Thickness Measurement on Large Composite Parts 2

[mrletters]

Hey guys,

We have been requested to measure some large carbon fiber parts (around .150 to .250 in thick). But there are some areas we can reach with a micrometer nor caliper.

We have also tried to use a capacitive sensor and an ultrasonic device we use for void detection. The first one failed because we also have a copper mesh on the OML of the part so it interferes on the measurement. With the second we were not able to get a correlation of the signal with the thickness as it has been developed to measure porosity mainly.

Is there some method we can use to accomplish this? Is it a common practice to check thickness of large composite parts even though the thickness is quite irregular?

 

[KENAT]

Anyway you can set up some king of gauge post that you sit the area of interest on, and then measure to the far side?

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[SWComposites]

quick Google search found this:

http://ndtsystems.com/

is your ultrasonic device a pulse-echo or thru-transmission unit?

why does your customer want thickness measurements in the center of the part? to verify layup?

 

[MikeHalloran]

If limited accuracy is acceptable, you could make up a super deep throat caliper using a big C-frame and a long stroke dial indicator.

If you have a CMM and a lot of time, you could map both faces, one at a time, and let a computer map the thickness. Wouldn't it be great if the CMM itself could do that?



Mike Halloran
Pembroke Pines, FL, USA

 

[mrletters]

Hey guys, thanks for the suggestions. In fact we used a Laser Tracker and performed mostly the procedure MikeHalloran mentioned. We placed the part on the mold, then used a Laser Tracker to map the points on the IML, removed the part and then mapped the points on the OML. We obtained the distances and later on we verified them with a potable ultrasonic equipment and the points near the edge we used a deep throat micrometer. All seemed very alike and close to what we expected.

Cheers!

 

[MagicProbe]

Would this work for your application?

http://www.magicprobe.net

I developed this originally for the Musical Instrument makers to measure large plates of wood or assembled instruments where no caliper can reach. As long as you can get a ball on the other side of the material and it it non-ferrous, you can measure the thickness all over.
The device uses magnetics with a probe and target ball.