This article deals with the buckling of periodic lattices in order to generate an auxetic behavior, sometimes called "metamaterials" for unknown reasons. The title of the paper is misleading since designing auxetics is not at the core of this work, as a matter of fact the design considered has been around for a few years now, as the literature review given by the authors shows. One important reference on plasticity of auxetics has been forgotten: R. Gilat and J. Aboudi, Behavior of Elastoplastic Auxetic Microstructural Arrays, Materials, 6, 726-737 (2013). There are only 2 references on this topic, Dirrenberger et al. (2012) and the latter, which happens to be published in the present journal. Moreover, in lines 84-87, it is stated that Andersson et al. (2008) developed an anisotropic compressible plasticity framework for auxetics, although there is no such things in the cited paper which deals with compression experiments on polyurethane foams. I believe the authors refer to the anisotropic compressible plasticity framework developed in Dirrenberger et al. (2012). This is just an example of several miscitations that I have observed in the paper. For instance, the original paper of Lakes on auxetics should be cited: Lakes, R., Foam structures with a negative Poisson's ratio. Science, 235(4792), 1038-1040 (1987). Another example, line 254, Shen et al. is cited but as reference 41 instead of 42. The authors should verify every citation for potential publication. Regarding the form of the paper, some formulations are clumsy, but one is just not acceptable for a scientific paper and should be removed: line 212-213, "a complicated casting process provided by Shapeways company".The authors should always be clear and specific. The authors should always be clear and specific. Which brings me to the scientific soundness of the paper. Firstly, in a community obsessed with modelling and simulation, it is courageous and very useful to make actual experiments on auxetics. Nevertheless, only a few technical details are given regarding the material behavior and propreties, it is eluded in one sentence line 160-161 for yield strength the reader is sent to another recent paper by the same group (quite redundant with this one by the way) instead of just giving the value directly. For studying plastic buckling I think that yield strength should be presented and discussed in more details. Nothing is stated about potential anisotropy for the constitutive material behaviour. Also, the constitutive plasticity law used is not described explicitely, nor justified. Except these few remarks, the experiments and simulations seem sound and are analysed properly. An interesting result is discussed line 571-572 about the increasing hardening ratio enhancing the auxetic behavior, this is in accordance with what was shown by Dirrenberger et al. (2012), i.e. increasing the isotropic hardening modulus resulted in an enhanced auxetic effect (NPR closer to -1), I think it would add value to the discussion if the connection was made betwenn these two independent results, although this is just a suggestion. Also, it was appreciated that the authors took some precautions in the last paragraph of the conclusions regarding the experiments and their limit of validity, it is not often seen in the experimental mechanics community, especially regarding auxetics, or worse: metamaterials. This paper should be considered for publication after minor revision.