Fabrication of short C fiber-reinforced SiC composites by spark plasma sintering

Abstract

Short carbon fiber reinforced SiC matrix composites were fabricated by spark plasma sintering. Density and mechanical properties of the composites increased continuously at increasing sintering temperature and constant pressure. Cracks in the composite matrix resulted from high thermal residual stresses generated during the cooling process from the sintering temperature due to the thermal expansion coefficient mismatch between fiber and matrix. The properties of the composites were lower than those of monolithic SiC ceramics obtained with the same processing technique as the composites. Fibers provided noncatastrophic fracture behavior of the composites as evidenced by the stress-displacement curves and fracture surface of the composites.

Introduction

Silicon carbide is one of the most promising structural materials for engineering application, because of its excellent high temperature mechanical properties, high thermal conductivity and good corrosion and wear resistance. However, silicon carbide applications have been limited because of its low fracture toughness. Fibers are introduced into the silicon carbide matrix to overcome the low fracture toughness and the high flaw sensitivity of monolithic silicon carbide ceramics.

Continuous fiber reinforced SiC composites obtained by chemical vapor infiltration (CVI) [1], [2], [3], polymer infiltration and pyrolysis (PIP) [4], [5], reaction sintering (RS) [6], [7], and hot-pressing (HP) [8], [9] have been extensively studied. Mechanics and fabrication of short fiber reinforced SiC composites have rarely been reported [10]. The use of short fiber as reinforcement is a way to reduced the cost of the composites.

Spark plasma sintering (SPS) is a relatively new sintering technique in powder metallurgy which is capable of sintering metal and ceramic powers quickly to full density at a fairly low temperature due to its unique features [11]. Nano-SiC ceramics have been fabricated by SPS [12], which would have better thermal shock than normal SiC ceramics. Fabrication of short carbon fiber reinforced SiC composites by SPS has been reported [13], [14] and the densification process of composites discussed. However, the mechanical properties of the C_f/SiC composites fabricated by SPS have not been reported.

In the present work, short C fiber reinforced SiC composites were fabricated by SPS. The effects of processing parameters on the densification process and on the mechanical properties of the composites using high modulus short C fibers as reinforcement were investigated.