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I don't want to imply that the
epoxy or polyester will burst into a roaring inferno at any hint of a
flame. I would expect that the prepreg/autoclave process that the main
structure is made from is somewhat resistant simply due to the fact that the
resin content per unit volume is quite a bit lower than what we get in a normal
lay-up. The mass of the non-combustibles act as a heat soak and helps to
keep the resin from reaching a high enough temperature that
it doesn't 'melt' (sort of, as much as a cross-linked plastic
can) as readily, at which state it will burn very readily. And
it is just the resin (epoxy or polyester or vinyl ester unless it is
brominated) that burns. However with sufficient heat from another
source, like electrical fire, fuel etc there will be plenty of heat to make up
for heat soak benefit of the non-combustible material so the resin will then
contribute to the fire.
Also remember that the HDT of
the resin (heat deflection temperature) is probably in the 300F range or lower,
(don't recall the actual numbers) so in the event of a fire that gets any part
hotter than that the structural integrity has pretty much disappeared.
Intumescent coating acts as a heat shield as well as creating a non-combustible
surface as it is exposed to the heat source.
Gary
R
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