Design Optimization of Variable-Stiffness Composite Structures Considering Blending Constraint

This study develops an innovative optimization framework for designing hybrid variable-stiffness composite structures featuring spatially varying fiber orientations with inter-regional blending constraints, which enables significant weight reduction in aerospace applications. The methodology addresses the complex design challenge involving mixed discrete variables (the numbers of plies and layer thicknesses) and continuous variables (fiber orientation angles), while ensuring manufacturing feasibility through strictly enforced fiber path continuity requirements. To realize simultaneous optimization of such mixed design variables, a ground laminate concept with redundant plies guides the optimization process and establishes the initial design space. A multi-fidelity surrogate modeling technique incorporating exponent-based adaptive correction enhances computational efficiency, and a hybrid optimization strategy combines genetic algorithms for global exploration with sequential quadratic programming for local refinement. A novel layer-sharing and mutation scheme, integrated between optimization phases, guarantees blending constraint compliance throughout the design process. Two representative numerical examples, i.e., a two-patch plate and a T-shaped composite structure, demonstrate the framework’s effectiveness in optimizing the composite layup while satisfying all manufacturing constraints. The developed methodology provides a systematic and practical solution for designing hybrid variable-stiffness composite structures, showing superior performance compared to conventional approaches.