BMS numbers explanation (for composite repair materials)

[Red_Starr]

Hi All

New poster here

Was just wondering if anyone out there can help explain BMS numbers for composite repair materials. Don't have any actual issues with the numbering system eg. (BMS 5 is for film adhesives), but is the Grade, Type and Class that are leading me to a deadend.
What does each term refer to or mean, say for film adhesive or honeycomb?
What would the difference be between Class 1 and Class 2

eg. BMS 8-124, Type 5, Class 6, Grade 3 vs BMS 8-124, Type 1, Class 1, Grade 5.5. What exactly is the difference between these 2 honeycomb core numbers?
and how can we interpret these numbers so as to be able to determine material substitution eg. using Class 2 instead of Class 1 as the manual refers.

 

[SWComposites]

Why don’t you have a copy of the spec if you are using the materials for repairs?

For that BMS, Grade is the core density, Type (I think) is cell type, and will have to go look up Class.

 

[SWComposites]

And the definitions are different for each spec.

 

[WKTaylor]

RS... what are You working-on? Aluminum- aluminum or aluminum-aluminumHCC-aluminum, etc... bonded structure???

For the BMS 5 series... I vaguely recall its dedicated to adhesives and sealants.

Use the vendor [company] standard or generic... unless You are forced to use Boeing spec stuff, materials... thus...

For paste and film adhesives I usually specify Cytec, Henkel-Hysol, 3M or generic [AMS, MMM-A-134, A-A-XXXXXX, etc]

For aluminum honeycomb core why not specify AMS-C-7438? NOTE. I suspect that HC core coding system is universally accepted and probably mimicked in Boeing specs you cited(?)... and is just as good and cheaper.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[Red_Starr]

Just a bit more info.

Whilst this was prompted by a certain repair, it is more of a general enquiry as it is not just limited to the materials i posted in my original post.
The materials are not there, and we are just working on what is in the manual.

And just a reminder, for some of us based outside the EU and USA/ North America, obtaining materials is a huge challenge. Shipping can sometimes cost as much as the material, sometimes even more.
For the repair that we are working on (bonded panel, carbon fibre), Boeing is the OEM of that particular component, and obviously unless they do state that we can use any alternatives, we wont (besides the alternatives are NOT available).

Anyway, i am trying to just find out what Class, Type and Grade refer to for these materials.
Another example would be these film adhesives
BMS 5-137 Type 2, Class 2, Grade 5 vs
BMS 5-137 Type 2, Class 1, Grade 10.

The challenge we face is that a supplier (in the US or EU) can tell you that they have certain material, but only available as Class 1 or Class 2. So knowing what the difference is between the 2 would be extremely useful
















































































































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[KirbyWan]

For BMS5-137. Type I is primer and the class is different VOCs, Type II is film adhesive and the class is supported (1) or unsupported (2) for when you need to reticulate it for bonding a perforated face sheet. Grade applies to type II only and is the thickness of the film adhesive. If you need to know what products are qualified, you should get the BMS5-137 QPL (Qualified Products Listing) or go to a major supplier and ask what products they have that are qualified to this spec/type/class/grade... Remember, this is old information so take it with a grain of salt.

And,... Um... cut down on the white space in your post...

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[rb1957]

"surely" Boeing defines these specs ? and also "acceptable substitutes". Possibly resin manufactures "could" say this product is equivalent to BMS ... but probably won't put it in writing.

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

'Google' any Boeing part numbers You may have... and talk to vendors.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]