RIMI: High Temperature Fatigue of Continuous Fiber Reinforced Silicon Carbide/Silicon Nitride Composites

将测试连续纤维增强陶瓷复合材料（CFCC） 在室温和高温下进行疲劳试验， 疲劳现象随温度的变化。 层压试样 SiCf/Si 3 N4（碳化硅纤维增强氮化硅 具有对称铺层的复合材料将受到 拉伸-拉伸疲劳 疲劳试验前，拉伸性能 将在不同温度下表征，以确定 强度，并决定具体的温度， 进行高温疲劳试验。 房间 温度疲劳试验将在不同的应力比下进行 范围从0到0.5，频率从1到10 Hz，观察它们对复合材料疲劳寿命的影响。 高温疲劳试验将在等温 保持循环载荷作为主要驱动力的条件 复合材料失效的原因 NDE和SEM表征将 进行了损伤和失效特征评估 合成物。 与力学测试、有限元平行 将进行分析，以研究 在拉伸和疲劳载荷下的层压板。 分层壳体 基于一阶剪切变形的单元 理论将被使用。 大变形和塑性应变 行为将被视为考虑几何和 分析中的材料非线性。 累积疲劳损伤 根据Miner规则和实验S-N曲线， 在有限元模型中模拟，以研究层合板响应 在两个和三个应力水平的循环载荷下。 很少有标本 在累积疲劳下进行试验，以验证有限元结果。 拟议的研究将由三个学院进行相关 塔斯基吉大学材料研究实验室（MRL） 这是一个多学科的设施， 高性能材料的表征，包括先进的 复合材料. 建议让六名少数民族毕业生 学生和六名少数民族本科生在一段时间内， 三年 该计划还将允许赞助部门 招募有才华的少数民族教师和学生。

Continuous fiber reinforced ceramic composites (CFCC) will be tested under fatigue at room and elevated temperatures to study the variation in fatigue phenomena with temperature. Laminated coupons of SiCf/Si3N4 (silicon Carbide fiber reinforced Silicon Nitride matrix) composites with symmetric layups will be subjected to tensile-tensile fatigue. Prior to fatigue tests, tensile properties will be characterized at various temperatures to determine the strength, and to decide about specific temperatures at which the elevated temperature fatigue tests are to be conducted. Room temperature fatigue tests will be performed at various stress ratios ranging from 0 to 0.5, and which frequencies varying from 1 to 10 Hz, to observe their effects on the fatigue life of the composite. High temperature fatigue tests will be conducted under isothermal conditions to maintain the cyclic loading as the main driving force for the composite failure. NDE and SEM characterization will be performed to evaluate the damage and the failure characteristics of the composite. Parallel to mechanical testing, finite element analysis will be performed to investigate the non-linear response of the laminate under tensile and fatigue loading. Layered shell element developed on the basis of first order shear deformation theory will be used. Both large deformation and plastic strain behavior will be considered to account for the geometric and material non-linearities in the analysis. Cumulative fatigue damage bases on the Miner's rule and the experimental S-N curve, will be simulated in the finite element model to study the laminate response under two and three stress level cyclic loading. Few specimens will be tested under cumulative fatigue to verify the FEM results. The proposed research will be conducted by three faculty associated with the Tuskegee University's Materials Research Laboratory (MRL) which is a multi-disciplinary facility developed for synthesis and characterization of high performance materials including advanced composites. It is proposed to involve six minority graduate students and six minority undergraduate students over a period of three years. The program will also allow the sponsoring department to recruit talented minority faculty and students.