JP2014104669A - Method for molding twist yarn-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a twist yarn-reinforced composite material using natural fiber as a reinforcing material at a low cost by simple equipment, to increase the mechanical properties of the twist yarn-reinforced composite material, and to increase its moldability by resin impregnation.SOLUTION: The twist yarns of natural fiber are used as reinforcing fiber, the molten resin of a natural resin-based matrix resin is impregnated in a vacuum state, and curing is performed to mold a twist yarn-reinforced composite material by a vacuum auxiliary resin impregnation process. The twist per inch (TPI) of the twist yarns of the natural fiber is controlled to 1 to 10, and further, the twist yarns with different TPI are arranged in parallel in a plurality of groups in such a manner that the twist yarns are present extensively to the direction of the impregnation of the resin, and the twist per inch (TPI) changes in a direction crossed therewith.

Description

  The present invention relates to a method for forming a twisted yarn reinforced composite material, and more particularly to a method for forming a twisted yarn reinforced composite material with improved formability and tensile properties of a unidirectional twisted yarn reinforced green composite by VaRTM.

  Since fiber reinforced plastic (FRP) is excellent in strength, heat resistance and corrosion resistance and has great advantages in weight reduction, it is used as various general-purpose structural members such as automobiles and aircraft. There is a vacuum assisted resin impregnation molding method (VaRTM: Vacuum Assisted Resin Transfer Molding) for the FRP molding method, which does not require large-scale equipment, is low in cost, and facilitates the integral molding of large structural members. It has a feature that the void (bubble) content is low, and various research and development have been made.

  At present, CFRP and GFRP using artificial fibers such as carbon fiber and glass fiber and thermosetting resins such as epoxy resin have been put into practical use as FRP, which have excellent mechanical properties. However, there is a problem that the amount of energy consumption is large, the disposal after disposal is difficult to perform, and the environmental load is large. For these reasons, recently, a natural fiber reinforced resin using a high-strength plant fiber as a reinforcing material has attracted attention as an environmentally friendly green composite (GC) and has been researched and developed. In the case of using natural fiber as a reinforcing material like GC, spun yarn (twisted yarn) is used because of the need to take the form of continuous fiber, and twisted yarn made of such natural fiber and a composite formed using it The relationship with the mechanical properties of materials has not yet been elucidated.

  Patent Document 1 describes a method of manufacturing a constituent member of a fiber reinforced structure in which a roving bundle as at least one layer of the constituent member is wetted with a matrix material before being placed in a mold. In Patent Document 2, when molding fiber reinforced plastic by the VaRTM method, a resin amount that fills the gap between the sealing medium and the mold is injected, and the resin amount impregnated in the reinforcing fiber material is controlled, It describes a method for molding a fiber reinforced plastic in which the thickness of the molded product and the fiber volume content are controlled. Non-Patent Document 1 describes the effects of fabric density and yarn twist on the mechanical properties in GC, and Non-Patent Document 2 describes a large FRP structure used for wind turbines using glass fibers by VaRTM. Describes techniques for manufacturing the body.

  The thing of patent document 1 is related to structural members, such as a windmill blade, and is not related to GC, and in patent document 2, the thing which uses natural fiber as a reinforced fiber is included, but strength and weight reduction are included. In regard to this point, it is shown that the fiber volume content of the fiber reinforced plastic is controlled, and there is no specific indication as to how the reinforcing fiber is actually used. Further, Non-Patent Document 1 shows the influence of the fabric density and yarn twist in GC on the mechanical properties, but it does not specifically show the forming of GC by VaRTM. The FRP applied to the structural member is molded by VaRTM, but is not specifically shown for GC.

JP 2012-16948 A JP 2010-173165 A

Rie Nakamura et al. “Effects of Fabric Density and Yarn Twist on Mechanical Properties of Textile Green Composites”, Materials (Journal of the Society of Materials Science, Japan), Vol. 58, No. 5, May 2009, pp.382 -388 Kentaro Shindo et al. “Manufacturing technology of large composite materials by VaRTM (vacuum impregnation method)”, Mitsubishi Heavy Industries Technical Review, Vol. 43 No. 1, 2006, pp. 11-12

  Many fiber reinforced plastics (FRP), which is a composite material of fiber reinforcement and resin, are currently manufactured and used for artificial fibers such as carbon fibers and glass fibers and thermosetting resins such as epoxy resins. The CFRP and GFRP used are problematic in that they consume a large amount of energy in the manufacturing process, are difficult to perform after disposal, and have a large environmental load. For this reason, it is required to develop a technology for producing and using a green composite using natural fibers as a reinforcing material.

  In addition, as a method of manufacturing a composite material without requiring large-scale equipment in the manufacturing process, molding is performed by a vacuum auxiliary resin impregnation molding method. For example, a composite material using carbon fiber, which is an artificial fiber, as a reinforcing material In this case, since the carbon fiber plain woven fabric is woven using a weaving machine, the fiber spacing cannot be arbitrarily controlled. Therefore, the resin flow rate is controlled during molding by the vacuum assisted resin impregnation molding method. It is something that cannot be done. Furthermore, although the demand for enhancing the mechanical properties of the composite material of the green composite is increasing, the conditions for the molding method of the composite material using such natural fibers as a reinforcing material have not yet been clarified.

  The present invention relates to a twisted yarn reinforced composite material made of natural fiber as a reinforcing material, and does not require a large-scale facility by a vacuum assisted resin impregnation molding method. The purpose is to increase.

  The present invention has been made to solve the above-mentioned problems, and a method for molding a twisted yarn-reinforced composite material according to the present invention uses a natural fiber twisted yarn as a reinforcing fiber, and a molten resin of a natural resin matrix resin in a vacuum state. Is a method of forming a twisted yarn reinforced composite material by a vacuum assisted resin impregnation method, wherein the twist number TPI per inch of the twisted yarn of natural fiber as the reinforcing fiber is 1 or more and 10 or less. is there.

  In addition, the method for molding the twisted yarn reinforced composite material according to the present invention includes a natural fiber twisted yarn as a reinforcing fiber, impregnated with a molten resin of a natural resin matrix resin in a vacuum state and cured to form the twisted yarn reinforced composite material as a vacuum auxiliary resin. This is a method of molding by an impregnation method, in which twisted yarns of natural fibers as reinforcing fibers extend in the direction of impregnation of the resin, and the TPI of the twisted yarn changes in the direction intersecting with the twist number per inch as TPI. Thus, it is good also as what controlled the fluidity | liquidity of resin by arrange | positioning several sets of twisted yarns of different TPI in parallel.

  The method for forming a twisted yarn reinforced composite material according to the present invention uses natural yarn twisted yarn as a reinforcing fiber, impregnated with a molten resin of a natural resin-based matrix resin in a vacuum state, and cured to form a twisted yarn reinforced composite material by a vacuum auxiliary resin impregnation method. By adopting a molding method, the twist number TPI per inch of the twisted yarn of the natural fiber as the reinforcing fiber is 1 or more and 10 or less, thereby improving the mechanical properties of the twisted yarn reinforced composite material and molding the composite By combining and arranging twisted yarns with different TPIs according to the shape and form of the material, the controllability of the resin impregnation speed can be improved, the moldability of the composite material can be improved, and the generation of voids can be significantly reduced. It is.

It is a figure which shows the apparatus form which shape | molds the twisted-yarn reinforcement | strengthening composite material by a vacuum auxiliary resin impregnation method as sectional drawing. It is a graph which shows the mechanical characteristic of the shape | molded twisted yarn reinforcement | strengthening composite material test piece. It is a photograph of a cross section of a test piece, showing (a) a twisted yarn having a TPI of 1.5 and (b) a twisted yarn having a TPI of 9.5. It is a figure which shows the flow state of the resin in the VaRTM shaping | molding test about the one-dimensional flow which has arrange | positioned the twisted yarn from which TPI differs. It is a figure which shows the flow state of the resin in the VaRTM shaping | molding test about the twisted yarn bundle with uniform TPI, and the twisted yarn bundle from which TPI differs.

Hereinafter, an embodiment of a method for forming a VaRTM of a twist-reinforced composite material according to the present invention will be described.
(A) Molding of FRP by VaRTM An apparatus configuration for molding FRP using natural fibers as reinforcing fibers by VaRTM (vacuum assist resin impregnation molding method) will be schematically described.
FIG. 1 is a diagram schematically showing a form of forming by VaRTM. In FIG. 1, reference numeral 1 denotes a mold made of a material such as stainless steel. A mold release sheet 2 such as Teflon (registered trademark of polytetrafluoroethylene) is arranged on the mold 1 and a reinforcing fiber 3 is placed thereon. Then, this is covered with peel ply 4 (Bleeder Lease B manufactured by Airtech Co., Ltd.), and the media mesh 5 is overlaid thereon. The media mesh 5 is a net-like sheet material arranged to diffuse the matrix resin, and the peel ply 4 is arranged to facilitate the removal of the media mesh 5.

  A resin injection line 6 (on the right side in FIG. 1) and a vacuum suction line 7 (on the left side in FIG. 1) are arranged on those loaded with sealant tape 8 (Air-Tech, AT-200Y). The entire portion surrounded by the sealant tape 8 is covered with a bagging film 9 so that the inside is sealed except for the resin injection conduit 6 and the vacuum suction conduit 7. The bagging film 9 does not wrinkle due to vacuum pressure and has heat resistance, and an elongation rate of 350%, a 170 ° C. heat resistant film Wrightlon 5400 (manufactured by Airtech), etc. are used.

  The resin injection line 6 and the vacuum suction line 7 are each opened and closed by an on-off valve, the resin injection line 6 side is connected to a molten resin supply source (not shown), and the vacuum suction line 7 is a vacuum pump (not shown). Z). In the apparatus configuration of FIG. 1, the mold and the vacuum pump are used through many times of molding of the composite material, and other parts remain attached and deformed, so that the apparatus is configured instead of a new one after molding. The

In the apparatus configuration as shown in FIG. 1, the twisted reinforced composite material is molded by VaRTM molding.
In the apparatus configuration in which the reinforcing fibers 3 are arranged as shown in FIG. 1, the on-off valve on the resin injection side is closed, and the resin, polymerization initiator, and diluent are held in a stirred state. Next, the opening / closing valve on the evacuation side is opened and vacuum suction is performed, so that the portion between the mold 1 including the reinforcing fibers 3 and the bagging film 9 is in a reduced pressure state. Thereafter, the on-off valve on the resin injection side is opened, the resin is injected, and the reinforcing fibers 3 are impregnated. As the resin injection amount, the amount impregnated over the entire reinforcing fiber 3 is obtained in advance, and when a predetermined amount of resin is injected, the on-off valve on the resin injection side is closed. After the impregnation of the resin, the on-off valve on the vacuum suction side is closed, and the reinforcing fiber 3 impregnated with the resin is cured for a predetermined time at a predetermined temperature in a high-temperature dryer, and the composite material forming process is completed.

(B) Implementation of molding of twisted yarn reinforced composite material using natural fibers In the present invention, ramie single yarn (16th) manufactured by Tosco Corporation is used as the reinforcing fiber, and TPI (Twist per inch) is 1.5 respectively. , 3.5, 6.5, 9.5 twisted yarn using a manual twister (manufactured by Yamaguchi University) and fixed in the prescribed shape, and the matrix resin is an epoxidized soybean oil with an acrylate moiety Acrylate (Daicel Cytec, BECRYL860; hereinafter referred to as AESO resin) was used. The AESO resin can be obtained by epoxidizing soybean oil mainly composed of neutral fat and then radicalizing it after reacting with acrylic acid. As a polymerization initiator, t-butyl peroxybenzoate manufactured by Wako Pure Chemical Industries, Ltd. is used, and a styrene monomer is used as a diluent for viscosity control. The mixing ratio of the AESO resin, the polymerization initiator, and the diluent is 200: 3: 30.

  In the apparatus configuration as shown in FIG. 1, the reinforcing fibers of the twisted yarn as described above are arranged, sealed and evacuated, and then the matrix resin as described above is injected to form a test piece of the twisted yarn reinforced composite material. Tests for measuring properties and moldability were conducted.

  As the reinforcing fiber of the test piece to be molded, a twisted yarn having a TPI of 1.5, 3.5, 6.5, or 9.5 is used, and for each TPI twisted yarn, an AESO resin, a polymerization initiator, and a diluent are mixed at 300 rpm for 1 minute. , And cured at 100 ° C. for 2 hours and further at 120 ° C. for 2 hours, and a twisted-reinforced composite specimen AR1.5 according to TPI1.5, 3.5, 6.5, 9.5 of the reinforcing fiber twisted yarn, AR3.5, AR6.5, and AR9.5 were prepared.

  Moreover, the NEAT test piece was produced separately. This is a resin-only test piece. After mixing AESO resin, polymerization initiator, and diluent at 300 rpm for 1 minute, air bubbles are removed with a vacuum pump, and then a Teflon plate frame with excellent releasability and heat resistance is used. The resin was poured and cured using a high temperature dryer at 100 ° C. for 2 hours and at 120 ° C. for 2 hours.

  The dimensions of the test piece were a gauge length of 90 mm, a width of 15 mm, and a thickness of 2 mm, and GFRP tabs were attached to both sides of the test piece to prepare a test state. The tensile tester was an Instron type tensile tester (Autograph IS-5000 manufactured by Shimadzu Corporation), the strain was measured by the gauge method, the tensile speed was 1 mm / min, and the test was carried out until the test piece broke. .

  Tensile tests were performed on specimens AR1.5, AR3.5, AR6.5, AR9.5 and NEAT specimens of twisted yarn reinforced composite material produced as described above. Table 1 shows the mechanical properties and flow velocity of each test piece as a result, and FIG. 2 shows a typical stress strain diagram of each test piece.

  From the results of the tensile test, it can be seen that the resin alone (NEAT test piece) can hardly handle the load, but the strength and Young's modulus are greatly improved by using a composite material in which the twisted yarn is a reinforcing fiber. Further, the improvement rate depends on the number of twists of the twisted yarn, and it has been found that the smaller the TPI (twist number), the higher the improvement rate in both strength and Young's modulus. However, the fracture strain tends to decrease as TPI decreases.

As a test for formability, the impregnation speed of the resin in the case of twisted yarn specimens AR1.5, AR3.5, AR6.5, AR9.5 with different numbers of twists was investigated, and the results are also shown in Table 1. . From the results of the impregnation rate shown in Table 1, it can be seen that the flow rate increases as the number of twists increases. From the law of constant flow rate (Q = AV, Q: flow rate [m ³ / s], A: cross-sectional area [m ² ], V: flow velocity [m / s]), twisted yarn with a larger number of twists has a higher flow rate. Can be said to grow.

  FIG. 3 (a) shows a case where TPI = 1.5, and FIG. 3 (b) shows a photograph of the cross section of the observed test piece, where TPI = 9.5. Not confirmed. The same observation results were obtained in a test using a TPI3.5 20-twisted twisted yarn, in which the styrene monomer content was adjusted to change the viscosity of the resin. This confirms that the VaRTM moldability (presence or absence of voids) of the unidirectional twisted-yarn-reinforced composite concerned is not affected by the twisted yarn structure, and the VaRTM moldability is good.

  The smaller the TPI, the smaller the twist angle with respect to the tensile axis, which is considered to correspond to an increase in strength and Young's modulus. For twisted yarns, TPI = 0 is a fiber bundle that is aligned in one direction, and in this case it should exhibit maximum strength and maximum Young's modulus. However, when there is no constraint due to twisting at TPI = 0, the gap between the fiber bundles cannot be controlled, and the resin impregnation rate in VaRTM molding cannot be controlled. Considering this, it can be said that the lower limit of application of TPI is TPI = 1. Further, when the TPI increases, the resin impregnation rate can be easily controlled, but the mechanical strength and Young's modulus decrease. Therefore, in practice, the upper limit of TPI is considered to be TPI = 10. When the TPI is in the range of 1 or more and 10 or less, it is suitable in terms of tensile strength, mechanical properties such as Young's modulus, and formability by VaRTM when actually used in various applications.

(C) Resin moldability test As described above, in the formation of a twisted yarn reinforced composite material, the smaller the TPI of the reinforcing fiber twisted yarn, the higher the strength and Young's modulus, and the higher the TPI, the faster the flow rate. The flow rate is directly related to the moldability of the composite material. When the TPI increases, the distance between the single yarns in the twisted yarn decreases, so that the capillary pressure increases and the flow rate of the resin increases. In resin impregnation molding where there is a high pressure difference between the inlet and outlet of resin impregnation, the speed of resin flow between fiber bundles is faster than the speed of resin flow in the fiber bundle, but as with VaRTM, the resin due to the difference between vacuum pressure and atmospheric pressure. In impregnation molding, the speed of the resin flow between the fiber bundles is slower than the speed of the resin flow in the fiber bundles. To confirm this, VaRTM molding test for one-dimensional flow with twisted yarns with different TPIs. Went.

  FIG. 4 shows the flow state of the resin in the test results. In the state where the resin is impregnated with five twisted yarns each having a TPI of 1.5, 3.5, 6.5, and 9.5 arranged in parallel. The state of the resin flow based on the photographing after 4 minutes from the flow start is shown. The twisted yarns are arranged so that the twisted yarns extend in the direction of impregnation with the resin, and the twisted yarns of different TPIs are arranged in parallel so that the TPI of the twisted yarns changes in the direction crossing the twisted yarns. From this result, the TPI dependence of the resin flow rate can be confirmed, and the speed of the resin flow between the fiber bundles is lower or the same as the speed of the resin flow in the fiber bundle. Then, it turns out that resin mainly flows and impregnates the inside of a fiber bundle.

  Furthermore, a VaRTM molding test for a two-dimensional flow was performed as a comparison between a twisted yarn bundle having a uniform TPI and a twisted yarn bundle having a different TPI juxtaposed. FIG. 5 shows the results. Twelve yarns having a TPI of 1.5 are arranged in the upper path so as to surround the non-flowing portion of the rhombus in the center, and the TPI is 1.5, 3.5, 6.5 in the lower path, respectively. , 9.5 twisted yarns arranged in parallel, the resin is impregnated at the same time, and shows the state of resin flow based on photographing 5 minutes after the start of flow. In the lower path, the twisted yarn whose flow rate is slow is arranged on the inner side (upper side).

  From this result, the speed of the resin flow inside the short path becomes faster in the upper path composed of the same twisted yarn with TPI, while the lower path with juxtaposed twisted yarns with different TPIs depends on the flow velocity. It can be seen that the resin flow is observed.

  In this way, when a composite material is formed by impregnating a resin into a reinforcing fiber of twisted yarn, the TPI of the twisted yarn is related to the mechanical properties of the composite material, and is also a factor related to moldability by resin flow. Yes. As can be seen from the results shown in FIG. 5, when a uniform TPI twist yarn in the upper path is arranged, the resin flows according to the flow path, but different TPI twist threads in the lower path are combined. When juxtaposed, the resin flow state depends on the flow rate according to the TPI, which means that the moldability by resin impregnation can be improved by changing the combination arrangement of TPI according to the shape and form of the composite material to be molded. It represents that it can be controlled.

  For example, when molding a panel having a thick wall and a curved surface, if the same TPI twisted yarn is used, the outermost layer is likely to be voided due to the difference in resin flow rate, resulting in a decrease in strength of the composite material to be molded. However, the occurrence of voids can be prevented by adopting the arrangement form such that the twisted yarns of different TPI are combined and juxtaposed according to the shape form of the panel to be molded and the resin impregnation form into the twisted yarn. It becomes possible.

  In the above, in the examples, ramie hemp twisted yarn was used as the reinforcing fiber, but the plant-based natural fibers are mostly composed of substances such as cellulose, hemicellulose, lignin, and the ratio is only different. Besides, for example, Flax hemp can be used as well. Moreover, although what used the epoxidized soybean oil acrylate was shown in the Example as a matrix resin, natural origin resin, such as BIOMUP 639P (made by Nippon Iupika Co., Ltd.), is used for others.

1 type 2 sheet 3 reinforced fiber 4 peel ply 5 media mesh 6 resin injection line 7 vacuum suction line 8 sealant tape 9 bagging film

Claims (2)

  A method of forming a twisted fiber reinforced composite material by a vacuum auxiliary resin impregnation method using a natural fiber twisted yarn as a reinforcing fiber and impregnating and curing a molten resin of a natural resin matrix resin in a vacuum state. A method for forming a twisted reinforced composite material by a vacuum assisted resin impregnation method, wherein the twist number TPI per inch of the twisted yarn of the fiber is 1 or more and 10 or less.   A method of forming a twisted fiber reinforced composite material by a vacuum auxiliary resin impregnation method using a natural fiber twisted yarn as a reinforcing fiber and impregnating and curing a molten resin of a natural resin matrix resin in a vacuum state. A plurality of twisted yarns of different TPIs are arranged in parallel so that the twisted yarns of the fibers extend in the direction of impregnation of the resin, and the TPI of the twisted yarns changes in the direction intersecting with the number of twists per inch as TPI. A method for forming a twisted reinforced composite material by a vacuum assisted resin impregnation method, wherein the fluidity of the resin is controlled by: