Counterintuitive modulus from semi-auxetic laminates



Semi-auxetic laminates consist of conventional and auxetic laminas such that the interlacing effect results in overall properties that are absent in both conventional and purely auxetic materials. Of late it has been shown that the in-plane Young's modulus of a semi-auxetic laminate always exceeds the rule of mixtures. In this paper, the conditions by which the in-plane modulus exceeds the stiffness of the phase with higher modulus is established. In addition, an example is demonstrated whereby the maximum point of the in-plane modulus occurs where the volume fraction of the stiffer phase is lower than that of the more compliant phase.