Stiffness Equivalent Substitution of an Airfoil Profile by an Automated Manufacturable CF/LM-PAEK Tailored Laminate Architecture

Continuous fiber-reinforced thermoplastic composites, processable with high-rate automated manufacturing technologies, are gaining momentum in the aviation industry. In contrast to conservatively designed multilayer ply stacks of uniform thickness processed by stamp forming or hybrid molding, tailoring of laminates opens the door to weight/performance optimized and geometrically advanced components. However, automated layup methods have certain limitations that reduce the degree of freedom in laminate design. Therefore, this study addresses laminate design strategies (BLOCK, CARD, CONV) with the goal of stiffness equivalent substitution of an AL7075-T6 aluminum airfoil profile by a pick-and-place compliant architecture based on a CF/LM-PAEK unidirectional (UD) tape material and defined guidelines. In addition, stacked pure matrix films were incorporated as core layers in certain laminates (THICK, THIN) to capture the edge-filling behavior driven by squeeze flow during processing and its influence on mechanical performance and laminate quality. The tailored ply stacks were consolidated into a composite component using a two-stage consolidation unit with a specially designed tool insert and experimentally evaluated by means of a four-point bending test and digital microscopy. From a design point of view, this study has shown that by smart utilization of symmetry, fiber orientations, and ply dimensions, a realization of the airfoil profile shape within the limitations of the pick-and-place tape laying unit can be realized by a tailored architecture. Despite the challenging stiffness requirements, one architecture is presented that meets the defined requirements. With respect to the incorporation of neat matrix film core layers, it has been found that this approach does not significantly improve the edge filling behavior, results in a discontinuous distribution within the laminate, is prone to voids, and reduces mechanical performance.