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IntroductionStructural polymers, being attractive from mechanical and chemical points of view, are susceptible to deterioration in the form of cracks. This leads to degradation of their mechanical properties and decreasing lifetime of such materials. Self-healing of mechanical properties of polymeric materials can be useful in a variety of applications.Here we elaborate on a self-healing approach in which special healing capsules are embedded in the polymer matrix (1-4). When a crack propagates it ruptures the capsules, healing glue leaks out into the crack, sealing, and "curing" the crack. This repairs the crack, and to some extent recovers mechanical integrity of the matrix. The major problem of this approach is the necessity of using a rather expensive catalyst, which in addition has a rather short lifetime. Another natural candidate for self-healing glue would be a two component epoxy (resin and hardener) encapsulated in separate capsules. Apart from relatively low cost and good availability of various epoxies, the advantage of using healing epoxy capsules within the epoxy matrix is the good compatibility between such healing glue and the matrix. As a result, higher adhesion strength and better repair effect might be expected. While the epoxy resin is relatively easy to encapsulate (3,4), there is a problem with doing that for the hardener. Recently, there was a proposal (3) to use a latent curing agent for the encapsulated epoxy resin, which can be dispersed in the epoxy matrix and activated later by heating. However, this is not a true selfhealing, but rather an assisted healing. Tension tests revealed a slight decrease in Young's modulus of the specimens containing the microcapsules but improved elongation at break and unchanged tensile strength. Fracture testing, in the form of single-edge notched bending tests, show a healing efficiency of 111% when the concentration of microcapsules and latent hardener are optimized. Some preliminary tests on epoxy-based fabric laminates containing this self-healing system demonstrated a 68% recovery of virgin interlaminar fracture toughness.Yuan et al. (4) reported another promising combination of healing agent and catalyst for self-healing polymer composites. The healing agent, consisting of a mixture of diglycidyl ether of bisphenol A (DGEBPA) along with a catalyst made from 1-butyl glycidyl ether (BGE), are stored in poly(urea-formaldehyde) (PUF) microcapsules that were prepared by an oilin-water emulsion process. This process of preparing the PUF microcapsules promotes long shelf-life and good chemical stability at temperatures below 238 o C. This system is still in the early developmental stages and the selfhealing efficiency of the system within a composite material is yet to be tested.Here we use a "physical" encapsulation of both epoxy and hardener inside nanoporous silica capsules. Both components are protected inside long channels that comprise the structure of the silica capsules. When they are mixed with the polymer epoxy matrix, they are expected to withst...

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Michael Ramsdell is an Assistant Professor of Physics and Director of First Year Physics at Clarkson University. He has over ten years of experience in the design, implementation, and assessment of laboratory curriculum within introductory physics courses. He has also developed, refined and taught a Pre-Freshman Physics course designed to assist student s with the transition to post-secondary education. He is a Co-Director of the NYS STEP Program, IMPETUS which provides economically disadvantaged students the opportunity to pursue their interest in math and science though educational summer camps, workshops, school-year tutoring and mentoring programs. He has helped provide numerous students and teachers with the opportunity to integrate STEM disciplines using real-world problem solving strategies through teacher/coach training institutes and contest coordination. He is the Adirondack Regional Science Olympiad Coordinator. Robert Prout Jaspersohn, Clarkson UniversityRobert Jaspersohn is a PhD candidate in Physics at Clarkson University, where he received his master's degree, also in Physics. He received his bachelor's degree at the University of Massachusetts, Amherst, in Astronomy, in 2006.c American Society for Engineering Education, 2015 Page 26.967.1 Innovating Engineering Curriculum for First-Year Retention AbstractAn ongoing effort to improve retention rates for first-and second-year engineering students at Clarkson University has resulted in the modernization of the curriculum including 1) the design, development, and rollout of a new course that emphasizes the links between engineering and society for first-year students, and 2) the introduction of a more flexible first year curriculum that offers two paths for incoming First-Year Engineering (FYE) students. The new course was piloted in Spring 2011, has grown into a key element of the modernized curriculum, and was made required for all first-year engineering students beginning in the 2014/15 academic year. In the context of engagement as much as retention, significant changes have been made to the new course curriculum to increase the active learning opportunities offered to the students as well as to link the various elements of the course (e.g., class activities, team-based design project, and summative assessments) to the engineering challenges facing engineers and society today. ABET assessment results demonstrate that the students are not only meeting expectations for the course but also for several key "ABET Criterion 3. Student Outcomes" through the exploration and study of real-world engineering and technological problems. The course addresses ABET criteria (c), (d), (f), (g), (h), and (j); recent assessment results will be presented for (c), (f), and (h), which are emphasized in the course. The impacts of the course on the students' attitudes towards engineering are being assessed with a combination of qualitative and quantitative approaches, including the administration of a survey each semester at the beginning (pre survey) and at the end...

Two surface theories for rate-independent plasticity have previously been shown to offer superior correlative capability in modeling material response under non-proportional loading. In this study, a class of kinematic hardening rules characterized by a decomposition of the total kinematic hardening variable is discussed. The concept of generalized image point hardening in conjunction with mulitple loading surface interpretations is presented. The ability of this class of rules to correlate experimental data from stable nonproportional cycling of Type 304 stainless steel at room temperature is examined. In addition, the proper framework for inclusion of isotropic hardening for this class of models is discussed.