Compressive strength of carbon fibers

Direct transverse compressive test of pitch-based carbon fibers was carried out on the single filament. The carbon fibers had randomly or radially orientation textures of graphite crystallite in the cross section. Both the transverse modulus and transverse compressive strength decreased with crystallite size increasing. There is little influence of orientation texture in cross section on the transverse modulus and transverse compressive strength. Fracture behavior was also observed under a scanning electron microscope from two directions. The fracture part was limited near the contact area of the punch for randomly oriented fibers, but the fracture of radially oriented fibers tend to be extended along the fiber axis. Fragment of fractured fiber with small crystallite was smaller. The fracture path in the cross section was run through the center of cross section and the edge of contact area with punch.