Experimental study on fracture behavior of linear functionally gradient materials

Static and dynamic fracture behaviors of functionallygradient materials (FGMs) with linear variation of the shear modulus areexperimentally studied with caustics method and high speed photographytechnique, and numerically investigated through finite element method (FEM).Firstly the caustics equations relative to the caustics principles and theelastic solution at mode I crack in FGMs are deduced through an iterativenumerical method. Three kinds of specimens with different variation of shearmodulus are synthesized by a gravity-assisted vertical casting process. Thenthree-point-bending experiments are performed and the caustics patterns areshot through CCD and high speed photography equipment. The static anddynamic stress intensity factors of FGMs specimens are obtained throughcaustics method. Finally, The experimental results are validated with thenumerical results to investigate the influences of the stiffness variationon the static and dynamic fracture characteristics.