Fiber preform injection and impregnation method

Abstract

The present invention relates to a method for injecting and impregnating a fiber preform with a polycondensable resin, wherein at least, A) Supplying resin to the intermediate container (13) at a pressure higher than atmospheric pressure, wherein the supply operation includes at least A1) transferring resin (20) from the first container (11) to the heater (12), A2) heating the resin using the heater, and A3) transferring resin (22) to the intermediate container (13), and supplying resin to the intermediate container (13) at a pressure higher than atmospheric pressure. B) Injecting and impregnating a fiber preform (14) with a polycondensable resin transferred by suction from an intermediate container maintained at an injection and impregnation temperature above the injection temperature, The present invention relates to a method in which the supply of the intermediate container is carried out at a pressure of 1.5 absolute bar or more, and the injection impregnation is carried out at a pressure of 0.1 absolute bar or less.

Description

[Technical Field]

[0001] This disclosure relates to a method for impregnating a fibrous structure with a phenolic resin for the manufacture of composite material components. [Background technology]

[0002] Composite materials have undergone significant industrial development.

[0003] These materials are characterized by a fibrous structure, also called a fibrous preform, in which resin fills the voids, and the resin forms a matrix after curing.

[0004] These properties depend not only on the properties of the fibers in the fibrous tissue, but also on the properties of the bonds between the fibers or the properties of the matrix.

[0005] Therefore, a variety of options offers a wide range of possibilities, making it possible to obtain materials with properties specifically defined for particular applications.

[0006] In particular, for aerospace applications, these materials are often considered favorable alternatives to metal parts because they are lighter than these components while providing at least the same, if not better, mechanical properties.

[0007] However, impregnating the voids in the fibrous structure sometimes presents industrial challenges. In fact, the properties of composite materials depend not only on the fibrous preform but also on the matrix it contains, which is why it is essential that the internal voids of the fibrous preform are filled with the matrix, and that this filling is homogeneous throughout the fibrous preform.

[0008] Areas of the preform that are not impregnated with the matrix will not have the same mechanical or thermal properties as the rest of the composite material component, which is undesirable.

[0009] Numerous fiber preform impregnation methods have been developed, each adapted to individual matrices or preforms.

[0010] However, none of the prior art methods appear suitable for obtaining thick injection-impregnated parts having a controlled porous, polycondensable resin matrix.

[0011] Polycondensing resins have very high viscosity at room temperature. While it is known that heating such resins can reduce their viscosity, this method is not used industrially because it causes premature initiation of polymerization and volatilization of the solvent contained within the resin. This latter point also applies when the resin is placed under reduced pressure. In addition to the fact that uncontrolled temperature can lead to exothermic runaway, whose risk must be absolutely controlled, the volatilization of the solvent contained within the resin can result in large variations in porosity in the final product, stemming from variations in the chemical fluid properties of the injected and impregnated resin.

[0012] These effects complicate the use of polyphenol resins, and novel manufacturing methods adapted to the constraints outlined above are still needed to enable their use in the production of composite material components. [Overview of the project] [Problems that the invention aims to solve]

[0013] Disclosure of the present invention The present invention aims to effectively address the above-mentioned problems. [Means for solving the problem]

[0014] Therefore, the present invention provides a method for injecting and impregnating a fiber preform with a polycondensable resin, comprising at least, A) Supplying the polycondensable resin to the intermediate container, wherein the resin is injected from the first container into the intermediate container at a pressure higher than atmospheric pressure, and the supply operation is at least, A1) Transferring the resin from the first container where it is stored at the storage temperature to the heater, A2) Heating the resin to an injection temperature higher than the storage temperature using a heater, A3) Transferring the resin, heated in this manner at a pressure higher than atmospheric pressure, from the heater to an intermediate container, The process involves supplying the polycondensable resin to an intermediate container, and B) Injecting and impregnating a fiber preform with a polycondensable resin transferred by suction from an intermediate container maintained at an injection / impregnation temperature above the injection temperature. Includes, The present invention relates to a method in which the supply of an intermediate container (A) is carried out by applying a pressure of 1.5 absolute bar or more to the resin, and the injection and impregnation of a fiber preform (B) is carried out by applying a pressure of 0.1 absolute bar or less to the resin.

[0015] On the one hand, this method ensures that the polymerization of the resin cannot begin before it is injected and impregnated into the preform.

[0016] In fact, resin polymerization only begins at sufficiently high temperatures and is not observed at room temperature.

[0017] The pressure applied for supply A) ensures that the resin composition remains the same, and in particular, that no volatile species, including solvents, leak during this step, which may be observed when reduced pressure is applied.

[0018] Since the reaction temperature range of the resin includes room temperature, the earliest point at which polymerization can begin is when the resin arrives in the intermediate container.

[0019] In one embodiment, step A) can be performed at a pressure of 1.5 absolute bar to 5.0 absolute bar, or 1.5 absolute bar to 3.0 absolute bar.

[0020] "Absolute bar" is understood in the meaning it usually has in the art, i.e., it defines the pressure relative to a vacuum which is arbitrarily set such that its pressure is taken as a reference and equal to 0 absolute bar. Further, the method makes it possible to ensure that the resin reaches the intermediate container at a temperature at which it is suitable for its injection, i.e., a temperature at which the resin has a sufficiently low viscosity, through control of the combination of time and temperature.

[0021] Thus, the achievement of the inventors is that they have successfully proposed a method for bringing the polycondensable resin to a temperature sufficient for its injection without the polycondensable resin starting polymerization or releasing its volatiles.

[0022] Furthermore, the method makes it possible to bring a large amount of phenolic resin to the injection impregnation temperature without the risk of early chemical changes. This is because the phenolic resin is brought to this temperature and then withdrawn at a controlled flow rate and injected and impregnated into the fiber preform.

[0023] Step B) of injecting and impregnating the resin into the preform maintained under reduced pressure has two further advantages.

[0024] This reduced pressure facilitates the removal of solvents and other volatile species with which the resin can be formulated and promotes the polymerization of the resin.

[0025] Furthermore, the reduced pressure promotes the removal of water which is a co-product of the polycondensation of the resin, which advantageously shifts the thermodynamic equilibrium of the reaction towards polycondensation. Thus, the progress of the polycondensation is favorable. Only the water bound to the three-dimensional crosslinked network remains in the matrix. Thus, the free water is removed.

[0026] In one embodiment, the viscosity of the resin at the storage temperature is 500 mPa·s or more or 800 mPa·s or more.

[0027] In one embodiment, the viscosity of the resin in the first container is 500 mPa·s or more or 800 mPa·s or more.

[0028] This viscosity value is sufficient to allow the resin to be transported from the initial container to the heater under excessive pressure while keeping the resin temperature as low as possible.

[0029] In one embodiment, the temperature of the resin in the initial container is 40°C or lower, or even room temperature.

[0030] In one embodiment, the first container may be at room temperature, which allows for an even simpler method as it does not require any specific conditioning system.

[0031] The initial temperature of the container is sufficient to give the resin enough viscosity to be poured into the heater, but it remains insufficient to initiate its polymerization.

[0032] In one embodiment, the amount of resin contained in the first container may correspond to the total amount of resin required to fill the voids within the fibrous structure.

[0033] For example, the amount of resin contained in the first container may be 50 kg or more, or even 60 kg or more.

[0034] Preferably, the resin present in the initial container is maintained under constant stirring. This allows for excellent homogeneity of the resin, even if the initial container contains a large amount of resin.

[0035] In one embodiment, the viscosity of the resin at the injection and impregnation temperature is 200 mPa·s or less, or 150 mPa·s or less.

[0036] In one embodiment, the viscosity of the resin in the intermediate container is 200 mPa·s or less, or 150 mPa·s or less.

[0037] This viscosity, reduced by the rising temperature, allows for superior injection impregnation of the preform.

[0038] Viscosity in the sense of this application is understood as dynamic viscosity and is measured in mPa·s. This characterizes the flow resistance of a fluid and can be defined as the ratio of shear stress to the velocity gradient perpendicular to the shear surface.

[0039] For example, it can be measured by a Brookfield viscometer in accordance with NF EN ISO 2555.

[0040] In one embodiment, the injection and impregnation temperature is 70°C or higher, for example, 75°C to 90°C, or 75°C to 85°C.

[0041] This temperature allows for a sufficient reduction in the viscosity of the resin, on the one hand, and ensures good drainage of the solvent that enables polymerization, on the other hand.

[0042] In one embodiment, the storage temperature is 20°C to 45°C, the injection temperature is 65°C to 90°C, and the injection impregnation temperature is 75°C to 90°C.

[0043] These temperature values ​​for this method are optimal for ensuring the injection of the resin into the intermediate container without initiating polymerization, while simultaneously ensuring easier injection impregnation.

[0044] Supply A), as shown, allows for the supply of polycondensable resin to an intermediate container, enabling the acquisition of polycondensable resin at a temperature suitable for injection impregnation but before polymerization has begun.

[0045] Next, injection impregnation B) involves injecting and impregnating the preform with a polycondensing resin.

[0046] In one embodiment, during injection impregnation B), the flow rate of resin supplied from the heater to the intermediate container is 90% to 110% of the flow rate of resin drawn out for injection impregnation of the fiber preform.

[0047] By selecting a flow rate that balances the supply to the intermediate container and the injection and impregnation of the preform, it is ensured that the intermediate container is neither overfilled, which could lead to excessively long residence times of the resin within the intermediate container, nor underfilled, which could lead to the injection and impregnation of undesirable air bubbles into the preform.

[0048] In one embodiment, the flow rate of resin supplied from the heater to the intermediate container is equal to the flow rate at which the fiber preform is drawn out for injection impregnation.

[0049] For example, the intermediate container may contain an amount of resin of 5 kg or less, or even 4 kg or less, or more preferably 3 kg or less.

[0050] In one embodiment, the supply rate of the intermediate container may include a first temporary filling regime before the start of injection impregnation B).

[0051] The use of an intermediate container ensures that only a small amount of resin polymerizes throughout this method.

[0052] In fact, as mentioned above, the resin cannot begin polymerization until it reaches the intermediate container.

[0053] Furthermore, because the resin is removed from the intermediate container for injection and impregnation into the fiber preform, the resin ultimately remains in the intermediate container for only a very short time, and therefore, polymerization of the resin proceeds only very slightly within the intermediate container.

[0054] In other words, the resin does not have time to polymerize in the intermediate container; it is removed from there and injected into the preform, where the polymerization process is completed.

[0055] In one embodiment, the resin injection and impregnation B) into the preform can be performed at different points on the fiber preform.

[0056] Unlike methods in which injection impregnation is performed at a single point, such embodiments allow for excellent uniformity in the injection impregnation rate of the resin within the preform.

[0057] In fact, injection impregnation of the preform results in the desired filling of the fiber preform with resin. If the resin is injected and impregnated into the preform at a single point, the injection impregnation rate decreases as the preform is filled.

[0058] Conversely, if injection impregnation is performed at several points on the preform, the resin only needs to travel a shorter distance within the preform from the injection impregnation point, thereby ensuring better uniformity of the injection impregnation.

[0059] In one embodiment, the resin is injected and impregnated at several points in the preform, but the supply is performed at only one point at a given time.

[0060] In other words, the resin is first injected and impregnated from the first supply point, and this supply is then interrupted when the supply from the second supply point is released, and so on until the last supply point.

[0061] This embodiment ensures excellent control over the progress of injection impregnation of the fiber preform, in addition to excellent uniformity of the injection impregnation.

[0062] In one embodiment, the resin is selected from polyfuran resin or polyphenol resin, preferably polyphenol resin.

[0063] For example, such resins may be commercially available products RS101 or RA101 from Solvay, or Furolite from TFC.

[0064] These resins are, in practice, too viscous at low temperatures and polymerize when heated, making reliable injection impregnation difficult. Therefore, conventional methods, unlike the injection impregnation methods described above, are insufficient to enable preform impregnation by known methods.

[0065] In one embodiment, the resin is compounded with at least 20% by mass of different types of resins, or at least 30% by mass of different types of resins.

[0066] The phrase "combined together" is intended to characterize the fact that the storage container may contain, in addition to the resin, so-called volatile compounds, such as solvents and / or other special additives different from the resin.

[0067] In one embodiment, the resin is compounded with at least 20% or at least 30% of a volatile compound.

[0068] Such volatile compounds can be used, for example, to reduce the viscosity of a resin and / or to chemically block its polymerization during storage.

[0069] This method is even more advantageous because it allows these volatile compounds to be retained in the intermediate container due to the initial container and heater and the high pressure.

[0070] Unlike prior art methods, this method ensures good retention of volatile compounds in the resin, and therefore makes it possible to inhibit the progression of polymerization until the resin reaches the intermediate container.

[0071] In one embodiment, the intermediate container and the fiber preform are placed in the same oven.

[0072] In one embodiment, the fiber preform may further include an injection-impregnation cover, in which case the intermediate container, the fiber preform, and its injection-impregnation cover may be placed in the same oven.

[0073] This embodiment ensures that the resin is maintained at the injection impregnation temperature after passing through the heater and reaching the intermediate container. Furthermore, this ensures that the resin is not cooled between the injection into the intermediate container and the injection into the preform.

[0074] In one embodiment, the preform contains or is composed of carbon fibers.

[0075] For example, preforms can take the form of atmospheric re-entry elements for aerospace vehicles.

[0076] Such a re-entry element may have a first sphere and a second sphere opposite to the first sphere.

[0077] For example, this element is a cone with circular ends and vertices.

[0078] In one embodiment, the resin is heated in an intermediate container to a temperature of 75°C to 90°C, or 75°C to 85°C. At such temperatures, the resin can begin its polymerization.

[0079] In one embodiment, the minimum dimensions of the space occupied by the resin in the intermediate container are 10 cm or less, or 5 cm or less.

[0080] Since resin polymerization is exothermic, if the resin is not under conditions that allow it to dissipate the heat generated by polymerization, a runaway reaction due to overheating may be observed.

[0081] The inventors found that in embodiments including two dimensions in which the volume occupied by the resin in the intermediate container is considerably larger than a third dimension, limiting the space occupied by the resin in the third dimension is sufficient to prevent exothermic runaway polymerization. More precisely, the inventors found that the minimum dimension of the volume occupied by the resin is the primary control of the ability of a given volume of resin to exchange heat with the container.

[0082] If one dimension is three or five times larger than another, we will refer to it as "considerably larger."

[0083] This embodiment ensures that the resin present in the intermediate container is able to exchange a controlled amount of heat with the outside of the intermediate container.

[0084] This heat exchange is advantageous because it prevents the reaction from becoming exothermic and runaway.

[0085] In fact, the heat generated by polymerization is dissipated through heat exchange with the outside or contributes to raising the temperature of the resin. However, when the temperature of the resin rises, it polymerizes again, which releases energy again and contributes to a runaway reaction due to heat generation.

[0086] Thermodynamic runaway can, in the worst case, lead to deterioration of the equipment used in this method or the preform, rendering the entire component unsuitable for its intended application.

[0087] Therefore, to avoid the risk of thermodynamic runaway, it is advantageous to provide an intermediate container that allows for sufficient heat exchange when the resin is brought to the injection and impregnation temperature.

[0088] Our greatest achievement is our ability to define the maximum allowable dimension for the minimum volume occupied by the resin, and to understand and model the temperature progression in a given volume of resin so that the runaway heat generation of the resin can be controlled by the injection and impregnation temperature.

[0089] The reaction rate, heat capacity, and polymerization enthalpy are determined by differential calorimetry. The dynamic behavior of the resin is then modeled using an autocatalytic dynamics model, followed by simulation of the resin's behavior during polymerization. This is experimentally verified by comparing Fournier's law, established in 1D / 2D, with experimental heating / polymerization tests measured by thermocouples in a thermal enclosure. The thermochemical fluid properties of the resin are represented by a dimensionless material model.

[0090] Therefore, the latter succeeded in establishing a law that defines the maximum allowable dimensions for the minimum dimensions of the space occupied by the resin in the intermediate container, which makes it possible to minimize the risk of exothermic runaway for a given volume of resin at a given temperature, and in knowing the residence time of the resin in that volume.

[0091] This is reflected in the "minimum dimensions of the space occupied by the resin in the intermediate container," which is a result of the inventors' understanding of the thermal and kinetic behavior of the polymerization reaction.

[0092] This embodiment limits the risk of thermal runaway of the resin after it has been injected and impregnated into the fiber preform, and ensures that the polymerization of the resin can be carried out reliably without the risk of runaway.

[0093] In fact, as explained regarding the intermediate container, the minimum dimensions of the space occupied by the preform determine whether the resin is at risk of overheating and runaway.

[0094] In one embodiment, the thickness of the fiber preform is 100 mm or less, or 60 mm or less.

[0095] In one embodiment, the thickness of the fiber preform is 10 mm or more, or 65 mm or more, or 80 mm or more.

[0096] The preform thickness is understood in the usual sense as the minimum dimension of the preform, and the thickness proposed above ensures that the polymerization reaction does not run out of control.

[0097] Since preforms of this thickness require a larger amount of resin for impregnation compared to those of the same shape, the injection impregnation method described above is even more advantageous for preforms of this thickness.

[0098] With preforms of this thickness, a larger amount of resin is introduced, and as mentioned above, there is a risk of thermal runaway of the resin; therefore, it is impossible to inject and impregnate such preforms with resin using conventional methods.

[0099] In contrast, the method described above allows for the injection impregnation of the preform to be controlled much better, and only a portion of the resin can polymerize at a given moment in the process, thus enabling such injection impregnation of the preform.

[0100] In fact, the use of an intermediate container, in addition to the advantages already mentioned, ensures that only a small amount of resin is in a position to polymerize at a given moment in the process.

[0101] Furthermore, as mentioned above, in one embodiment, the injection and impregnation temperature is 70°C or higher, for example, 75°C to 85°C.

[0102] This temperature, along with limiting the amount of resin that reaches the injection impregnation temperature, allows for limiting the risk of thermal runaway while simultaneously enabling the acquisition of a fluid-stable resin over the injection impregnation time.

[0103] Furthermore, the supply rate of the intermediate container and the injection / impregnation rate of the preform can be easily adjusted to inject and impregnate low volumes of resin without the risk of overheating runaway.

[0104] In one embodiment, the fiber preform contains carbon fibers and has a thickness of 10 mm or more.

[0105] In one embodiment, injection impregnation B) may include an injection impregnation rate that changes between the injection impregnation step and the pause step in which no injection impregnation takes place.

[0106] In such embodiments, the supply of the intermediate container A) may include an injection impregnation rate of 90% to 110% of the injection impregnation rate of injection impregnation B).

[0107] Alternatively, supply A) may include a constant rate, but the rate may be slower than that of the injection-impregnation stage, so that the intermediate container is filled during the pause stage and emptied during the injection-impregnation stage. Furthermore, the rate is adjusted to ensure that the minimum dimension of the space occupied by the resin in the intermediate container is always less than 10 cm within the intermediate container. [Brief explanation of the drawing]

[0108] [Figure 1] This is a schematic diagram of an apparatus for carrying out the method according to an embodiment of the present invention. [Modes for carrying out the invention]

[0109] The present invention is illustrated by drawings that exist for illustrative purposes to illustrate specific embodiments of the invention and should not be construed as limiting the invention.

[0110] Figure 1 schematically shows an apparatus that enables the implementation of the above method.

[0111] Figure 1 shows the first container 11 containing a large amount of resin 20.

[0112] Next, the resin 20 is injected into the heater 12 through the channel 21.

[0113] Next, the resin is injected into the intermediate container 13 through channel 22.

[0114] Note that the volume of resin 23 in the intermediate container 13 is considerably smaller than the volume of resin 20 in the initial container 11.

[0115] The heater 12 shown here is a heater that uses a water bath, and the resin passes through a coil immersed in a thermostat-controlled bath at the injection temperature.

[0116] Other heater shapes can be considered, and the energy efficiency of heat transfer can be improved.

[0117] In one embodiment, the heater 12 may be a countercurrent heater.

[0118] In such a heater, the resin enters through the duct 21 at the storage temperature, i.e., the temperature of the initial container 11.

[0119] In the heater, the resin is brought into contact with a heat transfer fluid that is at a higher temperature than the resin, for example, which is placed around the duct through which the resin is transported.

[0120] When the resin comes into contact with the heat transfer fluid, it is heated and the heat transfer fluid is cooled. The temperatures of the heat transfer fluid and the replacement surface are selected so that the resin is at its injection temperature when it leaves the heater.

[0121] As described above, the resin 20 in the initial container 11, the resin that has passed through the heater 12, and the resin that has exited the heater 12 are maintained under pressure.

[0122] The resin, which leaves the heater 12 through channel 22, reaches the intermediate container 13.

[0123] The resin 23 in the intermediate container 13 is at atmospheric pressure, and then polymerization begins.

[0124] However, the resin 23 in the intermediate container 13 does not remain there long enough to completely polymerize.

[0125] In fact, the resin 23 contained in the intermediate container is injected and impregnated into the preform 14 via the supply channel 24.

[0126] As shown in the illustration, in one embodiment, injection can be performed at different locations on the preform.

[0127] When the resin 23 is injected and impregnated into the preform 14, the voids in the preform are maintained under reduced pressure by the vacuum device 15.

[0128] Such a vacuum device 15 may be, for example, a pump.

[0129] As described above, the resin is injected and impregnated into the preform at an injection and impregnation temperature equal to or higher than the injection temperature of the resin into the intermediate container 13.

[0130] For this purpose, the fiber preform 14 can be placed inside the oven 16, as shown in Figure 1.

[0131] In the illustrated embodiment, the intermediate container 13 is located in the same oven 16 as the preform 14. However, as long as the intermediate container 13 is maintained at the injection temperature, even if it is not, it does not exceed the scope of the present invention.

[0132] The method of the present invention described herein also makes it possible to avoid runaway overheating of the resin.

[0133] Since the storage temperature is low enough to prevent the resin 20 from polymerizing, thermal runaway cannot occur in the initial container 11.

[0134] The pressure applied to the resin 20 in the initial container helps prevent polymerization by preventing the removal of volatile species mixed with the resin.

[0135] Thermal runaway cannot occur in the intermediate container 23 because the resin does not remain there for a sufficiently long time or is not present in a sufficient quantity.

[0136] Thermal runaway increases with residence time, resin temperature, and the volume of stored resin.

[0137] Thermal runaway is exothermic, characterized by a rapid rise in the temperature of a resin due to its polymerization, which is accelerated by temperature.

[0138] Because the residence time of the resin 23 in the intermediate container 13 is short, the resin cannot polymerize within it.

[0139] However, in order to further reduce the probability of thermal runaway events, the inventors studied the thermal behavior of the resin in detail as a function of its volume and residence time.

[0140] As a result, the inventors were able to describe a general law of temperature evolution.

[0141] Such laws make it possible to predict the progression of temperature, and therefore the occurrence of thermal runaway, depending on given parameters.

[0142] By knowing the operating conditions of this method, particularly the flow rate of resin entering and leaving the intermediate container 13, as well as the injection and injection impregnation temperatures, it was possible to define an upper limit on the minimum size of the space occupied by the resin, which is one of the other advantages of this method, in order to ensure that a given volume of resin cannot exhibit a runaway overheating reaction.

[0143] The law governing heat dissipation in such resins can be expressed according to the following equation [Equation 1].

[0144]

number

[0145] In equation [Equation 1], ρ is the density of the resin / composite material (kg·m³). -3 ) and Cp is the mass heat capacity (J·kg) of the resin / composite material. -1 ·K -1 ) and λ is the conductivity (W·m) of the resin / composite material. -1 ·K -1 ) and ΔH tot The total enthalpy of polymerization (J·kg) -1 ) and V mis the mass fraction of the material, and dα / dt is the reaction rate of the resin (s -1 ).

[0146] The reaction rate dα / dt of the resin can be expressed by Equation [Equation 2].

[0147] [Number]

[0148] In Equation [Equation 2], A, E, n, and m are constants specific to the resin under consideration.

[0149] Table 1 shows the conventional digits for the assumed applications.

[0150] [Table 1]

[0151] In the example shown in FIG. 1, the outer surface of the container at the intermediate contact 13 is located within the oven 16. Therefore, this outer surface is maintained at the temperature of the oven 16, i.e., the injection impregnation temperature.

[0152] Therefore, since the resin that has started polymerization continues to be sucked towards the preform, the temperature of the resin 23 remains in a stable state. Therefore, this container is maintained at the temperature of the oven 16 when the minimum dimension of the volume occupied by the resin, actually when the height of the resin in the intermediate container 13 is less than 10 cm, thereby preventing thermal runaway of the resin 23, and in this case, the resin can dissipate excessive energy.

[0153] The figures are not to scale and are for illustrative purposes only.

[0154] In one embodiment, the height of the resin in the intermediate container 13 is the minimum dimension of the volume occupied by the resin in the intermediate container 13. In other words, the width and length of the intermediate container, or its diameter if appropriate, are considerably larger than the height of the resin present in the intermediate container 13.

[0155] The inventors' achievement lies in their ability to characterize the thermal behavior of the resin, then identify the maximum amount of resin in the intermediate container 13, and ensure that the resin does not pose a risk of thermal runaway within the intermediate container.

[0156] The same reason applies to the resin that fills the internal voids of preform 14.

[0157] In fact, the resin introduced into the internal voids of the preform must polymerize to form the desired composite material component.

[0158] In doing so, it releases heat, and to avoid thermal runaway, that heat must be dissipated by the fiber preform 14.

[0159] Nevertheless, it should be noted that since the resin is continuously injected and impregnated, and the injected resin polymerizes as soon as it reaches the preform, the resin introduced at the start of injection impregnation can polymerize before the entire injection impregnation is completed, which already limits the risk of thermal runaway of the polymerization reaction.

[0160] Therefore, the amount of resin introduced into the preform 14 may be equal to the initial amount of resin 20 stored in the first container 11, but the resin introduced into the preform will not cause thermal runaway.

[0161] Figure 1 also includes graphs showing temperature T read on axis 100, curve 101, and pressure P read on axis 200, curve 201, which are dominant in various elements of the resin pathway in one embodiment.

[0162] Temperature T and pressure P are shown approximately for room temperature (Tamb) and atmospheric pressure (Patm), respectively.

[0163] As can be seen from the graph, and as mentioned above, the initial container 11 is at room temperature (Tamb) and at a pressure higher than atmospheric pressure.

[0164] The resin is transferred to the intermediate container 13 at a pressure still higher than atmospheric pressure (Patm).

[0165] In heater 12, the resin temperature rises to the injection temperature.

[0166] Next, the resin reaches an intermediate container, where it remains at atmospheric pressure before being injected and impregnated into the fiber preform 14 under a pressure lower than atmospheric pressure (Patm). Some embodiments of the present invention are shown below. [Embodiment 1] A method for injecting and impregnating a fiber preform with a polycondensing resin, wherein at least, A) Supplying the polycondensable resin to the intermediate container (13), wherein the resin (22) is injected from the first container (11) into the intermediate container at a pressure higher than atmospheric pressure, and the supply operation is at least, A1) Transferring the resin (20) from the first container (11) where the resin is stored at the storage temperature to the heater (12), A2) Heating the resin to an injection temperature higher than the storage temperature using the heater, A3) Transferring the resin (22) that has been heated in this manner from the heater (12) to the intermediate container (13), The polycondensable resin is supplied to an intermediate container (13), which includes the following: B) Injecting and impregnating the fiber preform (14) with the polycondensable resin that has been transferred by suction from the intermediate container, which is maintained at an injection and impregnation temperature equal to or higher than the injection temperature, Includes, A method wherein the supply of the intermediate container is carried out by applying a pressure of 1.5 absolute bar or more to the resin, and the injection and impregnation of the fiber preform is carried out by applying a pressure of 0.1 absolute bar or less to the resin. [Embodiment 2] The injection impregnation method according to Embodiment 1, wherein the viscosity of the resin (20) at the storage temperature is 800 mPa·s or more. [Embodiment 3] The injection impregnation method according to Embodiment 1 or 2, wherein the viscosity of the resin (23) at the injection impregnation temperature is 200 mPa·s or less. [Embodiment 4] The injection impregnation method according to any one of Embodiments 1 to 3, wherein the storage temperature is 20°C to 45°C, the injection temperature is 65°C to 90°C, and the injection impregnation temperature is 75°C to 90°C. [Embodiment 5] The injection impregnation method according to any one of Embodiments 1 to 4, wherein, during the injection impregnation, the flow rate of the resin supplied from the heater (12) to the intermediate container (13) is 90% to 110% of the flow rate of the resin (24) drawn out for the injection impregnation of the fiber preform. [Embodiment 6] The injection impregnation method according to any one of Embodiments 1 to 5, wherein the intermediate container (13) and the fiber preform (14) are placed in the same oven (16) maintained at the injection impregnation temperature. [Embodiment 7] The injection impregnation method according to any one of Embodiments 1 to 6, wherein the resin (20, 23) is selected from polyphenol resin or polyfuran resin. [Embodiment 8] The injection impregnation method according to any one of Embodiments 1 to 7, wherein the resin (20, 23) is blended together with at least 20% of a volatile compound. [Embodiment 9] The injection impregnation method according to any one of Embodiments 1 to 8, wherein the minimum dimension of the space occupied by the resin in the intermediate container (13) is 10 cm or less. [Embodiment 10] The injection impregnation method according to any one of Embodiments 1 to 9, wherein the fiber preform (14) contains carbon fibers and has a thickness of 10 mm or more.

Claims

1. A method for injecting and impregnating a fiber preform with a polycondensing resin, wherein at least, A) Supplying the polycondensable resin to the intermediate container (13), wherein the resin (22) is injected from the first container (11) into the intermediate container at a pressure higher than atmospheric pressure, and the supply operation is at least, A1) Transferring the resin (20) from the first container (11) where the resin is stored at the storage temperature to the heater (12), A2) Heating the resin to an injection temperature higher than the storage temperature using the heater, A3) Transferring the resin (22) that has been heated in this manner from the heater (12) to the intermediate container (13), The polycondensable resin is supplied to an intermediate container (13), which includes the following: B) Injecting and impregnating the fiber preform (14) with the polycondensable resin that has been transferred by suction from the intermediate container, which has been maintained at an injection and impregnation temperature equal to or higher than the injection temperature, Includes, A method wherein the supply of the intermediate container is carried out by applying a pressure of 1.5 absolute bar or more to the resin, and the injection and impregnation of the fiber preform is carried out by applying a pressure of 0.1 absolute bar or less to the resin.

2. The injection impregnation method according to claim 1, wherein the viscosity of the resin (20) at the storage temperature is 800 mPa·s or more.

3. The injection impregnation method according to claim 1, wherein the viscosity of the resin (23) at the injection impregnation temperature is 200 mPa·s or less.

4. The injection impregnation method according to any one of claims 1 to 3, wherein the storage temperature is 20°C to 45°C, the injection temperature is 65°C to 90°C, and the injection impregnation temperature is 75°C to 90°C.

5. The injection impregnation method according to any one of claims 1 to 3, wherein, during the injection impregnation, the flow rate of the resin supplied from the heater (12) to the intermediate container (13) is 90% to 110% of the flow rate of the resin (24) drawn out for the injection impregnation of the fiber preform.

6. The injection impregnation method according to any one of claims 1 to 3, wherein the intermediate container (13) and the fiber preform (14) are placed in the same oven (16) maintained at the injection impregnation temperature.

7. The injection impregnation method according to any one of claims 1 to 3, wherein the resin (20, 23) is selected from polyphenol resin or polyfuran resin.

8. The injection impregnation method according to any one of claims 1 to 3, wherein the resin (20, 23) is blended with at least 20% of a volatile compound.

9. The injection impregnation method according to any one of claims 1 to 3, wherein the minimum dimension of the space occupied by the resin in the intermediate container (13) is 10 cm or less.

10. The injection impregnation method according to any one of claims 1 to 3, wherein the fiber preform (14) contains carbon fibers and has a thickness of 10 mm or more.

Images