Multi-directional load dissipation using multimaterial mechanical metamaterials
View Patent ↗A multimaterial mechanical metamaterial (MMM) system for multi-directional load dissipation includes a rigid structural framework made of a first material, including left, right, and middle structures. This framework houses elastic bars made of a second, more elastic material. Upon application of a compressive load, the geometry of the rigid framework causes horizontal bars to stretch, dissipating a first portion of the load in an orthogonal direction. As deformation increases, the framework engages the middle structure, causing a vertical bar to stretch and dissipate a second portion of the load in a direction opposite to the initial applied load. A method for using the MMM system for protection against compressive loads provides a sequential, two-stage mechanism for energy absorption and force redirection. The method includes placing the MMM system between a subject and a compressive load.
1 . A multimaterial mechanical metamaterial (MMM) system, comprising:
a top surface positioned at a top side of the MMM system;
a bottom surface positioned at a bottom side of the MMM system;
a left structure positioned at a left side of the MMM system and comprising four left lateral faces defining a left open-ended prism shape;
a right structure positioned at a right side of the MMM system and comprising four right lateral faces defining a right open-ended prism shape;
a middle structure positioned between the left structure and the right structure and comprising four middle lateral faces defining a middle open-ended prism shape;
a left bar extending between a left edge and a right edge of the left open-ended prism shape of the left structure;
a right bar extending between a left edge and a right edge of the right open-ended prism shape of the right structure; and
a middle bar extending between a top edge and a bottom edge of the middle open-ended prism shape of the middle structure,
wherein the top surface, the bottom surface, the left structure, the right structure and the middle structure comprise a first material, and the left bar, the right bar and the middle bar comprise a second material that is more elastic than the first material,
wherein upon a compressive load on the MMM system, the left bar and the right bar are configured to dissipate a first portion of the compressive load to an orthogonal direction of the compressive load, and the middle bar is configured to reverse a second portion of the compressive load in an opposite direction of the compressive load.
2 . The MMM system of claim 1 , wherein when no compression or stretching force is applied on the MMM system:
the top surface, the bottom surface, the left bar and the right bar are parallel to one another and perpendicular to the middle bar.
3 . The MMM system of claim 2 , wherein when no compression or stretching force is applied on the MMM system:
the left structure is in direct contact with the top surface and the bottom surface,
the right structure is in direct contact with the top surface and the bottom surface,
the middle structure is spaced apart from the top surface and the bottom surface, and
the middle structure is in direct contact with the left structure and the right structure.
4 . The MMM system of claim 3 , wherein when no compression or stretching force is applied on the MMM system, in a cross section perpendicular to both the middle bar and the top surface:
the left structure has a diamond shape,
the right structure has a diamond shape, and
the middle structure has a square shape.
5 . The MMM system of claim 4 , wherein when no compression or stretching force is applied on the MMM system, in the cross section:
a top edge of the left structure is in direct contact with a left end of the top surface,
a bottom edge of the left structure is in direct contact with a left end of the bottom surface,
a top edge of the right structure is in direct contact with a right end of the top surface,
a bottom edge of the right structure is in direct contact with a right end of the bottom surface,
a left edge of the middle structure is in direct contact with a right edge of the left structure, and
a right edge of the middle structure is in direct contact with a left edge of the right structure.
6 . The MMM system of claim 5 , wherein when no compression or stretching force is applied on the MMM system, in the cross section:
the top edge, the bottom edge, a left edge and the right edge of the left structure and the top edge, the bottom edge, the left edge and a right edge of the right structure comprise fillet ends that are curved.
7 . The MMM system of claim 4 , wherein when no compression or stretching force is applied on the MMM system, in the cross section:
a top edge of the middle bar is spaced apart from the top surface by a first distance, and
a bottom edge of the middle bar is spaced apart from the bottom surface by a second distance that is equal to the first distance.
8 . The MMM system of claim 1 , wherein:
the first material is polylactic acid (PLA).
9 . The MMM system of claim 8 , wherein:
the second material is thermoplastic polyurethane (TPU).
10 . The MMM system of claim 1 , wherein:
the top surface, the bottom surface, the left structure, the right structure and the middle structure together form one monolithic piece.
11 . The MMM system of claim 1 , wherein:
the top surface, the bottom surface, the left structure, the right structure and the middle structure consist of the first material.
12 . The MMM system of claim 1 , wherein:
the left bar, the right bar and the middle bar consist of the second material.
13 . The MMM system of claim 1 , wherein when a compression force is applied on the MMM system along a first direction perpendicular to the top surface,
the left structure compresses along the first direction and extends along a second direction that is perpendicular to the first direction and parallel to the top surface,
the right structure compresses along the first direction and extends along the second direction, and
the middle structure compresses along the second direction and extends along the first direction.
14 . The MMM system of claim 13 , wherein when the compression force is applied on the MMM system along the first direction,
the left bar and the right bar both extend along the second direction, and
the middle bar extends along the first direction.
15 . The MMM system of claim 14 , wherein when the compression force is applied on the MMM system along the first direction,
the left bar and the right bar both extend along the second direction to convert a first portion of the compression force along the first direction to an orthogonal force in the second direction, and
the middle bar extends along the first direction to reverse a second portion of the compression force in an opposite direction relative to the first direction.
16 . The MMM system of claim 1 , wherein:
the top surface, the bottom surface, the left structure, the right structure and the middle structure are equally thick and have a first thickness.
17 . The MMM system of claim 16 , wherein:
the left bar, the right bar and the middle bar are equally thick and have a second thickness.
18 . The MMM system of claim 17 , wherein:
the first thickness is larger than the second thickness.
19 . A method of multi-directional load dissipation, comprising:
placing the MMM system of claim 1 between a subject and the compressive load.
20 . The method of claim 19 , further comprising:
orienting the MMM system so that the compressive load is perpendicular to the top surface of the MMM system.