Executive Summary : | Atherosclerotic coronary artery disease (ACAD) is primarily caused by a restricted supply of blood to the heart due to the hardening or narrowing of the arteries. It is one of the leading causes of mortality in India and worldwide. Therefore, a stent is inserted into an abnormally narrowed artery or vessel to open it mechanically and maintain the blood flow inside it. There has been ever-increasing interest in nitinol-based self-expandable stents due to their unusual shape memory effect in addition to the superelasticity, crush recoverability, biocompatibility, corrosion resistant, unusual elastic hysteresis, superior biased stiffness and kink resistance. The nitinol-based stents can be fabricated in the form of coils, sheets, hexagonal cells, and knitted and braided structures. Braided stents have distinct advantages over the other types of stents due to their superior toughness, excellent fatigue strength, crush resistance, and lower cost. Thus, the mechanical characteristics desired for any stent can be potentially developed in the braided structures. This requires appropriate design and development of braided stents by fundamentally understanding the constituent material behaviour, the role of process parameters, and the structural characteristics of braids. Therefore, the main objective of the proposed work is to optimally design and engineer the triaxial braided nitinol stents based on their geometrical and mechanical characteristics. The analytical models of mechanical properties, including tensile, bending, and compressional models of triaxial braided nitinol stents, will be developed and validated with the appropriate experimental work. The development of mechanical models will optimise braided stents for radial stresses, minimum compressional hysteresis and superior biased stiffness. A comparison would be made between the mechanical behaviour of biaxial- and triaxial braided nitinol stents having the same volume fractions of nitinol. The proposed work has the potential to have a high impact in the upcoming field of biomaterials as the braided stents will be engineered based on the first principles of constituent material properties in relation to the process conditions. The proposed work is anticipated to lead to a deeper understanding of engineering design and the development of braided stents. |