Functionally graded structures for impact absorption

A functionally graded structure for a protective device, comprising:

• a plurality of lattice structures with different compression response properties, a first geometry and compression response property of a first lattice structure of the plurality of lattice structures being different from a second geometry and compression response property of a second lattice structure having a second geometry of the plurality of lattice structures, the first lattice structure and the second lattice structure having a second thickness that is different from the first thickness, wherein the first lattice structure directly interconnects with the second lattice structure through a plurality of individual nodes and wherein the first lattice structure includes a plurality of first segments connected to the plurality of nodes and wherein the first segments define a first set of pores having a first quadrilateral shape and wherein the second lattice structure includes a plurality of second segments connected to the plurality of nodes and wherein the second segments define a second set of pores having a second quadrilateral shape and wherein the first segments extend from the nodes at an acute angle to that of the second segments whereby the first quadrilateral shape is oriented at the acute angle to the second quadrilateral shape,
• wherein the plurality of lattice structures are arranged in a stack and an order of lattice structures in the stack is from a least stiff lattice structure to a most stiff lattice structure,
• wherein the first lattice structure defines a hemispherical shape having a center region comprising the second lattice structure.