NormMessinger
11-13-2001, 08:59 AM
I can't speak to the wood part but here is something relevant to the epoxy part. Gary Hunter, you may remember from other stuff of his I've posted, is the epoxy answer man for Shell.
Patrick writes:
Has anyone ever done a realistic study as to what the realistic
life expectancy is with cured resin? It seems that with each passing day, we
are adding another day to the unknown expected life.
What I mean, is that if in say 3 years, we find out that saf t poxy
or aero poxy has a life of 30 years, 40 years or whatever.....
That "time life" might devastate our endeavors, or at least the
value....knowing that we are building an aircraft good for no more
than XX years....
Is there any factual data about this topic anywhere?
PLEEAAAZZZE don't start this rumor. This subject has been studied
thoroughly. I will be more than happy to mail you a copy of a paper
presented in 1980 by Grumman Aersopace titled REAL LIFE AGING PROPERTIES OF
COMPOSITES. The paper was written after 20 years of data collection on
various different types of fiber reinforced epoxy composite materials
exposed to environmental extremes our hand built lover affairs will never
see. The reason for the study was that up until that point, only
accelerated aging tests had been conducted and results indicated one can
expect considerable amounts of degradation. This was an unexpected result,
and they needed verification and correlation from a "real life" aging study.
I quote from the section - Discussion of Results - Fiberglass Laminates.
"The data presently available from accelerated aging tests on fiberglass
components invariably show considerable amounts of degradation. Therefore,
it has been assumed by most users that such degradation must be expected in
service. The data obtained under this program for specimens machined from
parts exposed to various climatic conditions under service loads show that
for properly protected structures the degradation for periods of up to 20
years is either MINOR or NON-EXISTANT. (In many cases a strength increase
was observed)." - end of quote. Caps added by this author.
The phrase "properly protected" quite simply means - painted.
I am 110% confident, that if they had tested the same components today, the
conclusion would be the same except it would state for "up to 41 years."
Because such a study takes so much time, the information if provides is
extremely valuable. It also strongly indicates that one should not depend
solely on accelerated aging test methods for this particular application.
ANY ONE who wants a copy, send me your address and I'll drop it in the snail
mail.
Gary Hunter
EAA Technical Counselor
Patrick writes:
Has anyone ever done a realistic study as to what the realistic
life expectancy is with cured resin? It seems that with each passing day, we
are adding another day to the unknown expected life.
What I mean, is that if in say 3 years, we find out that saf t poxy
or aero poxy has a life of 30 years, 40 years or whatever.....
That "time life" might devastate our endeavors, or at least the
value....knowing that we are building an aircraft good for no more
than XX years....
Is there any factual data about this topic anywhere?
PLEEAAAZZZE don't start this rumor. This subject has been studied
thoroughly. I will be more than happy to mail you a copy of a paper
presented in 1980 by Grumman Aersopace titled REAL LIFE AGING PROPERTIES OF
COMPOSITES. The paper was written after 20 years of data collection on
various different types of fiber reinforced epoxy composite materials
exposed to environmental extremes our hand built lover affairs will never
see. The reason for the study was that up until that point, only
accelerated aging tests had been conducted and results indicated one can
expect considerable amounts of degradation. This was an unexpected result,
and they needed verification and correlation from a "real life" aging study.
I quote from the section - Discussion of Results - Fiberglass Laminates.
"The data presently available from accelerated aging tests on fiberglass
components invariably show considerable amounts of degradation. Therefore,
it has been assumed by most users that such degradation must be expected in
service. The data obtained under this program for specimens machined from
parts exposed to various climatic conditions under service loads show that
for properly protected structures the degradation for periods of up to 20
years is either MINOR or NON-EXISTANT. (In many cases a strength increase
was observed)." - end of quote. Caps added by this author.
The phrase "properly protected" quite simply means - painted.
I am 110% confident, that if they had tested the same components today, the
conclusion would be the same except it would state for "up to 41 years."
Because such a study takes so much time, the information if provides is
extremely valuable. It also strongly indicates that one should not depend
solely on accelerated aging test methods for this particular application.
ANY ONE who wants a copy, send me your address and I'll drop it in the snail
mail.
Gary Hunter
EAA Technical Counselor