Raman spectroscopy was used to investigate the compressive fragmentation process and the interface behavior in ultra high modulus (UHM) (750 GPa Modulus) pitch-based graphite/polypropylene composites upon cooling from processing temperature to room temperature. It is found that bulging is the primary mechanism of failure in these fibers, and Raman peak position measurements show that not all visually detected features represent real fiber failure. However, at real break locations, the fiber strain is found to drop to zero.