Structural Evolution and Mechanical Modulation of C_f/SiC Interfaces During PIP Ceramization: A ReaxFF Molecular...

Area of Science:

• Materials Science
• Computational Materials Science
• Ceramic Matrix Composites

Background:

• The precursor infiltration and pyrolysis (PIP) route is standard for C_f/SiC composite fabrication.
• The atomic-scale interface evolution during ceramization and its mechanical impact are not well understood.

Purpose of the Study:

• To investigate the thermochemical-mechanical behavior of polycarbosilane (PCS) precursors on pyrolytic carbon (PyC) substrates with varying orientation angles (OAs).
• To elucidate the role of interfacial structure on the mechanical integrity and failure mechanisms of C_f/SiC composites.

Main Methods:

• Reactive molecular dynamics (ReaxFF MD) simulations were employed to model PCS pyrolysis on PyC substrates (OAs 0°, 25°, 55°, 85°).
• Simulations analyzed interfacial atomic restructuring, hybridization changes (sp² to sp³), and response to shear loading.

Main Results:

• High OAs (55°, 85°) promoted extensive cross-interfacial covalent bonding due to reactive edge sites.
• Interfacial bonding shifted failure modes from interlayer sliding to ductile fracture with crack deflection.
• The OA = 55° interface achieved 15 GPa shear strength, balancing strength and ductility.
• The OA = 85° interface showed brittle failure via crack penetration.

Conclusions:

• Interfacial texturing via substrate OA significantly influences C_f/SiC composite mechanical properties.
• Optimized pyrolysis protocols and interfacial design can engineer enhanced strength and ductility.
• This study provides a framework for bottom-up design of advanced C_f/SiC composites.