Al/SiC functionally graded and metal-matrix composites were investigated through dynamic mechanical analyzer as a function of vibrating frequencies. It was found that internal frictions were strongly dependent on material type and vibrating frequency. Tan delta reached 30.4 x 10(-3) and 21.2 x 10(-3)in FGM and MMC, respectively, at vibrating frequency of 1 Hz. The damping capacity decreased as the frequency increased to 10 Hz and 30 Hz. Storage moduli were 172 GPa and 144 GPa for FGMs and MMCs, respectively, at 1 Hz. Similar to Tan delta, storage moduli of the both materials were more sensitive to frequency change at higher temperatures. In general, higher storage moduli and damping capacities were observed in FGMs compared to MMCs.