The goal of this project was to continue work that started in the summer of 2002 on small scale testing of tire rubber compounds. The previous work used a sandwich beam geometry and dynamic mechanical analysis to evaluate the viscoelastic properties of tire rubber and the effects of aging on those properties. The beam was loaded in a three-point configuration. The results of the work were consistent with theories in place.

The goal of the current project is to create a test that will show when the rubber slips using a sandwich beam geometry. The rubber was sandwiched between two aluminum plates and loaded in a three-point configuration. The aluminum surface was pretty smooth and uniform. The rubber was not treated in any way. All tests were done at room temperature. Three different plate thickness (1/8'', ¼'' and ½'') and two rubber thickness (1/8'' and 1/16'') were used. None of the tests showed any slip of the rubber relative to the plates. The loads calculated using classic beam theory were in the range of 30 to 250 psi. These shearing stresses should be more than enough to induce slip (as most tires will slip in the region of 25 to 35 psi), so the classical theories must be wrong. A different model must be used to correctly describe the behavior of the plate/rubber interface. A model was not found during the span of this project that would describe the behavior of the beam. As work continues on small-scale tire testing, a model will need to be found or developed.

The author would like to thank the Army Research Office and the National Science Foundation for the funding of this project. The author would also like to thank Dr. Donald Radford, director of the Composite Materials, Manufacture and Structures Laboratory for his guidance and support during this project, and the graduate students, Todd Harper and Niraj Pansare, for their help along the way.

Steve Brandl
Email: sbrandl@engr.colostate.edu