Finite element based micromechanical methods are being developed to understand the fracture behavior of functionally graded foams. The method uses a micromechanical model in conjunction with a macro-mechanical model in order to relate the stress intensity factor to the stresses in the struts of the foam. The stress intensity factor was evaluated using two different methods. The fracture toughness is evaluated for various crack positions and crack lengths within the functionally graded foam. Then the relationship between the fracture toughness of foams and the local density at the crack tip is studied. The fracture toughness of homogeneous foams under uniform traction along the crack face is investigated in order to analyze the local effects of crack face traction and to observe the effect of crack length on the fracture toughness. The results indicate that smaller cracks seem to have higher fracture toughness. Since metal and ceramic foams are expected to be used as load-carrying thermal protection systems, the behavior of homogenous foams and functionally graded foams under thermal loading are investigated.
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