Analysis and development of a brazing method to weld carbon fiber-reinforced poly ether ketone ketone with amorphous PEKK

Abstract In this study, a brazing method for carbon fiber-reinforced poly ether ketone ketone (CF-PEKK) is developed that allows welding below the melting temperature of the single components. During the manufacturing of CF-PEKK laminates, a pseudo-amorphous PEKK film is consolidated to its surface which acts as interlayer polymer during subsequent joining (brazing). Five different brazing temperatures, determined from thermal analysis of the material, are characterized for their weld quality mechanically, analytically, and through ultrasonic testing. Microanalytically Scanning Electron Microscope (SEM) investigations focus on the morphology of the weld zone in order to evaluate the diffusion processes at the interfaces. Compared to Differential Scanning Calorimetry measurements, the SEM investigations offer a basic understanding of the welded process and its influence on the welding properties. A welding temperature of 60 °C below the processing temperature of CF-PEKK laminates (380 °C) is shown to yield a welding factor of 0.93. Furthermore, based on the SEM investigation, it is possible to derive more promising improvement measures for the brazing method. Graphical Abstract