|
|
|
|
|
|
Dream was created to
make advanced composite technology
more accessible to opto-mechanical customers. Advanced composites,
when designed properly and for a specific need, can far surpass
the strength, stiffness and lightweight characteristics of today's
metals. Their CTE's can be substantially lower (and in specific
cases negative CTE's are possible) than common metals. Click
here to see a comparison showing why advanced composites
are so beneficial compared to metals. |
|
|
|
Dream's specializes in the use of advanced composites,
mostly carbon fiber, in combination with sandwich core technology.
To learn more about the enormous benefits of sandwich core, click here. |
|
|
|
|
Dream was also
created to push past boundaries both in telescope & accessory
designs. An attempt is made at every turn to use composites instead
of metals, both for thermal stability and light-weighting. The
latter can have thermal benefits for the instrument, as well
as stiffness benefits. Thermal
characteristics can far outway other criteria in a telescope
system. But stiffness will always be one of the core requirements
of any opto-mechanical system. Optimizing the performance of
both the thermal aspects and the stiffness of the system can
allow the utmost in performance and the highest throughput. |
|
|
Many companies
use carbon fiber products that have a clear, glossy finish. This
leaves the part with one of two commonly used weave patterns,
2x2 twill or plainweave. Unfortunately this also leaves the part
charcoal black. This color exterior will heat up the interior
of the OTA and therefore the optics, when exposed to the Sun.
It will take that much longer for the optics to cool down. Dream
has tested black surfaced materials in moderate temperatures,
70°F, and found that they easily reach 160°+ degrees
in the Sun! This is a potential problem for all composite parts,
not just opto-mechanical products. Please read below for an explanation. |
|
|
|
Using bright white (some
silver paints work too) greatly reduces the amount of heat buildup
and therefore promotes the quickest equilibrium times. Excess
heat in advanced composites can also facilatate a breakdown of
the laminate, especially with room temperature cured resins.
Layers of reinforcement (fiberglass, carbon fiber, etc.) will
start to delaminate from each other, for example, if a temperature
threshold is exceeded. This can be prevented by using high temperature
epoxy that allows cooking the advanced
composite parts. This raises their properties so that they do
not have delamination issues, if designed and produced correctly.
Dream has always used a specific high temperature, high performance
epoxy (~$110/gallon) that can be cured at up to 350F, if the
application requires it. This also allows us to produce mirror
mounts, backplates, telescope structures, etc., that are close
to 1ppm/°C of the mirrors that we use. |
|
|
In sandwich core use temperatures are again a factor
that must be considered. Some foams and honeycombs ($100-$300
per 4'x8' sheet) can only withstand temperatures of 230°-250°F.
If the product will see temperatures above this, specialized
cores like Nomex honeycombs or Rohacell
foams can be used ($250-$700+ per 4'x8' sheet). |
|
|
To learn more about the background
of Dream and elevated temperature epoxy, click
here. |
|
|
Epoxy resins are
UV sensitive, as are most resin systems. They will degrade if
directly exposed to UV rays. Composites should always be protected
with a UV barrier layer(s) to help increase the longevity of
the product. |
|
|
|
To learn more about advanced composites,
click here. |
|
|
|
|
|
|
|
|
