The effects of the anisotropic core in a sandwich jamming structure. a) Sandwich jamming structure with an anisotropic core and two face sheets. The properties of the structure were analyzed through a three-point bending test. b) Stress contour plots indicate that the stress level in the face sheets is much larger than that in the core structure. c) A comparison of the analytical model, FEA, and experimental results. d) Stiffness and yield force increased with respect to the core thickness. e Bending stiffness did not change significantly with respect to the cellular width of the core structure.
The effects of rubber-laminated face sheets. a) Sandwich jamming structure with rubber-laminated face sheets. b) A comparison between model, FEA, and experimental results in three-point bending tests. c) Strain contour plots indicate the soft rubber layer deforms with respect to the shape of the cellular core. This deformation of rubber can increase friction between the core and face sheets with a wedge effect. The change of rubber deformation can also increase friction with a hysteretic effect. d) Three-point bending test results with respect to the level of vacuum pressure. Natural rubber was laminated on the face sheets. e) Different performances for rubber materials with different Young’s moduli. f) Jamming structure has viscoelastic bending strength with the lamination of nitrile butadiene rubber.
Anisotropic cores and face sheets with various degrees of freedom. a) Core with elongated rectangular cells. b) Core combined with elongated rectangular cells and triangular cells. c) Core with elongated rectangular cells with a thin layer in the neutral plane. d) Core with independent tubular column cells with a thin layer in the neutral plane. The Gaussian curvature is zero under the loading condition where the two ends are clamped and a single bending moment is applied about an in-plane axis. e) Core with hexagonal honeycomb cells. The Gaussian curvature is negative when deforms. f) Core composed of auxetic cells with rounded edges. The gaussian curvature is positive when deforms. g) Core with pyramidal truss structures. Each pyramidal truss has extended rectangular plates on the top and bottom surfaces. h) Single-layered face sheet. i) Double-layered face sheet. j) Face sheet woven with long thin films.
An arm support using the sandwich jamming structure. a) Core and face sheet designs of the arm support. b) Arm support allowing abduction-adduction and horizontal abduction-adduction motions. c) While the structure has a thin form factor, it provides sufficient stiffness and resisting force to support the arm weight. d) We conducted a precision manipulation task using a grooved peg board while requiring the wearer to maintain the arm-lifting posture with the proposed arm support. e) Reduced normalized integrated EMG values indicate that the device significantly reduced the overall muscle activity. f) Arm support did not affect the completion time for the task. g) End-effector area during the task did not change with the device. h) Range of motion of each joint did not significantly change with the device. The error bars indicate the standard deviations.
An active protector system using the sandwich jamming structure. a) Second skin composed of a rubber-laminated pyramidal core structure and woven face sheets for free-form deformation with a conductive fabric sheet and an outer enclosure. The thickness of the device is 14mm, a form factor to be embedded in a bunker gear. b) The flexible structure deforms freely with respect to the movement and shape of the body. In case of collision with an external object, it creates hard surfaces to distribute and dissipate the impact. c) When the sandwich structure is vacuumed, it effectively distributes a 50 N static load of a 12.7 mm diameter tip. The numbers inside the parentheses indicate the standard deviations. d) When a 1 kg steel ball (diameter: 63.5 mm) falls on the structure, the vacuumed structure prevents deformation effectively. e) Demonstration of the active protector with three different approaching speeds. By reading the capacitance change of the conductive fabric sheet, the system detects the distance of the object and vacuum the structure in advance to protect the wearer. f) Protecting strengths at the vacuum pressures in e). Higher yield force was achieved with higher vacuum pressure.
A selective hardening glove. a) We fabricated a sandwich jamming structure in the shape of four fingers and the back of a hand and attached to a commercial glove. When unjammed, the glove is flexible and guarantees dexterous hand movements of the wearer. When jammed, the glove hardens. b) Glove with a large stiffness difference between the unjammed and jammed conditions. c) Jammed glove not only distributes the pressure the hand receives but also increases the impact pressure applied to the local surface of an external object. d) When the glove is pressed with a 50N load on a pressure pad, the peak pressure was increased by 37% in the jammed condition. The numbers inside the parentheses indicate the standard deviations. e) Jammed glove increases the overall stiffness of the hand during a collision due to the large hard contact area. With the increased overall stiffness, the impact force can be larger due to the reduced time constant in a collision. f) Free fall experiment measuring the amount of increased impact force. By hardening the sandwich jamming structure, the maximum force increased up to 50%.