Jacob R. Grohs

On the Use of Pressure-Loaded Blister Tests to Characterize the Strength and Durability of Proton Exchange Membranes

The use of pressurized blister specimens to characterize the biaxial strength and durability of proton exchange membranes (PEMs) is proposed, simulating the biaxial stress states that are induced within constrained membranes of operating PEM fuel cells. PEM fuel cell stacks consist of layered structures containing the catalyzed PEMs that are surrounded by gas diffusion media and clamped between bipolar plates. The surfaces of the bipolar plates are typically grooved with flow channels to facilitate distribution of the reactant gases and water by-product. The channels are often on the order of a few millimeters across, leaving the sandwiched layers tightly constrained by the remaining lands of the bipolar plates, preventing in-plane strains. The hydrophilic PEMs expand and contract significantly as the internal humidity, and to a lesser extent, temperature varies during fuel cell operation. These dimensional changes induce a significant biaxial stress state within the confined membranes that are believed to contribute to pinhole formation and membrane failure. Pressurized blister tests offer a number of advantages for evaluating the biaxial strength to bursting or to detectable leaking. Results are presented for samples of three commercial membranes that were tested at 80°C and subjected to a pressure that was ramped to burst. The bursting pressures exhibit significant time dependence that is consistent with failure of viscoelastic materials. Rupture stresses, estimated with the classic Hencky’s solution for pressurized membranes in conjunction with a quasielastic estimation, are shown to be quite consistent for a range of blister diameters tested. The technique shows considerable promise not only for measuring biaxial burst strength but also for measuring constitutive properties, creep to rupture, and cyclic fatigue damage. Because the tests are easily amenable to leak detection, pressurized blister tests offer the potential for characterizing localized damage events that would not be detectable in more commonly used uniaxial strength tests. As such, this specimen configuration is expected to become a useful tool in characterizing mechanical integrity of proton exchange membranes.

Service, Dialogue, and Reflection as Foundational Elements in a Living Learning Community

Abstract As part of a broad initiative to create a portfolio of robust living learning communities at Virginia Tech, the SERVE LLC was established in 2009 to offer students meaningful community-engaged learning experiences. The program connects students with a commitment to social justice in an environment that promotes critical dialogue and reflection. This article describes efforts to establish the program and highlights some of its most effective practices.

Carefully, Thoughtfully Exploring the "I" in Reciprocity: Practitioner Reflections in Striving for Self-Authoring Student-Citizens

Abstract The author explores some of the more elusive aims of civic engagement and the tension from the role of self in context of community. Thoughtful reclamation of the role for self can be a catalyst for different “aha” moments in terms of self-authorship, multicultural understanding, and sustainable and effective change agency. This commentary seeks to shine a light on these ideas as a way of generating and focusing a conversation with the potential to transform practice.

Leveraging local data for reflective teaching in large classes

Abstract In this paper, we discuss efforts to collect and analyse data at the local level to prompt reflective teaching in large foundational engineering courses. The work is in direct response to the growing demands and constraints of teaching in large classes that compromise the educational environment. We feel that motivated improvement-seeking institutions and academics must strive to innovate within the constraints. To do this, we argue that locally rooted data analytics offers unique opportunities to infuse data back into decision-making processes. As a demonstration of our claims, we discuss summaries of our team’s efforts within large foundational engineering mechanics courses at a public research institution in the United States. Specifically, we report on work to examine (1) Student Engagement and Performance (analysis of student surveys and course grades); (2) Performance Patterns Not Performance Points (analysis of course-level data); and (3) Understanding Courses in Context (analysis of existing institutional data).

Civic Attitudes and the Undergraduate Experience

The assertion that higher education has a collective responsibility to prepare graduates for effective community engagement has gained significant national and international support; yet, many research universities, facing competing priorities and limited resources, have not articulated civic learning objectives for undergraduates. Using survey data from 3453 graduating seniors at Virginia Polytechnic Institute and State University (Virginia Tech), a large public research university, the purpose of this study was to investigate associations between participation in undergraduate experiences and civic attitudes. The study finds significant associations between these experiences (living-learning communities, volunteering, and service learning) and civic attitudes (social justice, diversity, and community orientation). The study suggests that research universities should not assume that disconnected programs will lead to significant civic learning gains for students; instead, explicit intentional integration of civic learning into the undergraduate experience at research universities can lead to greater civic outcomes.