Objectives and approaches: It is well known that macro scale responses of polymer-based particulate composites are controlled by micro scale mechanics. Hence bridging macro and micro scales is central to the design of next generation materials with micron and sub-micron size fillers. Recent investigations on filled polymers have produced counterintuitive fracture toughness results when filler characteristics such as the size and filler-matrix adhesion strengths are varied. This has motivated the proposed in depth study on how a propagating crack interacts with embedded inclusions under low and high rates of loading. Stiff inclusions in a relatively compliant matrix will be targeted in this research using experimental and computational methods. The experimental work will include aspects of macro (optical interferometry, high-speed imaging) and micro (microscopy, surface profilers) measurements of the fracture process. Boundary element analyses of crack-inclusion interaction problems will be addressed computationally. The measurements and computations will be utilized synergistically for identifying new failure mechanisms as well as validating the prevailing ones.
Broader societal impact: Polymer-based particulate composites are found in a wide range of applications as biocements, electrically conducting adhesives, syntactic structural foams, scratch resistant coatings, solid propellants, nanocomposites, to name a few. Understanding the mechanical characteristics in general and failure properties in particular is central to the safety and reliability of structural systems involving these materials. The proposed research is aimed towards addressing the above mentioned issues through collaboration between researchers at Auburn University and Univ of S. Alabama. During this project, students will be trained in materials processing, mechanical and optical characterization of materials as well as numerical modeling. Students belonging to underrepresented groups will be encouraged to participate in the project. Research outcome will be disseminated through archival journals, presentations at focused symposia, and world-wide-web.
