JP6965530B2 - Notch prepreg and method of manufacturing notch prepreg - Google Patents

Description

The present invention relates to a cut prepreg suitable as an intermediate base material for a fiber reinforced plastic having good shape followability during molding and high mechanical properties when solidified, and a method for producing the same.

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.

SMC (Sheet Molding Compound) is an intermediate base material for fiber reinforced plastics. SMC is a sheet-like base material in which chopped strands, which are usually cut to about 25 mm and impregnated with a thermosetting resin, are randomly dispersed, and is a material suitable for molding fiber reinforced plastics having a complicated three-dimensional shape. Are known. However, in the fiber reinforced plastic molded by SMC, uneven distribution and uneven orientation of chopped strands inevitably occur, so that the mechanical properties of the molded product deteriorate or the values vary widely. As a method for molding a fiber-reinforced plastic that stably exhibits high mechanical properties, a method is known in which a prepreg impregnated with a resin is laminated on continuous reinforcing fibers and molded by an autoclave. However, in a prepreg using continuous fibers, wrinkles and tension of reinforcing fibers occur due to insufficient deformability, and it is difficult to form a complicated shape such as a three-dimensional shape.

In order to make up for the above-mentioned shortcomings of the material, it is said that by making a cut in the prepreg composed of continuous reinforcing fibers and resin to divide the reinforcing fibers, it is possible to flow and the variation in mechanical properties is reduced. The base material is disclosed (for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 63-247012 Japanese Patent No. 5167953

Although the methods described in Patent Document 1 and Patent Document 2 have greatly improved mechanical properties and reduced variations as compared with SMC, Patent Document 1 cannot be said to have sufficient strength to be applied as a structural material. There is room for improvement in three-dimensional shape followability. Further, Patent Document 2 has a problem that although it exhibits higher strength and has good three-dimensional shape followability, the surface quality is inferior to that of the prepreg due to the opening of the notch during molding.

In view of the background technology, the present invention provides an intermediate base material (cut prepreg) capable of obtaining a fiber reinforced plastic which is excellent in three-dimensional shape followability and exhibits high surface quality and excellent mechanical properties when solidified. To provide.

The present invention employs the following means in order to solve such a problem. That is, it is as follows.
(1) A cut prepreg having a plurality of cuts for dividing the reinforcing fibers in at least a part region of the prepreg containing the reinforcing fibers oriented in one direction and the resin, and is arbitrarily selected from the regions. A cut prepreg having an average value of 10 or more and a coefficient of variation of 20% or less when the number of cuts contained in 10 small circular regions having a diameter of 10 mm is used as the population.
(2) A method for producing a cut prepreg having a plurality of cuts for dividing the reinforcing fiber in at least a part of a region of the prepreg containing the reinforcing fiber and the resin.
A method for manufacturing a cut prepreg, which comprises a step 1 of inserting a plurality of cuts 1 into a prepreg and a step 2 of inserting a plurality of cuts 2 which do not overlap with the cut 1 into the prepreg.

According to the present invention, it is possible to obtain an intermediate base material which is excellent in three-dimensional shape followability and exhibits high quality surface quality and excellent mechanical properties when made into a fiber reinforced plastic.

It is a conceptual diagram of the cut prepreg of this invention. The non-homogeneous cut pattern (a) and the homogeneous cut pattern (b, c) are illustrated. This is an example of a cutting pattern used for the cutting prepreg of the present invention. This is an example of a cutting pattern used for the cutting prepreg of the present invention. This is an example of a cutting pattern used for the cutting prepreg of the present invention. This is an example of a cutting pattern used for the cutting prepreg of the present invention. It is a mold for press molding. These are six examples of cut patterns used in the cut prepreg of the present invention. These are five examples of cut patterns not used in the cut prepreg of the present invention. It is a small area extraction pattern in a cut prepreg in an Example.

In order to obtain an intermediate base material that has excellent followability to a three-dimensional shape and exhibits excellent mechanical properties when used as a fiber reinforced plastic, the present inventors have diligently studied and made a unidirectionally oriented reinforcing fiber. By inserting multiple cuts that divide the reinforcing fibers into at least a part of the prepreg containing the resin and discontinuing the reinforcing fibers, it is possible to improve the followability to the three-dimensional shape and solve this problem. I investigated.

Specifically, the number of cuts contained in 10 circular small regions having a diameter of 10 mm, which are arbitrarily selected in the region where a plurality of cuts are inserted (hereinafter referred to as the cut region), is defined as the population. In this case, the incision prepreg has an average value of 10 or more and a coefficient of variation of 20% or less in the population (hereinafter, a state in which the average value of the population is 10 or more is high density and a coefficient of variation is 20% or less). Is called homogeneous).

FIG. 1A shows a conceptual diagram of a cut prepreg including a cut region 3 in which a plurality of cuts 2 are inserted into the prepreg 1. The cut region may be present in only a part of the prepreg or the entire prepreg as long as it is in at least a part of the prepreg, and the prepreg contains a plurality of cut regions. You may. The cut region may exist at any part of the cut prepreg, but when molded using the cut prepreg to make a fiber reinforced plastic, it exists in a region including a three-dimensional shape such as a curved surface or unevenness. It is preferable to do so. Within the cut region, all the reinforcing fibers may be divided by the cut, or may contain reinforcing fibers that are not divided by the cut. Further, the angle formed by the orientation direction of the reinforcing fibers and the cut may be two or more types, or the length of the reinforcing fibers divided by the cut may be two or more types.

FIG. 1B shows a state in which 10 circular small regions 4 having a diameter of 10 mm are extracted in the cut region 3 (hereinafter, the circular small regions 4 having a diameter of 10 mm are abbreviated as small regions). It is preferable to extract the small areas densely within the cut area so that the small areas do not overlap, but when the cut area is not large enough to extract all 10 small areas without overlapping. May be extracted so that the small areas overlap each other. However, in order to measure the above-mentioned population mean and coefficient of variation more accurately, a small area must not be set beyond the boundary of the cut area. The boundary of the cut area is a line segment group connecting the line segments connecting the ends of the cuts, and all the cuts are included in the line segment group, and the total length of the line segment groups is the minimum. Let it be a line segment group.

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 of the above-mentioned population and the coefficient of variation of the above-mentioned population 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). NS.

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 cut prepreg is deformed. A 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. As shown in FIGS. 2 (a) to 2 (c), the fiber length L is a reinforcement divided by an arbitrary cut and a cut (paired cut) closest to the reinforcing fiber direction. Refers to the length of the fiber. 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 in the cut region, the smaller the variation in the opening of each cut when the cut prepreg is deformed. Therefore, stable mechanical properties are obtained when the fiber reinforced plastic is used. Is expressed. 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. 1 (b), 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 cut has already been described in Patent Document 2, but for example, the cut pattern described in FIG. 2 of Patent Document 2 is enlarged or reduced so that the average value of the population becomes 10 or more. In this case, the fiber length of the reinforcing fibers must be 10 mm or less, and when the fiber length of the reinforcing fibers is 10 mm, the average value of the population is 5 or less, which is the distribution of cuts. The density of is small.

Further, in many existing cutting patterns represented by FIG. 1 (A) of Patent Document 1, it is shown in FIG. 2 (a) (when the document is not specified, it is the figure of the present specification; the same applies hereinafter). As described 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 appear prominently. As shown in FIG. 2B, by shifting adjacent cuts in fine cycles such as L / 5 and L / 6 instead of L / 2, the cuts are evenly distributed in the cut prepreg. It becomes a pattern, and when the cut prepreg is stretched, the stretched part is not biased and uniform deformation is possible, and the opening of each cut is suppressed (hereinafter, the cuts are evenly distributed). The pattern is sometimes referred to as a homogeneous cut pattern). Further, instead of shifting the adjacent cuts in a step-like manner as shown in FIG. 2 (b), the adjacent cuts may be shifted as shown in FIG. 2 (c). In FIG. 2C, 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. 2C) are cut. The distance between the indentation s1 and the incision s2) is 2L / 5, which is longer than the L / 5 in FIG. 2 (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. 2A, 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 length of the reinforcing fiber after splitting is preferably 10 mm or more, more preferably 15 mm or more, still more preferably 20 mm or more. Even when the length of the reinforcing fibers is 20 mm or more, by reducing the number of reinforcing fibers that are divided by each cut, the cut pattern in which the cuts are densely distributed (hereinafter, high-density cuts) (Sometimes referred to as a pattern) can be obtained, and the effect of improving mechanical properties can be expected due to the long length of the reinforcing fibers and the small depth of cut. As shown in FIG. 2B, by shifting the adjacent cuts in a fine cycle, a homogeneous and high-density cut pattern can be realized while maintaining the fiber length. The same applies when the notch is inserted diagonally with respect to the orientation direction of the reinforcing fibers.

As an aspect of the cut prepreg in the present invention, it is preferable that the same reinforcing fiber is not divided between the arbitrary cut A and another cut B that is in close contact with the cut. Reinforcing fibers that are separated by the notches that are in close contact with each other become relatively short reinforcing fibers, which is a factor that deteriorates the mechanical properties when made into fiber reinforced plastic. Further, since there is a reinforcing fiber between the notch A and the notch B which is in close contact with the notch A, which is not divided by either the notch A or the notch B, the notch A is used when the fiber reinforced plastic is used. And the notch B becomes difficult to connect due to damage, and the mechanical properties are improved.

FIG. 3 shows a part of the notch region, and there are a plurality of reinforcing fibers 5 between the notch A and the notch B which is in close contact with each other, and the notch A and the notch B have the same reinforcement. The fibers are not broken. As shown in FIG. 3A, the reinforcing fiber 5 between the notch A and the notch B may be separated by the notch A and the notch C which is not in close contact with the notch B, or FIG. 3 As in (b), the reinforcing fiber 5 between the notch A and the notch B does not have to be divided by the notch. The distance between the cuts that are in close contact with each other is preferably 0.5 times or more, more preferably 1 of Ws, in the direction perpendicular to the reinforcing fibers and the projected length Ws obtained by projecting the cuts on a plane perpendicular to the reinforcing fibers. More than double.

In the incision prepreg in which the incisions are distributed at high density, the distance between the incisions becomes short, and when the incisions that are in close contact divide the same reinforcing fiber, very short reinforcing fibers are mixed. Therefore, by providing an interval so that the cuts that are in close contact with each other do not divide the same reinforcing fiber, even if the cut pattern is high-density, the mixing of short reinforcing fibers is suppressed and stable. It is possible to express mechanical properties.

As a preferred embodiment of the cut prepreg in the present invention, as shown in FIG. 4, the cuts have substantially the same length Y (hereinafter, Y is also referred to as a cut length), and the distance between the cuts that are in close contact with each other. Reference numeral 6 denotes a notched prepreg that is longer than 0.5 times 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). In the present invention, the cut may be straight or curved, and in either case, the line segment connecting the ends of the cut is defined as the cut length Y.

The distance between the closest cuts means the shortest distance between the closest cuts. If the closest cuts are close to each other, or if the fiber reinforced plastic is damaged, the damage makes it easier to connect the cuts. Therefore, the distance between the most recent cuts is 0, which is the cut length Y. It is preferably larger than .5 times. The distance between the notches that are in close contact with each other is more preferably 0.8 times or more of Y, and further preferably 1.0 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, the cut pattern in which the cuts are separated from each other, that is, the distance between the cuts that are in close contact with each other may be made larger than 0.5 times the cut length Y. It is especially important for improving mechanical properties. Furthermore, in the case of a cut prepreg in which all the reinforcing fibers are divided in the cut region to improve the shapeability, the shortest distance between the cuts that are in close contact with each other should be larger than 0.5 times the cut length Y. Moreover, since the notches that are in close contact with each other do not divide the same reinforcing fiber, the mechanical properties can be exhibited to the maximum without impairing the followability to the three-dimensional shape and the surface quality.

A preferred embodiment of the cut prepreg in the present invention is a cut prepreg in which the cut is inserted diagonally with respect to the orientation direction of the reinforcing fibers. When the cut is curved, it means that the line segment connecting the ends of the cut is diagonal with respect to the orientation direction of the reinforcing fibers. By making the cut diagonal with respect to the orientation direction of the reinforcing fibers, it is possible to improve the followability of the cut prepreg to the three-dimensional shape and the mechanical properties of the fiber-reinforced plastic. Assuming that the orientation direction of the reinforcing fibers and the angle formed by the cut are θ, it is preferable that θ is 2 to 60 °. 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 25 ° 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 a cut with the blade, and it becomes difficult to insert while ensuring the position accuracy of the cut. From this point of view, it is more preferable that the absolute value of θ is 2 ° or more.

Not only when the cuts are distributed in high density, the smaller the absolute value of θ, the better the mechanical properties can be expected. On the other hand, especially when all the reinforcing fibers are divided in the cut region, the cuts are close to each other. Therefore, there is a concern that the damage generated by the incision will be easily connected and the mechanical properties will deteriorate. However, any incision and another incision closest to the incision do not divide the same reinforcing fiber, and the incisions are substantially the same length Y and are in close contact. Since the distance between the cuts is longer than 0.5 times Y, further improvement in mechanical properties can be expected as compared with the case where the cuts are perpendicular to the orientation direction of the reinforcing fibers. 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 Patent Document 2, it is a known technique to insert a notch diagonally into a reinforcing fiber, but as shown in FIGS. 2 (f) and 12 of Patent Document 2, they are adjacent to each other. In a cutting pattern in which the cutting is deviated by L / 2 with respect to the fiber length L of the reinforcing fiber, when L is long and the cutting length is small, the same as the phenomenon shown in FIG. 2 is homogeneous. It is not possible to realize a smooth cut pattern, and when the cut prepreg is stretched, it is easy to stretch the part where the cut is dense, and even if it is made of fiber reinforced plastic, the cuts are close to each other, so the cuts are connected to each other. It is easy and may cause deterioration of mechanical properties. By applying the diagonal cut to the homogeneous cut arrangement as shown in FIGS. 2 (b) and 2 (c), the effect of improving the mechanical characteristics by inserting the cut diagonally is more effectively exhibited. can.

A preferred embodiment of the cut prepreg in the present invention is a cut (referred to as a normal cut) in which the absolute value of the angle θ formed by the cut and the orientation direction of the reinforcing fibers is substantially the same and θ is positive. Examples thereof include a cut prepreg including a cut in which θ is negative (referred to as a negative cut). 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. By inserting not only a positive cut but also a negative cut in the cut prepreg, if in-plane shear deformation occurs near the positive cut when the cut prepreg is extended, the shear deformation in the opposite direction near the negative cut As a macro, it is possible to suppress in-plane shear deformation and extend it.

More preferably, it is a cut prepreg that includes approximately the same number of positive and negative cuts. Including approximately the same number of positive and negative cuts 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 θ that is a positive angle and the number of negative numbers when expressed as a percentage based on the number. It means that the number of θ that becomes is 45% or more and 55% or less (the same applies hereinafter).

By arranging the positive cuts and the negative cuts alternately as shown in FIG. 5, it becomes easy to secure the distance between the close cuts while inserting the cuts at a high density. Further, when laminating the obtained cut prepregs, in the case of a cut prepreg containing only positive cuts or negative cuts, whether the prepregs are viewed from the table even if the prepregs have the same reinforcing fiber orientation direction. The direction of the cut differs depending on the direction of the cut when viewed from the back. Therefore, when manufacturing fiber reinforced plastics, it is possible to increase the time and effort required to control the laminating procedure for laminating the same number of fibers having the same cutting direction or different cutting directions in the same reinforcing fiber direction each time. There is sex. Therefore, if the absolute value of the angle θ formed by the cut and the orientation direction of the reinforcing fiber is substantially the same and the number of positive cuts and negative cuts is approximately the same, the cut pattern is the same as that of a normal continuous fiber prepreg. It is possible to stack by handling.

In the case of a cut prepreg in which approximately the same number of positive cuts and negative cuts exist, and in the case of a cut pattern in which positive cuts and negative cuts are uniformly mixed, arbitrary cuts are made, especially in the case of a high-density cut distribution. It is easy to create a cut pattern in which the cut does not divide the same reinforcing fiber with another cut that is in close contact with the cut, and the distance between the cuts that are in close contact is longer than 0.5 times Y. Become. As a result, it is possible to suppress the connection of damage caused by the incision, and the mechanical properties are improved. In addition, when there are positive and negative cuts, it is difficult to find the opening of the cut even when the cut prepreg is extended, and good surface quality can be obtained when using fiber reinforced plastic, but the cut distribution is high. In the case of, the cut becomes finer, and a better surface quality can be obtained. The cut pattern is also effective when cutting all the reinforcing fibers in the cut region, and it is possible to improve the mechanical properties and the surface quality while maintaining the followability to the three-dimensional shape. Also, when inserting a cut into the prepreg using a blade, if only a positive cut or a negative cut is inserted, the force that moves the prepreg in the width direction acts when it is pushed out by the blade, so the prepreg is wide. Although it is easy to shift in the direction, by using a blade that contains approximately the same number of positive and negative cuts, the prepreg is less likely to shift in the width direction, and the cut can be inserted with high accuracy.

More preferably, with respect to the distance between an arbitrary cut and another cut that is in close contact on the extension line of the cut, the length differs between the distance between the positive cuts and the distance between the negative cuts. Included prepreg. FIG. 6 shows a cut prepreg in which approximately the same number of positive cuts and negative cuts are inserted. The positive cuts are arranged on the straight line 9 and the negative cuts are arranged on the straight line 10, and the interval between the positive cuts on the straight line 9 is smaller than the interval between the negative cuts on the straight line 10. By arranging the cuts in this way, it is possible to secure a uniform, high-density and close distance between the cuts, and it is possible to create a cut pattern that does not divide the reinforcing fibers with the same cuts that are in close contact with each other. be. Furthermore, regarding the distance between an arbitrary cut and another cut that is in close contact on the extension line of the cut, the length between the positive cuts and the distance between the negative cuts is the same as that of the case where the length is the same. It is possible to increase the length of the reinforcing fibers and maintain the mechanical properties even if the cuts are distributed at high density. Note that the presence of a cut on the extension line of the cut means that the angle between the straight line extending the cut and the straight line connecting the closest points of the target cuts is within 1 °. ..

Regarding the distance between an arbitrary cut and another cut that is in close contact on the extension line of the cut, the length should be different depending on the distance between the positive cuts and the distance between the negative cuts. Therefore, the length of the reinforcing fibers can be made longer even at a high density, and even when all the reinforcing fibers are divided within the cutting region, any cutting and the recent contact with the cutting are made. With another cut, the same reinforcing fiber is not divided, and it is easy to obtain a cut pattern in which the distance between the cuts that are in close contact with each other is longer than 0.5 times the cut length Y. Thereby, the mechanical properties can be improved more effectively without impairing the surface quality and the followability to the three-dimensional shape. That is, approximately the same number of positive cuts and negative cuts are inserted, and the distance between the positive cuts and the negative cuts regarding the distance between any cut and another recently adjacent cut that exists on the extension line of the cut. The length differs depending on the distance between the indentations, and an arbitrary incision and another incision that is in close contact with the incision do not divide the same reinforcing fiber, and the distance between the incisions that are in close contact with each other is the incision length. The cut pattern, which is longer than 0.5 times the length of Y and in which substantially all the reinforcing fibers are divided into fiber lengths of 15 mm or more in the cut region, has three-dimensional shape followability, surface quality, and mechanical properties. It is particularly preferable from the viewpoint of. As shown in FIGS. 1, 2 (d), and 14 (d) of Patent Document 2, a cut pattern in which a positive cut and a negative cut are inserted is known, but both cut patterns are described in the present specification. Similar to FIG. 2A of the book, the adjacent cuts are cut patterns in which the fiber length L of the reinforcing fiber is deviated by half, and the longer L and the smaller the cut, the denser the cut arrangement occurs. It will be easier to do. Adjacent cuts are not limited to L / 2 as shown in FIGS. 2 (b) and 2 (c), but can be shifted to obtain a high-density and uniform cut pattern.

In addition, when manufacturing the notch prepreg, a protective sheet is attached to the surface of the notch prepreg, and the notch is inserted into the prepreg through the protective sheet to make the rotary blade roll and the notch prepreg adhere. It may be suppressed. When laminating the cut prepregs manufactured in this way, it is necessary to peel off the protective sheet. There is. Therefore, from the viewpoint of handleability of the cut prepreg sheet, it is preferable that the distance between the cuts that are in close contact with each other is longer than 0.5 times the cut length Y. When substantially the same number of positive cuts and negative cuts are arranged in a mixed manner, it is difficult to connect the cuts on the protective sheet when the protective sheet is peeled off, and the handleability of the cut prepreg sheet is further improved. Regarding the distance between an arbitrary cut and another cut that is in close contact on the extension line of the cut, if the length differs between the distance between the positive cuts and the distance between the negative cuts, it is considered as a normal cut. The negative cuts can be arranged more evenly, the protective sheet is less likely to be torn off, and the handleability of the cut prepreg is further improved. Typical materials for the protective sheet include polymers such as polyethylene and polypropylene, which play a role in preventing the resin from sticking to the blade when inserting a notch into the prepreg with a blade, and the notch prepreg. It has the role of protecting the surface of the notched prepreg from foreign matter such as dust during storage.

In the present invention, the resin contained in the notch prepreg may be a thermoplastic resin or a thermocurable resin, and examples of the thermoplastic resin include polyamide (PA), polyacetal, polyacrylate, polysulphon, ABS, polyester, and acrylic. , Polybutylene terephthalate (PBT), Polycarbonate (PC), Polyethylene terephthalate (PET), Polyethylene, Polypropylene, Polyphenylene sulfide (PPS), Polyetheretherketone (PEEK), Polyetherimide (PEI), Polyetherketoneketone (PEI) PEKK), liquid crystal polymer, vinyl chloride, fluororesin such as polytetrafluoroethylene, silicone and the like. The thermosetting resin may be any resin as long as it causes a cross-linking reaction by heat to form at least a partial three-dimensional cross-linked structure. Examples of these thermosetting resins include unsaturated polyester resins, vinyl ester resins, epoxy resins, benzoxazine resins, phenol resins, urea resins, melamine resins and polyimide resins. 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. Further, a filler may be contained in order to improve heat resistance, conductivity and the like.

The reinforcing fiber contained in the cut prepreg of the present invention 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.

By setting the volume content Vf of the reinforcing fibers to 70% or less, the reinforcing fibers in the cut portion are displaced, bridging is effectively suppressed, and shape followability and molding defects such as voids are suppressed. Can be done. From this point of view, it is more preferable that Vf is 70% or less. Further, the lower the Vf, the more the bridging can be suppressed, but when the Vf is smaller than 40%, it becomes difficult to obtain the high mechanical properties required for the structural material. From this point of view, it is more preferable that Vf is 40% or more. A more preferred range of Vf is 45-65%, even more preferably 50-60%.

The cut prepreg may be manufactured using a prepreg in which the reinforcing fibers are partially impregnated with resin (that is, partially impregnated). By using a cut prepreg in which the reinforcing fibers are partially impregnated with resin, the unimpregnated portion of the reinforcing fibers inside the prepreg becomes an in-plane flow path, and the air trapped between the layers of the cut prepreg during lamination. Gases such as volatile components from the prepreg and the prepreg are easily discharged to the outside of the prepreg (such a gas flow path is called a degassing path). On the other hand, if the impregnation rate is too low, peeling may occur between the reinforcing fiber and the resin, and the cut prepreg may be split in two at the unimpregnated portion when the cut prepreg is laminated, resulting in inferior workability. The impregnation rate is preferably 10 to 90% because voids may remain if the impregnation time during molding is not long. From this point of view, the more preferable upper limit of the impregnation rate range is 70%, the more preferable upper limit is 50%, and the more preferable lower limit of the impregnation rate range is 20%.

The cut prepreg of the present invention may have a resin layer on its surface. Due to the presence of the resin layer on the surface of the cut prepreg, an interlayer resin layer is formed between the cut prepregs when the cut prepregs are laminated. As a result, when an out-of-plane impact load is applied, cracks are induced in the flexible interlayer resin layer, and the presence of the thermoplastic resin suppresses peeling due to the high toughness, thereby suppressing the residual compressive strength after the out-of-plane impact. It is suitable as a main structural material that requires high safety such as aircraft.

The cut prepreg of the present invention can be laminated and applied to press molding and autoclave molding. The lamination method can be arbitrarily selected depending on the application, but a pseudo-isotropic laminate or a cross-ply laminate is particularly preferable in consideration of suppression of warpage due to residual heat stress and a balance of mechanical properties. At the time of laminating, in order to further increase the fluidity of the laminated base material, a base material in which reinforcing fibers are randomly oriented such as SMC, a resin film, or the like may be appropriately laminated.

Hereinafter, a method for producing a cut prepreg having a plurality of cuts for dividing the reinforcing fibers in at least a part region of the prepreg containing the reinforcing fibers and the resin will be described.

The means for inserting the notch into the prepreg may be mechanically inserted with a blade or burned off with a heat source such as a laser. In order to insert the incision with higher density and accuracy, a method of pressing the roll in which the blade is arranged in a fixed position against the prepreg is preferable.

As another preferable method for producing the cut prepreg, a step 1 of inserting a plurality of cuts 1 into the prepreg and a step 2 of inserting a plurality of cuts 2 which do not overlap with the cut 1 into the prepreg. It may be a method including. Specifically, it is a device that inserts a notch by attaching a punching die with a blade to the elevator and pressing the punching die against the prepreg. After inserting the notch 1, the prepreg or the elevator is moved to cut. An example is a method of inserting the notch 2 at a position that does not overlap with the indentation 1. It is also one of the preferable means to use a rotary blade instead of the punching die. Further, the size and shape of the cut area may be different between the cut 1 and the cut 2.

The method for producing a cut prepreg in the present invention can also be preferably used when the cut pattern has a cut in which the angle formed by the orientation direction of the cut and the reinforcing fiber is different. Specifically, the angle θ1 formed by the notch 1 and the reinforcing fiber is positive or negative, and the angle θ2 formed by the notch 2 and the reinforcing fiber is different from the angle θ1 formed by the notch 2. In particular, when inserting a notch with a blade, it may be difficult to produce a blade in which blades of different angles are arranged at high density. A notch can be inserted in the density.

The method for producing a cut prepreg in the present invention can be preferably applied not only to a prepreg in which reinforcing fibers are oriented in one direction, but also to a case where the reinforcing form is a woven fabric or a random mat.

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 example, the preparation of the cut prepreg, the density distribution of the cut, the followability to the three-dimensional shape, the grade on the surface of the fiber reinforced plastic, the tensile elastic modulus, and the tensile strength were measured according to the following methods. 8 and 9 show a part of the cut patterns used in Examples and Comparative Examples, respectively, and each cut pattern is repeated in the prepreg plane on the cut prepreg. The results of Examples 1 to 7 and Comparative Examples 1 to 5 are as shown in Table 1.

<Manufacturing of cut prepreg>
"Treca" (registered trademark) prepreg sheet P3052S-15 (reinforcing fiber: T700S, resin composition resin: 2500, volume content of reinforcing fiber: 56%, single-sided paper pattern laminated) prepared and provided with a blade The notch was inserted by pressing the prepreg sheet against the roll (rotary blade roll) around which the plastic was wound. In each of the examples, the cut region was the entire prepreg, and the cut pattern was set so that all the cuts had the same length and the lengths of the reinforcing fibers divided by the cuts were also the same. The prepreg sheet is supported by the release paper which is the sheet base material A, and the polyethylene film is in close contact with the surface opposite to the release paper. At the time of inserting the cut, the polyethylene film was penetrated, and the cut was inserted into the paper pattern to about 50% of the thickness.

<Confirmation of the cut pattern of the cut prepreg>
After inserting the cut, take a picture of the surface of the cut prepreg with a digital microscope and use the measurement software of the digital microscope to make a cut to check whether the cut is inserted into the cut prepreg as intended. Distribution, length of cut, length of reinforcing fiber divided by the cut, angle between the orientation direction of the reinforcing fiber and the cut (cut angle), plane where the cut is perpendicular to the orientation direction of the reinforcing fiber The projected length Ws projected on the surface, the distance between the cuts that are in close contact with each other, and the distance between the cuts existing on the extension line of the cuts were measured. A plurality of captured images were connected to form a 50 mm × 50 mm region, and measurement was performed.

First, the cut pattern was extracted by extracting the line segments connecting the ends of the cuts existing on the image in all the cuts. However, the line segment is not extracted for the notch in contact with the edge of the image. Ten circular small regions having a diameter of 10 mm were drawn on the image in a hexagonal close-packed arrangement as shown in FIG. 10, and the line segments contained in each small region were counted. At this time, the line segment tangent to the boundary of the small area was also considered to be included in the small area. Using the line fractions contained in the 10 small regions as the population, the average value and the coefficient of variation of the population were calculated using Equations 1 and 2.

Regarding the length of the cut, the length of the line segment corresponds to the length of the cut, and the average value of the lengths of all the line segments existing on the image was calculated. If the lengths of all the line segments were within the range of ± 5% of the average value, all the cuts were considered to be substantially the same, and the average value was used as the representative value as the cut length.

The cut angle was the angle formed by the orientation direction (fiber direction) of the reinforcing fibers and the line segment. The cut angle is measured for all line segments to calculate the average value, and if all the cut angles are within the range of the average value ± 1%, it is considered that all the cut angles are substantially the same. , The average value was used as the representative value and the cutting angle was used. When there are positive and negative cuts, the above calculation was performed using the absolute value of the cut angle as a representative value.

The length of the reinforcing fiber divided by the notch was defined as the distance in the fiber direction between the lines adjacent to the fiber direction. The distances at three points were measured for a set of line segments, and the average value was used as the line segment distance, and the line segment distances were measured in the same manner for all the line segments that could be extracted. The average value of the line-breaking distance was taken as the length of the reinforcing fiber divided by the notch.

For Ws, for each line segment, a straight line was drawn in contact with the end of each line segment and parallel to the fiber direction, and the distance between the straight lines was defined as the distance between the straight lines. The distance between straight lines was measured for all line segments, and the average value was taken as Ws as a representative place.

The distance between the notches that are in close contact with each other is the shortest distance between the end of the line segment and the line segment closest to the end of any line segment. For the ends of all line segments, the shortest distance between the end and the nearest line segment was measured, and the average value was used as the distance between the most recently contacted cuts. Further, in any cut, when there are a plurality of reinforcing fibers that are not cut by the two cuts between the cuts that are in close contact with each other, the arbitrary cut and another cut that is in close contact with the cut are different. The notch was considered not to divide the same reinforcing fiber.

The distance between the cuts existing on the extension line of the cut was measured when there were a positive cut and a negative cut. With respect to a normal cut, a line segment extracted from any normal cut is extended, and there is a line segment that comes into contact with or approaches the line segment extracted from another normal cut as much as possible, and the center of the two line segments. When the angle between the straight line connecting the two line segments and one of the line segments is 1 ° or less, it is considered that the two line segments exist in one straight line. As shown in the distance 11 between the regular cuts in FIG. 6, the distance between the closest end points of the two line segments is defined as the distance between the cuts that are in close contact with each other. Similarly, for the negative cut, the distance 12 between the cuts adjacent to each other in the same straight line was measured.

<Confirmation of surface quality after press molding>
The orientation direction of the reinforcing fibers of the cut prepreg was set to 0 °, and _{a 150 mm × 150 mm laminate laminated in [+ 45/0 / −45 / 90] 2s} was prepared and press-molded with a die having the shape shown in FIG. Was done. The molding temperature was 150 ° C. and the press pressure was 3 MPa. The surface quality of the molded product was evaluated in the following three stages.

A: The existence of the notch is almost unrecognizable B: The opening of the notch is small but the existence of the notch is recognized C: The notch has a large opening and the notch opening is conspicuous.

<Tensile modulus / tensile strength of fiber reinforced plastic>
A laminated body of the cut prepreg having a thickness of 300 mm × 300 mm and a laminated structure of [+ 45 / −45 / _{0/90] 2s was prepared from the cut prepreg.} At the time of lamination, the polyethylene film was laminated so that the peeled surface was on top. Then, the laminated body of the cut prepreg was press-molded by a press machine using a mold of 350 mm × 350 mm under a surface pressure of 3 MPa to form a fiber reinforced plastic of 350 mm × 350 mm. The temperature at the time of pressing was 130 ° C., and after holding for 90 minutes after pressing, the mold was removed and left at room temperature for cooling. A 25 mm × 250 mm test piece was cut out so that the 0 degree direction of the reinforcing fiber was the longitudinal direction, and a tensile test was performed by the method specified in 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 was set as the cut pattern as shown in FIG. 8 (a). The length of the reinforcing fiber divided by the notch insertion is 8 mm, the projected length Ws projected on the plane perpendicular to the orientation direction of the reinforcing fiber is 1 mm, and the angle between the orientation direction of the reinforcing fiber and the notch is It was 90 °. The reinforcing fiber bundles divided by the notch were arranged with a deviation of 1/3 of the reinforcing fiber length L with respect to the adjacent reinforcing fiber bundles.

The press-molded product had a notch opening on the surface. Although the length of the reinforcing fiber was short, the tensile elastic modulus was high.

(Example 2)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 8 (b). The length of the reinforcing fiber divided by the cut insertion is 12 mm, the projected length Ws projected on the plane perpendicular to the orientation direction of the reinforcing fiber is 0.64 mm, and the orientation direction of the reinforcing fiber and the cut are formed. The angle was 40 °. The cuts have substantially the same length Y = 1 mm, and the distance between the cuts that are in close contact with each other is 1.7 mm, which is longer than 0.5 times Y. The reinforcing fiber bundles divided by the notch were arranged with a deviation of 1/6 of the reinforcing fiber length L with respect to the adjacent reinforcing fiber bundles.

The press-molded product had a notch opening on the surface. The tensile elastic modulus was the same as that of Example 1, but the tensile strength was improved as compared with Example 1.

(Example 3)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 8 (c). When confirmed after inserting the notch, the same reinforcing fiber was not divided between the arbitrary notch and another notch closest to the notch. The cuts had substantially the same length Y = 1 mm, and the distance between the cuts closest to each other was 1 mm, which was equivalent to Y. The length of the divided reinforcing fibers is 20 mm, the projected length Ws projected on a plane perpendicular to the orientation direction of the reinforcing fibers is 0.34 mm, and the angle between the orientation direction of the reinforcing fibers and the cut is 20 °. Met. An intermittent straight line was formed by multiple cuts.

The surface grades of the press-molded products were the same as those of Examples 1 and 2, but the tensile elastic modulus and the tensile strength were even higher than those of Examples 1 and 2.

(Example 4)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 8 (d). When confirmed after inserting the notch, the same reinforcing fiber was not divided between the arbitrary notch and another notch closest to the notch. 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 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 surface quality of the press-molded product was the same as that of Example 3, but the tensile strength was even higher than that of Example 3.

(Example 5)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 8 (e). As a result of confirmation after the incision was inserted, the incisions had substantially the same length Y = 1 mm, and the distance between the most adjacent incisions 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.

At the time of manufacturing the cut prepreg, in the cut pattern of Example 2, when the prepreg sheet was pressed against the rotary blade roll, the prepreg sheet tended to shift in the width direction as the pressing distance became longer. In Example 5, the deviation of the prepreg in the width direction was small. At the time of laminating, there are positive cuts and negative cuts regardless of which side is on the release paper side or the polyethylene film side, so that the cut prepreg can be laminated without worrying about the front and back. Further, in the cut pattern of Example 2, the polyethylene film was easily torn when the polyethylene film was peeled off, but in Example 5, the polyethylene film could be peeled off without being torn off.

A cut opening was observed in the press-molded product, but it was more difficult to see than in Example 2. The tensile elastic modulus and tensile strength were the same values as in Example 2.

(Example 6)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 8 (f). When confirmed after inserting the notch, the same reinforcing fiber was not divided between the arbitrary notch and another notch closest to the notch. 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 is 20 °, and includes approximately the same number of positive cuts in which θ is positive and negative cuts in which θ is negative. Further, the distance between the cuts existing on the extension line of the cut was different between the normal cut (3.4 mm) and the negative cut (24.5 mm).

Almost no cut opening was observed in the press-molded product. The tensile elastic modulus and tensile strength were higher than those in Examples 3 and 4.

(Example 7)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 8 (f). When confirmed after inserting the notch, the same reinforcing fiber was not divided between the arbitrary notch and another notch closest to the notch. The notches had substantially the same length Y = 1 mm, and the distance between the most adjacent cuts was 1.8 mm, which was 1.8 times that of Y. The length of the divided reinforcing fibers was 24 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. Further, the distance between the cuts existing on the extension line of the cut was different between the normal cut (33.3 mm) and the negative cut (44.7 mm).

Almost no cut opening was observed in the press-molded product. The tensile strength was higher than that of Example 6.

(Comparative Example 1)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 9 (a). The notch and another notch closest to the notch may be splitting the same reinforcing fiber, and the distance between the most recent cuts is 0.5 times the length of the notch. There was a shorter part than. The length of the divided reinforcing fibers is 20 mm or less, the projected length Ws projected on a plane perpendicular to the orientation direction of the reinforcing fibers is 1 to 2 mm, and the angle θ between the orientation direction of the reinforcing fibers and the cut is It was randomly inserted in the range of 90 °.

In the press-molded product, there was a part where the notch was large and opened. The tensile strength was lower than that of Examples 1 to 7.

(Comparative Example 2)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 9 (b). It was possible that the notch and another notch closest to the notch were splitting the same reinforcing fiber. 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 5 mm. The angle θ formed by the orientation direction of the reinforcing fibers and the notch was 40 °.

The surface of the press-molded product had a large notch. The tensile elastic modulus and tensile strength were higher than those of Comparative Example 1, but were lower than those of Examples 3, 4, and 6 having the same reinforcing fiber length.

(Comparative Example 3)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 9 (c). It is possible that the notch and another notch closest to the notch are splitting the same reinforcing fiber. 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 5 mm. The absolute value of the angle θ formed by the orientation direction of the reinforcing fibers and the cut is 40 °, and includes approximately the same number of positive cuts in which θ is positive and negative cuts in which θ is negative.

On the surface of the press-molded product, an opening of a notch was observed, but it was smaller than that of Comparative Example 2. The tensile strength was slightly improved as compared with Comparative Example 2.

(Comparative Example 4)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 9 (d). A continuous notch was inserted, the length of the divided reinforcing fiber was 20 mm, and the angle θ between the notch and the orientation direction of the reinforcing fiber was 20 °.

The surface of the press-molded product had a large notch. The tensile strength was higher than that of Comparative Example 3.

(Comparative Example 5)
The cut pattern of the cut prepreg was set as the cut pattern as shown in FIG. 9 (e). The cuts have substantially the same length Y = 1 mm, the length of the divided reinforcing fibers is 24 mm, and the projected length Ws obtained by projecting the cuts onto a plane perpendicular to the orientation direction of the reinforcing fibers is 0.34 mm. Met. The absolute value of the angle θ formed by the orientation direction of the reinforcing fibers and the notch was 20 °. When the position of the small region was changed, there was a pattern in which the coefficient of variation exceeded 80%.

Although the fiber length divided by the cut and the absolute value of θ are the same, as compared with Example 7, the surface of the press-molded product had a large cut and the tensile strength was low. ..

1: Prepreg 2: Notch 3: Area with multiple cuts that divide the reinforcing fiber (cut area)
4: Circular small area with a diameter of 10 mm 5: Reinforcing fiber between cut A and cut B 6: Distance between the most adjacent cuts 7: Positive cut 8: Negative cut 9: Straight line on which the positive cut rides 10: Straight line on which negative cuts ride 11: Distance between positive cuts adjacent to the same straight line 12: Distance between negative cuts adjacent to the same straight line

Claims (9)

A cut prepreg having a plurality of cuts that divide the reinforcing fibers in at least a part of a region of the prepreg containing unidirectionally oriented reinforcing fibers and a resin.
When the number of cuts contained in 10 circular small regions having a diameter of 10 mm, which are arbitrarily selected from the above regions, is used as the population, the average value of the population is 10 or more and the coefficient of variation is 20. Incision prepreg within%. The cut prepreg according to claim 1, wherein the arbitrary cut and another cut that is in close contact with the cut do not divide the same reinforcing fiber. The cut prepreg according to claim 1 or 2, wherein the cuts have substantially the same length Y, and the distance between the closest cuts is greater than 0.5 times Y. The cut prepreg according to any one of claims 1 to 3, wherein the cut is inserted at an angle with respect to the orientation direction of the reinforcing fibers. The absolute value of the angle θ formed by the cut and the orientation direction of the reinforcing fibers is substantially the same, and a cut in which θ is positive (called a positive cut) and a cut in which θ is negative (negative cut). ), The incision prepreg according to any one of claims 1 to 4. The cut prepreg according to claim 5, which includes approximately the same number of positive cuts and negative cuts. Claim 5 or 6 regarding the distance between an arbitrary cut and another cut that is in close contact on the extension line of the cut, the length differs between the distance between the positive cuts and the distance between the negative cuts. The notch prepreg described in. A method for producing a cut prepreg having a plurality of cuts for dividing a reinforcing fiber in at least a part of a region of the prepreg containing the reinforcing fiber and a resin.
A method for manufacturing a cut prepreg, which comprises a step 1 of inserting a plurality of cuts 1 into a prepreg and a step 2 of inserting a plurality of cuts 2 which do not overlap with the cut 1 into the prepreg. The cut prepreg according to claim 8, wherein the angle θ1 formed by the notch 1 and the reinforcing fiber is positive or negative, and the angle θ2 formed by the cut 2 and the reinforcing fiber is different from the angle θ1 formed by the notch 2. Manufacturing method.

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