Papers by Author: Masaki Shibuya

Abstract: SiC fabric including SiC (60 vol%)-Al2O3 (40 vol%) mixed powders and SiC (60 vol%)-Al2O3 (40 vol%) sheet of 60 μm thick were alternatively laminated and hot-pressed to 79 - 83 % of theoretical density under a pressure of 39 MPa in an Ar atmosphere at 1600 °C. Four cracks were formed on the polished laminates with 30 ± 3 and 43 ± 2 vol% SiC fabric along the center line perpendicular to the direction of length by Vickers indentor at the load of 98 N and healed in air at 1100 °C for 24 h. The strength (253 MPa) of the as-hot-pressed laminate without SiC fabric decreased to 119 MPa after the introduction of the cracks but was recovered to 336 MPa after the healing. The crack size decreased because of the oxidation of SiC particles during the healing. However, the laminates with SiC fabric had a high damage tolerance and gave no change in the strength (~100 MPa) after the introduction of the cracks. The SiC fabric prevented the propagation of the cracks. After the healing, the porosity of the laminates decreased owing to the volume increase during the oxidation of SiC particles and SiC fabric. The strength of the healed laminates was comparable to that of as-hot-pressed laminates.

Abstract: A polytitanocarbosilane (20-30 mass%)-xylene solution was infiltrated into a porous laminated composite with 35-40 vol% Si-Ti-C-O fabric of 11 diameter fiber and 15-25 vol% mullite filler, and decomposed at 1000°C in an Ar atmosphere. This polymer impregnation and pyrolysis method was repeated 8 times to produce the composites of 76-82 % theoretical density. The yarn (662-765 filament / yarn), fabric and composite provided the following average strengths : 1240 MPa for the yarn; 768 MPa for the fabric; 117 MPa for the composite. The fracture probability of the yarn, fabric and composite was well fitted by the normal distribution function. The tensile strength of the composite was interpreted by the product of the effective fiber content, the Young's modulus of the fiber and elongation of the composite.