Influence of oxidation inhibitor on carbon-carbon composites: 1. Degree of graphitization and mechanical behavior

PAN-based carbon fibers impregnated with phenolic resins used as a precursor of carbonized matrix were modified by addition of molybdenum disilicide (MoSi₂) in different concentrations, i.e., 0, 4, 12 and 20% by weight. And, unidirectional carbon fiber-reinforced phenolic matrix composites were manufactured by prepreg method, and were submitted to carbonization (heat treated to 1100 °C) and graphitization (to 2300 °C), throughout one step manufacturing process. In this work, the influence of MoSi₂ concentrations having the physical properties of oxidation inhibition and brittle-to-ductile transition (BDT) at higher temperatures was investigated in interlayer spacing (d₀₀₂). flexural strength (σ_f), and interlaminar shear strength (ILSS) of the composites. As a result, the additions of 12-20 wt% MoSi₂ to the composites received after graphitization showed that the flexural strength of the composites was improved in a result from about 200 MPa to 360 MPa. This is due to the increase of bulk density or decrease of open porosity and decrease of d₀₀₂ of the graphitized composites.