|
|
|
Advanced composites possess
a characteristic called the glass transition point, Tg. If the
product is subjected to temperatures past the Tg, performance
(stiffness and strength) will diminish. Delamination, warping,
vastly reduced properties and other problems can occur at temperatures
above the Tg of the composite matrix. Strength, stiffness and
all other physical and thermal properties are affected by temperatures
higher than the Tg. Even if the part hasn't reached the Tg temperature,
typically a part's properties start to fall off before that Tg
temperature is reached. It has a larger affect than one might
think, even at lower than Tg temperatures. |
|
Even though Dream
has always used epoxy, it is not enough to fabricate them at
room temperature. Room temperature cured epoxies ($17-$65 per
gallon) have a maximum Tg of about 120-140F. These are resins
that are not designed for an elevated temperature cure cycle.
Cooking low temp resins DOES NOT allow them to have an increased
Tg point and/or increased performance. It merely degrades or
ruins the resin. |
Dream uses epoxy a specific epoxy because it has higher
properties than other resins. This includes its adhesion performance.
It is more expensive, $125+/gallon, but we feel the performance
gains are worth the investment. |
|
Early on Dream conducted
tests on a black surfaced material in Sunlight. The surface temperature
went to 164F, even though the ambient temperature was only 70F.
Summers in Arizona and New Mexico can average ambient temperatures
of 100-120F. This will easily push the surface temperatures of
black/dark materials to over 200F. Therefore the use of products
that were made with conventional room temperature epoxies or
resins (vinyl-ester or polyester) in direct Sunlight, even on
very mild days, pass the Tg of most resin systems. This is the
reason all home built aircraft that use non-elevated cure resins
are painted white or a very light color. |
|
|
All composite parts,
including secondary bonded areas, are cooked in a computer controlled
oven ($45,000+), among other pieces of equipment. The interior
of the oven to the left is 6'x12'x6' (LWH) or 432 cubic feet.
The oven can easily handle 1m telescope structures. Recently
upgraded. Dream currently uses a high temp epoxy that
can be cooked as high as 350F, if the application calls for it. |
|
|
Dream is always striving for the ultimate in performance.
Dream's products can hold up
to extreme physical and environmental conditions. |
|
To learn more about advanced
composites, click here. |
|
|
|