Strength of a Hi-Nicalon (TM)/silicon-carbide-matrix composite fabricated by the multiple polymer infiltration-pyrolysis process

A woven-fabric Hi-Nicalon(TM)-fiber reinforced SiC-matrix composite has bee n fabricated by using a multiple polymer infiltration-pyrolysis (PIP) proce ss. The three-point bend strength, at room temperature, of the composite is examined as a function of total porosity of the composite. The porosity of the composite decreases as the number of PIP cycles (N) increases. Both th e proportional-limit load and the maximum load in the three-point bend test increase as N increases. A compressive fracture mode is observed for N < 1 0 (total porosity of >10%), and a tensile fracture mode is observed for N g reater than or equal to 10 (total porosity of less than or equal to 10%). F or the composite with N = 14, with a total porosity of 8 vol%, a proportion al-limit stress of 410 MPa and a maximum stress of 600 MPa are achieved.