Metamaterials, as substances with unconventional properties, play a decisive role in advanced technologies such as aerospace, robotics, an‎d biomedical engineering. These materials are capable of exhibiting unique mechanical an‎d thermal behaviors not found in conventional materials. The simultaneous achievement of auxetic properties an‎d negative thermal expansion has been the primary objective of this research. In this dissertation, an auxetic structure based on a combination of chiral an‎d anti-chiral architectures was designed. By employing an asymmetric geometric design approach an‎d utilizing two materials with different coefficients of thermal expansion, the simultaneous realization of auxetic behavior an‎d negative thermal expansion was made possible. Subsequently, using parametric modeling in ABAQUS software, a three-dimensional unit cell geometry was designed. The Taguchi design of experiments method was employed to systematically investigate the effect of five key geometric parameters. Finite element simulations were conducted to extract mechanical an‎d thermal properties, an‎d mesh convergence studies were performed to ensure the accuracy of numerical results. Analysis of the results was carried out using the signal-to-noise ratio method, an‎d the significance of each parameter was determined based on its impact on the outcome. Finally, the accuracy of the numerical results was validated through experimental tests on fabricated samples. The obtained results indicated that the proposed structure successfully exhibits simultaneous auxetic behavior an‎d negative thermal expansion. Analysis of the results revealed the significant influence of geometric parameters on the mechanical an‎d thermal properties of the structure. The parameters of inter-plate distance an‎d the aspect ratio of the unit cell ligaments were identified as the most effective factors. Comparison of numerical an‎d experimental results confirmed the validity an‎d accuracy of the proposed model.

رضا جعفري ندوشن , عليرضا شهيدي ريزي

مهدي كاظمي

صالح اكبرزاده , مهدي سلماني تهراني