Rate activated tether (RAT) dynamic strapping material

Self-adjusting technology that is stretchable under normal use but rigid in response to large forces

Rate Actuated Tether (RAT) Dynamic Strapping Material technology developed by the Army

Eric Wetzel at the Army Research Laboratory has developed a dynamic tether (a), using simple components (b) and shear thickening fluid, that is flexible and self-adjusting under normal use but highly resistive to rapid movements. Applications include buckle-free helmet straps (c).

The U.S. Army Research Laboratory (ARL) has developed and tested a patent-pending technology that incorporates shear thickening fluid into a dynamic strapping material, called RAT Strap. The RAT Strap stretches and retracts under normal use in a manner similar to an elastic strap; however, when subjected to a large force, it becomes up to 10x more resistive in a fraction of a second. The result is a strap component that self-adjusts in size to the user or application, stretches to allow comfortable movement during typical use, but hardens to provide restraint against impacts or other undesirably large rapid movements.

ARL’s technology is simple, consisting of one or more filaments inside a tube filled with a customizable discontinuous shear thickening fluid. The dynamic ligament could be applied to numerous products, including self-adjusting helmet straps that do not require buckles or adjustment slides, braces that dynamically protect the user under certain potentially injurious conditions, and industrial and military safety gear that is comfortable to wear during typical use but provides enhanced safety and security under adverse conditions.

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