Daoyang Han

Measurement of In-Plane Shear Strength of Carbon/Carbon Composites by Compression of Double-Notched Specimens

The compression of a double-notched specimen was used to determine the in-plane shear strength (IPSS) of a carbon/carbon composite in the paper. The effects of the notch distance (L), thickness (T), and notch width (W) and supporting jig on the IPSS of the double-notched specimens were investigated numerically and experimentally. The fracture surfaces were examined by a scanning electron microscope. It was found that the IPSS varied with L. Thin specimen yielded low strength. W has little effect on IPSS. The main failure modes include the matrix shear cracking, delamination, fracture and pullout of fibers or fiber bundles. Meanwhile, a supporting jig can provide lateral support and prevent buckling, therefore lead to the failure in a shear mode.

Impact behavior of different cross-ply laminated carbon fiber-reinforced silicon carbide composites under the low velocity

Carbon fiber-reinforced silicon carbide composites (C/SiC) were fabricated by a chemical vapor infiltration process using various ply orientations of 2D carbon fabric in the preform. The effect of ply angles (0°/90°, 45°/−45°, and 0°/45°/90°/−45°) on the low-velocity impact damage of the C/SiC composites was investigated externally and internally. Different depths of pits were formed in the impacted side with fibers sheared off, whereas fiber bundles breakage and matrix cracking appeared on the back side. The sample with 0°/90° ply angles experienced a serious fiber fracture and stratification damage, while the other two samples only showed a slight stratification. The samples with 0°/45°/90°/−45° and 0°/90° ply angles had nearly the same strength loss rate, which was smaller than that of the sample with 45°/−45° ply angle. In 45°/−45°, the ply angle had a major influence on the residual strength as the fibers were at 45° to the loading direction. Comparison of compression strength of the samples before and after impact test showed that the quasi-isotropic laminate improved the impact damage resistance due to the prevention of the devastating crack extension.

Effect of electrophoretic deposition of carbon nanotubes on the tensile behaviors of carbon fiber tow

The effect of carbon nanotubes introduced by electrophoretic deposition on the tensile behavior of carbon fiber tow was investigated. As-received and heat-treated carbon fiber tows that deposited with carbon nanotubes and their counterparts were tested under monotonous tensile loading. Morphology and presence state of carbon nanotubes on the surface of carbon fiber tows were observed for determining the role of carbon nanotubes. Results showed that tensile properties of carbon fiber tow were not damaged by the electrophoretic deposition process. Due to the uniformly distributed carbon nanotubes network on the surface of carbon fiber tow, the fracture of filaments were obviously constrained by carbon nanotubes instead of instantaneous separation. What’s more, carbon nanotubes exhibited a stronger confining ability for heat-treated carbon fiber tow and improved their tensile properties significantly.