How to Measure thickness of Carbon Fibre Panels

lee01 · Jul 7, 2004

Okay this is more a measurement/ inspection enquiry.

I have a requirement to measure the thickness of some carbon fibre panels that are up to an inch thick. They are of various types of carbon (BMI/ Epoxy, Hand Lay RTM Fibre placed etc). And also have sacrificial ply’s.

I have to measure the thickness of these panels but they are approx 2 – 3 metres in size so measuring the middle areas is impossible!

I have callipers but not only are they too small to reach the middle areas, they are not that accurate!

I have looked into the Ultrasonic Thickness devices such as sonatest, GE Inspection technologies/ Panametrics but they cannot get through the thickness of these panels, I have also looked into Flaw Detection devices from the same companies.

They do go through the panels but when conducting a gauge R&R the results are not good. The KrautKramer device equates to 101% of our target tolerance of 0.178mm (0.007”).

I’m therefore sending out feelers to understand what other people/ organisations/ industries are using to measure thicknesses of carbon items where the skins are too large for micrometers/ callipers etc, and where the target tolerance is of a similar value.

Any help, direction or advice will be VERY thankfully received

Regards

Lee01

Wes Bucey · Jul 7, 2004

lee01 said:
Okay this is more a measurement/ inspection enquiry.

I have a requirement to measure the thickness of some carbon fibre panels that are up to an inch thick. They are of various types of carbon (BMI/ Epoxy, Hand Lay RTM Fibre placed etc). And also have sacrificial ply’s.

I have to measure the thickness of these panels but they are approx 2 – 3 metres in size so measuring the middle areas is impossible!

I have callipers but not only are they too small to reach the middle areas, they are not that accurate!

I have looked into the Ultrasonic Thickness devices such as sonatest, GE Inspection technologies/ Panametrics but they cannot get through the thickness of these panels, I have also looked into Flaw Detection devices from the same companies.

They do go through the panels but when conducting a gauge R&R the results are not good. The KrautKramer device equates to 101% of our target tolerance of 0.178mm (0.007”).

I’m therefore sending out feelers to understand what other people/ organisations/ industries are using to measure thicknesses of carbon items where the skins are too large for micrometers/ callipers etc, and where the target tolerance is of a similar value.

Any help, direction or advice will be VERY thankfully received

Regards

Lee01

When I was in the machining business we used a large flat plate (checked for flatness with optical flats) and rigged a dial indicator on a swing arm.

We zeroed out the dial indicator at one point on the plate, then touched various points over the surface to indicate a continuous zero reading.

then we introduced the workpiece to the system and measured it for "z" dimension,

I have no idea of the flatness of your carbon fibre panel workpieces (is it important?), nor of the surface finish which might affect the reading.

Depending on how many workpieces you have to measure, this is a much cheaper solution to measuring a relatively big tolerance than investing in a large table coordinate measuring machine. Many machine shops are capable of producing a flat plate and supports to eliminate sagging at a reasonable price. Built-in bubble levels around the perimeter will help in maintaining level surface.

Govind · Jul 7, 2004

Lee01,
There is an instrument available in the market called "pistol Caliper"

http://www.mehtaassociatesindia.com/adver/103557c1.html

( I have no affiliation to this organization, just did a google search with pistol caliper as key word. This webpage has a picture)

Using this equipment you can reach long distances and measure thickness without cutting the cross section of the part.Check if Mitutoyo or Starrett has this instrument. I just verified Mitutoyo old catalogue. Iam not not able to find.
Is this the one you were looking for?

Note: Check if the measuring force is acceptable before using this instrument.

Govind.

Wes Bucey · Jul 7, 2004

Govind said:
Lee01,
There is an instrument available in the market called "pistol Caliper"

http://www.mehtaassociatesindia.com/adver/103557c1.html

( I have no affiliation to this organization, just did a google search with pistol caliper as key word. This webpage has a picture)

Using this equipment you can reach long distances and measure thickness without cutting the cross section of the part.Check if Mitutoyo or Starrett has this instrument. I just verified Mitutoyo old catalogue. Iam not not able to find.
Is this the one you were looking for?

Note: Check if the measuring force is acceptable before using this instrument.

Govind.

I think the problem lee01 is facing is that the reach he needs is closer to 1000 millimeters than 150 millimeters (the longest on the web page cited) to reach to the center of a 2 meter X 3 meter sheet (2000 millimeters X 3000 millimeters)

Al Rosen · Jul 7, 2004

Lee:

If you can spend about $1.5-$2k, you might look into an ultrasonic thickness gage.

http://www.drybanski.com/topac/sonogauge.html

More information can be found here. Maybe more than you need to know, but what the heck.

http://www.ndt.net/article/wt1097/hammond/hammond.htm

lee01 · Jul 8, 2004

Thanks for the assistance so far, unfortunately, the skins are of a complex shape and surface the use of a DTI is not an option (Although I have just thought of an offshoot from that idea).

I have looked into Callipers but they are not accurate, especially as they increase in size, they seem to bend and wobble?

I have looked into Ultrasonic Thickness gauges before and although not from this company, believe that they are not powerful enough to penetrate through the size, quantity, and type of Carbon Fibre ply’s.

Again thanks for your assistance, it’s a great site the coves, one of the best I’ve used!

Further advice is always thankful.

Carl Keller · Jul 8, 2004

I would look into a magnetic tester

Not sure of the Manufacturer, but they use a piece of steel on one side, and calculate the thickness by measuring the "Gauss" on the magnet applied to the other side.

I will search around and see if I can get some detail for you.

Carl-

lee01 · Jul 9, 2004

Carl,

Good I think I have heard of this before but could not find any information.

I think it was called a magnamic? If you do find any information please post it here so I can take it further

Many thanks

Much appreciated

How to Measure thickness of Carbon Fibre Panels

lee01

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