Mesophase Pitch-based Carbon Fiber and Its Composites: Preparation and Characterization

The objective of this study is to investigate the relationship among process, structure, and property of the UTSI pitch-based carbon fibers and optimize carbon fiber’s mechanical properties through the stabilization process. Various analysis techniques were employed throughout these investigations which include the Scanning Electron Microscope (SEM), optical microscope, Dia-stron system, MTS, and ImageJ.

Several fiber process techniques including fiber spinning, stabilization, and carbonization were explored to determine the effect of the thermal process on the fiber yield, fiber diameter, the sheath-core structure of stabilized fibers, the pac-man and hollow core structures of carbonized fibers, and the resulting mechanical properties of the carbon fibers. It was found that stabilization time and the temperature stepping had a great deal on influence on the resulting carbon fibers. Larger diameter fiber is easy to form sheath-core structure in the stabilization process. Pac-man structure was developed at 600°C during the carbonization. Both stabilization duration and the carbonization temperature control the resulting carbon fiber diameter and fiber structure defects such as the pac-man and hollow core defects. Multi-step stabilization can reduce the total stabilization duration and improve the mechanical properties of the resulting carbon fibers.

Fiber structure non-uniformities including fiber diameter distributions for a bundle fiber or along a single fiber, and pac-man angles were determined. Statistical analysis revealed the distribution of the carbon fiber cross-sectional areas and the result is compared against commercial available carbon fibers.

Carbon fiber sandwiched composites (CFSCs) were fabricated with UTSI carbon fiber and commercial PAN-based carbon fibers. Several configurations of sandwich structured composites were explored to test the flexural properties with varying sandwich thickness.