Mimicking the Anisotropic Behavior of Natural Porous Structures by Controlling the Reinforcing Particles Distribution in Polymeric Foams

Natural porous materials, like wood or bone, are multiscale cellular composite structures which exhibit mechanical (such as elasticity and strength) and functional (such as the thermal or acoustic insulating properties) behaviors dependent on the measuring direction. They show the best performance/weight ratio among all materials because their response is optimized in the needed direction by removing matter where not strictly functional, giving as a result a strong structural as well as morphological anisotropy. A new approach has been developed to mimic this behavior in polymeric foams, in which the mechanical and/or functional response of the cellular structure is tailored in a specific direction through the control of the spatial distribution and configuration of reinforcing particles. In order to demonstrate the concept, polymeric foams were produced with micro- or nano-sized reinforcement distributed along specific directions by means of the magnetic field. The effects of particles content, production parameters, and magnetic field strength were investigated and related to the mechanical (both elastic and magneto-elastic) performances.