Investigation on Cf/PyC Interfacial Properties of C/C Composites by the Molecular Dynamics Simulation Method.

Yuan Zhou,Zhenyu Yang,Tianyuan Ye,Shouwen Liu,Long Ma,Zixing Lu

doi:10.3390/ma12040679

Yuan Zhou, Zhenyu Yang + Show 4 more

Open Access

https://doi.org/10.3390/ma12040679

Copy DOI

Abstract

In this paper, a molecular dynamics (MD) simulation model of carbon-fiber/pyrolytic-carbon (Cf/PyC) interphase in carbon/carbon (C/C) composites manufactured by the chemical vapor phase infiltration (CVI) process was established based on microscopic observation results. By using the MD simulation method, the mechanical properties of the Cf/PyC interphase under tangential shear and a normal tensile load were studied, respectively. Meanwhile, the deformation and failure mechanisms of the interphase were investigated with different sizes of the average length of fiber surface sheets. The empirical formula of the interfacial modulus and strength with the change of was obtained as well. The shear properties of the isotropic pyrolysis carbon (IPyC) matrix were also presented by MD simulation. Finally, the mechanical properties obtained by the MD simulation were substituted into the cohesive force model, and a fiber ejection test of the C/C composite was simulated by the finite element analysis (FEA) method. The simulation results were in good agreement with the experimental ones. The MD simulation results show that the shear performance of the Cf/PyC interphase is relatively higher when is small due to the effects of non-in-plane shear, the barrier between crystals, and long sheet folding. On the other hand, the size of has no obvious influence on the interfacial normal tensile mechanical properties.

Highlights

Carbon/carbon (C/C) composites are one of the most important ceramic matrix composites, which are often used to manufacture thermal protection structures in the aerospace field [1].C/C composites are usually prepared by depositing a pyrolytic carbon (PyC) matrix on carbon fiber preforms using chemical vapor phase infiltration (CVI) or chemical vapor phase deposition (CVD) processes [2,3]
Using the molecular dynamics (MD) simulation model of the Cf /PyC interphase established in Section 2.2.1, the normal (z direction) tensile properties with different L a were calculated at room temperature (300 K)
The bottom boundary fixed by setting the velocity equal to 0. in the velocity tensile of the topproperties boundary atoms wasdifferent set to V in the direction and equal toat 0 in the other two

Summary

Introduction

Carbon/carbon (C/C) composites are one of the most important ceramic matrix composites, which are often used to manufacture thermal protection structures in the aerospace field [1].C/C composites are usually prepared by depositing a pyrolytic carbon (PyC) matrix on carbon fiber preforms using chemical vapor phase infiltration (CVI) or chemical vapor phase deposition (CVD) processes [2,3]. The performance of the interphase has a close relationship with the toughening mechanism of fiber-reinforced ceramic matrix composites (such as crack propagation delay or deflection, fiber bridging toughening, interface debonding, and fiber pull out), and has a great influence on the composite mechanical properties and the stress–strain behaviors [4,5,6]. The interfacial properties of ceramic matrix composites have been one of the focuses of scholars’ study. Elkhateeb et al [9] used the MD method to simulate the crack propagation along the interface of Ti6Al4V/TiC in titanium metal matrix composites under Mode-I and II loadings and at different temperatures, and obtained the traction-separation relationship, which was used to parameterize the cohesive zone model (CZM) for modeling the interphase in finite element analysis

Objectives

Methods

Results

Conclusion