Design and Evaluation of Load Path Tailored Composite Panels

Abstract

The aim of present study is to establish the optimization design approach for light weight composites aircraft structure. A composite panel with a large cut-out representing a part of lower wing panel is optimally designed with the curved fiber orientation based on principal load path. The optimum curved fiber orientation is directly defined by the principal stress direction derived from finite element analysis result. Only the fiber orientation in 0 degree layers are steered based on principal load path. Three different types of the optimum panel with different staggering strategies are precisely manufactured by Automated Fiber Placement (AFP) with tow-steering layup technique. The optimum panels are evaluated by testing under tensile load. The results show that the initial failure load of the optimum panels with curved fiber orientation is 6% higher than that of the conventional panel with straight fiber orientation with the same weight, and the panel stiffness of the optimum panel is 3% higher than that of the conventional panel. The maximum strain level around the cut-out of the optimum panel is 8% smaller than that of the conventional panel. These results indicate that the optimum panel is capable of sustaining larger load than the conventional panel, and imply the potential of structural weight reduction for load path tailored composite panel. Those improvements in the testing correspond well with the numerical prediction which is used for the panel design.