Design and modeling of auxetic and hybrid honeycomb structures for in-plane property enhancement

Honeycomb structures have been used extensively in lightweight sandwich structure and impact energy absorption applications. Recently the research has been carried out on auxetic honeycombs that have negative Poisson's ratio (NPR). Auxetic structures are attractive for various engineering applications because of their unique mechanical properties, volume change control and excellent impact energy absorption performance. In this study, novel design and performance improvement of new auxetic-strut structures were presented. A comparative study of in-plane uniaxial compression loading behavior of regular honeycomb, re-entrant auxetic honeycomb, locally reinforced auxetic-strut structure and a hybrid structure of combining regular honeycomb and auxeticstrut structure was conducted on 3D printed samples. The deformation and failure modes of the different cells were studied and their performance was also discussed. The new auxetic-strut structure showed better mechanical properties than the honeycomb and auxetic structure. For example, the compressive strength of the auxeticstrut design is similar to 300% more than that of honeycomb structure and similar to 65% more than that of auxetic structure. With lower values of the Poisson's ratio, the new design can absorb more energy when compared to the other structures. Hybrid structure of auxetic-strut and honeycomb cells allows us tailor the deformation paths to provide desired failure modes. (C) 2016 Elsevier Ltd. All rights reserved.