STITCHED FIBER-REINFORCED SUBSTRATE MATERIAL, PREFORM MATERIAL, FIBER-REINFORCED COMPOSITE MATERIAL, AND PRODUCTION METHOD FOR SAME

Abstract

An object of the present invention is to provide a stitched fiber-reinforced substrate material capable of suppressing the formation of microcracks in a fiber reinforced composite material. The stitched fiber-reinforced substrate material of the present invention is a stitched fiber-reinforced substrate material formed by stitching reinforcement fiber sheets made of reinforcement fibers using stitching yarns that exhibit an in-plane shear strength transition rate of 5% or more. The stitching yarn is preferably adhered by an organic compound having a polar group.

Claims

1. A stitched fiber-reinforced substrate material formed by stitching reinforcement fiber sheets made of reinforcement fibers using stitching yarns, the stitching yarn being a stitching yarn exhibiting an in-plane shear strength transition rate of 5% or more.

2. The stitched fiber-reinforced substrate material according to claim 1, wherein the reinforcement fiber sheet is a reinforcement fiber sheet made of unidirectionally drawn and aligned reinforcement fiber.

3. The stitched fiber-reinforced substrate material according to claim 1, wherein the reinforcement fiber sheet is formed by laminating a reinforcement fiber sheet made of unidirectionally drawn and aligned reinforcement fiber layer by layer by altering the fiber axial direction.

4. The stitched fiber-reinforced substrate material according to claim 1, wherein the stitching yarn has a linear expansion coefficient in the fiber axial direction of −1×10−6 to 70×10−6/K after heated at 180° C. for 2 hours and then cooled.

5. The stitched fiber-reinforced substrate material according to claim 1, wherein the stitching yarn is a stitching yarn to which an organic compound having a polar group is adhered.

6. A method for manufacturing a stitched fiber-reinforced substrate material, comprising: stitching a reinforcement fiber sheet made of reinforcement fiber using stitching yarns exhibiting an in-plane shear strength transition rate of 5% or more as measured by the method described in the DESCRIPTION.

7. A preform material comprising: the stitched fiber-reinforced substrate material according to claim 1 and a binder resin of 1 to 20 parts by mass with respect to 100 parts by mass of the stitched fiber-reinforced substrate material.

8. A method for manufacturing a preform material comprising: heating the stitched fiber-reinforced substrate material according to claim 1 and a binder resin under pressure.

9. A fiber reinforced composite material comprising: the stitched fiber-reinforced substrate material according to claim 1 and a matrix resin formulation of 20 to 60 parts by mass with respect to 100 parts by mass of the stitched fiber-reinforced substrate material.

10. A method for manufacturing a fiber reinforced composite material comprising: impregnating a matrix resin into the stitched fiber-reinforced substrate material according to claim 1.

11. The stitched fiber-reinforced substrate material according to claim 2, wherein the reinforcement fiber sheet is formed by laminating a reinforcement fiber sheet made of unidirectionally drawn and aligned reinforcement fiber layer by layer by altering the fiber axial direction.

Description

EXAMPLES

[0093] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the examples. The components and test methods used in this example and comparative example are described below.

Stitching Yarn

[0094] Stitching yarn 1: Aromatic copolymerized polyamide fiber obtained in production example 1 below, In-plane shear strength transition rate: 12.6%, Fineness: 33 dTex, Number of single filaments: 1, Linear expansion coefficient: −0.1×10.sup.−6/K [0095] Stitching yarn 2: Aromatic copolymerized polyamide fiber manufactured by Teijin Limited, Technora (registered trademark), 33T10, In-plane shear strength transition rate: 1.4%, Fineness: 33 dTex, Number of single filaments: 10, Linear expansion coefficient: −5 ×10.sup.−6/K

[0096] [Production example 1] Production of stitching yarn 1 Paraphenylenediamine (50 parts by mass) and 3,4′-diaminodiphenyl ether (50 parts by mass) were dissolved in NMP, terephthaloyl dichloride (100 parts by mass) was added thereto, and the mixture was subjected to a polycondensation reaction to obtain a polymer solution of 3,4′-oxydiphenylene terephthalamide. At this time, the polymer concentration was 6% by mass, and the intrinsic viscosity (IV) of the polymer was 3.38.

[0097] After heating the spinneret with a hole diameter of 0.3 mm to 105° C., the polymer solution obtained above heated to 105° C. was discharged from the spinneret and through a 10 mm air gap, and passed through a coagulation bath filled with 30% by mass NMP aqueous solution at 50° C. to obtain a fiber bundle of the coagulated polymer.

[0098] Next, the fiber bundle after coagulation was water-washed by passing through a water-washing bath adjusted to 50° C., dried with a drying roller at 200° C., and then wound on a paper tube using a winder to obtain a para-type fully aromatic copolyamide fiber of 1000 filaments.

Reinforcement Fiber

[0099] As reinforcement fiber, carbon fiber strand “Tenax (registered trademark)” HTS40-12K (manufactured by Teijin Limited, Tensile strength 4.2 GPa, Tensile elastic modulus 240 GPa, Linear expansion coefficient: −0.5 ×10.sup.−6/K) was used.

Liquid Thermosetting Matrix Resin Formulation

[0100] An amine-curable epoxy resin was used as the matrix resin for the carbon fiber composite material. The formulation is as follows. The linear expansion coefficient of the cured product was 55 ×10.sup.−6/K. (Epoxy resin) [0101] Tetraglycidyl-4,4′-diaminodiphenylmethane (Araldite (registered trademark) MY721 manufactured by Huntsman Japan KK) 20 parts by mass [0102] Triglycidyl-p-aminophenol (Araldite (registered trademark) MY0510 manufactured by Huntsman Japan KK) 30 parts by mass [0103] Triglycidyl-m-aminophenol (Araldite (registered trademark) MY0610 manufactured by Huntsman Japan KK) 30 parts by mass [0104] Bisphenol-F diglycidyl ether based epoxy resin (Araldite (registered trademark) PY306 manufactured by Huntsman Japan KK) 20 parts by mass

Curing Agent

[0105] 4,4′-diamino-3,3′-diisopropyl-5,5′-dimethyldiphenylmethane (Lonzacure (registered trademark) M-MIPA manufactured by Lonza Japan Co., Ltd.) 67 parts by mass

Evaluation Method

(1) Fiber Fineness

[0106] The obtained fiber was wound up to 100 m using a sizing reel, and the mass was measured. The obtained mass was multiplied by 100 to calculate the mass per 10000 m, and the value was taken as fineness (dtex).

(2) Tensile Strength of Stitching Yarn

[0107] The tensile strength of the stitching yarn was measured by a tensile tester (manufactured by INSTRON, trade name: INSTRON, model: 5565 type) using a thread test chuck based on the procedure of ASTM D885 under the following conditions.

Measurement Condition

[0108] Temperature: Room temperature

[0109] Specimen: 75 cm

[0110] Test speed: 250 mm/min

[0111] Distance between chucks: 500 m

(3) In-Plane Shear Strength Transition Rate

[0112] The in-plane shear strength transition rate of the stitching yarn was measured by the following method. A measurement sample of a fiber composite material composed of stitching yarn and epoxy resin was produced by using an autoclave molding method. That is, a plurality of stitching yarns was unidirectionally drawn and aligned so as to have a weight per area of 190 g/m.sup.2 to obtain a fiber sheet. Next, an epoxy resin formulation containing a glycidylamine type epoxy resin and an aromatic amine-based curing agent was prepared by mixing the following components.

Epoxy Resin Formulation

Epoxy Resin

[0113] Triglycidyl-m-aminophenol (Araldite (registered trademark) MY600 manufactured by Huntsman Japan KK) 50 parts by mass [0114] Tetraglycidyl-4,4′-diaminodiphenylmethane (Araldite (registered trademark) MY721 manufactured by Huntsman Japan KK) 50 parts by mass (Epoxy resin curing agent) [0115] 3,3′-Diaminodiphenyl sulfone (manufactured by Konishi Chemical Ind. Co., Ltd.) 45 parts by mass

Thermoplastic Resin For Viscosity Adjustment

[0116] Polyether sulfone resin (SUMIKAEXCEL PES-5003P manufactured by Sumitomo Chemical Co., Ltd.) 10 parts by mass

[0117] The obtained epoxy resin formulation was applied onto a release paper using a knife coater to prepare a resin film. Next, two sheets of the resin film were layered on both sides of the fiber sheet made of stitching yarn, heated and pressed at 90° C. to impregnate the resin formulation, and thus unidirectional prepreg (curing temperature 180° C., resin content 30%) was produced.

[0118] The obtained prepreg was cut and laminated to obtain a laminate having a laminate structure [+45/−45].sub.2s. This laminate was molded by an autoclave molding method. The molding conditions were such that molding was performed under a pressure of 0.49 MPa at a temperature of 180° C. for 120 minutes. The obtained molded product was cut into a size of 25 mm in width×230 mm in length, and the strength of the yield stress was measured in accordance with ASTM D3518 as the in-plane shear strength. When there was no yield point, the strength at the fracture point was measured as the in-plane shear strength.

[0119] The in-plane shear strength transition rate (%) was calculated by dividing the in-plane shear strength by the tensile strength of the stitching yarn according to the following formula. [0120] In-plane shear strength transition rate (%)=IPSS÷TS×100 [0121] IPSS: In-plane shear strength (MPa) [0122] TS: Tensile strength of stitching yarn (MPa)

(4) Linear Expansion Coefficient

[0123] After the fiber sample was heated at 180° C. for 2 hours while preventing tension to be applied on the sample and then cooled, the linear expansion coefficient in the line axial direction was measured by a thermomechanical analysis apparatus (TA Instruments model: TMA Q400).

Measurement Condition

[0124] Ramp start temperature: −60° C. [0125] Measurement temperature range: −50 to 70° C. [0126] Ramp end temperature: 100° C. [0127] Temperature ramp rate: 5° C./min [0128] Load: 0.0001 N

(5) Thermal Shock Test

[0129] A thermal shock tester (TSA-73EH-W manufactured by ESPEC CO., LTD.) was used to subject the fiber reinforced composite material to 1000 times of thermal cycles. One cycle of the thermal cycle was set to consist of a flat range at —55° C. for 15 minutes, followed by a ramp range reaching 70° C. for 15 minutes, a flat range at 70° C. for 15 minutes, and then a ramp range going back to −55° C. for 15 minutes, which cycle was repeated 1000 times.

(6) Crack Density

[0130] The number of cracks after the thermal shock test in the cross section inside the fiber reinforced composite material test piece was measured by microscopic observation. VHX-5000 manufactured by KEYENCE CORPORATION was used as a microscope for observation at a magnification of 200 times. Specifically, the test piece (width 80 mm x length 50 mm×thickness 5 mm) after the thermal shock test was cut into four equal parts of width 40 mm×length 25 mm, and the cut surface in the thickness direction was mirror-polished to give an observation surface for each of the long side and the short side. The microcracks are observed using a microscope in an observation range of 50 mm.sup.2 or more, and the number of cracks measured is divided by the number of layers and the width of the observation surface to give the value of crack density. The unit of crack density is cracks/(cm.Math.ply). The crack density values obtained from the observations on the long and short sides were averaged to give the final crack density.

Example 1

[0131] Stitching yarn 1 was used as the stitching yarn. The stitching yarn was washed with an organic solvent to remove the fiber oiling agent adhering to the surface of the stitching yarn. The stitching yarn was washed by circulation washing for 12 hours using a Soxhlet extractor and a mixed solution of ethanol and benzene as an organic solvent.

[0132] The stitching yarn after washing was dried in a vacuum dryer for 12 hours.

[0133] Then, the stitching yarn from which the fiber oiling agent was removed was continuously immersed in the treatment agent solution to apply the treatment agent. Used as the treatment agent solution was a 5 wt % aqueous solution of aliphatic epoxy compound “Denacol” (registered trademark) EX832 (polyoxyethylene diglycidyl ether manufactured by Nagase ChemteX Corporation, Number of epoxy groups: 2, Epoxy equivalent: 284 g/Eq) (weight ratio of polyoxyethylene diglycidyl ether/water=1:19). After removing excess water with a roller, the stitching yarn provided with a treatment agent solution was dried at 100° C. for 1 hour using a hot air dryer.

[0134] Four reinforcement fiber sheets with 200 reinforcement fibers unidirectionally drawn and aligned were prepared and laminated by altering angles in the order of −45°, 0°, +45°, 90° to give a laminate sheet of laminated four unidirectionally drawn and aligned reinforcement fiber sheets. Next, the laminate sheet was sewn (stitched) through the laminate sheet using a stitching yarn provided with a treatment agent to give a stitched fiber-reinforced substrate material (reinforcement fiber weight per area per layer: 190 g/m.sup.2, stitching yarn usage amount: 4 g/m.sup.2, stitched fiber-reinforced substrate material total weight per area: 764 g/m.sup.2).

[0135] The obtained stitched fiber-reinforced substrate material was cut into a size of 300×300 mm. Next, six stitched fiber-reinforced substrate materials were laminated on a mold release treated aluminum plate of 500×500 mm to form a laminate (preform material [−45°/0°/+45°/90°].sub.3s).

[0136] Then, using the obtained laminate and the liquid thermosetting resin formulation, a fiber reinforced composite material was manufactured by a resin transfer molding method. First, on the laminate laminated were Release Ply C (manufactured by AIRTECH) of peel cloth, which is a substrate material provided with a mold release function, and Resin Flow 90HT (manufactured by AIRTECH), which is a resin distribution substrate material. Then, hoses for forming a resin injection port and a resin discharge port were arranged, whole the mold was covered with a nylon bag film, sealed with a sealant tape, and the inside was evacuated. Subsequently, the aluminum plate was heated to 120° C., the pressure in the bag was reduced to 5 torr or less, and then the above-mentioned liquid thermosetting resin (33 parts by mass based on 100 parts by mass of the stitched substrate material) heated to 100° C. was injected into the vacuum system through the resin injection port. The injected liquid thermosetting resin filled the bag and was impregnated into the laminate, and under this condition, the temperature was raised to 180° C. and kept at 180° C. for 2 hours to obtain a fiber reinforced composite material.

[0137] The crack density was measured using the obtained fiber reinforced composite material. As a result, almost no crack was generated, and the crack density was as low as 0.12 cracks/(cm.Math.ply). The formation of microcracks was confirmed to be suppressed by weaving the stitched fiber-reinforced substrate material using stitching yarn 1.

Comparative Example 1

[0138] A stitched fiber-reinforced substrate material and a fiber reinforced composite material were obtained in the same manner as in example 1 except that stitching yarn 2 was used as the stitching yarn instead of stitching yarn 1. The crack density was measured using the obtained fiber reinforced composite material. The fiber reinforced composite material obtained in comparative example 1 in which stitching yams exhibiting a low in-plane shear strength transition rate were used was confirmed to have a significant generation of microcracks, and the crack density of 0.23 cracks/(cm.Math.ply) was high as compared with example 1.

CITATION LIST

Patent Literature

[0139] [PTL 1] Japanese Unexamined Patent Application Publication (Translation of PCT Application) NO. 2012-511450

Non-patent literature

[0140] [NPL 1] Pierre-Jacques Liotier et al., Composites: Part A 42 (2011), 425-437