Enhancement of stability, durability, and performance of thermal barrier coating (TBC) systems providing thermal insulation to aero-propulsion hot-section components is a pressing industrial need. An experimental program was undertaken with thermally cycled eight wt.% yttria stabilized zirconia (YSZ) TBC to examine the progressive and sequential physical damage and coating failure. A linear relation for parameterized thermally grown oxide (TGO) growth rate and crack length was evident when plotted against parameterized thermal cycling up to 430 cycles. An exponential function thereafter with the thermal cycling observed irrespective of coating processing. A phenomenological model for the TBC delamination is proposed based on TGO initiation, growth, and profile changes. An isostrain-based simplistic fracture mechanical model is presented and simulations carried out for functionally graded (FG) TBC systems to analyze the cracking instability and fracture resistance. A few realistic FG TBCs architectures were considered, exploiting the compositional, dimensional, and other parameters for simulations using the model. Normalized stress intensity factor, K₁/K₀ as an effective design parameter in evaluating the fracture resistance of the interfaces is proposed. The elastic modulus difference between adjacent FG layers showed stronger influence on K₁/K₀ than the layer thickness. Two advanced and promising TBC materials were also taken into consideration, namely gadolinium zirconate and lanthanum zirconate. Fracture resistance of both double layer and trilayer hybrid architectures were also simulated and analyzed.

中文翻译：

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功能梯度高级热障涂层系统的损伤评估和抗断裂性能：实验和分析建模方法

增强热障涂层（TBC）系统的稳定性，耐用性和性能，为航空热推进部件提供热绝缘是迫切的工业需求。用热循环的八重量％氧化钇稳定的氧化锆（YSZ）TBC进行了实验程序，以检查进行性和顺序性的物理损伤和涂层破坏。当针对高达430个循环的参数化热循环作图时，参数化的热生长氧化物（TGO）的生长速率和裂纹长度的线性关系显而易见。此后，观察到具有指数指数的热循环，而与涂层处理无关。提出了基于TGO引发，生长和轮廓变化的TBC脱层现象学模型。提出了一种基于等应变的简单断裂力学模型，并对功能梯度TBC系统进行了仿真，以分析裂纹的不稳定性和抗断裂性。考虑了一些实际的FG TBC架构，利用组成，尺寸和其他参数来使用该模型进行仿真。归一化应力强度因子，提出了K ₁ / K ₀作为评价界面抗断裂性能的有效设计参数。相邻FG层之间的弹性模量差异对K ₁ / K _0的影响大于层厚度。还考虑了两种先进且有前途的TBC材料，即锆酸g和锆酸镧。还对双层和三层混合架构的抗断裂性进行了仿真和分析。