High Strain Composite Testing Methodologies

An innovative loading stage design based on the principle of eccentric loading is proposed for mechanical testing of thin composites to impart precise mixtures uniaxial and bending stresses. In contrast to alternative designs, the mechanism is fully compatible with advanced experimental techniques such as three-dimensional digital image correlation (3D-DIC) strain measurements and in situ micro X-ray computed tomography (XCT) testing. Specific research is proposed to demonstrate the feasibility of this design and resolve scientific questions regarding the role of strain gradients on composite strength: First, constitutive modeling and analytical sensitivity studies will model the prototype designs performance. Second, a set of full-size experiments will be performed to optimize the gripping mechanism, and 3D-DIC full-field strain measurements will validate the stress state within the composite. Third, we will demonstrate in situ XCT testing capability, and employ volumetric digital image correlation (V-DIC) to quantify and model the internal strain gradient and failure mechanisms. The PIs expertise in materials design and process validation, as well as the University of Virginias expertise in mechanical and microstructural characterization of composites will ensure the success of this project. We anticipate commercialization of the loading stage itself as well as associated expertise on mechanical testing of composites.