DE102014119160A1 - molding compound - Google Patents

Abstract

This invention relates to a method of making a polymer matrix composite comprising a resin matrix or a combination thereof; 5%, preferably 1% of the cured lay-up

Description

INTRODUCTION

In particular, PMC materials with high volume fractions of structural fibers produced by impregnation of the reinforcement with a curable or otherwise viscous polymer.

BACKGROUND

In a way to promote coverage, resin flow and / or structural stiffness, the fabric is not stretched, net-shaped, drapable onto doubly-curved surfaces, and is made of continuous yarn. Existing textiles generally deforming their mechanical performance.

In a process known as preforming Rolls of thin knitting of continuous yarns (plain weaves, twill weaves, satin weaves and / or other patterns of woven fabrics), knitting of continuous yarns (any type of warp-knitting and / or flat yarns); or weft-knitting), braiding of continuous yarns (any type of biaxial, triaxial or tubular braiding), stitching of parallel continuous yarns using a secondary thread, or any other process where continuous yarn reinforcements are combined into thin flat reinforcements.

Liquid Composite Molding (LCM) is widely used for Polymer Matrix Composite (PMC) production.

Liquid composite molding (LCM) or liquid resin infusion (LRI) is a process used to manufacture fiber-reinforced composite structures and components for use in a variety of industries including the aerospace, transportation, electronics, and building and leisure industries. The general concept in LRI technology involves infusing resins into a fiber reinforcement, fabric or pre-shaped fibrous reinforcement ("preform") by placing the material into a mold (two-component mold or single-sided mold) and then injecting resin under high pressure (or ambient pressure) in the mold cavity or vacuum sealed single-sided mold. The resin infuses into the material or preform resulting in a fiber-reinforced composite structure. LCM technology is particularly useful in manufacturing complex-shaped structures which are otherwise difficult to manufacture using conventional technologies.

Alternatively, the perform may be made from textiles which are preimpregnated. These processes are both versatile and cost-effective, they are widely used, and the resulting defects are not of plane deformations and inter-fiber gaps. Preform quality is itself determined by the draping operation.

SUMMARY OF THE INVENTION

According to the invention there is a method, a preform and a molding assembly as defined in any one of the accompanying claims.

The preform may be preimpregnated to form a near net shape molding material. Alternatively, the preform is unimpregnated but may be infused to form a near net shape molding material.

In one embodiment, the present invention provides a method for manufacturing thick net-shape continuous-fiber textile preforms from carbon reinforcement. This thesis may be performed and draped over complex molds, thus reducing labor intensive activities such as trimming, taping, layering fabric.

In another embodiment, the present invention provides a method of designing and manufacturing directional thick, net-shape, drapable reinforcement preforms, the method of making a pattern manual operation on a mold defined in 3D.

A method of optimizing yarn paths for enhanced coverage of the mold, using a Monte Carlo optimization method parameter of interest or a parameter of interest is identified.

In an embodiment, the present invention provides a novel textile architecture where yarn spacings of a textile may vary across the textile. These variable-length textiles can be customized for specific PMC applications, offering advantages over conventional constant-length textiles as well as a larger surface area covered by a single piece of textile, lower values of in-plane shear, and controlled fiber orientations. The variable-length textiles can be optimized manually or using model algorithms based on Monte Carlo methods which are implemented in the model.

We have discovered that the models for draping textiles so apply to resin impregnated fabrics and fibers such as prepregs.

SPECIFIC DESCRIPTION

The term composite identifies a class of engineered materials characterized by different physical and mechanical properties. The constituent materials can be polymers, metals or ceramics. Once combined, they offer performance advantages beyond those of the constituents. In one embodiment, the present invention provides polymer matrix composites (PMCs) made of carbon or glass fibers, encased in a polymer resin. Described below are aspects of manufacturing PMCs where the reinforcement is a textile. These PMCs are widely used in aerospace, automotive, nautical and recreational goods industries.

The basic principle of molding processes for PMC production consists in creating a lay up of structural fibers, known as a preform, the volume and shape of which corresponds to the volume and shape of the PMC part to be made. The structural fibers may be dry or they may be impregnated with resin. The operation of creating a lay-up assembly of fibers is commonly known as preforming.

In the case of dry fibers, the preform is infused with a curable liquid polymer or resin and the fibers are impregnated in an operation called resin infusion. Many different liquid molding processes exist including resin transfer molding (RTM), RTM-light, vacuum assisted resin transfer 2 molding (VARTM), resin film infusion (RFI), Seeman Composites Resin Infusion Molding Process (SCRIMP ^™ ) and Quickstep ^™ . The RTM process uses a mold made at least two stiff parts, forming a closed cavity which has the shape and dimensions of the PMC component to be made. During the production process, the mold is covered or draped with pieces of dry textile reinforcement. Alternatively, the preforming can be carried out on a separate tool, with the preform transported in the actual mold afterwards. Once preform is ready the mold is closed and resin is injected through carefully chosen injection ports; The thickness of the gap separating the mold parts ensures predictable component thickness. The orientation of the fibers and volume fraction throughout the component are largely determined when the preform is made, so precision in preform construction is of paramount importance. RTM-light half-and-one thin shell mold half made of composite material. This thin and relatively flexible mold helped to limit the resin injection pressures that can be used; resin flow in RTM-light is often driven by vacuum.

VARTM is a further evolution of RTM where the top mold is replaced by a series of breather cloths, a perforated film and an air-tight membrane which compresses the preform when a vacuum is drawn for resin infusion. Similarly to RTM, the preform construction largely determines how the fibers are oriented in the PMC component, while the compaction and vacuum levels have an effect on the final fiber volume fraction and PMC component thickness. RFI is very similar to VARTM with the difference of having a film of semi-cured resin incorporated in the layup, which is melted when heated and infused into the textile reinforcement. The resin film replaces the liquid resin which is drawn in by vacuum in the VARTM process. The patented SCRIMP ^™ process is thus very similar to the VARTM process with the addition of a patented flow medium which assists the flow of resin. While the process does offer advantages in terms of resin infusion over VARTM, it is still largely dependent on the preform construction in order to produce high quality PMC components.

The Quickstep ^™ process resembles both VARTM and RTM; while the preform is in a flexible membrane much like VARTM, a surrounding liquid can exert positive pressure on the preform much like the mold halves in RTM. However, unlike both RTM and VARTM, the curing process is activated by heat transferred via a heat transfer fluid (HTF); RTM may depend on the heat transferred from the mold. Again, a high quality PMC component can only be prepared by using a high quality preform.

Preforms may thus be formed from fibrous reinforcement layers which are preimpregnated with an reinforcing resin (prepreg).

The performance, integrity and reproducibility of PMC parts manufactured using any of the above molding processes are highly dependent on the quality of the preform. High-precision and long-lasting results in a limited amount of defects in a single-volume process. The edges of a high quality preform should be devoid of fraying. Finally, preform quality refers to whether preform thickness and fiber orientation are as specified. The thickness and fiber orientation of the PMC component during a gap and fiber orientation. The vf is defined as the percentage of the total volume of the PMC part which is occupied by the reinforcement. Typical values of range from 55% to 70% depending on the reinforcement and manufacturing process used. A PMC part with a low of vf wants to benefit fully from the mechanical properties of the reinforcement, but will be heavier due to the excess resin. Conversely, a PMC part with a vf which is too high may not be due to a varnish of resin, resulting in voids and very poor structural properties. The fiber orientation is the direction along which fibers impart their strength and stiffness to the PMC part. Fiber orientations which diverge from design specifications or are out-of-plane will yield a PMC component paint the desired design stiffness and / or strength. Lastly, the thickness of the finished PMC component is nearly identical to the thickness of the compact preform; thus it is imperative that the preform thickness.

Textile reinforcements which are dry or resin impregnated and used in preforms generally come as rolled stock, which needs to be cut, draped and compacted upon preform manufacturing. Draping involves placing layered pieces of dry textile reinforcement onto the mold surface while compacting, and applying a pressure to, respectively, positively or through vacuum. The draping operation should be done in between draping operations or only once at the end. Both the draping and compaction of the textile reinforcement deform the textile. Possible deformation modes for the textile include fiber stretching, fiber straightening, interfibre slip, tow buckling and in-plane shear among others. Whilst these deformations enable the draping of high vf preforms, they may lead to defects and low preform quality if badly applied or controlled.

In-plane shear is particularly important to the preforming process as it is capable of forming flat sheets of textile reinforcements to conform to doubly-curved surfaces. As such, it accounts for the vast majority of preform deformation. In-plane shear is introduced during the draping operation; It is drained on a flat surface that can be covered by a textile reinforcement as it is is draped. All textile reinforcements are limited in the amount of in-plane shear deformation that they can withstand before deforming out-of-plane through wrinkling and buckling. Out-of-plane deformations of dry reinforcements are particularly damaging to PMC parts because they may result in major difficulties for resin injection or major defects in the part upon infusion. In the RTM process, out-of-plane deformations could result in the inability to close the mold due to areas of increased thickness. Which is no longer aligned with applied loads, therefore, is not transmitted to the fibers. To effectively avoid the above defects and components deficiencies, it is important to drape the textile correctly, which can be made possible with accurate predictive simulation of the draping operation.

The design of preforms and parts, as well as their manufacturing, can be engineered by simulating the draining operation using high-resolution, or low-power, and the presence of potential out-of-plane deformation zones. Kinematic algorithms, finite element (FE) simulations, and hybrid kinematic energy methods have been elaborated for this purpose, including kinematic algorithms.

The kinematic or geometric method is essentially a mapping algorithm which predicts the path of yarns on the curved surface of simple geometric assumptions. The assumption is that the textile reinforcement acts much like a fishnet; a square mesh made of inextensible segments which corresponds to the centrelines of the textile yarns, running in two directions, which are usually orthogonal. The yarns may rotate relative to one another, but yarn stretching and slipping is not permitted. The fishnet may only be deformed by the rotation of segments around the yarn crossover. The kinematic method is dependent on the creation of two orthogonal geodesics which cross each other and define the global shape of the fishnet.

It is therefore possible to simulate the draping of textile reinforcements using finite elements. Different methods have been established, including a simplified unit cell method which uses 1D bar elements as shear and tow elements. The tow elements of the unit cell represent the yarn of the textile while the added shear elements represent the resistance to shearing of the textile, which makes it possible to find a minimum strain-energy solution for the textile. The draping is simulated by finding the configuration in which the total strain-energy of the simulated textile is minimal.

Alternatively, FE can be performed using an elementary pattern. The elementary pattern represents a crossover of perpendicular yarns before deformation, which is repeated in order to create an isoparametric bilinear four-node shell element. Each node in the element has three degrees of freedom to account for the three components of the node's displacement. The directions of the yarns in the elementary pattern correspond to the reference coordinates of the element. The modeling process can be used to simulate draping in a punch and die, where the punch and the are of the desired preform shape. Non-linear kinematics are used in order to calculate the deformation energy for each element, which should be minimized in order to determine the correct configuration.

The hybrid kinematic energy methodology is similar to the kinematic method by mapping the textile to a pin-jointed mesh similar to a fishnet. The segments may rotate relative to each other in order to conform to the model surface. However, instead of solving for geometric constraints only, the hybrid kinematic energy method solves for minimal shear deformation energy. Unlike the pure kinematic method, this method does not rely on the in-depth geodesics that extend to the boundaries of the surface to cover. Instead of the basic lines are determined as coverage progresses, allowing the simulated textile to deform more freely. The direction of the fibers and the shear deformation of each of the fishnet segments is defined by identifying the configuration in which the deformation energy is minimal. Additionally, the magnitude of the resistance to shear can vary; this gives the method to a certain amount of material, including textiles which have a tendency to shear in one direction with more ease than in the other direction.

Simulation software can deform and drape over a 3D surface. These predictions are used for better informing the design of preforms used in liquid molding processes. Fiberglass fractions and fiber orientations. This makes the creation of preforms which are more likely to fail. However, the extent to which a textile fabric can be deformed is indicated by the locking angle of that textile. Therefore there are limits to the surfaces and shapes that can be draped without defect. In conventional textiles the distinction between yarns and yarns is constant for a given textile. In one embodiment, the present invention provides a novel textile architecture where the textile's yarn spacing is allowed to vary across the textile. In a plane, or / or offer advantages over conventional textile reinforcements. The optimization of these variable-length textiles can be done manually or using software. Care should therefore be made flat, hence the software probes in-plane shear and of the optimized textiles both in the flat state before draping and in the draped state. It is therefore important to limit the length of the yarn in a yarn to yarn and to make it difficult to do so.

When draping the preform, the textile architecture has a great effect on how to do it. Textile reinforcements can be classified in different types according to their manufacturing process and structure, including weaves, knits, braids and stitched textile reinforcements. Such reinforcements are referred to as periodic fabrics and are generally supplied as rolls.

The preforming operation involves the deformation of the textile layers. The textile layers in place. The process and the deformation modes encountered during preforming were discussed in previous sections, with the exception of nesting. Nesting occurs when multiple layers of textile reinforcement are compacted and towed from one layer penetrating between the tows of the adjacent layer. Nesting may reduce the relative motion between textile layers and make the textile more compact.

Another point of practical importance should be mentioned. It is not possible, using current textiles and draping methods, to successfully make a preform with a single piece of textile, covering the surface of the mold entirely. These are usually flat or only gently curved. For this reason, multiple pieces of fabric are used in each layer, creating joints in the preform. Several types of joints exist as lap joints, butt joints and step joints. Only the butt and step joints may be used for manufacturing processes as RTM where the extra thickness of the lap joint makes it impossible in practice for the mold to close on the preform. While commonly used in VARTM applications, lap joints increase the local volume fraction of the preform at the joint seems.

Joints may cause problems due to racetrack in the gaps between the textile pieces during the infusion process.

To temporarily affix multiple pieces of textile to the preform mold, adhesives commonly called tackifiers or binders are typically used. Tackifiers, often supplied as a powder, can thus be applied between layers in multilayered textiles to simplify the handling of textile pieces in the creation of complex preforms. While the practical advantages to the preforming operation are evident, the use of a tackifier may have adverse effects on the infusion operation. Preform permeability decreases and may become uneven as the tackifier concentration is increased unless the tackifier is located within yarns. The tackifier may be so interfere with the resin on a chemical basis.

The simulation of the draping operation can be performed using geometric principles, using a method called kinematic simulation algorithm. The algorithm and mathematics for kinematic draping are described in detail in for example US 2013/0269159 which is incorporated by reference.

In the embodiment of structural polymer-matrix composite (PMC) materials and parts, the present invention provides methods for designing, optimizing and manufacturing the integral reinforcement of composite material and parts. Reinforcement preforms are typically draped onto a mold and combined with a polymer resin supplied in liquid or film form; once combined and solidified these two constituents form a PMC part. Advantages of the invention include: (1) The preforms are designed and optimized individually for specific PMC parts. (2) The preforms are manufactured as flat sheets to be drained onto molds in PMC manufacturing processes. (3) Curved yarns are oriented along two selected and / or optimized directions at each point of a preform but these orientations vary across the surface of the flat preform, and they are further modified as the preform is draped onto the mold, aiming at improving coverage of mold preforms and structural performance of the PMC parts. (4) The preforms are designed and manufactured net-shape, reducing / removing the need for any tailoring and cutting of reinforcement fabrics. (5) The preforms are manufactured to required thickness, reducing / removing the need for laminating successive layers of reinforcement fabric.

Assembled in a rigid preform, with the polymer matrix (typically epoxy encapsulating the fibers and primarily for positioning the fibers in the PMC parts, for protecting the fibers from the environment, and for transferring stresses from the environment to the fibers. Fibers with diameters ranging from about 5 [mu] m to 15 [mu] m are preferred for easy conformability of the reinforcement preforms to curved mold surfaces and to be used in PMC parts. PMC manufacturing takes place PMC manufacturing operations is not practical, thus fibers are traditionally assembled into various types such as weaves, braids, and others in separate textile manufacturing operations. Initially, individual fibers are grouped into yarns of a few hundred to a few thousand fibers. PMC manufacturing operations are then followed by conventional processings. These fabrics become the reinforcement in PMC parts.

Woven fabrics are produced in continuous sheets of set widths as rolls. A typical woven reinforcement is much better than the thickness of a typical PMC part, hence the fabrics are usually referred to as thin ('2D') fabrics. Traditional textile reinforcements are not intended for specific PMC parts in terms of outline, thickness or orientations of fibers and yarns.

Shakes: parts where one dimension-the thickness-orders of magnitude smaller than other dimensions. Shells usually are not flat-they feature varying levels of curvature and are defined in the 3D space. An airfoil, the nose cone of aircraft and a saddle shape are examples of shells. Shells are defined by a contour or outline. Preparing the reinforcement for such shells typically involves cutting pieces of fabric from a roll and laying them on the curved surface of a mold. Many superimposed pieces of thin fabric are required to achieve a required thickness. PMC parts are often referred to as laminated: more layers are needed for thicker parts, and inversely. The operation of conforming textile pieces to the surface of a mold is called draping. A stack of superimposed layers of reinforcement fabric pieces. Draped into shape on a mold is often referred to as a preform. The outline of the individual pieces of fabric from the continuous roll of thin fabric should match the outline of the preform to be made as much as possible. However, the outline of a flat piece of fabric differs from the outline of the same piece once it is draped on a mold and into the final preform, and the draping operation is very delicate because of the nature of textile reinforcements. Therefore, preform manufacturing remains highly manual-many unsuccessful attempts at automation were made-and-time-consuming, and its outcome is very variable. Laser projection systems are often used to indicate where and how a given piece of fabric should fall on the mold once draped. Cutting textiles to outlines leads to potential fraying and handling of single layers can result in some disassembling. Positioning layers on top of each other with precision is tremendously difficult. Traditionally, this has precluded textile-based PMCs based on dry textile preforms-which are relatively-from-entering aerospace markets. The preforming technology according to an embodiment of the present invention.

A typical 2D fabric is made from two sets of parallel and equidistant yarns (warp yarns and yarn yarns in a weave, for example). Two sets of yarns are perpendicular. However, the fabrics are subject to wear and tear, even though the yarns in each other remain in a plane and equidistant-the distance varies during in-plane shear when measured perpendicularly to the yarns. This can be visualized if a square is drawn on the fabric; as the fabric undergoes in-plane shear the square takes the aspect of a diamond, with the 4 sides maintaining a constant length. This capability for large and reversible strain shear strain is not found in materials such as sheet metal. Point 1 is important because it is made of stiff and virtually inextensible fiber reinforcement. This is a limit shear angle-typically labeled "locking angle" beyond which a fabric does not shear but buckle-buckling of fabrics in preform highly detrimental to PMC performance and should be avoided. Fabrics can shear more or less depending on construction; capability to undergo high shear strain is always desirable. 2) A fabric may be used in either direction. resistance to shear and locking angle differ for both directions, depending on construction.

A fabric in any given state is characterized by its fiber volume fraction (vf). This value can change in different situations for a given fabric. It can therefore change from point to point in a piece of fabric and in a preform. The fiber volume fraction is the fraction of the volume circumscribing a fabric, or part of a fabric or preform. For example, assuming a representative thickness for a sheet of fabric, a 50% means that half of the volume within this thickness is occupied by fibers. A high vf is highly beneficial for the specific structural properties of PMCs; however vf can not reach 100%. Textiles may be compacted to normal. vf Thus, when the thicknesses of the fabric remain constant, the thicknesses of the fabric remain constant. Usually thickness does not remain constant upon shearing, so there is no systematic structural advantage for the PMC.

Woven and braided fabrics are interlaced as yarns cross over each other during textile manufacturing; this is what holds yarns together for these textile manufacturing processes. But interlacing generally reduces the ability of fabrics to undergo in-plane shear, and thus reduces the primary structural properties of PMCs made from reinforcements. Other means of manufacturing 2D fabrics from two sets of parallel yarns exist, where the yarns are held together by light stitched lines realized by processes including stitching, warp-knitting and others. In this document and much PMC literature, we are looking for non-crimp stitched (NCS) 2D fabrics.

Advantages of the preforming technology according to the invention include: (1) the ability to design, optimize and manufacture individual preforms for PMC parts of known shape and geometry PMC structural behavior; (2) the ability to design, optimize and manufacture textile preforms as flat; drapable individual pieces of textile as opposed to cutting; (3) the ability to design, optimize and manufacture textile preforms as flat, drapable individual pieces of flat textile as opposed to the molds in 3D, so that the same machinery may be used in all cases and preforms can be easily exported; (4) the ability to design, optimize and manufacture textile preforms, including two local yarn orientations that vary throughout the preform-both prior to and after draping on a mold, PMC manufacturing and structural performance; (5) the design, optimization and manufacture of textile shape preforms, reducing / removing the need for cutting and assembling numerous textile pieces; and (6) the ability to design, optimize and manufacture textile preforms to the required thickness, reducing / removing the need for laminating and superimposing numerous textile pieces.

Textile preforms manufactured using the technology according to the present invention are flat, thus typically they should be subjected to a curved mold defined in 3D. This method of producing distinct, part-specific textile pieces enables at least three important technical features: (1) textile preforms operation-the resultant thick textile preform is known as 2.5D (thick textile preform in this proposal); (2) textile preforms can be built into the required outline (flat) in a single operation-the resulting thick textile preform is known as the net-shape (thick-net-shape textile preform in this proposal); (3) there is no limitation in the flat fabric feature (s) only as yarn paths in the flat fabric (before draping). The present invention is characterized by the fact that it is capable of producing PMC manufacturing or PMC manufacturing. Search textiles are referred to here as directional thick net-shape textile preforms. It should be noted that it is perfectly possible to make thick net-shape textile preforms with straight yarns, and that this would constitute optimum solution in some cases. But the design manufacturing process defines allows yarn directionality. The architecture of the preform according to whichever aspect of the invention is concerned, and which both flat and draped.

One of the advantages of the preforming technology according to the invention is that of the manufacture of the same as it is. This promotes process versatility and simplicity. Whilst it may be used on an industrial robot or highly dedicated machinery, dry yarns laid on anything and horizontal surfaces do not stay in place and should be used with ancillary devices. The preforming technology according to the invention is simple and it produces flat preforms that are easier to wrap and ship. Another notable advantage of the preforming technology according to preforms, namely the cutting, manual handling and manual draping of individual thin layers. It does offer potential for improved consistency.

The architecture of the invention is straightforward. Preforms consist of layers of superimposed no-crimp yarns assembled by a stitch. Simpler textile structures are available in thin ('2D') form and sold as continuous rolls with straight yarns only-such thin fabrics are generally recognised as superior to their woven counterparts and their use is widespread. 3) yarns in the preforms. 2) the preforms are thick, 2) the preforms are deep-shaped, and 3) yarns in the preforms can be directional.

In one embodiment, the present invention provides a method for manufacturing the aforementioned directional thick-shape reinforcement preforms.

In one embodiment, the present invention provides optimizing yarn paths in the flat directional thick-shape reinforcement preforms, aiming at optimizing mold coverage, resin flow through fabric and / or stiffness of final PMC part.

Most resin infusion systems are inherently brittle, and the viscosity levels necessary to achieve the injection process preclude the use of toughening agents. Said differently, the properties of toughness and low viscosity are typically mutually exclusive in conventional resin infusion systems. In prepregs, high levels of toughness are generally increased by about ten percent (10%) to about thirty percent (30%) by weight of a thermoplastic toughener to the base resin. However, addition of such tougheners to LRI system generally results in an unacceptable increase in the viscosity of the resin and / or reduction in resistance of the cured material to solvents. In the specific case of particulate toughener, there may be additional filtering issues in the textile. These limitations render the addition of tougheners conventionally added in prepregs generally unsuitable in conventional LRI applications.

One technology to tough fiber-reinforced composite structures produced by LRI technologies is to integrate the toughener into the preform itself. Which would otherwise increase the viscosity of the resin (rendering it unsuitable for resin infusion). Another example of the use of soluble or insoluble veils comprising of toughener is used as an interleaf with the reinforcement of the preform. However, in either of these methods, the manufacturing process may be more complicated and costly, in addition to increasing the risk of hot / wet performance with a polymer based insoluble interleaf. Another technology is the addition of particles to the resin. The process is often unfavorable for LRI.

A formulation comprising: (i) at least one base resin; (ii) amount of particles within a range in a carrier resin; and (iii) an amount of thermoplastics material in a range of temperatures. The resin particles are combined to form a modified resin system is disclosed in.

We have already discovered that this formulation is used as a resin for preimpregnating textiles, fibers or fabrics as described hereinbefore

The formulation may further comprise a curing agent. The curing agent may be an aniline-based amine compound. The base resin may be one of epoxy, bismaleimide, cyanate ester or a combination thereof. The base resin may be a combination of epoxies including at least one di-, tri- or tetra-epoxy. The particles may be one of chemically functionalized or chemically non-functionalized core-shell rubber particles or hollow particles. The material may include one or more polybutadiene-styrenes, polybutadiene or a combination thereof, and a material comprising the shell may be one of silica, polymerized monomers of acrylic acid derivatives containing the acrylic group including acrylic and poly (methyl methacrylate) or a combination thereof. The thermoplastic material may be one of phenoxy-based polymers, poly (ether sulfone) polymers, poly (ether ether sulfones), poly (methyl methacrylate) polymers , carboxylterminated butadiene acrylonitrile polymers, copolymers thereof, or combinations thereof. In a cured condition, at least the thermoplastic material phase may be separated from the base resin. More particularly, the thermoplastic material phase may be divided into aggregate domains from the resin base, each aggregate domain having an island-like morphology. The morphology in a cured article may evolve: (i) during the later stages of a ramp to dwell temperature; or (ii) after a ramp to dwell has been completed during the cure cycle. The amount of particles and the amount of thermoplastic material may be combined in a 1 to 0.56 ratio. The threshold average viscosity may be less than 180 ° C, more narrowly between 80 ° C and 130 ° C.

A composite article, comprising: a structure having a shape, the structure having a specific composite toughness within a range resin system during a process, the modified resin system including: (i) at least one base resin; (ii) amount of particles within a range in a carrier resin; and (iii) an amount of thermoplastic material within a thermoplastic resin range, the particles and the thermoplastic material are combined to form the modified resinous system is disclosed in. The modified resin system may further include a curing agent, the curing agent comprising aniline-based amine compound. The base resin may be one of epoxy, bismaleimide, cyanate ester or a combination thereof. The base resin may include a combination of epoxies including at least one di-, tri- or tetra-epoxy. When the particles are CSR particles, a material comprising the core is one of polybutadiene-styrene, polybutadiene or a combination thereof, and a material comprising the shell is one of silica, polymerized monomers of acrylic acid derivatives containing the acrylic group including acrylic and poly (methyl methacrylate) or a combination thereof. The thermoplastic material may be one of phenoxy-based polymers, poly (ether sulfone) polymers, poly (ether ether sulfones), polymerized monomers of acrylic acid derivatives containing the acrylic group including acrylic and poly (methyl methacrylate) polymers, carboxyl-terminated butadiene, acrylonitrile polymers, or copolymers thereof. The amount of thermoplastic material is approximately 30% net weight, preferably less than 7% net weight, of the modified resin system base resin, each aggregate domain having an island-like morphology. The amount of particles and the amount of thermoplastic material may be combined in a 1 to 0.56 ratio. The structure may exhibit a high level of microcrack resistance. Poise at a temperature of less than 180 ° C, more narrowly between 80 ° C to 130 ° C. Organic polymer, inorganic polymer, carbon, glass, inorganic oxide, carbide, ceramic, metal or a combination thereof. The process may be a liquid resin infusion manufacturing process, a prepreg manufacturing process or a resin film infusion process.

A formulation comprising: (i) a base resin comprising at least one epoxy; (ii) a curing agent; (iii) amount of thermoplastic material; and (iv) an amount of core-shell particles in the base resin, the curing agent, the thermoplastic material and the particles are combined to form the modified resin system , 7% net weight, of the total weight of the modified resin system is disclosed in.

With the base resin in a partially cured or gel-like state, the thermoplastic material phase may separate into aggregate domains from the base resin. The amount of particles and the amount of thermoplastic material may be combined in a 1 to 0.56 ratio. With the base resin in a partially cured, gel-like, The modified resin system may have an average viscosity of less than 180 ° C, more narrowly between 80 ° C and 130 ° C , With the base resin in a cured or vitrified condition, the thermoplastic material may separate into aggregate domains from the base resin, each aggregate domain having an island-like morphology. The morphology in a cured article may evolve (i) during the later stages of a ramp to dwell temperature or (ii) after a ramp to dwell has been completed during the cure cycle. A manufacturing process, comprising: (i) preparing a preform; (ii) laying the preform within a mold; (iii) heating the mold to a predefined temperature; and (iv) injecting a resin in a modified resin, the modified resin system comprising a combination of: (i) at least one base resin; (ii) a curing agent; (iii) an amount of particles within a range in a carrier resin; and (iv) an amount of thermoplastic material is less than 30% net weight, or less than 7% net weight, of the total weight of the modified resin system disc losed.

The temperature of the mold may be 1 10 ° C. 10 ° C per minute, more narrowly, less than 5 ° C per minute. The manufacturing process, when the mold reaches 180 ° C, the temperature is between 90 minutes and 150 minutes. The preform may be sealed within the mold by at least a vacuum bag. 5 Poise at a temperature range of less than 180 ° C, more narrowly between 80 ° C and 130 ° C. The preform may be of a complex of layers of fiber-based fabric. The fiber-based fabric may include a woven fabric, multi-warp knitted fabrics, non-crimp fabrics, unidirectional fabrics, braided socks and fabrics, narrow fabrics and tapes or fully-fashioned knit fabrics. The fiber-based fabric may be used as an organic polymer, inorganic polymer, carbon, glass, inorganic oxide, carbide, ceramic, metal or a combination thereof.

Embodiments of the invention are directed to modified resin systems for use in resin infusion (RI) processes, variations of LRI processes and other suitable processes such as prepreg processes. In an embodiment, the modified resin system includes a novel combination of at least one base resin, an amount of particles in a range and an amount of thermoplastic material within a range Below a threshold average viscosity within a specific temperature range and a high level of toughness. The modified resin system may also include a curing agent and other suitable components. The modified resin system has been experimentally shown to exhibit a unique, controllable and constant morphology. glass transition temperature or tensile modulus of the modified resin system.

According to the invention, a combination of at least one base resin and an amount of particulate matter can be added to a range, in addition to other components. Formulation of a modified resin system which can be used in RI / LRI processes or prepreg processes. Unexpectedly low viscosity, low reactivity, a high level of toughness (GJC), among other characteristics, when subjected to numerous experimental tests. It is also anticipated that the modified resin infusion process will include, but not limited to, Resin Infusion with Flexible Tooling (RIFT), Constant Pressure Infusion (CPI), Bulk Resin Infusion (BRI), Controlled Atmospheric Pressure Resin Infusion (CAPRI), Resin Transfer Molding (RTM), Seaman Composites Resin Infusion Molding Process (SCRIMP ^™ ), Vacuum-assisted Resin Infusion (VARI), Resin Transfer Injection (RTI) and Vacuum-assisted Resin Transfer Molding (VARTM) as well as other processes used to manufacture composite articles.

In the context of this application, a "resin" is a synthetic polymer compound which begins in a viscous state and hardens with treatment. Resins are used as a structural matrix material in the manufacture of adhesives and composites and are often reinforced with fibers (eg, glass, evlar, boron and carbon). In some respects, the base resin may be any one of epoxy, bismaleimides, benzoxazines, cyanates esters, vinyl esters, polyisocyanurates, bismalimides, cyanates esters, phenolic resins or any combination thereof in addition to other suitable resins. In some aspects, the base resin is an epoxy resin or a combination of epoxy resins. The epoxy resin may be tetra-, tri-, di-epoxy or combinations of tetra-, tri- and / or di-epoxies. Exemplary tri-epoxies include triglycidyl p-aminophenol (MY-0510 available from Huntsman Advanced Materials, Inc.) and ARALDITE ^® (MY-0600 available from Huntsman Advanced Materials, Inc.). An exemplary tetra-epoxy is tetraglycidyl diaminodiphenylmethane (MY-721 available from Huntsman Advanced Materials, Inc.). Other suitable epoxy resins include bisphenol F epoxy (PY-306 available from Ciba Geigy).

In the context of this application, a "particle" is a polymer-based material having a core-shell or hollow morphology. Core-shell rubber (CSR) particles surrounded by an outer shell of glassy material. CSR particles are used as toughening agents when combined with polymeric matrices, e.g., epoxy resins. Having a core material of polybutadiene-styrene or polybutadiene and having a shell material of acrylic acid or polybutadiene; (methyl methacrylate). The CSR particles may be used in a carrier resin such as tetraglycidyl diaminodiphenyl methane (ie, MY-721) and may have a diameter of about fifty (50) nanometers (run) and about eight hundred (800) nm, in one embodiment , about one-hundred (100) nm. Examples of commercially available CSR particles include, but are not limited to, the Paraloid series of materials (available from Rohm and Haas), MX411 (polybutadiene-styrene / acrylic) and MX416 (polybutadiene / acrylic) (both are dispersions in Huntsman MY721 epoxy resin and are available from Kaneka Corp.); however, any particle exhibiting the CSR or hollow structure as described above may be used in the modified resin system according to the invention.

Core-shell particles have been evidenced to tough LRI systems via a cavitation mechanism in addition to crack pinning or "tear out" mechanisms. In a cavitation mechanism, the rubbery cores of the CSR particles yield under the stress at a crack tip, resulting in dissipation of energy from the crack front and the formation of voids in the core material.

In the context of this application, a "thermoplastic" is a polymer that is elastic and flexible above a glass transition temperature (Tg). In some of the other, the thermoplastic material comprises one of phenoxy-based polymers, poly (ether sulfone) (PES) polymers, poly (ether ether sulfones), polymerized monomers containing acrylic and poly (methyl methacrylate). (PMMA) polymers, carboxyl terminated butadiene acrylonitrile (CTBN) polymers, copolymers thereof, or combinations thereof. Representative thermoplastics include, but are not limited to, KM180 (available from Cytec Industries Inc.), 5003P (available from Sumitomo Corp.), PKHB (InChemRes); however, any thermoplastic or other suitable material (eg, Nanostrength X, available from Arkema, Inc.) exhibiting a thermally driven phase separation from a base resin, more particularly exhibiting aggregate domains, or to "island-like" morphology (explained in more detail below), may be used in the modified resin systems according to the invention.

An example of a typical mechanism for thermoplastic toughening of composite or resin matrices is crack pinning. <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> Another example of a typical toughening mechanism is shown as a localized plastic deformation upon application of a stress to the material. A "curing agent" is a substance or mixture of substances added to a polymer composition (e.g., resin) to promote or control the curing reaction. Addition of curing agent functions to harden and harden a polymer material by cross-linking of polymer chains. Representative curing agents include, but are not limited to, methylene bis (3-chloro-2,6-diethylaniline) (MCDEA), 3,3'-diaminodiphenyl sulfone (3,3'-DDS), 4,4'-diaminodiphenyl sulfone ( 4,4'-DDS), dicyandiamide (DICY), N-methyl-diethanolamine (MDEA) and 4,4'-methylene-bis (2-isopropyl-6-methyl-aniline) (MMIPA).

According to the modified resin system, the modified resin system combined with an amount of CSR particles in a 1 to 0.56 ratio of thermoplastic to CSR particles. In one embodiment, the base resin may be a combination of di-, tetra- and tri-epoxies such as PY-306, MY-0500 and / or MY-0600). In one embodiment, the thermoplastic material may be 5003P and the CSR particles may be MX41 1 (in MY-721) or MX416 (in MY-721) one-hundred (100) nm particles. A curing agent, such as MCDEA, may be added to the "one pot" resin system to make the resin system curable when heat and / or pressure is / are applied.

The formulation of the present invention at least one base resin; in amount of particles within a range in a carrier resin; The modified resin having an average viscosity and a modest amount of thermoplastic material is used. Poise at a temperature of less than 180 ° C and preferably at a temperature of between 80 ° C and 130 ° C.

When the formulation is in a cured condition, at least the thermoplastic material is phase having aggregated from the base resin, each aggregate domain having an island-like morphology. The cure morphology evolves (i) during the later stages of a ramp to dwell temperature or (ii) after a ramp to dwell has been completed during the cure cycle.

The amount of thermoplastic material in the formulation is approximately 30% by weight of the modified resin system.

The formulation may include an amount of particles and the amount of thermoplastic material combined in a 1 to 0.56 ratio.

Each aggregate has been subjected to the same process as a thermoplastic material.

The modified resin system is a modified resin. The modified resin system according to claim 1 is a modified resin : (i) at least one base resin; (ii) a curing agent; (iii) amount of particles within a range in a carrier resin; and (iv) the total weight of the modified resin system is less than 30% by weight.

90 ° C and 120 ° C more or less The temperature of the mold is 110 ° C.

The manufacturing process can be done at a rate of 2 ° C per minute.

Furthermore, when the mold reaches 180 ° C, the temperature may be about 120 minutes.

The manufacturing process may be practiced in the preform as described hereinbefore. The fiber-based fabric may include a woven fabric, multi-warp knitted fabrics, non-crimp fabrics, unidirectional fabrics, braided socks and fabrics, narrow fabrics and tapes or fully-fashioned knit fabrics. Of organic polymer, inorganic polymer, carbon, glass, inorganic oxide, carbide, ceramic, metal or a combination thereof.

The preform may be infused with resin or preimpregnated with a resin as inbefore described.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2013/0269159 [0034]

Claims (4)

 A method of making a polymer matrix composite comprising the steps of assembling a preform of one or more composite elements each comprising a fibrous reinforcing material, a resin matrix or a combination thereof; 5%, preferably 1% of the cured lay-up.  The method of claim 1, is a composite element with a resin prior to processing of the composite.  The method of claim 1 or 2, the composite element is impregnated with a resin prior to processing of the composite.  The method of any of the preceding claims, the composite element.