Composite Structures Question

[slowto280]

For starters - Happy 2024!

In the US FAA AMT (aircraft maintenance technician) general handbook (8083) - speaking about ultrasonic inspection, different types of laminate defects are discussed. Can anyone here fill me in what defect (closure member and core-to-closure member) is being mentioned here? Any information is greatly appreciated - in this case - Google is not my friend - coming up empty handed. Thanks very much!!!

Type IV—voids in foam adhesive or disbonds between the adhesive and a closure member at core-to-closure member joints

[wrench1]

Can anyone here fill me in what defect (closure member and core-to-closure member) is being mentioned here?

In general terms, the closure member is the material that seals up the edges of the laminate/composite panel, skin, etc. The core is the material that is laminated between the skins, etc. There are various types of closure members and core materials. The defect being addressed is the lack of adhesive or the unbonding of the adhesive (voids) between the closures themselves or the core and closures.


To get a better idea look to FAA AC 43.13-1B, Chapter 5, Section 7 (link below) which describes the ultrasound process in detail and provides examples of the different types of closures and their uses. Plus it shows how to inspect them as well.

AC 43.13-1B (https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_43.13-1B_w-chg1.pdf)

[slowto280]

Wrench, thanks much!! Did you edit your reply or am I going crazy?

Great explanation - closure is what I was looking for! I didn't even think to look in the 43.13, but they didn't really explain it - just discussed it.

Long story - instruct at an AMT school, and recently curriculum has changed and 'inspections' are now taught in block 1 - together with Math, Physics, Weight and Balance (go figure....?)

Anyway, your input is greatly appreciated - I can 'rest easy' tonight......

[TURIN]

Could you also tell your students that trying to 'map' composite damage using a ramp ultrasound detector on a wet night in February, on a remote line station with no hangar, is neither fun or easy. 😁
Happy 2024.👍😀

[tonytales]

Turin,
You are so right. Have spent many a night out there.
At a Boeing conference on the still in design B757, the subject of small damage repair to composites came up. Boeing had indeed produced a procedure to handle that. Only air temp had to be above 75-deg F.
I raised hand and asked what I do at Bradley, Connecticut, temp 23-deg F, freezing rain coming down, small ding in a trialing edge of a flap (baggage cart strike), No real structural problem, so could I speed tape it?
Horror and consternation. NO! Moisture intrusions, etc. Put it in hangar and repair properly.
"Then we have to wait for spring. No hangar there." (P&W do have one, but it is not available).
Lots of our procedures were written under a palm tree or in nice, warm offices. And yes, I have been at Bradley in freezing rain conditions.

[Webby737]

Could you also tell your students that trying to 'map' composite damage using a ramp ultrasound detector on a wet night in February, on a remote line station with no hangar, is neither fun or easy. 😁
Happy 2024.👍😀
I'd agree, especially if you're using the Olympus RDC which is little more than a modified direct reading thickness gauge. This gets even harder in the areas of multiple thicknesses such as door surrounds etc.
Whist you can use a standard A Scan ultrasonic test set for this, it will give you much more information but you still have to map out the individual thicknesses and that takes quite a bit of time.
The easiest option is to use phased array ultrasound that will give you a 2D image of what you're inspecting and only takes a couple of minutes to cover a relatively large area, the only downside to this is cost as the instrument and probe cost around 40K.