I want to know about the best way to inspect delamination of a 10 mm thickness,Aircraft Radome made of fiberglass.At first I did 10 MHz and 15 MHz UT but It had many noises and so hard to see BWE.
Please let me know if you have any methods or UT technics that useful to inspect this fiberglass radome.
22:48 Oct-15-2009 Tom Nelligan Engineering, retired, USA, Joined Nov 1998 390
Re: Aircraft Fiberglass Radome In Reply to pratchaya kittisakkul at 20:50 Oct-15-2009 .
I agree with M. Couture. We would normally recommend a 2.25 MHz test frequency as a starting point when testing 10 mm of fiberglass. Also, if your flaw detector has adjustable filtering, you should experiment with low pass filter settings to help clean up some of the scatter noise.
typically i would think that you would want to use a thru-transmission method to find lamination/de-lamination in a composite part.
You should be using a procedure that gives step by step instructions for aircraft parts including the type of inspection to be used, and type of inspection equip to be used including transducers, couplant ...etc.
I agree with John Harbert on this that Through transmission is best. I would also recommend trying to do it with C-Scan rather than just a probe each side, as this is too subjective.
2.5MHz seems a good frequency to start with, but if you are using C-Scan, don't be afraid to go down to 1MHz as well.
I assume the Radome has quite a curvature on it, so that will make it difficult to inspect, but we use automated and programmable machines here, working in through transmission C-Scan, so it really is a job for someone with specialist equipment.
Thank you for every opinions.I will try to do technics that you all replies.Anyway,I would like to listen anyother way or your experience with this subject.
One thing I would like to know is about inspecting this subject with Advance NDT like Laser shearography or Thermal/Infrared or other methods to do with Aircraft fiberglass.
Thanks for allowing me to make some suggestion here in this forum. This is a friendly advice, I would better suggest if you'll try radiography method (x-ray), I believe in every aircraft there's a MRP/MRO (Maintenance Repair Procedure/Operation). If these aircraft made by Boeing or Airbus they have their own procedure for NDT inspection of radome, so you don't need to worry just follow their procedure. Since the material is made of possibly (kevlar) fiberglass you can ask the owner of the aircraft for this requirements or manual. In aircraft industry always follow the manufacturer approved procedure (NDI) that's the golden rule, but if you're experimenting in your own and try and try until you succeed it's a long process. Hope this will give you other solution to your problem.
Instead of looking for a MIL-STD or an ASTM procedure, I recommend contacting the aircraft manufacturer. When dealing with NDT of aircraft, the manufacturer will normally publish an NDT manual containing all of the approuved procedures. I don't know about the laws of your country, but to inspect an aircraft by any other method and unapporuved procedures would get you in hot water with the FAA if you were in North America.
On my days on aircraft, one instrument we used for such work was the Bondtester. Very simple to use and fairly accurate.
This can also be done as mentioned above using Thermal Imaging techniques - Both Boeing and Airbus have procedures for using Thermal Imaging to inspect composite structures. The technique is a variation of Flash or Lock-in Thermography. Have a look at the Thermal Wave website (www.http://thermalwave.com), or the AT Automation website (http://www.automationtechnology.de/cms/en/thermography.html) for a review of the principles.
Re: Aircraft Fiberglass Radome In Reply to pratchaya kittisakkul at 20:03 Oct-15-2009 (Opening).
The best way to inspect a radome for delamination is a simple tap test. Layout a grid on the external and internal surface and manually tap it out. You could set up an elaborate UT system with procedures, techniques and calibration standards if that suits you, but the tap test is the fasted, easiest and cheapest way to do it.
We have used bond testing systems and found that the tap test outperforms in all areas of the inspection; fast, easy, cheap, reliable and repeatable.
Don't forget to inspect for moisture. If it has impact delamination there is a very good chance for moisture ingress. Moisture has to be removed for transmission testing and structural soundness due to freeze and thaw in the flight cycle.
Most SRM's have this info. Request the information from the customer.