Session: 12-15-01: Dynamic Failure of Materials & Structures

Paper Number: 99364

99364 - Mixed Mode Dynamic Fracture Behavior of Soda Lime Glass 

Structures often fail during service due to combined tensile and shear loads. Under such conditions, mixed mode fracture is the likely outcome when brittle materials are involved and hence understanding the material behavior under those conditions is critical. In this work, the fracture behavior of highly brittle soda lime silicate glass plates is investigated under mixed mode loading conditions. Although soda lime glass is a widely used material in many structural applications, its fracture behavior under mixed mode, stress wave dominant conditions, is yet to be investigated and understood. Furthermore, most previous mixed mode dynamic fracture investigations to date have been limited to brittle polymers and composites due to the lack of a suitable optical technique capable of both spatial and temporal sensitivity requirements necessary for such an investigation until recently. In this context, the dynamic mixed mode fracture of soda lime glass was experimentally investigated during this research using a relatively new full field, non contact, vision based optical method called Digital Gradient Sensing (or DGS) by using it in conjunction with ultrahigh speed photography (one million frames per second). Single edge notched specimens were subjected to reverse impact loading using a modified Hopkinson pressure bar. The specimens were eccentrically loaded at different offset distances relative to the initial notch to achieve a wide range of mode mixities, from mode I to nearly mode II condition, at crack initiation. Two orthogonal angular deflections of the light rays proportional to the respective stress gradients were optically measured. Both mode I and II stress intensity factor histories prior to, at crack initiation and during crack growth were evaluated by performing over deterministic least squares analysis of optically measured instantaneous full field data. Using the critical stress intensity factors at different crack initiation events, a fracture envelope for soda lime glass encompassing various mode mixities was developed and compared with predictions from Maximum Tensile Stress (MTS) and Strain Energy Density (SED) criteria. A parabolic fit of critical stress intensity factor data seems to describe the behavior better than the two popular criteria. From the fractured samples, kink angles were also measured and compared with the two established criteria and both seem to predict the kink angles rather well. Interestingly, within the experimental errors the critical effective stress intensity factors seem independent of mode mixity for soda lime glass. This is unlike the mixed mode fracture response of many brittle polymers and composites.

Presenting Author: Hareesh Tippur Auburn University

Presenting Author Biography: McWane Endowed Chair Professor of Mechanical Engineering at Auburn University, AL.

Authors:

Hareesh Tippur Auburn University
Sivareddy Dondeti Auburn University