Thermomechanical behavior of a graphite foam

The thermomechanical behavior of a graphite foam derived from pitch for use in thermal management was studied in air up to 150 degreesC. The damping capacity or loss tangent under flexure was 0.17 at 30 degreesC for the graphite foam, compared to 0.02 for conventional graphite (not a foam), 0.15 for flexible graphite and 0.22 for PTFE. The loss tangent of the graphite foam decreased with increasing temperature, whereas that of conventional graphite did not. The compressive strain of the graphite foam strongly depended on time, compressive stress and temperature. Due to creep at 30 degreesC, it reached 3% at 200 kPa, in contrast to 0.7% for conventional graphite. Thermal softening increased the compressive strain in the graphite foam upon heating and subsequent cooling, such that the thermal expansion phenomenon was overshadowed. In contrast, thermal softening was less in conventional graphite. The storage modulus of the graphite foam under flexure was lower than that of conventional graphite. Its fractional decrease with increasing temperature was more than that of conventional graphite. (C) 2003 Elsevier Science Ltd. All rights reserved.