No abstract

In this study, a three‐dimensional printing technique is applied for the fabrication of novel functionally graded magnetic shape memory polymers (SMPs) to create high‐resolution multimaterial shape memory architectures. This approach is applied to a copolymer network of photocurable methacrylate using high projection stereolithography. Carbonyl iron particles (CIPs) were physically embedded in a polymer matrix to add magnetic functions to the SMPs. The glass transition characteristics and shape memory effect were also investigated by varying the composition of the SMP. The microstructured, lightweight SMPs showed interesting shape memory behaviors, as observed in hot environment. The almost perfect strain recovery rate of poly(ethylene glycol) dimethacrylate was measured (99.95% using a tension set bar). The results of dynamic mechanical analysis and thermogravimetric analysis reveal an increment in the thermal conductivity after embedding the CIPs. Further, the results of dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy reveal close interaction between the particles and matrix. X‐ray diffraction was used to characterize the iron particles and polymer structure. These results, along with the electrical and magnetic tests, strongly support the remote controllability of the material properties of the present functionally graded magnetic SMPs for a broad range of temperature and/or magnetically responsive material applications by using eddy current heating and/or magnetorheological polymeric effects. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45997.

A galloping-based energy harvester, which is surrounded by structure(s) such as an enclosure, has an aerodynamic force change due to a change in flow caused by movement of the bluff body against the structure(s). Therefore, any model derived without considering this effect cannot predict the harvester’s behavioral or energetic characteristics accurately. The main goal of this study was to develop a model that could be used to accurately simulate a galloping-based energy harvester surrounded by an enclosure. To consider the effect of the enclosure on the aerodynamic force applied to the bluff body, a bivariate quasi-static aerodynamic force model was newly proposed, which was accomplished by performing an experiment involving two variables, the attack angle, and the distance from the nearest wall of the bluff body. A set of governing nonlinear field equations reflecting this force model were derived, and their perturbed solutions were obtained and validated by comparison with experimental results. The effect of the enclosure on the performance of the present energy harvester system was investigated and discussed using both theoretical and experimental methods.

The feasibility of fabrication of shape memory polymers (SMPs) was investigated using a customized 3-dimensional (3D) printing technique with an excellent resolution that could be less than 100 microns. The thermorheological effects of SMPs were adjusted by contact and non-contact triggering, which led to the respective excellent shape recoveries of 100% and 99.89%. Thermogravimetric analyses of SMPs resulted in a minor weight loss, thereby revealing good thermal stability at higher temperatures. The viscoelastic properties of SMPs were measured using dynamic mechanical analyses, exhibiting increased viscous and elastic characteristics. Mechanical strength, thermal stability and viscoelastic properties, of the two SMPs were compared [di(ethylene) glycol dimethacrylate (DEGDMA) and poly (ethylene glycol) dimethacrylate (PEGDMA)] to investigate the shape memory behavior. This novel 3D printing technique can be used as a promising method for fabricating smart materials with increased accuracy in a cost-effective manner.