Evaluation of Micromechanical Properties of Carbon/Carbon and Carbon/Carbon–Silicon Carbide Composites at Ultralow Load

Abstract

2D carbon fiber (C-fiber)-reinforced carbon/carbon (C/C) composites were prepared by vacuum infiltration with coal-tar pitch followed by carbonization and graphitization in inert atmosphere. Liquid silicon infiltration was done in controlled atmosphere at 16001C to convert the matrix carbon of the C/C composites into silicon carbide. The 2D C/C and carbon/ carbon-silicon carbide (C/C-SiC) composites had density of B1.65 and B2.32 g/cm 3 , respectively with corresponding flexural strength of B70 and B169 MPa, respectively. The local mechanical properties like hardness, Young's modulus, contact pressure, relative stiffness, relative spring back, and indentation energies of the two composites under different loading conditions were measured at an ultra low load of 10 mN using a nanoindentation instrument with a Berkovich indenter. The scatter in the data was treated in terms of the two-parameter Weibull statistical analysis. The maximum characteristic Young's modulus (B16 GPa) and hardness (1.20 GPa) was obtained for the C/C-SiC composites in parallel direction of fabric stacking. The elastic rebounce was also the maximum (0.77) for the C/C-SiC composites when loaded in parallel direction of fabric stacking. The extent of structural anisotropy was higher in the C/C-SiC composite than that of the C/C composite.

Impact Energy Absorption Analysis of Spark Plasma Sintered Al2O3 Reinforced Bulk Multiwalled Carbon Nanotube Compacts Using Nanoindentation

“…RSB was calculated as [( h max − h f )/ h max ]. Similarly, RS was calculated as ( S max / h max ), where S max was contact stiffness . Table shows the data on H , E , and RS values of the three specimens at various loads.…”

“…So, the elastic recovery was the second highest at about 83%. Hardness ( H ) and Young's modulus ( E ) of all samples were evaluated from the P–h data plots using the well‐established Oliver–Pharr (O–P) model . In addition, other related properties such as ratio of elastic ( W e ) and plastic ( W p ) parts of total energy ( W t ) consumed during indentation cycle as well as RSB and relative stiffness (RS) were also calculated from the experimentally obtained load‐depth plots .…”

Characterization of thermal sprayed Si on sintered SiC for space optical applications

“…The h c is expressed as penetration depth and can be calculated from the following expression [32-34]: where κ ≈ 0.75 for a Berkovich indenter [34], S is basically the slope ( dP / dh ), estimated from the first ∼1/3rd of the linear part of the unloading cycle of P – h plot as marked in Figure 4.…”

“…The h c is expressed as penetration depth and can be calculated from the following expression [32][33][34]:…”

“…where κ ≈ 0.75 for a Berkovich indenter [34], S is basically the slope (dP/dh), estimated from the first ∼1/3rd of the linear part of the unloading cycle of P-h plot as marked in Figure 4. The term, S is further expressed as [32][33][34]:…”