JP2019044285A - Heat-resistant multiaxial stitch base material - Google Patents

Abstract

To provide a heat-resistant multiaxial stitch base material which does not cause the heat-shrinking or heat-melting of a stitch yarn even when exposed to a high-temperature environment in a preform production process and a molding process, or in an FRP product, and which prevents the fraying of the stitch yarn occurring during cutting and lamination, thereby being able to keep its form.SOLUTION: In a multiaxial stitch base material, a plurality of reinforcing fiber sheets comprising reinforcing fiber yarns arranged parallel to each other are laminated, each in a different orientation direction, and are integrated by sewing with a stitch yarn passing through the sheets. The stitch yarn has a fineness of 100-500 dtex and is a composite yarn which comprises a glass fiber yarn having a breaking strain energy of 30 MJ/mor more and a thermoplastic polymer yarn having a fineness of 30-120 dtex. When heated, the thermoplastic polymer yarn forming the stitch yarn is fusion-bonded to and integrated with the glass fiber yarn and the reinforcing fiber yarns.SELECTED DRAWING: Figure 1

Description

  The present invention relates to the improvement of a multiaxial stitch substrate used as a fiber-reinforced substrate of fiber reinforced plastics (FRP), more specifically, a high temperature environment in a preform manufacturing process, a molding process, or an FRP product. Even if exposed to the following conditions, the stitch yarn does not cause heat shrinkage or heat melting, and the handling of the multiaxial stitch base material can be maintained by preventing fraying of the stitch yarn that occurs during cutting or lamination. The present invention relates to a heat resistant multiaxial stitch base material.

  Fiber-reinforced plastics (FRP: Fiber-Reinforced-Plastics) with carbon fiber or glass fiber as a reinforcing material exhibits high strength and elastic modulus in the fiber direction, but it is sharp with respect to the angle orthogonal to the fiber direction So that the mechanical properties are quasi-isotropic, such as 0 ° / 90 °, 0 ° / ± 45 °, or 0 ° / + 45 ° / -45 ° / 90 ° There is used a method of laminating and molding so that fiber axes become multiaxial.

  However, since it takes time and effort to laminate while accurately aligning the fiber axes at the time of molding, and the production efficiency becomes very low, as proposed in <Patent Document 1>, a plurality of fibers are formed in advance at a predetermined fiber orientation angle. There is known a multiaxially stitched base material in which sheets of sheets are laminated and these sheets are penetrated with a stitch thread to form a stitch.

  In such an integration technology of multiaxial stitch substrates, a stitch yarn is fed to a needle that penetrates the substrate, and stitches are sequentially drawn while being drawn in the substrate thickness direction to integrate the laminate. Therefore, synthetic yarns such as polyamide fibers and polyester fibers having high toughness are usually used as the stitch yarns.

  However, for preparing a preform, there is a case where the base material is exposed to a high temperature in the process of applying an adhesive and adhering it at a high temperature, or in the prepreg process or the forming process. However, there has been a problem that heat shrinkage occurs to generate wrinkles, or heat melting causes loss of the integrated function of the laminate.

  In addition to the above-described prepreg process and molding process, when the resin is made of FRP with high heat resistance and then exposed to high temperatures, melting or decomposition of the stitch yarn occurs in the region below the heat resistance temperature of the FRP, and the inside of the FRP There is also a problem in that the mechanical properties are lowered due to the void where the stitch yarn is present.

  Furthermore, synthetic fiber yarns have water absorbability, and in particular, when FRP is molded from a reinforced fiber base material using fibers having large water absorbability as stitch yarns, the curing of the resin becomes insufficient due to moisture, or the inside of a molded article The "microcracks" occur due to repeated melting of water, which causes problems that the material can not be a reliable material, and is particularly unsuitable for use in aircraft.

  So, in <patent document 2>, even if it is exposed to high temperature, by using a stitch yarn as a twist yarn of glass fiber, heat contraction occurs like a synthetic fiber yarn to generate wrinkles or heat melting. If the FRP is molded from a reinforced fiber base material that uses fibers with large water absorbability for stitch yarns, curing of the resin may become insufficient due to moisture, or molding may be prevented. It is proposed to prevent the occurrence of "microcracks" due to repeated freezing of water in the product.

  However, although the problem of heat resistance and water absorption could be solved in the proposal of <patent document 2>, it is higher in elasticity than synthetic fiber yarn because it uses a twist yarn of glass fiber as a stitch yarn. Therefore, a force acts to straighten the needle loop formed by the stitch yarn, so that the yarn itself has high rigidity and is hardly crushed. Therefore, the contact with the reinforcing fiber and the contact of the stitch yarn itself in the needle loop become smaller at the point contact and the friction becomes smaller, so the stitch base is broken off from the cut surface and integrated by the stitch There was a problem that the function was lost.

International Publication No. 01/63033 JP, 2016-164320, A

  The present invention has been made in view of the problems as described above in the conventional multiaxial stitch base material for FRP molding, and the purpose of the present invention is a preform production process and a molding process Or, even if exposed to high temperature environment in FRP products, the stitch yarn does not cause heat shrinkage or heat melting, and the fray of the stitch yarn that occurs during cutting or lamination is prevented to prevent the multiaxial stitch substrate It relates to an easy-to-handle heat-resistant multiaxial stitch substrate that can be maintained in form.

  The means employed by the inventor for solving the above-mentioned technical problems will be described below with reference to the accompanying drawings.

That is, according to the present invention, a plurality of reinforcing fiber sheets in which reinforcing fiber yarns are arranged in parallel to one another are laminated in different orientation directions, respectively, and a multiaxially integrated by stitching yarns penetrating these sheets. Stitch base material,
The stitch yarn is a composite yarn consisting of a glass fiber yarn having a breaking strain energy of 30 MJ / m ³ or more and a thermoplastic polymer yarn having a denier of 30 to 120 dtex while having a fineness of 100 to 500 dtex,
A heat-resistant multiaxial stitch substrate is obtained by adopting a technical means of fusing and integrating thermoplastic polymer yarns constituting stitch yarns with glass fiber yarns and reinforcing fiber yarns by heating. It was completed.

  Further, in order to solve the above-mentioned problems, the present invention, in addition to the above-mentioned means as needed, makes the stitching yarn a covering yarn having a glass fiber yarn as a core yarn and a thermoplastic polymer yarn as a sheath yarn. It is also possible to adopt the technical means of

  Furthermore, in order to solve the above problems, the present invention optionally, in addition to the above means, a yarn made of a low melting point polymer, or a core-sheath composite yarn in which the low melting point polymer is sheathed. It is also possible to adopt the technical means of

  Furthermore, in order to solve the above-mentioned problems, the present invention optionally comprises, in addition to the above-mentioned means, two thermoplastic polymer yarns of a sheath yarn constituting a stitch yarn and a glass fiber yarn of a core yarn. It is also possible to employ technical means of double covering yarns wound doubly in the S and Z directions.

  Furthermore, in order to solve the above problems, the present invention optionally, in addition to the above means, the thermoplastic polymer yarn of the sheath yarn constituting the stitch yarn, 2 to 10 times per 1 cm of glass fiber yarn of the core yarn. It is also possible to employ the technical means of making a covering yarn processed with a number of turns.

  Furthermore, in order to solve the above-mentioned problems, the present invention, in addition to the above-mentioned means as required, is a technical means of setting the radius of curvature of the needle loop formed by the stitch yarn in the range of 0.3-2 mm. It can also be adopted.

  Furthermore, in order to solve the above problems, the present invention can adopt technical means of setting the course density of the stitch by the stitch yarn to 2 to 4 courses / cm as needed, in addition to the above means. .

  Furthermore, in order to solve the above-mentioned problems, the present invention, in addition to the above-mentioned means, is selected from carbon fiber, glass fiber, aramid fiber, silica fiber and ceramic fiber, as needed. It is also possible to employ technical means to make single fibers or mixed fibers.

In the present invention, a plurality of reinforcing fiber sheets, in which reinforcing fiber yarns are arranged in parallel to one another, are laminated in different orientation directions, and a plurality of sheets are integrated by stitching through these sheets. In the axial stitch substrate,
The stitch yarn has a fineness of 100 to 500 dtex, and is a composite yarn composed of a glass fiber yarn having a breaking strain energy of 30 MJ / m ³ or more and a thermoplastic polymer yarn having a fineness of 30 to 120 dtex. The plastic polymer is fused and integrated to the glass fiber yarn and the reinforcing fiber yarn, and further integrated by the stitch yarn mainly made of the glass fiber excellent in heat resistance and flame resistance,
Even if exposed to high temperature environment in preform manufacturing process or molding process, or FRP product, stitch yarn does not cause heat shrinkage or heat melting, has dimensional stability, and does not fray stitch yarn at the time of cutting It can be reliably prevented.

That is, by setting the fineness of the stitch yarn to 100 to 500 dtex, and setting the breaking strain energy of the glass fiber yarn to 30 MJ / m ³ or more, processing can be performed without stitch breakage or fuzzing in the stitching process, Surface irregularities can also be minimized.

In addition, an interlayer reinforcing effect can be exhibited by causing a stitch yarn made of a glass fiber yarn having a breaking strain energy of 30 MJ / m ³ or more to penetrate in the thickness direction of the stitch base material.

  Furthermore, as needed, by making the stitching yarn a covering yarn having a glass fiber yarn as a core yarn and a thermoplastic polymer yarn as a sheath yarn, it is easy to handle in a preparatory work for stitching, etc. to improve productivity. Can.

  In addition, since the stitch yarn inside the FRP is not decomposed in a high temperature atmosphere and the thermoplastic polymer used is also a small amount, the occurrence of voids is extremely small, and high mechanical properties are obtained if it is below the heat resistance temperature of the resin. It can be demonstrated.

  Furthermore, if necessary, by using a thermoplastic polymer yarn as a sheath yarn of a stitch yarn as a low melting point polymer, it is possible to fuse the thermoplastic polymer at a low temperature, so heat treatment processing becomes easy and simultaneously reinforced It is possible to reduce the thermal influence on the sizing agent and the coupling agent when adhering to the fiber.

  Furthermore, if necessary, the needle loop formed by the stitch yarn has a radius of curvature in the range of 0.3 to 2 mm to allow extra thread length for the needle loop, thereby forming the needle loop or While forming, it is possible to prevent the breakage of the stitch yarn due to the bending of the loop tip caused when the loop is elongated with the longitudinal extension of the substrate, and the reinforcing force against the substrate is not too strong, and the reinforcing fiber The industrial utility value is extremely large because the straightness of the above can be maintained, and in the case of a bias alignment substrate such as ± 45 °, the formability can be improved.

FIG. 1 is a schematic diagram representing the structure of a multiaxial stitch substrate of an embodiment of the present invention. It is the schematic showing the structure of the stitching thread of the embodiment of the present invention. It is an enlarged view showing the shape of the needle loop of the stitch thread of the embodiment of the present invention.

  The mode for carrying out the present invention will be described in more detail based on the drawings specifically illustrated as follows.

  An embodiment of the present invention will be described based on FIGS. 1 to 3. In FIG. 1, what is designated by reference numeral 1 is a multiaxial stitch base material, and what is designated by reference numeral 2 is a stitch yarn.

  Moreover, what is indicated by reference numeral 3 (3a, 3b, 3c, 3d) is a reinforcing fiber sheet, and each of the reinforcing fiber sheets 3 is formed in a sheet shape by arranging reinforcing fiber threads in parallel to each other .

  In constructing the multiaxial stitch base material 1 of the present embodiment, first, the reinforcing fibers of each reinforcing fiber sheet 3 are laminated so that the orientation directions of the reinforcing fibers are different. For example, when the longitudinal direction of the multiaxial stitch substrate 1 is 0 °, the sheet 3a is laminated at -45 °, the sheet 3b at 90 °, the sheet 3c at + 45 °, and the sheet 3d at 90 °. Then, the stitch thread 2 is penetrated through these sheets to integrate them with stitching (see FIG. 1).

  At this time, the laminated structure of the reinforcing fiber sheet 3 is not limited to the above laminated structure, and at least two layers having different orientation angles of the reinforcing fibers may be laminated, for example, 0 ° / 90 °, Biaxial orientation at 0 ° / + 45 °, 4-axis orientation at 0 ° / + 45 ° / −45 ° / 90 °, or lamination at 0 ° / ± 45 ° or 60 ° cross angle It is good.

Moreover, in this embodiment, as a fabric weight of the sheet | seat per one layer of the reinforcement fiber sheet 3, the thing of 50-400 g / m < ² > is employ | adopted. If the weight per unit area is less than 50 g / m ^2, it becomes difficult to spread the reinforcing fibers uniformly because it becomes a very thin sheet, and there is a problem that voids occur, while if the weight per unit area is more than 400 g / m ² Since the fibers are dense and form thick layers, there is a problem that resin impregnation becomes difficult. In addition, more preferable fabric weight is the range of 70-300 g / m < ² >.

  The knitting structure of the stitch yarn 2 may be a normal warp knitting structure such as chain knitting, 1/1 tricot knitting, or change structure of chain knitting and 1/1 tricot knitting.

  In the present embodiment, when reinforcing fibers are used as the stitch yarns 2, those conventionally used generally, such as carbon fibers and glass fibers, can be considered, but many fibers having heat resistance and flame resistance are used together. It is extremely brittle, and there are problems with stitch processability, quality of processed products, and performance, so that it is not suitable for use as a stitch yarn as it is.

  In addition, when carbon fiber or glass fiber is used, since it has high elasticity, a force acts to straighten the needle loop formed by the stitch yarn, so the rigidity is high and the yarn itself is hardly crushed. Therefore, the contact with the reinforcing fiber and the contact of the stitch yarn itself in the needle loop are small points of friction because they come in contact with each other, so the stitch base is broken and the integrated function by the stitch is broken. Was lost, and the handleability of the stitch base material was very bad.

So, in this embodiment, the breaking strain energy at a denier of 100 to 500 dtex is 30 MJ / m ³ (M (Mega) = 10 ⁶ , J / m ³ = N · m / m ³ = N / m ² ). The glass fiber yarn 5 described above and a yarn 6 of 30 to 120 dtex made of a thermoplastic polymer were employed. The breaking strain energy W is a value derived by the following equation.
W = σ × ε / 2
σ: tensile strength (Pa = N / m ² ), ε: tensile breaking strain

  By doing this, it is possible to complete a multiaxial stitch base material that satisfies desired heat resistance and flame resistance and has no problems with stitch processability and quality and performance of a processed product.

  That is, among various kinds of fiber types having heat resistance and flame retardancy, glass fibers have an adverse effect on the appearance of a molded product because fine fibers are inexpensive and available and the fibers themselves are transparent. It is optimal in that it does not

  The stitch yarn may be a aligned yarn of glass fiber yarn 5 and thermoplastic polymer yarn 6 or a twist yarn, but as shown in FIG. 2, glass fiber yarn 5 is used as a core yarn, and thermoplastic polymer yarn 6 It is also possible to adopt a covering thread with a covering. And, as a covering process, it may be a single covering yarn in which the glass fiber yarn 5 is covered in the S direction or the Z direction using one thermoplastic polymer yarn 6, but the direction of covering is made by the rigidity of the fiber. There is a problem that torque is generated in the opposite direction to that of the yarn and it is difficult to handle it in preparation for stitching etc. Specifically, two thermoplastic polymer yarns 6 are used to make the glass fiber yarns 5 in the S and Z directions Since the torques in the S direction and in the Z direction cancel each other out by forming a double covering yarn covered with the above, it is possible to configure the easy-to-handle stitch yarn 2.

  With regard to the application range of the fineness of the glass fiber yarn 5 in the present embodiment, when the thick fineness yarn is larger than 500 dtex, the thick stitch yarn 2 protrudes on the flat base material surface, and a molded article having a smooth surface can not be obtained. Therefore, it is preferable that the fineness is 500 dtex or less. On the other hand, with fine fineness yarn less than 100 dtex, the strength necessary for loop formation at the time of stitch processing is insufficient, and problems such as cutting or fuzzing during the stitching process Therefore, the fineness of the preferred glass fiber yarn 5 is in the range of 100 to 500 dtex.

And although glass fiber generally has high tensile breaking strength, it has a small tensile elongation at break and high compressive strength, so when the fiber is bent, the outer periphery (tension side) is bent without buckling on the inner circumference (compression side). The glass fiber of the present embodiment adopts one having a breaking strain energy W of 30 MJ / m ³ or more because it has the disadvantage of being easily broken and easily broken.

  Furthermore, a 30-120 dtex thermoplastic polymer yarn 6 is used as a sheath yarn, and a stitch yarn 2 obtained by covering the glass fiber yarn 5 is adopted, and thermal treatment is performed by heating in any step after the stitching. Since the plastic polymer yarn 6 is fused and integrated with the glass fiber yarn 5 which is the core yarn of the stitch yarn 2 and the reinforcing fiber yarn, it can be used in a high temperature environment in a preform manufacturing process, a molding process or an FRP product. Even if exposed, the stitch yarn 2 does not cause heat shrinkage or heat melting, thereby suppressing the occurrence of wrinkles and having dimensional stability, and further suppressing the occurrence of voids, and preventing fraying of the stitch yarn 2 at the time of cutting Demonstrate high form retention.

  The application range of the denier of the thermoplastic polymer yarn 6 to cover the glass fiber yarn 5 is larger than 120 dtex, the amount of the thermoplastic polymer is large, the water absorption is high compared to the glass fiber, FRP from the reinforcing fiber base When molded, the resin may not cure sufficiently due to moisture, or the moisture in the molded product may repeatedly freeze and cause "microcracks", resulting in a problem that the material can not be made reliable. Since the yarn 2 itself is thick as a whole, there is a problem that the surface of the FRP is uneven when it is molded, and surface smoothness can not be obtained. On the other hand, when it is smaller than 30 dtex, sufficient adhesiveness can not be obtained when heat-fusing, and the fraying preventing effect of the stitch yarn 2 can not be obtained. Therefore, the preferable denier of the thermoplastic polymer yarn 6 to be covered with the glass fiber yarn 5 is 30 to 120 dtex, more preferably 30 to 60 dtex.

  In addition, as the polymer of the thermoplastic polymer yarn 6, usually, those selected from nylon, copolymer nylon, polyester, modified polyester, vinylidene chloride, vinyl chloride, polyurethane, polypropylene, polyurethane, etc. can be adopted, among which at low temperature Copolymerized nylons that can melt the polymer and have good adhesion to the matrix resin of FRP are preferred. The melting point is preferably 180 ° C. or less. When the melting point is higher than 180 ° C., the thermal effect of reinforcing fibers such as carbon fibers and glass fibers on the sizing agent and coupling agent is large when heat fusion is performed, and they are deteriorated, and the strength when made into FRP There is a problem of reduced expression. The more preferable melting point is 150 ° C. or less.

  In the present embodiment, since the stitch yarn 2 is a yarn bundle subjected to covering processing, the yarn is focused to increase the bending rigidity, so that the curvature of the loop tip at the time of forming the loop can be suppressed from increasing. It is possible to prevent breakage of glass fiber at the time of formation.

  In addition, the twisting torque of the core yarn can be offset by applying a slight twist to the glass fiber yarn 5 forming the core yarn of the stitch yarn 2 and covering the thermoplastic polymer yarn 6 in the direction opposite to the twist direction. In addition, each single fiber is helically arranged in the yarn bundle so that each single fiber is not fixed to the pulling side or the compression side against bending of the stitch yarn 2, and the stress generated in each single fiber becomes substantially uniform. Therefore, it is possible to prevent breakage of the glass fiber at the time of loop formation.

  Furthermore, as a condition of covering processing, the thermoplastic polymer yarn of the sheath yarn constituting the stitch yarn is a covering yarn processed by covering with a number of winding less than twice per 1 cm of the glass fiber yarn 5 of the core yarn. Certainly, the focusing force with the glass fiber yarn 5 can not be obtained, and the glass fiber yarn 5 and the thermoplastic polymer yarn 6 are separated and difficult to handle in preparatory work of stitching, etc. There is a problem that it is difficult to hook. In addition, if the covering yarn is covered with a winding number of more than 10 turns per 1 cm of the glass fiber yarn 5 of the core yarn, the yarn rigidity is too high and the yarn path is on the line supplying the stitch yarn 2 There is a problem that the compatibility of the bent portion is bad and it is difficult to feed yarn, and it is difficult to form a loop in the stitch processing, and the cross section of the stitch yarn 2 becomes a completely circular and tightly converged state, and the surface of the molded product becomes uneven. There is a problem of Therefore, the winding number of the covering which is preferable as a condition for covering processing is 2 to 10 times per 1 cm of the glass fiber yarn 5 of the core yarn.

  The loop forming method of the stitch processing in the present embodiment supplies the stitch yarn 2 to the needle 4 penetrating the laminate of the reinforcing fiber sheet 3 and then the reinforcing fiber sheet 3 in a state where the stitch yarn 2 is hooked on the needle hook Stitching while repeating the process of passing through the stack of and pulling out the necessary yarn length for a new loop.

Accordingly, the stitch yarn 2 at the time of loop formation is bent at a large curvature at a high curvature due to the frictional resistance between the laminate of the reinforcing fiber sheet 3 and the needle hook, so the breaking strain energy W is 30 MJ / If the glass fiber is less than m ³ , yarn breakage or single yarn breakage tends to occur at the bending portion, and satisfactory stitch processability can not be obtained.

  In addition, sizing of glass fiber yarn 5 includes starch sizing and plastic sizing, but when using glass fiber yarn 5 of starch size, interface adhesion is poor and sufficient mechanical properties can not be obtained when FRP is used, It is preferred to employ plastic sized glass fibers.

  Next, the enlarged view of the loop part by the stitch yarn 2 of the multiaxial stitch base material 1 of this embodiment is shown in FIG. The symbol r indicates the radius of curvature of the central axis of the stitch yarn 2. The radius of curvature r can be arbitrarily controlled by the thickness and bending rigidity of the stitch yarn 2 and the stitch processing conditions, but in the present embodiment this radius of curvature r is It is preferable that it is the range of 0.3-2 mm.

  If the radius of curvature r of the loop is small, the tightness to the substrate by the stitch yarn 2 is strong, and in particular, in the case of the stitch yarn 2 having a high elastic modulus like glass fiber, the stitch yarn 2 is based on the substrate in the thickness direction. There is a problem of causing a bend in the reinforcing fiber yarn because the reinforcing fiber yarn is tightened in a circular arc shape without being a right angle at the corner portion toward the material surface direction or the opposite corner portion. Also, in a bias-oriented substrate such as ± 45 °, stress concentration is generated at the loop tip when the substrate is stretched in the longitudinal direction because there is no room for the loop to longitudinally extend, and the stitch yarn 2 is The curvature radius r is preferably 0.3 mm or more because there is a possibility of cutting.

  On the other hand, when the radius of curvature r of the loop is large, the above problems can be solved and the shapeability is also increased in a bias alignment substrate such as ± 45 °, but when the radius of curvature r is larger than 2 mm, the stitch processing is stitched The radius of curvature r of the loop should be 2 mm or less, since the amount of delivery of the yarn 2 becomes too large, and slack may occur between the stitch yarn supply beam and the knitting portion, resulting in a supply error to the needle. preferable.

  In addition, as a kind of reinforcement fiber which makes each reinforcement fiber sheet 3, it is a high strength and high elasticity modulus, Comprising: The fiber which had heat resistance and a flame retardance especially is preferable, for example, carbon fiber, glass fiber, aramid fiber And silica fiber, ceramic fiber, or any single or mixed fiber selected from such fibers. By such selection, the entire multiaxial stitch substrate 1 together with the stitch yarn 2 has heat resistance and flame retardancy. Therefore, it has dimensional stability without causing heat shrinkage during heat treatment during preform preparation or a prepreg process, or molding process, and can exhibit a flame retardant effect in a molded product.

  Moreover, in the present embodiment, it is preferable that the course density of the stitch is 2 to 4 courses / cm. If the course density is less than 2 courses / cm, it is necessary to pull out a large amount of stitch yarn 2 at one time to form a long loop, so it is easy to cause yarn breakage by applying high tension to stitch yarn 2 On the other hand, if the course density is more than 4 courses / cm, the amount of use of the stitch yarn 3 is increased and the productivity is lowered at the same time as the cost is increased.

  Next, the evaluation about the sample which produced specifically the multiaxial stitch base material of this invention and a comparative example is demonstrated below.

[Invention Item]
As a multiaxial stitch base material, carbon fiber yarns having a tensile strength of 4900 MPa, a tensile elastic modulus of 235 GPa, and a fineness of 800 tex (12000 filaments) are used as reinforcing fibers so that the fabric weight is 100 g / m ² The sheets arranged in parallel were stacked at ± 45 ° with respect to the direction in which the stitch yarn 2 was woven.

Then, as a stitch yarn, a glass fiber yarn (glass yarn) having a fineness of 112 dtex, a tensile strength of 3.2 GPa, a breaking elongation of 4.8% and a breaking strain energy of 76.8 MJ / m ³ is used as a core yarn Double covering of 5 turns / cm in S direction and Z direction respectively using 2 nylon fibers of 56 dtex as sheath yarn to obtain a covering yarn, and using the covering yarn, wale density is Stitching was performed by chain knitting of 5 W / inch (= 1.97 W / cm: 1 inch = 2.54 cm) and a course density of 8.5 C / inch (= 3.35 course / cm).

  Further, after the stitching, the stitch substrate is heated to melt and cool the nylon fiber yarn, thereby the carbon fiber yarn and the glass fiber yarn are fused and integrated to obtain a stitch substrate.

[Evaluation]
The carbon fiber stitch substrate thus obtained has a radius of curvature of 0.4 mm for the needle loop and a reasonably rounded loop shape, and can be manufactured without breakage of the stitch yarn when knitting. There were no gaps between adjacent carbon fiber yarns, and the orientation of the carbon fibers was also stitched at a predetermined orientation angle. In addition, even when this carbon fiber stitch base material was cut with scissors, the stitch yarn was not frayed from the cut surface, and the form retention of the carbon fiber stitch base material was good and the handleability was good.

[Comparative example]
As a comparative example, a yarn yarn of glass yarn was used without covering with nylon fiber in the stitch yarn. Specifically, a glass fiber yarn (glass yarn) having a fineness of 112 dtex, a tensile strength of 3.2 GPa, an elongation at break of 4.8% and a strain energy at break of 76.8 MJ / m ³ is used and the lower direction Z direction After obtaining a single yarn with a twist of 590 turns / m (= single yarn twist number), combine two of the single yarns, and in the S direction, above 472 turns / m of 80% of the single yarn twist number in the S direction A wale density of 5 W / inch (= 1.97 W / cm: 1 inch = 2.54 cm) as in the example of the product of the present invention, using a yarn of glass fiber yarn having a fineness of 225 dtex, with a twist number of twists Stitching by chain knitting with a course density of 8.5 C / inch (= 3.35 course / cm).

[Evaluation]
The carbon fiber stitch base material thus obtained could be stitched at the time of knitting in the same manner as the product of the present invention, but when the carbon fiber stitch base material is cut with scissors, the stitch yarn is loosened from the cut surface and the carbon fiber cut further There is a problem that the handleability is very bad because the stitch base material is lifted by hand.

  Although the present invention is generally configured as described above, it is by no means limited to the illustrated embodiment, and various modifications are possible within the scope of the claims, for example, stitching yarn The covering yarn of 2 is not limited to a single covering or a double covering, and a covering yarn of three or more thermoplastic polymer yarns can be adopted, and belongs to the technical scope of the present invention.

Reference Signs List 1 multiaxial stitch base material 2 stitch yarn 3 reinforcing fiber sheet 3a + 45 ° orientation reinforcing fiber sheet 3b 90 ° orientation reinforcing fiber sheet 3c-45 ° orientation reinforcing fiber sheet 3d 0 ° orientation reinforcing fiber sheet 4 needle 5 glass fiber yarn 6 thermal Plastic polymer yarn r radius of curvature

Claims (8)

It is a multiaxial stitch base material in which a plurality of reinforcing fiber sheets, in which reinforcing fiber yarns are arranged in parallel to one another, are laminated in different orientation directions and stitched together by stitch yarns penetrating these sheets. ,
The stitch yarn is a composite yarn consisting of a glass fiber yarn having a breaking strain energy of 30 MJ / m ³ or more and a thermoplastic polymer yarn having a denier of 30 to 120 dtex while having a fineness of 100 to 500 dtex,
What is claimed is: 1. A heat-resistant multiaxial stitch base material characterized in that the thermoplastic polymer yarn constituting the stitch yarn is fused and integrated with the glass fiber yarn and the reinforcing fiber yarn by being heated.   The heat resistant multiaxial stitch base material according to claim 1, wherein the stitch yarn is a covering yarn having a glass fiber yarn as a core yarn and a thermoplastic polymer yarn as a sheath yarn.   The heat-resistant multiaxial stitch substrate according to claim 1, wherein the thermoplastic polymer yarn is a yarn composed of a low melting point polymer, or a core-sheath composite yarn sheathed with a low melting point polymer.   The stitch yarn is a double covering yarn in which two thermoplastic polymer yarns of the sheath yarn constituting the yarn are wound in double in the S direction and the Z direction around the glass fiber yarn of the core yarn. The heat resistant multiaxial stitch substrate according to any one of Items 1 to 3.   The stitching yarn is characterized in that the thermoplastic polymer yarn of the sheath yarn constituting the covering yarn is a covering yarn processed with 2 to 10 windings per 1 cm of glass fiber yarn of the core yarn. The heat-resistant multiaxial stitch base material as described in any one of -3.   The heat-resistant multiaxial stitch substrate according to any one of claims 1 to 5, wherein a curvature radius of a needle loop formed by the stitch yarn is in a range of 0.3 to 2 mm.   The heat resistant multiaxial stitch substrate according to any one of claims 1 to 6, wherein a course density of stitches by the stitch yarn is 2 to 4 courses / cm.   The reinforcing fiber yarn is any single or mixed fiber selected from carbon fiber, glass fiber, aramid fiber, silica fiber, and ceramic fiber. Heat resistant multiaxial stitch substrate as described.