Dynamic effect on strength in SiCf/SiCm composite

Loading rate dependence of mechanical properties of SiC fibre-reinforced Si C composites (SiCf/SiCm) has been experimentally investigated as to the fib re volume fraction and coating materials for SIC fibre. The composites cons isting of monolithic SiC and SiC fibre (Hi-Nicalon) coated with Boron-Nitri de (BN) or Carbon (C) with fibre volume fractions of 20, 30 and 40% were fa bricated by polymer infiltration-pyrolysis (PIP) process. The stress-strain response and strength were measured in tension over a wide range of strain rate,10(-4) similar to 200 s(-1). It was shown that the higher volume frac tion, the larger tensile strength regardless of the kind of coating and str ain rate. The interface friction stress evaluated by the fibre pullout leng th that is measured through microscopic observations of fractured specimens is larger in dynamic loading than in static loading. The BN-coated fibre g ave the composite superior tensile strength to the C-coated fibre. This tre nd results from the variety of the interface friction stress associated wit h the coating thickness. (C) 2000 Elsevier Science Ltd. All rights reserved .