The progressive ply interpolation model for the optimization design of double-double laminates with gradual thickness tapering

Double–double laminates can offer a lightweight design that is easy to taper by varying the number of repeated sub-plies. In this work, an innovative gradual thickness tapering optimization design method for DD laminates has been proposed, enabling the ply-drop design of DD laminates. Specifically, the progressive ply interpolation model has been put forward, simultaneously taking into account the current element thickness and the element thickness within the local search area. This method can effectively prevent the occurrence of empty sub-plies and the simultaneous change of multiple sub-plies in the DD laminate structure, and can also control the taper size. Finally, through three examples, including the aircraft wing in an engineering project, the influencing factors of the optimization results are discussed. It is demonstrated that this method has great potential in enabling the DD laminate structure to achieve a higher stiffness-to-mass ratio.