Mechanical behavior of self-entangled single wire materials

Abstract

Fibrous entangled media are interesting architectured materials because of their numerous different applications, such as thermal insulation, mechanical reinforcement, filtration and biomedicine. Entangled materials have recently been more investigated, due to the poor mechanic properties (such as frailness) that usually present porous sintered metals. [1,2]. However, their mechanical behavior is complex and still not well explained, although comparatively, for example the nowadays available knowledge about metal foams is much extensive [3-5]. The objective of this work is to expand the current experimental data base on this kind of materials, in order to characterize and better explain their mechanical behavior. For this purpose various fibrous self-entangled media were elaborated with porosity values ranging from 42% to 75%. These entangled samples were made of three types of fibers/wires with different mechanical behavior: polyamide fibers (presenting elastic behavior), NiTi wires (presenting superelastic behavior) and copper wires (presenting elastoplastic behavior). All three types of fibers/wires had the same nominal diameter (500μm), and their tensile behavior was characterized in this work. To obtain cylindrical entangled samples from the fibers and the wires, a specific manufacturing process was developed for each type of material. A local strain measurement method was developed as well, to accurately assess axial, lateral, and volumetric strains of interest zones of the samples. In order to characterize the entanglements mechanical behavior, the manufactured samples were subjected to uniaxial compression and tension tests up to axial strain values of 30%.