Shock absorbing and impact mitigating structures based on axial-rotational coupling mechanism
An impact mitigating assembly includes an elongate member formed from a plurality of triangulated cylindrical origami (TCO) unit cells that exhibit coupled rotational and axial motion. The unit cells include an end portion and a tubular member fixed to the end portion. The tubular member has a plurality of concave sides. Each side has a first triangular portion and a second triangular portion sharing an elastic connecting edge with the second triangular portion. The first triangular portion also shares an angled upright edge with the second triangular portion of an adjacent side. Compressing the tubular member longitudinally causes the connecting edge and the angled upright edge to elastically deform, for example by stretching, and causes the second end of the tubular member to rotate with respect to the first end of the tubular member.
1. An impact mitigating assembly comprising:
a plurality of longitudinally connected unit cells comprising at least five unit cells;
each unit cell comprising:
an end member and a corresponding tubular member having a variable axial length, wherein a first end of the tubular member is fixed to the end member and a second end of the tubular member extends away from the end member, the tubular member comprising a plurality of sides each side comprising a first triangular portion and a second triangular portion, wherein for each side:
i) the first triangular portion shares a connecting edge with the second triangular portion, the connecting edge extending across the variable axial length of the tubular member, wherein the connecting edge is configured to have a first elastic spring constant;
ii) the first and second triangular portions are non-coplanar such that the side is concave;
iii) the first triangular portion shares an angled upright edge with the second triangular portion of an adjacent side, the angled upright edge extending across the variable axial length of the tubular member, wherein the angled upright edge is configured to have a second elastic spring constant that is different from the first elastic spring constant; and
wherein compressing the tubular member longitudinally causes the connecting edge and the angled upright edge to elastically deform and further causes the second end of the tubular member to rotate with respect to the first end of the tubular member.
2. The impact mitigating assembly of claim 1 , wherein the first triangular portions and the second triangular portions comprise triangular panels.
3. The impact mitigating assembly of claim 1 , wherein the first triangular portions each comprise a truss structure comprising three rods connected end-to-end to define the triangular portions.
4. The impact mitigating assembly of claim 1 , wherein the first and second triangular portions are obtuse, scalene triangular portions.
5. The impact mitigating assembly of claim 1 , wherein the plurality of sides comprise at least five sides.
6. The impact mitigating assembly of claim 1 , wherein the plurality of sides comprise six sides.
7. The impact mitigating assembly of claim 1 , wherein the plurality of unit cells are identical.
8. The impact mitigating assembly of claim 1 , wherein the plurality of unit cells comprise at least one unit cell that is configured such that compressing the tubular member longitudinally causes the second end of the tubular member to rotate with respect to the first end of the tubular member in a first direction, and at least one unit cell that is configured such that compressing the tubular member longitudinally causes the second end of the tubular member to rotate with respect to the first end of the tubular member in a second direction that is opposite to the first direction.
9. The impact mitigating assembly of claim 1 , wherein at least some of the end members of the unit cells have a transverse length that is greater than a transverse length of the corresponding tubular member.
10. A device for mitigating impact to a protected object, the device comprising:
a panel; and
a plurality of elongate members having a first end attached to the panel and a second end configured to engage the protected object,
wherein the elongate members comprise a plurality of at least five longitudinally connected unit cells;
each unit cell comprising:
an end member and a corresponding tubular member having an elastically variable axial length, wherein a first end of the tubular member is fixed to the end member and a second end of the tubular member extends away from the end member, the tubular member comprising a plurality of sides each side comprising a first triangular portion and a second triangular portion, wherein for each side:
i) the first triangular portion shares an elastic connecting edge with the second triangular portion, the connecting edge extending across the variable axial length of the tubular member, wherein the connecting edge is configured to have a first elastic spring constant;
ii) the first and second triangular portions are non-coplanar such that the side is concave;
iii) the first triangular portion shares an elastic angled upright edge with the second triangular portion of an adjacent side, the angled upright edge extending across the variable axial length of the tubular member, wherein the angled upright edge is configured to have a second elastic spring constant that is different from the first elastic spring constant; and
wherein compressing the tubular member longitudinally causes the connecting edge and the angled upright edge to elastically deform and further causes the second end of the tubular member to rotate with respect to the first end of the tubular member.
11. The device of claim 10 wherein the first triangular portions and the second triangular portions comprise triangular panels.
12. The device of claim 10 , wherein the first triangular portions each comprise a truss structure comprising three rods connected end-to-end to define the triangular portions.
13. The device of claim 10 , wherein the first and second triangular portions are obtuse, scalene triangular portions.
14. The device of claim 10 , wherein the plurality of sides comprise at least five sides.
15. The device of claim 10 , wherein the plurality of sides comprise six sides.
16. The device of claim 10 , wherein the plurality of unit cells are identical.
17. The device of claim 10 , wherein the plurality of unit cells comprise at least one unit cell that is configured such that compressing the tubular member longitudinally causes the second end of the tubular member to rotate with respect to the first end of the tubular member in a first direction, and at least one unit cell that is configured such that compressing the tubular member longitudinally causes the second end of the tubular member to rotate with respect to the first end of the tubular member in a second direction that is opposite to the first direction.
18. The device of claim 10 , wherein at least some of the end members have a transverse length that is greater than a transverse length of the corresponding tubular member.