Stability control of active compressed rods with shape memory polymers

In structural systems, applied compressive force fields cause second-order effects that may not only influence the buckling behavior, but also enhance the internal stress and the deformation field in the structure. Specifical ly, slender and thin-walled structural elements subjected to compressive fo rce fields may experience buckling instability, which may affect their serv ice life. In the case of imperfection-sensitive systems, loading and geomet ric imperfections may drastically affect the buckling response and reduce t he buckling resistance. This behavior may be positively influenced by a s t ructural adaptation to bending effects. In this connection, an attempt is m ade to use the potentials o f the adaptive systems t o influence the second -order as well as the buckling response of the slender compression elements by means of the actuator components. To this end, the s tability control p roblem of adaptive slender rods with embedded Shape Memory Polymer (SMP) ac tuators is theoretically treated. The main goal of this investigation was t o explore the possibility of minimizing the end deflection of a cantilever rod under eccentrically applied force via actuation of an SMP fiber. First, the s tability theory of spatial rods is outlined, and the non-linear gove rning equations of straight rods are derived. The specific case treated is the problem of a cantilever rod with a single eccentric SMP fiber under ecc entrically applied end compressive force. Numerical calculations were carri ed out with the help of the Runge-Kutta method. It is shown that the respon se of the rod can be effectively controlled by the appropriate action of th e SMP actuator. Specifically, the goal of minimizing the end deflection of the eccentrically loaded cantilever rod through the action of the SMP actua tor is achieved. In carrying out the computations, the second-order effects arising from the action of SMP fiber as well as the axial force were taken into consideration. Moreover, the follower action of the SMP force was con sidered.