Method for producing pultruded molding

Abstract

To provide a method for producing a pultruded molding, capable of reducing the pultrusion force both before and after curing in a mold, and yielding a pultruded molding with excellent appearance and dimensional precision.SOLUTION: A method of producing a pultruded molding, the method including curing a material that contains components (A)-(D) and meets conditions (I) and (II). [Components] (A) carbon fiber; (B) an epoxy base agent selected from bisphenol A type and bisphenol F type; (C) an epoxy base agent selected from aminophenol type, novolac type, and aliphatic ether type; (D) at least one epoxy curing agent selected from cyanamide type and alicyclic amine type. [Conditions] (I) the volumetric expansion ratio V80 / V25, when the mixture of (B) and (C) is heated from 25°C to 80°C, satisfies a predetermined relational expression; (II) the viscosity increase ratio of the mixture of (B), (C), and (D) after 90 minutes at 25°C is 1.80 times or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a pultruded article containing carbon fiber and epoxy resin. [Background technology]

[0002] Carbon fiber reinforced composites (CFRP), which are made from carbon fiber (CF) and thermosetting resins, are lightweight and have excellent mechanical properties, and have therefore been applied in many fields, including aerospace, railway vehicles, ships, civil engineering and construction, and sporting goods.

[0003] The manufacturing methods for CFRP using thermosetting resins include the prepreg method, hand layup method, filament winding method, pultrusion method, and RTM (Resin Transfer Molding) method, which are appropriately selected. Among these, the pultrusion method is known as a cost-effective method because it allows for the relatively easy and continuous production of CFRP with unidirectionally aligned CF. In the pultrusion method, reducing the pulling force directly leads to improved productivity, so reducing the pulling resistance when the resin-impregnated CF passes through the mold is an issue.

[0004] Patent Document 1 discloses a method for pultrusion molding using a reinforcing fiber bundle impregnated with epoxy resin, in which an acid anhydride curing type epoxy resin composition is used and the mold temperature is controlled to maintain a certain range of curing degree, and it is said that by reducing the curing shrinkage inside the mold, the generation of resin scale (resin residue) can be suppressed and the pulling resistance can be reduced. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2019 / 151174 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technique of Patent Document 1 has a problem in that the pulling force cannot be sufficiently reduced because the pulling resistance increases due to the thermal expansion of the epoxy resin before hardening near the mold entrance during pultrusion molding. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides a method for producing a pultrusion molded article, which comprises curing a material that contains components (A) to (D) and satisfies conditions (I) and (II). [component] (A) Carbon fiber (B) an epoxy base resin selected from bisphenol A type and bisphenol F type (C) an epoxy base resin selected from aminophenol type, novolac type, and aliphatic ether type (D) One or more epoxy curing agents selected from cyanamide type and alicyclic amine type [conditions] (I) The volume expansion rate V of a mixture of (B) and (C) when heated from 25°C to 80°C 80 / V 25 satisfies the following relation (1):

[0008]

number

[0009] V 80 : Density (g / cm) of a mixture of component (B) and component (C) at 80°C 3 ) V 25 : Density (g / cm) of a mixture of component (B) and component (C) at 25°C 3 ) (II) The viscosity increase ratio of the mixture of (B), (C) and (D) after 90 minutes at 25°C is 1.80 times or less. [Effects of the Invention]

[0010] According to the present invention, the thermal expansion of the epoxy resin before curing is reduced before and after curing in the mold, thereby reducing the pulling force, and the resulting pultrusion-molded product has good appearance and dimensional accuracy. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing the manufacturing process of pultrusion. [Figure 2] FIG. 1 is a schematic diagram illustrating an embodiment of a pultrusion molded product. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described in detail.

[0013] <Outline of the manufacturing process for extruded products> FIG. 1 is a schematic diagram showing a manufacturing process 1 for a pultrusion molded product. Carbon fibers 2 set on a creel 3 are pulled out in one direction and passed through an eyelet guide before being introduced into a resin bath 4 containing an uncured epoxy resin composition and impregnated with the resin composition. The carbon fibers 2 are then passed through squeeze dies 5 and 6 to squeeze out excess resin composition from the impregnated carbon fibers 2 to achieve a predetermined fiber content. The carbon fibers 2 from which the excess resin composition has been squeezed out are then introduced into a heated mold 7, where the epoxy resin composition is cured and molded by heating in the heated mold 7. The cured pultrusion molded product 9 is then pulled out by a puller 8 and wound into a coil by a winder 10.

[0014] One embodiment of a pultrusion molded product 9 obtained by such a manufacturing process is shown in Figure 2. Figure 2A is a schematic diagram of a plan view of the pultrusion molded product 9, i.e., a view from above in Figure 1, with the arrow indicating the pultrusion direction. Figure 2B is a schematic diagram of a cross section perpendicular to the longitudinal direction of the pultrusion molded product 9. As shown in these figures, the pultrusion molded product 9 has a structure in which carbon fibers 2 are dispersed and arranged in epoxy resin 11.

[0015] <Component (A): Carbon fiber> The carbon fiber used in the pultrusion molded product of the present invention is not particularly limited, but examples thereof include polyacrylonitrile (PAN)-based carbon fibers made from PAN fibers, pitch-based carbon fibers made from petroleum tar or petroleum pitch, etc. Among these carbon fibers, PAN-based carbon fibers are preferably used because of their excellent balance between strength and elastic modulus.

[0016] Typically, one or more carbon fiber bundles each made up of a large number of single fibers are arranged side by side. The number of carbon fiber filaments (single fibers) when one or more carbon fiber bundles are arranged is preferably 1,000 to 2,000,000. From the viewpoint of productivity, the number of filaments of the reinforcing fiber is more preferably 1,000 to 1,000,000, further preferably 1,000 to 600,000, and particularly preferably 1,000 to 300,000.

[0017] <Component (B): Epoxy base resin selected from bisphenol A type and bisphenol F type> Examples of bisphenol A type and bisphenol F type epoxy base resins that can be used in the present invention are shown below.

[0018] Bisphenol A type epoxy resin refers to a resin having the structural formula shown in (1) below.

[0019] [ka]

[0020] Commercially available examples of such epoxy resins include jER (registered trademark) 825, jER (registered trademark) 827, and jER (registered trademark) 828 (all manufactured by Mitsubishi Chemical Corporation), and Araldite (registered trademark) LY3585 (manufactured by Huntsman).

[0021] Bisphenol F type epoxy resin refers to a resin having the structural formula shown in (2) below.

[0022] [ka]

[0023] Commercially available examples of such epoxy resins include "jER (registered trademark)" 806 and "jER (registered trademark)" 807 (both manufactured by Mitsubishi Chemical Corporation) and "EPICLON (registered trademark)" 830 (manufactured by DIC Corporation).

[0024] <Component (C): Epoxy base resin selected from aminophenol type, novolac type, and aliphatic ether type> The aminophenol-type, novolac-type, and aliphatic ether-type epoxy base resins used in the present invention are shown below. In the present invention, an aminophenol-type epoxy base resin is preferably used to increase the strength of the pultrusion molded product, and an aliphatic ether-type epoxy base resin is preferably used when low pull-out force and appearance quality are important.

[0025] The aminophenol type epoxy resin refers to a resin having the structural formula shown in (3) below, and a representative example is triglycidyl aminophenol.

[0026] [ka]

[0027] Examples of commercially available epoxy resins include "JER (registered trademark)" 630 (manufactured by Mitsubishi Chemical Corporation), "Araldite (registered trademark)" MY0600, and "Araldite (registered trademark)" MY0510 (all manufactured by Huntsman).

[0028] Novolac epoxy resin refers to a resin having the structural formula shown in (4) below, and a representative example is phenol novolac resin.

[0029] [ka]

[0030] An example of a commercially available epoxy resin is "JER (registered trademark)" 154 (manufactured by Mitsubishi Chemical Corporation).

[0031] Aliphatic ether type epoxy resin refers to a resin having the structural formula shown in (5) below, and representative examples include ethylene glycol diglycidyl ether epoxy, trimethylolpropane polyglycidyl ether epoxy, hexanediol glycidyl ether epoxy, sorbitol polyglycidyl ether epoxy, and propylene glycol glycidyl ether epoxy.

[0032] [ka]

[0033] Examples of commercially available epoxy resins include "Denacol (registered trademark)" EX-810, "Denacol (registered trademark)" EX-321L, "Denacol (registered trademark)" EX-212, and "Denacol (registered trademark)" EX-614B (all manufactured by Nagase Chemtec Corporation), and "ADEKA GLYCIROL (registered trademark)" ED-503 (manufactured by ADEKA Corporation).

[0034] <Component (D): One or more epoxy curing agents selected from cyanamide-type and alicyclic amine-type> The cyanamide-type and alicyclic amine-type epoxy curing agents used in the present invention are shown below. Note that, as the curing agent used in the present invention, a cyanamide-type epoxy curing agent is preferably used from the viewpoints of the curing speed in the mold and the viscosity stability in the resin bath.

[0035] An example of a cyanamide-type epoxy curing agent is dicyandiamide. Examples of commercially available cyanamide-type epoxy curing agents include "DICY7T" (manufactured by Mitsubishi Chemical) and "Diehard (registered trademark)" Fluid 111 (manufactured by AlzChem).

[0036] Examples of alicyclic amine-type epoxy curing agents include isophoronediamine and cyclohexylamine. Commercially available alicyclic amine-type epoxy curing agents include "VESTAMIN (registered trademark)" IPD (manufactured by Evonik Japan Co., Ltd.) and "Baxxodur (registered trademark)" EC201 (manufactured by BASF).

[0037] When a cyanamide-type epoxy curing agent is used, an aromatic urea compound can be used in combination as a curing accelerator, which can shorten the curing time in the mold and increase the productivity of drawing.

[0038] Examples of aromatic urea compounds include 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, 4,4'-methylenebisphenyldimethylurea, phenyldimethylurea, and toluenebisdimethylurea. Commercially available aromatic urea compounds include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), Omicure® 24 (manufactured by PTI Japan), and Diehard® UR505 (manufactured by CVC).

[0039] Cyanamide-type and alicyclic amine-type epoxy curing agents are preferably blended so that the moles of active hydrogen in component (D) divided by the moles of active epoxy groups in 100 parts by weight of the total epoxy base resin is 0.8 to 1.2 equivalents. If the ratio of moles of active epoxy groups to moles of active hydrogen falls within this range, it is possible to obtain a cured epoxy resin product with good heat resistance and mechanical properties.

[0040] <Method for preparing an epoxy mixture of components (B), (C), and (D)> The method for preparing the epoxy mixture of the present invention is not particularly limited. For example, the mixture may be kneaded using a machine such as a kneader, a planetary mixer, a three-roll mill, or a twin-screw extruder, or in the case of laboratory-scale production, the mixture may be mixed by hand using a beaker and a spatula, for example.

[0041] <Volume expansion coefficient V of the mixture of component (B) and component (C) 80 / V 25 About > The volume expansion coefficient of the mixture of components (B) and (C), which are the epoxy base resins of the present invention, satisfies the following relational expression (1): 80°C is assumed to be the gel state of the epoxy resin in the mold, and 25°C is assumed to be the state before curing, and the change in volume from 25°C to 80°C has a significant effect on the pull-out resistance within the mold.

[0042]

number

[0043] V 80 : Density (g / cm) of a mixture of component (B) and component (C) at 80°C 3 ) V 25 : Density (g / cm) of a mixture of component (B) and component (C) at 25°C 3 ) Contains component (B) and component (C), and V 80 / V 25 By setting the ratio within the range of the present invention, the pultrusion force can be reduced, significantly improving productivity, while maintaining the excellent dimensional accuracy of the pultrusion molded product. Here, the volume expansion coefficient is calculated using the resin density measured with a liquid hydrometer at 25°C and 80°C, according to the method described in the Examples below.

[0044] <Thickening ratio of a mixture of components (B), (C), and (D)> In the present invention, the epoxy mixture of components (B), (C) and (D) before curing is It is necessary that the viscosity increase ratio after 90 minutes at 25°C is 1.80 times or less. If this range is not met, the viscosity will increase in the resin bath, increasing the risk of increased process fluff and poor impregnation of pultrusion molded products.

[0045] The viscosity increase ratio here means viscosity stability relative to the initial viscosity at 25°C, and is calculated as the rate of change in complex viscosity measured by the method described in the examples below.

[0046] <Mechanical properties of pultrusion molded products> In the present invention, when an aminophenol-type epoxy base resin is selected as component (C) and a cyanamide-type epoxy curing agent is selected as component (D), the bending strength of the resulting pultrusion molded product is improved. Specifically, under the conditions of the examples described below, the product is suitable for use as a structural member for wind turbine blades, which require bending properties, particularly as a structural member for spar caps.

[0047] <Surface smoothness of pultrusion molded products> Furthermore, it has been found that the surface smoothness of pultrusion molded articles is improved by selecting an aliphatic ether-type epoxy base resin as component (C) and a cyanamide-type epoxy curing agent as component (D). Specifically, under the conditions of the examples described below, it is possible to reduce the arithmetic mean roughness Ra of the pultrusion molded article surface to 0.4 μm or less. [Example]

[0048] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to the descriptions of these examples.

[0049] 1.Various measurement methods [Viscosity increase rate after 90 minutes at 25°C] 5 g of the epoxy mixture was weighed and placed in a measuring jig (parallel plate), and complex viscosity measurements were performed using a DMA device (model: ARES-G2 manufactured by TA Instruments) at 25°C for 90 minutes under a measurement strain of 30% and a frequency of 0.5 kH. Here, the viscosity after 5 minutes at 25°C was defined as the initial viscosity, and the viscosity increase ratio was the percentage increase in viscosity after 90 minutes at 25°C relative to the initial viscosity.

[0050] [Volumetric expansion rate] Take a 30 g sample of the epoxy mixture, transfer it to a test tube, and measure it on a hydrometer (measurement range: 1.000-1.500 g / cm). 3 ) was used to measure the density when the temperature was adjusted to 25°C and 80°C in a water bath, and the volume change rate when the temperature was increased from 25°C to 80°C was calculated to obtain the volume expansion rate.

[0051] 2. Evaluation method for pultrusion formability The following items were set as evaluation indices for pultrusion formability, and a simple evaluation was carried out.

[0052] [Pull-out force] Pultrusion molded products were manufactured using the manufacturing process shown in Figure 1. A load cell was installed under mold 8, and the pull-out force 1 hour after the start of molding was measured for 10 minutes using a data logger (sampling rate 100 ms). The average pull-out force during the sampling period was used.

[0053] [Appearance of molded product] The appearance of the molded product obtained by the manufacturing process shown in Figure 1 was judged according to the following criteria. A: Good appearance of molded product B: There are scratches on the surface of the molded product. C: There are chips on the edge of the molded product or scratches on the surface. 3. Evaluation method for pultrusion molded products [CF volume content (Vf)] After measuring the mass W0 of the pultrusion molded product, the pultrusion molded product was heated in air at 550 ° C for 240 minutes to burn off the resin component, the mass W1 of the remaining reinforcing fibers was measured, and the CF volume content (Vf) of the pultrusion molded product was calculated using the following formula. Vf (volume%) = (W1 / ρf) / {W1 / ρf+(W0-W1) / ρ1}×100 ρf: Density of reinforcing fiber (g / cm 3 ) [Arithmetic mean roughness Ra] The surface condition of the pultrusion molded product was measured using a surface roughness measuring device (model: Surfcom 1800G / manufactured by Tokyo Seimitsu Co., Ltd.) by scanning 50 mm in the longitudinal direction of the CF, and the arithmetic mean roughness Ra was measured with N = 3. [Mold shrinkage rate] The dimensions of the width direction (TD direction) and thickness direction of the pultrusion molded product were measured at three points each with a micrometer, and the average values ​​were calculated. In order to quantify the degree of shrinkage of the actual dimensions relative to the product dimensions (width, thickness) in the pultrusion mold, the molding shrinkage rate was calculated using the following method. Mold shrinkage rate (%) = (measured dimensions of pultrusion molded product - product dimensions in the pultrusion mold) / (product dimensions in the pultrusion mold) x 100 [Mechanical property evaluation] (1) Bending test (0° direction: reinforcing fiber bundle direction in plan view) The pultrusion molded product was cut with an autocutter to a width of 15 mm, length of 250 mm, and thickness of 5 mm, with the 0° direction as the longitudinal direction, to obtain a 0° bending test piece. Next, a bending test was performed with N=5 using an Instron 5565 device in a three-point bending mode (indenter diameter: upper φ10, lower φ4) with a crosshead speed of 12 mm / min and a span distance of 190 mm.

[0054] 4. Manufacturing method of pultrusion molded products [Raw materials] (1) Epoxy base / component (B) <Bisphenol A type> "Araldite (registered trademark)" LY3585 (manufactured by Huntsman) "jER (registered trademark)" 828 (Mitsubishi Chemical Corporation) <Bisphenol F type> "EPICLON (registered trademark)" 830 (DIC Corporation) (2) Epoxy base / component (C) <Aminophenol type> "JER (registered trademark)" 630 (Mitsubishi Chemical Corporation) "Araldite (registered trademark)" MY0600 (manufactured by Huntsman) "Araldite (registered trademark)" MY0510 (manufactured by Huntsman) <Novolac phenol type> "JER (registered trademark)" 154 (Mitsubishi Chemical Corporation) <Aliphatic ether type> "Denacol (registered trademark)" EX-810 (manufactured by Nagase Chemtec Corporation) "Denacol (registered trademark)" EX-321L (manufactured by Nagase Chemtec Corporation) "Denacol (registered trademark)" EX-212 (manufactured by Nagase Chemtec Corporation) Denacol (registered trademark) EX-614B (manufactured by Nagase Chemtec Corporation) "ADEKA Glycirol (registered trademark)" ED-503 (manufactured by ADEKA Corporation) (3) Hardener / Component (D) <Cyanamide type> "DICY7T" (Mitsubishi Chemical) "Diehard (registered trademark)" Fluid111 (manufactured by AlzChem) <Alicyclic amine type> "VESTAMIN (registered trademark)" IPD (manufactured by Evonik Japan Co., Ltd.) "Baxxodur (registered trademark)" EC331 (manufactured by BASF) "ARADUR (registered trademark)" 3474 (Huntsman) (4) Curing agents other than component (D) <Acid anhydride type> "ARADUR (registered trademark)" 917-1 (Huntsman) (5) Curing accelerator <Aromatic urea> "Omicure (registered trademark)" 24 (PTI Japan Co., Ltd.) <Imidazole> Accelerator (registered trademark) DY080 (Huntsman) (6) Thermosetting and thermoplastic resins other than epoxy <Vinyl ester> Base resin: Bisphenol A vinyl ester resin, DIC pultrusion grade, "EPICLON UE-3505" (registered trademark) Initiator 1: t-butylperoxy-2-ethylhexanoate, a radical initiator manufactured by Nouryon Chemical Industries, Ltd., "Trigonox 21-50E (registered trademark)" Initiator 2: t-butyl peroxybenzoate, a radical initiator manufactured by Nouryon Chemical Industries, Ltd., "Trigonox C (registered trademark)" <Polymethyl methacrylate (PMMA)> Main component: MMA monomer, Arkema pultrusion grade, "EliumC595-E (registered trademark)" Initiator 1: Di(4-butylcyclohexyl) peroxydicarbonate, a radical initiator manufactured by Nouryon Chemical Industries, Ltd., "Perkadox 16 (registered trademark)" Initiator 2: t-butyl peroxybenzoate, a radical initiator manufactured by Nouryon Chemical Industries, Ltd., "Trigonox C (registered trademark)" <Polyurethane> Main ingredient: DESMOCOMP (registered trademark) Ultra AP-200 (manufactured by Sumika Covestro) Catalyst: "DESMORAPT™ AP-100 (manufactured by Sumika Covestro) (7) Carbon fiber "TORAYCA (registered trademark)" T700S-24K (24,000 filaments, manufactured by Toray Industries, Inc.) [Resin preparation method and pultrusion molding trial production] The raw materials (main agent, curing agent, curing accelerator, etc.) shown in Tables 1 to 3 were charged into a 5 L disposable cup container in the prescribed blending ratio, and stirred with a stainless steel stirring blade at 700 rpm for 60 minutes.

[0055] Pultrusion molded articles were produced using the resin composition prepared in this manner using the manufacturing process shown in Figure 1. A pultrusion mold measuring 50 mm wide, 750 mm long, and 5.2 mm thick was used, and a carbon fiber bobbin was set on creel 3 (Figure 1) so that the carbon fiber content (volume content: Vf) was 62%. As shown in Figure 1, the resin composition was placed in resin bath 4, temperature-controlled at 25°C, and carbon fiber bundles (continuous reinforcing fiber bundles 2) were passed through it to be impregnated with the resin. Next, the resin-impregnated fiber substrate, from which excess resin was squeezed out as it passed through squeeze bars 5 and 6, was introduced through the inlet of mold 7 and continuously cured. Pultrusion molded articles 9 emerging from the outlet of mold 7 were collected in coil form on winding device 10 at a take-up speed of 0.3 m / min using puller 8. The mold temperature was set as follows depending on the resin type of the resin composition: Epoxy: mold entrance 120℃, mold center 160℃, mold exit 150℃ Vinylester: mold entrance 120℃, mold center 160℃, mold exit 150℃ Polyurethane: mold entrance 120℃, mold center 160℃, mold exit 150℃ PMMA: mold entrance 90℃, mold center 110℃, mold exit 100℃

[0056] [Table 1]

[0057] [Table 2]

[0058] [Table 3] [Explanation of symbols]

[0059] 1. Pultrusion molding manufacturing process 2 Continuous reinforcing fiber bundles 3 Creel 4 Resin Bath 5, 6 Squeeze bar 7 Pultrusion mold 8 Puller 9 Pultrusion products 10 Winding device 11 Epoxy Resin

Claims

1. A method for producing a pultruded article comprising curing a material comprising components (A) through (D) and satisfying conditions (I) and (II). [component] (A) Carbon fiber (B) an epoxy base resin selected from bisphenol A type and bisphenol F type (C) an epoxy base resin selected from aminophenol type, novolac type, and aliphatic ether type (D) One or more epoxy curing agents selected from cyanamide type and alicyclic amine type [conditions] (I) The volume expansion coefficient V when the mixture of (B) and (C) is heated from 25°C to 80°C ８０ / V ２５ satisfies the following relational expression (1): [Equation 1] V ８０ : Density (g / cm) of a mixture of component (B) and component (C) at 80 ° C. ３ ) V ２５ : Density (g / cm) of a mixture of component (B) and component (C) at 25°C ３ ) (II) The viscosity increase ratio of a mixture of (B), (C) and (D) after 90 minutes at 25°C is 1.80 times or less.

2. 2. The method for producing a pultrusion molded product according to claim 1, wherein component (C) is an aminophenol-type epoxy base resin, and component (D) is a cyanamide-type epoxy curing agent.

3. 2. The method for producing a pultrusion molded product according to claim 1, wherein component (C) is an aliphatic ether-type epoxy base resin, and component (D) is a cyanamide-type epoxy curing agent.

4. A method for manufacturing a wind turbine blade, comprising using a pultrusion molded product manufactured by the manufacturing method according to any one of claims 1 to 3 as a spar cap.

5. A pultrusion molded article obtained by curing a material containing components (A) to (D) and satisfying conditions (I) and (II). [component] (A) Carbon fiber (B) an epoxy base resin selected from bisphenol A type and bisphenol F type (C) an epoxy base resin selected from aminophenol type, novolac type, and aliphatic ether type (D) One or more epoxy curing agents selected from cyanamide type and alicyclic amine type [conditions] (I) The volume expansion coefficient V when the mixture of (B) and (C) is heated from 25°C to 80°C ８０ / V ２５ satisfies the following relational expression (1): [Equation 2] V ８０ : Density (g / cm) of a mixture of component (B) and component (C) at 80 ° C. ３ ) V ２５ : Density (g / cm) of a mixture of component (B) and component (C) at 25°C ３ ) (II) The viscosity increase ratio of a mixture of (B), (C) and (D) after 90 minutes at 25°C is 1.80 times or less.

6. A wind turbine blade using the pultrusion product according to claim 5 as a spar cap.

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