Effect of pyrocarbon interphase texture and thickness on tensile damage and fracture in T‐700™ carbon fiber–reinforced silicon carbide minicomposites

Abstract

In this paper, T-700™ carbon fiber-reinforced silicon carbide (C/SiC) minicomposites with pyrocarbon (PyC) interphase with different textural microstructure and thickness were fabricated using the chemical vapor infiltration method. The interface properties (i.e., textural microstructure, thickness, hardness, and modulus) were obtained through multiple testing methods (i.e., Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and nanoindentation tests). Relationships between the deposition temperature and residence time with the texture type (i.e., low, medium, and high texture) were established. Uniaxial tensile experiments were conducted for C/SiC minicomposites with different PyC interphases to characterize the composite's internal damage evolution and fracture. Relationships between the composite's tensile nonlinear damage evolution, fracture strength and strain, PyC interphase texture, and thickness were established. The composite's tensile strength and fracture strain were the highest for the C/SiC minicomposite with medium-high texture PyC interphase.For the C/SiC minicomposite with the same texture interphase, the composite's tensile strength and fracture strain were affected by the coating thickness. The higher the thickness of the coating, the lower the composite's tensile strength and fracture strain.

Effects of pyrocarbon interphase on microstructure and properties of C/SiBCN composites

“…The thicknesses of the PyC coating on the fibers after deposition times of 5 h, 15 h, and 30 h were ∼100 nm, ∼250 nm, and ∼500 nm, respectively (figure 1). The PyC interphases had rough surfaces that were strongly bonded with carbon fiber, which is conducive to improving the interface bonding strength between fiber and matrix [13,14]. After deposition for 5 h, carbon fibers were covered with a rough PyC coating with a thickness of 100 nm (figures 1(a), (b)); this rough surface is advantageous for increasing the frictional sliding resistance of pullout fibers in C/SiBCN composites [13].…”

“…Investigations of improvements in the properties of C/SiBCN composites after high-temperature treatment should focus on the interphase between carbon fibers and the matrix, because this interphase has a greatly influence on the properties of the composites [10]. Carbon fibers are typically coated with C [13,14], SiC [8,15], BN [16,17], etc as the interphase. The most common coating for optimizing the interphase are pyrocarbon (PyC).…”

Influence of Texture and Thickness of Pyrocarbon Coatings as Interphase on the Mechanical Behavior of Specific 2.5D SiC/SiC Composites Reinforced with Hi-Nicalon S Fibers

“…Detailed thermal-induced residual stresses calculation in each phase (i.e., fiber, interphase and matrix) is detailed elsewhere [35]. Even if the model is based on a single fiber and concentric cylinders of interphase and matrix, good correlations for minicomposites [19] and 2D tubular composites [25,36] have already been reported. The thermomechanical properties as a function of temperature were fitted with Equation (1) and the constants used for the calculations are presented in Table 3.…”

“…This textural organization is commonly used for PyC classification [15,16]. The influence of the nature of a PyC interphase (thickness and/or texture) on the mechanical behaviors of C/SiC was already studied [17][18][19], but these studies were only dedicated to carbon fiber reinforcement. Although the influence of pyrocarbon interphase thickness is well known in SiC/SiC composites [20][21][22][23][24][25], its textural organization influence has only been studied recently on unidirectional model composites (minicomposites) [26].…”

Fabrication process and growth mechanism of novel micro‐stack PyC interphase with different textures

“…In order to explore the advantage of the micro‐stack PyC interphase, The mini‐C f /PyC/SiC composites containing the micro‐stack PyC interphase were prepared, and the fabrication process referred to the previous works 21 …”