Design, optimization and manufacturing of a unitized carbon fiber/thermoplastic wingbox structure

Manufacture of high performance large composite aerostructures in an out-of-autoclave process using thermoplastic composites that is cost-effective is highly attractive and, at the same time, technologically challenging. Furthermore, the introduction of variable angle tow composites giving spatially variable stiffness properties provides new ways to design high performance composite structures, by redefining the tailoring concept and allowing overall structural performance to be improved. The focus of this paper is the design and the manufacture of a unitized wingbox demonstrator with variable angle tow skin panels and integrated stiffeners. The entire structure is constructed using thermoplastic composite material with an in-situ laser-assisted automated tape placement machine. The design and optimization processes involve load determination, sizing and lay-up optimization of both the stiffener and the variable stiffness skin panels of the wingbox. The design of a reusable modular mold for manufacturing of the wingbox is also described. The interactions between the overall design process and the constraints imposed by the automated manufacturing technology with thermoplastic composites are also highlighted.