Title: Mechanism-based multi-scale models for damage and failure in heterogeneous materials

Abstract: A large variety of modern engineering materials such as polymers and their composites (unidirectional, textile, nanocomposites) have a heterogeneous microstructure. As a result, their failure behavior under multi-axial stresses is highly complex, consisting of multiple simultaneous meso-scale damage mechanisms. Moreover, the heterogeneous microstructure also makes the fracturing distinct quasi-brittle character (neither fully brittle nor fully ductile). This has important implications on structural behavior, especially in terms of size effects in strength and fracture toughness. Since structural designs often rely on numerical modeling, an accurate prediction of load-bearing capacities and energy dissipation during these failures is essential. This talk will focus on the class of semi-multiscale constitutive models called the microplane models (pioneered at Northwestern), which effectively address this challenge. These models have a dual-scale architecture, and can reproduce complex macro-scale behaviors via simple, intuitive formulation of meso-scale damage mechanisms. They also provide a physically sound basis to homogenize the meso-scale damage to predict the macro-scale failure growth and structural size effects. They are thus an effective strategy for multi-mechanism failures in heterogeneous materials. First, we will introduce the quintessential spherical microplane model, first developed for concrete, and applicable in general to isotropic materials. We will present its application to the failure of brittle-plastic polymers and demonstrate its abilities to capture complex aspects such as tension-compression asymmetry and pressure sensitivity. Next, we will introduce the cylindrical microplane model, which applies to unidirectionally reinforced polymer composites, which are transversely isotropic. We will present a successful application of this model to compression induced kink band failures. Following that we will introduce the microplane triad model, which applies to textile composites, which are orthotropic and have additional complexities due to yarn undulations. We will demonstrate its successful application to prediction of ballistic impact of woven composite lamina. Lastly, we will discuss the challenges of applying these models to real world applications and directions for future work.

Bio- Prof. Kedar Kirane is an associate professor of Mechanical Engineering at Stony Brook University, New York. His research focuses on characterizing, understanding, and predicting the fracturing and scaling behavior of various conventional and advanced heterogeneous materials. These include brittle materials, fiber reinforced composites, polymers, nanocomposites, geological and cementitious materials, and soft materials. His research combines experimental, computational, and theoretical approaches. The overarching goal is to develop reliable predictive capabilities and sound scientific bases for safe designs in various engineering applications. Prof. Kirane obtained his Ph.D. in 2014 from Northwestern University and joined the Mechanical Engineering faculty at Stony Brook University in Sept 2017. He also holds an M.S. degree from the Ohio State University (2007) and a B.S from the University of Pune, India (2004), both in mechanical engineering. Prior to joining Stony Brook, Prof. Kirane worked in industry, as a finite element analyst at Goodyear Tire & Rubber Co and later as a senior research engineer at ExxonMobil Corp. His research is supported by DOD ARO, DOD ONR, NSF NRT, and ASME. He is the recipient of the 2020 Orr Early Career Award by ASME's Materials Division, the 2019 DOD ARO Young Investigator Award, and the 2018 Haythornthwaite Research Initiation Grant by ASME's Applied Mechanics Division.