Parametric study of afp lay-up process parameters effect on the air permeability of thermoplastic composites and their suitability for out of autoclave post-processing by a new method

Structural thermoplastic composites manufacturing by automated fiber placement (AFP) needs a secondary process to ensure perfect bonding between plies and remove all interlaminar voids and pores. Regarding the drawbacks of the autoclave as a conventional post-processing method of composites and the growing demand for aerospace-grade thermoplastics, out of autoclave post-processing methods such as vacuum bag only (VBO) getting more and more attention. Since the VBO process depends on the evacuation of internal air from components and filling them with resin flow under high temperature, the inherent air permeability of composite structure is the key parameter in the VBO process efficiency and final part quality. This study aims to find a correlation between the permeability of CF/PEKK thermoplastic composite structure and AFP lay-up process parameters. The air permeability is measured for coupons from components by the pulse-pressure decay method. Among studied parameters, high compaction force and high lay-up velocity result in low air permeability.