FR3045449A1 - - Google Patents

Abstract

The invention relates to a method and an installation for manufacturing a fiber-reinforced composite part by means of an injection process, according to which the internal pressure of the tool is measured inside the injection zone (12). using one or more pressure sensors (Si at Sa), pressure-time variation behaviors are formed, and a pore movement is observed as a function of the pressure-time variation behaviors.

Description

The invention relates to a method and an installation for manufacturing a fiber-reinforced composite part by means of an injection process, in which a matrix material is injected into a material based on of fibers, and the matrix material having been injected is cured. The use of fiber-reinforced composite materials is now almost inevitable in the aeronautical and aerospace field. But the use of such materials is finding increasing success even in the field of the automotive industry, a reason and not least being that fiber reinforced composite parts made of a fiber reinforced composite material have a specific strength and rigidity by weight, very high. Consequently, the tendency is to manufacture more and more often critical structural parts in such composite materials reinforced with fibers.

However, the fiber-reinforced composite materials have some disadvantages, especially concerning the manufacture, compared to conventional materials such as aluminum. Thus, the manufacture of fiber reinforced composite parts still today requires in many areas, work steps and manual process monitoring, which make the manufacture of such parts relatively expensive.

An essential quality characteristic of fiber reinforced composite parts made by an injection process is the complete impregnation or infiltration of the matrix material into the fiber material. In conventional injection processes, a dry fiber-based or slightly pre-impregnated material is also used, which is introduced into a suitable shaping tool and then infiltrated with a matrix material. , by the use of an appropriate injection pressure. The matrix material, which may for example be a thermosetting resin and form after curing an integral assembly with the infiltrated fiber material, is hereby generally prepared and made available in a reservoir which is communicatively connected to the material based on fibers, via injection lines.

When injecting the matrix material into the fiber-based material, however, it is necessary to ensure that no gas inclusions are formed in the fiber-based material, or that the pore content of the the room is too high, because such a quality defect outside the tolerable limit, leads to the scrapping of the room. The causes of such gas inclusions, also known as "dry spots", are to be found, for example, in the advance of the matrix material or the matrix system, which causes reunitions of flow fronts then leading to gas inclusions and so to defective areas. Poor interaction between different casting attacks and air purges or the variation of the impregnating properties of the fiber material can also be at the origin of such gas inclusions.

There is therefore a real interest in wanting to prevent such gas inclusions. Since, as a general rule, this can not be 100% assured, it is of great interest, particularly for mass production, to be able to detect such gas inclusions already during the injection phase, in order to be able to take countermeasures in good time, or be able to extract the part of the production process early. This reduces manufacturing costs and increases quality. DE 10 2013 100 092 A1 discloses a method for testing the impregnation of fiber-reinforced composite materials, according to which the workpiece is probed with ultrasonic transmitters and receivers. ultrasound, then we conclude to a degree of impregnation with regard to the reflection of ultrasound. DE 10 2007 060 739 A1 discloses a method and a device for the manufacture of fiber-reinforced composite parts, according to which in the edge regions of the forming tool a set of temperature lower than in the rest of the room, to thereby avoid a faster advance of the matrix resin at these border areas. It is possible here, using pressure sensors, to conclude on the shape of the flow front. According to the document EP 2 105 285 A2, there is known a method and a device for the manufacture of a fiber-reinforced composite part according to which pressure sensors are for example integrated in the vacuum sheet, for so be able to measure the internal pressure. With regard to the pressure measurement, it is then possible to conclude that there may be a leak in the evacuation structure. According to the document WO 2014/006131 A2, there is known a method and a device for the manufacture of a fiber reinforced composite part, according to which are also carried out, with the aid of pressure sensors, measurements of pressure during the injection of the matrix resin, and the injection pressure is then adjusted based on the pressure values, so as to achieve an optimal flow rate of the matrix resin. From US 5,219,498 a method is finally known in which dielectric properties of the fiber material are measured using a dielectric sensor.

Accordingly, it is an object of the present invention to provide an improved process and an improved installation for increasing the quality of the part with respect to gas inclusions and pore formation.

This object is achieved by the process for manufacturing a fiber-reinforced composite part by means of an injection process in which a matrix material is injected into a fiber-based material and the matrix material having been injected is cured. method comprising the steps of: a) introducing a fiber-based material into an injection zone of a forming tool, and preparing a matrix material outside the injection zone, in a reservoir communicatively connected to the injection zone; b) producing a pressure difference between the matrix material and the injection zone so that an injection pressure acts on the matrix material; matrix is injected into the fiber-based material having been introduced into the injection zone, characterized by c) measuring the internal pressure of the tooling within the zone injection using one or more pressure sensors during and / or after injection of the matrix material, so as to determine a large number of measurement values for each pressure sensor, d) form behaviors pressure-time variation of the internal pressure of the tooling for each pressure sensor, as a function of the measurement values of the respective pressure sensor, using a data processing unit, and e) identifying at least a characteristic deviation in at least one formed pressure-time variation behavior, and ascertaining a pore movement of one or more pores within the matrix material as a function of an identified deviation in at least one pressure variation behavior -time, by the data processing unit.

The goal is further achieved by an apparatus for manufacturing a fiber-reinforced composite part by means of an injection process in which a matrix material is injected into a fiber material and the injected matrix material is cured. the installation comprising a) a forming tool, which has an injection zone in which the fiber-based material can be introduced and communicatively connected to a reservoir for storing the matrix material, characterized in that (b) one or more pressure sensors are provided for measuring the internal pressure of the tooling within the injection zone; and (c) a data processing unit connected to the sensors is provided. of pressure, configured to form pressure-time variation behaviors of the internal pressure of the tooling for each pressure sensor in function measuring values of the respective pressure sensor, and for identifying at least one characteristic deviation in at least one pressure-time variation behavior formed, and detecting a pore movement of one or more pores within the matrix material according to a difference identified in at least one pressure-time variation behavior.

According to the invention there is provided a method for manufacturing a fiber-reinforced composite part by means of an injection process in which a matrix material is injected into a fiber-based material and the matrix material having been injected. is hardened. The matrix material and the fiber-based material are here components of a fiber-reinforced composite material for the manufacture of a fiber-reinforced composite part. Prior to injection, the fiber-based material may be dry or (slightly) pre-impregnated.

According to the known injection methods, the fiber-based material is here introduced into an injection zone of a forming tool, and the matrix material is prepared outside the injection zone, in a tank communicatively connected to the injection zone. The injection zone is here part of the tool in which the fiber-based material is introduced, which is then subjected to injection with the matrix material. In the conventional open mold process, the injection zone is delimited by a shaping tooling surface on the one hand and the evacuation complex on the other hand, which contains, in particular, a foil corresponding vacuum. In the conventional closed mold (closed mold) process, the injection zone is surrounded by two or more half-molds, and most often closed in a vacuum-tight manner.

After introduction of the fiber-based material and the preparation of the matrix material, an injection pressure acting on the matrix material is produced so that the matrix material is injected from the reservoir via a pipe. in the fiber material having been introduced into the injection zone. The production of the injection pressure can for example be effected by suction of air in the injection zone, thereby establishing a thin vacuum / vacuum. Due to the atmospheric outside pressure and the resulting pressure difference, it settles on the matrix material, which has been prepared outside the injection zone, an injection pressure acting in the direction of the injection area. Alternatively or in addition to this, it is also possible to exert on the matrix material, which is prepared outside the injection zone, a higher pressure with respect to the pressure conditions of the injection zone, by example higher than the atmospheric pressure, which produces alternatively or additionally an additional injection pressure (or fraction thereof).

According to the invention, it is now provided during or after the injection of the matrix material, to continuously determine the internal pressure of the tooling using pressure sensors arranged inside the zone d injection, so that multiple measurement values are thus determined for each pressure sensor. A pressure sensor is already sufficient here, when it is arranged for example near the air purge port said "ventingport-. The air purge port normally designates the last filled area of a tool or a pipe leading to a resin trap before the vacuum pump.

Then, for each pressure sensor, from the measurement values of the individual pressure sensors, the corresponding pressure-time variation behaviors of the internal pressure of the tool are formed, so that for each sensor it is produced for each sensor. pressure, a pressure variation behavior of the internal pressure at the position of the pressure sensor, with respect to time. This can for example be detected online, a pressure-time variation behavior that can also consist of discrete measurement values.

According to the invention, it is then proposed to identify at least one characteristic deviation in at least one pressure-time variation behavior formed, and then, as a function of a characteristic deviation identified in at least one pressure variation behavior, it is noted. -formed time, if a pore movement of one or more pores takes place inside the matrix material. The pores are formed, for example, during the dissolution of a substantially stationary gas inclusion within the matrix material, or they enter the fiber-based material to be impregnated by sealing defects on the tooling or in the vacuum system.

The inventors have found here that with regard to the internal pressure of the tool, it was possible to determine whether there is a pore movement, because such pore movements are reflected for example in the form of oscillations. , noises, pressure minima and / or pressure maxima in the respective pressure-time variation behavior of a sensor. There is always a characteristic deviation from a pressure-time variation behavior when essential parameters of the pressure-time behavior, which as a general rule can be considered as a kind of curve, vary significantly, that is to say that the variations of the parameters of the pressure-time curve are greater than a tolerable limit value. A minimum pressure or a maximum pressure of more than 0.1 bar in the space of a few seconds, for example in less than 10 seconds, is such a characteristic deviation for example, and makes it possible to conclude, for example, at the beginning of a pore movement inside the matrix material. This value is however to be considered only as an example and may depend on the size of the part and the injection pressure used. If necessary, it should be determined experimentally which characteristic deviations occur for a given injection pressure and part / workpiece geometry in the case of gas inclusions and artificially generated pore or pore movements. For the purposes of the present invention, stationary gas inclusions denote the inclusion of a material in gaseous form, for example outside air or degassing of the materials used, which is formed by a closed flow front of the material of matrix within the fiber-based material. The stationary gas inclusions here occupy substantially a fixed position, i.e. there is no significant change in local positions with respect to the position of the fiber-based material. Such gas inclusions are also called -dry-spot- or dry areas.

For the purposes of the present invention, a gas pore or pore designates a small cavity inside the matrix material, which is formed for example by the dissolution of a gas inclusion. Such pores can appear here during the dissolution of a stationary gas inclusion in the form of the gas stationary inclusion layers, the pores generally moving in the direction of the pressure gradient, i.e. say away from the pressure connection or pressure source. Here we often observe a narrow branching of the pores. But the pores can also arise due to leaks in the tooling or leaks in the injection system. A pore is thus, relative to the part, a very small gas inclusion, which often has an elongated structure.

It has been found that such a pore movement could be identified in the pressure-time variation behavior of the sensors arranged on the tooling, because the pressure-time variation behavior exhibits characteristic deviation properties, which are in clear and close correlation with the movement of pores. The identification of a characteristic deviation can, for example, also be performed by comparing the pressure-time variation behavior with an idealized pressure-time variation behavior, defined by a pressure-time variation behavior of the pressure sensor respectively considered, without pore movement in the matrix material. A deviation exceeding a respective critical limit value with respect to such idealized pressure variation behavior, can be identified as a characteristic deviation to conclude pore movement.

Advantageously, the characteristic deviation in at least one pressure-time variation behavior having been formed is identified by curve oscillations, curve noises, pressure minima and / or pressure maxima in the variation behavior. respective pressure-time. The pressure and / or pressure minima must here be outside a tolerable limited value, to be identified as a characteristic deviation, because smaller deviations in the pressure-time variation behavior can not be detected. allow us to conclude indisputably with a movement of pores. Oscillations of the curve here in particular designate alternating amplitude variations beyond a tolerated limit value, the amplitudes here reproducing the pressure parameter of the pressure-time variation behavior. A noise of the curve here in particular designates the superposition of numerous harmonic curve oscillations, the amplitude here also representing the internal pressure of the tooling. In other words, in the case of curve oscillations or curve noises, variations in the internal pressure of the tool are considered as the amplitude of an oscillation outside a tolerable limit value. alternating variation of the internal pressure of the tooling to unequivocally conclude a pore movement within the matrix material.

In another advantageous embodiment, an end of a characteristic deviation having been identified in at least one pressure-time variation behavior formed is identified by the fact that the characteristic deviation can no longer be observed in the variation behavior. pressure-time, and then, depending on the identified end of an identified characteristic deviation, the end of the pore movement having been noted. The beginning and the end of a pore movement can thus be deduced from the characteristic deviation inside the pressure-time variation behavior, the end of a pore movement can also mean the dissolution of said one or several pores.

Such information is advantageously stored in a data store for subsequent protocol and evidence purposes. According to another advantageous embodiment, it is determined as a function of the position of the pressure sensors with respect to the fiber-based material and the characteristic deviations of several pressure-time variation behaviors, a direction of the pore movement, so that it is possible not only to note the movement of pores in itself, but also its concrete direction. Since the pressure sensors are arranged spaced apart from each other within the injection zone, information about the direction of pore movement can be deduced therefrom. The direction of movement of the pore movement is advantageously determined by the data processing unit.

Advantageously, it is now possible, when identifying a pore movement, and possibly also at the end of the pore movement, to adjust or adapt the process parameters of the injection process, so as to be able to react in this way. the special conditions concerning the inclusion of gases and the pores formed therein. Thus, it is possible, for example, to imagine that, in the case of identification of a pore movement, the injection pressure is continuously increased until the end of the pore movement is observed, so as to be able to for example to bring back to a preset standard value, an injection pressure that had been increased. This increases the quality of the part and reduces the scrap.

Advantageously, the formation or dissolution of a gas inclusion is noted by the data processing unit, as a function of at least one identified characteristic deviation.

Advantageously, the process parameters of the injection process are adjusted or adapted by the data processing unit according to the observation of a pore movement or the observation of the end of the pore movement.

It is thus possible for the first time to detect a movement of pores, and to be able to adjust and adapt the process parameters of the injection process accordingly during the manufacture of the fiber-reinforced composite part, with a view to increasing the quality of parts and reduce a possible series dispersion.

Furthermore, the aim is also achieved according to the invention, thanks to the evoked installation, the installation comprising a shaping tool in the injection zone of which are provided a plurality of pressure sensors, configured to measure the internal pressure of the tooling within the injection zone, and there is provided a data processing unit configured to form the pressure-time variation behaviors as well as to identify characteristic deviations and pore movements.

Advantageously, the installation according to the invention is configured according to one or more of the aforementioned developments of the method. The invention will be explained in more detail by way of example, with reference to the appended figures. These show:

Figure 1 schematic representation of an installation according to the invention;

Figure 2 diagram of several pressure-time variation behaviors and their characteristic deviations.

FIG. 1 schematically shows the method of construction of an installation 10, configured for the manufacture of a fiber-reinforced composite part by means of an injection method. The installation 10 comprises for this purpose a shaping tool 11 having an injection zone 12 in which is introduced the fiber-based material (not shown). The injection zone 12 is then generally covered by a vacuum sheet (also not shown), and thus sealed in a vacuum-tight manner.

In the injection zone 12 are arranged several pressure sensors Si to Se configured to measure the internal pressure of the tooling inside the injection zone 12.

A casting inlet opening 13 provided in the tool 11 is communicatively connected to a matrix material 14 prepared outside the injection zone 12. facility capable of controlling the injection pressure and other process parameters.

Furthermore, the installation 10 comprises, according to the invention, a data processing unit 16, which is in connection with the sensors Si to Se, and which is provided according to the invention to form, from measured values as a function of time, of the individual sensors, a respective pressure-time variation behavior, with a view to analyzing these pressure-time variation behaviors as to the presence of characteristic deviations, and to ascertain whether produces a pore movement. The data processing unit 16 is also connected to an installation command 15, in order to be able to influence, for example, the process parameters during the injection of the matrix material 14, as a function of a pore movement observed. .

In the embodiment of FIG. 1, there is also provided, at the end opposite the casting entry opening 13, a suction opening 17 connected to a vacuum pump 18. thus to produce and maintain a vacuum before the injection of the matrix material 14 as well as, if necessary, also during the injection.

FIG. 2 shows, by way of example, a pressure-time variation behavior diagram Vi to V3 of three sensors. Initially, in the injection zone, a vacuum of less than 0.1 bar was set.

It can be seen that up to about 50 seconds the pressure-time variation behaviors V1 to V3 are substantially superimposable and the pressure in the injection zone increases continuously.

But from about 50 seconds, characteristic deviations 20 appear within the pressure-time variation behaviors Vi to V3, which can be identified in particular by oscillations and noises in the pressure-time variation behaviors V1 at V3 outside a tolerable limit range.

This characteristic deviation now shows in accordance with the invention that pore movement has been established in the matrix material 14, i.e. the pores which have formed during the dissolution of a substantially stationary gas inclusion, began to move at the instant corresponding to about 50 seconds. From about 100 seconds, this pore movement is completed, which can occur for example following the dissolution of the pores or the dry zone or "dry-spot".

The characteristic deviations in the pressure-time variation behaviors V1 to V3 as well as their characteristic properties may depend inter alia on the part geometry, the injection pressure as well as the fiber-based material and the matrix material used. . It has been found appropriate to first determine, when operating in test mode under the same boundary conditions as the future production, with an inclusion of artificially generated gas, the characteristic properties of the characteristic deviations 20, and then to transpose them. to subsequent series production.

Marking nomenclature: 10 Installation 11 Tooling 12 Injection area 13 Casting inlet 14 Matrix material 15 Installation control 16 Data processing unit 17 Suction opening 18 Vacuum pump 20 Characteristic deviation

Si-Se Pressure Sensors

Vi to V3 Pressure-time variation behaviors (curves)

Claims (9)

Claims: A method for manufacturing a fiber-reinforced composite part by an injection process in which a matrix material (14) is injected into a fiber-based material and the matrix material (14) having been injected is cured the method comprising the steps of: a) introducing a fiber-based material into an injection zone (12) of a forming tool (11), and preparing a matrix material (14) to the outside the injection zone (12), in a reservoir communicatively connected to the injection zone (12), b) producing a pressure difference between the matrix material (14) and the injection zone ( 12) so that an injection pressure acts on the matrix material (14), and that the matrix material (14) is injected into the fiber-based material having been introduced into the injection zone (12). ), characterized by c) measuring the internal pressure of the within the injection zone (12) by means of one or more pressure sensors (Si to Se) during and / or after injection of the matrix material (14), so as to determining a large number of measurement values for each pressure sensor (Si to S8), d) forming pressure-time variation behaviors of the internal pressure of the tooling for each pressure sensor (Si to Se) as a function of measuring values of the respective pressure sensor (Si to S8), using a data processing unit (16), and e) identifying at least one characteristic deviation in at least one pressure-time variation behavior formed and detecting a pore movement of one or more pores within the matrix material as a function of an identified deviation in at least one pressure-time variation behavior by the data processing unit. 2. Method according to claim 1, characterized in that the characteristic deviation is identified in at least one pressure-time variation behavior with respect to an idealized pressure-time variation behavior, the idealized pressure-time variation behavior being formed. by a pressure-time variation behavior of the respective pressure sensor (Si to S8), without pore movement in the matrix material. 3. Method according to claim 1 or 2, characterized in that the characteristic deviation in at least one pressure-time variation behavior that has been formed is identified by curve oscillations, noise of the curve, pressure minima. and / or pressure maxima in the respective pressure-time variation behavior. 4. Method according to one of the preceding claims, characterized in that it identifies an end of a characteristic deviation having been identified in at least one pressure-time variation behavior formed, and it is found, depending on the end identified with a characteristic deviation identified, the end of the pore movement having been noted. 5. Method according to one of the preceding claims, characterized in that depending on the position of the pressure sensors (Si to S8) relative to the fiber-based material and the characteristic deviations of several pressure-time variation behaviors , the data processing unit determines a direction of movement of the pore movement. 6. Method according to one of the preceding claims, characterized in that according to at least one identified characteristic deviation, the data processing unit observes the formation or dissolution of a gas inclusion. 7. Method according to one of the preceding claims, characterized in that depending on the finding of a pore movement or the observation of the end of the pore movement, the data processing unit (16) rule or fits the process parameters of the injection process. A plant (10) for manufacturing a fiber-reinforced composite part by an injection process in which a matrix material (14) is injected into a fiber-based material and the matrix material (14) having been injected is cured, the installation comprising a) a forming tool (11), having an injection zone (12) into which the fiber-based material can be introduced and communicatively connected to a reservoir for the storing the matrix material (14), characterized in that b) one or more pressure sensors (Si to S8) are provided for measuring the internal pressure of the tooling within the injection zone (12), and c) there is provided a data processing unit (16) connected to the pressure sensors (Si to S8), configured to form pressure-time variation behaviors of the internal pressure of the tooling for each pressure sensor n (Si to S8) as a function of the measurement values of the respective pressure sensor (Si to S8), and to identify at least one characteristic deviation in at least one pressure-time variation behavior formed, and to observe a pore movement of one or more pores within the matrix material as a function of an identified deviation in at least one pressure-time variation behavior. 9. Installation (10) according to claim 8, characterized in that the installation is designed for the implementation of the method according to one of claims 1 to 7.