Energy absorbing systems
Disclosed herein are flexible energy absorbing systems and methods of manufacturing flexible energy absorbing systems. The systems include one or more cells of a strain rate sensitive material and having a re-entrant geometry. Some of the systems have an anisotropic geometry to provide a different response to impacts from different directions.
1. A flexible energy absorbing system comprising:
a plurality of cells formed from a strain rate sensitive material and connected to a base element, wherein:
each respective cell of a first subset of the plurality of cells comprises a cell wall continuously tapering in a single direction from a first cell wall width at a first end of the cell wall attached to the base element to a second cell wall width at a second end of the cell wall opposite the base element, the cell wall having a continuous concave curvature,
each respective cell of the first subset of the plurality of cells comprises a hole at a top of the respective cell opposite the base element,
the plurality of cells comprise a re-entrant geometry along a re-entrant geometry axis,
each respective cell of the first subset of the plurality of cells comprises an anisotropic geometry comprising a major axis and a minor axis, the major axis and the minor axis being perpendicular to the re-entrant geometry axis, and
the hole at the top of each cell of the first subset of the plurality of cells comprises an anisotropic geometry comprising the major axis and the minor axis.
2. The flexible energy absorbing system of claim 1 , wherein:
each cell in the plurality of cells comprises at least one wall,
the at least one wall has a re-entrant geometry in a direction normal to the base element, and
the re-entrant geometry in the direction normal to the base element comprises one or more of:
a tapering cylinder,
a tapering rectangular prism,
a tapering polygonal prism, or
a tapering anisotropic geometry.
3. The flexible energy absorbing system of claim 1 , wherein the plurality of cells comprises first cells comprising a first geometry and second cells comprising a second different geometry.
4. The flexible energy absorbing system of claim 1 , wherein:
the plurality of cells comprises a second subset of cells comprising a first geometry and a third subset of cells comprising a second geometry, different from the first geometry and
the third subset of cells comprising the second geometry have a different flexing response than the second subset of cells comprising the first geometry in order to facilitate configuration of the flexible energy absorbing system from a planar form to an aspherical form.
5. The flexible energy absorbing system of claim 1 , further comprising: a flexing mechanism for facilitating configuration of the flexible energy absorbing system from a planar form to an aspherical form.
6. The flexible energy absorbing system of claim 5 ,
wherein the flexing mechanism comprises one or more of:
an absence of cells,
an orientation of cells,
a slit, or
a textile portion.
7. The flexible energy absorbing system of claim 1 , further comprising:
a flexing mechanism for facilitating configuration of the flexible energy absorbing system from a planar form to an aspherical form,
wherein the flexing mechanism comprises one or more slits in the base element.
8. The flexible energy absorbing system of claim 1 , further comprising:
a flexing mechanism for facilitating configuration of the flexible energy absorbing system from a planar form to an aspherical form,
wherein the flexing mechanism comprises at least part of the base element.
9. The flexible energy absorbing system of claim 1 , wherein:
at least a first set of the plurality of cells are arranged according to a first curvature when the flexible energy absorbing system is configured in a planar form,
at least a second set of the plurality of cells are arranged according to a second curvature when the flexible energy absorbing system is configured in an aspherical form, and
the first curvature is at a different orientation to the second curvature.
10. The flexible energy absorbing system of claim 1 , further comprising:
at least two interconnected portions of cells,
wherein a first portion has a first shape and a second portion has a second, different shape.
11. A body armor, comprising:
a flexible energy absorbing system, comprising:
a plurality of cells formed from a strain rate sensitive material and connected to a base element, wherein:
each respective cell of a first subset of the plurality of cells comprises a cell wall continuously tapering in a single direction from a first cell wall width at a first end of the cell wall attached to the base element to a second cell wall width at a second end of the cell wall opposite the base element, the cell wall having a continuous concave curvature,
each respective cell of the first subset of the plurality of cells further comprises a hole at a top of the cell opposite the base element,
the plurality of cells comprise a re-entrant geometry along a re-entrant geometry axis,
each respective cell of the first subset of the plurality of cells comprises an anisotropic geometry comprising a major axis and a minor axis, the major axis and the minor axis being perpendicular to the re-entrant geometry axis, and
the hole at the top of each cell of the first subset of the plurality of cells comprises an anisotropic geometry comprising the major axis and the minor axis.
12. A helmet, comprising:
a flexible energy absorbing system, comprising:
a plurality of cells formed from a strain rate sensitive material and connected to a base element, wherein:
each respective cell of a first subset of the plurality of cells comprises a cell wall continuously tapering in a single direction from a first cell wall width at a first end of the cell wall attached to the base element to a second cell wall width at a second end of the cell wall opposite the base element, the cell wall having a continuous concave curvature,
each respective cell of the first subset of the plurality of cells further comprises a hole at a top of the cell opposite the base element,
the plurality of cells comprise a re-entrant geometry along a re-entrant geometry axis,
each respective cell of the first subset of the plurality of cells comprises an anisotropic geometry comprising a major axis and a minor axis, the major axis and the minor axis being perpendicular to the re-entrant geometry axis, and
the hole at the top of each cell of the first subset of the plurality of cells comprises an anisotropic geometry comprising the major axis and the minor axis.
13. A method of manufacturing a flexible energy absorbing system, comprising:
forming a plurality of cells from a strain rate sensitive material on a base element, wherein:
a first subset of the plurality of cells comprises a cell wall continuously tapering in a single direction from a first cell wall width at a first end attached to the base element to a second cell wall width at a second end of the cell wall opposite the base element, the cell wall having a continuous concave curvature,
each respective cell of the first subset of the plurality of cells comprises a hole at a top of the respective cell opposite the base element,
the plurality of cells comprise a re-entrant geometry along a re-entrant geometry axis,
each respective cell of the first subset of the plurality of cells comprises an anisotropic geometry comprising a major axis and a minor axis, the major axis and the minor axis being perpendicular to the re-entrant geometry axis, and
the hole at the top of each cell of the first subset of the plurality of cells comprises an anisotropic geometry comprising the major axis and the minor axis.