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; and
a second plurality of cells comprising a second geometry, different from the first re-entrant geometry, wherein:
the first plurality of cells and the second plurality of cells comprise an elastomeric material,
cells in the first plurality of cells are located in a first area of the flexible energy absorbing system and cells in the second plurality of cells are located in a second area of the flexible energy absorbing system, different than the first area of the flexible energy absorbing system,
cells in the first area of the flexible energy absorbing system are packed at a higher density than cells in the second area of the flexible energy absorbing system, and
a third area is provided between the first area and the second area and comprises a packing density less than that of the first plurality of cells in the first area of the flexible energy absorbing system and greater than that of the second plurality of cells in the second area of the flexible energy absorbing system.
2. The flexible energy absorbing system of claim 1 , wherein one or more of the first re-entrant geometry and the second geometry comprise an internal cell wall re-entrant geometry.
3. The flexible energy absorbing system of claim 1 , wherein the first area of the flexible energy absorbing system comprises a core area and the second area of the flexible energy absorbing system comprises an edge area surrounding the core area.
4. The flexible energy absorbing system of claim 1 , wherein cells in the second area of the flexible energy absorbing system are located closer to one or more edges of the flexible energy absorbing system than cells in the first area of the flexible energy absorbing system.
5. The flexible energy absorbing system of claim 1 , further comprising a third area between the first area and the second area and comprising a third re-entrant geometry based on the first re-entrant geometry of the first plurality of cells in the first area and the second geometry of the second plurality of cells in the second area of the flexible energy absorbing system.
6. The flexible energy absorbing system of claim 1 , wherein the second geometry comprises a second, different re-entrant geometry.
7. The flexible energy absorbing system of claim 1 , wherein cells in the second plurality of cells comprise straight walls.
8. The flexible energy absorbing system of claim 1 , wherein:
the elastomeric material comprises a strain rate sensitive material, and/or the flexible energy absorbing system further comprises a tensile layer.
9. The flexible energy absorbing system of claim 1 , wherein a packing density transitions from the first area to the second area.
10. A body armor, comprising:
a flexible energy absorbing system, comprising:
a first plurality of cells comprising a first re-entrant geometry; and
a second plurality of cells comprising a second geometry different from the first re-entrant geometry, wherein:
the first plurality of cells and the second plurality of cells comprise an elastomeric material,
cells in the first plurality of cells are located in a first area of the flexible energy absorbing system and cells in the second plurality of cells are located in a second area of the flexible energy absorbing system, different from the first area of the flexible energy absorbing system,
cells in the first area of the flexible energy absorbing system are packed at a higher density than cells in the second area of the flexible energy absorbing system,
the first area of the flexible energy absorbing system is associated with a first body area to be protected and the second area of the flexible energy absorbing system is associated with a second different body area to be protected, different from the first body area, and
the first body area is more vulnerable to impact damage than the second body area.
11. The body armor of claim 10 , wherein the first area of the flexible energy absorbing system provides a first level of impact protection that is higher than a second level of impact protection provided by the second area of the flexible energy absorbing system.
12. The body armor of claim 10 , wherein:
the body armor comprises a knee protector, and
the first body area comprises one or more of:
a patella;
one or more bony protrusions at the ends of the tibia; and
one or more bony protrusions at the ends of the femur.
13. The body armor of claim 10 , wherein:
the body armor comprises a back protector,
the first body area comprises a core spine area,
the second body area comprises an area adjacent to, but not overlapping, the core spine area.
14. The body armor of claim 10 , wherein a packing density transitions from the first area to the second area.
15. A helmet, comprising:
a flexible energy absorbing system, comprising:
a first plurality of cells comprising a first re-entrant geometry; and
a second plurality of cells comprising a second geometry, different than the first re-entrant geometry, wherein:
the first plurality of cells and the second plurality of cells comprise an elastomeric material,
cells in the first plurality of cells are located in a first area of the flexible energy absorbing system and cells in the second plurality of cells are located in a second, different area of the flexible energy absorbing system,
cells in the first area are packed at a higher density to cells in the second area, and
a third area is provided between the first area and the second area and comprises a packing density less than that of the first plurality of cells in the first area and greater than that of the second plurality of cells in the second area.
16. A protective garment, comprising:
a flexible energy absorbing system, comprising:
a first plurality of cells comprising a first re-entrant geometry; and
a second plurality of cells comprising a second geometry, different than the first re-entrant geometry, wherein:
the first plurality of cells and the second plurality of cells comprise an elastomeric material,
cells in the first plurality of cells are located in a first area of the flexible energy absorbing system and cells in the second plurality of cells are located in a second, different area of the flexible energy absorbing system,
cells in the first area are packed at a higher density to cells in the second area, and
a third area is provided between the first area and the second area and comprises a packing density less than that of the first plurality of cells in the first area and greater than that of the second plurality of cells in the second area.
17. A method of manufacturing a flexible energy absorbing system comprising an elastomeric material, the method comprising:
forming a first plurality of cells comprising a first re-entrant geometry; and
forming a second plurality of cells comprising a second geometry, different than the first re-entrant geometry, wherein:
the first plurality of cells and the second plurality of cells comprise an elastomeric material,
cells in the first plurality of cells are located in a first area of the flexible energy absorbing system and cells in the second plurality of cells are located in a second, different area of the flexible energy absorbing system,
cells in the first area are packed at a higher density to cells in the second area, and
forming one or more of the first plurality of cells and the second plurality of cells comprises performing an injection molding process.
18. The method of claim 17 , the method comprising:
forming a tensile layer; and
performing one of:
directly molding the first plurality of cells and the second plurality of cells onto the tensile layer; or
attaching the first plurality of cells and the second plurality of cells to the tensile layer using an adhesive.