Properties of Multilayered Interphases in SiC/SiC Chemical‐Vapor‐Infiltrated Composites with “Weak” and “Strong” Interfaces

Abstract

The interfacial properties of SiC/SiC composites with interphases that consist of (C-SiC) sequences deposited on the fibers have been determined by single-fiber push-out tests. The matrix has been reinforced with either asreceived or treated Nicalon fibers. The measured interfacial properties are correlated with the fiber-coating bond strength and the number of interlayers. For the composites reinforced with as-received (weakly bonded) fibers, interfacial characteristics are extracted from the nonlinear portion of the stress-displacement curve by fitting Hsueh's push-out model. The interfacial characteristics are controlled by the carbon layer adjacent to the fiber. The resistance to interface crack growth and fiber sliding increases as the number of (C-SiC) sequences increases. For the composites reinforced with treated (strongly bonded) fibers, the push-out curves exhibit an uncommon upward curvature, which reflects different modes of interphase cracking and a contribution of fiber roughness.

Influence of pyrolytic carbon interface thickness on microstructure and mechanical properties of SiC/SiC composites by NITE process

“…The interfaces arrest, deflect and branch the propagating cracks that have initiated at outer or pore surfaces of the matrix. The propagating of cracks deflected along the interface enables energy dissipation through friction, and consequently allows a pseudo-ductile macroscopic fracture behavior in ceramic composites [17][18][19]. pyrolytic carbon (PyC) has conventionally been employed as interfaces in SiC/SiC composites.…”

A new approach to the subcritical cracking of ceramic fibers

“…Their structural performance is controlled mainly by the fibers [15]. Indeed, the fibers within the composite are protected from the surrounding cracks thanks to the mechanical fuse concept [1,20]. However, once the surrounding matrix has cracked, the fibers are no longer protected from the aggressive environment: air (actually, oxygen, water, etc.)…”

Mechanical properties and microstructures of Cf/SiC–ZrC composites using T700SC carbon fibers as reinforcements

“…Meanwhile, the oxide scale formed in the ablation process can effectively reduce the diffusion rate of oxidizing atmosphere toward the composite. For continuous fiber reinforced ceramic matrix composites (CFCMCs), fiber/matrix interfaces are critical on determining the performance of the materials [6], as the properties of fiber/ matrix interfaces determine the mechanical behavior of brittlematrix composites [7,8]. It has been postulated that the best interphase materials might be those with a layered crystal structure (PyC, h-BN) or a layered microstructure, such as (PyC-SiC) n and (BN-SiC) n , the layers being deposited parallel to the fiber surface weakly bonded to one another but strongly adherent to the fiber surface [9,10].…”