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Micromechanical analysis of nonwoven materials with tunable out-of-plane auxetic behavior

: Rawal, Amit; Sharma, Sumit; Kumar, Vijay; Rao, P.V. Kameswara; Saraswat, Harshvardhan; Jangir, Nitesh Kumar; Kumar, Rajat; Hietel, Dietmar; Dauner, Martin


Mechanics of materials 129 (2019), S.236-245
ISSN: 0167-6636
Fraunhofer ITWM ()

Needlepunched nonwovens represent a special class of three-dimensional (3D) fiber networks that successfully generated a host of applications but the rationale of their design involving the intricate microstructure and understanding of the mechanics of the relevant deformation is still lacking. Herein, the micromechanical behavior of needlepunched nonwoven materials possessing out-of-plane auxetic characteristics has been investigated by unraveling the anisotropic structure. The evolution of the 3D intricate architecture of anisotropic nonwoven materials under prescribed levels of tensile strain has been determined using a 3D optical profiler. Most importantly, the analytical models expressed in terms of the initial modulus and in-plane Poisson's ratio of the nonwoven materials are presented. A comparison between the theory and experiments revealed a satisfactory agreement for the modulus and in-plane Poisson's ratio. Further, a comparative analysis of well-known analytical models of in-plane Poisson's ratio with the experimental data clearly demonstrated that the plausible mechanism of deformation of fibers is bending and not stretching.