Energy absorbing systems
The present disclosure relates to flexible energy absorbing systems and body armor, helmets and protective garments incorporating flexible energy absorbing systems. A flexible energy absorbing system may comprise a first plurality of cells having a first re-entrant geometry and a second plurality of cells having a second, different geometry. The first plurality of cells and the second plurality of cells may comprise an elastomeric material.
1. A flexible energy absorbing system, comprising:
a first plurality of cells comprising a first re-entrant geometry which extends directly from a top surface of the system to a bottom surface of the system; and
a second plurality of cells comprising a second geometry, different from the first re-entrant geometry which extends directly from the top surface of the system to the bottom surface of the system,
wherein the first plurality of cells and the second plurality of cells comprise an elastomeric material,
wherein one or both of the first re-entrant geometry and the second geometry comprise an internal cell wall re-entrant geometry which extends directly from the top surface of the system to the bottom surface of the system,
wherein cells in the first plurality are orientated along a first axis and cells in the second plurality are orientated along a second, different axis, and
wherein one or both of the first axis and the second axis are not normal to the top surface of the system and the bottom surface of the system.
2. The system according to claim 1 , wherein one or both of the first axis or the second axis are aligned with a direction in which an injection molding tool used to manufacture the system opens.
3. The system according to claim 1 , wherein at least one cell of the first plurality of cells comprises an anisotropic geometry along a different axis than the first axis.
4. The system according to claim 1 , wherein at least one cell of the second plurality of cells comprises an anisotropic geometry along a different axis than the second axis.
5. The system according to claim 1 , wherein cells of the first plurality of cells are located in a first area of the system and cells of the second plurality of cells are located in a second area of the system, different from the first area of the system.
6. The system according to claim 5 , wherein cells in the first area are packed at a different density than cells in the second area.
7. The system according to claim 5 , wherein cells in the first area are packed at a higher density than cells in the second area.
8. The system according to claim 5 , wherein the first area comprises a core area and the second area comprises an edge area surrounding the core area.
9. The system according to claim 5 , wherein the system comprises one or more edges, and cells in the second area are located closer to the one or more edges of the system than cells in the first area.
10. The system according to claim 5 , wherein a geometry of the first plurality of cells and a geometry of the second plurality of cells gradually changes from the first re-entrant geometry in the first area to the second geometry in the second area.
11. The system according to claim 5 , wherein a packing density of the first plurality of cells and a packing density of the second plurality of cells gradually changes from a relatively higher packing density in the first area to a relatively lower packing density in the second area.
12. The system according to claim 5 , wherein the system comprises body armor.
13. The system of claim 12 , wherein the first area is associated with a first body area to be protected and the second area is associated with a second body area to be protected, different from the first body area to be protected.
14. The system according to claim 13 , wherein the first body area is a relatively more vulnerable anatomical body area than the second body area.
15. The system according to claim 13 , wherein:
the body armor comprises a knee protector, and
the first body area comprises one or more of:
a patella,
a bony protrusions at an end of a tibia, and
a bony protrusions at an end of a femur.
16. The system according to claim 13 , wherein:
the body armor comprises a back protector,
the first body area comprises a core spine area, and
the second body area comprises an area further away from a spine than the core spine area.
17. The system according to claim 1 , wherein the second geometry comprises a second re-entrant geometry, different from the first re-entrant geometry.
18. The system according to claim 1 , wherein cells of the second plurality of cells comprise straight walls.
19. The system according to claim 1 , wherein the elastomeric material comprises a strain rate sensitive material.
20. The system according to claim 1 , wherein the system comprises a tensile layer attached to at least one of the first plurality of cells or the second plurality of cells.
21. The system according to claim 1 , wherein the system comprises a protective garment.
22. The system according to claim 1 , wherein the elastomeric material comprises a thermoplastic elastomer.
23. A helmet, comprising:
a flexible energy absorbing system, comprising:
a first plurality of cells comprising a first re-entrant geometry which extends directly from a top surface of the system to a bottom surface of the system; and
a second plurality of cells comprising a second geometry, different from the first re-entrant geometry which extends directly from the top surface of the system to the bottom surface of the system,
wherein the first plurality of cells and the second plurality of cells comprise an elastomeric material,
wherein one or more of the first re-entrant geometry and the second geometry comprise an internal cell wall re-entrant geometry which extends directly from the top surface of the system to the bottom surface of the system,
wherein cells in the first plurality are orientated along a first axis and cells in the second plurality are orientated along a second, different axis, and
wherein one or more of the first axis and the second axis are not normal to the top surface of the system and the bottom surface of the system.
24. A method of manufacturing a flexible energy absorbing system, comprising:
forming a first plurality of cells comprising a first re-entrant geometry which extends directly from a top surface of the system to a bottom surface of the system; and
forming a second plurality of cells comprising a second geometry, different from the first re-entrant geometry which extends directly from the top surface of the system to the bottom surface of the system,
wherein the first plurality of cells and the second plurality of cells comprise an elastomeric material,
wherein one or both of the first re-entrant geometry and the second geometry comprise an internal cell wall re-entrant geometry which extends directly from the top surface of the system to the bottom surface of the system,
wherein cells in the first plurality are orientated along a first axis and cells in the second plurality are orientated along a second, different axis, and
wherein one or both of the first axis and the second axis are not normal to the top surface of the system and the bottom surface of the system.