Evaluation of crack tip fields and stress intensity factors in functionally graded elastic materials: Cracks parallel to elastic gradient

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摘要：

Particulate functionally graded materials (FGM) made of glass-filled epoxy with edge cracks parallel to the direction of the elastic gradient and subjected to pure bending have been studied. Crack tip measurements are used to examine continuum models for FGMs by treating the material as isotropic and nonhomogeneous at macroscales. Situations where cracks are located on the compliant and the stiff sides of the beams are separately examined by mapping crack tip deformations using optical interferometry. Comparative experiments on homogeneous compositions corresponding to identical elastic properties of the crack tip region in the FGM are also undertaken. A methodology for extracting fracture parameters in FGMs based on locally homogeneous material descriptions is advanced. Companion finite element models are used to aid the development of fringe analysis procedures and to provide a direct comparison to the optical measurements. Stress intensity factors in FGMs are compared to each other and to their homogeneous counterparts. Optical measurements near quasi-statically growing cracks in FGMs have been undertaken, and crack growth resistance behavior is explained using crack initiation toughness variation as a function of filler volume fraction in homogeneous sheets.

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Theoretical or Mathematical, Experimental/ crack-edge stress field analysis filled polymers finite element analysis fracture toughness functionally graded materials light interferometry Young's modulus/ particulate functionally graded materials glass-filled epoxy composite edge cracks parallel elastic gradient functionally graded elastic materials crack tip fields stress intensity factors continuum models isotropic nonhomogeneous stiff sides beams crack tip deformations optical interferometry homogeneous compositions elastic properties crack tip region fracture parameters locally homogeneous material descriptions finite element models fringe analysis procedures optical measurements quasi-statically growing cracks crack growth resistance behavior crack initiation toughness filler volume fraction homogeneous sheets solid spherical glass inclusions/ A8140N Fatigue, embrittlement, and fracture A6220D Elasticity, elastic constants A8140J Elasticity and anelasticity A6220M Fatigue