An Integrated Computational-Experimental Approach to Three-dimensional Fracture in Polymer-Ceramic Composites

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Composite materials are used in spacecrafts, aircrafts, automobiles, and naval vessels for their unique property to provide high strength- and stiffness-to-weight ratios. They are also used in bioengineering and electronic devices; and concrete is a composite that is one of the most widely used materials today. Understanding their behavior is important to advance the design of these materials, as measures taken to further strengthen or stiffen them can sometimes yield counterintuitive or even counterproductive results. This award supports fundamental research on understanding the material properties of composites by examining the three-dimensional mechanics and failure evolution on the microstructural level. An integrated combination of experiments and simulations will be used to study their behavior, with a focus on polymer-ceramic composites. This project will answer fundamental questions about the competing mechanisms on the microscale that lead to the counterintuitive relations between microstructure and resulting composite properties. The new knowledge and tools will lead to advances in the design of composites, and significantly impact the broad range of applications in which these materials are used, thereby impacting national health, prosperity, and welfare; and securing the national defense. The outreach and educational activities in this project will broaden the participation of undergraduate and graduate students, particularly women and from other underrepresented groups, in STEM subjects through research in the PIs' labs. The outreach activities with visiting students from Africa also intends to inspire interest of African-American students in STEM subjects.A new computational approach called the continua-discontinua particle method (CDPM) is proposed which combines the strengths of traditional continuum-based methods in fundamental mechanics and mathematically grounded principles, with the strengths of discrete methods in simulating arbitrary complex three-dimensional fracture. The method allows the transition under failure from a meshfree particle discretization based on continuum mechanics, to that of a discrete fracture network similar to discrete particle methods. An approach using micro X-ray computed tomography (micro-CT) and an in-situ mechanical tester is proposed, which yields 3D full-field mechanical measurements. Other material characterization methods, such as tensile testing, nanoindentation, and scanning electron microscopy will also be employed to compliment the in-situ experiments. The experiments and simulations will be closely integrated to both formulate and validate the numerical models for prediction of composite stiffness, strength, and toughness of polymer-ceramic composites with varying filler morphology, as well as illuminate the underlying causes of the structure-property relationships in these materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.