A Study of Crack Propagation Paths in Functionally Graded Material Plates

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This research project consists of two parts : [1] Study of thermal stress intensity factors in the functionally graded material plates (FGPs) with cracks under thermal load, [2] A study of crack propagation paths in FGPs under thermal load by Finite Element Methods (FEM).PART [1] : Study of constitutional equations of the functionally graded materials (FGMs) under thermal loading.(1) We proposed a laminated composite model to study FGMs with arbitrary compositional profile subjected to thermal loading.(2) Multiple crack problems could be treated by the proposed a laminated composite model.(3) When FGPs with collinear crack are subjected thermal loading, stress intensity factor at an inner edge of collinear crack is larger than one at outer edge and increases with decreasing the distance of each crack.PART [2] : A study of crack propagation paths in FGPs under thermal load by Finite Element Methods (FEM).(1) We could develop a program with automatically production of mesh of FEM.(2) For the single crack growth simulation, the straight or curved cracks are obtained for several conditions of the thermal shock and the compositional profiles. Some cracks curve sharply and grow in the direction parallel to the surface. Such cracks cause delamination of the surface. The other cracks are arrested in the middle of the plate.(3) As two crack growths is one of the basic forms of the multiple thermal cracking, the interaction between the two cracks are discussed. The cracks grow in curve and away from each other, when the cracks exist in short distance. For spalling cracks that come close to each other from a long distance, the cracks curve in the direction normal to the surface as the crack tips come closer. Then the cracks are arrested in the middle of the plate.