Assessment of the potential for release of conductive fibers from advanced composites by means of thermogravimetric analysis and scanning electron microscopy

Abstract Recently, there has been concern over the effects of accidentally released conductive carbon and graphite fibers on unprotected electrical circuits. Because of their thermal stability, such fibers could be released by the involvement of a resin matrix composite in a fire. A simple method based on thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) has been developed which permits the assessment of release potential from such composites. Dynamic TGA is used to determine temperatures at which significant events such as onset of resin matrix decomposition occur. Isothermal TGA permits a determination of the time required to produce releasable fibers at a given temperature. SEM examination of residues from TGA experiments serves to characterize their physical state which, in turn, permits a more precise assessment of release potential. This method has been used to examine a large number of materials composed of several different fibers in a variety of thermoset and thermoplastic matrices. It is concluded that release potential varies inversely with resin thermal‐oxidative stability and directly with fiber stability. The matching of matrix resin char and fiber stabilities is especially effective in suppressing fiber release.