|Publication number||US20080079425 A1|
|Application number||US 11/589,677|
|Publication date||Apr 3, 2008|
|Filing date||Oct 30, 2006|
|Priority date||Sep 29, 2006|
|Also published as||CN101657693A, CN101657693B, US7352194, WO2008037818A1|
|Publication number||11589677, 589677, US 2008/0079425 A1, US 2008/079425 A1, US 20080079425 A1, US 20080079425A1, US 2008079425 A1, US 2008079425A1, US-A1-20080079425, US-A1-2008079425, US2008/0079425A1, US2008/079425A1, US20080079425 A1, US20080079425A1, US2008079425 A1, US2008079425A1|
|Inventors||Antonio Fuente Souviron, Joaquin Pascual Fernandez|
|Original Assignee||Airbus Espana, S.L.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Classifications (4), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to a method for determining the thicknesses of coatings on composite materials by means of the application of induced currents.
Induced currents or Eddy currents (also known as parasitic currents or Foucault currents) are circulating electric currents induced by an alternating magnetic field in an insulated conductor. Eddy currents are not induced on an insulating material, the alternating magnetic field traversing the mentioned non-conducting material.
The use of induced currents is currently well known as a non-destructive test method for determining the thicknesses of a non-conducting coating on a conducting metal, or the thickness of a non-magnetic metal coating on a magnetic metal. However, currently there is no reliable method for the application of induced currents in the measurement of thicknesses on composite materials, such as carbon fiber, because this material, although it is a conductor, has a very low electric conductivity.
Other type of techniques, such as ultrasound techniques, have currently been proposed as non-destructive test methods for determining the thicknesses on composite materials, although this type of techniques use very complex equipment and have not provided reliable results.
The present invention is oriented to the solution of these drawbacks.
The present invention proposes an indirect measurement method for determining the thickness of a coating on a composite material, such as carbon fiber, comprising the following steps:
Other features and advantages of the present invention will be disclosed in the following detailed description of an illustrative embodiment of its object in relation to the attached figures.
The method for determining the thickness of a coating on a composite material, such as carbon fiber, developed by the present invention, consists of carrying out an indirect measurement considering the composite material or carbon fiber as a lift-off against a planar metal sheet, such as an aluminium alloy sheet.
The method described in this invention can be applied to a wide range of thicknesses of coatings ranging from 20 μm to 300 μm, because in no case are they so thick that they cannot be traversed by the low frequency technique proposed herein.
Thin thicknesses of carbon fiber, mainly 1 to 5 mm, allow obtaining very reliable results in the measurement of the thicknesses of the coating, because they have a greater relative importance in the separation of variables.
The aluminium sheet must have a suitable thickness, preferably more than 2 mm and must not be plated. 2024, 7075 sheets and the like, in different treatment conditions, are suitable for carrying out the calibration and therefore the measurements.
The results obtained with the present method are compared with micrographic cut measurements which are determining in situations of conflict.
The results obtained in a specific embodiment of the invention are set forth below, using a multichannel Zetec MIZ-40 A as an induced current equipment, a Leica Q 550 MW Image Analyzer as micrographic equipment, and an absolute Donut Nortec/R/100 Hz-1 kHz/0.50-1.00 inches, P/N 9215653/S/N FO4173, type probe with the following characteristics as a measuring probe:
Frequency: 950 Hz
Gain: 41 dB
Horizontal scale: 2.0 V/D
Vertical scale: 0.4 V/D
Firstly, the zero calibration is carried out using to that end a paint-free carbon fiber test piece, which is the coating measured in this specific case. As can be seen in
Then, as shown in
One of the test pieces used for the test can be observed in
The examined test piece of
Another important issue to be considered is the finishing surface of the carbon fiber to be examined. Composite materials with textured surfaces are very rough, and this can make the measurement of very thin paint thicknesses difficult, particularly if a considerable thickness of said fiber is considered. For small thicknesses, as in this example (1.6 mm), this fact can be minimized by applying pressure with the probe on the fiber and the aluminium support sheet, as well as thanks to the wide rounded configuration of the Donut type probe used.
Thus, the micrograph of
Another relevant issue in this method is the importance of the calibration zero, which must be carried out between each of the measurements with the aim of preventing as much as possible the fluctuations that may interfere therein. This entails calibrating the zero before each reading.
Table 1 below shows the results obtained in the test pieces tested by the induced current method of the invention versus the real data of the micrographic cut of these test pieces, as well as two Mylar type reference polyester sheets used in the calibration of the method, in the measurement margins.
Mylars: 195/193 18.9/17.5 in μm
In reference to
Thus, the method for determining the thickness of a coating on a composite material by using induced currents, developed by the present invention, has the main features that are detailed below:
Modifications comprised within the scope defined by the following claims can be introduced in the preferred embodiment which has just been described.
|Mar 9, 2007||AS||Assignment|
Owner name: AIRBUS ESPANA, S.L., SPAIN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:FUENTE SOUVIRON, ANTONIO;PASCUAL FERNANDEZ, JOAQUIN;REEL/FRAME:019022/0837;SIGNING DATES FROM 20070122 TO 20070201
|Apr 14, 2011||AS||Assignment|
Owner name: AIRBUS OPERATIONS S.L., SPAIN
Free format text: CHANGE OF NAME;ASSIGNOR:AIRBUS ESPANA, S.L.;REEL/FRAME:026124/0168
Effective date: 20090320
|Sep 19, 2011||FPAY||Fee payment|
Year of fee payment: 4
|Sep 15, 2015||FPAY||Fee payment|
Year of fee payment: 8