The thermal expansion behavior of Ni matrix composites reinforced with multiwalled carbon nanotubes (MWNT) fabricated by pressureless sintering and hot uniaxial pressing was studied in the range between 50 and 1050 °C and compared to that of pure Ni. The results show an active interaction between the MWNT and the Ni matrix by reducing the coefficient of thermal expansion (CTE) of pure Ni up to 76% between 50 and 400 °C. This reduction is due to the strong interfacial interaction between the matrix and the reinforcement and the low intrinsic CTE of the nanotubes. This outstanding behavior may be very useful in applications were low CTE is required as for example structural materials.

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Evaluations of the fracture toughness in metal matrix composites (Duralcan reinforced with 15% of Al(2)0(3) and SiC) are presented in this work. The application of Elastic Plastic Fracture Mechanics is discussed and the obtained values are compared with the ones obtained by means of Linear Elastic Fracture Mechanics. Results show that J IC derived K JC values are higher than the corresponding values obtained by direct application of the linear elastic methodology. The effect of a heat treatment on the material fracture toughness was also evaluated in which the analyzed approaches showed, not only different toughness values, but also opposite tendencies. A second comparison of the J IC and K JC values obtained in this work with toughness values reported in the literature is presented and discussed