Internal friction behaviour of carbon fibre reinforced multilayered (PyC–SiC)_n matrix composites

Carbon fibre reinforced multilayered (PyC–SiC)_n matrix (C/(PyC–SiC)_n) composites were prepared by alternate deposition of pyrocarbon (PyC) and SiC inside preforms via chemical vapour infiltration. The matrix microstructures and internal friction behaviours of C/(PyC–SiC)_n composites (n = 1, 2 and 4) under different testing conditions of frequency, strain amplitude and temperature were studied. The results show that with increasing the number of sequences (n), the internal friction increases due to the enhancement of interfacial internal friction. The internal friction of C/(PyC–SiC)_n composites increases with the increase of frequency related to thermoelastic mechanism, but exhibits anomalous amplitude effect in the testing amplitude range. Effect of temperature on internal friction behaviours is attributed to combined effects of carbon fibres, PyC–SiC matrices and interfaces between fibres and PyC, adjoining PyC and SiC layers. It is also found that internal friction is sensitive to microstructural defects induced by damage. These results indicate that internal friction is an effective and efficient method to characterize the structural evolution and internal damage of C/(PyC–SiC)_n composites non-destructively.