Residual stress and interface debonding behavior in Si₃N_4w reinforced SiCN composites prepared by the PIP process: A case study

Polymer infiltration and pyrolysis (PIP), as a preparation route for ceramic matrix composites, employs the polymer-to-ceramic transformation inside the preforms to gradually buildup the matrix. The effects of the structural transformation on the residual stress and on the interface debonding behavior of PIP derived Si₃N₄ whisker reinforced SiCN (Si₃N_4w/SiCN) composites are analyzed. Accordingly, the Si₃N_4w whisker in the composites are under residual compressive stress after the formation of the polymer-derived ceramic matrix. An increase in the pyrolysis heating rate from 1 to 10 ℃/min effectively lowers the residual stress from 195.8 to 91.3 MPa. Interface fracture energies of Si₃N_4w/SiCN derived from the debonding behavior significantly rise from <11.91 to 21.82 J/m² with the annealing temperature from 900 to 1400 ℃. The residual stress and interfacial behavior are related to the in-situ densification/shrinkage and structural rearrangement during pyrolysis and annealing.