Frequency Control of Beams and Cylindrical Shells With Light-Activated Shape Memory Polymers

Light activated shape memory polymer (LaSMP) is a novel smart material. It realizes the shape memory function under the exposure of laser lights with two different wavelengths. During the exposure process, the stiffness of LaSMPs also changes. With this noncontact actuation feature, this study presents a new technique to manipulate frequencies of beams and cylindrical shells. Fundamental LaSMP mechanism and its stiffness manipulation are presented first. The LaSMP/elastic coupled dynamic equations of cylindrical shells coupled with LaSMPs are established first and then simplified to the governing equation of beams. In case studies, the natural frequency of a cantilever beam laminated with LaSMP patches is studied. Furthermore, the length of LaSMP patches is varied to broaden its frequency variation range. Results show that the maximum frequency change ratio reaches to about 24.5% on beams. A simply supported cylindrical shell laminated with LaSMPs on both the inner and outer surfaces is also analyzed and its frequency varies about 6% for the lowest (1,4) mode. Thus, adopting LaSMPs to manipulate the structural frequencies is a new noncontact actuation technique in vibration controls.