A ballistic containment structure (64; 92; 140; 160) comprising: a first layer (66;94;142;162) including a plurality of flanges (72;102;168), a second layer (68;96;144;164) including a deformable membrane (74;104;170), wherein the second layer (68;96;144;164) is connected to the first layer (66;94;142;162) along a first major surface of the deformable membrane (74;104;170); and a third layer (70;98;146;166) connected to the second layer (68;96;144;164) along a second major surface of the deformable membrane (74;104;170) opposite the first major surface, wherein the third layer (70;98;146;166) comprises a first series of internal structures (76;106;172), wherein each of the first series of internal structures (76;106;172) includes structure elements that form a triangle with and are connected to the second major surface of the deformable membrane (74;104;170), wherein each of the first series of internal structures (76;106;172) includes an exterior surface (88;110) opposite the deformable membrane (74;104;170), characterised in that: each of the exterior surfaces (88;110) of each first series of internal structures (76;106; 172) includes an apex located at a midpoint of the exterior surface (88;110) and at a distance A D from a plane of intersection points of the first series of internal structures (76;106;172), wherein the intersection points include points of intersection between individual structure elements and the exterior surface (88;110), and further wherein the distance A D includes an absolute value of greater than zero, wherein each of the plurality of flanges (72;102;168) further comprises a first face (80;120) and a second face (82;122) on an opposite side of the flange (72;102;168) as the first face (80;120), further wherein each of the first face (80;120) and the second face (82;122) form either an acute angle or an obtuse angle with a plane of the deformable membrane (74;104;170) in an un-deformed state, wherein the first face (80;120) of each of the plurality of flanges (72;102;168) includes a first nesting feature (84;124) and the second face (82;122) of each of the plurality of flanges (72;102;168) includes a second nesting feature (86;126), and further wherein the first nesting feature (84;124) is configured to receive the second nesting feature (86;126). a first layer (66;94;142;162) including a plurality of flanges (72;102;168), a second layer (68;96;144;164) including a deformable membrane (74;104;170), wherein the second layer (68;96;144;164) is connected to the first layer (66;94;142;162) along a first major surface of the deformable membrane (74;104;170); and a third layer (70;98;146;166) connected to the second layer (68;96;144;164) along a second major surface of the deformable membrane (74;104;170) opposite the first major surface, wherein the third layer (70;98;146;166) comprises a first series of internal structures (76;106;172), wherein each of the first series of internal structures (76;106;172) includes structure elements that form a triangle with and are connected to the second major surface of the deformable membrane (74;104;170), wherein each of the first series of internal structures (76;106;172) includes an exterior surface (88;110) opposite the deformable membrane (74;104;170), characterised in that: each of the exterior surfaces (88;110) of each first series of internal structures (76;106; 172) includes an apex located at a midpoint of the exterior surface (88;110) and at a distance A D from a plane of intersection points of the first series of internal structures (76;106;172), wherein the intersection points include points of intersection between individual structure elements and the exterior surface (88;110), and further wherein the distance A D includes an absolute value of greater than zero, wherein each of the plurality of flanges (72;102;168) further comprises a first face (80;120) and a second face (82;122) on an opposite side of the flange (72;102;168) as the first face (80;120), further wherein each of the first face (80;120) and the second face (82;122) form either an acute angle or an obtuse angle with a plane of the deformable membrane (74;104;170) in an un-deformed state, wherein the first face (80;120) of each of the plurality of flanges (72;102;168) includes a first nesting feature (84;124) and the second face (82;122) of each of the plurality of flanges (72;102;168) includes a second nesting feature (86;126), and further wherein the first nesting feature (84;124) is configured to receive the second nesting feature (86;126).