Damping of bromine-intercalated P-100 graphite fibers

A resonant flexural free decay test method was used to measure the damping of single pristine and bromine-intercalated P-100 graphite fibers in high vacuum, at temperatures from 77 K to 675 K, and at frequencies from 50 to 2000 hz. The damping capacity of the intercalated fibers was found to be significantly greater than that of the pristine fibers. For frequencies from 80 hz to 1300 hz, the pristine fibers exhibited two small peaks in damping capacity (~0.2%) in the vicinity of 145 K and 230 K, while the intercalated fibers exhibited one large peak (~3%) near 230 K. The activation energy of the mechanism underlying the 230 K damping peak in the intercalated fibers is 0.44 eV, suggesting an atomic process. The peak is unsymmetrical in (1/T) and, at half the peak damping, is four to five times wider than that of a standard anelastic solid, indicating a broad distribution of relaxation times. The specific physical mechanisms underlying the observed damping in both the pristine and intercalated fibers remain to be determined.