JP4599718B2 - Multiaxial stitch fabric for reinforcement and method for forming FRP - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multiaxial stitched fabric used as a reinforcing fiber base material for FRP, a method for forming FRP using the multiaxial stitched fabric, and an automobile outer plate.
[0002]
[Prior art]
The fiber reinforced plastic composed of continuous reinforcing fibers is excellent in the mechanical properties in the fiber axis direction, but as the distance from the fiber axis increases, the mechanical properties in that direction decrease rapidly.
As a countermeasure, for example, the fiber axis direction is the length (0 °) direction, the width (90 °) direction, or the oblique (± α °) direction of the FRP molded body so that the mechanical characteristics become a pseudo-isotropic substrate. Are laminated and molded.
[0003]
However, when a normal woven fabric is used, the fiber arrangement directions are the length (0 °) direction and the width (90 °) direction of the woven fabric, so that reinforcement in an oblique (± α °) direction cannot be performed. As a countermeasure, the fabric is cut in an oblique direction, and the ends of the cut fabric are laminated so as to be parallel to the fabric arranged in the 0 ° direction and the 90 ° direction, and the arrangement direction of the fibers cut in the oblique direction is ± 45 °. However, this method takes time and effort to cut and laminate the fabrics, and the (0 ° / 90 °) aligned fabric and the (+ 45 ° / −45 °) aligned fabric are misaligned during the stacking, and the fiber orientation is accurate. It becomes difficult.
[0004]
On the other hand, recently, with a weft insertion tricot device, the above-mentioned problems have been achieved in the + α °, −α ° and 0 ° and / or 90 ° directions with respect to the length direction of the fabric, ie, more than two directions. A so-called multiaxial stitched fabric in which reinforcing fibers are arranged in parallel in a layered manner in each direction of the shaft and these are laminated and stitched together with stitches such as polyester fiber yarns has attracted attention. In this fabric, + α °, -α °, 0 °, and 90 ° aligned fibers are integrated with stitch yarns, so that it is not necessary to perform preparation work for arranging in a predetermined direction by cutting. Therefore, there is an advantage that a laminating operation is greatly saved and an inexpensive FRP molded body can be obtained. Further, by optimizing the stitch density of the stitch yarn, deep drawing can be performed, and there is an advantage that a preform for molding can be easily produced.
[0005]
However, since the stitch fabric has a fabric structure in which the reinforcing fibers are constrained by the stitch yarn, there are portions where the reinforcing fibers are constrained and no reinforcing fibers exist in each layer. Therefore, when the resin is impregnated and the resin is cured, the resin is cured and contracted. Therefore, in the FRP state, the amount of contraction in the thickness direction of the restraining portion of the reinforcing fiber is small because the reinforcing fiber exists, and there is no reinforcing fiber at all. The shrinkage amount of the portion was increased, the unevenness of the surface of the FRP was increased, and an FRP having a smooth surface was not obtained.
[0006]
In particular, since the surface smoothness required for the outer panel of automobiles is required to be a severe grade of Class A, if the FRP surface is sanded and painted or the gel coat layer is not thick enough on the surface of FRP, Did not reach.
[0007]
[Problems to be solved by the invention]
In view of the background of such prior art, the present invention is intended to provide a multi-axis stitched fabric, a molding method thereof, and an outer panel of an automobile, which can obtain a smooth surface and inexpensive FRP.
[0008]
[Means for Solving the Problems]
The present invention employs the following means in order to solve such problems. That is, the multi-axis stitched fabric of the present invention is
(1) A large number of reinforcing fiber yarns are arranged in a sheet form in parallel to form a layer structure, and at least two layers of the layers are cross-laminated to form a laminated body, and the laminated body has a melting point of 80 to A multiaxial stitched fabric for reinforcement characterized by being stitched and integrated with a low melting point polymer yarn at 200 ° C.
[0009]
(2) The crossing angle is + α °, two directions of −α °, two directions of 0 °, 90 °, three directions of 0 °, + α °, and −α °, + α °, -.alpha. °, 90 ° 3 direction and 0 °, + alpha DEG-.alpha. °, reinforcing multiaxial stitch fabric according to SL before Ru der either 90 ° in four directions (1).
[0014]
(3) the angle α゜Ga 45 reinforcing multiaxial stitch fabric according to゜Dea Ru before SL (2).
[0015]
(4) the reinforcing multiaxial stitch fabric according to any one of the low-melting polymer yarns copolymerized nylon yarn der Ru before SL (1) to (3).
[0016]
(5) the reinforcing multiaxial stitch fabric according to any one of the low-melting polymer yarns modified polyester yarn der Ru before SL (1) to (3).
[0018]
(6) A method for molding FRP, wherein the reinforcing multiaxial stitch fabric according to any one of (1) to (5) is impregnated with a resin and heat-molded to a temperature higher than the melting point of the low-melting polymer yarn.
[0019]
(7) The automatic vehicle exterior plate Do that using FRP obtained by the molding method described in (6) [0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail based on embodiments shown in the drawings.
[0021]
FIG. 1 is a partially cutaway schematic perspective view showing an embodiment of a multi-axis stitched fabric according to the present invention. As shown in FIG. 1, from the lower surface of the fabric 1, first, a first layer has a number of reinforcing fiber yarns 2 arranged in parallel in an oblique direction with respect to the length direction A to form a + α ° layer 6. Next, the second layer has a plurality of reinforcing fiber yarns 3 arranged in parallel in the width direction of the fabric to form a 90 ° layer 7, and then the third layer has a plurality of reinforcing fiber yarns 4 in parallel in the oblique direction. -Α ° layer 8 is arranged to form a fourth layer, and a plurality of reinforcing fiber yarns 5 are arranged in parallel in the length direction of the fabric to form 0 ° layer 9, and the arrangement direction is mutually In a state where different first to fourth layers are laminated, these four layers are stitched and integrated with the stitch yarn 10.
Examples of the stitch structure formed by the stitch thread upon the stitching integration include single ring stitching and 1/1 tricot knitting.
[0022]
FIG. 2 is an enlarged schematic view of the AA ′ cross section of the multi-axis stitched fabric shown in FIG. 1. As shown in FIG. 2, a tricot knitting structure in which stitch yarns 10 are formed in four layers of a -α ° layer 6, a 90 ° layer 7, a + α ° layer 8, and a 0 ° layer 9 is integrated. The yarns of each layer are arranged in parallel in the layers, and the needles are randomly inserted into these yarns, and the stitch yarn forms a stitched structure. At this time, the reinforcing fiber 11 does not exist between the stitch yarn 10 and the stitch yarn 10 due to the tension of the stitch yarn, and a large gap B is formed.
[0023]
FIG. 3 shows a schematic cross-sectional view of an FRP molded body using the conventional multiaxial stitch fabric shown in FIG. 2, but there is no reinforcing fiber in the space B between the stitch yarn 10 and the stitch yarn 10. When the resin impregnated in the multiaxial stitch fabric is cured, the volume shrinks, and the surface of the portion is recessed. In addition, since the stitch yarn 10 has a portion located outside the reinforcing fiber layer, the stitch yarn 10 portion is more convex than the portion where the stitch yarn 10 does not exist even when the mold is filled with the fabric. Thus, the FRP surface is uneven, and the surface smoothness does not reach Class A very much.
[0024]
The fabric structure of the multiaxial stitched fabric of the present invention is not different from the conventional multiaxial stitched fabric, but the present invention is characterized in that a low melting polymer yarn is used as the stitched yarn.
[0025]
The low-melting-point polymer yarn used in the present invention is a melt-spun polymer having a melting point of 80 to 200 ° C., melted at the time of molding, and the stitch yarn structure formed by the stitch yarn after molding disappears. What will be in a state is preferable. When the melting point is less than 80 ° C., when it is molded into fiber reinforced plastic (hereinafter referred to as FRP), the area where the low melting point polymer is present is melted due to the temperature rise due to outdoor exposure, etc., although the area and volume are small. Since it will be in a state, it is not preferable. On the other hand, if the melting point exceeds 200 ° C., it takes time to raise the temperature of the mold and cool the mold for curing the matrix resin during molding, which is not preferable. More preferably, the melting point of the low-melting polymer yarn is 120 to 160 ° C.
[0026]
The low melting point polymer used in the present invention is usually selected from nylon, copolymer nylon, polyester, modified polyester, vinylidene chloride, vinyl chloride, polyurethane, polypropylene, polyurethane and the like. Among these, copolymer nylon is preferable because it can melt the polymer at a low temperature and has good adhesion to the matrix resin of FRP.
[0027]
Further, a modified polyester that can melt the polymer at a low temperature, has good adhesion to the matrix resin, and has a low water absorption rate is preferable.
[0028]
If the thickness of the stitch yarn is thin, the yarn will break during stitching operation, and if it is thick, the low melting point polymer part formed by melting the stitch yarn will become large when it is made FRP, resulting in color spots etc. during painting Therefore, 50 to 400 dtex is preferable. More preferably, it is 70-300 dtex.
[0029]
Examples of the reinforcing fibers used in the present invention include glass fibers, polyaramid fibers, and carbon fibers. Among them, carbon fibers have good adhesiveness with a matrix resin, and have high tensile strength and tensile elastic modulus. Since weight reduction is achieved, it is preferably used.
[0030]
The thickness of the reinforcing fiber used in the present invention is preferably about 3,000 to 50,000 dtex. In particular, it is preferable to use a thick reinforcing fiber yarn because the reinforcing fiber becomes cheap and an inexpensive fabric can be obtained. However, if the basis weight of the reinforcing fiber per layer is small, a gap is formed between the yarns in the layer, and when the stitches are integrated with each other, the fiber density becomes partially non-uniform, and when molded, the fiber density is high. However, the FRP becomes thick and the FRP becomes thin where the fiber density is small, resulting in an FRP having an uneven surface. Furthermore, when using thick reinforcing fiber yarns of 7,000 to 50,000 decitex, if the reinforcing fiber yarns are spread thinly by roller swinging operation or air jet injection before integrated processing with stitch yarns, This is preferable because the density of the reinforcing fibers becomes uniform over the entire surface and an FRP having a smooth surface can be obtained.
[0031]
Originally, the role of the stitch yarn is to prevent the fiber orientation from being disturbed in the state of the fabric, and to prevent the multiple reinforcing fiber yarns arranged in parallel from being frayed. However, the reinforcing effect in the layer direction is not so great.
[0032]
The configuration of the reinforcing fiber of the fabric shown in FIG. 1 has been described as a four-layer configuration of + α ° layer / 90 ° layer / −α ° layer / 0 ° layer, but is not limited to this, and at least the fabric The layer structure may be formed in the direction of the bias (± α °) of the −α ° layer and the + α ° layer with respect to the length direction. Further, the order of the layer structure is not limited to the order of -α ° / 90 ° / + α ° / 0 °, but is 0 ° / -α ° / 90 ° / + α ° or 0 ° / -α ° / + α °. / 90 ° can be designed as appropriate. In addition, when a fabric in which reinforcing fibers are arranged only in the bias direction of the -α ° layer and the + α ° layer is used, the direction of the reinforcing fibers is easily shifted when pulled in the length direction of the fabric, and the width direction of the fabric is narrowed. The form is unstable. In such a case, for example, auxiliary fibers such as glass fibers, carbon fibers and polyaramid fibers that are thin in the 0 ° direction or 90 ° direction are arranged at about ²⁰ to 100 g / m ² , and the −α ° layer, + α ° layer and stitch yarn are arranged. If integrated with, the form can be stabilized.
[0033]
The bias angle α ° is preferably 45 ° from the viewpoint of effectively laminating multiaxial stitched fabric in the length direction of the FRP molded body and effectively performing shear reinforcement with reinforcing fibers.
[0034]
The FRP using the multiaxial stitched fabric of the present invention can be formed, for example, as follows.
[0035]
A predetermined number of multiaxial stitched fabrics of the present invention are laminated in a predetermined direction on a female RTM molding die, a male die is placed thereon, and the periphery of the die is sealed with a putty. Next, the inside of the mold is sucked with a vacuum pump so as to be in a vacuum state, and then the resin is injected. Next, the mold is sufficiently heated to be equal to or higher than the melting point of the low-melting polymer yarn to cure the injected resin. Cool the mold and remove it.
[0036]
The molding method of the present invention is not limited to the above RTM molding method. For example, a multiaxial stitched fabric is heated and impregnated at a temperature lower than the melting point of the low-melting polymer yarn in the dry method, or the melting point in the wet method. A method of forming a prepreg by heating and drying at the following temperature, laminating the prepreg on a mold, and heating and pressing at a temperature higher than the melting point of the low-melting polymer yarn may be used.
[0037]
The resin used in the present invention may be a thermosetting resin such as epoxy resin, unsaturated polyester resin, vinyl ester resin or phenol resin, or a thermoplastic resin such as nylon resin, PBT resin, polyethylene resin or polypropylene resin.
[0038]
FIG. 4 shows a schematic cross-sectional view of the FRP molded body obtained by the molding method of the present invention. Since the multiaxial stitched fabric is heated to the melting point of the low-melting polymer yarn simultaneously with the heating of the mold, the low-melting polymer The yarn is melted, and the low melting point polymer 12 is scattered at the locations where the polymer yarn was present in the FRP. In addition, the stitch structure formed by the stitch yarn made of the low melting point polymer disappears when the stitch yarn melts, so that the reinforcing fiber is unconstrained by the stitch yarn and the reinforcing fiber is dispersed in the space B. The surface of the obtained FRP becomes smooth.
[0039]
FIG. 5 is a schematic diagram for explaining an automobile outer plate. The reinforcing multi-axis stitch fabric of the present invention is applied to outer plates such as a hood 13, a fender 14, a door 15, a roof 16, a trunk cover 17, and the like. When an FRP molded body obtained by using, impregnating a resin, and heat-molding to a temperature higher than the melting point of the low-melting polymer yarn is used, the surface becomes smooth, excellent in design, and inexpensive.
[0040]
【The invention's effect】
Since the reinforcing multiaxial stitch fabric of the present invention is stitch-integrated with a low-melting polymer yarn, an FRP molded product with a smooth surface can be obtained by impregnating the resin and heat-molding it above the melting point of the low-melting polymer yarn. It is done.
[Brief description of the drawings]
FIG. 1 is a partially cutaway schematic perspective view showing an example of a multi-axis stitched fabric of the present invention.
FIG. 2 is an enlarged schematic view of the AA ′ cross section of FIG. 1;
FIG. 3 is a schematic cross-sectional view of an FRP molded body of a conventional multi-axis stitched fabric.
FIG. 4 is a schematic cross-sectional view showing an example of an FRP molded body of the multi-axis stitched fabric of the present invention.
FIG. 5 is a schematic view illustrating an automobile outer plate.
[Explanation of symbols]
1: Multiaxial stitched fabric 2: + α ° layer reinforcing fiber yarn 3: 90 ° layer reinforcing fiber yarn 4: -α ° layer reinforcing fiber yarn 5: 0 ° layer reinforcing fiber yarn 6: Fabric + Α ° reinforcing fiber layer 7 forming the fabric: 90 ° reinforcing fiber layer forming the fabric 8: forming the fabric -α ° reinforcing fiber layer 9: 0 ° reinforcing fiber layer forming the fabric 10: stitch yarn 11: Reinforcing fiber 12: Low melting point polymer 13: Automotive hood 14: Automotive fender
15: Automobile door 16: Automobile roof 17: Automobile trunk cover: Longitudinal direction AA 'of the fabric: Reference line B of the cross section: Air gap

Claims (7)

A large number of reinforcing fiber yarns are arranged in a sheet form in parallel to form a layer structure, and at least two layers of the layers are cross-laminated to form a laminated body, and the laminated body has a melting point of 80 to 200 ° C. A multiaxial stitched fabric for reinforcement characterized by being stitched and integrated with a low melting point polymer yarn. The crossing angles are + α °, -α ° in two directions, 0 °, 90 ° in two directions, 0 °, + α °, -α ° in three directions, + α °, -α ° with respect to the length direction of the fabric. , 90 ° 3 direction and 0 °, + alpha DEG,-.alpha. °, is either 90 ° in four directions, reinforcing multiaxial stitch fabric according to claim 1. It said angle α゜Ga is 45 °, the reinforcing multiaxial stitch fabric according to claim 2. The multiaxial stitch fabric for reinforcement according to any one of claims 1 to 3 , wherein the low-melting-point polymer yarn is a copolymerized nylon yarn. The multiaxial stitch fabric for reinforcement according to any one of claims 1 to 3 , wherein the low melting point polymer yarn is a modified polyester yarn. A method for molding FRP, comprising impregnating a resin in the reinforcing multiaxial stitch fabric according to any one of claims 1 to 5, and heat-molding the resin to a temperature equal to or higher than a melting point of the low-melting polymer yarn. An automobile outer plate using FRP obtained by the molding method according to claim 6.

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