Geometric effects of sustainable auxetic structures integrating the particle swarm optimization and finite element method

The development of new materials based on industrial wastes has been the focus of much research for a sustainable world. The growing demand for tyres has been every year exacerbating environmental problems due to indiscriminate disposal in the nature, making a potentially harmful waste to public health. The incorporation of rubber particles from scrap tyres into polymeric composites has achieved high toughness and moderate mechanical properties. This work investigates the geometric effects (thickness, width and internal cell angle) of auxetic structures made of recycled rubber composites based on experimental and numerical data. The response surface models integrated with the swarm intelligence and finite element analysis were proposed in order to obtain a range of solutions that provides useful information to the user during the selection of geometric parameters for reentrant cells. The results revealed the cell thickness ranges from 39-40 mm and 5.98-6 mm, and the cell angle range from -0.01 to -0.06° maximize the ultimate strength. The same parameters were able to optimize the modulus of elasticity of rubber auxetic structures, excepting for the angle factor which must be set between -30° and 27.7°. The optimal Poisson's ratio was found when the cell angle ranged from -30° to -28.5°, cell width ranged from 5-5.6 mm and 2 mm in thickness.