Carbon Foam Tooling Moisture Comparison

Not All Carbon Foams are Alike

Customers looking for carbon foam tooling need to understand that all carbon foams are not created equal.

Recently, Touchstone has become aware that composite tools – with phenolic-resin based carbon foam – have failed due to an internal pressure increase of the composite tool during composite part curing.

This can destroy both the part and the tool.

carbon_foam_coal_based carbon_foam_phenolic_resin_based

Touchstone investigated the claims and found the following:

  • Two kinds of carbon foam are commonly used to make composite tooling, those manufactured from coal – such as CFOAM® – and those manufactured from a phenolic resin-based foam.
  • While the external morphology of both carbon foams is similar, major differences in their physical properties exist.
  • Touchstone theorized that carbon foams manufactured from phenolic resins adsorbed a large quantity of water.
  • It was the Touchstone scientists’ experience that carbon foams manufactured from coal, such as CFOAM carbon foam, do not exhibit this phenomenon.
  • A confirming experiment was performed. Panels of phenolic resin-based carbon foam and coal-based carbon foam, were placed on balances in an environmental chamber which controls temperature and humidity. The mass increase for each was monitored.

Carbon Foam Tooling Moisture Humidity Study


Experimental Method

Carbon foam tooling moisture humidity study.

  • Each sample was placed on a balance inside an environmental chamber at 90° F (32° C) and 85% relative humidity for 24 hours.
  • Balances were connected to a data logging computer which recorded a mass reading from the balance every 20 seconds.


  • Phenolic-based carbon foams increased mass 13.3 percent in 24 hours.
  • Carbon Foams made from coal increased mass only 0.3 percent in 24 hours.
  • During the manufacture of a composite tool, a tool surface is typically applied to the carbon foam and most surfaces are covered. Upon heating of the tool in the autoclave or oven, the moisture converts to steam – building up pressure in the tool – blowing off the surfaces. This appears to be the failure mode for phenolic-based carbon foams, with their higher moisture adsorption rate.
  • Tools made from coal-based carbon foam don’t exhibit this issue, and have successfully been made and used by Touchstone and its customers for over five years.

CFOAM® is a registered trademark of Touchstone Research Laboratory, Ltd.
CFOAM® products may be covered under the following patents with more patents pending:
6,656,238 – 6,656,239 – 6,689,470 – 6,749,652 – 6,814,765 – 6,833,011 – 6,833,012 –
6,849,098 – 6,860,910 – 6,861,151 – 6,869,455 – 6,899,970 – 7,192,537 – 7,247,368