Switchable stiffness morphing aerostructures based on granular jamming

One of the persistent challenges facing the development of morphing aerostructures is the need to have material and structural solutions which provide a compromise between the competing design drivers of low actuation energy and high stiffness under external loads. This work proposes a solution to this challenge in the form of a novel switchable stiffness structural concept based on the principle of granular jamming. In this paper, the concept of using granular jamming for controlling stiffness is first introduced. Four-point bending tests are used to obtain the flexural rigidity and bending stiffness of three different granular materials under different levels of applied vacuum loading. Non-linear Finite Element Analysis simulations using experimentally derived non-linear material properties shows good agreement with experiment. A specific application of this concept it then proposed based on the Fish Bone Active Camber morphing airfoil. A unit cell of this concept is built, tested, and analyzed, followed by the first prototype of a complete switchable stiffness Fish Bone Active Camber morphing airfoil, which is experimentally shown to be able to achieve an increase in stiffness of up to 300% due to granular jamming.