WO2013076312A1 - Procédé et dispositif pour déterminer la température de transition vitreuse d'un produit - Google Patents

Procédé et dispositif pour déterminer la température de transition vitreuse d'un produit Download PDF

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Publication number
WO2013076312A1
WO2013076312A1 PCT/EP2012/073649 EP2012073649W WO2013076312A1 WO 2013076312 A1 WO2013076312 A1 WO 2013076312A1 EP 2012073649 W EP2012073649 W EP 2012073649W WO 2013076312 A1 WO2013076312 A1 WO 2013076312A1
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WO
WIPO (PCT)
Prior art keywords
blade
voltage
glass transition
transition temperature
location
Prior art date
Application number
PCT/EP2012/073649
Other languages
English (en)
Inventor
Erik Jan DE JONG
Original Assignee
Se Blades Technology B.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Se Blades Technology B.V. filed Critical Se Blades Technology B.V.
Publication of WO2013076312A1 publication Critical patent/WO2013076312A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/221—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance by investigating the dielectric properties
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/44—Resins; Plastics; Rubber; Leather
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/44—Resins; Plastics; Rubber; Leather
    • G01N33/442—Resins; Plastics
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00—Investigating or analyzing materials by the use of thermal means
    • G01N25/02—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering
    • G01N25/04—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering of melting point; of freezing point; of softening point

Definitions

  • the invention relates to a method for determining the glass transition temperature of a product, in particular a wind turbine blade, comprising a composite material.
  • the glass transition temperature is a useful indicator. This glass transition temperature is the temperature at which the characteristic of the material changes from "glass-like", i.e. relatively stiff and brittle, to "rubber-like", i.e. relatively elastic and flexible.
  • the glass transition temperature of a composite material is found to be lower than expected, this is an indication of insufficient cross-linking or curing of the resin. This may be caused e.g. by deviations in the composition of the resin by insufficient mixing of the components of the resin. Insufficient cross-linking or curing results in a reduction in strength and/or stiffness of the composite material.
  • the glass transition temperature of a composite material has been determined by a technique known as Differential Scanning Calorimetry (DSC).
  • DSC Differential Scanning Calorimetry
  • This technique involves taking a sample of the composite material and a sample of a reference material.
  • the reference sample should have a well-defined heat capacity over the range of temperatures to be scanned. Both samples are then heated and the difference in the amount of heat that is required to increase the temperature of the composite sample and the reference is measured as a function of temperature.
  • the basic principle underlying this technique is that when the sample undergoes a physical transformation such as glass transition, more or less heat will need to flow to it than the reference to maintain both at the same temperature.
  • a differential scanning calorimeters measures the amount of heat absorbed or released during glass transition. When the results of such measurements are represented graphically, the glass transition is shown as a peak.
  • the conventional DCS technique has the drawback that it requires a sample to be taken from the product, thus damaging the product. Moreover, the DSC technique is relatively time- consuming and does not lend itself to inspections in the field.
  • the present invention provides a method for determining the glass transition temperature of a product, in particular a wind turbine blade, comprising a composite material, the method comprising: a) applying an alternating voltage to a first location on the blade;
  • Performing measurements of an alternating voltage applied to a product at various temperatures allows the glass transition temperature to be determined without the need to take a sample from the product. I.e. this is executed in such that complex impedance or capacitance of the material to be measured can be determined while maintaining the appearance and structural integrity of the product.
  • the method which can be performed relatively swiftly, is suited for determining the glass temperature in the field, which is particularly advantageous when monitoring large structures like wind turbine blades.
  • step c) includes heating said part of the blade to a maximum temperature, while the method further includes: f) letting the blade cool down from said maximum temperature;
  • step e) includes comparing the measured voltage with the applied voltage at predetermined temperatures to determine an amount of attenuation and a phase shift between the respective voltages at each of said temperatures.
  • step e) may include using the attenuation and phase shift to determine a capacity or derivatives of those measurements like the complex impedance and/or capacitance of the material between the first and second locations at each of said temperatures, and observing variations in said capacity to determine the glass transition temperature.
  • the capacity as a function of the temperature can be illustrated in a graph, where the glass transition temperature will be clearly indicated by a sudden increase in the slope of the graph.
  • step e) may include determining a flexibility of dipoles within the material between the first and second locations at predetermined temperatures, and observing variations in said dipole flexibility to determine the glass transition temperature.
  • the flexibility of the dipoles in the material changes abruptly at the glass transition temperature, presenting yet another clear indication of this material characteristic.
  • the alternating voltage is applied by a first electrode arranged on the blade at the first location and the resulting voltage is measured by a second electrode arranged on the blade at the second location.
  • the first and second electrodes may be arranged at a predetermined mutual distance, so that the results of the measurements are comparable. This may be achieved by holding the first and second electrodes in a mutually fixed relationship.
  • the electrodes are placed very close to each other and configured to work as capacitor while the voltage is applied to one part of the capacitor and the induced voltage is measures in the other part of the capacitor. By this the characteristics of the dielectric placed in the surrounding of the electrodes, respectively capacitor very much influences the measured voltage.
  • the voltage measured represents the dielectric which again represents the electrical properties of the material surrounding the electrodes; analogous to details mentioned above this can be used to determine the glass transition temperature of the very location of the blade.
  • the part of the blade between the first and second locations is heated by resistive heating.
  • Electrical heating can efficiently be combined with the electrical measurements.
  • a heating current may be supplied to the blade at a different frequency than the alternating voltage.
  • the steps a) to e) are repeated at various pairs of first and second locations on the blade. In this way the amount of curing or cross-linking may be monitored at various points on the blade.
  • the measurement of the glass transition temperature may be used to determine the quality of the composite material.
  • the invention further relates to a device for determining the glass transition temperature of a product, in particular a wind turbine blade, comprising a composite material.
  • a conventional device for performing such determinations is a differential scanning calorimeter.
  • this is a device that is only suited for use in a laboratory and requires that a sample be taken from the product to be examined.
  • a glass transition temperature determining device which comprises: a) means for applying an alternating voltage to a first location on the blade;
  • the device of the invention performs a non-destructive measurement of the glass transition temperature. Moreover, the device can be used in the field. This is especially advantageous for products which represent a substantial capital investment, like wind turbine blades, since it allows the amount of down-time to be reduced.
  • the heating means are arranged to be rendered inoperative after heating said part of the blade to a maximum temperature, and the voltage applying means, the voltage measuring means and the analysing means are arranged to remain operative after the heating means have been rendered inoperative. This allows a second non-destructive measurement to be performed after the blade has been locally subjected to additional heating, which may lead to an even more accurate determination of the glass transition temperature.
  • the analysing means are arranged for comparing the measured voltage with the applied voltage at predetermined temperatures to determine an amount of attenuation and a phase shift between the respective voltages at each of said temperatures. More specifically, the analysing means may be arranged for using the attenuation and phase shift to determine a capacity of the material between the first and second locations at each of said temperatures, and the analysing means may further be arranged for observing variations in said capacity to determine the glass transition temperature.
  • the analysing means are arranged for determining a flexibility of dipoles within the material between the first and second locations at predetermined temperatures, the analysing means further being arranged for observing variations in said flexibility to determine the glass transition temperature.
  • the voltage applying means may include a first electrode to be arranged on the blade at the first location and the voltage measuring means may include a second electrode to be arranged on the blade at the second location.
  • the device may comprise a frame in which the first and second electrodes are mounted at a predetermined mutual distance.
  • the heating means may include an electric current supply.
  • This current supply may be connected to the first and second electrodes and may be arranged to supply current at a different frequency than the alternating voltage.
  • the device may comprise a grip for manually holding the device to the blade.
  • the analysing means may be arranged for using the glass transition temperature to determine the quality of the composite material.
  • Figures 2A and 2B show a simplified representation of cross-linking in a resin of a composite material, wherein Figure 2A illustrates a situation wherein cross-linking is incomplete,
  • Figure 3 is a graph showing the change in the stiffness of thermoplastic and thermosetting materials at the glass transition temperature
  • Figure 4 shows an alternating current that is supplied to the material at a first location and the current that is measured at a second location, illustrating the phase shift and damping of the current
  • Figure 6 is a graph showing the capacity of the material as a function of the temperature, indicating the glass transition temperature
  • Figure 7 is a schematic drawing of a handheld device for determining the glass transition temperature
  • Figure 7A is an exploded view of the electrodes and heating means of this device.
  • a blade 1 for a wind turbine comprises a bottom skin 2 and a spar 3.
  • the blade 1 also comprises a top skin, which is not shown for reasons of clarity.
  • the blade 1 may have a span S from root 4 to tip 5 that amounts to several tens of meters and a chord C from leading edge 6 to trailing edge 7 that may be several meters long.
  • it is important that the blade 1 be sufficiently strong and stiff. Wind turbine blades are designed for a long service life, for example twenty years, during which their structural integrity must be ensured.
  • wind turbine blades are mounted relatively close to the tower supporting the nacelle, the blades must have sufficient stiffness to maintain a safe clearance between the blades and the tower.
  • wind turbine blades are comparatively slender and thin, which makes it particularly challenging to achieve the required strength and stiffness. This imposes stringent requirements on the structural design and the materials used in manufacturing wind turbine blades.
  • Blades for wind turbines are normally made from a fibre reinforced composite material.
  • a fibre reinforced composite material can be designed to be strong, stiff and lightweight.
  • a composite material consists of a resin in which the reinforcing fibres are embedded.
  • the resin is a polymer material that includes a hardener of cross-linking agent. When the resin is cured, cross-links are formed which provide the material with strength and stiffness. However, it is conceivable that for some reason the resin will not cure sufficiently during manufacture of a blade.
  • the glass transition temperature Tg of the material is determined. This is the temperature where Young's modulus E of the material abruptly decreases, thus signaling a fundamental change in the characteristics of the material from "glassy” to "rubbery” ( Figure 3). If this glass transition temperature Tg is found to be too low, that is an indication of insufficient curing or cross- linking, signaling that the material will lack sufficient strength and/or stiffness to withstand the loads to which the wind turbine blade 1 is subjected.
  • the glass transition temperature Tg of the material is determined in a non-destructive manner. This prevents the blade 1 from being damaged in the test and allows the determination to be performed at the location where the blade 1 is in use.
  • the material is subjected to an oscillating electrical field while being heated, and the response of the material at various different temperatures is measured and analysed to determine the glass transition temperature Tg.
  • An alternating voltage Vi is applied to the material at a first location on the blade 1 , and a resulting voltage Vo is measured at a second location that is spaced a predetermined distance from the first location. The first and second locations will be selected such that the measurements are representative for a substantial part of blade 1 .
  • the input voltage Vi has greater amplitude than the output voltage Vo.
  • the output voltage Vo has undergone a phase shift At with respect to the input voltage Vi.
  • the amount of damping or attenuation of the voltage AV and the phase shift At can be measured and used to calculate the capacity C of the material between the first and second locations.
  • a mathematical model is used in which the properties of the material are simulated by a first order filter.
  • This filter model consists of a resistor and a capacitor.
  • the measured values of damping AV and phase shift At can be used to calculate the values of the resistance R and capacity C of the modeled filter that would have led to a similar response to the input voltage Vi.
  • the attenuation AV and phase shift At will vary with the temperature T of the material, and so will the capacity C. This is due to temperature dependent variations in the flexibility of dipoles that are present in the material.
  • the temperature dependency of the capacity C of the material is illustrated in Figure 6.
  • the graph of capacity C as a function of temperature T has two branches; a lower branch 8A showing the increase in capacity C when the material is heated (arrow I) and an upper branch 8B showing the decreasing capacity C when the material cools down again (arrow II).
  • the lower branch 8A of the graph shows a fairly abrupt change in the inclination of the curve at a temperature T of about 1 10 degrees Celsius. This change signifies that the glass transition temperature Tg has been reached.
  • the upper branch 8B has an abrupt change of inclination at the temperature T of approximately 120 degrees Celsius. This signifies another, higher value of the glass transition temperature Tg. This latter value represents the maximum glass transition temperature Tgmax of the fully cured product.
  • the reason for the discrepancy between the glass transition temperatures Tg found during heating and during subsequent cooling is that when the material is not yet fully cured, heating of the material during the first measurement will result in additional curing. Therefore, the second measurement during cooling is performed on a material that is more fully cured than the first measurement. If the first measurement yields a glass transition temperature Tg that is too low, this may be rectified by reheating the product. However, if the second measurement yields a glass transition temperature Tgmax that is too low, this indicates a fundamental flaw in the composition of the material that will lead to rejection of the product.
  • the alternating voltage is applied by a first electrode 9, while the resulting voltage is measured by a second electrode 10.
  • the two electrodes 9, 10 are brought into contact with the material at two locations which are spaced apart a predetermined distance.
  • the electrodes 9, 10 are placed side-by-side on the surface of the blade 1.
  • the measurement is performed while the material is being heated.
  • resistive heating is used, since this is easily compatible with the application of an oscillating voltage.
  • other techniques for heating the material like e.g. by radiation, are also conceivable.
  • the illustrated embodiment of the invention provides a frame 1 1 carrying the electrodes 9, 10.
  • Figure 7 A shows the electrodes 9, 10 mounted in the annular frame 1 1 in an intermeshing arrangement.
  • the frame 1 1 is arranged at the tip 12 of a handheld device 13.
  • the device 13 also includes heating means 14, which in this embodiment are formed by a resistive heater element 15.
  • This heater element 15, which is spiral-shaped, is connected to an alternating current supply.
  • This current supply operates at a different frequency than the voltage supply which provides the alternating voltage to the first electrode 9.
  • the device 13 further includes a temperature sensor 17, which in the illustrated embodiment is arranged between the heating means 14 and the voltage applying and measuring electrodes 9, 10.
  • the first and second electrodes 9, 10, the temperature sensor 17 and the heating means 14 are all connected to a printed circuit board 21 by means of wiring 18, 19, 20.
  • the board 21 includes electronic circuitry for controlling operation of the first and second electrodes 9, 10 and the heating means 14.
  • the board 21 further includes electronic circuitry for comparing a measured voltage signal Vo from the second electrode 10 with an applied voltage signal Vi from the first electrode and for analysing the results of this comparison.
  • These electronic circuits may be arranged to determine a phase shift At and an amount of damping or attenuation AV and to use these measurements to determine a capacity C of the material.
  • the electronic circuitry may further be arranged to observe variations in the capacity C as a function of the temperature T that is measured by the sensor 17 in order to determine the glass transition temperature Tg of the material.
  • the electronic circuitry on the board 21 may be connected to output means, e.g. a display, which may form part of the device 13.
  • the electronics may be connected to an output terminal, e.g. a USB port, for connection to an external device, like a display or a printer.
  • an external device like a display or a printer.
  • the further processing and analysis of the measurements is done externally, e.g. on an external computer or workstation.
  • the electronic circuitry on the board 21 is only required to control the input and output voltages Vi, Vo of the first and second electrodes 9, 10. Communication with external devices may be done through a wired or a wireless connection. In the latter case the device 13 will include a transceiver.
  • Power for operating the device is supplied by power supply means 22.
  • the power supply means include a plurality of batteries 23.
  • the device it is also conceivable for the device to be connected to an external power supply, e.g. through a mains connector.
  • the device 13 In operation the device 13 is held with its tip 12 against the material to be monitored, such that the electrodes 9, 10 lie flat on the surface of the material. Then an alternating voltage Vi is applied to the material through the first electrodes, and after passing through part of the material the resulting voltage Vo is received at the second electrodes. This received voltage Vo is transferred to the measuring and analyzing means.
  • the heating means 14 are operative to apply a heating current to the material through the heater element 15. In this way a zone of the material that is bounded by the frame 1 1 is heated. The amount of heating and the resulting temperature of the material is sensed by the temperature sensor 17 and is used both to control the current supply and to provide a temperature basis for the measurement and analysis.
  • the results of the measurements and analysis are finally presented either graphically or in the form of a discrete value of the glass transition temperature.
  • the glass transition temperature of a material may be swiftly and reliably determined in a non-destructive manner.
  • the determination which gives a reliable indication of the strength and/or stiffness of the material, may be performed in the field.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
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  • Physics & Mathematics (AREA)
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  • General Health & Medical Sciences (AREA)
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  • Engineering & Computer Science (AREA)
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Abstract

L'invention concerne un procédé permettant de déterminer la température de transition vitreuse d'un produit, en particulier une pale d'éolienne, comprenant un matériau composite. Il est donc nécessaire de faire appel à un procédé non destructif pour déterminer la température de transition vitreuse qui peut être réalisé relativement rapidement et in situ. À cette fin, la présente invention propose un procédé et un dispositif permettant de déterminer la température de transition vitreuse d'un produit, en particulier une pale d'éolienne, comprenant un matériau composite, le procédé consistant à appliquer une tension alternative sur un premier emplacement de la pale, à mesurer une tension obtenue à un second emplacement de la pale, à chauffer au moins une partie de la pale entre les premier et second emplacements, à répéter les deux premières étapes à différentes températures et à analyser les mesures afin de déterminer une température à laquelle une propriété diélectrique de la pale subit une variation. La réalisation des mesures d'une tension alternative appliquée sur un produit à différentes températures permet de déterminer la température de transition vitreuse sans avoir à prélever un échantillon du produit. Ceci est effectué de telle manière que l'impédance ou la capacitance complexe du matériau à mesurer peut être déterminée tout en conservant l'apparence et l'intégrité structurale du produit. Ainsi le procédé, qui peut être réalisé relativement rapidement, est approprié pour déterminer in situ la température de transition vitreuse, ce qui est particulièrement avantageux lorsque l'on contrôle de grandes structures telles que des pales d'éoliennes.
PCT/EP2012/073649 2011-11-25 2012-11-26 Procédé et dispositif pour déterminer la température de transition vitreuse d'un produit WO2013076312A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL2007873A NL2007873C2 (en) 2011-11-25 2011-11-25 Method and device for determining the glass transition temperature of a product.
NL2007873 2011-11-25

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WO2013076312A1 true WO2013076312A1 (fr) 2013-05-30

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Cited By (3)

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Publication number Priority date Publication date Assignee Title
RU2564520C1 (ru) * 2014-07-15 2015-10-10 Общество С Ограниченной Ответственностью "Бийский Завод Стеклопластиков" Способ определения термомеханических характеристик полимерных композиционных материалов
US9271526B2 (en) 2013-05-28 2016-03-01 Huizhou Kimree Technology Co., Ltd., Shenzhen Branch Electronic cigarette box
CN113791110A (zh) * 2021-09-15 2021-12-14 苏州热工研究院有限公司 一种风力发电机组叶片玻璃化转变温度的测定装置及方法

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JP2009281918A (ja) * 2008-05-23 2009-12-03 Osaka Gas Co Ltd 劣化判定方法及び劣化判定装置

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9271526B2 (en) 2013-05-28 2016-03-01 Huizhou Kimree Technology Co., Ltd., Shenzhen Branch Electronic cigarette box
RU2564520C1 (ru) * 2014-07-15 2015-10-10 Общество С Ограниченной Ответственностью "Бийский Завод Стеклопластиков" Способ определения термомеханических характеристик полимерных композиционных материалов
CN113791110A (zh) * 2021-09-15 2021-12-14 苏州热工研究院有限公司 一种风力发电机组叶片玻璃化转变温度的测定装置及方法

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