Additive manufacturing or 3-D printing is the process of creating a three-dimensional object from a 3-D digital model. In recent years, it has been used as a tool to help create structures that were too complex for traditional manufacturing methods. It also allows for the use of materials that have a variety of material properties that vary on strength, toughness, and ductility. Additive manufacturing can be used to create structures inspired from biology. 3-D printed materials with shape morphing capability that respond to external stimuli such as heat, light, and electricity have become known as 4-D printing. One such aspect of 4-D printing is the use of ferromagnetic nanoparticles in structures to increase the mechanical properties when a magnetic field is applied. In this study, 3-D printed honeycomb-based designs and crocodile-based armor designs incorporated ferromagnetic particles to increase material properties. The samples were fabricated by additive manufacturing using an elastic resin. There were three honeycomb-based structures, a traditional honeycomb, a bamboo-inspired honeycomb, and a pomelo-inspired honeycomb. All ferrofluid filled honeycomb structures exhibited an increase in effective stiffness when a magnetic field was applied. Further, the bamboo-inspired honeycomb was tested at different strengths of the magnetic field. The results showed that as the magnetic field decreased, the stiffness decreased. Finally, the crocodile-based armor design was tested and found that the ferromagnetic particles were practical in the application of a smart-armor by increasing the samples strength.