This paper presents an experimental investigation on the effect of structural (geometrical) design on the thermomechanical behavior of shape memory polymers. Three beams with identical dimensions (length, width, and thickness), material, and mass, but with different geometrical cells (honeycomb, diamond, and rounded rectangle) are designed by solving a set of nonlinear equations and produced using additive manufacturing method. Then, thermomechanical tests under bending and tensile loading at different temperatures are conducted. As a result, shape recovery and force recovery of the beams, due to the shape memory behavior of the material, are measured. In bending and tensile tests, shape and force recovery results of each beam are compared with their own pre-force and other beams. According to the results, the beam with rounded rectangle cells has the most shape recovery and force recovery ratios (compared to its applied pre-force). Shape recovery for this beam type in bending and tensile tests is 93.03% and 87.86%, respectively. The beam with honeycomb cells requires more pre-force in bending and tensile modes for programming, which leads to a higher maximum force recovery, due to its higher strength.

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An exact frequency analysis of a rotating beam with an attached tip mass is addressed in this paper while the beam undergoes coupled torsional-bending vibrations. The governing coupled equations of motion and the corresponding boundary condition are derived in detail using the extended Hamilton principle. It has been shown that the source of coupling in the equations of motion is the rotation and that the equations are linked through the angular velocity of the base. Since the beam-tip-mass system at hand serves as the building block of many vibrating gyroscopic systems, which require high precision, a closed-form frequency equation of the system should be derived to determine its natural frequencies. The frequency analysis is the basis of the time domain analysis, and hence, the exact frequency derivation would lead to accurate time domain results, too. Control strategies of the aforementioned gyroscopic systems are mostly based on their resonant condition, and hence, acquiring knowledge about their exact natural frequencies could lead to a better control of the system. The parameter sensitivity analysis has been carried out to determine the effects of various system parameters on the natural frequencies. It has been shown that even the undamped systems undergoing base rotation will have complex eigenvalues, which demonstrate a damping-type behavior.

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