Composite life expectancy

Tom-D

Tom-D

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Tom-D
Anyone know a good reference for the Epoxy resin life?
 
Infinite. It'll be just as strong 100 yrs from now as it is today. :) seriously though let met know the actual number. That way I'll sell my Glasair a few weeks prior to that.
 
Depends........don't you love those kind of answers ! What kind of epoxy, what kind of UV exposure, etc,etc,etc
 
When I purchased my aircraft there was no time limit specified,however I store outside 5 months out of the year so I cover the entire fuselage in canvas when outside.also wax the airplane several times a year.
 
Tom-D said:
Nice read, but I didn't see any reference to age.
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Are you asking about the life expectancy of finished structrures or the shelf life of uncured resin?

Assuming you are askng about the finished structures...

Fiberglass boats from the 1950's are still going strong (mostly built with polyester resins). The early glass giders are still in use - primary problems are with gel coat and some shrinkage of the resin. Some have life limits, but then, so do some aluminum gliders. Rutan's designs have been around for over 30 years. Creep can also a problem if they are left in the sun with a load. Fiberglass structures can have issues with fatigue.

I doubt that you will find any reliable source that says a finished structure is only good for xx years.

Is this a question about a specific aircraft or a quiz?
 
My only clue is my 1959 Glasspar G3, which has taught about 100 people to waterski, and now gets the crap beat out of it regularly on Priest Rapids Lake. From 15 ft it looks like new.
 
Much longer then its economic/useful life.
 
Saw one done by one of the euro geek assemblages of sailplane pilots/engineers that claimed 50,000 hours lifespan for composite airframes. Longer then metal, we'll have jet packs before the things are worn out.
 
ClimbnSink said:
Saw one done by one of the euro geek assemblages of sailplane pilots/engineers that claimed 50,000 hours lifespan for composite airframes. Longer then metal, we'll have jet packs before the things are worn out.
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Some of the oldest layups we have are old surf boards dating to the 50s. are they still as strong as when they were made? Seems no one knows.

Let's vary the question,
If you found a 30 year old LongEZ (as in a barn find) would you fly it? engine problems not considered.

How would you verify the A/F as airworthy/safe to fly?
 
Airframe is easy to verify. Turn it over and put on an appropriate cradle under the fuselage (a trestle up into the cabin to put the major load on the spar) Load the horizontal flying surfaces with shot bags to what ever + G-load makes you happy. (do the ailerons still work under load?)
Turn it over and do the same for your neg G-load
Side loading the vertical flying surfaces requires a bit more mickey mouse, but you can figure it out. I have confidence in you.

Engine - set up high speed blower(s) for cooling and beat the crap out of it on the ground. Remember to test the fuel valves, etc. at full power.
None of this requires a rocket scientist. :D
 
kgruber said:
My only clue is my 1959 Glasspar G3, which has taught about 100 people to waterski, and now gets the crap beat out of it regularly on Priest Rapids Lake. From 15 ft it looks like new.
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That's polyester, and the pre 1972 formulation which was considerably better than the post 1972 which requires post curing which nobody does.
 
The short answer is 'nobody really knows', but I'd say you're good for at least 25 years with anything but pure carbon layups, pure carbon layups have some issues. There are a lot of variables involved that can change the service life considerably.
 
The Glasfluegel H301 was certified in 1964 and many of the early ones are still flying. The Grob 109 type dates back to 1981, again I am not aware of any structural issues.

Now, how far would I trust a composite construction built by someone I dont know in his garage who has no established QA process and which cured under undocumented heat and humidity conditions ? I would trust it enough to hang it under the ceiling of an aviation themed bar or maybe turn it into a really fancy weathervane on top of my hangar.
 
Cap'n Jack said:
Tom- I'm deciding if giving input is _going_ to be a waste of time. If this is one of your trolling quizzes, like the link below, I won't bother giving input since you know the answer.

http://www.pilotsofamerica.com/forum/showthread.php?t=62031
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Treat it as you like. I really don't give a rat's A$$ what you do or don't do. there are people here that I value their opinions on subjects that I am not familiar with.

you, not so much.
 
weilke said:
Now, how far would I trust a composite construction built by someone I dont know in his garage who has no established QA process and which cured under undocumented heat and humidity conditions ? I would trust it enough to hang it under the ceiling of an aviation themed bar or maybe turn it into a really fancy weathervane on top of my hangar.
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As I talk to fellow pilots and mechanics I'm finding more and more of that attitude towards old composite aircraft.

Thus the thread, But I see no bases in fact for it.
 
Tom-D said:
As I talk to fellow pilots and mechanics I'm finding more and more of that attitude towards old composite aircraft.

Thus the thread, But I see no bases in fact for it.
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In my case this caveat is for old composite aircraft built by someone who did this for the first time.

Each of the manufacturers of composite aircraft had to take back an airframe or two and run them through the shredder. Cessna learned the hard way that you need to control the environment very tightly to get a consistent result.
 
Probably out of all the resins, Vinylester will be the safest if buying from a home builder.
 
Beech could not deliver on it's FAA contract to make this determination. That was a big deal.
 
bbchien said:
Beech could not deliver on it's FAA contract to make this determination. That was a big deal.
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Yeah, it's too flipping complicated to figure, just too many variables involved in both operational and construction issues to make that determination, the environment the structure lives in even makes a big difference as well.

There is not only how long the resin will last, but also how long the resin will hold onto the reinforcement matrix. I keep hearing there is 'no fatigue' to composite structures, but that's not what I see out in the field. Autoclaved & vacuumed prepreg materials go a long way to stabilizing the construction issues, but the operational and environmental will give a wide variety in durability and lifespan. I'll be interested in the 787 around 2020 to see how they are holding up.
 
Tom-D said:
Treat it as you like. I really don't give a rat's A$$ what you do or don't do. there are people here that I value their opinions on subjects that I am not familiar with.

you, not so much.
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That's too bad, Tom.

I try not to let my feelings for another get in the way of learning. So long as a person posts factual information, I don't let my personal feelings block what they do have to offer.
 
Cap'n Jack said:
That's too bad, Tom
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Yes it is too bad,, that you could not resist the temptation to inject your personal feelings into this thread.

When you have no answer to the first post, why post as you did?

Do you feel you must place your judgement on each post I make, Must I make posts that pass your requirements ?

Who are you to judge anything any one posts here? You hide behind a moniker and snipe at any one you feel is not in your good graces? At least there are several people here that have the personal integrity to use there names and be responsible for their opinions.
 
Tom-D said:
Yes it is too bad,, that you could not resist the temptation to inject your personal feelings into this thread.

When you have no answer to the first post, why post as you did?

Do you feel you must place your judgement on each post I make, Must I make posts that pass your requirements ?

Who are you to judge anything any one posts here? You hide behind a moniker and snipe at any one you feel is not in your good graces? At least there are several people here that have the personal integrity to use there names and be responsible for their opinions.
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I really didn't inject any feelings. I only asked if it were one of your quizzes, to which you already know the answer. Nothing more or less.

No judgement is being made. If it's a quiz, I won't play.

Finally, my name is really "Jack", so no hiding behind any moniker. I do try to reply with factual information, and make it clear when it is my opinion.
 
Tom-D said:
Some of the oldest layups we have are old surf boards dating to the 50s. are they still as strong as when they were made? Seems no one knows.
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The answer is quite clear. It depends. Heat, UV, over stressing - bad. Otherwise, OK.

Let's vary the question,
If you found a 30 year old LongEZ (as in a barn find) would you fly it? engine problems not considered.
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No. I am flying under the sport pilot rules and a LongEZ does not qualify. Otherwise, it would depend on how it looks when I inspect it - same as any other homebuilt that one might buy.

How would you verify the A/F as airworthy/safe to fly?
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Rutan wrote some very specific instructions on how to inspect the composite structure. Age is not an issue. How flat the strands for the "spar" were laid is.
 
Cap'n Jack said:
D'oh! You're right.
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Yeah, I remember that paper from way back when I was working on a blister program in the late 80s.

The thing with laminates is there are so many bloody variables, you have multiple resins and multiple reinforcing materials and then the schedule provides an exponent to the variables of the results of the other two factors which all gets factored against environmental conditions both during construction and operation.

To me, the best long term laminate structure is wood with resorcinol, a urea based glue, with a Kevlar skin epoxied to it lol.
 
Henning said:
Yeah, I remember that paper from way back when I was working on a blister program in the late 80s.

The thing with laminates is there are so many bloody variables, you have multiple resins and multiple reinforcing materials and then the schedule provides an exponent to the variables of the results of the other two factors which all gets factored against environmental conditions both during construction and operation.
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True. That's one reason I think the 1972 polyester formulation you mentioned a couple of times is mostly anecdotal. I'm not saying nothing happened, but I will say lots of things happened. Some manufacturers started using chopped glass for hulls. I think, but can't prove, they knocked the MEKP concentration down which would affect cure time unless it was heated as you alluded (or increase the cure time), without the polyester formulation being changed. They may well have changed the polyester formulation as well although I find nothing to support that either.

Henning said:
To me, the best long term laminate structure is wood with resorcinol, a urea based glue, with a Kevlar skin epoxied to it lol.
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Yep, until someone manages to hole it, does a bad repair, and the wood dry rots. I've seen more than one "soft" deck.
 
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Cap'n Jack said:
True. That's one reason I think the 1972 polyester formulation you mentioned a couple of times is mostly anecdotal. I'm not saying nothing happened, but I will say lots of things happened. Some manufacturers started using chopped glass for hulls. I think, but can't prove, they knocked the MEKP concentration down which would affect cure time unless it was heated as you alluded (or increase the cure time), without the polyester formulation being changed. They may well have changed the polyester formulation as well although I find nothing to support that either.


Yep, until someone manages to hole it, does a bad repair, and the wood dry rots. I've seen more than one "soft" deck.
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Pre 72 polyester boats don't blister. Polyester resin was changed to meet the VOC requirements of the Clean Air Act. After that room temp cures of polyester matrices have pockets of uncured styrene which requires bringing it up to 90°C on a post cure. That is the ONLY way to solve a blister problem, everything else is expensive snake oil.

Wash your boat with salt water, and if you live on a fresh water lake, throw a bag of salt in the bilge, problem solved. As for soft decks, foam core is worse than wood.
 
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Henning said:
Wash your boat with salt water, and if you live on a fresh water lake, throw a bag of salt in the bilge, problem solved. As for soft decks, foam core is worse than wood.
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That's why I said "deck". Next time it rains, you get fresh water again.

Speaking of foam, and to get this thread closer to back on track, aren't many EAB planes made with foam cores? I seem to remember hearing that some of those are going bad, for the same reason as the foam decks you mentioned.

I'd think this would matter as much as the age of the plane and how it was stored and maintained.
 
Cap'n Jack said:
That's why I said "deck". Next time it rains, you get fresh water again.

Speaking of foam, and to get this thread closer to back on track, aren't many EAB planes made with foam cores? I seem to remember hearing that some of those are going bad, for the same reason as the foam decks you mentioned.

I'd think this would matter as much as the age of the plane and how it was stored and maintained.
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If you are leaving the boat parked, sprinkle rock salt on the deck.

Foam core is yet another exponent multiplier in the equation, closed cell or open cell? Stiff or pliable? What weight foam? What material foam? Scored or smooth? Is the foam factored in as a structural component or only to hold form? Is it drilled to hold reinforced resin plugs to connect between the skins?

High quality boats no longer foam core under the waterline due to delamination issues, and even above the water delamination can occur. The more we think we know about engineering with these materials, the more we find our assumptions incorrect or incomplete. Also while the resins are pretty stable, they are not ultimately stable and degrade at varying rates under varying conditions. The best FRP/GRP hulls are the old ones where the material overkill was enormous. Except for some Taiwanese manufacturers, this is no longer the case. Boats that would have a two inches of solid laminate in the hull now have 3/8 of an inch.
 
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