JP6907503B2 - Manufacturing method of cross-ply laminate and fiber reinforced plastic - Google Patents

Description

The present invention relates to a cross-ply laminate composed of reinforcing fibers and a resin and in which prepregs having a plurality of cuts are laminated, and is suitable for hand lay-up.

Fiber reinforced plastics made of reinforced fibers and resins are attracting attention in industrial applications because they have high specific strength and specific elastic modulus, excellent mechanical properties, and high functional properties such as weather resistance and chemical resistance. It is being developed for structural applications such as aircraft, spacecraft, automobiles, railroads, ships, electrical appliances, and sports, and its demand is increasing year by year. Hand lay-up is one of the molding methods of fiber reinforced plastic, and it is shaped by manually pressing a fiber base material made by processing reinforced fibers into a sheet shape against a mold having a product shape or a structure requiring repair. Is a method of obtaining a fiber reinforced plastic by solidifying the resin impregnated in the fiber base material. Since it is a manual work, the fiber base material can be pressed against the mold while stretching the required part to shape it, and even a complicated shape can be molded with high quality.

Hand lay-up includes a method of pressing a fiber base material that is not impregnated with resin into a mold to shape it, and then impregnating it with a resin having a low viscosity to solidify it (for example, Patent Document 1). There is a method (for example, Patent Document 2) in which a shape is formed and solidified by a prepreg impregnated with. The former can be molded using an inexpensive fiber base material that has not undergone the prepregation process. The latter is an effective method for obtaining a good quality molded article.

Japanese Unexamined Patent Publication No. 2015-117442 Japanese Unexamined Patent Publication No. 8-25491

However, in the method described in Patent Document 1, when the reinforcing fibers broken during the hand lay-up work are scattered and the working environment is deteriorated, or when the reinforcing fibers are undulated in the process of impregnating the resin, the resin is not completely impregnated and voids are formed. May remain. Further, since the method described in Patent Document 2 uses a prepreg in which a fiber base material is impregnated with a resin in advance, there is a problem that the cost of the prepreg itself is high.

For hand lay-up using a prepreg, it is common to use a prepreg in which a fiber base material (woven fabric) having a woven structure having excellent shapeability as a reinforced form is impregnated with a resin. On the other hand, as for the mechanical properties of the solidified fiber reinforced plastic, it is superior that the reinforced form of the reinforced fiber has a woven structure, and that the reinforced fiber is oriented in one direction without undulation in the thickness direction, which is higher. For products with desired mechanical properties, it is preferable to use a prepreg in which reinforcing fibers are oriented in one direction (unidirectional prepreg). However, since the unidirectional prepreg has high rigidity in the fiber direction, it is difficult to stretch it, and when following a mold having a three-dimensional shape, it is difficult to follow the shape because the reinforcing fibers are stretched at the corners. Further, the unidirectional prepreg is not suitable for hand lay-up because it is connected only with resin in the non-fiber direction and breaks when a tensile load is applied in the non-fiber direction. In the case of a laminated body of unidirectional prepregs in which a plurality of sheets are laminated by changing the angle in the fiber direction, the splitting of the prepregs is reduced, but the tension of the reinforcing fibers at the corners cannot be eliminated, and the mold has a three-dimensional shape. Shape tracking is difficult.

Therefore, an object of the present invention is to provide a laminate of prepregs that is suitable for hand laying and exhibits excellent mechanical properties when made into a fiber reinforced plastic.

The present invention provides the following cross-ply laminated body laminate in order to solve such a problem. That is, it is composed of a plurality of prepregs having a volume content Vf of 45 to 65% of the reinforcing fibers oriented in one direction and the reinforcing fibers containing the resin, and is configured to include the prepregs in which the fiber directions intersect substantially at right angles. It is a cross-ply laminated body
Each prepreg is a cut prepreg having a plurality of cuts across the reinforcing fibers, and substantially all the reinforcing fibers have a fiber length (L) of 10 to 300 mm. A cross-ply laminate that satisfies or satisfies the tensile property 2 shown below in an environment of 60 ° C.
(Tensile property 1) When the fiber direction of any of the prepregs in the cross-ply laminate is set to 0 °, the cross-ply laminate is subjected to 1% tensile strain in the 0 ° direction with respect to the cross-ply laminate. Let the load generated in the 0 ° direction of the body be the load 1, and the load generated in the 0 ° direction of the cross-ply laminated body when a 2% tensile strain is applied to the cross-ply laminated body in the 0 ° direction is the load 2. Then, the load is 1 × 0.5 <load 2 <load 1 × 1.5.
(Tensile property 2) When the fiber direction of any of the prepregs in the cross-ply laminate is set to 0 °, the cross-ply laminate is subjected to 1% tensile strain in the 0 ° direction with respect to the cross-ply laminate. Let the load generated in the 0 ° direction of the body be the load 1, and the load generated in the 0 ° direction of the cross-ply laminated body when a 2% tensile strain is applied to the cross-ply laminated body in the 0 ° direction is the load 2. Then, the load is 1 × 0.5 <load 2 <load 1 × 1.5.
In the cross-ply laminated body of the present invention, when the number of cuts contained in 10 small circular regions having a diameter of 10 mm arbitrarily selected from the prepreg is used as the population, the average value of the population is used. Is preferably 10 or more and the coefficient of variation is preferably 20% or less.

According to the present invention, it is possible to obtain a cross-ply laminate that is suitable for hand lay-up and exhibits excellent mechanical properties when used as a fiber reinforced plastic.

Cross-ply laminate It is a conceptual diagram which shows an example of a small area extracted on a prepreg. It is a conceptual diagram which shows an example of the cut pattern of the prepreg of this invention. It is a conceptual diagram which shows an example of the cut pattern of the prepreg of this invention. It is a conceptual diagram which shows an example of the cut pattern of the prepreg of this invention. It is a cut pattern applied in Examples and Comparative Examples. This is the shape of the mold used in Example 1. It is a small area extraction pattern in a prepreg in an Example. It is a large shaped type.

The present inventors include unidirectionally oriented reinforcing fibers and a resin in order to obtain an intermediate base material which is suitable for hand lay-up and exhibits excellent mechanical properties when made into a fiber reinforced plastic. The prepreg having a volume content Vf of 45 to 65% was made into a cross-ply laminated body in which a plurality of prepregs were laminated so that the orientation directions (fiber directions) of the reinforcing fibers intersected substantially in the perpendicular direction, and the reinforcing fibers were used for the prepreg. This problem is solved by forming a cut prepreg in which substantially all the reinforcing fibers are divided into fiber lengths L = 10 to 300 mm by a plurality of crossing cuts, and further forming a cross-ply laminate having tensile properties described later. It is the one that investigated the solution.
Normally, the fiber direction of the reinforcing fiber is high and it is difficult to stretch it, but by dividing the reinforcing fiber by cutting, it is possible to stretch the prepreg in the fiber direction, and the cross-ply laminate in which the prepreg is laminated can be used. By doing so, it is possible to prevent the prepreg from cracking when a load is applied to the prepreg of each layer in the non-fiber direction. The configuration in which the prepregs laminated so that the fiber directions intersect at a substantially right angle is constrained to each other because the warp and weft are restrained to each other and can be stretched in the ± 45 ° direction in which the reinforcing fibers are not oriented. Since it has a structure that imitates a woven fabric having excellent shape and can be expected to have the same shapeability as a woven fabric, it is preferable to laminate it on a cross ply (laminate so that the fiber directions intersect substantially at right angles). Laminating is convenient because it is only necessary to rotate the prepreg cut into squares of the same size by 90 ° and stack them. The fact that the fiber direction is substantially right angle means that the fiber direction is within the range of 90 ° ± 10 °.

The number of cross-ply laminates laminated so that the fiber directions intersect substantially at right angles is not particularly limited, and for example, the laminated configurations are [0/0/90/90], [0/90], [0/90] ₂ or the like may be used, and the number of sheets of 0 ° and 90 ° such as [0/90/0] may be different. A cross-ply laminate in which prepregs of different cut insertion methods (cut patterns) are laminated may be used. The thicker the cross-ply laminate, the more difficult it is to stretch. Therefore, the thickness after lamination is preferably smaller than 1 mm.

In the present invention, substantially all the reinforcing fibers are divided into fiber lengths L = 10 to 300 mm. In each prepreg in the cross-ply laminate, the reinforcing fibers outside the range of L = 10 to 300 mm. It means that the total volume of the prepreg is 0% or more and 10% or less with respect to the volume of the prepreg.

By setting the volume content Vf of the reinforcing fibers of each prepreg to 65% or less, the reinforcing fibers at the cut portion are displaced, shape followability can be obtained, and it is sufficient to suppress resin chipping on the surface that occurs during molding. The amount of resin can be secured. From this point of view, Vf is preferably 65% or less. Further, the lower the Vf, the higher the stretching effect in the fiber direction, but when the Vf is smaller than 45%, it becomes difficult to obtain the high mechanical properties required for the structural material. From this point of view, Vf is preferably 45% or more.

By setting L of the reinforcing fibers divided by the cut to 300 mm or less, the existence probability of the cut can be increased in the fiber direction of the cross-ply laminate, and the shape followability to fine irregularities can be improved. When L is set to 10 mm or more, the distance between the cuts is increased, so that when a load is applied to the fiber reinforced plastic formed by using such a prepreg, cracks are hard to be connected and the strength is high. .. Considering the relationship between the shape followability at the time of molding and the mechanical properties of the molded fiber reinforced plastic, the preferable range of L is 10 to 300 mm. The more preferable range of L is 10 to 100 mm, more preferably 15 to 30 mm.

As shown in FIG. 3, the fiber length L refers to the length of the reinforcing fiber divided by an arbitrary cut and a cut (paired cut) closest to the reinforcing fiber direction. There is. Since the reinforcing fibers escape when the cut is inserted, a long cut may be intentionally inserted into the prepreg, and the reinforcing fibers having a fiber length shorter than the majority of L may be present in the prepreg. However, its volume ratio should be less than 5% of the volume of the prepreg. Further, in each prepreg, there may be a reinforcing fiber in which the cut is not inserted due to a slight deviation in the fiber direction at the time of inserting the cut, deterioration of the device for inserting the cut, or a reinforcing fiber having an L of more than 300 mm. However, its volume ratio should be less than 5% of the volume of the prepreg. By making the paired cuts, substantially all the reinforcing fibers are in a predetermined fiber length range (10 to 300 mm), which leads to followability to the three-dimensional shape and prevention of bridging.

In the present invention, when the fiber direction of any one of the prepregs in the cross-ply laminate is 0 ° at room temperature, that is, in an environment of 25 ° C., 1% in the 0 ° direction with respect to the cross-ply laminate. When a load generated in the 0 ° direction of the cross-ply laminate when a tensile strain is applied is a load 1, and a 2% tensile strain is applied to the cross-ply laminate in the 0 ° direction in an environment of 25 ° C. Assuming that the load generated in the 0 ° direction of the cross-ply laminated body is the load 2, it is preferable that the load 1 × 0.5 <load 2 <load 1 × 1.5 (tensile characteristic 1) is satisfied.

FIG. 1 is a conceptual diagram of a cross-ply laminated body in which two layers of prepreg are laminated, and the fiber direction of the upper prepreg is set to 0 ° direction 3. When the cross-ply laminate is pressed against the mold by hand lay-up to shape it, it is most easily stretched in the 45 ° direction 5, but it is difficult to shape it while stretching only the 45 ° direction 5. When shaping while stretching in a direction closer to 0 ° direction 3 than in 45 ° direction 5, the easier it is to stretch in 0 ° direction 3, the easier it is to stretch at that angle. Ease of ease is a measure of the ease of shaping the cross-ply laminate. When shaping while stretching in a direction closer to 90 ° than in 45 ° direction 5, the ease of stretching of another prepreg in the 0 ° direction 4 of the cross-ply laminate is the shaping of the cross-ply laminate. It is a measure of ease of use.

The cross-ply laminate of the present invention has the tensile characteristics (load 1 × 0.5 <load 2 <load 1 ×) when the fiber direction of any one of the prepregs in the cross-ply laminate is 0 °. It is important to satisfy 1.5). For example, when the fiber direction of the upper prepreg is set to the 0 ° direction 3, the fiber direction of the lower prepreg is set to the 0 ° direction as long as the tensile characteristics are satisfied. Even if the tensile property is not satisfied in the case where the above-mentioned tensile property is not satisfied (that is, when the 90 ° direction 4 of the fiber direction of the upper prepreg is set to the 0 ° direction), the embodiment is included in the cross-ply laminate of the present invention. Particularly preferably, in the cross-ply laminate of the present invention, when the fiber direction of any one of the prepregs of the cross-ply laminate is 0 °, the tensile properties (load 1 × 0. A mode that satisfies 5 <load 2 <load 1 × 1.5), that is, for all prepregs in the cross-ply laminate, the tensile characteristics (load 1 × 0) in the 0 ° direction when the fiber direction is 0 °. It is an embodiment that satisfies .5 <load 2 <load 1 × 1.5).

At the time of hand lay-up, it is preferable that the strain in the 0 ° direction of the prepreg stretches by 1% or more in the 0 ° direction, but if it continues to stretch due to elastic deformation, it contracts after shaping and the shape cannot be maintained, or the load required for shaping. The tensile property of the cross-ply laminated body in the 0 ° direction is non-linear, and it is preferable that the cross-ply laminated body has a property that the elastic modulus gradually decreases. That is, it is preferable that the load 2 <load 1 × 1.5. Further, if the strain of the cross-ply laminate in the 0 ° direction is 2% or less and the cross-ply laminate has a characteristic of being divided starting from a part of the cut, the cross-ply laminate is torn off during shaping. Therefore, as the tensile characteristics of the cross-ply laminated body in the 0 ° direction, it is preferable that the load in the 0 ° direction does not decrease extremely while the strain in the 0 ° direction is 1 to 2%. That is, it is preferable that the load 2> the load 1 × 0.5. A more preferable range of tensile properties is load 1 × 0.7 <load 2 <load 1 × 1.3. Further, even if a notch is inserted and substantially all the reinforcing fibers are cut, the cross-ply laminate having a load of 1 of 5 N or more per 1 mm of the width of the cross-ply laminate has the rigidity of the cross-ply laminate. Since it is high, it is easy to handle and is preferable. On the other hand, if the load 1 is too large, even if the load 1 × 0.5 <load 2 <load 1 × 1.5 is satisfied, it may not be easily stretched by human power and may not be suitable for hand lay-up. Therefore, the load 1 is preferably 100 N or less per 1 mm of the width of the cross-ply laminated body.

A tensile test piece obtained by cutting out a cross-ply laminated body into a strip may be used for measuring the load 1 and the load 2, and a tensile tester may be used for applying the tensile strain. The strain can be measured by the method using the non-contact strain measuring device described in the examples.

In the present invention, when the fiber direction of any of the prepregs of the cross-ply laminate is 0 ° and a tensile strain of 2% is applied to the cross-ply laminate in the 0 ° direction, the cross-ply laminate It is preferable that the total area of the cut openings (referred to as the area ratio of the cut openings) in the area is 0% or more and 1% or less from the viewpoint of the surface quality of the fiber reinforced plastic. The notch opening may be filled with the resin flowing, or the adjacent layer may be visible when the resin is not filled. In either case, the cut opening looks different in color from the portion containing the reinforcing fiber, so that the surface quality is often impaired when the fiber reinforced plastic is used.

In the present invention, the cut opening is a cut and a cut when a digital image taken from a distance of 10 cm or more and 50 cm or less from the surface is binarized by image processing on the surface of a cross-ply laminate or a fiber reinforced plastic. Refers to an opening that can separate parts other than the above.

When the area ratio of the cut opening in the cross-ply laminated body is 0% or more and 1% or less, the cut opening is difficult to be visually recognized, and the surface quality of the fiber-reinforced plastic after solidification is good. Even when a tensile strain of 2% is applied, if the area ratio of the cut opening is 0% or more and 1% or less, the cut is made when the opening of each cut is small or the fiber length is long. For example, when the probability of existence of is low. The inflow of reinforcing fiber bundles adjacent to the notch can result in an opening of 1% or less. A more preferable area ratio of the notch opening is 0.8% or less.

The cross-ply laminate in the present invention is 0 ° with respect to the cross-ply laminate when the fiber direction of any one of the prepregs in the cross-ply laminate is 0 ° at a temperature of 60 ° C. The load generated in the 0 ° direction of the cross-ply laminate when a tensile strain of 1% is applied in the direction is assumed to be load 1, and the tension of 2% in the 0 ° direction with respect to the cross-ply laminate in an environment of 60 ° C. Assuming that the load generated in the 0 ° direction of the cross-ply laminate when strain is applied is load 2, the cross-ply laminate satisfying load 1 × 0.5 <load 2 <load 1 × 1.5 (tensile characteristic 2). It may be a body. Even if it is difficult to shape at room temperature, when shaping while heating with a heating means such as a dryer, load 1 x 0.5 <load 2 <load 1 x 1.5 under a 60 ° C environment. By filling it, it is easy to shape it, and after shaping it is easy to fix the shape. Preferably, load 1 × 0.7 <load 2 <load 1 × 1.3.

Further, even at a temperature of 60 ° C., when the fiber direction of any prepreg of the cross-ply laminate is set to 0 °, a tensile strain of 2% is applied to the cross-ply laminate in the 0 ° direction. At that time, the total area of the cut openings (referred to as the area ratio of the cut openings) to the area of the cross-ply laminated body is 0% or more and 1% or less from the viewpoint of the surface quality of the fiber reinforced plastic. Is preferable. A more preferable area ratio of the notch opening is 0.8% or less.

The area ratio of the cut opening in the cross-ply laminated body when a tensile load is applied can be measured by image processing after photographing the cross-ply laminated body during the tensile test by the method described in the examples. can. When the load drops sharply in the process of applying 2% tensile strain in the 0 ° direction of the cross-ply laminate and the load 2 <load 1 × 0.5, the reinforcing fibers swell and the surface Dignity is impaired.

As a preferred embodiment of the prepreg in the cross-ply laminate of the present invention, it is preferable that a plurality of cuts in the prepreg are arranged at high density and uniformly. Specifically, when the number of cuts contained in 10 circular small regions having a diameter of 10 mm arbitrarily selected in the prepreg is used as the population, the average value of the population is 10 or more and the coefficient of variation is Is a cut prepreg within 20% (hereinafter, a state where the average value of the population is 10 or more is called high density, and a state where the coefficient of variation is within 20% is called homogeneous). The presence of high-density and homogeneous cuts allows the cross-ply laminate to be uniformly stretched at any location during manual shaping, improving handleability.

FIG. 2 shows a state in which 10 small regions 8 having a diameter of 10 mm are extracted from the prepreg 1. It is preferable to extract the small regions so densely that the small regions do not overlap, but if the prepreg is not large enough to include all 10 small regions without overlapping, even if the small regions overlap each other. good.

The number of cuts included in the small area is the total number of cuts existing in the small area and some cuts that partially contact the contour of the small area. The average value and the coefficient of variation are calculated by Equations 1 and 2, respectively, assuming that the number of cuts in the 10 small regions is ni (i = 1 to 10).

The higher the number of cuts, the better the followability to the three-dimensional shape, and the smaller the opening of each cut when the prepreg is deformed. When this is done, good surface quality can be obtained. In addition, even if the number of reinforcing fibers divided by the cut is the same as a whole, when a load is applied when the fiber reinforced plastic is used, the stress concentration around the cut becomes large when the cut is large. However, the finer it is, the less stress concentration is reduced and the better the mechanical properties. Therefore, when the number of cuts contained in the small region is counted in 10 small regions and used as the population, the average value of the population is preferably 10 or more. More preferably, the number is 15 or more. The same reinforcing fiber may be divided by a plurality of cuts in the small region, but if the fiber length L of the reinforcing fiber is smaller than 10 mm, the mechanical properties after solidification may deteriorate, so that the small region It is more preferable that the same reinforcing fiber is not divided by a plurality of cuts. When the average value of the population is larger than 50, the same reinforcing fiber is more likely to be divided by a plurality of cuts in the small region, so that the average value of the population is preferably 50 or less. On the other hand, the more uniformly the cuts are distributed, the more the cross-ply laminate can be uniformly stretched to follow the shape during hand lay-up, and the variation in the opening of each cut becomes smaller when the prepreg is deformed. Therefore, it exhibits stable mechanical properties when it is made of fiber reinforced plastic. Therefore, the coefficient of variation of the population is preferably 20% or less. More preferably, it is 15% or less. Here, as a method for extracting small regions, as shown in FIG. 2, it is preferable to extract small regions so that they are relatively close to each other. The coefficient of variation may fluctuate depending on the extraction pattern. In that case, the measurement is performed by changing the extraction pattern five times, and if the coefficient of variation is 20% or less four times or more, it is considered that the aspect of the present invention is satisfied.

The concept of inserting a relatively small notch has already been described in the International Publication WO2008 / 099670 pamphlet. For example, the incision pattern shown in FIG. 2 of the internationally published pamphlet is enlarged or reduced to scale the average of the population. When the value is 10 or more, the fiber length of the reinforcing fiber must be 10 mm or less, and when the fiber length of the reinforcing fiber is 10 mm, the average value of the population is 5 or less. Then, the density of the incision distribution becomes smaller.

Further, in many existing cutting patterns represented by FIG. 1 (A) of the pamphlet of International Publication WO2008 / 099670, FIG. 3 (a) (when the document is not specified, it is the figure of the present specification. As shown in (same as above), the adjacent cuts are shifted by half the length L / 2 of L with respect to the length L of the reinforcing fibers to form intermittent cuts. In the case of such a cut pattern, the shorter the cut length and the longer the fiber length, the more likely it is that the cuts are linearly present at intervals of L / 2 in the orientation direction of the reinforcing fibers. Population variability increases. In such a case, the cut openings are concentrated on the straight line, and the openings are prominently displayed. As shown in FIG. 3B, by shifting the adjacent cuts in fine cycles such as L / 5 and L / 6 instead of L / 2, a cut pattern in which the cuts are evenly distributed during the prepreg can be obtained. It becomes a cut prepreg to have, and when the cut prepreg is stretched, the stretched part is not biased, uniform deformation is possible, and the opening of each cut is suppressed (hereinafter, the cut is evenly distributed). The distributed cut pattern is sometimes referred to as a homogeneous cut pattern). Further, instead of shifting the adjacent cuts in a staircase pattern as shown in FIG. 3 (b), the adjacent cuts may be shifted as shown in FIG. 3 (c). In FIG. 3 (c), the cuts are deviated in the cycle of L / 10, but the reinforcing fiber bundles are divided by the cuts, and the ends of the adjacent reinforcing fiber bundles (for example, the cuts in FIG. 3 (c)) are cut. The distance between the indentation s1 and the incision s2) is 2L / 5, which is longer than the L / 5 in FIG. 3 (b). The long distance between the ends of adjacent reinforcing fiber bundles has the effect of suppressing crack growth and chaining of cut openings, improving both mechanical properties and surface quality. In the case of FIG. 3A, the distance between the ends of adjacent reinforcing fiber bundles is as long as L / 2, but the distance between the two cuts sandwiching the reinforcing fiber bundle is also short, so the two cut openings The stress concentration parts due to the above are likely to overlap, which is not preferable as a mechanical property.

The plurality of cuts in the prepreg may form a plurality of intermittent straight lines as shown in column 9 of FIG. 3, and the plurality of intermittent straight lines may be inserted in parallel. Here, the fact that a plurality of cuts form an intermittent straight line means that the plurality of cuts are connected to form a straight line, and these cuts exist in the same straight line. In the present invention, when a plurality of cuts exist in the same straight line, the angle between the straight line extending the cut and the straight line connecting the closest points of the target cuts is within 1 °. Refers to something. When there are multiple cuts in the same straight line, insert the cut by rolling the rotating round blade of the perforation in a straight line, or scan the pulse laser for laser processing in a straight line at high speed. A highly productive incision insertion method can be applied, such as inserting an incision corresponding to the pulse period.

Further, as a preferred embodiment of the prepreg in the cross-ply laminate of the present invention, the plurality of cuts in the prepreg form a plurality of intermittent straight lines, and the plurality of cuts forming the intermittent straight lines are substantially. For a plurality of cuts having the same length Y and forming the intermittent straight line, the distance between the cuts adjacent to each other (hereinafter referred to as the distance between the cuts on the same straight line) is larger than 3 times Y. Things can be mentioned. As described above, when the adjacent reinforcing fibers separated by the cut are displaced by L / 2, the distance between the cuts on the same straight line is also Y with respect to the cut length Y. However, by shifting at a cycle of L / 3 or less, the distance between cuts on the same straight line becomes three times or more of Y. When the cuts are present on the same straight line, damage due to the cuts may occur on the extension line of the cuts, so that the closer the distance is, the easier it is for the cracks to be connected. Therefore, by keeping the same linear cuts as far apart as possible, crack connection is suppressed and the strength of the fiber reinforced plastic is improved. Also, if the distance between the cuts on the same straight line is short, the cut openings will be chained during hand lay-up, making it easier for the cuts to be recognized as an intermittent straight line pattern, while the cuts will be separated from each other. By being present, it will not be recognized as a pattern, and the surface quality will be excellent. In the present invention, the plurality of cuts in the prepreg form a plurality of intermittent straight lines, and the plurality of cuts forming the intermittent straight lines have substantially the same length Y, and the intermittent straight lines are formed. For a plurality of cuts forming a straight line, it is preferable to have at least one prepreg having a distance between adjacent cuts greater than three times Y, and particularly preferably, for all the prepregs, the plurality of cuts form an intermittent straight line. The plurality of cuts forming the plurality of cuts forming the intermittent straight line have substantially the same length Y, and the distance between the cuts close to each other for the plurality of cuts forming the intermittent straight line is Y. It is also an embodiment larger than 3 times.

In the cross-ply laminate of the present invention, the projected length Ws when the notch in the prepreg is projected in the direction perpendicular to the reinforcing fibers in the prepreg is preferably in the range of 30 μm to 1.5 mm. By reducing Ws, the amount of reinforcing fibers divided by each notch is reduced, and strength is expected to be improved. In particular, by setting Ws to 1.5 mm or less, a large improvement in strength is expected. On the other hand, when Ws is smaller than 30 μm, it is difficult to control the cutting position, it is difficult to reduce all the reinforcing fibers to a predetermined length or less by the paired cutting, and the shape followability is deteriorated at the time of shaping. There is. Here, "projected length Ws in which the cut is projected in the direction perpendicular to the reinforcing fiber" means that the cut is in the plane of the prepreg in the direction perpendicular to the reinforcing fiber (to the reinforcing fiber), as shown in FIGS. On the other hand, with the projection plane 7) as the projection plane, it refers to the length when projected from the notch at a right angle to the projection plane (fiber orientation direction 6). In the present invention, it is preferable to have at least one prepreg having a projected length Ws of 30 μm to 1.5 mm when projected in the direction perpendicular to the reinforcing fibers in the prepreg, and particularly preferably the projected lengths of all the prepregs. Ws is 30 μm to 1.5 mm.

In the cross-ply laminate of the present invention, when the angle formed by the notch in the prepreg and the reinforcing fiber is θ, the absolute value of θ is preferably in the range of 2 to 25 °. Since the cutting angle is slanted, Ws can be made smaller than the size of the cutting length Y, so that a very small cut with a Ws of 1.5 mm or less can be industrially stable. It can be provided, and the prepreg is less likely to come apart due to continuous cutting during stacking, and is excellent in handleability as a prepreg. In particular, when the absolute value of θ is 25 ° or less, the mechanical properties, especially the tensile strength, are remarkably improved, and from this viewpoint, the absolute value of θ is more preferably 15 ° or less. On the other hand, if the absolute value of θ is smaller than 2 °, it becomes difficult to make a stable cut. That is, when the notch falls on the reinforcing fiber, the reinforcing fiber easily escapes from the blade when making the cut, and it becomes difficult to insert the reinforcing fiber while ensuring the position accuracy of the cut. From this point of view, it is more preferable that the absolute value of θ is 5 ° or more. In the present invention, it is preferable to have at least one prepreg having an absolute value of θ of 2 to 25 ° when the angle formed by the notch in the prepreg and the reinforcing fiber is θ, and particularly preferably all of them. This is an embodiment in which the absolute value of θ of the prepreg is 2 to 25 °.

As another preferable cut pattern of the prepreg in the cross-ply laminate of the present invention, as shown in FIG. 4, a plurality of cuts in the prepreg form an intermittent straight line, and the cut and the reinforcing fiber are connected to each other. When the angle to be formed is θ, the absolute value of θ is substantially the same, and the number of cuts where θ is a positive angle (positive cut) and the number of cuts where θ is a negative angle (negative cut). The number of is about the same. Here, the fact that the absolute value of θ is substantially the same means that the absolute value of the angle θ in all the cuts is within ± 1 ° of the average value obtained from the absolute value of the angle θ in all the cuts. say. Further, the fact that the number of positive cuts and the number of negative cuts are substantially the same means that the number of cuts in which θ is positive and the number of cuts in which θ is negative are approximately the same. The number of cuts in which θ is positive and the number of cuts in which θ is negative are approximately the same as the number of positive cuts and the number of negative cuts when expressed as a percentage based on the number. It means that it is 45% or more and 55% or less (the same applies hereinafter). When laminating the obtained prepregs, if the diagonal cuts are only at an angle in one direction, the cut directions of the two prepregs may be close to each other when the cross-ply laminated body is manufactured. When the cut directions of the two prepregs are close to each other, the cuts may overlap each other or the stretchability of the cross-ply laminated body may be anisotropic. Therefore, it is preferable that the cut pattern has substantially the same absolute value of the slope of the cut from the fiber direction and substantially the same number of positive cuts and negative cuts. In the present invention, when a plurality of cuts in the prepreg form an intermittent straight line and the angle formed by the cut and the reinforcing fiber is θ, the absolute value of θ is substantially the same. It is preferable to have at least one prepreg in which the number of cuts in which θ is a positive angle and the number of cuts in which θ is a negative angle are approximately the same, and particularly preferably, a plurality of cuts are provided for all prepregs. When an intermittent straight line is formed and the angle formed by the cut and the reinforcing fiber is θ, the absolute value of θ is substantially the same, and the number of cuts in which θ is a positive angle and θ are negative. This is a mode in which the number of cuts at the corners of is approximately the same.

As a preferred embodiment of the prepreg in the cross-ply laminate of the present invention, as shown in FIG. 4, when focusing on any one notch A inserted in the prepreg, among the cuts adjacent to the notch, among the cuts adjacent to the notch. There are four or more cuts C having different positives and negatives of θ, which are closer to each other than the cuts B having the same positive and negative values of θ. When following a three-dimensional shape, the movement of the reinforced fiber end of the prepreg cut insertion part is determined by the relationship between the cut angle and the fiber direction. From a macro perspective, the in-plane isotropic property after molding is guaranteed. When focusing on the cut A, the number of cuts C that are close to the cut and have different positive and negative values of θ that are closer in the shortest distance than the cut B that has the same positive and negative values of θ is Four or more are preferable, and four or more are particularly preferable. Further, a plurality of cuts form an intermittent straight line, and the plurality of cuts forming the intermittent straight line have substantially the same length Y, and a plurality of cuts forming the intermittent straight line. When focusing on any one notch A inserted in the prepreg, the distance between the cuts in close proximity (hereinafter referred to as the distance between the cuts on the same straight line) is more than three times Y. If there are four or more notches C that are close to the notch and have different positive and negative values of θ that are closer in the shortest distance than the notch B that has the same positive and negative values of θ, the positive and negative cuts are the positive and negative cuts. Is more uniformly arranged, which is preferable from the viewpoint of three-dimensional shape followability, surface quality, and mechanical properties. In the present invention, among the cuts that are close to any cut A inserted in the prepreg, the cut C that is closer in the shortest distance than the cut B in which the positive and negative of θ is the same and has a different positive and negative of θ is 4 It is preferable to have at least one prepreg existing at least one, and particularly preferably, among the cuts adjacent to any cut A inserted for all prepregs, the shortest cut B having the same positive and negative θ. In this embodiment, there are four or more notches C having different positive and negative values of θ that are close to each other.

Further, as a preferred embodiment of the prepreg in the cross-ply laminate of the present invention, as shown in FIG. 5, a plurality of cuts in the prepreg are inserted in a straight line and substantially the same length Y, and the cuts are close to each other. The shortest distance between them is longer than the depth of cut Y. Here, substantially the same length means that all the cut lengths are within ± 5% of the average value of all the cut lengths (the same applies hereinafter). From the viewpoint of mechanical properties, the fiber reinforced plastic breaks when the notches, which are the discontinuities of the reinforcing fibers, are connected by cracks. By using a cut pattern in which the cuts in the plane are separated from each other, there is an effect of suppressing crack connection at least in the same plane, and the strength is improved. The shortest distance between adjacent cuts is more preferably 1.2 times or more of Y. On the other hand, there is no particular upper limit to the distance between the cuts that are in close contact with each other, but when giving a high-density cut to the prepreg, the distance between the cuts that are in close contact with each other should be 10 times or more the cut length Y. It's not easy.

In the incision prepreg in which the incisions are distributed in high density, the followability to the three-dimensional shape is improved, and the mechanical characteristics can be expected to be improved by making each incision small, but the distance between the incisions is short. The mechanical properties are further improved when the notches are separated from each other than in the case. Therefore, when the cuts are inserted densely, it is necessary to make the cut pattern in which the cuts are separated from each other, that is, the shortest distance between the adjacent cuts to be larger than the cut length Y to improve the mechanical characteristics. This is especially important. Not only when the cuts are distributed in high density, the smaller the absolute value of θ, the better the mechanical characteristics can be expected. There is also a concern. However, the lengths Y are substantially the same, and the shortest distance between adjacent cuts is longer than Y, so that the cuts are further perpendicular to the orientation direction of the reinforcing fibers. Improvement of mechanical properties can be expected. When the depth of cut is high, it is expected that the mechanical properties will be improved and the surface quality will be improved by suppressing the cut opening. As represented by the internationally published WO2008 / 099670 pamphlet, it is a known technique to insert a notch diagonally into a reinforcing fiber, but FIGS. 2 (f) and 12 of the internationally published pamphlet. In a cut pattern in which adjacent cuts are deviated by L / 2 with respect to the fiber length L of the reinforcing fiber as shown in FIG. 3A, when L is long and the cut length is small, FIG. 3A. Similar to the phenomenon shown in, a uniform cut pattern cannot be realized, and when the cut prepreg is stretched, the dense cuts tend to stretch, and even when using fiber reinforced plastic, the cuts are close to each other. Therefore, the cuts are easily connected to each other, which may lead to deterioration of mechanical properties. By applying the diagonal cut to the homogeneous cut arrangement as shown in FIGS. 3 (b) and 3 (c), the effect of improving the mechanical characteristics by inserting the cut diagonally is more effectively exhibited. can. In the present invention, at least one prepreg in which a plurality of cuts in the prepreg are inserted in a straight line and substantially the same length Y, and the shortest distance between adjacent cuts is longer than the cut length Y. It is preferable to have one, and particularly preferably, a plurality of cuts are inserted in a straight line and substantially the same length Y for all prepregs, and the shortest distance between adjacent cuts is longer than the cut length Y. It is an aspect.

The resin to be impregnated with the reinforcing fibers oriented in one direction in the present invention is not particularly limited, and may be a thermoplastic resin or a thermosetting resin. Examples of the thermoplastic resin include polyamide (PA), polyacetal, polyacrylate, polysulphon, ABS, polyester, acrylic, polybutylene terephthalate (PBT), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene, polypropylene, and the like. Examples thereof include polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherimide (PEI), polyetherketoneketone (PEKK), liquid crystal polymer, vinyl chloride, fluororesin such as polytetrafluoroethylene, and silicone. Examples of the thermosetting resin include unsaturated polyester resin, vinyl ester resin, epoxy resin, benzoxazine resin, phenol resin, urea resin, melamine resin and polyimide resin. Deformations of these resins and two or more blended resins can also be used. Further, these thermosetting resins may be resins that are self-curing by heat, or may contain a curing agent, a curing accelerator, or the like. A thermosetting resin is preferable. Since the prepreg whose resin is a thermosetting resin has tackiness at room temperature, the upper and lower prepregs are easily integrated by adhesion when the prepregs are laminated. After laminating the prepreg, the adhesive may be strengthened by a pressurizing means such as evacuation. In addition, the thermosetting resin is soft when uncured and is suitable for manually shaping the prepreg.

When the resin is a thermoplastic resin, the prepreg is not tacky and cannot be laminated and integrated at room temperature. Therefore, the prepreg is integrated by a method equipped with heating and pressurizing means such as press molding to form a cloth. It is preferable to prepare a ply laminate.

The reinforcing fiber used in the present invention is not particularly limited, and may be glass fiber, Kevlar fiber, carbon fiber, graphite fiber, boron fiber or the like. Of these, carbon fibers are preferable from the viewpoint of specific strength and specific elastic modulus.

As a preferred embodiment of the cross-ply laminate in the present invention, the area is preferably 0.5 m ² or more. More preferably, it is 0.8 m ² or more. On the other hand, the maximum area of a realistic cross-ply laminated body is 5 m ² . Generally, the larger the area of the unlaminated prepreg, the more easily it bends, and the more wrinkles are likely to occur when it is placed in the mold during molding. By using a cross-ply laminated body, the rigidity is improved, and even if the area is 0.5 m ² or more, wrinkles are less likely to occur when arranging in a mold. Further, when producing a cross-ply laminate having a large area, a plurality of cut prepregs may be connected to form one layer. By using the cross-ply laminate, even if there is a joint, it is supported by the other layer, and the joint is not separated and the handleability is improved. It is preferable that the joint is a straight line parallel to the reinforcing fibers in order to maintain the mechanical properties of the fiber-reinforced plastic solidified from the cross-ply laminate.

The cross-ply laminate of the present invention may be set in a mold as it is in a flat plate shape and press-molded, or the cross-ply laminate may be pressed against a mold to form a preform, and then the preform is solidified. It may be manufactured as a fiber reinforced plastic. Since the cross-ply laminate of the present invention can be extended in the orientation direction of the reinforcing fibers, the preform completely follows the mold when performing high-pressure molding such as press molding by a double-sided mold. It does not have to be. It takes a long time to carefully follow the unevenness of the cross-ply laminate, but even if it does not completely follow the surface of the mold, it can follow the shape according to the pressure, and the preform preparation time. Will also be shorter. Not completely following the surface of the mold indicates that the area of the preform in contact with the mold is 90% or less of the surface area of the mold. The preform may be manufactured by being pressed against the mold by hand (hand lay-up), or may be pressed against the mold by using a robot or the like. When the cross-ply laminate is made to follow fine irregularities, in the manual shaping, it is possible to limit the places to be stretched while checking the places where wrinkles occur, and to follow them with high accuracy. A plurality of cross-ply laminates may be laminated at different angles. When solidifying the preform, the preform is placed between the mold and the bag film to form a closed space, and the closed space is evacuated and heated while pressurizing the prepreg laminate with the pressure difference from the atmospheric pressure. Then, it may be further molded by a compression heating gas by an autoclave, or it may be solidified only by pressurization by a pressure difference from the atmospheric pressure using a vacuum pump by an oven or contact heating. Alternatively, the preform may be sandwiched between molds and solidified by press molding.

When pressing the cross-ply laminate against the mold, it is also preferable to include a step of heating the cross-ply laminate. That is, when pressing the cross-ply laminate against the mold, a step of softening the cross-ply laminate by a heating means such as a dryer or a heater may be included. The mold itself may be heated. By heating the cross-ply laminate, the prepreg may be softened and the shape followability may be improved. The heating temperature is preferably such that the shape of the cross-ply laminate does not collapse, and the temperature at which the resin viscosity is maintained at 50 Pa · s or more is preferable.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the inventions described in the Examples.

In this embodiment, fabrication of a cross-ply laminate, measurement of tensile properties of the cross-ply laminate, measurement of the area ratio of the notch opening, evaluation of shape followability during hand lay-up, measurement of surface quality of fiber reinforced plastic, mechanics. The characteristic measurement was carried out according to the following method.

<Manufacturing of cross-ply laminate>
Insert a notch into the "Treca" (registered trademark) prepreg sheet P3052S-15 (reinforcing fiber: T700S, thermosetting resin: 2500, volume content of reinforcing fiber: 56%, laminated single-sided paper pattern), and 300 mm x It was cut out to 300 mm, and the non-laminated surfaces of the release paper were laminated so that the fiber directions were perpendicular to each other. The incision was made over the entire prepreg by a roller cutter with a blade placed in the cylinder. The bonded cross-ply laminate was evacuated for 30 minutes to improve the adhesion between the two prepregs to obtain a cross-ply laminate.

<Measurement of tensile characteristics of cross-ply laminate and measurement of area ratio of notch opening>
A 50 mm × 250 mm prepreg tensile test piece was cut out from the cross-ply laminate so that the fiber direction of one prepreg of the cross-ply laminate was the longitudinal direction (this fiber direction is 0 °). Both ends of the prepreg tensile test piece were grasped by 50 mm in an environment of 25 ° C., and a tensile load was applied to the prepreg tensile test piece using a tensile tester with a span interval of 150 mm. The tensile strain was measured by tracking the distance between two points marked at the center of the 0 ° side surface of the prepreg tensile test piece at a distance of 50 mm using a non-contact strain meter facing the 0 ° side of the prepreg tensile test piece. .. The load when the tensile strain in the 0 ° direction was 1% was recorded as the load 1, and the load when the tensile strain was 2% was recorded as the load 2.

During tensile strain application, the 0 ° side of the prepreg tensile test piece and the digital camera are separated by 30 cm so as not to overlap with the non-contact strain meter, and the sides other than the facing side with the digital camera are covered with a curtain that blocks light, and the digital camera is digitally used. An illumination was installed to illuminate the prepreg tensile test piece from the side facing the camera, and a digital image of the prepreg tensile test piece was acquired when the tensile strain in the 0 ° direction was 2%. From the digital image, a digital image corresponding to the area of 25 mm × 25 mm in the center of the test piece is cut out at 500 × 500 pixels, and the pixel corresponding to the cut is binarized so that the pixel corresponding to the cut is 1 and the part other than the cut is 0. The area ratio of the cut opening was obtained from the ratio of the number of pixels corresponding to the cut to the total number of pixels of the cut out digital image.

<Evaluation of shape followability during hand lay-up>
The cross-ply laminate was placed along the mold shown in FIG. 7 in an environment of 25 ° C. Align each side of the bottom surface of the mold with the fiber direction of the cross-ply laminate, press the cross-ply laminate against one corner, and stretch the cross-ply laminate in the 45 ° direction while stretching the wrinkles that occur on the sides. It was shaped along the corner. The remaining three corners were similarly aligned to form a preform in which the cross-ply laminate was shaped into a box shape that fits the mold. In Table 1, the labor required for shaping is divided into the following three stages.
A: The cross-ply laminate was easy to stretch in any direction and could be shaped into a box without wrinkles.
B: Although the cross-ply laminate had some parts that were difficult to spread, it could be shaped into a box shape without wrinkles.
C: The cross-ply laminate was difficult to stretch, and wrinkles remained when it was shaped into a box shape.

<Surface grade of molded fiber reinforced plastic (molded product)>
In order to confirm the quality of the surface other than the transfer surface whose surface quality is affected by the smoothness of the mold, the preform produced by pressing the cross-ply laminate against the mold shown in FIG. 7 is kept pressed against the mold. , The temperature was raised to 130 ° C. at 0.1 ° C./min and solidified to produce a fiber reinforced plastic. In Table 1, the surface grades of the obtained fiber reinforced plastics were divided into the following five stages.
A: The existence of the cut is hardly recognized and no wrinkles occur. B: The opening of the cut is small but the existence of the cut is recognized and no wrinkles occur. C: The cut is opened. Wrinkled but not wrinkled D: Wrinkled <Mechanical properties of fiber reinforced plastic>
As for the mechanical properties of fiberglass reinforced plastics, it was difficult to cut out a test piece capable of stably obtaining mechanical properties from the test piece after hand lay-up. Therefore, using a 350 mm × 350 mm mold, a 300 mm × 300 mm cross-ply laminate was stretched by applying a surface pressure of 3 MPa with a press machine to obtain a press-molded product of a 350 mm × 350 mm fiber reinforced plastic. The temperature at the time of press molding was 130 ° C., and after 90 minutes while maintaining the temperature and surface pressure, pressurization / heating was stopped, left at room temperature to cool, and then demolded.

The mechanical properties were measured using a tensile test piece cut out from the obtained fiber reinforced plastic in a size of 25 mm × 250 mm so that the fiber direction was the longitudinal direction, and tensile elastic modulus and tensile strength were obtained as the mechanical properties of the molded product. However, as for the laminated structure, four cross-ply laminated bodies are laminated at different angles, and the prepregs are laminated so that the laminated structure is [+ 45 / -45/0/90] s, and the tensile test piece is oriented in the 0 ° direction. In the longitudinal direction of. The test shall be based on ASTM D3039 (2008). The number of test pieces measured was 5 for each level, and the average value of tensile elastic modulus and tensile strength was used as a representative value.

(Example 1)
The cut pattern of the cut prepreg is shown in FIG. 6 (a), the length L of the divided reinforcing fibers is 24 mm, and the projected length Ws obtained by projecting the cut on a plane perpendicular to the orientation direction of the reinforcing fibers is 1 mm. The angle θ between the reinforcing fiber and the notch was 25 °. The reinforcing fiber bundles divided by the notch were arranged with a deviation of 1/4 of the reinforcing fiber length L with respect to the adjacent reinforcing fiber bundles.

As the tensile characteristics of the cross-ply laminate, the load 1 × 0.5 <load 2 <load 1 × 1.5 was satisfied. When the tensile strain was 2%, the notch was large and opened. The shape followability by hand lay-up was good, and the shape could be formed without wrinkles. As for the surface quality of the molded fiber reinforced plastic, a notch opening was observed on the surface.

(Example 2)
The cut pattern of the cut prepreg was set to the cut pattern shown in FIG. 6 (b), and a cross-ply laminated body was produced. The arbitrary cut and the other cut closest to the cut did not separate the same reinforcing fiber. The cuts had substantially the same length Y = 1 mm, and the shortest distance between adjacent cuts was 1.5 mm, which was 1.5 times that of Y. The length of the divided reinforcing fibers was 20 mm, and the projected length Ws of the cut projected onto a plane perpendicular to the orientation direction of the reinforcing fibers was 0.34 mm. The angle between the orientation direction of the reinforcing fibers and the notch was 20 °. The reinforcing fiber bundles divided by the notch were arranged with a deviation of 2/5 of the reinforcing fiber length L with respect to the adjacent reinforcing fiber bundles. The plurality of cuts formed an intermittent straight line, and for the plurality of cuts forming the intermittent straight line, the distance between the adjacent cuts was 22 times Y. As shown in FIG. 8, small regions arranged in six directions were extracted and the distribution of cuts was measured. As a result, the average value of the population was 12.4 and the coefficient of variation was 10.9%.

As the tensile characteristics of the cross-ply laminate, the load 1 × 0.5 <load 2 <load 1 × 1.5 was satisfied. An opening of a notch was observed when the tensile strain was 2%, but the opening area was smaller than that of Example 1. The shape followability due to hand lay-up was slightly difficult to stretch, but it was able to be shaped without wrinkles. As for the surface quality of the molded fiber reinforced plastic, a notch opening was observed on the surface.

(Example 3)
The cut pattern of the cut prepreg was set to the cut pattern shown in FIG. 6 (c), and a cross-ply laminated body was produced. The cuts had substantially the same length Y = 1 mm, and the shortest distance between adjacent cuts was 1.4 mm, which was 1.4 times that of Y. The length of the divided reinforcing fibers was 12 mm, and the projected length Ws of the cut projected onto a plane perpendicular to the orientation direction of the reinforcing fibers was 0.64 mm. The absolute value of the angle θ formed by the orientation direction of the reinforcing fibers and the cut was 40 °, and included approximately the same number of positive cuts in which θ was positive and negative cuts in which θ was negative. For both positive and negative cuts, multiple cuts form an intermittent straight line, and for multiple cuts that form an intermittent straight line, the distance between adjacent cuts is 7 times that of Y for positive cuts and negative. The notch was 13 times that of Y. As shown in FIG. 8, small regions arranged in six directions were extracted and the distribution of cuts was measured. As a result, the average value of the population was 10.9 and the coefficient of variation was 10.4%.

As the tensile characteristics of the cross-ply laminate, the load 1 × 0.5 <load 2 <load 1 × 1.5 was satisfied. When the tensile strain was 2%, the notch was slightly open. The shape followability by hand lay-up was good, and the shape could be formed without wrinkles. As for the surface quality of the molded fiber reinforced plastic, some cut openings were visible on the surface.

(Example 4)
The cut pattern of the cut prepreg was set to the cut pattern shown in FIG. 6 (d), and a cross-ply laminated body was produced. The arbitrary cut and the other cut closest to the cut did not separate the same reinforcing fiber. The cuts had substantially the same length Y = 1 mm, and the distance between the cuts closest to each other was 1.5 mm, which was 1.5 times that of Y. The length of the divided reinforcing fibers was 20 mm, and the projected length Ws of the cut projected onto a plane perpendicular to the orientation direction of the reinforcing fibers was 0.34 mm. The absolute value of the angle θ formed by the orientation direction of the reinforcing fibers and the cut was 20 °, and included approximately the same number of positive cuts in which θ was positive and negative cuts in which θ was negative. For both positive and negative cuts, multiple cuts form an intermittent straight line, and for multiple cuts that form an intermittent straight line, the distance between adjacent cuts is 3.4 times that of Y for a normal cut. In the negative cut, it was 24.3 times that of Y. Further, among the cuts close to any cut A inserted in the prepreg, there are four cuts C having different positive and negative values of θ, which are closer in the shortest distance than the cut B having the same positive and negative values of θ. rice field. As shown in FIG. 8, small regions arranged in six directions were extracted and the distribution of cuts was measured. As a result, the average value of the population was 11.3 and the coefficient of variation was 7.9%.

As the tensile characteristics of the cross-ply laminate, the load 1 × 0.5 <load 2 <load 1 × 1.5 was satisfied. When the tensile strain was 2%, the opening of the notch was hardly visible. The shape followability by hand lay-up was good, and the shape could be formed without wrinkles. As for the surface quality of the molded fiber reinforced plastic, almost no cut openings were found on the surface.

(Example 5)
Using the same cut prepreg as in Example 4, the laminated structure of the cross-ply laminated body was set to [0/90/90/0]. As the tensile characteristics of the cross-ply laminate, load 1 was 3340N and load 2 was 4320N, satisfying load 1 × 0.5 <load 2 <load 1 × 1.5, but shaping at room temperature was difficult. Met. When heated using a dryer, the shape followability was improved, and it was possible to follow the mold without wrinkles. When the tensile properties of the cross-ply laminate were measured in an environment of 60 ° C., the load 1 was 52 N and the load 2 was 45 N.

(Example 6)
Using the same cut prepreg as in Example 4, a 1000 m × 1000 m cross-ply laminate was produced. Originally, the cut prepreg was 500 mm wide, but a 1000 mm x 500 mm cut prepreg was cut out so that the orientation direction of the reinforcing fibers was the longitudinal direction, and two 1000 mm x 1000 mm cut prepregs were pasted together. Then, the reinforcing fibers were laminated so that the orientation directions were orthogonal to each other to obtain a 1000 mm × 1000 mm cross-ply laminated body. After laminating, vacuuming was performed to strengthen the adhesion between the laminated layers. Although one layer was composed of two notched prepregs, it was supported by the other layer and was easy to handle.

The prepared cut prepreg was shaped into a mold having the shape shown in FIG. 9A to obtain a preform. It took about 20 minutes, but as shown in FIG. 9B, it was possible to accurately shape the uneven shape. The preform was sandwiched between double-sided molds and cured at 130 ° C. for 90 minutes to obtain a fiber reinforced plastic. The obtained fiber reinforced plastic had a good surface quality with almost no visible notch opening.

(Example 7)
A preform was obtained in the same manner as in Example 6 except that the cross-ply laminate was not completely aligned with the mold and was shaped so as to be partially floated from the mold as shown in FIG. 9 (c). The shaping time was 5 minutes, which was faster than that of Example 6. The preform was sandwiched between double-sided molds and cured at 130 ° C. for 90 minutes to obtain a fiber reinforced plastic. At the time of preformation, the obtained fiber-reinforced plastic had good surface quality, with the parts floating from the mold following the unevenness, and the notch opening was hardly visible.

(Comparative Example 1)
Two prepregs without cuts were laminated so that the fiber directions were at right angles to prepare a prepreg laminate.

As for the tensile characteristics of the prepreg laminate, it broke before reaching the tensile strain of 2% and a sudden load drop occurred, and the load 1 × 0.5 <load 2 <load 1 × 1.5 was not satisfied. The shape followability by hand lay-up was difficult to extend in the fiber direction, and wrinkles could not be eliminated.

(Comparative Example 2)
The cut pattern into the prepreg was set to the cut pattern shown in FIG. 6 (e), and a cross-ply laminated body was produced. A plurality of cuts are provided in the direction of crossing the reinforcing fiber at a right angle, and the projected length Ws obtained by projecting the cut in the direction perpendicular to the reinforcing fiber is 1 mm, which is equal to the length Y of the cut, and the fiber length L. Is divided into 24 mm reinforcing fibers. As shown in FIG. 8, small regions arranged in six directions were extracted and the distribution of cuts was measured. As a result, the average value of the population was 3.7 and the coefficient of variation was 38.3%.

As for the tensile characteristics of the cross-ply laminate, it broke before reaching the tensile strain of 2% and a sudden load drop occurred, and the load 1 × 0.5 <load 2 <load 1 × 1.5 was not satisfied. Therefore, it was impossible to measure the notch opening area ratio. The shape followability by hand lay-up was difficult to extend in the fiber direction, and wrinkles could not be eliminated. As for the surface quality of the molded fiber reinforced plastic, a notch opening was observed on the surface.

(Comparative Example 3)
The shape followability by hand lay-up was measured using a woven fabric prepreg F6343B-05 (reinforcing fiber: T300B-3000, resin: 2500) in which the reinforcing form of the reinforcing fiber is a woven structure. The shape followability by hand lay-up was good, and it was possible to shape it into a box shape without wrinkles.

(Comparative Example 4)
It was shaped into the mold of FIG. 9 using an unlaminated cut prepreg instead of a cross-ply laminate. Since the width of the cut prepreg is 1000 mm x 500 mm, I tried to shape the two cut prepregs independently, but before shaping, the cut prepreg wrinkled and the wrinkles could not be eliminated. I gave up shaping.

The angle θ formed by the cut and the reinforcing fiber is referred to as the cut angle θ in the table.

1: Prepreg 2: Notch 3: 0 ° direction of cross-ply laminate 4: 90 ° direction of cross-ply laminate 5: 45 ° direction of cross-ply laminate 6: Prepreg fiber direction 7: For prepreg reinforcing fibers On the other hand, in the direction perpendicular to 8: a small area with a diameter of 10 mm 9: an intermittent straight line formed by a plurality of cuts 10: an intermittent diagonal cut (a positive angle with respect to the fiber direction)
11: Intermittent diagonal cut (negative angle with respect to fiber direction)
12: Preform

Claims (13)

A cloth composed of a plurality of prepregs having a volume content Vf of unidirectionally oriented reinforcing fibers and reinforcing fibers containing a resin of 45 to 65%, and comprising prepregs in which the fiber directions intersect at substantially right angles. It is a ply laminate
Each prepreg is a cut prepreg having a plurality of cuts across the reinforcing fibers, in which substantially all the reinforcing fibers have a fiber length (L) of 10 to 300 mm, and 10 pieces arbitrarily selected from the prepregs. When the number of cuts contained in a small circular region with a diameter of 10 mm is used as the population, the average value of the population is 10 or more, the coefficient of variation is 20% or less, and
A cross-ply laminate that satisfies the tensile property 1 shown below in an environment of 25 ° C. or the tensile property 2 shown below in an environment of 60 ° C.
(Tensile property 1) When the fiber direction of any of the prepregs in the cross-ply laminate is set to 0 °, the cross-ply laminate is subjected to 1% tensile strain in the 0 ° direction with respect to the cross-ply laminate. Let the load generated in the 0 ° direction of the body be the load 1, and the load generated in the 0 ° direction of the cross-ply laminated body when a 2% tensile strain is applied to the cross-ply laminated body in the 0 ° direction is the load 2. Then, the load is 1 × 0.5 <load 2 <load 1 × 1.5.
(Tensile property 2) When the fiber direction of any of the prepregs in the cross-ply laminate is set to 0 °, the cross-ply laminate is subjected to 1% tensile strain in the 0 ° direction with respect to the cross-ply laminate. Let the load generated in the 0 ° direction of the body be the load 1, and the load generated in the 0 ° direction of the cross-ply laminated body when a 2% tensile strain is applied to the cross-ply laminated body in the 0 ° direction is the load 2. Then, the load is 1 × 0.5 <load 2 <load 1 × 1.5. In an environment of 25 ° C., when the fiber direction of any of the prepregs in the cross-ply laminate is 0 ° and a tensile strain of 2% is applied to the cross-ply laminate in the 0 ° direction, the cloth is crossed. Whether the total area of the cut openings (area ratio of the cut openings) in the area of the ply laminate is 0% or more and 1% or less.
When the fiber direction of any of the prepregs in the cross-ply laminate is set to 0 ° in an environment of 60 ° C. and a tensile strain of 2% is applied to the cross-ply laminate in the 0 ° direction, the cloth is crossed. The cross-ply laminate according to claim 1, wherein the total area of the cut openings (area ratio of the cut openings) in the area of the ply laminate is 0% or more and 1% or less. The plurality of cuts in the prepreg form an intermittent straight line.
The plurality of cuts forming the intermittent straight line are substantially the same length Y.
The cross-ply laminate according to claim 1 or 2 , wherein the distance between adjacent cuts is larger than 3 times Y for the plurality of cuts forming the intermittent straight line. The cross-ply laminate according to any one of claims 1 to 3 , wherein the projected length Ws when the cut in the prepreg is projected in the direction perpendicular to the reinforcing fibers in the prepreg is 30 μm to 1.5 mm. body. The cross-ply laminate according to any one of claims 1 to 4 , wherein the absolute value of θ is 2 to 25 °, where θ is the angle formed by the notch in the prepreg and the reinforcing fiber. The plurality of cuts in the prepreg form an intermittent straight line.
When the angle formed by the cut and the reinforcing fiber is θ, the absolute value of θ is substantially the same.
The cross-ply laminate according to any one of claims 1 to 5 , wherein the number of cuts in which θ is positive and the number of cuts in which θ is negative are substantially the same. Among the cuts in which the prepreg is close to any cut A inserted in the prepreg, there are four or more cuts C in which the shortest distance is closer than that of the cut B in which the positive and negative of θ are the same and the positive and negative of θ are different. The cross-ply laminate according to claim 6, which is present. The plurality of cuts in the prepreg are straight and substantially the same length Y.
The cross-ply laminate according to any one of claims 1 to 7 , wherein the shortest distance between adjacent cuts is longer than the length Y of the cuts. The cross-ply laminate according to any one of claims 1 to 8 , wherein the resin is a thermosetting resin. The cross-ply laminate according to any one of claims 1 to 9 , which has an area of 0.5 m2 or more. A method for producing a fiber reinforced plastic, wherein the cross-ply laminate according to any one of claims 1 to 10 is pressed against a mold to form a preform, and then the preform is solidified. The method for producing a fiber reinforced plastic according to claim 11 , further comprising a step of heating the cross-ply laminate when pressing the cross-ply laminate against a mold. The method for producing a fiber reinforced plastic according to claim 11 or 12 , wherein the method of pressing against the mold is manual.

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