Dynamic effect on strength in SiC_f/SiC_m composite

摘要

Loading rate dependence of mechanical properties of SiC fibre-reinforced SiC composites (SiC_f/SiC_m) has been experimentally investigated as to the fibre volume fraction and coating materials for SiC fibre. The composites consisting of monolithic SiC and SiC fibre (Hi-Nicalon) coated with Boron-Nitride (BN) or Carbon (C) with fibre volume fractions of 20, 30 and 40/100 were fabricated 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 ～ 200 s~-1. It was shown that the higher volume fraction, the larger tensile strength regardless of the kind of coating and strain rate. The interface friction stress evaluated by the fibre pullout length that is measured through microscopic observations of fractured specimens is larger in dynamic loading than in static loading. The BN-coated fibre gave the composite superior tensile strength to the C-coated fibre. This trend results from the variety of the interface friction stress associated with the coating thickness.