Internal friction behavior of carbon-carbon composites

The fundamental internal friction behavior of carbon-carbon composites is studied. Two internal friction mechanisms are proposed according to the special internal friction characteristics in carbon-carbon composites. A thermoelastic mechanism, which is independent of amplitude, mainly leads to the internal 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 abnormal internal friction phenomena can be observed. The variation characteristics of internal friction and dynamic modulus versus temperature in carbon-carbon composites are quite different from other materials. This special behavior may be a result of interfacial CTE effects, as well as the coordination effects of the individual response of the fibers, matrix and interface of carbon-carbon composites. Finally, the validity of internal friction analysis methods for densification process monitoring and non-destructive inspection of carbon-carbon composites is discussed for the first time. The results indicate that internal friction testing methods have great potential for monitoring process and inspecting components of carbon-carbon composites non-destructively. (C) 2000 Elsevier Science Ltd. All rights reserved.