Numerical determination of mechanical properties of concrete-filled auxetic composites

This study consists of two parts. In the first part, nine composite structures were obtained by filling concrete into six auxetic (re-entrant, arrowhead, new arrowhead, lozenge grid, formed from square grid and star honeycomb) and three conventional (honeycomb, isogrid and rectangle grid) lattice structures with constant relative density. The behavior of these composite structures under compression was investigated by creating numerical models. Numerical analysis were conducted to examine the effects of the Poisson's ratios and stiffnesses of the lattice structures used in the composites on the behavior of the composite structures. It was determined that the structure with the highest strength and energy absorption capacity was the concrete-filled rectangle grid. In the second part, the models with the highest strength and energy absorption capacity are selected as one each for concrete filled auxetic and conventional lattice structures. Re-entrant is considered for the auxetic lattice, while the rectangular grid structure is used for the conventional lattice. A parametric study was performed on the unit cell thicknesses and sizes of the lattices in these composite structures and their strength and energy absorption capacities were compared. It was observed that as the unit cell thickness of the lattices used in these two composites increased, the concrete-filled re-entrant lattice exhibited much higher strength and energy absorption capacity than the concrete-filled rectangle grid lattice. As the unit cell size of the lattices used in these two composites increased, it was revealed that the strengths of both composite structures decreased. When all the studies are evaluated, it is determined that concrete-filled re-entrant structure showed better mechanical behavior than concrete-filled rectangle grid structure at an appropriate lattice unit cell thickness and size.