Dynamic Mechanical Properties of Graphite-Epoxy and Carbon-Epoxy Composites

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Abstract
Dynamic elastic moduli and damping of carbon- and graphite-filled epoxy composites have been measured over the temperature range of 85 to 300° K. The epoxy resin matrix was cured with diethylenetriamine. Dynamic elastic moduli increase with filler content in both cases; however, graphite powder is more effective than carbon powder in increasing the modulus. For the graphite composite, experimental data agree with Wu's equation for disk-shaped filler particles with a modulus of 56 × 1010 dyne/cm2. For the carbon composite, experimental data cannot be effec tively compared to any theoretical model, probably because the carbon powder is composed of agglomerated particles. The effect of voids on the dynamic modulus of a particulate composite is also discussed. The β damping peak (∼ 250° K) does not change in its intensity with filler con tent, while the intensity of the γ peak (∼ 150°K) is decreased as the amount of filler is increased. The relation between the filler content and the intensity of the β peak suggests that damping in the composites in cludes a component due to friction at the interface between the filler and matrix. The decrease in the y peak with filler content may be explained by interaction between the filler surface and unreacted epoxides