Notes about Carbon/Epoxy Pre-Preg Composites:
1. There's many different formulas of resin used in this type of heat-activated composite that have
varying reactive temperatures and recommended temperature-increase and cooling time schedules in
autoclaves. In making carbon/epoxy tubes, a typical heat-curing schedule might be: raise temp
over 1/2 hour to 180-degrees F. Maintain at 180 for 20 minutes. Raise to 200 and maintain for 20
min. Raise to 220 and maintain for 20 min. Turn off heat and let slowly cool to 100-degrees,
before removing. Store in an un-stressed position at 75-degrees F for two days, before using for
assembly. Let it sit un-stressed for 3 more days at room temperature. Do not paint or apply
surfacing agents until at least 5 days after curing. This is just one example and there could be
other types that require much different schedules. Make sure you have the manufacturer's curing
schedule for each type you use, although many people have their own versions they may use for
varying results in performance characteristics.
2. Carbon fiber can be a health hazard to the respiratory system, if it's cut, sawed or sanded.
Invisible little fibrils fill the air and special filter-masks must be used when working with
it. Ordinary fiberglass masks won't remove the finest and most dangerous particles. If you don't
know everything about properly and safely using it, I'd leave it alone.
3. Dry Ice (frozen carbon dioxide) will evaporate within a couple of hours if it rises above 15-
degrees F. Even if slightly-elevated temperatures above the recommended level during storage and
shipping do not appear to have caused polymerization or thickening of the resin, there may be
hidden degradation that will show up only when the finished products are put to hard usage (a
personal lesson learned the hard way). Sometimes such quality problems relating to the condition
of the resin during manufacture of the product, may take years to emerge and usually do so at the
worst possible time.
4. Personally, I don't like to use Pre-Preg material, especially for small, home projects. It's
harder to determine material quality than with the cold, wet, catalyst-activated composites I
mostly use. In this, the liquid resin and the fiber are kept separate until assembly and the
resin can be better evaluated for quality. In large, professional operations, the integrity of
Pre-Preg can be better monitored and such assembly plants have a more dependable pipeline for
materials delivery at top quality.
Steve McDonald