Test Methods for the Determination of Anisotropic Compliances in 3D Woven Preforms for Ablative TPS

Based on the recent success of the Mars Exploration Program and the Mars Science Laboratory mission, NASA has a desire to expand on the technology developed under each effort in order to increase future mission capabilities, namely an increase in payload capacity for entry to Mars, Venus and other Outer-Planets. Such a goal requires an innovative solution to the vehicle's entry, decent and landing system (EDL). In order to address this goal,NASA has recently invested in the development of low ballistic coefficient aeroshell technology concepts which typically consist of a flexible 3D woven carbon cloth that can be stowed during flight and deployed to serve as a semi-rigid aeroshell on atmospheric entry. The ability of individual groups of fibers within yarn bundles to undulate in multiple orientations relative to the major axis of the yarn bundle results in full anisotropy for the 3D woven preforms. In addition to adding more complexity to the accompanying analytical models, the testing of such materials is also complicated as compared to isotropic and transversely orthotropic materials. Within the proposed Phase I effort, Materials Research & Design will develop test methods for the materials characterization of a hybrid, woven 3D fabric for use in a flexible TPS application. The program willinvolve analytical, fabrication and experimental tasks to achieve the overall program goal of maturing technologies for advanced EDL systems. A few select tests will be performed at Southern Research Institute with strain data being captured for use in the anisotropic compliance matrix calculations. Finite element simulations, using a homogeneous representation of the anisotropic material, will be used to simulate each test and aide in the design of test specimens sufficient to generate measurable strain levels while simultaneously allowing the anisotropic material to deform naturally.