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Posted for "Dan Newland" <Dan.Newland@orcon.com>:
I said awhile back I was going to get some data for the LML aout surface
temperatures of aircraft outdoors, so here it is on Acrobat. After the
posting asking about temps, I called up my good friend and old boss Andy
Marshall to see if he still had the table of data. He said "Sure, do you have
my book?"...Duh... Yeah, he's given me all six editions since it came out.
This was scanned from it, "Composite Basics". It is an excellent book, very
readable and filled with "How to's" and "Where to go for's". Plus a few "And
the whole thing got screwed up when they fogot to..." It is even used as a
college text in some university engineering programs. You can get it from
Aircraft Spruce and the EAA bookstore I think. Andy used to ship and sell
them from his house to but I'll have to ask if he still does that or whether
it's strictly through stores now .
I also said I was going to do some research on the replacement adhesive for
the old Hysol 9339. A guy I work with on our spacecraft projects is the
former QC director of Dexter Hysol and worked with this (and other adhesives)
for years. I asked him about the Hysol and he in turn got in touch with some
of his old buds that are still there. The new stuff is Hysol 9360. It
appears to be better in elevated temperature performance by about 20 degrees
than the old 9339. It is available in qts. and also in ready mix tubes. I am
now checking the archives of Hysol (Loctite) to see exactly how comparable
they are and will get back with real data I will get back with the real data
because until I see numbers, I won't really know and I would expect some other
differences. I am particularly interested in various cure times so people in
Arizona in the Summer or Minnesota in the Fall can get the correct forulation
for their needs. Many base resins can have a whole family of hardeners that
when cured, have similar performance but have different working times. And
don't go to the general directory at Hysol to ask for the equivilent
adhesives, the people on the computer or phone line had their brains die but
their body hasn't found out yet.
The Hysol we use is terribly expensive but oddly, in many Aerospace cases is
identical to some of their industrial adhesives. In fact, many aerospace and
industrial adhesives are taken from the same batch but the aircraft adhesives
cost 5X or more of the industrial version. While it is easy to say this is
another example of a consumer rip-off like the $500 toilet seat, I can assure
you that in aerospace, the documentation is typically more expensive by far
than the parts. And no, there isn't an industrial grade of the 9360, I
checked because I didn't want to pay their usual "Aerospace rip-off prices."
Ooops!
One thing I want to re-emphasize is that while there is nothing wrong with
Jeffco, it is NOT the same as Hysol. All of the claims that Jeffco with flox,
or WEST System and flox, etc are "just as good as Hysol" MAY be correct, but
PROBABLY are not. More likely, they may be ADEQUATE and you won't die
testing an un-proved theory. Even if the adhesion were similar, adding
thixotrope with outsophisticated equipment would mean every batch would be
different in wet-out and flow. Jeffco is a general purpose room temp. cure
epoxy, it is not designed as a bonding adhesive! It sticks well but a bonding
adhesive would probably adhere much better. An analogy is if you said you
made your airplane out of metal, it wouldn't tell and engineer or metallurgist
much. Well, neither does saying "epoxy" since the physical properties from
one to the next may be orders of magnitude different. And price does not
necissarily guarantee performance since an adhesive designed to give elevated
temperature performance might be too brittle for normal applications. Or an
adhesive designed for high bond strength give poor wet-out in a laminate. It
is not necissarily bad, just designed to perform best in a certain area that
if you are not aware, could be differnt than you intended. A good example of
two extremes of bonding performance are an experiment I did using G-10 solid
glass/epoxy laminate. I prepped some samples for bonding with WEST system
epoxy and another with Applied Poleramic thixotropic bonding adhesive. The
WEST (pretty similar to JEFFCO), broke off pretty easily from the bond line
(adhesive failure) using a simple wedge test for peel adhesion. The Applied
Poleramic epoxy adhesive CAUSED THE LAMINATES TO SPLIT BEFORE THE BOND DID!
So do not EVER believe that the term "epoxy" means the same thing for all
applications. I use a lot of WEST System laminating epoxy, a lot of
toughened laminating epoxy, a lot of toughened adhesives and a lot of
toughened adhesives with high Tg temperatures. Not one of them are "bad", but
some may not be as good as others for what I need.
If you are working on a really CRITICAL part and you need to be assured of
maximum adhesion, you should be using better grades of adhesive. By better I
mean higher peel strength, higher impact strength, higher tensile or
compressive strength, higher tensile and compressive modulus, and VERY
IMPORTANTLY perhaps, higher Heat Distortion Temperature (HDT) which is related
but not identical to glass transition temperature (Tg). But you need to
figure out which properties you need to have improved. The history of
Lancairs is such that the materials called out are generally pretty good since
we seem to have few structural failures, but that doesn't mean for a few extra
bucks we couldn't improve our safety factor and fatigue resistance. Or
possibly in case of an accident, stop the damage in a smaller area. Many
manufacturers of general purpose adhesives also make more advanced
formulations. In fact, Jeffco makes its own brand of toughened adhesive
systems and WEST also has higher performance epoxies, (their ProSet epoxy
line). There are some really good epoxies out there, but for those that have
read my postings before, you know that I like Applied Poleramic. Partly it's
because they sell smaller quantities. But also, Rich Molton is the owner of
Applied Poleramic and former head chemist at Hexcell where he designed many of
their high performance epoxies. I like the ability to reach the person that
really KNOWS what he's doing, not a salesperson that can only quote out of the
literature. Rich and Doyle (the alter ego) watch their product being made
daily so I know the President is aware of everything going on in the plant.
It isn't big but it is very good. The phone number is (707 ) 747-6738. Next
door to them is YLA Inc. that manufacture high performance pre-pregs so it's a
little cottage industry there in Benecia, Ca. And there are certainly other
good manufacturers out there if you want to do some research.
For that matter, carbon fiber is similar to the generic term "epoxy" in that
it is descriptive of the molecule, not the finished properties of the fabric.
Some carbon can be had for as little as $12.00/lb (33 million modulus, i.e. 3
x as 'stiff' as fiberglass) and yet I've also worked with $4500/lb carbon that
is 120 million modulus, (11 times as resistant to stretch as glass). And the
strength was about twice, also. One characteristic of many of these higher
performance caron fibers is their NEGATIVE coefficient of expansion. That
means that when you heat it up, unlike almost all other materials, it actually
shrinks in heat, or in the case of the Aamoco carbon I was just talking about,
it has zero Ct. This makes it ideal for satellite antenna and camera mounts
since going in and out of the sun in the Earth's shadow doesn't cause it to
jump.
Well, that's enough from me which is too much for most. Give a holler if I
can help, I do have a lot of materials and contacts.
Dan Newland
Application engineer
Orcon Corporation
1570 Atlantic Street
Union City, California 94587
phone: (510) 476-2150
cell: (510) 290-6885
fax: (510) 489-6702
[The PDF file sent by Dan with this post has been uploaded to the "Materials & Supplies" page in the Attachments area on the LML website. <Marv> ]
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