Adam,
It is difficult to spend the time making a reply. I am not an engineer and I did not play one on TV -but- there is plenty of literature concerning "composite" construction. Composite generally meaning a matrix (fiberglass, carbon fiber, kevlar, wood fiber) and a bonding agent (epoxy, glue) thus we end up with results that have certain properties, like our glass/carbon construction and plywood. There are many weaves of glass and carbon cloths and even more "epoxies" with certain designed properties.
The kinds of epoxies we use, consisting of a resin and a hardener, are brittle when cured if there is no matrix or the matrix was too wet. If you were a builder, you could go out to your shop and take that excess cured epoxy sitting in the mixing cup and whack it with a hammer - it would probably shatter. Using the proper techniques and materials, there is no known life limit and no natural enemy of glass/epoxy combination save for ultraviolet radiation.
BTW, everything is porous at the microscopic level, especially molecules with those goofy atoms and silly electrons spinning around in space. Perhaps he should contact Boeing, the Rutan boys, Diamond Aircraft, Cirrus, Lancair and all the composite kit companies about his paper - - By golly, I am going to run out and watch my 320 disintegrate before my very eyes since the moldings were done in 1989, a whole 14 years ago. Maybe this guy should stick to something like the chemical composition of Jalapena peppers - that complex demonic chemistry attacks every useful orfice of the human body.
Scott Krueger
Sky2high@aol.com
II-P N92EX IO320 Aurora, IL (KARR)
In a message dated 10/24/2003 12:13:06 PM Central Daylight Time, propjet882aw@cox.net writes:
I recently had a disconcerting conversation with an engineer. Like me, he was also a flight enthusiast. Unlike me, he was not thrilled with my dreams of fast glass. (For the record, I didn't mention any specific model--I just told him I was looking at a cross-country cruiser and an amphib. Because of this, I know he didn't have any bad experiences and was biased against them.) Later I learned why he was dismayed. It was not because of the composite construction--it was because of the epoxy that we use for the structural adhesive. When I asked him what he meant, he told me that he had published a paper on it. He then proceeded to tell me about how epoxy is hard, brittle, and porous (on a microscopic level). The first trait I thought was a good idea. The second two I wasn't too sure about. He explained to me that the issue that worried him was fatigue. NOT of the composite structure but the epoxy itself. In a traditional metal aircraft, you can x-ray structures to determine their state of fatigue and replace the hinge pins, bolts, etc if needed. He said that you can not do this w/ the epoxy. In a nutshell <these types of joints don't fail little by little. When they fail, they fail catastrophically and we have no way of determining when that will be>. I don't know if he is talking about delamination or what--I'm still a low-time PP.