Method for measuring thickness of carbon fiber components using ultrasounds

Abstract

The present disclosure refers to a method for measuring thickness in any type of carbon fiber component, even in components having parts with different thickness and integrating at least a second material. The method includes measuring with the maximum and minimum real thickness of the component, and measuring with ultrasonic equipment the time that the ultrasound takes to propagate across the component part with maximum and with minimum thickness, calculating a thickness correction value, and calculating an ultrasound test speed from said thickness correction value, said measured times, and said measured maximum and minimum real thickness. Then, the total thickness of each of the parts of the component are measured, using ultrasounds with the same calculated ultrasound test speed, and the thickness correction value is applied to each of the measuring total thickness of each part, to determine a corrected carbon fiber thickness for each part.

Claims

1. A method for measuring carbon fiber thickness, in a carbon fiber component having parts with different thickness and integrating at least a second material, the method comprising the steps of: measuring with a mechanical thickness measurement device a maximum real thickness and a minimum real thickness of the carbon fiber component; measuring with an automatic ultrasonic equipment, a time that an ultrasound takes to propagate across the carbon fiber component part with the maximum real thickness and the carbon fiber component part with the minimum real thickness; calculating an optimum ultrasonic test speed and a thickness correction value for the carbon fiber component; wherein the thickness correction value and the optimum ultrasound test speed are determined using the time that the ultrasound takes to propagate across the carbon fiber component part with the maximum real thickness and the carbon fiber component part with minimum real thickness, and the maximum measured real thickness and the minimum measured real thickness; measuring a total thickness of each of the parts of the carbon fiber component, using ultrasounds with the same calculated ultrasound test speed, and applying the thickness correction value to each of the measuring total thickness of each part, to determine a corrected carbon fiber thickness for each part.

2. The method according to claim 1, wherein the maximum real thickness and the minimum real thickness of the carbon fiber component is measured with a micrometer.

3. The method according to claim 1, wherein the thickness of the second material is constant though out the different parts of the component.

4. The method according to claim 1, wherein the carbon fiber is a Carbon Fiber Reinforced Plastic.

5. The method according to claim 1, wherein during the step of measuring a total thickness of each of the parts of the carbon fiber component the ultrasound is generated by an automatic ultrasound measurement equipment, set at the previously calculated ultrasound test speed.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Preferred embodiments of the present disclosure, are henceforth described with reference to the accompanying drawings, wherein:

(2) FIG. 1 is an illustration of a schematic representation of the prior art traditional process for thickness measurement using ultrasounds.

(3) FIG. 2 is an illustration of a schematic representation of an ultrasound thickness measurement in a carbon fiber component (3) formed by parts with different thickness (3A,3B,3C) and incorporating a second material (4), as a copper mesh, adhesive etc. in accordance with an aspect of the present disclosure. The arrows in the figure represent the different ultrasound propagation speed for each material, and the error X caused in the carbon fiber thickness measurement due to the different ultrasonic speed in the second material.

(4) FIG. 3 is a graphic representation of the problem associated with the use of different speeds and lack of precision offered, compared with the solution that allow the use of a single speed and greater accuracy for a thickness range of 2-18 mm in accordance with an aspect of the present disclosure.

(5) FIG. 4 is a table containing an example of calculated and measured data to demonstrate the accuracy of the carbon fiber measurement method in accordance with an aspect of the present disclosure.

DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE

(6) The method of the present disclosure is suitable for measuring carbon fiber thickness, in any carbon fiber component (preferably, Carbon Fiber Reinforced Plastic), as shown in FIG. 2, having parts with different thickness (3A,3B,3C) and integrating at least one layer (4) of a second material, different than carbon fiber. Typically, in a wing skin cover of an aircraft, this second material is a copper mesh having a constant thickness though out the different parts of the component.

(7) The real thickness of the thicker part (3A) and the real thickness of the thinner part (3C), are measured, with micrometer.

(8) An optimum ultrasound test speed is calculated for which the difference between the measurement error at the maximum real thickness and the measurement error at the minimum real thickness of the component, is similar

(9) FIG. 3 shows the accuracy of several ultrasound speeds for a range of thickness 2-18 mm. It can be noted in the graph that an ultrasound speed of 2955 m/s is the optimum speed, since it is the one providing a similar error along the thickness of the component.

(10) On the other hand, two time measurements are taken, one is the time that the ultrasound takes to propagate across the thicker component part, and a second one for the time that the ultrasound takes to propagate across the thinner component part.

(11) Then, a thickness correction value (X) is calculated for each part (3A,3B,3C) of the component with different thickness. Additionally, an ultrasound test speed (Y) is also calculated from said thickness correction value, said measured times, and said measured maximum and minimum real thickness.

(12) The process for calculating these two parameters (X),(Y) is describe below, wherein:

(13) Y=unique ultrasound test speed

(14) X=thickness correction value

(15) E.sub.1=measure by micrometer the real thickness of the thicker part of the component

(16) E.sub.2=measure by micrometer the real thickness of the thinner part of the component

(17) T.sub.1=time that the ultrasound takes to propagate across the thicker part of the component.

(18) T.sub.2=time that the ultrasound takes to propagate across the thinner part of the component.

(19) Knowing that E=V.Math.T, then:
E.sub.1+X=Y T.sub.1
E.sub.2+X=Y T.sub.2
X=Y T.sub.1E.sub.1
X=Y T.sub.2E.sub.2
Y T.sub.1E.sub.1=Y t2E.sub.2
Y T.sub.1Y T.sub.2=E.sub.1E.sub.2
Y(T.sub.1T.sub.2)=E.sub.1E.sub.2

(20) We obtain the value of the two parameters:
Y=(E.sub.1E.sub.2)/(T.sub.1T.sub.2)
X=(Y T.sub.1)E.sub.1

(21) That is, we obtain a common calculated ultrasound test speed (Y) and a thickness correction value (X) for all the parts of the component with different thickness and materials configuration.

(22) In the case of FIG. 2, since the copper mesh thickness is constant throughout all the parts of the component, the value of (X) is the same for all the parts.

(23) Finally, the automatic ultrasound measurement equipment is set with the calculated ultrasound test speed (Y), and using this speed he total thickness of each of the parts of the component is measured. Then, the calculated thickness correction value (X) is applied to each of the measured total thickness of each part, to obtain a corrected carbon fiber thickness for each part of the component.

(24) FIG. 4 is a table regarding the great accuracy achieved with the method of the present disclosure, wherein it can be noted that different between the real thickness (caliper value column), and the thickness obtained by the method of the present disclosure (calculated thickness column), is less 0.52% in this particular example.