ENHANCED COMPOSITE PLATE DAMPING USING INTERCALATED GRAPHITE FIBER

The increased vibration damping capability of bromine-intercalated gra phite fibers has been recently reported. Continuing investigation of t he use of such fibers in structural composite materials has demonstrat ed increased flexural damping of unidirectional, brominated P-100 grap hite/epoxy composites. Damping was measured at temperstures ranging fr om -120 to +30-degrees-C and at frequencies from 50 to several 100 Hz. As expected on the basis of constituent fiber and matrix damping char acterization, the observed damping was both temperature- and frequency -dependent. The peak modal damping ratio observed for pristine fiber c omposites Was 0.8 X 10(-3), whereas that exhibited by the brominated f iber composites was 1.6 x 10(-3). Theoretical predictions of composite specimen modal damping ratios based on known fiber and matrix propert ies are in reasonable agreement with experimental data. Discrepancies may be due to imperfect intercalation or to the effects of the fabrica tion environment on intercalation stability. Analytical results obtain ed for additional cases and materials indicate that 1) contrary to sta te-of-the-art design principles, the damping of quasi-isotropic compos ites made using intercalated graphite fibers could be dominated by fib er damping instead of matrix shear damping; and 2) damping levels of s ignificance could be achieved.