and stitch that into a band and you
get tape. If you make the bi-directional fabric super lightweight,
you get veil; take that bi-directional
fabric and change the weave to a
2x2 or 4x4 pattern and you can get
twill which easily forms around any
shape. The forms of fiber are ever
growing.
TTT’s robots are generally
heavily built with as much kevlar as
we can get our hands on as it is very
light but super absorbent to impact.
It can be harder to wet out and get
proper lamination but it is such a
wonderful material to work with
because it doesn’t itch when you
sand it. However, being so abrasive,
it is very difficult to cut.
Carbon fiber is our next most
used fabric and it is generally used
for strength and stiffness in key
areas. We tend to use a lot of tape
forms of carbon to keep narrow
segments straight. We also are guilty
of using it on our final layers on the
outside of the robot to give a sexy
black exterior that stuns the other
robots into submission.
Fiberglass is the cheapest and
most readily available material, and
TTT does use it heavily when we run
out of kevlar or need strength and
thickness. TTT also makes prototype
parts with fiberglass to make sure
the part will be successful before
wasting kevlar, as well as using it for
the molds we create for
such parts. We
sometimes come across
remnant materials which
may be specialty cloths
with Mylar coatings,
special weaves, or even
hybrid fabrics that
include carbon fiber
woven with kevlar, but
these materials are rare
and not quite right for
the average robot
builder.
From bottom to top,
you have a phenolic
honeycomb, kevlar
with a Mylar/aluminum
treatment, fiberglass,
carbon fiber, and
finally another layer
of fiberglass. All
these fabrics are bi-directional. When you
have your entire layup
schedule together, you
refer to it as a kit.
Beyond just
the fabric, you
then get into
core materials
which are
designed to add
thickness,
insulation,
structure, or
form. Various
types and densities of foam,
honeycomb, wood, or pretty much
anything that can be wet out and
jammed into a laminate can be core
material. Then, when you start
adding resin to the mix you might
have gaps or need special surfacing
which may require you to add
powders or materials directly to the
resin before application.
Sawdust, micro-balloons (glass
spheres), chopped up glass, carbon,
or kevlar may be added to the resin
to be used for a wide range of tasks.
The beauty of composites is the
flexibility of not only the standard
laminate, but the array of materials
in which you can use them.
Max Bond epoxy system from
Polymer Composites, Inc. This
would be the marine grade resin
two gallon kit as purchased
through eBay or directly through
the company. It is a 1:1 ratio mix
of part A and part B.
There may be a lot of
information about various fabric
materials that can be used
successfully in combat robots, but as
far as resins go there is one clear
winner: epoxy. Polyester, vinyl ester,
phenolic, polyurethane, and
bismaleimide resins just aren’t quite
capable of being what epoxy is.
Epoxy may be a bit more expensive,
but you just can’t beat its strength
and ease of mixing without using
dangerous catalysts.
Most epoxy types have a
standard two part system, but
make sure you read the exact ratio
of hardener to epoxy as per the
manufacturers instructions (as
well as the MSDS).
We have used
various epoxies at
various price levels
and have found a
lot of epoxy
manufacturers put
plastesizers and
sometimes just a
whole lot of junk that
adds nothing to the
strength of the resin
but merely increases
the volume.
Max Bond —
which is referred to as
a marine grade resin —
is one of the best
quality resin systems
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