P. Fino, M. Pavese (Sp), Politecnico di Torino (Italy); L. Scatteia, G. Marino, CIRA - Italian Aerospace Research Centre, Capua (Italy); A. Ortona, FN S.p.A., Boscomarengo (Italy); C. Badini, Politecnico di Torino (Italy) 
 
The suitability of a 2D SiC/Cf composite for fabricating the nose of a re-entry space vehicle has been investigated. To this purpose the detrimental effect of oxidation on the composite mechanical characteristics as well as the effectiveness of a protective SiC coating deposited by CVD have been studied.
Composite specimens were processed at FN S.p.A. (Boscomarengo, Italy) according to the following fabrication route: preparation of a preform by stacking fabrics of T300 carbon fibres, realisation of SiC matrix by several repeated cycles consisting in polymer impregnation (with a solution containing allyhydropolycarbosilane), pyrolysis and thermal treatment.
A second set of samples was obtained by chemical vapour deposition of a SiC layer on the composite surface.
Composite mechanical behaviour and microstructure were investigated by carrying out tensile, bending and compressive tests (at different temperatures); XRD, SEM, thermo-mechanical and porosimetric analyses (with nitrogen adsorption and Hg intrusion techniques).
Preliminary tests of thermal stability and oxidation resistance were peformed by simoultaneous TGA, DTA and Mass spectroscopy analyses.
Mechanical tests and material characterization were repeated after submitting both uncoated and SiC-coated specimens to isothermal oxidation treatments performed in air at 800 °C and 1600 °C.
Thermal stability of both un-coated and SiC-coated smaples was found to be excellent.
However, the un-coated composite, as expected, is prone to undergo strong oxidation starting from 500 °C. Oxidation at 1600 °C results in a dramatic worsening of strength (which decreases of more than 60%) and stiffness (Young’s modulus lowers of about 50%); important changes of other physical features (mass loss about 23%, decrease of density and thermal expansion coefficient, increase of specific surface area) were also observed.
The SiC surface coating greatly increases oxidation resistance of composite, but it is unable to avoid oxidation completely; for instance isothermal oxidation at 1600 °C causes a strength decrease of about 20%. Unfortunately, the efficiency of this surface coating is compromised by rapid changes of temperature, which cause coating damage owing to stresses arising from thermal expansion mismatch between the composite and the coating itself.