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Technical Discussions
pratchaya kittisakkul
pratchaya kittisakkul
20:03 Oct-15-2009
Aircraft Fiberglass Radome

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.

 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 897

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
897
20:35 Oct-15-2009
Re: Aircraft Fiberglass Radome
In Reply to pratchaya kittisakkul at 20:03 Oct-15-2009 (Opening).

Pratchaya,

I think you maybe going the wrong way. I did some delam and disbound check on F18 and we would normally a 2.25 MHz transducer in a pitch an catch method. So I recommend lowering your frequency.

 
 Reply 
 
pratchaya kittisakkul
pratchaya kittisakkul
20:50 Oct-15-2009
Re: Aircraft Fiberglass Radome
In Reply to Michel Couture at 20:35 Oct-15-2009 .

Thank you michel I'm very appreciate your reply and I will try as you recommend.

If anyone have any technics to do with fiberglass radome,please don't hestitation to let me know.I still looking forward to any answers.

 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
22:48 Oct-15-2009
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.

 
 Reply 
 
john harbert
john harbert
01:03 Oct-16-2009
Re: Aircraft Fiberglass Radome
In Reply to Tom Nelligan at 22:48 Oct-15-2009 .

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.

 
 Reply 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 307

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
307
08:38 Oct-16-2009
Re: Aircraft Fiberglass Radome
In Reply to john harbert at 01:03 Oct-16-2009 .

Hi Pratchaya,
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.

 
 Reply 
 
pratchaya kittisakkul
pratchaya kittisakkul
11:48 Oct-16-2009
Re: Aircraft Fiberglass Radome
In Reply to Godfrey Hands at 08:38 Oct-16-2009 .

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.

 
 Reply 
 
Simon Amallraja
Simon Amallraja
18:21 Oct-16-2009
Re: Aircraft Fiberglass Radome
In Reply to pratchaya kittisakkul at 20:03 Oct-15-2009 (Opening).

You can try Non Contact Ultrasound method. check with www.ultrangroup.com. you will get more details.

You can also try Rotary UT Phased Array method. check with www.sonatest.com for Rapidscan applications. you will find more details.

Simon

 
 Reply 
 
Jack A. R.
Jack A. R.
09:11 Oct-20-2009
Re: Aircraft Fiberglass Radome
In Reply to Simon Amallraja at 18:21 Oct-16-2009 .

Hi Guys,

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.

 
 Reply 
 
yoram shohat
yoram shohat
14:45 Aug-26-2010
Re: Aircraft Fiberglass Radome
In Reply to Jack A. R. at 09:11 Oct-20-2009 .

Please , I want to know the MIL-STD or ASTM for ULTRASONIC INSPECTION of composite laminates RADOME . The radome contain also Honrycomb.

Regards
yoram

 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 897

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
897
03:24 Aug-27-2010
Re: Aircraft Fiberglass Radome
In Reply to yoram shohat at 14:45 Aug-26-2010 .

Yoham,

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.

 
 Reply 
 
Paul Sacker
Paul Sacker
11:37 Nov-04-2010
Re: Aircraft Fiberglass Radome
In Reply to Michel Couture at 03:24 Aug-27-2010 .

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.

 
 Reply 
 
Simon Amallraja
Simon Amallraja
14:41 Nov-04-2010
Re: Aircraft Fiberglass Radome
In Reply to Michel Couture at 03:24 Aug-27-2010 .

You have use very low frequency probes fior this application. Look at Sonatest website for Dryscan 410D equipment - you will have many details for your application.

Also look at Rapidscan 2 and 3D System from the same manufacturer. You will get more info.

Look into www.ultrangroup.com. Their Non Contact UT Systems will guide you more on your application.

Look at www.vidisco.com. Their fox rayzor - flat panel system will guide you more on your application

Look at www.zetec.com. Thier MIZ 21SR will guide you more on your application.

There are many manufacturers in the World for the above methods. I have mentioned which I am familiar with.

Good Luck

Simon

 
 Reply 
 
Alex Easton
Alex Easton
18:03 Nov-04-2010
Re: Aircraft Fiberglass Radome
In Reply to pratchaya kittisakkul at 20:03 Oct-15-2009 (Opening).

Hello Pratchaya,

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.

Contact me if you would like details.

 
 Reply 
 
Mike Nash
Mike Nash
21:10 Nov-05-2010
Re: Aircraft Fiberglass Radome
In Reply to Alex Easton at 18:03 Nov-04-2010 .

It seems that you pretty much have the answer already. However, next week I will try to ask a colleague of mine that works in aircraft restoration and is also a very experienced NDT practitioner.

 
 Reply 
 
Michel Couture
NDT Inspector,
consultant, Canada, Joined Sep 2006, 897

Michel Couture

NDT Inspector,
consultant,
Canada,
Joined Sep 2006
897
03:11 Nov-06-2010
Re: Aircraft Fiberglass Radome
In Reply to Mike Nash at 21:10 Nov-05-2010 .

Some techs used to do that too when I was in the air force. The trick here is to have your quarter ($0.25) calibrated to be able to find the edge of the delamination.

 
 Reply 
 
joel nyaga
joel nyaga
14:59 May-17-2020
Re: Aircraft Fiberglass Radome
In Reply to Michel Couture at 03:11 Nov-06-2010 .

I have seen Airbus recommending the use of Through Transmission Ultrasonics. The challenge is the coupling of tranducers may be one is to use a Yoke aligner.
who knows where to get the airbus composite standards. what is their website i can check?

 
 Reply 
 
Johann Hinken
,
fitm Hinken Consult, Germany, Joined May 2014, 21

Johann Hinken

,
fitm Hinken Consult,
Germany,
Joined May 2014
21
12:25 May-18-2020
Re: Aircraft Fiberglass Radome
In Reply to joel nyaga at 14:59 May-17-2020 .

Meanwhile microwave NDT has become a well recongnised method. It is ideally suited to test thick GFRP walls, e.g. GFRP radoms. It can be uesd in reflection and through transmission. For an overview see
https://fitm.de/wp-content/uploads/2018/06/N38e_Microwave_Testing_An_Overview.pdf
For more details you may contact me directly.
Johann

 
 Reply 
 
J.B.
J.B.
15:27 May-18-2020
Re: Aircraft Fiberglass Radome
In Reply to joel nyaga at 14:59 May-17-2020 .

@ Joel
Wow,
you digged out a rather old communication!
Regarding Airbus NDT tools and reference blocks: Besides Airbus Customer Support the best source is TESTIA (https://www.testia.com/), they have an online shop for tools, probes, reference blocks etc. and items not listed there you my ask for by mail of phone. As far as I know the onlineshop and the tooling is handled by the subsidiary in Bremen, Germany. TESTIA has recently refurbished their Homepage - somehow they disimproved it. A link to the Online-Shop is missing now in the TESTA page, but with https://shop.testia.com/ you can still reach it.

The Airbus yoke is build by OptoPrecision (https://www.optoprecision.de/en/industrial-solutions/applications/non-destructive-testing-ndt.html) - you can see it in the following image: https://www.optoprecision.de/fileadmin/_processed_/d/a/csm_Handzange_6531e19387.jpg. The legs of the yoke can be ordered in different length. Together with Sonatest STP (Soft Tip Probe) - see https://sonatest.com/application/files/9015/7227/3570/STP_N.pdf it can be used with all standard UT equipment for inspection of Sandwhich or thin CFRP structure.

For reference blocks regarding CFRP and Sandwich:
checkout the following document:
https://prod-ng.sandia.gov/techlib-noauth/access-control.cgi/2003/032112.pdf
https://www.niar.wichita.edu/chicagoworkshop/Chicago%20Damage%20Tolerance%20Workshop%20-%20July%2019-21,%202006/Thursday%20-%20Session%205%20Presentations/GalellaWrkshp.pdf
Those sets are general - easy to reproduce - the reference blocks are recommended by the FAA and described by the SAE - there are specific SAE documents describing the standards you have to pay for:
ARP 5605, “Solid Composite Laminate NDI Reference Standards,” SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001.
ARP 5606, “Composite Honeycomb NDI Reference Standards,” SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001.
The papers I put the links in contain more or less all information, so you need not to purchase the SAE docs.
There should be several companies especially in the US selling these block sets.

Airbus has developed an advanced procedure to inspect honeycomb with standard transducer, pulse echo and standard equipment like USM 35 etc. It works basically with monolithic piezo transducer (not composite piezo) K1SM (or even with a corresponding 0,5Mhz - K0.5SM). In Quality Magazine this was once described very short - see here https://www.qualitymag.com/articles/94999-nondestructive-bond-testing-for-aircraft-composites, you have to focus on the part above the image https://www.qualitymag.com/ext/resources/Default_Images/Principe_Composite_2B.png

A little more can be found within the presentation: https://www.researchgate.net/publication/320112533_NDT_Toolbox_for_Honeycomb_Sandwich_Structures_-_a_comprehensive_approach_for_maintenance_inspections
refer to page 14 and following. But for details you have to read the Airbus NTM procedure referenced there. In the meantime the method was improved to be used with array transducers and RotoArrays (0.5MHz) which speeds up the inspection far beyond everything else. The procedure is available in Airbus Manuals, but nothing is published free to access - you may ask people dealing with Airbus Aircraft Maintenance if they could help you to get access to the NTM.

Hillger also published this method in a report about Helicopter Tail Boom Inspection: https://www.ndt.net/article/ecndt2010/reports/4_01_17.pdf see chapter 2 "Ultrasonic echo-technique" He gives an idea how to preset the filters to deal with the characteristics of the sound transmission in honeycomb cells, as they only transmit in the range of 0.1MHz and 1MHz if you want to use P/E inspection. Benefit of this technique: You can penetrate thick (stiff) CFRP skin as well as thich (lengthy) Honeycomb cores, which is impossible e.g. with devices like Bondmaster or Tap Test.

 
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