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

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 L ¯ a of fiber surface sheets. The empirical formula of the interfacial modulus and strength with the change of L ¯ a 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 L ¯ a 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 L ¯ a has no obvious influence on the interfacial normal tensile mechanical properties.

Molecular dynamics simulation on PyC interfacial failure mechanism and shear strength of SiC/SiC composites

“…Zhan et al [27] simulated the tensile behavior of SiC/graphene composites through LAMMPS software and found that when the graphene sheet was in contact with Siterminated SiC (1 1 1) surface, stronger interfacial interaction inhibited the tensile deformation of graphene sheet, resulting in higher tensile strength and failure strain of composites. Zhou et al [28] studied the mechanical properties of the C f /PyC interphase under a tangential shear and normal tensile load. However, the proposed model established in that paper only considered the contact position between the C-fiber and PyC interphase.…”

Molecular Dynamics Analysis of Silica/PMMA Interface Shear Behavior

“…The tensile deformation of bitumen-aggregate and polymer-mineral interfaces 55 was recently investigated through molecular simulations [15][16][17][18]. MD was also used to 56 understand the mode II behavior of interfaces between metallic atoms [19,20], polyethy-57 lene and silica [21] and carbon composites [22]. A MD model of glass with crystalline 58 nanoprecipitates revealed that glass-glass interfaces act as structural heterogeneities, 59 which promote shear band formation and prevent strain localization [23].…”