Project: V-Notched Rail Shear
School: University of Utah
Location: Salt Lake City
Director: Dan Adams
In the process of developing a new composite product, you must often consider the shear stiffness of the material (its elastic property) and the shear strength (how much shear stress a material can take). University of Utah Professor Dan Adams has worked on tests specifically designed to establish the shear properties of composites. His newest test method, the V-Notched Rail Shear test method was recently standardized by ASTM International, which develops international standards for materials, products, systems and services, as ASTM D 7078.
Specifically, Adams has addressed two deficiencies in the existing Iosipescu shear test method used to determine the shear properties of composites. “The test uses a small specimen that doesn’t contain enough fiber tows for common woven or braided composites,” he says. The existing test method was not capable of introducing enough load into the specimen through its edges to fail a high shear strength composite laminate. So, we set out to address those two deficiencies.”
Adams and his students chose to retain the double V-notched specimen geometry of the Iosipescu test method, but change the geometry outside of the central test region to allow for face-loading of the specimen. “Putting the notches in the test section does a really nice job of creating a more uniform state of shear stress,” said Adams.
The group found a lot of interest both from commercial aviation, general aviation, and military programs,” said Adams. “We also found an unexpected group in the shipbuilding industry that was interested. When the marine industry constructs large vessels, they often use woven composite materials that have large fiber tows and need a larger shear specimen. They found that the method we developed addressed that need.”