This is what I know about composites:

Getting started with composites costs about $140.  $200+ if you want to make big projects.

To have a composites "workbench" you'll need fabric, epoxy resin, epoxy hardener, and volumetric pumps for measuring out the right amount of goo.  (better than using measuring cups from your kitchen and just "guessing" that epoxy won't be poisonous).  Oh, and good scissors.  You can buy composite scissors, but I find that a dozen or so disposable Fiscars scissors work just fine.  To mix the epoxy goos, I typically use Solo cups and plastic spoons.  These are cool, because as the epoxy sets, it heats up and melts the solo cup.

To make an individual part, you'll need some garbage bags, Crisco, water, plaster of paris, maybe some 2X4's, and definitely some duct tape.

Follow the instructions on the plaster and be prepared to work fast.  Rub Crisco all over the part you're going to cast.  I haven't found the perfect way to make a cast, but use your gut feeling to avoid trapping tiny bubbles on critical surfaces.  You can stick your hand in the plaster to make sure bubbles aren't trapped against the surface.  Make sure to wash the plaster off your hands.

Fast forward to the point where you've put the fabric in the mold and are rubbing the mixed epoxy (2 parts go in) all over the place.  This is where you can use a big, tall garbage bag full of water to squish the composite into the mold.  This is actually a ghetto, car-craft, garage-version of "hydroforming".  They do this to make the headers for the new Corvettes.  It's like stamping sheet metal, but you can apply pressure in more than one direction.

You have about 20, 60, or 120 minutes to wait for the epoxy to harden and freeze the fabric in place.  Pop out your part and carefully drill any holes, trim any rough edges, and double check for fluid retention if it's important.

Here's a basic summary of the cool types of composites:

Carbon Fiber - very strong fabric, but will kind of splinter if you beat it up.  They use it to make drive-shafts, so it’s beastly.  Try to think of imaginary “bitchin-strong” lines that run along the “grain” of the fabric.  Currently being eaten up by China to build Boeing’s new airplanes.  Eats up scissors.

Kevlar – Not carbon fiber, but still very strong.  Will bend a little before it breaks, unlike carbon fiber.  Resists abrasion.  Is usually yellow.  Is a little better with scissors.

Fiberglass – Strong enough for interior and exterior parts that only need to resist human-type strength.  Pretty.  Cheap.  Fine with scissors.

Nomex – Amazing stuff.  They make this reinforced hexacore stuff that is essentially a paper honeycomb with lines of nomex running through it.  You can toss a building on top of it and it won’t flex.  People sandwich this stuff between carbon fiber to make stupid-strong “cardboard”.  Also good for making the flame-resistant pajamas worn by professional racers.

Hybrids – You can mix fabrics to get a best-of-both-worlds-sort-of result that has the colors of both fabrics and a blend of their strengths and weaknesses.  Before China ate all the carbon fiber, hybrids were easy to find on eBay and websites that Google can find.

Epoxies: You need resin, and you need hardener.  There are different types of hardeners that harden in short or long lengths of time.

Edited 12/25/2006 7:15 pm by thisispeace

I'm a moron.  This article title is a mispelling of "Composites".

Not "camp sites".

what do you reccomend for producing a flexible part? something that is essentially a rubber trim piece on a car. ive been messing with trying to reproduce something and ive been havng a hard time getting something flexible enough to work. is there a rubberized style epoxy out there that will work yet still accept coatings? (paint, dyes, texture coating etc..)

any reccomendations on a more permanent mold unlike plaster of paris that can be used for making those parts as well? thanks.

What kind of flexibility are you looking for?  I can't think of a rubber trim piece that I've seen.  Is it part of a bumper?

Most epoxies are pretty stiff, but you might be able to use another process altogether.

A lot of people use silicone to make molds (the way I make plaster of paris).  In your case, you can use it to make both flexible parts and molds.  Remember to put bolts or threaded rod into the part before it cures so you have a way of securing it (unless you prefer trim glue).  Check out how it looks:

http://www.cs.cmu.edu/~rapidproto/manufacturing/molds/silicone.html

I think silicone molds are a little more resilient than plaster molds.  Hard enamel paint should make plaster molds a little more permanent, too.  I can't think of the next-best mold material, because I tend to cheat and use a CNC mill to carve one out of aluminum.

the link helps, so ill keep an eye out for that.

the piece i want to make isnt a bumper trim piece, its basically a dash delete plate that is made out of a flexible rubber instead of a rigid piece of plastic. ive tried some flexible bumper repair products when i was working at a paint store with some mild success. my only problem is that it became very rigid when it was cold outside and my concern was that the drastic change in flexibility might lead it to crack after it cycles enough times.