Structural design and mechanical characterization of an auxetic advanced grid structure composite

The structural design, manufacture and mechanical evaluation of an auxetic advanced grid structure (AGS) composite were investigated. The mechanical behavior of the auxetic AGS composite under the compressive loading was simulated via finite element method (FEM). The auxetic AGS composite was fabricated via autoclave processing, and the processing quality and mechanical properties were evaluated. The simulation results show that the auxetic AGS composite after deformation is in a corrugation shape, which is different from the saddle deformation shape of the orthogonal AGS composite. Compared with the orthogonal AGS composite, the transverse expansion is lower and the stress is more uniformly distributed. An 30° included angle between grid and axis is the most optimal structure for the auxetic AGS composite. Excellent manufacturing quality and superior mechanical properties are found for the MT300/603 carbon fiber/epoxy auxetic AGS composite. The mechanical experiment results show the optimal MT300/603 auxetic AGS composites have a compression modulus of 65.92 GPa and a compression failure load of 64.65 kN. The failure occurs between the grid and skin at the crossing of the grids, showing a higher compression strength than the orthogonal AGS composite. The optimal MT300/603 auxetic AGS composite exhibits a characteristic negative Poisson’s ratio. The AGS composite structure with superior overall mechanical performance can potentially be used on aerospace structures.