Processing optimization and mechanical evaluation of hot pressed 2D Tyranno-SA/SiC composites

Non-coated and carbon-coated 2D woven Tyranno SA/SiC composites were fabricated by hot pressing (HP) via liquid phase sintering (LPS). Various preparation conditions were optimized using non-coated fiber fabrics and mechanical evaluation was further conducted for the composites using carbon coated fiber fabrics. Results have indicated that intra-bundle infiltration of the fiber preforms during polymer impregnation and pyrolysis (PIP) pretreatment would affect the density of the composites. Modification of the polymer (polycarbosilane-PCS) to filler (SiC with sintering additives) ratio could promote the densification process, especially the intra-bundle matrix formation. Using non-coated fiber preforms, at 1750degreesC, 15MPa, suitable polymer precursor and filler content [PCS/(PCS + SiC) = 50%] was beneficial for obtaining composites with higher density. Applying carbon coated fiber fabrics and adopting the optimized polymer to filler ratio for pretreatment, composites with non-catastrophic fracture behavior could be obtained. Meanwhile, carbon coating can well protect fiber from damaging. At 1780 degreesC under 20 MPa, higher density of 2.82 g/cm(3) could be reached. This composite exhibited a relatively strong fiber/matrix bonding and the improved mechanical properties such as ultimate strength, proportional limit stress and elastic modulus, either in bending or tensile tests. (C) 2002 Elsevier Science Ltd. All rights reserved.