Systems and methods are provided for designing flat composites that are formed into 3D shapes. One embodiment is a method that includes loading data defining a three dimensional (3D) shape for a composite part, identifying constraints based on dimensions of the 3D shape, simulating flattening of the 3D shape into a planar shape, and acquiring a mandrel having the planar shape. The method also includes placing features at the mandrel which permit a laminate laid-up onto the mandrel to compensate for the constraints during forming of the laminate into the 3D shape, and generating a Numerical Control (NC) program that directs an Automated Fiber Placement (AFP) machine laying up the laminate. The NC program includes instructions for laying up tows of constituent material onto the mandrel having the features, to form layers of the laminate.