Internal friction behavior of carbon-carbon composites

The fundamental internal friction behavior of carbon-carbon composites is s tudied. Two internal friction mechanisms are proposed according to the spec ial internal friction characteristics in carbon-carbon composites. A thermo elastic mechanism, which is independent of amplitude, mainly leads to the i nternal friction increase with increasing frequency. The other is a static hysteresis mechanism that internal friction depends on the amplitude but is independent of frequency. Moreover, it is very interesting that some abnor mal internal friction phenomena can be observed. The variation characterist ics of internal friction and dynamic modulus versus temperature in carbon-c arbon composites are quite different from other materials. This special beh avior may be a result of interfacial CTE effects, as well as the coordinati on effects of the individual response of the fibers, matrix and interface o f carbon-carbon composites. Finally, the validity of internal friction anal ysis methods for densification process monitoring and non-destructive inspe ction of carbon-carbon composites is discussed for the first time. The resu lts indicate that internal friction testing methods have great potential fo r monitoring process and inspecting components of carbon-carbon composites non-destructively. (C) 2000 Elsevier Science Ltd. All rights reserved.