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 1750°C, 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 C under 20 MPa, higher density of 2.82 g/cm³ 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.