Topology optimization with graded infill accounting for loading uncertainty

The optimal design of composite structures made of a solid phase and a given fraction of graded infill is addressed, using homogenization-based topology optimization and accounting for uncertainty in loading amplitude. A two-phase material law with void is implemented to control the amount of graded infill to be distributed, along with its admissible density range. Numerical homogenization is used to derive the macroscopic elastic properties of an isotropic and two orthotropic infills that are commonly used in additive manufacturing. A minimum weight problem is endowed with a set of deterministic displacement constraints that are equivalent to stochastic displacement enforcements in case of normal distributions of the amplitude of the applied forces. Sequential convex programming is adopted to solve the arising multi-constrained problem. Numerical simulations are performed to assess the proposed algorithm and point out peculiar features of the achieved optimal solutions with respect to layouts found in case of deterministic loads. When a fraction of graded infill is prescribed, coated structures are retrieved, whose shape may be remarkably affected by the selected type of lattice.