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As you can see above, when the distance between skins is increased
to 4t, the stiffness increases by 37 times and
the strength increases by 9.2 times, yet weight is only increased
by 6%. Dream routinely produces sandwich cored
composites with 8-15+ t. |
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One of the driving factors for the performance of opto-mechanical
systems is stiffness. Without enough stiffness and thermal stability
in the structures, optical components (mirrors and/or lenses)
will not stay in alignment (tip/tilt, de-space, de-center), initially
causing off-axis optical performance to degrade and eventually
hurting even on-axis performance. A lack of stiffness can obviously
affect whole-field pointing and tracking as well, blurring the
image. In 2003 Dream realized Carbon Fiber skinned Sandwich Core
(CFSC) was an ideal choice for opto-mechanical systems. This
technology requires the proper choices for; sandwich core(s),
resin system, fabrication techniques, vacuum bagging, baking,
etc. It is the full combination of all choices, materials and
fabrication methods used that will determine the final performance
of the part. |
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Dream specializes in the use of sandwich core (both honeycomb
& foam), using specific carbon fibers & a high performance,
high temperature epoxy. Dream has been directly and indirectly
supporting precision optics with carbon fiber structures since
Dream's inception in 2003. Dream's advanced composite structures
have been used to support numerous mirror substrate types and
materials, from solid to engineered lightweight mirrors, from
ULE to borosilicates. |
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The other two main benefits of Dream's in-house composite parts
are that their CTE (Coefficient of Thermal Expansion)
is extremely low and it is more impervious to corrosion and chemical
attack. |
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When compared to metal or even solid laminate (no
core) carbon fiber parts of the same stiffness, Dream's Carbon
Fiber skinned Sandwich Core (CFSC) parts will be exceptionally
light. The right image shows ~1000 pounds of "live"
weight on a 16.0 pound CFSC Dream board (2' wide, 6' long and
1.1" thick). |
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There is an abundance of strength in Dream's parts.
Watch these dramatic videos
to see how rugged Dream's CFSC parts are. |
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There are parts where solid laminate CF is a better choice, like
small parts. But not for large, main structures; telescope/instrument
tubes, backplates, larger parts of the primary mirror mount,
etc. For those parts CFSC outperforms solid laminate hands down. |
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Solid laminate composites are easier for the average composite
shop to fabricate but they do not come remotely close to the
stiffness and therefore performance that is achieved using sandwich
core. This is why Dream specializes in CFSC use. |
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Dream's CF/CFSC mirror mounts are
achieving AND maintaining the surface of the mirror, as it moves
during real-world use, to a fraction of a wavelength of light.
This is an extreme mechanical requirement. |
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Dream's thick-walled sandwich
core tubes have no rivals, which is why we developed them
in the first place. They did not and still do not exist anywhere
else. Dream has unmatched experience & expertise with this
technology. Most applications desire lower moments of inertia
in order to accelerate, slew & decelerate faster, allowing
demanding project goals to be met. A stiffer structure also yields
better pointing, tracking & final performance because the
entire system is more rigid. When temperature is dynamic high
stiffness is not the only parameter that matters. Thermal stability
matters. Focus shifts are one thing but a mirror mount that is
far more athermal to the mirror and/or lens will distort that
optical less than traditional technologies. |
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Dream produces all of the inserts that we use inside the tubes,
mirror supports, etc., in-house. These threaded inserts are stainless
steel and have outstanding
performance, as tested indepenently by a lab. rocketry, IRAC, Spaceport America Cup, soundingrocket.org |
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