Static and dynamic constitutive behavior and fracture of particulate composites
An experimental and analytical study has been conducted to investigate the static and dynamic constitutive behaviors and fracture of homogeneous and functionally graded particulate composite materials. In the first part of the study, fabrication and static and dynamic characterization of lightweight homogeneous polyurethane-cenosphere particulate composite was discussed. A predictive model to estimate the fracture toughness of the composite was developed. The dynamic constitutive behavior of the composite in compression was investigated using the split Hopkinson pressure bar (SHPB) technique in conjunction with high-speed photography. Results indicated that the quasi-static stiffness, both in tension and compression, and the quasi-static fracture toughness of the composite increased with addition of cenospheres. The high strain rate constitutive behavior of 100% polyurethane showed monotonic stiffening where as the composite at higher cenosphere volume fractions (40%) exhibited a stiffening-softening-stiffening behavior. ^ In the second part of the study, static and dynamic fracture of functionally gradient materials was discussed. Under static fracture, stress fields for a crack inclined to the direction of property gradation in functionally graded materials (FGMs) were obtained through an asymptotic analysis coupled with Westergaard's stress function approach. The elastic modulus of the FGM was assumed to vary exponentially along the gradation direction. ^ An experimental study using CGS in reflection has been performed to determine quasi-static fracture parameters for cracks at four different angles to the property gradation. Elasto-static finite element analysis was also performed and the experimental results were compared with those obtained from numerical method. The results indicated that mode-I and mode-II stress intensity factors increase as the load increase for all gradation angles. The synthetic contours generated using numerical results matched well with experimentally obtained fringes. ^ In case of dynamic fracture of FGMs, a generalized elastic solution for an arbitrarily propagating crack in Functionally Gradient Materials (FGMs) was obtained through an asymptotic analysis. The shear modulus and mass density of the FGM are assumed to vary exponentially along the gradation direction. Using this asymptotic solution, contours of constant out of plane displacement were generated. ^
Vijaya Bhaskar Chalivendra,
"Static and dynamic constitutive behavior and fracture of particulate composites"
Dissertations and Master's Theses (Campus Access).