Multi-trigger mechanism with shape memory polymer nanocomposite



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Shape memory polymers (SMPs) and their composites are set of smart materials that exhibit a special ability to recover a trained shape deformation upon activation of a single environmental trigger. This ability has made SMPs an emerging technology and has provided novel solutions for applications such as actively expandable vascular stents, deployable space structures, and releasable fasteners. However, the single trigger can be problematic in applications where an ambient field can accidentally trigger the SMP or where direct mechanical access is not available for training of SMP. This research has thus investigated a novel multi-trigger SMP nanocomposite. This SMP nanocomposite is sensitive to thermal and magnetic fields and requires both fields to be applied for shape deformation. SMP nanocomposites were manufactured using a commercially available SMP and magnetite nanoparticles at varying weights (5, 10, 15, 20, and 25 wt.% magnetite). Basic thermomechanical testing of the SMP nanocomposites at ambient conditions and transition conditions along with specially created thermomechanical-magnetic tests have been performed and have shown the multiple sensitivities of the SMP nanocomposites. Further, the varying addition of the magnetite nanoparticles and/or the applied magnetic field to the SMP nanocomposite shows results with higher magnetic sensitivity as well as larger shape deformations. Based on this special behavior, a constitutive model has been presented for the SMP nanocomposites. This constitutive model considers four specific phases of the SMP nanocomposites that are defined by the initial/final configurations of the SMP nanocomposite following and during the application of transition state environmental conditions. This model has been used within LS Dyna FEA to simulate the multi-trigger behavior of the SMP nanocomposite. The simulations have matched closely the actual test case scenario and have validated the developed constitutive model. Further, simulations have been performed to test the SMP nanocomposite in the application of active disassembly. From these simulations, a definite case can be made for the SMP nanocomposite over its SMP counterpart per reduced processing time. This research has exhibited novelty through the documentation of the multiple field sensitivities of the SMP nanocomposite smart material. Smart material research, especially with SMPs, has focused on shape memory actuation on application of a single trigger (i.e. heat, light, chemical, electrical, magnetic, etc.). This research looks to expand on this research by analyzing and understanding the special behavior of a developed multi-trigger SMP nanocomposite. This research documents the multiple field properties and actuation strategies for SMP nanocomposites. The development and study of these materials can create a transformative new dimension for smart material research that will provide additional avenues for manufacturers in smart material applications. Furthermore, this research can create a number of opportunities that extend beyond the technical contributions produced. The key will be in the use of the derived constitutive model as a design tool, which could be used in a number of fields.



Shape memory polymers, Nanostructured materials, Magnetism, Nanomaterials and their applications, Nanocomposites (Materials)