Material BehaviourFabrication and vibration characterization of electrically triggered shape memory polymer beams

Shape memory polymers (SMP) exhibit temperature, frequency and strain rate dependent properties which may be manipulated by various types of external stimuli to achieve desirable response characteristics. In recent years, the emphasis has been on designing SMPs which do not require external stimuli (such as a heat source) and have a rapid response time with large homogenous and reversible deformation characteristics. In this research, the fabrication process and dynamic vibration testing of an electrically activated SMP are presented. It is shown that conductive SMP beams can be fabricated to achieve tunable stiffness and damping with a reasonable thermal gradient generated by electrical triggering. This can allow the tuning of a range of frequency bandwidth and damping properties of SMPs for vibration control applications. The experimentation yielded modal properties (natural frequencies and damping) of the SMP beams. These parameters were validated against values obtained from the estimated performance of these beams based on the complex modulus parameters obtained using dynamic mechanical analysis (DMA). For a modest 20 °C temperature range in an epoxy based SMP, a resulting shift of approximately 7% in the natural frequency and 100% change in the damping ratio of a rectangular beam was successfully attained. These results recommend SMPs as being tunable materials that can enhance vibrational performance and expand the operational envelope of structures.