A NOVEL PRE-COMPRESSION KOLSKY TENSION BAR TECHNIQUE FOR BRITTLE MATERIALS

Brittle materials such as concrete are used ubiquitously in structural engineering due to their ability to withstand enormous compressive loads. When these materials undergo a high speed impact, however, the reflection of the resultant stress wave can cause moments of tensile stress. Currently, little reliable data is available about brittle materials' tensile stress and strain information at high strain rates. This is due to the low tensile strength causing fracture before dynamic stress equilibrium can be established across the sample. nou Systems, Sandia National Labs, and Auburn University have joined together to provide a solution for this challenge by applying a pre-compressive load to Kolsky bar tensile test samples through utilizing the thermal expansion of the materials composing the Kolsky bar itself. This pre-compressive load will place the sample in a state of compression, or “negative strain”, that will enable the device to undergo a longer period of "positive" constant strain rate before sample fracture. The strategy of utilizing Kolsky bar materials will allow for existing Kolsky tension bars to be retrofitted with a the capability of applying a pre-compressive stress with very little modification to existing setups. In Phase I of this STTR, we will complete the component design, analyses, and testing needed to finalize critical details for prototype assembly, characterization, and delivery in Phase II.