To expand on that, the prototype structure seems made to replicate the properties of vibranium with other materials.

The black framework is to prevent the disc shape from distorting on impact, and has struts leading to the center to redistribute kinetic energy into the entire frame.

The small "winglets" on the lower left look to be spring-loaded, again to allow shock absorption and give it the distinctive "pinball" quality of hitting multiple targets in a single throw. That they are also angled in one direction leads me to think they would help maintain momentum after throwing the shield, so that it doesn't start wobbling after an impact.

The honeycomb lattice in the center, and the smaller one on inside wall, are there to provide direct frontal impact resistance, while keeping the overall structure lighter than if it were a solid slab.