NZ624037B2 - Improvements in or relating to fibre reinforced composites - Google Patents

Improvements in or relating to fibre reinforced composites Download PDF

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Publication number
NZ624037B2
NZ624037B2 NZ624037A NZ62403712A NZ624037B2 NZ 624037 B2 NZ624037 B2 NZ 624037B2 NZ 624037 A NZ624037 A NZ 624037A NZ 62403712 A NZ62403712 A NZ 62403712A NZ 624037 B2 NZ624037 B2 NZ 624037B2
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NZ
New Zealand
Prior art keywords
resin
stack
prepreg
prepregs
epoxy resin
Prior art date
Application number
NZ624037A
Other versions
NZ624037A (en
Inventor
Thorsten Ganglberger
Wilhelm Pointer
Original Assignee
Hexcel Holding Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hexcel Holding Gmbh filed Critical Hexcel Holding Gmbh
Priority claimed from PCT/EP2012/076780 external-priority patent/WO2013093065A1/en
Publication of NZ624037A publication Critical patent/NZ624037A/en
Publication of NZ624037B2 publication Critical patent/NZ624037B2/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
    • B29D99/00—Subject matter not provided for in other groups of this subclass
    • B29D99/0025—Producing blades or the like, e.g. blades for turbines, propellers, or wings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B17/00—Layered products essentially comprising sheet glass, or glass, slag, or like fibres
    • B32B17/06—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material
    • B32B17/10—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin
    • B32B17/10005—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing
    • B32B17/1055—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer
    • B32B17/10733—Layered products essentially comprising sheet glass, or glass, slag, or like fibres comprising glass as the main or only constituent of a layer, next to another layer of a specific material of synthetic resin laminated safety glass or glazing characterized by the resin layer, i.e. interlayer containing epoxy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/02—2 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/20—All layers being fibrous or filamentary
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/24—All layers being polymeric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B32B2260/02—Composition of the impregnated, bonded or embedded layer
    • B32B2260/021—Fibrous or filamentary layer
    • B32B2260/023—Two or more layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B32B2260/04—Impregnation, embedding, or binder material
    • B32B2260/046—Synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/10—Inorganic fibres
    • B32B2262/101—Glass fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/07—Parts immersed or impregnated in a matrix
    • B32B2305/076—Prepregs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/08—Reinforcements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/77—Uncured, e.g. green
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2315/00—Other materials containing non-metallic inorganic compounds not provided for in groups B32B2311/00 - B32B2313/04
    • B32B2315/08—Glass
    • B32B2315/085—Glass fiber cloth or fabric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2363/00—Epoxy resins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2603/00—Vanes, blades, propellers, rotors with blades
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/38—Layered products comprising a layer of synthetic resin comprising epoxy resins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/06—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the heating method
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/16—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with all layers existing as coherent layers before laminating
    • B32B37/18—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with all layers existing as coherent layers before laminating involving the assembly of discrete sheets or panels only
    • B32B37/182—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with all layers existing as coherent layers before laminating involving the assembly of discrete sheets or panels only one or more of the layers being plastic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/022—Non-woven fabric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/12—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer characterised by the relative arrangement of fibres or filaments of different layers, e.g. the fibres or filaments being parallel or perpendicular to each other
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B32B5/24—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
    • B32B5/28—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer impregnated with or embedded in a plastic substance
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
    • C08G59/4007—Curing agents not provided for by the groups C08G59/42 - C08G59/66
    • C08G59/4014—Nitrogen containing compounds
    • C08G59/4021—Ureas; Thioureas; Guanidines; Dicyandiamides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2363/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
    • C08J5/0405—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres
    • C08J5/042—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres with carbon fibres
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
    • C08J5/0405—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres
    • C08J5/043—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres with glass fibres
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
    • C08J7/02—Chemical treatment or coating of shaped articles made of macromolecular substances with solvents, e.g. swelling agents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M15/00—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment
    • D06M15/19—Treating fibres, threads, yarns, fabrics, or fibrous goods made from such materials, with macromolecular compounds; Such treatment combined with mechanical treatment with synthetic macromolecular compounds
    • D06M15/37—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
    • D06M15/55—Epoxy resins
    • D—TEXTILES; PAPER
    • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
    • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
    • D06M2101/00—Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03D—WIND MOTORS
    • F03D1/00—Wind motors with rotation axis substantially parallel to the air flow entering the rotor 
    • F03D1/06—Rotors
    • F03D1/065—Rotors characterised by their construction elements
    • F03D1/0675—Rotors characterised by their construction elements of the blades
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/72—Wind turbines with rotation axis in wind direction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
    • Y10T442/20—Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
    • Y10T442/2926—Coated or impregnated inorganic fiber fabric
    • Y10T442/2951—Coating or impregnation contains epoxy polymer or copolymer or polyether
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
    • Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
    • Y10T442/643—Including parallel strand or fiber material within the nonwoven fabric
    • Y10T442/644—Parallel strand or fiber material is glass

Abstract

Prepregs and stacks of prepregs based on reactive epoxy resins that can be cured at lower externally applied temperatures such as from 70°C to 110°C with acceptably short cycle times comprise epoxy resins of epoxy equivalent weight from 200 to 500 containing a curing agent but no hardener.

Description

IMPROVEMENTS IN OR RELATING TO FIBRE REINFORCED COMPOSITES The present invention relates to the production of laminar structures by laying up a stack of layers of e structures in a mould and causing the stack of structures to cure. The invention is particularly concerned with the production of resin based fibre reinforced structures from fibre impregnated with a curable resin such an epoxy resin. Such layers of curable structures in which the resin is uncured are sometimes known as prepregs. In one embodiment the invention is concerned with the production of wind turbine structures, such as shells for the blades of the turbine and spars that support the blades.
The present invention therefore relates to fibre reinforced materials and in particular to prepregs comprising fibres and thermosetting resins which may be stacked to form a preform and subsequently cured to form a reinforced composite material. Such composite materials are known, they are lightweight and of high strength and are used in many structural applications such as in the automobile and aerospace industries and in industrial applications such as wind turbine components such as spars and the shells used to make the blades. g is the term used to describe fibres and fabric impregnated or in combination with a resin in the uncured state and ready for curing. The fibres may be in the form of tows or fabrics and a tow generally comprise a plurality of thin fibres. The fibrous materials and resins employed in the prepregs will depend upon the properties required of the cured fibre reinforced material and also the use to which the cured laminate is to be put. The fibrous material is bed herein as ural fibre. The resin may be combined with fibres or fabric in various ways. The resin may be tacked to the surface of the s material. The resin may partially or tely impregnate the fibrous material. The resin may impregnate the s material so as to provide a y to facilitate the l of air or gas during processing of the prepreg al.
Various methods have been proposed for the production of prepregs, one of the preferred methods being the impregnation of a moving fibrous web with a liquid, molten or semi-solid d thermosetting resin. The prepreg produced by this method may then be cut into sections of the desired length and a stack of the sections cured by g to produce the final fibre reinforced laminate. Curing may be performed in a vacuum bag which may be placed in a mould for curing as is red in the manufacture of wind energy structures such as shells for the blades and spars. atively, the stack may be formed and cured directly in a mould.
One red family of resins for use in such applications are curable epoxy resins and curing agents and curing agent accelerators are usually included in the resin to shorten the cure cycle time. Epoxy resins are highly suitable resins although they can be e after cure causing the final laminate to crack or fracture upon impact and it is therefore common practice to e toughening materials such as thermoplastics or rubbers in the epoxy resin.
The cure cycles employed for curing prepregs and stacks of prepregs are a balance of temperature and time taking into account the reactivity of the resin and the amount of resin and fibre employed. From an ic point of view it is desirable that the cycle time be as short as possible and so curing agents and accelerators are usually included in the epoxy resin. As well as requiring heat to te curing of the resin the curing reaction itself can be highly exothermic and this needs to be taken into account in the time/temperature curing cycle in particular for the curing of large and thick stacks of prepregs as is increasingly the case with the production of laminates for industrial application where large amounts of epoxy resin are employed and high atures can be generated within the stack due to the exotherm of the resin curing reaction. Excessive temperatures are to be avoided as they can damage the mould reinforcement or cause some osition of the resin. Excessive temperatures can also cause loss of control over the cure of the resin leading to run away cure.
Generation of excessive temperatures can be a greater problem when thick sections comprising many layers of prepreg are to be cured as is becoming more prevalent in the production of fibre reinforced laminates for heavy industrial use such as in the tion of wind turbine structures particularly wind turbine spars and shells from which the blades are assembled. In order to sate for the heat generated during curing it has been necessary to employ a dwell time during the curing cycle in which the moulding is held at a constant temperature for a period of time to control the temperature of the moulding and is cooled to prevent overheating this increases cycle time to undesirably long cycle times of several hours in some instances more than eight hours.
For example a thick stack of epoxy based prepregs such as 60 or more layers can require cure temperatures above 100°C for several hours. However, the cure can have a reaction enthalpy of 150 joules per gram of epoxy resin or more and this reaction py brings the need for a dwell time during the cure cycle at below 100°C to avoid overheating and decomposition of the resin. Furthermore, following the dwell time it is necessary to heat the stack further to above 100°C (for example to above 125°C) to complete the cure of the resin. This leads to undesirably long and uneconomic cure cycles. In addition, the high temperatures generated can cause damage to the mould or bag materials or require the use of l and costly als for the moulds or bags.
In addition to these problems there is a desire to produce laminar structures from prepregs in which the cured resin has a high glass tion temperatures (Tg) such as above 80°C to extend the ness of the structures by improving their resistance to exposure at high atures and/or high ty for extended s of time which can cause an undesirable lowering of the Tg. For wind energy structures a Tg above 90°C is red. Increase in the Tg may be achieved by using a more reactive resin. However the higher the reactivity of the resin the greater the heat released during curing of the resin in the presence of hardeners and accelerators which increases the attendant problems as previously described.
PCT publication WO2011/0731 1 1 is concerned with the provision of a prepreg that, inter alia, can be cured quickly without a damaging exotherm event. The solution provided by WO2011/0731 1 1 is to employ a resin which contains an unsaturated monomer capable of free radical polymerisation and also a curable functionality such as epoxy groups. The chemistry is complex and ive and furthermore requires the ce of peroxide initiators in the resin system to polymerise the unsaturated monomers during cure of the resin.
The present invention aims to overcome the aforesaid problems and/or to provide improvements generally.
According to the invention, there is provided a prepreg, a stack, a laminate, a use, a process, a resin matrix and a wind turbine blade or ent as defined in any one of the accompanying .
According to a first aspect, there is provided a prepreg comprising a mixture of a fibrous reinforcement and an epoxy resin containing from 20% to 85% by weight of an epoxy resin of epoxy equivalent weight (EEW) from 150 to 1500 said resin comprising from 0.5 to 10 wt% based on the weight of the epoxy resin of a urea based curing agent and being free of dicyandiamide, said resin further being curable by an externally applied temperature in the range of 70°C to 110°C.
According to a second aspect, there is provided a stack of prepregs containing an epoxy resin of epoxy equivalent weight (EEW) from 150 to 1500 the resin comprising (11127107_1):RTK from 0.5 to 10 wt% based on the weight of the epoxy resin of a urea based curing agent and being free of dicyandiamide, said resin further being curable by an externally applied temperature in the range of 70°C to 110°C, the stack of prepregs containing at least 2 or more prepreg . ing to a third aspect, there is provided a curable stack of prepregs, at least one of said prepregs comprising a structural fibrous layer impregnated with an epoxy resin the epoxy resin having an epoxy equivalent weight (EEW) of from 150 to 1500 said resin comprising from 0.5 to 10 wt% based on the weight of the epoxy resin of a urea based curing agent and being free of dicyandiamide, said resin further being e at a temperature in the range of 70°C to 110°C.
According to a fourth aspect, there is provided a laminate comprising a cured prepreg or stack of prepregs according to any one of the first to third aspects.
According to a fifth aspect, there is provided use of a prepreg or a stack of gs ing to any one of the first to third aspects for the production of wind turbine ures.
According to a sixth aspect, there is provided a process of curing the epoxy resin within a prepreg or prepreg stack according to any one of the first to third aspects, the process involving exposing the prepreg or prepreg stack to an externally applied temperature in the range 70°C to 110°C for up to 8 hours at a pressure of less than 3.0 bar absolute.
According to a seventh aspect, there is ed a process for the production of wind turbine structures comprising providing a prepreg or stack of prepregs comprising a mixture of s rcement and from 20 % to 85 wt % of an epoxy resin of epoxy equivalent weight (EEW) 150 to 1500 and containing from 0.5 to 10 wt % based on the weight of the epoxy resin of a urea based curing agent and being free of dicyandiamide within a vacuum bag, placing the vacuum bag within a mould and creating a vacuum within the bag prior to or after placement in the mould and curing the epoxy resin by application of an externally applied temperature in the range 70°C to 110°C for a period of from 4 to 8 hours.
According to an eighth , there is provided a resin matrix comprising an epoxy resin containing from 20% to 85% by weight of an epoxy resin of epoxy equivalent weight (EEW) from 150 to 1500 said resin being curable by an externally applied temperature in the range of 70°C to 110°C, the resin containing from 0.5 to 5 wt % of a urea based curing agent, and being free of dicyandiamide. (11127107_1):RTK According to a ninth aspect, there is provided a wind turbine blade or component produced from a resin matrix as defined in the eighth aspect in combination with a fibrous reinforcement.
The reactivity of an epoxy resin is indicated by its epoxy equivalent weight (EEW) the lower the EEW the higher the reactivity. The epoxy equivalent weight can be calculated as follows: ular weight epoxy resin)/ (Number of epoxy groups per le). Another way is to calculate with epoxy number that can be defined as follows: Epoxy number = 100 / epoxy eq.weight. To calculate epoxy groups per le : (Epoxy number x mol.weight) / 100. To calculate ight : (100 x epoxy groups per molecule) / epoxy number. To calculate mol.weight: epoxy eq.weight x epoxy groups per molecule. The present invention (11127107_1):RTK is particularly concerned with providing a g that can be based on a reactive epoxy resin that can be cured at a lower temperature with an acceptable moulding cycle time.
The present invention therefore es a prepreg comprising a mixture of a fibrous reinforcement and an epoxy resin containing from 20% to 85% by weight of an epoxy resin of EEW from 150 to 1500 said resin being curable by an externally d ature in the range of 70°C to 110°C.
In an embodiment of the present ion therefore provides a prepreg comprising a mixture of a fibrous reinforcement and an epoxy resin containing from 20% to 85% by weight of an epoxy resin of EEW from 150 to 1500 said resin being curable by an externally applied temperature in the range of 70°C to 110°C, wherein the resin contains from 0.5 to 5 wt% of a urea curing agent, and the resin is cured in the absence of a dicyandiamide based hardener.
We have found that prepreg and its epoxy resin matrix has a reduced cure time, whilst providing good mechanical performance, a ble Tg (glass transition temperature) and good mechanical performance in combination with the fibrous reinforcement of the prepreg.
The invention further provides a stack of prepregs ning an epoxy resin of EEW from 150 to 1500 preferably from 200 to 500 the resin being curable by an externally applied temperature in the range of 70°C to 110°C and containing 40 or more prepreg layers, typically 60 or more layers the stack being of a thickness of at least 35mm.
The invention further provides such a prepreg and stacks of prepregs that can be cured in less than ten hours particularly less than eight hours. In a preferred embodiment the curing resin has a dynamic enthalpy of 150 joules per gram of epoxy resin or lower.
We have found that such ble prepregs and stacks of prepregs may be ed using conventionally available epoxy resins if the epoxy resin is cured in the absence of a traditional hardener such as dicyandiamide and in particular we have found that these desirable prepregs can be obtained by use of a urea based curing agent in the absence of a hardener such as diamide. The relative amount of the curing agent and the epoxy resin that should be used will depend upon the reactivity of the resin and the nature and quantity of the fibre reinforcement in the prepreg. Typically from 0.5 to 10 wt % of the urea based curing agent based on the weight of epoxy resin is used.
The prepregs of this invention are lly used at a different location from where they are manufactured and they therefore require handleability. It is therefore preferred that they are dry or as dry as possible and have low surface tack. It is ore preferred to use high viscosity resins. This also has the benefit that the impregnation of the fibrous layer is slow allowing air to escape and to minimise void formation.
In order to produce final tes with substantially uniform mechanical properties it is ant that the structural fibres and the epoxy resin be mixed to provide a substantially homogenous prepreg. This requires m distribution of the structural fibres within the prepreg to provide a ntially continuous matrix of the resin surrounding the fibres. It is therefore important to minimise the encapsulation of air bubbles within the resin during application to the fibres. It is therefore preferred to use high viscosity resins. The prepregs should contain a low level of voids in order and it is ore preferred that each prepreg and the prepreg stack has a water pick-up value of less than 25%, more preferably less than 15%, more preferably less than 9%, most ably less than 3%. The water pick-up test determines the degree of waterproofing or impregnation of prepregs. For this purpose, a specimen of prepreg material is initially d and clamped between two plates in such a way that a strip of specimen 5 mm wide protrudes. This arrangement is suspended in the ion of the fibres in a water bath for 5 minutes at room temperature (21 °C). After removing the plates, the specimen is again weighed. The ence in weight is used as a measured value for the degree of nation. The smaller the amount of water picked up, the higher the degree of waterproofing or impregnation.
The prepregs of this invention are intended to be laid-up with other composite materials (e.g. other prepregs according to the invention or other prepregs) to produce a prepreg stack which can be cured to produce a fibre reinforced laminate.
The prepreg is typically produced as a roll of prepreg and in view of the tacky nature of such materials, a g sheet is generally provided to enable the roll to be unfurled at the point of use. Thus, preferably the prepreg according to the invention comprises a g sheet on an external face.
The epoxy resin has a high reactivity as indicated by an EEW in the range from 150 to 1500 preferably a high reactivity such as an EEW in the range of from 200 to 500 and the resin composition comprises the resin and an accelerator or curing agent. Suitable epoxy resins may comprise blends of two or more epoxy resins selected from monofunctional, difunctional, trifunctional and/or tetrafunctional epoxy resins.
Suitable difunctional epoxy resins, by way of example, include those based on: diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A (optionally brominated), phenol and cresol epoxy novolacs, glycidyl ethers of phenol-aldelyde adducts, glycidyl ethers of aliphatic diols, diglycidyl ether, lene glycol diglycidyl ether, aromatic epoxy , aliphatic polyglycidyl ethers, epoxidised s, brominated resins, aromatic glycidyl amines, heterocyclic glycidyl es and amides, glycidyl ethers, nated epoxy resins, glycidyl esters or any combination thereof.
Difunctional epoxy resins may be selected from diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol A, diglycidyl dihydroxy naphthalene, or any combination thereof.
Suitable ctional epoxy resins, by way of example, may e those based upon phenol and cresol epoxy novolacs, glycidyl ethers of phenol-aldehyde adducts, aromatic epoxy resins, aliphatic triglycidyl ethers, dialiphatic triglycidyl ethers, aliphatic polyglycidyl amines, heterocyclic glycidyl imidines and amides, yl ethers, fluorinated epoxy resins, or any combination f. Suitable trifunctional epoxy resins are available from Huntsman Advanced Materials (Monthey, Switzerland) under the tradenames MY0500 and MY0510 (triglycidyl para-aminophenol) and MY0600 and MY0610 (triglycidyl meta-aminophenol). cidyl meta-aminophenol is also available from Sumitomo Chemical Co. (Osaka, Japan) under the tradename ELM-120.
Suitable unctional epoxy resins include N,N, N’,N’-tetraglycidyl-m-xylenediamine (available commercially from Mitsubishi Gas Chemical Company under the name Tetrad-X, and as Erisys GA—240 from CVC Chemicals), and N,N,N’,N’-tetrag|ycidylmethylenedianiline (e.g. MY0720 and MY0721 from Huntsman Advanced Materials). Other suitable multifunctional epoxy resins include DEN438 (from Dow Chemicals, Midland, MI) DEN439 (from Dow Chemicals), Araldite ECN 1273 (from Huntsman Advanced Materials), and Araldite ECN 1299 (from Huntsman Advanced Materials).
The epoxy resin composition also comprises one or more urea based curing agents and it is preferred to use from 0.5 to 10 wt % based on the weight of the epoxy resin of a curing agent, more preferably 1 to 8 wt %, more preferably 2 to 8 wt %, more preferably 0.5 to 5 wt %, more ably 0.5 to 4 wt % inclusive, or most preferably 1.3 to 4 wt % inclusive.
The urea curing agent may comprise a bis urea curing agent, such as 2,4 toluene bis dimethyl urea or 2,6 toluene bis dimethyl urea and/or ations of the aforesaid curing agents. Urea based curing agents may also be referred to as s”.
Other suitable urea based curing agents may comprise: H3C\ (a H /CH3 NiCiNH CH2 NH7C7N\ H3C/ CH3 4,4-methylene diphenylene bis(N,N-dimethy| urea) (‘3‘ CH3 CIQNHCNi 1,1-dimethyl, 3-(4-chloropheny|)urea (‘3‘ CH3 C1 NHiCib‘I 1,1-dimethyl, 3-(3,4-dichlorophenyl)urea H /CH3 H3C NH7C7N\ /CH3 H3C NH7C7N\ (‘3‘ CH3 |sophorone bisdimethyl urea (3 CH3 1,1-dimethyl, 3-phenyl urea (H CH3 H3CH2COQNHCN\ 1,1-dimethyl, 3-(4-ethoxyphenyl)urea H3C\ (3 /CH3 /N*C*HN NH*C*N\ H3C (‘3‘ CH3 1,1-(4-pheny|ene)—bis(3,3-dimethy|)urea (3 CH3 NHiCilrl methyl, 3-(2—hydroxyphenyl)urea (3 CH3 H3C NHiCilrl 1,1-dimethyl,3-(3-ch|oromethy|pheny|)urea OYNHz N-Phenylurea H3C\ o H3C NH2 N,N-Dimethylurea NH N(CH3)2 Fluomethuron Preferred urea based materials are the range of materials available under the commercial name DYHARD® the trademark of Alzchem, urea derivatives, which include bis ureas such as UR500 and UR505.
The structural fibres employed in the prepregs or prepreg stacks of this invention may be tows or fabrics and may be in the form of random, knitted, non-woven, multi-axial or any other suitable pattern. For structural applications, it is generally preferred that the fibres be unidirectional in orientation. When unidirectional fibre layers are used, the orientation of the fibre can vary throughout the g stack. r, this is only one of many possible orientations for stacks of unidirectional fibre layers. For example, unidirectional fibres in neighbouring layers may be ed orthogonal to each other in a so-called 0/90 arrangement, which signifies the angles between neighbouring fibre layers. Other arrangements, such as 0/+45/—45/90 are of course possible, among many other arrangements.
The ural fibres may comprise cracked (i.e. stretch-broken), ively discontinuous or continuous fibres. The structural fibres may be made from a wide variety of materials, such as , graphite, glass, metalized polymers, aramid and mixtures thereof. Glass and carbon fibres are preferred carbon fibre, being preferred for wind e shells of length above 40 metres such as from 50 to 60 . The structural fibres, may be individual tows made up of a multiplicity of individual fibres and they may be woven or non-woven fabrics.
The fibres may be unidirectional, bidirectional or multidirectional according to the properties required in the final laminate. Typically the fibres will have a ar or almost circular cross- 2012/076780 section with a diameter in the range of from 3 to 20 um, preferably from 5 to 12 um.
Different fibres may be used in different gs used to produce a cured laminate.
Exemplary layers of ectional structural fibres are made from HexTow® carbon fibres, which are available from Hexcel Corporation. Suitable HexTow® carbon fibres for use in making unidirectional fibre layers include: |M7 carbon fibres, which are available as fibres that contain 6,000 or 12,000 filaments and weight 0.223 g/m and 0.446 g/m tively; lM8-IM10 carbon fibres, which are available as fibres that contain 12,000 filaments and weigh from 0.446 g/m to 0.324 g/m; and AS7 carbon fibres, which are available in fibres that contain 12,000 filaments and weigh 0.800 g/m.
The structural fibres of the prepregs will be substantially impregnated with the epoxy resin and prepregs with a resin content of from 20 to 85 wt % of the total prepreg weight are preferred. The prepregs of the present invention are predominantly composed of resin and structural fibres.
The stacks of prepregs of this invention may n more than 40 layers, lly more than 60 layers and at times more than 80 layers. Typically the stack will have a thickness of from 35 to 100mm.
Epoxy resins can become brittle upon curing and toughening materials can be included with the resin to impart durability, although they may result in an undesirable increase in the viscosity of the resin. The toughening material may be supplied as a separate layer such as a veil.
Where the additional toughening material is a polymer it should be insoluble in the matrix epoxy resin at room temperature and at the elevated atures at which the resin is cured. Depending upon the melting point of the thermoplastic r, it may melt or soften to varying degrees during curing of the resin at elevated temperatures and re-solidify as the cured laminate is cooled. Suitable thermoplastics should not ve in the resin, and include thermoplastics, such as ides (PAS), polyethersulfone (PES) and polyetherimide (PEI). Polyamides such as nylon 6 (PA6), nylon 11 (PA11) or nylon 12 (PA12), and/or mixtures thereof are preferred.
In an embodiment of the invention, there is provided a prepreg sing a resin system comprising an epoxy resin containing from 20%to 85% by weight of an epoxy of EEW from 150 to1500, and 0.5 to 10 wt% of a curing agent, the resin system comprising an onset temperature in the range of from 115 to 125 0C, and/or a peak ature in the range of from 140 to 150 0C, and/or an enthalpy in the range of from 80 to 120 J/g (Tonset, Tpeak, Enthalpy measured by DSC (=differential scanning calorimetry) in ance with ISO 11357, over temperatures of from -40 to 270°C at 10 °C/min). Tonset is defined as the onset- temperature at which curing of the resin occurs during the DSC scan, whilst Tpeak is defined as the peak temperature during curing of the resin during th scan.
The resin system is particularly suitable for g applications at which a desired cure temperature is below 100°C. The resin system may be processed to cure over a wide sing temperature range, ranging from 75°C up to 120°C. Due to its low exothermic properties M79 can be used for large industrial components, suitable for the cure of thin and thick sections. It demonstrates a good static and dynamic mechanical performance following cure temperatures <100°C.
As discussed, the resin system can be pre-impregnated into carbon, glass or aramid fiber reinforcement materials and exhibits a significant long out-life at room temperature (greater than 6 weeks at 23°C). Other benefits of the resin system include: ent tack life, low exothermic properties, well adapted to low re processing, suitable for a range of processing pressures (0.3 to 5 bar) which enable both vacuum bag and autoclave cure applications, good flexibility and handleability of g, suitable for thin and thick laminates, good quality surface finish, ent fatigue mance and translucent resin after cure.
The prepregs of this invention are produced by impregnating the fibrous material with the epoxy resin. In order to increase the rate of impregnation, the process is preferably carried out at an elevated temperature so that the viscosity of the resin in reduced. However it must not be so hot for sufficient length of time that premature curing of the resin occurs. Thus, the impregnation process is preferably carried out at temperatures in the range of from 40°C to 80°C.
The resin composition can be spread onto the external surface of a roller and coated onto a paper or other g material to produce a layer of curable resin. The resin composition can then be t into contact with the s layer for impregnation perhaps by the passage through rollers. The resin may be present on one or two sheets of backing material, which are brought into contact with the structural fibrous layer and by passing them through heated consolidation rollers to cause impregnation. Alternatively the resin can be maintained in liquid form in a resin bath either being a resin that is liquid at ambient 2012/076780 temperature or being molten if it is a resin that is solid or semi solid at ambient temperature.
The liquid resin can then be applied to a g employing a doctor blade to produce a resin film on a release layer such as paper or polyethylene film. The structural fibrous layer may then be placed into the resin and optionally a second resin layer may be provided on top of the fibrous layer.
A backing sheet can be applied either before or after impregnation of the resin. However, it is typically applied before or during impregnation as it can provide a non-stick surface upon which to apply the pressure required for causing the resin to impregnate the fibrous layer.
Once prepared the prepreg may be rolled-up, so that it can be stored for a period of time. It can then be unrolled and cut as desired and optionally laid up with other prepregs to form a prepreg stack in a mould or in a vacuum bag which is subsequently placed in a mould.
Once it is created in the mould the prepreg or prepreg stack may be cured by exposure to an externally applied elevated temperature in the range 70°C to 110°C, and optionally elevated pressure, to produce a cured laminate.
The exotherm due to the curing of the g stack may take the temperatures within the stack to above 110°C, however we have found that if the externally applied ature is within the range of 70°C to 110°C, curing of a prepreg or stack of prepregs based on an epoxy resin of EEW from 150 to 1500 particularly of EEW from 200 to 500 and in the absence of a curing hardener can be accomplished within no more than 4 to 8 hours with an externally d temperature of 80°C without substantial decomposition of the resin. We have also found that this enables structures in which the resin has a Tg above 80°C, typically in the range 80°C to 110°C more lly 80°C to 100°C to be obtained within an acceptable curing time.
Thus, in further aspect, the invention relates to a process of curing the epoxy resin within a prepreg or prepreg stack as described herein, the process ing exposing the prepreg or prepreg stack to an ally applied temperature in the range 70°C to 110°C for a sufficient time to induce curing of the epoxy resin composition. The process may be med in a vacuum bag which may be placed in a mould or directly in a mould and is preferably carried out at a pressure of less than 3.0 bar absolute.
The curing process may be carried out at a re of less than 2.0 bar absolute. In a particularly preferred embodiment the pressure is less than atmospheric pressure. The curing process may be carried out employing one or more externally applied temperatures in the range of from 70°C to 110°C, for a time sufficient to cure the epoxy resin composition to the desired degree. In ular it is preferred that the curing cycle has a duration of less than three hours.
Curing at a pressure close to atmospheric pressure can be achieved by the led vacuum bag technique. This involves placing the prepreg or prepreg stack in an air-tight bag and ng a vacuum on the inside of the bag, the bag may be placed in a mould prior or after creating the vacuum and the resin then cured by externally applied heat to produce the moulded laminate. The use of the vacuum bag has the effect that the prepreg stack experiences a consolidation pressure of up to atmospheric pressure, depending on the degree of vacuum applied.
Upon curing, the prepreg or prepreg stack s a composite laminate, le for use in a structural application, such as for example an automotive, marine vehicle or an aerospace structure or a wind turbine structure such as a shell for a blade or a spar. Such composite laminates can comprise structural fibres at a level of from 80% to 15% by volume, preferably from 58% to 65% by volume.
The invention has applicability in the production of a wide variety of materials. One particular use is in the production of wind turbine blades. l wind turbine blades comprise two long shells which come together to form the outer surface of the blade and a ting spar within the blade and which extends at least partially along the length of the blade. The shells and the spar may be produced by curing the prepregs or stacks of prepregs of the t invention.
The length and shape of the shells vary but the trend is to use longer blades (requiring longer shells) which in turn can require thicker shells and a special sequence of prepregs within the stack to be cured. This imposes special ements on the materials from which they are prepared. Carbon fibre based prepregs are preferred for blades of length 30 metres or more particularly those of length 40 metres or more such as 45 to 65 . The length and shape of the shells may also lead to the use of different prepregs within the stack from which the shells are produced and may also lead to the use of different prepregs along the length of the shell. In view of their size and complexity the preferred process for the manufacture of wind energy components such as shells and spars is to provide the appropriate prepregs within a vacuum bag, which is placed in a mould and heated to the curing temperature. The bag may be evacuated before or after it is placed within the mould.
It will be appreciated that the size, shape and complexity of these wind turbine structures requiring large volumes of gs can produce considerable heat due to the exotherm generated by curing. The opportunities to reduce this exotherm presented by the present invention are therefore particularly valuable in the production of such wind turbine structures.
Furthermore, in order to withstand the conditions to which wind turbine structures are ted during use it is desirable that the cured prepregs from which the shells and spars are made have a high Tg and preferably a Tg greater than 90°C. In addition the present invention allows this to be accomplished employing reactive epoxy resin such as those with an epoxy equivalent weight of 200 to 500 without ing unduly long cure times.
The present ion is illustrated but in no way limited by reference to the following examples and to the accompanying figure in which Figure 1 shows a diagram of the complex viscosity for a resin matrix according to an embodiment of the invention; and Figure 2 shows a diagram of the temperature inside a prepreg stack of 60 plies of prepreg containing different resin matrices A to F and M according to the es.
The first series of experiments employed blends of liquid and semi solid epoxy resins free of dicyandiamide (DDM) blended with differing amounts of the latent urea base curing agent UR 500 (3,31-(4-methyl-1,3, ene) bis(1,1-Dimethylurea) ) and compared with a similar system ning in on the latent hardener dicyandiamide. The dynamic enthalpies of the formulations were measured as were the Tg of the resin after curing with an externally applied temperature of 80°C for 360 minutes. The e properties were measured according to ISO 427. The time to peak ature was also measured. The results were as follows.
The various resin system blends A,B,C,E,F are prepared by blending a semi-solid bisphenol- A epoxy resin (the same resin for all of blends A,B,C,D,E and F) with a UR500 accelerator at room temperature (21 0C) in the ratios as outlined in the below Table. The resin blend as an epoxy equivalent weight (EEW) in the range of from 180 to 340. The resin system blend D comprises 95.6% by weight (wt%) of semi-solid bisphenol-A epoxy resin, 1.3% by weight (wt%) of UR500 accelerator and 3.1% by weight (wt%) of a dicyandiamide hardener (Dyhard 100) Example 1 Resin Semi solid UR Peak c Time To Tg after System Bisphenol- DYHARD® Temperature Enthalpies Peak 360 mins A-epoxy 500 °C Joules/gram Minutes cure at resin (wt%) (wt%) (EN6041) 80°C A 97 3 147 85 105 87 B 96.5 3.5 145 93 90 89 C 96 4 149 120 99 89 D 95.6 1.3 147 290 157 95** E 99.6 0.4 140 4 ND. 27*** F 94 6 150 230 85 94 ** Not fully cured, N.D. *** No = Not Detectable, cure observed.
Table 1.
It can be seen that the products of the invention systems A, B and C have lower dynamic enthalpies and a r time to peak temperature than the traditional dicyandiamide containing system D indicating an ability for faster and more controllable cure at an externally applied temperature of 80°C than can be ed with the system also containing the dicyandiamide. The dynamic enthalpy was measured using a dynamic calorimeter DSC- 60/A and the measurement was in accordance with standard EN6041. System E, which ned 0.4% by weight of UR500, could not be cured at temperatures of 80°C. System F, which contained 6% by weight of UR500, cured with a dynamic enthalpy of 230 Jg'1 which is comparable to dynamic enthalpy of system D, the dicyandiamide containing system.
Example2 The formulations employed in Example 1 were impregnated onto triaxial glass fibres to produce prepregs containing 40 wt % resin for s A, B, C, E and F and 43% resin for system D. The impregnation levels for A, B, C, E, F and D are considered to be able and the difference in resin impregnation between the samples is not considered to be significant. The prepreg consists of a triaxial cross ed fabric of total weight of 1200 gsm (g/m2) which contains a fabric layer comprising glass unidirectional fibers in 0° direction of a nominal weight of 567 g/m2 which is sandwiched between glass unidirectional fibers in +450 and -45° directions of areal weight of 301 g/m2.
Lay-ups of 60 plies of the prepreg are prepared. A calibrated thermocouple is d in the centre of the lay-up to measure the temperature. The lay-ups are each cured at an isothermal 80 °C over 500 s which is applied to the stack ally.
Figure 2 shows the temperature profiles inside the lay-up stack for each of the lay-ups in combination with the oven temperature marked as “oven temperature” which shows an initial heat up rate of 1 00/ minute, followed by a cure at 80 °C. The s are marked A to F to correspond with the resin matrices A to F as defined in Example 1.
The time to peak temperature was also measured. The s were as follows: Resin System Max Temp in Stack °C Time to Max Temp Minutes A 120 240-270 B 120 240-270 C 120 240-270 D 140 360 E 82 N.D.* F 140 211 ND. = Not detectable, * Formulation did not cure.
Table 2 These results in Table 2 show that the systems A, B and C of the invention can be cured faster and more completely at externally applied temperatures below 100°C as opposed to the conventional prepreg (system D) which required more time and generated more heat.
System E failed to cure at temperatures with an externally applied temperature of 80°C.
System F, reached a maximum temperature of 140°C, this ed with a rapid cure resulted in partial decomposition of the matrix within the stack.
Mechanical Testing of Plaques (in accordance with EN2561) based on the laminar structures produced as above showed the following results as set out in Table 3: Resin System Tensile Strength MPa Tensile Modula (GPa) A 79 3.35 B 76 344 C 80 3.46 D 76 3.14 E NA. NA.
F NA. NA.
Table 3 A, B, C, E and F were cured with an externally applied temperature of 80°C for 6 hours, D was cured with an externally applied temperature of 120°C for 1 hour. The s show that comparable ical properties are achieved for the two systems with the invention enabling the use of a lower ally applied temperature. Mechanical testing could not be performed on resin system E as the system did not cure after a cure cycle of 80°C externally applied for 6 hours. As mentioned above, the stack containing resin system F exhibited partial matrix decomposition which was s upon visual inspection. Such decomposition can adversely affect the mechanical properties and can render a stack unsuitable for use, therefore no mechanical testing was necessary on the stack ning resin system F.
Example 3 Three ts were prepared to represent typical prepregs used for the manufacture of rotor blades for wind turbines employing resin systems. The prepregs were prepared from resin matrices A and C of Example 1 together with three different fibrous reinforcement materials.
The prepregs were as follows (ILSS Interlaminar shear strength, tensile properties ed in accordance with EN 2563; flexural properties measured in accordance with EN 2744) Prepreg Resin System Wt % Resin Glass Reinforcement Number of Layers Material 1 A 50% Biaxial 4 (Tensile) 2 ral ILSS) 2 A 38% Triaxial 2 (Tensile) 4 (Flexural ILSS) 3 A 32% stitched uniaxial 1 (Tensile) 4 (Flexural ILSS) 4 C 50% l 4 (Tensile) 7 (Flexural ILSS) C 38% Triaxial 2 le) 4 (Flexural ILSS) 6 C 32% stitched uniaxial 1 (Tensile) 4 (Flexural ILSS) Table 4 All the samples were cured in a vacuum bag placed in a mould that was heated with an externally applied temperature of 80°C for 6 hours.
The three materials were tested for mechanical mance and compared with the same performance data of system D cured with an externally applied temperature of 100-120°C.
The results were corrected to 50% fibre volume except for ILSS and were as follows: System 1 4 D Tensile (EN2563) Average values +/- Tensile Strength (MPa) 113.00 141.50 120.00 Norm. E-mod (GPa) 11.03 12.64 11.00 Elongation at Fmax (%) 10.60 9.20 11.30 Flexural (EN2744) Flexural th (MPa) 301.10 311.87 230.00 Norm. E-mod (GPa) 11.62 12.33 12.00 Deflection at Fmax (%) 6.00 6.00 N/A Table 5 System 2 5 D 0° 45° 0° 45° 0° 45° Tensile (EN2563) Average Average values values +/- 15% +/- 15 Tensile Strength (MPa) 517.26 272.00 515.21 256.64 500.00 270.00 Norm. E-mod (GPa) 24.47 19.25 25.33 25.21 21.00 15.00 Elongation at Fmax (%) 2.60 2.30 2.50 2.30 3.60 2.94 al (EN2744) Average Average values values +/- 15% +/- 15 Flexural Strength (MPa) 762.85 510.38 703.78 480.24 700.00 430.00 Norm. E-mod (GPa) 18.39 17.41 21.38 14.93 22.00 16.00 Deflection at Fmax (%) 4.20 2.90 3.00 3.80 N/A N/A ILSS 3) Average Average values values +/- 15 +/- 15 ILSS (MPa) 44.10 46.50 51.00 40.10 49.00 39.00 Table 6 System 3 6 D 0° 0° 0° Tensile (EN2563) Average values +/- Tensile Strength (MPa) 925.54 957.42 885.00 Norm. E-mod (GPa) 44.91 46.49 38.30 Elongation at Fmax (%) 2.20 2.20 3.70 Flexural (EN2744) Flexural Strength (MPa) 1016.79 995.56 975.00 Norm. E-mod (GPa) 26.03 25.96 31.00 tion at Fmax (%) 3.00 3.00 N/A ILSS (EN2563) Average values +/- 15 ILSS (MPa) 53.70 55.00 55.00 Table 7. In Tables 5,6 and 7 Fmax signifies the maximum force which can be applied before sample disintegration.
As can be seen from the Tables the ical performance of systems 1 to 6 which were cured with an externally applied temperature of 80°C was found to be at least as good as the performance of system D which was cured with an externally applied temperature of 100- 120°C.
Example4 Resin system A of Example 1 was cured at different atures. The time to 95% conversion of the resin was measured by DSC (ISO 11357). The results were as follows.
Temperature Cure Time* Tg cured 80°C 240min 85-90°C 90°C 130min. 100-110°C 100°C 75min 0°C 110°C 60min 100-110°C 120°C 55min 100-110°C *time to 95% conversion In Figure 1, the dynamic viscosity of the resin system A is shown over the temperature range of from 40 to 130 0C. The m viscosity is 1.6 Pa.s at a temperature of 94 0C.
There is thus provided a prepreg, a resin system, a laminate and a process as herein described. The process is particularly suitable for the production of wind turbine ures comprising ing a prepreg of stack of prepregs comprising a mixture of fibrous reinforcement and from 20 % to 85 wt % of an epoxy resin of EEW 150 to 1500 and containing from 0.5 to 10 wt % of a urea based curing agent and being free of dicyandiamide within a vacuum bag, placing the vacuum bag within a mould and creating a vacuum within the bag prior to or after placement in the mould and curing the epoxy resin by ation of an externally applied temperature in the range 70°C to 110°C for a period of from 4 to 8 hours. The resin is preferably a high viscosity resin having a ity at room temperature (21°C) in excess of 1800 mPa.s. The stack of prepregs in the aforesaid process would typically comprise at least 20 layers. The stack of prepregs has a thickness of from 2mm to 100mm. The fibrous reinforcement is preferably a carbon fibre. The wind turbine structure may be in the form of a shell for a blade of the wind turbine and has a length greater than 40 metres or from 45 to 65 metres.

Claims (18)

We claim:
1. A prepreg comprising a mixture of a fibrous rcement and an epoxy resin containing from 20% to 85% by weight of an epoxy resin of epoxy equivalent weight (EEW) from 150 to 1500 said resin comprising from 0.5 to 10 wt% based on the weight of 5 the epoxy resin of a urea based curing agent and being free of dicyandiamide, said resin further being curable by an externally applied temperature in the range of 70°C to 110°C.
2. A stack of prepregs containing an epoxy resin of epoxy equivalent weight (EEW) from 150 to 1500 the resin comprising from 0.5 to 10 wt% based on the weight of the epoxy resin of a urea based curing agent and being free of dicyandiamide, said resin 10 r being curable by an ally applied temperature in the range of 70°C to 110°C, the stack of prepregs containing at least 2 or more prepreg layers.
3. The stack of claim 2, wherein the stack of prepregs contains 40, 60 or more layers.
4. A prepreg or stack of prepregs according to any one of claims 1 to 3 15 wherein the resin ses from 0.5 to 5 wt % of the urea curing agent.
5. A prepreg or stack of prepregs ing to any one of the ing claims that can be cured in less than ten hours.
6. The prepreg or stack of prepregs of claim 5, wherein the prepreg or stack can be cured in less than eight hours. 20
7. A stack of prepregs according to any one of Claims 2 to 6 having a thickness of from 2 mm to 100 mm.
8. A curable stack of prepregs, at least one of said prepregs comprising a structural fibrous layer impregnated with an epoxy resin the epoxy resin having an epoxy equivalent weight (EEW) of from 150 to 1500 said resin comprising from 0.5 to 10 wt% 25 based on the weight of the epoxy resin of a urea based curing agent and being free of diamide, said resin further being curable at a temperature in the range of 70°C to 110°C.
9. A stack according to Claim 8 having a thickness of from 2 mm to 100 mm.
10. A laminate comprising a cured prepreg or stack of prepregs according to 30 any one of the preceding claims.
11. Use of a prepreg or a stack of prepregs according to any one of Claims 1 to 9 for the production of wind e structures.
12. A process of curing the epoxy resin within a prepreg or g stack according to any one of claims 1 to 9, the process involving exposing the prepreg or 35 prepreg stack to an externally applied temperature in the range 70°C to 110°C for up to 8 hours at a pressure of less than 3.0 bar absolute. (11126749_1):RTK
13. A process according to Claim 12 in which the epoxy resin has an epoxy equivalent weight (EEW) of from 200 to 500.
14. A process for the production of wind e structures comprising providing a prepreg or stack of prepregs comprising a mixture of s reinforcement 5 and from 20 % to 85 wt % of an epoxy resin of epoxy lent weight (EEW) 150 to 1500 and containing from 0.5 to 10 wt % based on the weight of the epoxy resin of a urea based curing agent and being free of dicyandiamide within a vacuum bag, placing the vacuum bag within a mould and creating a vacuum within the bag prior to or after placement in the mould and curing the epoxy resin by application of an externally applied 10 temperature in the range 70°C to 110°C for a period of from 4 to 8 hours.
15. A resin matrix comprising an epoxy resin ning from 20% to 85% by weight of an epoxy resin of epoxy equivalent weight (EEW) from 150 to 1500 said resin being curable by an externally applied temperature in the range of 70°C to 110°C, the resin containing from 0.5 to 5 wt % of a urea based curing agent, and being free of 15 dicyandiamide.
16. The resin matrix of claim 15, wherein the expoxy resin is curable by an externally applied temperature in the range of 70°C to 90°C.
17. The resin matrix of claim 15 or claim 16, wherein the urea based curing agent is a bis urea curing agent. 20
18. A wind turbine blade or component produced from a resin matrix as defined in any one of claims 15 to 17 in combination with a fibrous reinforcement.
NZ624037A 2011-12-22 2012-12-21 Improvements in or relating to fibre reinforced composites NZ624037B2 (en)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
EP11195398 2011-12-22
EP11195398.0 2011-12-22
EP12172537.8 2012-06-19
EP12172537 2012-06-19
PCT/EP2012/076780 WO2013093065A1 (en) 2011-12-22 2012-12-21 Improvements in or relating to fibre reinforced composites

Publications (2)

Publication Number Publication Date
NZ624037A NZ624037A (en) 2016-04-29
NZ624037B2 true NZ624037B2 (en) 2016-08-02

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