TOP STORY
New Research Could Lead to Better Energy-Absorption Materials
By Diane Kukich
Research being conducted by Professor of Mechanical Engineering Michael H. Santare has the potential to lead to better energy-absorbing materials. The work, which focuses on stress wave prediction and management in functionally graded materials, is being carried out under the ARL-CMT program in collaboration with ARL Research Physicist George Gazonas. Other members of the research team have included postdoc Priya Thamburaj, now on the faculty at Armstrong Atlantic University , and current Ph.D. candidate Dan Su. Santare has long been interested in fracture mechanics, most recently in functionally graded materials (FGMs), which feature continuously graded properties through gradual changes in microstructure. In contrast, traditional protective materials consist of discrete layers of homogeneous materials with different properties. |
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“I became interested in the question ‘What about stress wave propagation in these materials?'” says Santare. “Would it be possible to exploit this phenomenon and develop a material to transfer impact energy in a desired way through microstructural design?”
He explains that one of the primary mechanisms by which materials absorb energy is through damage. “So we began to look at how energy could be managed in these materials through the way damage grows and changes the material,” he says.
“After impact, what we have is not only a material that is functionally graded but also one whose properties have been altered through damage. This work has required us to combine what we know about damage with what we know about grading in order to maximize the protective properties of these complex materials.”
The novel aspect of the work Santare and his research team are conducting is their ability to look at anisotropic, nonhomogeneous damage fields. Other work has been limited to scenarios in which the damage is either perfectly aligned or completely random.
The damage Santare is investigating is primarily in the form of microcracks, which form a distributed array. None of the cracks is critical in itself, but as an array, the tiny cracks change the mechanical properties of the material. In particular, compressive and tensile waves travel through arrays of microcracks in very different ways and have very different effects.
“With a compressive wave, the cracks close and the wave passes through the material,” Santare explains. “In contrast, with a tensile wave, the cracks open and there is a complex interaction between the cracks and the stress wave.”
Santare's current goal is to create a single model to predict energy transmission through a damaged material subjected to arbitrary wave loading, including tensile, compressive, and/or shear waves.
“Having a solid understanding of these waves and their movement through the material, in terms of both direction and velocity, will enable tailored design of energy-absorbing materials for specific applications,” Santare says.
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Numerical simulation of wave propagation in microcrack-damaged media. The figure shows that the compressive wave is much faster than the tensile wave. The scattering due to the cracks causes the “diffusion-like” behavior in the tensile loading, but has very little effect on the compressive wave.
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OTHER NEWS
Two SAMPE-UD Students Win Prizes in Student Symposium
At the 51st International SAMPE Symposium and Exhibition in Long Beach, CA, Solange Amouroux and Mike Fuqua, both SAMPE-UD students, won awards in the student competitions.
Solange Amouroux, a PhD candidate working at CCM, took first place in the Ph.D. category of the SAMPE Graduate/Senior Student Competition. Solange's participation began with the local competition through the Baltimore/Washington chapter of SAMPE in February. As a result, Solange was selected as a finalist in the national student symposium, and SAMPE sponsored her trip to participate in the 51st International SAMPE Symposium and Exhibition in California .
Each finalist submitted a technical paper for the final stage of the competition. Solange's paper, "Membrane-based VARTM: Membrane and Resin Interactions," was judged on technical content, originality, significance of the research, and presentation. As the winner, Solange will receive a check for $1,000. Jack Gillespie is Solange Amouroux's advisor in research on membrane-based VARTM processing. Solange has served as the treasurer of the SAMPE-UD student chapter since 2004 and she organizes the CCM Spring Research Reviews, sponsored by SAMPE. She also participates in the manufacturing trainings held at CCM for industrial consortium members.
Also at the 51st International SAMPE Symposium and Exhibition, Mike Fuqua won second place in the SAMPE Undergraduate competition and a check for $400. In this national competition, students are asked to fill out an application, submit a reference from their Research Advisor and provide official transcripts for their entire college education. Mike began working at CCM the summer of his freshman year; he then continued to participate in CCM activities, mainly focusing on processing issues. Currently, he is finishing his senior thesis on an improved version of the VARTM process, under Dr. Glancey's supervision. Fuqua is going to graduate school next year in North Dakota .
EMPLOYMENT OPPORTUNITIES
Job Opening: Materials Engineer
2Phase Techologies, Inc., Santa Clara, CA
Primary Skill Category: Materials R&D
Qualifications: Ph.D. in Materials Engineering or closely related discipline from an ABET-accredited university, or M.S. with 1-4 years R&D experience
Work includes research and development of materials and processes to implement and advance the capabilities of reconfigurable tooling systems for composites and plastics manufacture and repair.
For details about this and other employment opportunities, please go to www.ccm.udel.edu/Opportunities/jobs.html
CONSORTIUM
CCM would like to thank our many consortium members for continuing to participate in consortium activities. To learn more about our Industry-University Consortium, please go to http://www.ccm.udel.edu/Consortium/members.html .
NEW PUBLICATIONS
Conference Proceedings
Lim, A. S., B. A. Gama, and J. W. Gillespie, Jr., “High Strain Rate Compression-Shear Behavior of a Shear-Thickening Fluid (STF),” SAMPE 2006: Creating New Opportunities for the World Economy, Long Beach, CA, April 30 – May 4, 2006.
Zhang, Y., S. Luo, S. Lopatnikov, D. Heider, J. W. Gillespie, Jr., “Analytical and Finite Element Model of Vacuum Bag Deformation in Vacuum Assisted Resin Transfer Molding (VARTM) Process,” SAMPE 2006: Creating New Opportunities for the World Economy, Long Beach, CA, April 30 – May 4, 2006.
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