibers fall off and fall apart during shaping. No problem. More preferably, the matrix resin is a thermosetting resin having tackiness. Here, the tape-like support includes papers such as kraft paper, polymer films such as polyethylene / polypropylene, metal foils such as aluminum and the like, and in order to obtain releasability from the resin, silicone. A surface or “Teflon (registered trademark)” type release agent, metal vapor deposition, or the like may be applied to the surface.

  In the fiber reinforced plastic obtained by laminating a plurality of the cut prepreg base materials of the present invention and molding them while pressing, the cut openings are very small or the cut openings are not formed. This is the greatest feature of the present invention.

  This feature will be described with reference to FIGS. As a comparison of the present invention, FIG. 2 shows a laminate 10 in which a cut prepreg base material 7 having an absolute value of an angle Θ between the cut 4 and the fiber 3 of 90 ° is laminated a), and the laminate 10 is shown in FIG. The molded fiber reinforced plastic 11 is shown in b) in a plan view in which the layers derived from the cut prepreg base material 7 are respectively close-up and a cross-sectional view in which the AA cross section of the plan view is cut out. As shown in a), the cut prepreg base material 7 is provided with a cut perpendicular to the fiber on the entire surface, and the cut 4 penetrates the thickness direction of the layer. By setting the fiber length L to 100 mm or less, fluidity is ensured, and the fiber reinforced plastic 11 whose area is easily extended from the laminate 10 can be easily obtained by press molding or the like (however, the thickness is reduced). When the elongated fiber reinforced plastic 11 is obtained as in b), the short fiber layer 12 derived from the cut prepreg base material 7 extends in the vertical direction of the fiber, and the region where the fiber does not exist (cut opening) ) 13 is generated. This is because carbon fibers generally do not expand at a pressure of the molding level. In the case of FIG. 2, the cut openings 13 are generated for the extended length, for example, 250 × 250 mm laminates 10 to 300. When the fiber reinforced plastic 11 of × 300 mm was obtained, the total area of the cut openings 13 was 50 × 300 mm, that is, 1/6 (about 16.7 (about 16.7) with respect to the surface area of the fiber reinforced plastic 11 of 300 × 300 mm. %) Is the calculation for the cut opening. As shown in the cross-sectional view, the region 13 is occupied by the substantially triangular resin-rich portion 16 and the region in which the adjacent layer has intruded. Therefore, when the laminated body 10 using the cut prepreg base material 7 is stretched and formed, the undulation 17 of the layer and the resin rich portion 16 are generated at the fiber bundle end portion 15, which causes deterioration of mechanical properties and surface quality. Affects decline. In addition, since the rigidity is different between the part where the fiber is present and the part where the fiber is not present, the fiber-reinforced plastic 11 is in-plane anisotropic, and design is difficult due to problems such as warping. Further, in terms of strength, the fiber oriented to about ± 10 ° or less from the load direction transmits most of the load, but the fiber bundle end 15 must redistribute the load to the adjacent layer 14. Don't be. At that time, as shown in FIG. 2b), when the fiber bundle end 15 is perpendicular to the load direction, stress concentration is likely to occur, and peeling is also likely to occur. Therefore, the strength improvement cannot be expected so much.

  In FIG. 3, the laminated body 10 which laminated | stacked an example of the cut prepreg base material of this invention is a), the fiber reinforced plastic 11 which shape | molded the laminated body 10 is b), respectively, and the cut prepreg base material 7 origin A top view of the layers close-up is shown. As shown in a), the cut prepreg base material 7 is provided with intermittent cuts 4 having an absolute value of the angle Θ between the fibers 3 of 25 ° or less and the cuts 4 are in the layer thickness direction. Through. By making the fiber length L to be 100 mm or less over the entire surface of the cut prepreg base material 7 by the cuts 4, the fiber reinforced plastic 11 whose area is easily extended from the laminate 7 by press molding or the like is secured. Can be obtained. By reducing the cut length and the absolute value of the angle between the cut and the carbon fiber, the projected length Ws obtained by projecting the cut in the vertical direction of the carbon fiber can be made 1.5 mm or less. When the stretched fiber reinforced plastic 11 is obtained as in b), the short fiber layer 12 derived from the cut prepreg base material 7 does not stretch in the fiber direction when stretched in the vertical direction of the fiber. Is generated, the adjacent short fiber group flows in the vertical direction of the fiber, thereby filling the cut opening 13 and reducing the area of the cut opening 13. Become. This tendency is particularly noticeable when the projection length Ws obtained by projecting the cut in the vertical direction of the carbon fiber is 1.5 mm or less, and the cut opening 13 is not substantially generated. The area on the surface of the layer can be in the range of 0.1 to 10% compared to the surface area of the layer. Therefore, it is possible to obtain a high-strength and high-quality fiber-reinforced plastic 11 without layer undulation or resin-rich portion without adjacent layers intruding in the thickness direction. Since the fibers 3 are arranged all over the surface, there is no difference in rigidity in the surface, and the design can be easily applied as in the conventional continuous fiber reinforced plastic. The epoch-making effect of filling the cut opening with the vertical flow of the fiber to obtain a fiber-reinforced plastic without layer undulations is that the absolute value of the absolute value Θ between the cut and the carbon fiber is 25 ° or less. In addition, the projection length Ws obtained by projecting the cut in the vertical direction of the carbon fiber can be obtained for the first time to 1.5 mm or less. More preferably, when Ws is 1 mm or less, higher strength and higher quality can be achieved.

  More preferably, in the outermost layer of the fiber reinforced plastic, the area of the cut opening is substantially zero. The area of the cut opening is “substantially 0”, but it is desirable that the opening does not exist, but the area of the cut opening in the outermost layer is 1% or less compared to the surface area of the fiber reinforced plastic. If so, it means that there is no problem. If the absolute value of Θ is larger than 25 °, a resin-rich part or a region where there is no fiber in the layer, that is, a region where the carbon fiber of the adjacent layer is viewed is generated in the outermost layer. Is difficult. On the other hand, in the present invention, it is difficult to generate a resin-rich portion or a region without fibers, so that it can be applied as an outer plate member.

  Even if the thickness H of the prepreg base material is larger than 300 μm, good fluidity can be obtained. However, since the present invention has a notch, the larger the layer thickness to be divided, the lower the strength. If it is assumed to be applied to a structural material, it is necessary to set it to 300 μm or less. On the other hand, even if H is smaller than 30 μm, fluidity can be maintained and high strength can be obtained. However, since it is very difficult to stably produce an extremely thin prepreg base material, the effect of the present invention can be reduced at a low cost. It is necessary that the thickness is 30 μm or more. In view of the relationship between mechanical properties and cost, the thickness is preferably 50 to 200 μm.

  When the fiber volume content Vf is 65% or less, sufficient fluidity can be obtained. The lower the Vf, the better the fluidity. However, if Vf is less than 45%, the high mechanical properties required for the structural material cannot be obtained. Considering the relationship between fluidity and mechanical properties, it is more preferably in the range of 55-60%.

  Furthermore, it is preferable to provide an additional resin layer having a higher tensile elongation than the matrix resin in the cut prepreg base material on at least one surface of the cut prepreg base material of the present invention. FIG. 5 shows an example in which an additional resin layer made of a thermoplastic resin and a thermosetting resin is provided on both sides of the cut prepreg. The fiber reinforced plastic obtained by laminating and molding the cut prepreg base material of the present invention has a final elongation when cracks generated from within the layers are connected by delamination, so an additional resin layer having a high elongation is provided between the layers. This dramatically reduces delamination and improves strength.

  The additional resin for forming the additional resin layer may be anything as long as it has a higher tensile elongation than the thermosetting resin used as the matrix resin, but it is particularly preferable to use a thermoplastic resin. Thermoplastic resins are known to have higher elongation and fracture toughness values than general thermosetting resins, and effectively exhibit the strength improvement effect of the present invention. Furthermore, polyamide, polyester, polyolefin, and polyphenylene sulfone are preferable in terms of the balance between resin characteristics and cost and the degree of freedom in designing the resin viscosity. As the additional resin has higher compatibility with the matrix resin, the effect of the present invention is exhibited. Therefore, it is preferable that the additional resin has a melting point equal to or lower than the molding temperature. In particular, a polyamide having a low melting point of about 100 to 200 ° C. by copolymerization or the like is excellent in compatibility with a thermosetting resin, and has a high tensile tensile strength, tensile strength, and fracture toughness, and is preferable. When carbon fiber is used as the carbon fiber, epoxy resin is used as the matrix resin, and polyamide resin is used as the additional resin, the most lightweight, high-strength, high-rigidity fiber-reinforced plastic can be obtained.

  About arrangement | positioning of an additional resin layer, it is good not to enter in the layer which a carbon fiber forms, but to arrange | position in layers on the cut prepreg base material surface. The inside of the layer formed by the carbon fibers refers to a cut prepreg base material obtained by impregnating carbon fibers preliminarily aligned with a matrix resin in one direction. By providing the additional resin layer intensively between the layers, the delamination phenomenon can be further suppressed. Further, the additional resin is arranged in a layered form without entering the layer formed by the carbon fiber means that the additional resin is arranged in a mode in which an anchor effect is obtained in the layer formed by the carbon fiber. Although a small amount of additional resin (for example, 20% by volume or less of the total additional resin) has entered the layer formed of carbon fibers by melting or the like (that is, some of the carbon fibers This means that there may be an additional resin of 20% or less by volume of the total additional resin instead of a matrix resin. The form of the additional resin layer may be any form such as a film or non-woven form, and the additional resin layer may be provided uniformly on the entire surface of the prepreg base material, or concentrated on the area covering the cut. Additional resin may be disposed on the surface. Further, it is possible to dispose the additional resin layer only by spraying the particulate additional resin on the surface of the prepreg base material not including the resin layer. At this time, the thickness of the additional resin is preferably larger than the carbon fiber single yarn and smaller than half of the layer thickness H.

The notched prepreg base material is laminated according to ASTM D7137 / D7137M-05, and the temperature is increased from 25 ° C. to 180 ° C. using an autoclave at a pressure of 6 kg / cm ² and a heating rate of 1.5 ° C./min. When the resin is cured by holding for 2 hours and molded into a flat fiber reinforced plastic as defined by ASTM D7137 / D7137M-05, the CAI strength measured according to ASTM D7137 / D7137M-05 is 200 to 400 MPa, And it becomes possible to express the dent depth 0.18-2mm, and also the tensile strength measured according to JIS-7073 (1988) 450-850MPa. The CAI strength and dent depth are measured according to ASTM D7137 / D7137M-05, and the tensile strength is measured according to JIS-7073 (1988). In a fiber reinforced plastic made of continuous fibers without inserting a notch, the CAI strength increases, but the dent depth tends to decrease. On the other hand, in the SMC molded product which is a short fiber reinforced plastic, the dent depth is large, but the CAI strength is low and it is difficult to use as a structural member. The fiber reinforced plastic obtained by laminating and curing the cut prepreg base material of the present invention has both the advantages of high CAI strength and large dent depth, and has characteristics not found in conventional materials. ing. Here, in order to use as a member for automobiles or airplanes that are required to be reduced in weight, it is preferable that the tensile strength is in the range of 450 to 850 MPa and the CAI strength is in the range of 200 to 400 MPa. Further, in view of production stability, the tensile strength is in the range of 500 to 800 MPa, and the CAI strength is in the range of 220 to 320 MPa.

  A material having a high CAI strength and a large dent depth is particularly in demand as an aircraft member. For example, in order to visually recognize (nondestructive) damage caused by impact during assembly of a member or impact received during operation of an aircraft, a recess is formed at a level at which the impacted portion can be visually identified. It is necessary to If the recess is formed at a level where it can be visually observed, and the compressive strength at that time can be predicted and the compressive strength is high enough to withstand operation, it will be shocked during inspection during assembly and maintenance service during operation. It can be judged whether or not it can withstand operation, and it contributes greatly to quality assurance and maintenance of aircraft. That is, it can be said that a material that expresses a dent depth deeply due to a falling weight impact and has a high compressive strength CAI after impact in that state has extremely high suitability as an aircraft member.

  As a method for producing the cut prepreg base material in the present invention, several methods such as a method of cutting the prepreg base material with a blade, a method using a laser cutter or a water cutter can be considered, but the cut prepreg base is inexpensive and has high productivity. If a material is manufactured, a method of inserting a notch by producing a punching die in which a plurality of blades are integrated and pressing the blade against the prepreg base material is effective.

  Moreover, the following two are considered to be particularly useful as specific means for inserting intermittent cuts into the cut prepreg substrate.

  The first is a push cutting method in which a notch is inserted into a prepreg base material by pressing a punching die having a blade disposed on the prepreg base material using a press machine (elevator). FIG. 6 shows a schematic diagram of the push-off method. The push-cut method has good production efficiency, such as a large amount of cuts can be inserted into the prepreg substrate at one time by a single press. Further, the punching die can be easily processed, and the punching die can be produced at a low cost. In addition, as a method of attaching the punching die to the press machine in the press-cutting method, for example, it is preferable to embed the blade in a wooden mold or the like as a base and attach it to the press machine as a punching die. If this method is used, it is easy to produce a punching die, and the amount of protrusion of the blade can be easily adjusted.

  The second is a rotary blade method in which a cutting roller is inserted into a prepreg base material by continuously pressing a rotary roller on which a blade is previously arranged against the prepreg base material. FIG. 7 shows a schematic diagram of the rotary blade method. The rotating blade method is useful because the rotation speed of the roller can be set faster, and the cut prepreg base material can be produced faster than the aforementioned push-cut method.

  In addition, even if it uses any method of a push cutting method and a rotary blade method, it is possible to insert a notch on the same line as the line which is producing the prepreg base material, ie, online. Therefore, when producing the incision prepreg base material of the present invention, for example, it is only necessary to arrange the incision insertion device in the final process of the existing prepreg base material production line, and the incision prepreg base material is produced with little investment. It is possible.

  Further, the shape of the cut inserted into the cut prepreg base material is linear, and the cut length W is preferably in the range of 0.5 mm to 1.5 mm. By making the shape of the cut into a straight line, the shape of the blade necessary for the insertion of the cut becomes a flat shape, so that the labor required for the cutting die is reduced and the manufacturing cost of the die is reduced. Further, as described above, the smaller the cut length is, the more the mechanical strength of the cut prepreg base material is improved. At the same time, the blade length is also reduced, and the durability of the blade is lowered. Further, if the cutting length is 0.5 mm or less, the processing cost of the blade is increased, which is not realistic. In view of the durability of the blade, the cutting length is preferably 0.5 mm or more. On the other hand, if it is intended to reduce the cutting length to such an extent that it has high mechanical strength and does not open during molding, the cutting length is preferably 1.5 mm or less. In view of both side surfaces of the durability and mechanical strength of the blade, the cutting length is more preferably in the range of 0.8 to 1.2 mm.

  In the cut prepreg base material of the present invention, it is preferable that all the carbon fibers divided by the cut have substantially the same fiber length L. Even if the fiber length varies from place to place, the effect of the present invention can be obtained, but by making the fiber length constant, the variation in mechanical properties can be further reduced and uniform substrate flow characteristics can be exhibited. I can do it. In the present invention, “substantially the same fiber length L” means that, among the carbon fibers contained in the cut prepreg base material, the fiber length of the carbon fiber is 3/4 or more by weight. Means L.

  In addition, as a device for preventing continuous fibers from remaining on the cut prepreg base material, in the cut pattern of the cut prepreg base material, as shown in FIG. Thus, a technique of preventing the continuous fibers from remaining is also effective. At this time, a carbon fiber having a fiber length of L or less is present in a part of the cut prepreg base material. Among the carbon fibers contained in the cut prepreg base material, the fiber length is If the carbon fiber of L or less is 1/4 or less in weight, it is expected that variation in mechanical properties will be small and uniform base material flow characteristics can be exhibited.

  Furthermore, it is a laminate comprising the cut prepreg base material of the present invention in at least a part, and a plurality of prepreg base materials in which carbon fibers are aligned in one direction are laminated, and the carbon fibers are unidirectional. It is preferable to prepare a laminated body in which the prepreg base materials aligned in the above are integrated with the fiber directions of the prepreg base materials oriented in at least two directions, and this is used as a base material for molding. By making a prepreg base material into a laminated body, it becomes easy to arrange | position a base material to a shaping | molding die. Note that the effect of the present invention can be expected even when a plurality of the cut prepreg base materials of the present invention are laminated so that the longitudinal direction of the fibers is the same, and the laminated body is made into fiber reinforced plastic by press molding. However, in this fiber reinforced plastic, the strength in the longitudinal direction of the fiber is high, while the strength in the vertical direction of the carbon fiber is low. This is because in the fiber-reinforced plastic of the present invention, the adhesive strength at the resin / fiber interface is much lower than the tensile strength of carbon fiber. Therefore, when a load is applied in the vertical direction of the carbon fiber to the fiber reinforced plastic in which all layers are oriented in the same direction, a force to peel off both at the fiber / resin interface is generated. Breaks at lower load. Therefore, if it is intended to develop high strength regardless of the load direction, it is preferable to make a laminate in which the fiber directions of the prepreg base material are aligned and integrated in at least two directions. As a specific example of a preferable laminate, a laminate in which the fiber longitudinal direction of the prepreg base material of each layer is classified into two directions orthogonal to each other can be considered. This laminated body is useful because isotropic mechanical properties can be expressed even when the number of laminated layers is small. As another specific example of the preferred laminate, when the fiber longitudinal direction of an arbitrary layer contained in the prepreg base laminate is 0 °, the fiber longitudinal direction of the prepreg base contained in the other layer is 45. It is a prepreg base material laminate included in any of °, -45 °, and 90 °. By changing the fiber longitudinal direction in increments of 45 °, more isotropic mechanical properties can be exhibited.

  Furthermore, the laminate described above or a laminate of a plurality of the cut prepreg base materials of the present invention is placed in a heated mold, and the resin is cured by heating under pressure to obtain a fiber reinforced plastic. Good. Only when the resin is cured to obtain a fiber-reinforced plastic, it can be used as a member having high strength and high rigidity while being lightweight.

  The fiber reinforced plastic of the present invention can be applied even when the shape is a smooth surface or a gently curved surface. Furthermore, when a member including a standing surface or a rib shape is formed on a part of the fiber reinforced plastic, the merit of using the cut prepreg base material is great. If the laminated body of continuous fiber prepreg base material is heated and pressed and a member including a standing surface or a rib shape is simply press-molded, the fibers cannot follow the mold shape, or the mold cavity It is very difficult to obtain a molded article of good quality because the fiber is not filled to the end. If the cut prepreg base material of the present invention is used, even if it is a member including a standing surface or a rib shape, it is easy to form a molded article of good quality because the base material exhibits high fluidity during press molding. It is possible to obtain.

  As described above, the fiber-reinforced plastic of the present invention is considered to have extremely high compatibility as an aircraft member. In particular, in a thin fiber reinforced plastic having a thickness of 5 mm or less, the CAI strength at a foreign matter collision point is likely to be lowered, and it is very important how to detect the foreign matter collision point. Reinforced plastics are expected to be very useful. Examples of aircraft members that are relatively thin among aircraft members and for which the fiber-reinforced plastic of the present invention is expected to be applied include skins, stringers, stiffeners, spars, floor beams, ribs, frames, and even doublers. Can be mentioned. In particular, these members often include ribs and standing surface shapes as part of their shapes, and it is expected that the effect of increasing fluidity by inserting cuts into the prepreg base material is great.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the inventions described in the examples.

<Mechanical property evaluation method>
In this example, two mechanical strengths, tensile strength and CAI strength, are measured and used as an index of the strength of the fiber reinforced plastic in the present invention.

(Tensile test method)
A tensile test piece having a length of 250 ± 1 mm and a width of 25 ± 0.2 mm was cut out from the flat fiber-reinforced plastic. According to the test method prescribed in JIS K-7073 (1998), the tensile strength was measured at a crosshead speed of 2.0 mm / min with a distance between the gauge points of 150 mm. In this example, an Instron (registered trademark) universal testing machine 4208 type was used as a testing machine. The number of test pieces measured was n = 5, and the average value was the tensile strength. Further, a standard deviation was calculated from the measured value, and the standard deviation was divided by an average value, thereby calculating a variation coefficient (CV value (%)) as an index of variation.

(CAI test method)
A CAI test piece having a length of 150 ± 0.25 mm and a width of 100 ± 0.25 mm was cut out from the flat fiber-reinforced plastic. The dent depth and CAI intensity were measured according to the test method specified in ASTM D7137 / D7137M-05. The energy of impact given to the panel was 270 in · lb, and the dent depth was measured one day after the impact was given. In this example, an Instron (registered trademark) universal testing machine 4208 type was used as a testing machine. The number of test pieces measured was n = 3, and the average value was the CAI intensity. Further, a standard deviation was calculated from the measured value, and the standard deviation was divided by an average value, thereby calculating a variation coefficient (CV value (%)) as an index of variation.

<Criteria for CFRP evaluation>
In this example and comparative example, three indicators of substrate handling properties, surface quality (incision opening), and substrate fluidity were used. The criteria for each are as follows.

(Handling of substrate)
○: When the incised prepreg base material is lifted with both hands and the base material is further placed on a flat surface, the end of the base material is almost in its original shape.
Δ: When the cut prepreg base material is lifted with both hands and the base material is further placed on a flat surface, the deformation amount of the base material end is less than 2%.
X: When the cut prepreg base material is lifted with both hands and the base material is further placed on a flat surface, the deformation amount of the base material end is 2% or more.

(Surface quality (incision opening))
○: The opening of the cut is hardly observed, the cut cannot be confirmed, or the area of the opening is 5 mm ² or less.
Δ: Of all the cuts existing on the flat plate surface, 20% or less of the cuts are slightly opened, or the area of the opening part of 20% or more of the cuts is less than 5 mm ² .
X: Of all the cuts existing on the flat plate surface, 20% or less of the cuts are slightly opened, or the area of the opening of 20% or more of the cuts is 5 mm ² or more.

(Substrate fluidity)
○: The base material reaches the cavity end of the mold.
(Triangle | delta): The unfilled part exists in the cavity edge part of a metal mold | die, The volume is less than 1% of the cavity of a metal mold | die.
X: An unfilled portion exists at the cavity end of the mold, and the volume thereof is 1% or more of the cavity of the mold.

Example 1
First, a prepreg base material was prepared. Specifically, 100 parts of tetraglycidyl diaminodiphenylmethane (MY720, manufactured by Huntsman Advanced Material Co., Ltd.), 15 parts of polyethersulfone (PES5003P, manufactured by Sumitomo Chemical Co., Ltd.), 4,4′-diaminodiphenyl sulfone (Huntsman) 45 parts of Advanced Material Co., Ltd.) were kneaded, and the resulting resin composition was used as a matrix resin. First, polyethersulfone was heated and dissolved in tetraglycidyldiaminodiphenylmethane, cooled to 70 ° C., and 3,3′-diaminodiphenylsulfone was dispersed therein. The resin prepared by the above means was applied onto release paper using a reverse roll coater so that the coating amount was 45 g / m ² , thereby producing a resin film. Furthermore, carbon fibers (tensile elastic modulus 290 GPa, tensile strength 5900 MPa) aligned in one direction are sandwiched between the resin films from both sides, heated and pressed to impregnate the resin, and the carbon fiber basis weight (CF basis weight) is 190 g / m ² , A prepreg base material having a carbon fiber volume content of 56% was produced.

Next, a particulate thermoplastic resin was sprayed on the surface of the prepreg base material to provide an additional resin layer. Specifically, 90 parts by weight of a polyamide containing 4,4′-diamino-3,3′dimethyldicyclohexylmethane (“Milamide (registered trademark, the same applies hereinafter)”-TR55 manufactured by Mzavelke), epoxy resin (Japan Epoxy Resin) 8 parts by weight of “jER (registered trademark, the same shall apply hereinafter)” 828) and 2 parts by weight of diaminodiphenylmethane (“MDA-220” manufactured by Mitsui Takeda Chemical Co., Ltd.) of 300 parts by weight of chloroform and 100 parts by weight of methanol It added in the mixed solvent and obtained the uniform solution. Next, the solution was made into a mist using a spray gun for coating, and sprayed toward the wall surface of 3000 parts by weight of n-hexane, which was well stirred, to precipitate a solute. The precipitated solid was separated by filtration, washed well with n-hexane, and then vacuum-dried at 100 ° C. for 24 hours to obtain a particulate thermoplastic resin (polyamide particles). This particulate thermoplastic resin was sprayed at 7 g / m ^{2 on} both sides of the prepreg substrate. In this way, an additional resin layer containing a thermoplastic resin was provided on both sides of the prepreg base material. It was 0.19 mm when the thickness of the obtained prepreg base material was measured with digital micro calipers.

  Further, a notch was inserted into the prepreg base material. First, a number of blades were cut out from a metal plate having a size of 500 mm × 500 mm and a thickness of 5 mm, and a punching die for inserting a cut into a prepreg base material was produced. FIG. 4 shows the layout of the cutting blades. A plurality of blades 19 having a length of 1.5 mm are arranged at intervals of 1.5 mm in a region of the central portion 400 × 400 of the punching die 18 to form a row 20 of blades. An angle α (23) formed by the row of blades and the reference direction 21 of the punching die is 20 °. Furthermore, the rows of adjacent blades are arranged at intervals of 15 mm in the reference direction of the punching die, and the rows of adjacent blades are shifted from each other by a half phase in a direction 22 perpendicular to the reference direction. Next, this punching die is attached to a press machine, and the punching die is transferred to the prepreg base material while feeding the prepreg base material so that the reference direction of the punching die and the feed direction of the base material (fiber longitudinal direction of the prepreg base material) coincide. And a cut was inserted into the prepreg substrate. The cutting pattern of the obtained cutting prepreg base material was a pattern in which the blade layout of FIG. 4 was transferred as it was. The surface of the obtained cut prepreg base material is photographed using a digital microscope, printed out so that the magnification becomes 100 times, and the cut length W, the fiber length L, and the projection using a curve ruler. When the length Ws was measured, they were W = 1.5 mm, L = 30 mm, and Ws = 0.51 mm, respectively. Further, the center line of the cut is divided into 20 equal parts, the angle formed by each minute line segment and the fiber longitudinal direction is measured with a protractor, and the average value is defined as the absolute value Θ of the angle formed by the cut and the carbon fiber. , Θ was 20 °.

Furthermore, the above-mentioned cut prepreg base material was laminated | stacked and the cut prepreg laminated body was obtained. First, in the cut prepreg base material produced by the above-described procedure, the size is 250 × 250 mm in the fiber longitudinal direction (0 ° direction) and in the direction shifted 45 degrees to the right from the fiber longitudinal direction (45 ° direction). Cut out. The substrate had tackiness. Next, the cut prepreg base material cut out was laminated on a 16-layer pseudo-isotropic ([−45 / 0 / + 45/90] _2S ) to obtain a 250 × 250 mm cut prepreg laminate. At this time, when the thickness of the laminate was measured using a digital caliper, it was 3.1 mm. A flat plate for tensile testing was produced by press-molding this cut prepreg laminate. After the laminate was placed in the center of a flat plate mold having a 300 × 300 mm cavity, it was cured by a heating press molding machine under a condition of 180 ° C. × 120 minutes under a pressure of 6 MPa. A flat fiber-reinforced plastic with a size of 300 mm was obtained. When the ratio of the area of the base material to the mold area when the mold is viewed from above is defined as the charge rate, the charge rate corresponds to 70%. The obtained fiber reinforced plastic had no fiber undulation, and the fibers were flowing evenly to the end. There is no warpage as a whole, and even in the cut of the outermost layer, there is almost no part where no carbon fiber is present and the carbon fiber of the resin rich part or the adjacent layer is peeking, maintaining good appearance quality and smoothness. It was. Moreover, when the thickness of this flat plate was measured using a digital caliper, it was 2.2 mm. Since the base material extended | stretched by press molding, it has confirmed that the thickness of the shaping | molding board became smaller than the thickness of a laminated body.

  Furthermore, according to the above-mentioned means, the tensile test of the fiber reinforced plastic obtained by press molding was conducted. The tensile modulus of elasticity was 51 GPa, which was almost the theoretical value, and the tensile strength was as high as 650 MPa. The CV value was 5%, which was very small. From these results, it was found that mechanical properties and quality that can be applied to structural materials and outer plate members were obtained. Further, when the obtained fiber-reinforced plastic was cut out and attention was paid to the layer having a cut-out surface of 0 °, there was no layer waviness or no fiber portion, and almost no resin-rich portion was present.

In addition, a CAI test flat plate was formed by autoclave molding, and the CAI test was performed according to the above-described means. In the autoclave, the internal temperature of the autoclave is increased at a heating rate of 2 ° C./min under a pressure of 6 kg / cm ² in the autoclave, and the temperature is maintained for 120 minutes after the internal temperature reaches 180 ° C. By curing the resin, a flat fiber reinforced plastic of 250 × 250 mm was obtained. The plate thickness at this time was 4.5 mm. When the CAI strength and the dent depth were measured for the flat plate thus obtained, the dent depth was as large as 0.24 mm, and even by visually observing the surface of the test piece from a location several meters away. We were able to identify the damaged part. When the cross section of the impact portion was observed, delamination progressed widely in the fiber reinforced plastic using the continuous fiber prepreg base material of Comparative Example 1 to be described later, but in this fiber reinforced plastic, the delaminated region Although it was small, it was confirmed that large deformation occurred in the out-of-plane direction. By inserting a notch into the prepreg base material, it is suggested that the energy absorbed by the impact is not used for delamination but for deformation in the out-of-plane direction, and delamination can be suppressed. Moreover, the CAI strength was a very high value of 270 MPa, and even when compared with the fiber reinforced plastic not containing the notch of Comparative Example 1 described later, the strength comparable to that of the comparative example 1 was exhibited. Therefore, it can be confirmed that the fiber reinforced plastic of the present invention has a unique advantage that a high CAI strength can be exhibited while generating a large dent depth, and it can be confirmed that the fiber reinforced plastic is sufficiently applicable as an aircraft member. .

(Examples 2 to 4) [Incision length (projection length) comparison (Table 1)]
A fiber-reinforced plastic was obtained in the same manner as in Example 1 except that the die used for inserting the cut was changed. Specifically, in Example 1, both the length of the cutting die blade and the interval between the blades were 1.5 mm, but in Example 2, both W = 1 mm (Ws = 0.34 mm), and in Example 3, both W = 3 mm (Ws = 1.0 mm), and in Example 4, both were 4.4 mm (Ws = 1.5 mm).

  The fiber reinforced plastic obtained by press molding had no fiber undulation in any of Examples 2 to 4, and the fibers were flowing evenly to the end. There was no warpage as a whole, and even in the outermost layer incision, there was almost no portion where the resin rich portion or the carbon fiber of the adjacent layer was peeked out, and good appearance quality and smoothness were maintained. Tensile elastic modulus is expressed as 50 to 51 GPa almost as theoretical values. Regarding tensile strength, 660 MPa in Example 2, 610 MPa in Example 3, and 580 MPa in Example 4, both of which are high values, CV of tensile strength The value was 4 to 6%, which was a very small variation. From this result, it was confirmed that the tensile strength was improved as the cut length was reduced. The CAI strength and dent depth were almost the same as those in Example 1.

(Examples 5 to 7) [Comparison of cutting angles (Table 2)]
A fiber-reinforced plastic was obtained in the same manner as in Example 1 except that the die used for inserting the cut was changed. The angle α formed by the row of the blades arranged in the punching die and the reference direction of the punching die is 5 ° (Ws = 0.13 mm) in Example 5 and 10 ° (Ws = 0) in Example 6. .26 mm) and Example 7 was 25 ° (Ws = 0.63 mm).

  All of the fiber reinforced plastics obtained by press molding had no fiber undulations, and the fibers flowed evenly to the ends. In addition, there was no warp, and even in the outermost layer cut, there was almost no part where no carbon fiber was present and the carbon fiber in the resin rich part or the adjacent layer was peeked, maintaining good appearance quality and smoothness. . At any level, the tensile modulus was 50 to 51 GPa, the tensile strength was as high as 600 to 700 MPa, and the CV value of the tensile strength was as small as 5 to 6%. In particular, in Examples 5 and 6 having a small cutting angle, a tensile strength of 650 MPa or more was expressed. The CAI strength and dent depth were almost the same as those in Example 1.

(Examples 8 to 10) [Fiber length comparison (Table 3)]
A fiber reinforced plastic was obtained in the same manner as in Example 1 except that the fiber length L was changed by changing the interval of the cut in the cut pattern of Example 1. L was 10 mm in Example 8, 60 mm in Example 9, and 100 mm in Example 10, respectively.

  The fiber reinforced plastic obtained by press molding had no fiber swell except in Example 8, and the fiber was sufficiently flowing to the end. In Example 8, there was a portion where the fiber did not sufficiently flow to the end at the surface portion where the undulation of the fiber and friction with the mold were received. In addition, none of the fiber reinforced plastic has a warp, and even in the cut of the outermost layer, there is almost no part where the carbon fiber does not exist and the carbon fiber of the resin rich part or the adjacent layer is peeked, and the appearance quality is good. The smoothness was maintained. The tensile elastic modulus was 49 to 50 GPa, the tensile strength was a high value of 600 to 700 MPa, and the CV value of the tensile strength was 4 to 6%, which was a small variation. The CAI strength and dent depth were almost the same as those in Example 1.

(Examples 11 and 12) [Comparison of substrate thickness (Table 4)]
The fiber reinforced plastic is obtained in the same manner as in Example 1 except that the thickness of the cut prepreg base material is changed by changing the carbon fiber basis weight, resin film basis weight, and thermoplastic resin application amount of the prepreg base material of Example 1. It was. In Example 11, the carbon fiber basis weight is 50 g / m ² , the resin film basis weight is 12 g / m ² , and the dispersion amount of the thermoplastic resin is 2 g / m ² , so that the base material thickness is approximately 0.05 mm. A prepreg substrate was obtained. In Example 12, the weight of the carbon fiber per unit area is 300 g / m ² , the basis weight of the resin film is 71 g / m ² , and the spraying amount of the thermoplastic resin is 11 g / m ² . A cut prepreg base material of 3 mm was obtained. In Examples 11 and 12, the ratio of the carbon fiber basis weight, the resin film basis weight, and the dispersion amount of the thermoplastic resin is the same as that in Example 1.

  All of the fiber reinforced plastics obtained by press molding have no fiber undulation, the fibers are sufficiently flowing to the end, no warp, and no carbon fiber is present in the outermost incision. There were almost no portions where the carbon fibers of the rich part or the adjacent layer were peeked, and good appearance quality and smoothness were maintained. The tensile elastic modulus was 50 to 51 GPa in all cases, the tensile strength was as high as 790 MPa in Example 11, and the CV value of the tensile strength was as small as 5%. It was found that the tensile strength was improved by reducing the thickness of the cut prepreg substrate. On the other hand, in Example 12, the tensile strength was 510 MPa, which was slightly lower than the other examples, but the tensile strength tends to be lower as the thickness of the prepreg base material is thicker. Is as strong as a thick prepreg base material having a thickness of 0.3 mm. The cut prepreg base material produced in Example 12 is also useful when it is considered to produce a thick fiber-reinforced plastic with a small number of laminations.

(Examples 13 and 14) [Comparison of fiber content (Table 5)]
A fiber reinforced plastic was obtained in the same manner as in Example 1 except that the fiber volume content Vf was changed by changing the carbon fiber weight per unit area of the prepreg base material of Example 1. In Example 13, the carbon fiber weight per unit area was 221 g / m ² , Vf was 65%, Example 14 was 153 g / m ² , and Vf was 45%.

  In Example 13, the fiber reinforced plastic obtained by press molding had a portion where the fiber did not sufficiently flow to the end at the surface portion where the undulation of the fiber and friction between the mold and the mold were received. On the other hand, in Example 14, the fiber reinforced plastic obtained by press molding had no fiber undulation, and the fiber sufficiently flowed to the end. In addition, both fiber reinforced plastics have no warp, and even in the outermost layer incision, there is almost no part where the carbon fiber is absent and the carbon fiber of the resin rich part or the adjacent layer is peeking, and the appearance quality is good. The smoothness was maintained. Regarding the tensile elastic modulus, it was 59 GPa in Example 13 and 41 GPa in Example 14. Regarding the tensile strength, Example 13 was a high value of 710 MPa, Example 14 was a high value of 540 MPa, and the CV value was also 6 to 7%, showing a small variation. As Vf increased, the tensile modulus and strength were improved. However, when Vf was too large, there was a problem that the fluidity decreased.

(Example 15) [Comparison of cutting methods]
In the cutting pattern of Example 1, instead of shaving the flat metal, the cylindrical metal is shaved and a plurality of blades are provided on the circumference to form a rotary blade roller, and the rotary blade roller is used as a prepreg base material. A cut prepreg base material was obtained by pressing. The used metal roller is a cylindrical roller having an axial length of 40 cm and a diameter of 150 mm. A number of blades were cut out from this roller so as to have the same cutting pattern as in Example 1, and a rotary blade roller was produced. The rotary blade roller and the rubber roller paired with the rotary blade roller were arranged so that the axes of the rollers were parallel and in contact with each other. Furthermore, the notch was inserted into the prepreg base material by feeding the base material between both rollers while rotating both rollers.

  The obtained cut prepreg base material was almost the same as the cut prepreg base material of Example 1, and no clear difference was observed between the two. It was confirmed that the rotary blade method of the present example was also useful as a method for inserting a cut, similar to the press cutting method performed in Examples 1-14.

(Example 16) [Presence / absence of additional resin layer (Table 6)]
A fiber reinforced plastic was obtained in the same manner as in Example 1 except that the thermoplastic particles were not sprayed on the surface of the prepreg substrate.

  When the CAI test of fiber reinforced plastics molded using an autoclave is performed, the CAI strength is 220 MPa, which is lower than that of Example 1, and it can be confirmed that Example 1 is more suitable for aircraft members. It was.

  Hereinafter, a comparative example is shown.

(Comparative Example 1) [Comparison with a prepreg base material without cutting]
Example 1 was the same as Example 1 except that the prepreg base material was not cut.

  The fiber-reinforced plastic obtained by press molding is almost 250 x 250 mm with little flow from the stage of the laminate, and the matrix resin is squeezed out to create resin burrs in the gap with the mold. It was. Because the resin was squeezed out, the surface was squeezed and it seemed impossible to apply it to the product.

  As a result of performing a CAI test on the fiber reinforced plastic obtained by autoclave molding, the CAI strength was as high as 300 MPa, but the dent depth was as small as 0.15 mm. In addition, when the surface of the test piece was visually observed from a distance of about 3 meters, it was difficult to confirm the damaged portion.

(Comparative Examples 2 and 3) [Incision length (projection length) comparison (Table 1)]
A fiber-reinforced plastic was obtained in the same manner as in Example 1 except that the die used for inserting the cut was changed. Specifically, in Example 1, both the length of the cutting die blade and the interval between the blades were 1.5 mm, but in Comparative Example 2, both W = 10 mm (Ws = 3.4 mm), and in Comparative Example 3, In both cases, W = 0.25 mm (Ws = 0.086 mm).

  In Comparative Example 2, the fiber reinforced plastic obtained by press molding had no fiber undulation, the fibers were flowing evenly to the end, and there was no warpage as a whole. However, when the surface of the fiber reinforced plastic was observed, notches were opened, and the surface quality was poor, such as being able to observe the resin pool or the underlying carbon fiber in the opening.

  In Comparative Example 3, in the fiber reinforced plastic obtained by press molding, the fibers did not flow all over the cavity of the mold, and a resin rich portion was observed at the end. Therefore, when the cut prepreg base material is immersed in the organic solvent N-methyl-2-pyrrolidone (NMP), the resin part is dissolved, and the remaining fibers are observed, many continuous fibers with a fiber length exceeding 10 cm remain. It was. It was thought that the reason why the fluidity was deteriorated was that the fibers were not cut well.

(Comparative Examples 4 and 5) [Cutting angle (projection length) comparison (Table 2)]
A fiber-reinforced plastic was obtained in the same manner as in Example 1 except that the die used for inserting the cut was changed. Specifically, in Example 1, both the length of the punch and the distance between the blades were 1.5 mm, but in Comparative Example 4, both α = 2 ° (Ws = 0.05 mm), and in Comparative Example 5, The angle was 45 ° (Ws = 1.1 mm).

  About the comparative example 4, since the cut angle was small, the space | interval of cuts was as small as about 0.5 mm, and there existed difficulty in cutting and lamination | stacking. The fiber reinforced plastic obtained by press molding had some fibers, but the fibers flowed to the end. There was no warp, and even in the cut of the outermost layer, there was almost no part where the carbon fiber was not present and the carbon fiber of the resin rich part or the adjacent layer was peeked, and good appearance quality and smoothness were maintained. The tensile modulus was as high as 51 GPa and the tensile strength was as high as 720 MPa, but the CV value of the tensile strength was as high as 10% and the production stability was lacking.

  On the other hand, in Comparative Example 5, the fiber reinforced plastic obtained by press molding had no fiber undulation, the fibers were flowing evenly to the end, and there was no warpage as a whole. However, when the fiber reinforced plastic surface was observed, the notch was opened, and the resin pool or the underlying carbon fiber could be observed in the opening. The tensile elastic modulus was 49 GPa, which was almost the theoretical value, but the tensile strength was 570 MPa, which was a low value compared to Example 1.

(Comparative Examples 6 and 7) [Fiber length comparison (Table 3)]
A fiber-reinforced plastic was obtained in the same manner as in Example 1 except that the interval in the reference direction between the rows of adjacent blades was changed, that is, the fiber length L of the cut prepreg base material was changed. L was 7.5 mm in Comparative Example 6 and 120 mm in Comparative Example 7, respectively.

  In Comparative Example 6, the fiber reinforced plastic obtained by press molding had a sufficient flow of fibers to the end, but depending on the location, the fibers were wavy or where the cuts were open. I was able to observe. Further, the tensile strength was a high value of 550 MPa, but the CV value was 10%, the variation was large, and the production stability was lacking.

  In Comparative Example 7, in the fiber reinforced plastic obtained by press molding, the fibers did not flow all over the cavity of the mold, and a resin rich portion was observed at the end. It was considered that sufficient fluidity could not be obtained because the fiber length was too large.

(Comparative Examples 8 and 9) [Comparison of layer thickness (Table 4)]
The fiber reinforced plastic is obtained in the same manner as in Example 1 except that the thickness of the cut prepreg base material is changed by changing the carbon fiber basis weight, resin film basis weight, and thermoplastic resin application amount of the prepreg base material of Example 1. It was. In Comparative Example 8, the carbon fiber basis weight is 25 g / m ² , the resin film basis weight is 6 g / m ² , and the dispersion amount of the thermoplastic resin is 1 g / m ² , so that the base material thickness is approximately 0.025 mm. A prepreg substrate was obtained. In Comparative Example 9, the weight of the carbon fiber per unit area is 400 g / m ² , the basis weight of the resin film is 94 g / m ² , and the spraying amount of the thermoplastic resin is 15 g / m ² . A cut prepreg base material of 4 mm was obtained. In Comparative Examples 8 and 9, the ratio of the carbon fiber basis weight, the resin film basis weight, and the dispersion amount of the thermoplastic resin is the same as in Example 1.

  In Comparative Example 8, none of the fiber reinforced plastics obtained by press molding had swells of fibers, the fibers were sufficiently flowing to the end portions, and there was no warp. However, since the thickness of the base material is extremely thin, it is difficult to uniformly dispose the carbon fiber, and a cut prepreg base material with a clear opening is obtained. For this reason, the fiber-reinforced plastic obtained by press molding also has some spots, and the appearance quality is poor.

  Further, in Comparative Example 9, the fiber reinforced plastic obtained by press molding had no fiber undulation, the fiber sufficiently flowed to the end, no warp, and maintained good appearance quality and smoothness. It was. However, it was found that the tensile strength is 400 MPa, which is considerably lower than those of Example 1 and Examples 11 and 12.

(Comparative Examples 10 and 11) [Comparison of fiber content (Table 5)]
A fiber-reinforced plastic was obtained in the same manner as in Example 1 except that the fiber volume content Vf was changed by changing the carbon fiber weight per unit area of the cut prepreg base material of Example 1. Each Comparative Example 10 is a carbon fiber weight per unit area 237 g ^/ m 2, Vf is 70%, Comparative Example 11 is 135 g ^/ m 2, Vf was 40%.

  In Comparative Example 10, the fiber reinforced plastic obtained by press molding was swelled, and the fiber did not flow to the end at the surface portion that received friction with the mold. A resin rich portion was present on the surface portion, the appearance quality was poor, and warping occurred. The fiber reinforced plastic obtained in Comparative Example 11 had no warp and maintained good appearance quality and smoothness. However, the tensile elastic modulus was 36 GPa and the tensile strength was 440 MPa, which were considerably low values as compared with Example 1 and Examples 13 and 14.

(Comparative example 12) [Short fiber random orientation sheet]
A resin film coated with a thick epoxy resin composition similar to that in Example 1 was prepared. Next, a carbon fiber bundle (tensile elastic modulus 290 GPa, tensile strength 5900 MPa, 12,000 pieces) cut to a length of 25 mm is uniformly dropped on the resin film so that the weight per unit area becomes 125 g / m ² . Scattered. Further, after covering another cut carbon fiber, the cut carbon fiber was sandwiched, and then passed through a calender roll to prepare an SMC sheet having a fiber volume content Vf of 55%. This SMC sheet was cut out into 250 × 250 mm, and 16 layers were laminated to obtain a laminate, and then molded in the same manner as in Example 1 to obtain a fiber reinforced plastic.

  In the obtained fiber reinforced plastic, fibers sufficiently flowed to the end portion. On the other hand, warping occurred slightly, but sinking occurred in the resin-rich part due to the coarse and dense fiber distribution, and the smoothness was poor. The tensile elastic modulus was 36 GPa, which was considerably lower than the theoretical value because the fiber was not straight, the tensile strength was 250 MPa, and its CV value was 13%, which showed great variation.

It is an enlarged plan view which shows an example of the cutting pattern of the cutting prepreg base material of this invention. It is a top view which shows an example of the laminated body for a comparison, and fiber reinforced plastics. It is a top view which shows an example of the laminated body of this invention and a fiber reinforced plastic. It is a top view which shows an example of the cutting die for inserting a notch into a prepreg base material. It is sectional drawing which shows an example of the cutting prepreg base material of this invention. It is a perspective view which shows an example of the manufacturing method of the cutting prepreg base material of this invention. It is a perspective view which shows an example of the manufacturing method of the cutting prepreg base material of this invention. It is an enlarged plan view which shows an example of the cutting pattern of the cutting prepreg base material of this invention.

Explanation of symbols

1: Fiber longitudinal direction 2: Vertical direction of fiber 3: Carbon fiber 4: Discontinuous end (cut) of carbon fiber
5: Angle Θ between cut and fiber direction
6: Fiber length L divided by a notch paired in the fiber direction
7: Pre-preg base material 8: Width cut into each other by the cuts 9: Projected length Ws obtained by projecting the cuts in the vertical direction of the carbon fiber
10: Laminate 11: Fiber reinforced plastic 12: Short fiber layer 13: Area without carbon fiber (cut opening)
14: Adjacent layer 15: Fiber bundle end portion 16: Resin rich portion 17: Layer waviness 18: Cutting die 19: Blade 20: Row of blades 21: Reference direction of cutting die 22: Perpendicular to reference direction of cutting die Direction 23: Angle α
24: Spacing in the reference direction of the cutting die of the row of adjacent blades 25: Additional resin layer 26: Cut prepreg base material 27: Thermosetting resin 28: Thermoplastic resin 29: Base 30: Rotating roller

Claims (9)

In a prepreg base material composed of carbon fibers aligned in one direction and a matrix resin mainly composed of a thermosetting resin, a plurality of intermittent cuts in a direction crossing the carbon fibers on the entire surface of the prepreg base material Is inserted, the absolute value Θ of the angle between the cut and the carbon fiber is in the range of 2 to 25 °, and the projection length Ws obtained by projecting the cut in the vertical direction of the carbon fiber is 0. 1 to 1.5 mm, substantially all the carbon fibers are divided by the cut, and the fiber length L of the carbon fiber divided by the cut is in the range of 10 to 100 mm. The thickness H of the prepreg base material into which the notches are inserted is 30 to 300 μm, the fiber volume content Vf is in the range of 45 to 65%, and the prepreg base material into which the notches are inserted is ASTM D7137 / According to D7137M-05 In the laminated structure, using an autoclave, pressure 6 kg / cm ^2, and held for two hours after reaching the temperature was raised to 180 ° C. from 25 ° C. at a heating rate of 1.5 ° C. / min to cure the resin, ASTM D7137 / D7137M-05 has a CAI strength of 200 to 400 MPa and a dent depth of 0.18 to 2 mm as measured according to ASTM D7137 / D7137M-05. Furthermore, the cut prepreg base material in which the tensile strength measured according to JIS-7073 (1988) expresses 450-850 MPa. All the geometric shapes of the cuts are linear, the cut length W is in the range of 0.5 to 1.5 mm, and all the carbon fibers cut by the cut are substantially The cut prepreg base material according to claim 1, which has the same fiber length L. The cut prepreg base material according to claim 1, wherein the cut prepreg base material has a layered additional resin layer containing a thermoplastic resin on at least one surface of the cut prepreg base material. The means for inserting the cut into the cut prepreg base material is to press a die having a plurality of blades against the prepreg base material made of carbon fiber and matrix resin aligned in one direction. The cut prepreg base material according to any one of claims 1 to 3. The means for inserting a notch into the notched prepreg base material presses a rotating blade provided with a blade on a rotating roller against a prepreg base material made of carbon fiber and matrix resin aligned in one direction. The cut prepreg base material according to any one of claims 1 to 4. A laminate comprising at least part of the cut prepreg base material according to any one of claims 1 to 5, wherein a plurality of prepreg base materials in which carbon fibers are aligned in one direction are laminated, A prepreg laminate in which a prepreg base material in which carbon fibers are aligned in one direction is integrated with the fiber direction of the prepreg base material oriented in at least two directions. A fiber reinforced plastic obtained by laminating a plurality of the cut prepreg substrates according to claim 1 or 5 or molding the laminate according to claim 6 into a predetermined shape. The fiber reinforced plastic according to claim 7, wherein a part of the fiber reinforced plastic includes a standing surface or a rib shape. The fiber reinforced plastic according to claim 7 or 8, wherein the fiber reinforced plastic is used as an aircraft member.

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