DE102017007197A1 - Method for producing a component in the vacuum infusion method - Google Patents

Abstract

The invention relates to a method for producing a component having a hardening material in the vacuum infusion method, in particular of rotor blades or rotor blade parts, wherein the component cures in a heated mold. According to the invention, the degree of curing or a property corresponding to the degree of curing of the component is determined during the curing and, depending on this, the heating of the mold is regulated.

Description

The invention relates to a method for producing a component having a hardening material in the vacuum infusion method, in particular of rotor blades or rotor blade parts, wherein the component cures in a heated mold.

Plastic components typically cure in a mold. To support the curing process, the mold is heated. Thereby a lot of energy is spent.

Large components made of fiber composite plastics, such as rotor blades (in particular for wind turbines), are produced in correspondingly large, heated molds, preferably in the VARI process (Vacuum Assisted Resin Infusion) or a similar process. The material in the mold cures under a vacuum film while the mold is being heated. Therefore, in the present case, the VARI method is also regarded as a vacuum infusion method.

Object of the present invention is to provide a method and a mold with which an energy-saving and high-quality production of a component with hardening material in the vacuum infusion process are possible.

To achieve the object, the inventive method has the features of claim 1. In particular, it is provided that the degree of hardening or a property corresponding to the degree of hardening of the component are determined during hardening and, depending on this, the heating of the mold is regulated. In this way, an automatic heating control is possible, as well as an optimization of the infusion or curing time. The process according to the invention is preferably used in conjunction with the VARI process and / or in the production of rotor blades.

• - die Reaktionsenthalpie des aushärtenden Werkstoffs,
• - den lokalen Aufbau des Bauteils (Dicke, Anzahl der Lagen Fasermatten),
• - den Infusionsprozess,
• - den Aufbau der Form,
• - eine Isolation,
• - Außentemperatur Taußen,
• - Wärmeleitung in Form und Bauteil, und/oder
• - Versuchsergebnisse.

The control of the heater according to the invention, in addition to the degree of cure and other parameters and measures taken into account, such

• the reaction enthalpy of the hardening material,
• the local structure of the component (thickness, number of layers of fiber mats),
• - the infusion process,
• - the structure of the form,
• - an isolation,
• - outside temperature Taußen,
• - Heat conduction in the form and component, and / or
• - Test results.

As a result, the control can also include a prediction function. For example, the heat output or its rise can be reduced before the desired degree of cure is achieved, because the enthalpy of reaction introduces additional heat energy, the effect of which can be estimated by tests and / or the local structure, outside temperature, heat conduction and insulation.

According to a further aspect of the invention, the degree of curing is determined at least indirectly by one or more sensors, in particular by measuring strain, temperature, electrical resistance, ion viscosity, reflection or Bragg wavelength. Sensors for the specified physical values are known in principle. The Bragg wavelength is determined using so-called fiber Bragg grating sensors. The aim is to determine the strain and / or temperature derived from the Bragg wavelength.

According to a further aspect of the invention, the degree of curing is determined at least indirectly by one or more sensors arranged on the component, in particular by at least one sensor arranged under a vacuum film. This also includes sensors that abut the component, which are inserted into the component, as well as in a component surface, or sensors without direct contact with the component, such as sensors close to the component surface. The sensors provide the data for a control unit for automatic control of the heating. The sensor should be as reusable as possible and is separated after completion of the process from the component, for example, demolished.

According to a further aspect of the invention, the sensor is located on a layer covering the component, in particular on a layer as a flow aid or on a layer as a separating aid. At least one layer is located between sensor and component.

According to a further aspect of the invention, the sensor is arranged under a vacuum film, wherein the sensor protrudes with a partial region through an opening in the vacuum film, and wherein the opening and sensor are sealed against each other. A portion of the sensor is located under the vacuum film, while the other portion protrudes from the opening. The protruding portion may also be a lead, but preferably a portion of a sensor housing.

According to a further aspect of the invention, the degree of cure is determined at least indirectly by one or more sensors arranged on the mold, in particular in conjunction with at least one sensor on the component. These include sensors that are inserted into the mold, as well as into a surface of the mold. The sensors provide the data for a control unit for automatic control of the heating.

According to a further aspect of the invention, the mold has a plurality of heating fields which are regulated separately, in groups or together. This makes it possible to heat different areas of the mold in different ways. Preferably, one or more sensors are provided per heating field. However, it is also possible to use a sensor for several heating fields, for example if the heat conduction in the component is calculable or known from empirical values.

According to a further aspect of the invention, it is provided that the component has fiber composite plastics, in particular with EP (epoxy resin), UP (unsaturated polyester resin) or VE (vinyl ester resin). These materials are known and used for the manufacture of rotor blades.

According to a further aspect of the invention, the component has fiber composite plastics, as GFRP (glass fiber reinforced plastics) or CFRP (carbon fiber reinforced plastics). The processing of GRP and CFRP is proven, especially for the production of rotor blades.

The invention also provides a mold for producing a component with hardening material and with the features of claim 10. In particular, a control unit for controlling the heating and at least one associated with the control unit sensor is provided, with the sensor of the degree of cure or one with the Cure degree of the component corresponding property can be determined. The control unit is integrated into the mold, associated with the mold or connected to the mold, for example via electrical or optical conductors. In the simplest case, a sensor, a control unit and a heater form a control loop. However, it is also possible to provide a plurality of sensors and / or a plurality of heating fields.

The heating of the mold may be formed in a known manner, such as with a system of channels in the mold for passing a heated or cooled fluid. Also, electrical heating / heating wires can be provided.

According to a further aspect of the invention, the degree of hardening can be determined at least indirectly with the sensor, in particular by measuring strain, temperature, electrical resistance, ion viscosity, reflection or Bragg wavelength.

According to a further aspect of the invention, the sensor is connected to the control unit but arranged outside the mold, namely on the component, for example in the component or on the component surface. The sensor is connected to the control unit via lines or via a wireless communication link, such as by radio.

According to a further aspect of the invention, at least one sensor is arranged on the mold, in particular on a mold surface. The sensor may also be provided below the surface, ie within the mold.

According to a further aspect of the invention, a plurality of heating fields are provided, which can be controlled together, in groups or separately.

• 1 Eine schematische Querschnittsdarstellung von Form und Bauteil mit Sensoren,
• 2 eine schematische Darstellung für eine Heizungsregelung während eines Vakuuminfusionsverfahrens,
• 3 eine Darstellung der Temperaturverläufe an einem Bauteil (a) und an einer Heizung (b),
• 4 eine Querschnittsdarstellung eines Sensors auf einem Bauteil und unter einer Vakuumfolie.

Further features of the invention will become apparent from the description, moreover, and from the claims. Advantageous embodiments of the invention are explained below with reference to claims. Show it:

• 1 A schematic cross-sectional representation of the form and component with sensors,
• 2 a schematic representation of a heating control during a vacuum infusion process,
• 3 a representation of the temperature profiles on a component (a) and on a heater (b),
• 4 a cross-sectional view of a sensor on a component and under a vacuum film.

It is based on a vacuum infusion process for the production of large-area components made of fiber-reinforced plastics. The components are preferably rotor blades for wind turbines, specifically rotor blade halves or rotor blade parts. For the production fiber mats are placed in a mold shell and covered by a vacuum film. Subsequently, resin flows under vacuum under the vacuum film and wets the fiber mats. Between fiber mats and vacuum film auxiliary layers can be provided, in particular a flow aid and a separating aid.

1 shows a resulting in this way component 10 in a form 11 or on a mold surface 12 , In the form 11 a heating system is integrated. Visible are heating pipes 13 for guiding a flowing heating medium (or cooling medium). The heating pipes 13 can be grouped into heating fields, in 1 For example, three heating fields, each with three heating pipes 13 ,

The heating system is with a regulation 14 equipped, in particular with an electronic control unit not shown in detail. With the scheme 14 linked are sensors 15 . 16 , The sensor 16 is in the mold surface 12 integrated and completes with this flush. The sensor 15 lies on the component 10 on.

Specifically, the sensor comes 15 during the vacuum infusion process on one component 10 lying situation. This is in particular a situation as a flow aid 17 for the resin and / or a layer as a separating aid 18 (Perforated film) and / or a layer as a tear-off fabric 19 , In 4 is below the layers 17 . 18 . 19 only one layer package 20 of the later component 10 located. This layer package 20 is impregnated with the resin in the vacuum infusion process.

The sensor 15 in 4 lies with a broad sensor head 21 under a vacuum foil 22 , There is a bottom 23 of the sensor head 21 at the position as a flow aid 17 at. After the end of the vacuum infusion process, the sensor becomes 15 from the situation 17 tore off. One to the sensor head 21 upwards following, narrow extension 24 extends through an opening 25 in the vacuum film 22 , From the extension 24 go a line 26 out to the scheme 14 connected.

The sensor head 21 is at its encircling top 27 with an adhesive seal 28 to the vacuum film 22 Mistake. Preferably, it is a sealing tape, also referred to as Tacky Tape.

As in 2 is represented by the scheme 14 and based on the from the sensors 15 . 16 provided values heating the mold 11 regulated. The aim is optimal control of the curing of the component 10 ,

• eine Reaktionsenthalpie ΔH des verwendeten Materials,
• die Wärmeleitung innerhalb der Form 11,
• die Wärmeleitung im Bauteil 10.

In addition to the values of the sensors 15 . 16 be in the scheme 14 considered further known parameters, in particular

• a reaction enthalpy ΔH of the material used,
• the heat conduction within the mold 11 .
• the heat conduction in the component 10 ,

The material used should harden so that the best possible properties are achieved for the finished component, in particular life, strength and elasticity under the intended conditions for the component. In order to achieve this hardening, testing is an ideal temperature curve 29 on or in the component 10 known, see 3a , The temperature T should reach a certain height, but not exceed this.

To the optimal temperature course 29 To adhere to is a certain heating of the mold 11 , ie a provision of heating power required in 3b represented by a nominal temperature 30 a mold heating.

In practice, due to a measured temperature profile 31 on the component 10 the of the scheme 14 set temperature of the mold heater - here as regulated temperature 32 designated - from the nominal temperature 30 differ. At the beginning of a curing time t, the regulated temperature 32 the mold heating continuously ramped up. This raises the component 10 a significant deviation of the measured temperature profile 31 from the optimal temperature profile 29 one. As a result, the scheme increases 14 the regulated temperature 32 , see short-term, significant increase I the regulated temperature 32 above the nominal temperature 30 in 3b ,

After another, weaker rise, the regulated temperature 32 kept constant, see plateau II in 3b , Meanwhile, the measured temperature increases 31 due to the reaction enthalpy in the component 10 continue on. This increase is known from experiments and from material properties and is under the regulation of temperature 32 considered as a prognosis of curing kinetics. Also taken into account are the known thermal properties of the mold 11 and the component 10 , in particular a heat transfer. In this way, the occurrence of too high measured temperatures 31 in the component 10 avoided. Energy consumption is minimized. Also, a cycle time for the curing of the component 10 Minimized in compliance with required material characteristics.

By arranging and using separately controlled heating fields in the mold 11 and respective associated sensors 15 . 16 can different areas of the component 10 be individually regulated.

After preserving the plateau II There is a further increase in temperature of the heater in the form 11 up to a plateau III to thereby measure the measured temperature 31 in the component 10 To be able to hold longer than would be possible only by the reaction enthalpy. Subsequently, the regulated temperature 32 lowered to a very low plateau IV. The measured temperature 31 follows with delay, due to the heat capacity of form 11 and component 10 and the time course of the reaction enthalpy in the component.

With the sensors 15 . 16 In particular, the temperature and / or an electrical resistance R are measured. The resistance R is a function of the temperature T _component and the degree of curing and thus the glass transition temperature T _{G of} the component 10 : $$R_{mess}=f\left(T_{Bauteil.}{T}_G\right)$$

Based on empirical values, the temperature profile on the component can be determined 10 Information about the beginning of the exothermic reaction and the progress of a crosslinking of the thermosetting material are taken.

For the mentioned temperature control a certain heating power P _{heating is} needed. This is a function of time and additionally depends on a number of parameters: $$\begin{array}{cc}{P}_{Heiz}& =f\left(t\right)\\ & =f\left(ReaktivitätdesHarzes.FOrmaufbau.IsOlatiOn.T_{außen}.AusHärteGrad...\right)\\ & =f\left(M_{SensOr1}.M_{SensOr2}.\Delta H.H\left(FOrm\right).H\left(Bauteil\right)\right)\end{array}$$

The reactivity of the hardening material (the resin) is described by the enthalpy ΔH and indicates how much heat is released during the reaction (during curing). The heat can be used to heat the component and thus reduce the required heating power of the mold.

The parameters h (shape) and h (component) take into account the heat conduction in the mold and in the component.

The current state of curing is determined by the sensor measurements M _{Sensor 1} and M _{Sensor 2} (here: the sensors 15 . 16 ).

Thus, the reaction kinetics and the reaction enthalpy are included in the heating control as fixed parameters. In addition, the local structure of the mold and the component is taken into account, since these significantly influence the heat transfer / heat transfer. So you can set the optimal heating power locally. The heating power is determined for each individual heating field.

The reaction kinetics / curing kinetics can be described as follows:

• - Prime-Modell $\frac{dp}{dt}=k{\left(1-p\right)}^n$
  
  oder dem
• - Prout-Tompkins-Modell $\frac{dp}{dt}=A\cdot e^{-\frac{E}{RT}}\cdot {\left(1-p\right)}^n\cdot p^a$
  

bestimmt werden. Hierbei ist:

• $\frac{dp}{dt}:$
  
  Reaktionsrate

• p: Aushärtegrad
• k: Arrhenius-Term
• n: Reaktionsordnung
• a: Katalyseordnung
• E: Aktivierungsenergie
• R: Allgemeine Gaskonstante
• e: Eulersche Zahl
• A: Arrhenius-Faktor

Is measured with the sensors only the temperature of the resin, z. B. on the surface of the component 10 under the vacuum film 22 , the degree of hardening of the component can 10 using approaches such as

• - Prime model $\frac{dp}{dt}=k{\left(1-p\right)}^n$
  
  or the
• - Prout-Tompkins model $\frac{dp}{dt}=A\cdot e^{-\frac{e}{RT}}\cdot {\left(1-p\right)}^n\cdot p^a$
  

be determined. Here is:

• $\frac{dp}{dt}:$
  
  reaction rate

• p: degree of cure
• k: Arrhenius-Term
• n: reaction order
• a: catalytic order
• E: activation energy
• R: General gas constant
• e: Euler's number
• A: Arrhenius factor

The targeted automatic control of the heating power minimizes the cycle time while maintaining the required material parameters (eg glass transition temperature T _G ). The measurement of the state of the component and the regulation take place in real time for each of the individual heating elements / heating fields. This means that sudden or locally occurring changes can be automatically taken into account. The predictive function (inclusion of the reaction enthalpy, empirical values) allows the heating power to be minimized at an early stage and the cooling of the component to begin, even if the curing is not yet complete, since the curing continues even at lower temperatures and is terminated.

The control of the mold automatically runs optimally for each individual heating field / heating element. This saves energy costs and significantly minimizes cycle times. At the same time, the control of the mold is fully automatic; no adjustment is required by the operator when the outside conditions change. Even slightly different material behavior with different batches of material is covered by the regulation.

LIST OF REFERENCE NUMBERS

10

component

11

shape

12

mold surface

13

heating pipes

14

regulation

15

Sensor (component surface)

16

Sensor (mold surface)

17

Location as a flow aid

18

Location as a separation aid

19

Location as a tear-off fabric

20

Location package

21

sensor head

22

vacuum film

23

bottom

24

extension

25

opening

26

management

27

top

28

seal

29

optimal temperature profile

30

nominal temperature

31

measured temperature profile

32

regulated temperature

I

short-term increase

II

plateau

III

plateau

VI

plateau

Claims (14)

Method for producing a component (10) with hardening material in the vacuum infusion method, in particular of rotor blades or rotor blade parts, the component (10) hardening in a heated mold (11), characterized in that the degree of hardening or a degree of hardening of the component (10 ) are determined during the curing and depending on the heating of the mold (11) is controlled. Method according to Claim 1 , characterized in that the degree of curing is determined at least indirectly by at least one sensor (15, 16), in particular by measuring strain, temperature, electrical resistance, ion viscosity, reflection or Bragg wavelength. Method according to Claim 1 or 2 , characterized in that the degree of cure is determined at least indirectly by at least one sensor (15) arranged on the component (10), in particular by at least one sensor (15) arranged under a vacuum film (22). Method according to Claim 2 or 3 , characterized in that the sensor (15) rests against a position covering the component (10), in particular at a position as a flow aid (17) or at a position as separation aid (18). Method according to Claim 2 or one of the further claims, characterized in that the sensor (15) is arranged under a vacuum film (22), that the sensor (15) protrudes with a partial region through an opening (25) in the vacuum film, and that opening (25) and sensor (15) are sealed from each other. Method according to Claim 1 or one of the further claims, characterized in that the degree of curing is determined at least indirectly by at least one sensor (16) arranged on the mold (11), in particular in connection with at least one sensor (15) on the component. Method according to Claim 1 or one of the further claims, characterized in that the mold (11) has a plurality of heating fields, which are regulated separately. Method according to Claim 1 or one of the further claims, characterized in that the component (10) comprises fiber composite plastics, in particular with EP (epoxy resin), UP (unsaturated polyester resin) or VE (vinyl ester resin). Method according to Claim 1 or one of the further claims, characterized in that the component (10) has fiber composite plastics, as GFRP (glass fiber reinforced plastics) or CFRP (carbon fiber reinforced plastics). Mold (11) for producing a component (10) with hardening material in Vakuuminfusionsverfahren, in particular of rotor blades or rotor blade parts, with a heater to support the curing of the material, characterized by a control unit (14) for controlling the heater and at least one with the control unit (14) linked sensor (15, 16), wherein the sensor of the degree of cure or a corresponding to the degree of curing of the component (10) property can be determined. Shape after Claim 10 , characterized in that with the sensor (15, 16) of the degree of curing at least indirectly determined by measuring strain, temperature, electrical resistance, ion viscosity, reflection or Bragg wavelength. Shape after Claim 10 or 11 , characterized in that the sensor (15) connected to the control unit (14) but outside the mold (11) is arranged, namely on the component (10). Shape after Claim 10 or one of the further claims, characterized in that at least one sensor (16) is arranged on the mold (11), in particular on a mold surface (12). Shape after Claim 10 or one of the further claims, characterized by a plurality of heating fields, which are separately, in groups or together controllable.

Images