Several medical papers have reported delamination of the coating from the stent-substrate following intravascular deployment leading to adverse outcomes for patients. However, the mechanisms of delamination of such polymer coatings from the surface of a stent due to large deformations during device deployment have not been studied. In this paper, a novel and in-depth investigation of the mechanisms and parameters that govern stent-coating delamination is performed, using a cohesive zone formulation to simulate the evolution of traction at the stent-coating interface. The study firstly analyses the behaviour of elastic coatings on idealised elastic stent substrates. Simulations reveal that the mode mixity of delamination is strongly dependent on the level of stent deployment at initiation. In general, peak normal tractions exceed peak shear tractions at low levels of stent deployment whereas the reverse trend is computed at high levels of stent deployment. Interface tractions increase with both increasing stent thickness and coating thickness suggesting that thinner stents and thinner coatings should be utilised for the delivery of antiproliferative drugs to reduce the risk of coating delamination. Next, the influence of stent plasticity on interface tractions and coating delamination is investigated. Even at low levels of deployment, plastic yielding occurs in the stent hinge region and the patterns of normal and shear tractions are found to be significantly more complex than those computed for the elastic stents, with both tensile and compressive regions of normal traction occurring in the stent arch. At a high level of stent deployment shear tractions at the stent-coating interface are computed to increase with decreasing strain hardening modulus. The findings of this paper provide a new insight into the stress-state at the stent-coating interface as a function of the stent design parameters and large deformation elasticity and plasticity during deployment, allowing for a more reliable assessment of the limits relating to safe implantation of coated stents.

几篇医学论文报道了在血管内展开后涂层从支架-基材上分层，从而导致患者的不良后果。然而，尚未研究由于在装置展开期间大的变形而使这种聚合物涂层从支架表面脱层的机理。在本文中，使用内聚区公式模拟支架-涂层界面处的牵引力演变，对控制支架-涂层分层的机理和参数进行了新颖而深入的研究。该研究首先分析了理想弹性支架基材上弹性涂层的行为。模拟表明分层的模式混合在很大程度上取决于支架在开始时的展开水平。一般来说，在低水平的支架展开过程中，峰值法向牵引力超过峰值剪切牵引力，而在高水平的支架展开处计算出反向趋势。界面牵引力随着支架厚度和涂层厚度的增加而增加，表明应使用更薄的支架和更薄的涂层来输送抗增殖药，以减少涂层分层的风险。接下来，研究了支架可塑性对界面牵引力和涂层分层的影响。即使在较低的展开水平下，塑性屈服也会发生在支架铰链区域，并且正常和剪切牵引的模式比弹性支架计算的要复杂得多，而正常牵引的拉伸和压缩区域都发生在支架的铰接区域。支架弓。在高水平的支架展开下，支架-涂层界面处的剪切力被计算为随应变硬化模量的减小而增加。本文的发现提供了对支架-涂层界面应力状态的新见解，该应力状态是支架设计参数以及展开过程中大变形弹性和可塑性的函数，从而可以更可靠地评估与安全植入有关的极限涂层的支架。