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Published May 6, 2015 | Submitted
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Hydrostatic Tensile Fracture of a Polyurethane Elastomer

Abstract

The investigation of fracture of polymeric materials in hydrostatic tensile fields constitutes an avenue of approach to the study of fracture in more general three-dimensional environments. The advantages created by the symmetry of the stress field are considerable and, in one of the cases studied, facilitates a theoretical treatment that includes large deformations, which are characteristic of this class of materials. The analysis is developed through the concept of fracture originating from a flaw, which in this instance is taken to be a spherical cavity. Through the application of energy principles, a theoretical prediction of ultimate strength is made for hydrostatic tensile fields. Experiments were conducted to demonstrate the existence of such flaws and to evaluate the theory. Results of the tests on specimens containing both residual flaws and artificially inserted ones indicate a fundamental difference in behavior as contrasted with cracks. An explanation is given linking experimental results and theoretical predictions. It is based on the concept that a flaw "grows" in the material under load using the cavity as a nucleating point. Upon this hypothesis is built a theory of rupture in which planar cracks grow radially from the center of the cavity in the form of Saturn-ring cracks.

Additional Information

ARL 66-0029. Contract AF 33(615)-2217 Project 7063. This is a final report prepared by the Graduate Aeronautical Laboratories of the California Institute of Technology (GALCIT) for Aerospace Research Laboratories, Office of Aerospace Research, United States Air Force. The work was performed under Contract No. AF 33(615)-2217, Task 706302-N-3 of Project No. 7063. This report includes both analytical and experimental results obtained between 15 October 1964, and 15 November 1965, under the cognizance of the late Mr. Charles A. Davies, ARL Project Scientist. It is appropriate to acknowledge the help of Mr. William Rae, lab technician and Marvin Jessey, electronics lab supervisor, for help in design, preparation and conduction of laboratory experiments. Furthermore, it is a pleasure to express appreciation to Mrs. Sally Richards and Mrs. Elizabeth Fox, who typed the manuscripts. The notes and data for this report are recorded in GALCIT File No. SM 65-25. This report is distributed to the Chemical Propulsion Mailing List of 1965.

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Created:
August 19, 2023
Modified:
October 23, 2023