Faculty — Structures and Materials
Structures and Materials Lab Facilities
- W. Chen
Dr. Chen's research activities mainly involve the development of novel dynamic material characterization techniques and the determination of dynamic responses of engineering materials at high loading rates. He built dynamic material characterization laboratories at California Institute of Technology, University of Arizona, and Purdue University. He also assisted the development of such laboratories at Sandia National Laboratories in Albuquerque, NM and Livermore, CA; Army Research Laboratory in Aberdeen Proving Ground, MD; U.S. Army Waterway Experiment Station in Vicksburg, MS; National Institute of Standard and Technology in Gaithersburg MD; and a number of university and industrial laboratories. The techniques he developed are focused on ensuring valid testing conditions during dynamic experiments to obtain accurate material properties at high rates of loading. These techniques, summarized in over 15 journal articles, have been well accepted in the research community. Two of top five, four of top ten "most cited papers of Experimental Mechanics" are from Dr. Chen's group.
Using the novel techniques, Dr. Chen and his students have obtained accurate and reliable material behavior at high rates for soft rubbers, glassy polymers, polymeric foams, gelatins, glass/epoxy composites, soy-bean based clay nanocomposites, biological tissues (muscles, skins, bones), shape memory alloys, high-strength steels, geomaterial, masonry materials, textile materials, and armor ceramics. For each class of the materials under dynamic tension, compression, or multiaxial compression, at various temperatures, his group examined the valid dynamic testing conditions to obtain valid experimental results. Microstructural characterization was carried on some of the materials. Based on the experimental results and microstructural observations, material constitutive models were developed to describe the recorded material behavior. Over forty journal articles have been published based on the results from these research programs.
The research accomplishments demonstrate that Dr. Chen has established himself with unique contributions in the field of experimental solid mechanics. He has developed an independent and well funded research program investigating the dynamic mechanical behavior of materials and the necessary experimental techniques, and has established a national and international reputation in his field.- W. A. Crossley
Professor Crossley's current research interests are in the area of design methodologies and multidisciplinary design optimization, with emphasis for aerospace engineering systems design problems.
- J. F. Doyle
The main research area is Experimental Mechanics with an emphasis on the development of a new methodology for analyzing impact and wave propagation in complicated structures with the goal of being able to extract the complete description of the wave and the dynamic system from limited experimental data. Special emphasis is placed on solving inverse problems by integrating experimental methods with computations methods (primarily Finite Element based methods).
This research is based on the assertion that, in modern analyses, constructing the model is constructing the solution—that the model is the solution. But all model representations of real structures must be incomplete; after all, we cannot be completely aware of every material property and every aspect of the loading and every condition of the environment, for any particular structure. Therefore, as a corollary to the assertion, we posit that a very important role of modern experimental stress analysis and experimental mechanics in general is to aid in completing the construction of the model.
That the model is the focal point of modern Experimental Mechanics has a number of significant implications. First, collecting data can never be an end in itself. Invariably, the data will be used to infer indirectly (or inversely) something unknown about the system. Typically, they are situations where only some aspects of the system are known (geometry, material properties, for example) while other aspects are unknown (loads, boundary conditions, behavior of a nonlinear joint, for example) and we attempt to use measurements to determine the unknowns; these are partially specified problems. The difficulty with partially specified problems is that, far from having no solution, they have a great many solutions. The research question revolves around what supplementary information to use and how to incorporate it in the solution procedure. Which brings us to the second implication. The engineering point to be made is that every experiment or every experimental analysis is ultimately incomplete, there will always be some unknowns and at some stage the question of coping with missing information must be addressed. This is not a question of collecting more data, "re-do the experiment," or design a better experiment. This is not a statistical issue where if the experiment is repeated enough times, the uncertainty is removed or characterized. We are talking about experimental problems which inherently are missing enough information for a direct solution.
These ideas with the accompanying algorithms and examples are presented in the book:
- J.F. Doyle, Modern Experimental Stress Analysis: completing the solution of partially specified problems, Wiley & Sons, UK, 2004.
A final point: current technologies are exploring the possibility of using nanostructures in a variety of applications. These do not lend themselves to traditional methods of experimentation; the inverse methods being developed here offer great potential to overcome the challenges.
- R. Pipes
- Dr. Pipes' graduate students work in composites manufacturing simulation focuses on the influence of manufacturing processes on the development of composites microstructure and the resulting implications upon structural performance. Two primary manufacturing processes are the subject of the majority of the scholarship underway and these include composites additive manufacturing (cAM) through fused filament fabrication and discontinuous prepreg platelet composites. For cAM, the research is directed at the prediction of the free-surface flow of fiber-reinforced polymer extrudates and the multi-physics phenomena that determine extrudate-substrate adhesion, shrinkage deformation, mechanical and transport properties and performance of the printed geometry. The discontinuous prepreg platelet studies examine the rheology of these highly anisotropic systems to determine fiber orientation distribution within a molded geometry, micro-CAT scan methods for determination of fiber orientation and prediction of the strength properties of structural elements molded from these materials systems.
- M. Sangid
Professor Sangid’s research activities combine knowledge of materials science, solid mechanics, and advanced manufacturing to solve complex problems in materials behavior and processing. His research group employs physics-based computational modeling and design tools, which are experimentally validated and verified. The goal of this work is to improve our understanding and our tools for designing, processing, and lifing materials through simulation-based modeling of the microstructural defects. His research specifically focuses on (micro)structure to performance modeling, via the use of atomistic simulations to inform multi-scale models for plasticity, fatigue, and fracture of metallic alloys and high temperature composites. Both material systems have direct applications in Aerospace Engineering. Many times, it is necessary to start at the atomistic level to gain a quantifiable understanding of the deformation pathways and failure mechanisms at component scales. Further, there is also an experimental component to his research as he does advanced materials testing and characterization including digital image correlation, advanced microscopy, and high-energy x-ray diffraction. Thus, the most advanced characterization and interrogation methods are exercised at each scale to verify and validate model predictions, including four dimensional mapping of ‘defect’ features, strain fields, and complex stress states within the material.
Professor Sangid is the principal director of the Advanced Computational Materials and Experimental Evaluation (ACME) Laboratory. The ACME group’s philosophy is to simultaneously address fundamental research needs and implement this knowledge into integrated models that can directly aid in and transform our design methodologies providing pragmatic engineering solutions. The overarching goal and uniqueness of the ACME group’s modeling strategy is to avoid fitting parameters prevalent in classical engineering models, while providing a general framework, which allows: (1) Easy integration and modification of software, (2) Uncertainty quantification and probabilistic lifing, and (3) Pragmatic tools to answer production questions.
- V. Tomar
- Interfacial Multiphysics Lab is focused on advancing analytical technologies such as Mechanical Raman Spectroscopy (MRS), an analytical experimental method developed by lab members (US Patent 9,778,194, Review of Scientific Instruments 85, 013902 (2014)) and Smart Battery Management Systems (another US Patent from lab: US11658350B2) to solve important extreme environment operational problems with specific projects currently focusing on; 1. Non-equilibrium Phenomenon in Matter: Application of Nanosecond Multipoint Raman Spectroscopy and data science to understand/describe shock as well as low velocity fracture/sensitivity to damage. Use of such knowledge in domains such as Physiology, Hypersonics, Anti-Shock Designs, Space Solutions, Additive Manufacturing, etc. 2. Autonomy Energy Intelligence: Use of data science for combined edge-cloud solutions for deploying high voltage batteries in sensitive applications, emphasizing extreme events such as nail puncture-high voltage shock-rapid temperature events, etc. Use of such knowledge for Physical AI Solutions for Autonomy, Artificial General Intelligence, Large Scale Autonomous Manufacturing etc Lab Director, Prof. Tomar started his career as an assistant professor in January 2006 after graduating from Georgia Tech with PhD in Mechanical Engineering in December 2005. He was promoted to full professor in 2016 at Purdue University. Lab has graduated 17 PhDs, 27 MS-Thesis students, and multiple non-thesis/undergrad special topic research project students. Lab has published over 400 publications, filed 11 research patents/disclosures (awarded 6 patents), written 2 published books, and edited 5 research volumes. The lab has been part of multiple externally funded projects from Industry, the Office of Naval Research (ONR), the Naval Surface Warfare Center, the National Science Foundation (NSF), the Department of Energy (DoE), ARMY, and Air Force Office of Scientific Research (AFoSR). Lab excellence in research has been recognized by several awards including the VAJRA award from Govt of India, the AFoSR Young Investigator Award for high-temperature interface thermomechanics, the American Society of Mechanical Engineers (ASME) Orr Early Career Award for excellence in fracture and fatigue, The Mineral, Metal, and Materials Societies (TMS) early career faculty fellow-honorable mention award for materials research, inaugural Elsevier Material Science and Engineering journals Early Career Young Researcher Award for Interface Mechanics, Purdue Seeds for Success Awards (2017, 2018, 2020), Purdue CT Sun Research award, Purdue University Faculty Scholar Award, and multiple other best paper awards. For his contribution to the profession, Dr. Tomar was elected an ASME Fellow in 2016 and an American Institute of Aeronautics and Astronautics (AIAA) Associate Fellow in 2015. He has been bestowed with multiple mentorship and teaching awards including the Indiana LSAMP Outstanding Mentor Award, Purdue School of Aeronautics Best Undergraduate Teacher Gustafson award etc. He has organized numerous conferences as track chair and conference co-organizer with various Editor-in-Chief and Associate Editor positions at reputed journals. Lab student members have won multiple research and service awards at the undergraduate and graduate level including the Mitchell Scholarship award to Milad Alucozai which is first ever awarded in Purdue undergraduate education history, the NASA RASC-AL award to an undergraduate team, the NSF best poster award with grad student Ming Gan, Best paper awards at TMS with Bing Li and Abhijeet Dhiman, Chorafus foundation best PhD dissertation finalist to Ming Gan, College of Engineering outstanding service award to Devendra Verma, and numerous other student awards such as Blissland Dissertation Fellowship, Purdue's Nominee for external Best Master's Thesis competitions, multiple Lynn Fellowships, and finally numerous student conference travel awards sponsored by organizations across the world. Students after graduation have enjoyed successful careers in academia US government agencies national labs and industry. Several lab alumni have either tenured or tenure-track faculty positions in universities in the USA, Mexico, India, China, and S Korea.