(I don't do composites for a living, but I did a bunch in school, and a
friend of mine is a full-time composites engineer at a local aerospace
joint. What follows are my opinions, hard facts would require that I
consult with the expert who's had his 240z taken apart on my lift for the
past 3 months.)
Prepreg is the only way to go. The beauty of prepreg is that just the right
amount of resin is already very evenly distributed, and the resin was very
accurately measured out and well mixed, too. It's also much less messy than
wet layup.
The vacuum bag helps get the fiber pressed into exactly the shape of the
mold, and also makes sure the various layers are pressed together tightly
enough to bond well. All you need is some heavy clear plastic, something to
the seal the edges with (weatherstip, or better yet that zinc chromate putty
strip stuff often sold as "roll caulk") and a vacuum pump.
A vacuum pump can be one of those venturi deals you use with your
compressor, or, like mine, a bastardized compressor from an old
refrigerator. (The freon had been emptied in an EPA approved manner.)
Autoclaves are fun, but not necessary for home use. Obviously, they require
that you vacuum bag the part, or else all the pressure in the world isn't
helping you. If you get the bag sealed well and pull a full 14.7 psi
vacuum, that's really pretty good. Understand that if you have any kind of
honeycomb core in the part, you may need to go easy on the vacuum or else
you'll crush the core.
Now all you need is an oven to cure parts in. This can be an old toaster
oven for small parts. For larger parts, build a box out of rigid styrene
insulation and cut a hole in one end to stick a heat gun in. Make sure you
don't melt/ignite the insulation, and yes this duty does wear out heat guns.
Parts can be trimmed with sabre saw, die grinder, band saw, etc. Unless the
part is really thin, or you're a real he-man, tin snips/aviation shears
won't cut it.
keithka
pictures of some of my wet layup work at:
http://vri.etec.wwu.edu/viking_xx.htm
-----Original Message-----
From: Mike Lee - Team Banana Racing [mailto:mikel@ichips.intel.com]
My thoughts are turned towards making some motorcycle parts out of carbon
fiber/kevlar;
Except for small pieces, autoclaving would be impossible for
me; is this always necessary, or can I avoid it by using pre-preg cloth.
wonder if vacuum bagging is absolutely needed if I stipple the resin enough;
I
believe the reason is to use less resin and save weight, but I think the
trade-off
What is used to trim the parts?
|