Substitute for EPON 828?
Substitute for EPON 828?
(OP)
Howdy all,
I am trying to find a material substitution for EPON 828. This is to repair a DC-10 antenna panel which is a laminate honeycomb core panel made from 250°F cure prepreg fiberglass. The DC-10 SRM 51-43-01 provides a wet layup repair using EPON 828 or Hetcon 92. I want to use the same process only with EA9390 adhesive and cure cycle similar to B757 SRM 51-70-17.
The problem I am having is finding data on these old adhesives. The Epon 828 data sheet is very short on strength properties. It can be cured with dozens of different curing agents and it lists the strenght of up to 10000 psi without mentioning which curing agent was used. I can't find any information on Hetcon 92.
Does anyone have recomendations for how to substitute materials? I can't really do a test since I don't have Epon 828 data to compare against. There is plenty of data on EA9390 from Henkel and in BMS 8-301, but what do I compare it to.
Thanks to the community for pointing me in the right direction.
-Kirby
I am trying to find a material substitution for EPON 828. This is to repair a DC-10 antenna panel which is a laminate honeycomb core panel made from 250°F cure prepreg fiberglass. The DC-10 SRM 51-43-01 provides a wet layup repair using EPON 828 or Hetcon 92. I want to use the same process only with EA9390 adhesive and cure cycle similar to B757 SRM 51-70-17.
The problem I am having is finding data on these old adhesives. The Epon 828 data sheet is very short on strength properties. It can be cured with dozens of different curing agents and it lists the strenght of up to 10000 psi without mentioning which curing agent was used. I can't find any information on Hetcon 92.
Does anyone have recomendations for how to substitute materials? I can't really do a test since I don't have Epon 828 data to compare against. There is plenty of data on EA9390 from Henkel and in BMS 8-301, but what do I compare it to.
Thanks to the community for pointing me in the right direction.
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.





RE: Substitute for EPON 828?
what's the critical criteria ? strength or stiffness ?
is the old panel completely U/S, or could it be used as a test coupon ?
can you set up somethinglike a 3- or 4- point bend test and compare old and new ??
can you do calcs on the new ... put in some antenna load, a bit of P/A, ... ??
RE: Substitute for EPON 828?
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
if you're "just" blanking the old antenna install, what about a Al blanking plate ? similar to the antenna footprint, 0.05" thick ...
RE: Substitute for EPON 828?
Do you have a reference for the Al blanking plate? Note this antenna panel is a panel roughly 4' by 4'
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
is the panel loaded, particularly by cabin pressure ? (i suspect not, but have learnt to ask)
is the 4' x 4' the size of the panel or the size that needs to be repaired ?
how well do you get on with your local cert people and the customer ? this affects how much substantiation you need to do
on one level, if it is "just" a fairing panel, and the material susbtitution sounds reasonable to you (and to the others involved) then maybe a bit of "hand waving" is enough; i'd've thought the detail design of how you finish the reapir (and join to the existing panel) is porbably more important than the details of the materials used.
on another level, if the panel sees significant load then you need a good story as to why this repair is good-to-go. one "simple" possibility is to do a stiffness test on the finished part.
Al balnking plate is standard industry practice for covering a removed antenna. if the hole is 4' x 4' then you'll need more than just a plate, stiffeners as well. if the plate is loaded, more analysis ...
RE: Substitute for EPON 828?
this panel is a fairing panel, so one face of it is an airflow surface, but it is outside the pressure vessel. There are no significant pressure loads. Think of it like any external fairing panel. The antenna part did kind of throw me, because it doesn't looke like an antenna. It looks more like an access panel to an antenna. But Antenna, Assy-ADF Sense AFT is how it is reference in the part drawing. This antenna P/N is AAN 7017
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
cutting off the edge band and gluing on a new one doesn't sound like a good idea.
filling holes, then drilling a new pattern also doesn't sound like a good idea.
remaking the panel with a new composite, and confirming the stiffness against an existing panel works.
making an Al s/m replacement panel works (though more work than it's work than it's worth ??
maybe cuting of the composite edge band and fabricate an Al replacement, riveted onto the composite panel ??
RE: Substitute for EPON 828?
It's a pretty standard repair. Just step back the plies 1/2" each so that the plies are to the part edge except right where a fastener is. Then lay up plies in each step. Add an extra ply and a sanding ply vacuum bag and cure and it's good as new. Proving it is the tough part.
And BTW, there are SRM repairs for just filling the holes with RT cure adhesive and chopped fiber, but the number of holes you can repair is limited.
Also I don't know what the antenna is. I just have a panel. I don't know if the panel _is_ the antenna or if the antenna bolts to the panel. There is one odd circular fitting on the interior of the panel, but it doesn't go through the panel. I am at a loss too about what the antenna is.
-Kirby
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
would it be unreasonable to manufacture a test specimen ? maybe compare before and after ? (afte being the panel with a bunch of holes repaired in a presumably conservative manner ... adjacent holes off-set towards each other a conservative amount ??)
RE: Substitute for EPON 828?
I eventually found some property data that shows the EA9390 has strength (at least with one test method) as strong or stronger then the original fiberglass prepreg. I was just hoping to have more information, particularly on EPON 828
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
RE: Substitute for EPON 828?
For each individual repair design, this EASA approval is based on:
...
3) minor repair data determined to be acceptable data (under 14CFR part 43) as determined by a U.S. maintenance organisation under FAA's authorized system.
I think I'm reading that if it's acceptable under FAA system it's good enough for EASA. And the FAA system is DER approval is only needed on major repairs. I would not consider this a major repair. QED.
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
RE: Substitute for EPON 828?
Here's a page from the DC-10 SRM. It shows the Epon 828 with two possible hardeners. Epolite 2323 and Hardener 956. This is as qualified a formulation as the SRM gives and it still dosen't bring me closer to the quality of information I would like to have to substantiate this repair.
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
RE: Substitute for EPON 828?
I guess the products are still available, but we have a few resin systems that we use regularly that we prefer to use. Perhaps I should just tell purchasing to bite the bullet and buy the SRM qualified materials. But we work with EA9390 alot and like the system. It's strong, durable and we are familiar with it. What I'm really lacking is good data on Epon 828 with a specific curing agent.
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
Contact Miller Stephenson chemical co in Danbury Ct
http://www.miller-stephenson.com/
They sell Epon resins and used to have data sheets showing the heat deflection curves and tensile strengths for different hardeners.
B.E.
RE: Substitute for EPON 828?
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
RE: Substitute for EPON 828?
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
Kirby
I realise this may be taking you off to where you do not want to go.
Miller does sell TETA. this hardener at 11 to 13 parts per hundred will give you a room temperature cure that can be post tempered up to 180 degrees F and give you the strengths you are looking for.
Back in the 70's I used to practically bathe in this stuff.
In the 80's I got an MSDS sheet with an order of TETA and nearly had a heart attack when I saw what it could do to you.
Even this stuff is a pretty aggressive hardener, however,
this was an approved room temp resin system for several aircraft Mfrs in the 70's Unfortunately I have discarded most of those old data sheets. The only old Boeing document I have is D6-24483 for the 767 ( 1985)
Which lists Epocast 956 and 9449 hardeners
Which I do not think will help you. I think you are dealing with an old DPS spec which Boeing has now taken over.
You may have to break down and ask Boeing for help on this one.
B.E.
RE: Substitute for EPON 828?
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
RE: Substitute for EPON 828?
I gave you a star , that document is 4 years younger than mine.
B.E.
RE: Substitute for EPON 828?
That'll help if someone second guesses my repair. And i can go through that and get a real idea of how strong it really is based on a whole slew of data. Excellent, a Star for you.
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
However, It isn't very helpful. It doesn't show strengths for different hardeners.
My copy is from 2003. 3 Pages.
Exerpt:
4. TECHNICAL REQUIREMENTS:
4.1 Mechanical and Physical Properties: The properties of a laminate, tested at 70-85F, shall be as specified in MIL-R-9300, Type 1, in addition to the following elevated temperature requirements when tested lengthwise at
300F ±10 after aging for 1/2 hr at this temperature:
Flexural, Flatwise, psi, min
Ultimate Strength, 40,000 psi
Initial Modulus of Elasticity 2 X 106
Ultimate Compressive Strength, Edgewise, psi, min 20,000
Ultimate Tensile Strength, psi, min 30,000
4.1.1 Barcol Hardness:: The Barcol hardness of the laminate fabricated as specified in MIL-R-9300 shall be a minimum of 60. Size of specimen shall be in accordance with Fed. Test L-P-406.
RE: Substitute for EPON 828?
Yeah I found that spec and read through it, but it didn't have any useful property data that I could compare. I didn't have any flexural flatwise data on EA9390. For that I had flatwise tension, but no info on the Epon 828 for flatwise tension. It's like they purposely avoided providing any datum point that matched up between the two adhesives.
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.
RE: Substitute for EPON 828?
I should read the intent of problems first. I gave you all I had on Epon 828, but, why not repair per DC-10 SRM V-II 51-62-01, GENERAL REPAIR OF ADVANCED COMPOSITES.
Using Table 1, Sh 2 (EA9396 - DPM 5535-5).
Cure 1 Hr at 150F.
EA9396 Attached.
RE: Substitute for EPON 828?
-Kirby
Kirby Wilkerson
Remember, first define the problem, then solve it.