Segmented Reinforcement Variable Stiffness Materials for Reconfigurable Surfaces

Abstract

Reconfigurable and morphing structures may provide a range of new functionalities such as optimization over broad operational conditions and multi-mission capability. This article introduces a new generic approach to achieving large strains in materials with high elastic moduli (5-30 GPa). The work centers on creating variable stiffness composite materials which exhibit a controllable change in elastic modulus (bending or axial) and large reversible strains (5-15%). We have performed a simulation study to better understand the implication of various geometric design parameters on the elastic and deformation behavior. Using this information, a series of prototype materials were prepared using a commercial shape memory polymer, and measurements on these materials indicate a controllable change in stiffness as a function of temperature with large reversible strain accommodation. We have fabricated and tested several design variations of laminar morphing materials which exhibit structural stiffness values of 8-12 GPa, changes in modulus of 15-77x and large reversible axial of 2-10%. Results indicate that significant controllable changes in stiffness are possible. Further, agreement between simulations and prototype material properties indicate that simulations may be used an effective screening tool to specify micromechanical design variations for specific application requirements.

Materials that couple sensing, actuation, computation, and communication

“…At higher temperatures, the thermoplastic has much less resistance to shear and the plates act as if they were uncoupled from each other, creating a composite with a much lower stiffness. A similar approach is shown in (50,51), which segments the rigid layers and uses a shape memory polymer (52) as the sandwich layer. Instead of melting, friction between plates can also be altered pneumatically.…”

Flexible Medical Devices: Review of Controllable Stiffness Solutions

“…A flexible heater is used to modify the temperature of the polymer and change its shear behavior in order to couple or decouple the stiff layers. In [27], a Shape Memory Polymer (SMP) demonstrates a variable stiffness element in a sandwich configuration with rigid elements.…”

Development of a Span-Extending Blade Tip System for a Reconfigurable Helicopter Rotor

“…22 Though these advanced blade shapes are static, feasibility of dynamic shape changing skin technologies has been proven for one-dimensional structures 23,24,25 and airfoil structures. 26,27 Hence, it appears that the maturity of these types of components has progressed to a level where design for fabrication and testing on a rotorcraft system is possible. Herein, shape-changing rotor blades could be designed to account for the conflicting requirements of advancing and retreating blades, approaching an aerodynamic optimum, or to change configuration for optimal hover or forward flight performance.…”