Real-time observation of waviness formation during C/PEEK consolidation

Defects such as fiber waviness can occur during the production of thermoplastic composite parts. It is desirable to prevent or minimize fiber waviness as it causes a knockdown in the part's mechanical properties. However, the mechanisms governing the formation of fiber waviness are currently not fully understood. A setup for the real-time observation of waviness formation during flat laminate consolidation is presented in this paper. For C/PEEK unidirectional composites, it was observed that waviness forms during cooling between the maximum process temperature and the crystallization temperature. A higher processing temperature leads to waviness with a larger misalignment angle. No such trends were observed for the wavelength. Waviness does not form or increase in severity after crystallization. The driving force for waviness formation in flat laminate consolidation was determined to be tool shrinkage transferred to the laminate via tool-ply friction.