Experimental study of defects influence on auxetic behavior of cellular structure with curvilinear elements

Abstract

In this paper uniaxial tension of two-dimensional auxetic cellular structures is studied experimentally. Various samples were made by the laser cutting method from nonauxetic polyethylene terephthalate (PET-A amorphous) planes of size 112.5 × 24 × 0.7 mm with central area of 28 × 24 × 0.7 mm. The transverse size of elements of hexagons was equal to sample thickness. The samples were subjected to monotonous uniaxial tension until the last moment when they still remained plane. Comparison of mechanical properties of the defect-free cellular structures consisting of concave hexagons with straight elements and concave hexagons in which part of straight elements is replaced with curvilinear elements is given as a result of experimental analysis. Cellular structure with straight elements showed lower value of Poisson’s ratio in comparison with cellular structure with curvilinear elements. Influence of defects on mechanical properties of cellular structure with curvilinear elements is studied. We conclude that for the considered samples of cellular structure with curvilinear elements at uniaxial tension, loss of one horizontal element (near the center of the sample) changes effective mechanical properties much less than for the case of same structure with one vertical element being absent. As a result, tensile force – displacement diagram for four samples was calculated from the experimental data.