Mechanical propertiesof smart metarials

Smart materials have the ability to change more than one of its properties with external stimulis (e.g. stress, temperature, electric, magnetic field). These materials have wide range of applications in aerospace, automotive, medical, electronics and more. Thus its significance is rising for the next generations. Smart materials can be obtained either as entirely new developed product or by adding novel features to conventional materials. In this study, auxetic materials were mentioned, which were obtained by adding geometric features to conventional materials and which has an interest due to their different mechanical properties. 316L stainless steel is used in foil (very thin) structure which is accepted as conventional material which is used frequently in biomedical field. By using the femtosecond laser cutting method, a geometric shape with different cell sizes is processed from conventional material and a negative Poisson Ratio auxetic material is obtained. In order to determine the mechanical properties , tensile tests were applied on rectangular samples and the effect of cell size, thickness and elasticity modulus parameters on mechanical behavior is investigated. As a result of these tests , it has been found that the modulus of elasticity of the conven tional materials in foil structure is lower than the steels known elastic modulus obtained from bulk samples . Due to the porous structure of auxetics, it has lower modulus of elasticity than conventional materials but it can bear more deformation prior to failure and show a completely different failure pattern . At the same time, when compared to the size of cells and thicknesses of auxetics, it is understood that the auxetic effect is longer as the cell size is decreased and the thickness is increased. By means of the finite elements, the synclastic behavior, which occurs with the bending forces, has been visually examined in the auxetic sample. Keywords: Smart materials, Negative Poisson's Ratio, Auxetic