The Effects of Fiber Surface Modification and Thermal Aging on Composite Toughness And its Measurement

A detailed experimental study was conducted to establish the structure-property relationships between elevated temperature aging and (I) fiber-matrix bonding, (2) Mode II interlaminar fracture toughness, and (3) failure modes of carbon fiber/PMR-15 composites. The fiber-matrix adhesion was varied by using carbon fibers with different surface treatments. Short beam shear tests were used to quantify the interfacial shear strength afforded by the use of the different fiber surface treatments. The results of the short beam shear tests definitely showed that, for aging times up to 1000 hr, the aging process caused no observable changes in the bulk of the three composite materials that---would degrade the shear properties of the material. Comparisons between the interlaminar shear strength (ILSS) measured by the short beam shear tests and the GII c test results, as measured by the ENF test, indicated that the differences in the surface treatments significantly affected the fracture properties while the effect of the aging process was probably limited to changes at the starter crack tip. The fracture properties changed due to a shift in the fracture from an interfacial failure to a failure within the matrix when the fiber was changed from AU-4 to AS-4 or AS-4G. There appears to be an effect of the fiber/matrix bonding on the thermo-oxidative stability of the composites that were tested. The low bonding afforded by the AU-4 fiber resulted in weight losses about twice those experienced by the AS-4 reinforced composites, the ones with the best TOS

Discovery of Samarium, Europium, Gadolinium, and Terbium Isotopes

Currently, thirty-four samarium, thirty-four europium, thirty-one gadolinium, and thirty-one terbium isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.Comment: To be published in At. Data Nucl. Data Table

Student attributes related to dual enrollment baccalaureate degree outcomes in a rural state

A decrease in West Virginia in-state college-going and graduation rates and a need for additional postsecondary degrees in the workforce in the state by 2020 require the support and implementation of an evidence-based intervention to ameliorate the pressing issue. This study considers the outcomes in regard to persistence and completion of West Virginia students enrolled in public baccalaureate degree granting institutions in the state who entered as first-time, full-time freshmen during the 2010 academic year with dual enrollment credit. The population of the study was drawn from preexisting data provided by the West Virginia Higher Education Policy Commission. Propensity score matching and statistical analyses, including chi-square, ttest, and logistic regression were used to address the research questions. The study’s findings indicate a significant relationship between dual enrollment and persistence, and also with graduation. These findings also support that among socioeconomic status, college readiness, rurality, sex, and minority status, dual enrollment presents significant models in both persistence and graduation. At the variable level, however, neither sex nor minority status were found significant for persistence or graduation. Further analysis determined that dual enrollment increased the average number of credits earned by the second fall semester by one three-credit course on average and further determined that the dual enrollment students were more likely to graduate based on the number of credits accumulated that same semester

Meeting the guidance needs of youth in the Booker Washington school.

The writer wishes to confess that this has been very difficult problem because certain factors in the overall picture of\u27 the education of the Negro in the South make it almost impossible to rule out passion, not to mention subjectivity. In the responses of the students who filled out questionnaires have been found a number of answers that we should like to ignore. In about half of the instances these students have written, sometimes without invitation, their comments on the back of the mimeographed sheet

Double Beta Decay: Historical Review of 75 Years of Research

Main achievements during 75 years of research on double beta decay have been reviewed. The existing experimental data have been presented and the capabilities of the next-generation detectors have been demonstrated.Comment: 25 pages, typos adde

Nutritional Knowledge and Behaviors of Undergraduate Students

Poor dietary behavior can lead to various chronic health conditions, such as heart disease and obesity. Because dietary intake takes time to impact health, observing diet knowledge in college students can be beneficial. This study sought to measure whether greater nutritional knowledge would translate to a healthier dietary intake. Nutritional knowledge and behavior were measured and then compared in 257 students in two different undergraduate classes - an introductory nutrition course and a standard biology course - which was the control group. Each class was given the same survey at the beginning and end of the fall semester. Results indicated that the knowledge of the recommended daily fruit and vegetable intake, per the USDA, did not improve throughout the semester. There was no significant change in nutrition students that consumed vegetables daily, however the number of students that consumed fruit daily increased by 5%. Knowledge regarding saturated fats increased by 15%. The nutrition students decreased their saturated fat consumption by 1g, which placed their saturated fat intake at 10.2 g per day. Nutrition education had a positive impact on nutritional knowledge and did translate to the students’ diets in some aspects of nutrition, but not all of them. This indicates that nutritional knowledge is an effective way to improve dietary behavior, however knowledge is not always the only factor that will change behavior

Klipsun Magazine, 2019, Volume 50, Issue 01 - Fall

Dear reader, Klipsun Magazine has hit the stands for fifty volumes now—it transformed from student yearbook to a storytelling publication during a time of war, civil unrest, uncertainty and an ever-present sense of indignation. Our writers pursued ledes with that feeling at heart. In this issue you’ll read stories about the long fight to renew the college of ethnic studies, one student’s year-long struggle with homelessness, why one man put a dent in his savings to run for city council, how one person has persevered since her sexual assault and more. I would like to personally thank the Klipsun staff, writers, and advisor for their contribution and dedication to this special issue of Klipsun. We all feel indignant about something, but it’s our course of action that counts. That’s why we report. We write. We must—it is our proud duty. Respectfully, Questen Inghram Editor-in-chiefhttps://cedar.wwu.edu/klipsun_magazine/1272/thumbnail.jp

The Effects of Fiber Surface Modification and Thermal Aging on Composite Toughness and Its Measurement

A detailed experimental study was conducted to establish the structure-property relationships between elevated temperature aging and fiber-matrix bonding, Mode 2 interlaminar fracture toughness, and failure modes of carbon fiber/PMR-15 composites. The fiber-matrix adhesion was varied by using carbon fibers with different surface treatments. Short beam shear tests were used to quantify the interfacial shear strength afforded by the use of the different fiber surface treatments. The results of the short beam shear tests showed that, for times up to 1000 hr, the aging process caused no changes in the bulk of the three composite materials that would degrade the shear properties of the material. Comparisons between the interlaminar shear strengths (ILSS) measured by the short beam shear tests and the GIIC test results, as measured by the ENF test, indicated that the differences in the surface treatments significantly affected the fracture properties while the effect of the aging process was probably limited to changes at the starter crack tip. The fracture properties changed due to a shift in the fracture from an interfacial failure to a failure within the matrix when the fiber was changed from AU-4 to AS-4 or AS-4G. There appears to be an effect of the fiber/matrix bonding on the thermo-oxidative stability of the composites that were tested. The low bonding afforded by the AU 1 fiber resulted in weight losses about twice those experienced by the AS 1 reinforced composites, the ones with the best TOS

Graphite Sheet Coating for Improved Thermal Oxidative Stability of Carbon Fiber Reinforced/PMR-15 Composites

Expanded graphite was compressed into graphite sheets and used as a coating for carbon fiber reinforced PMR-15 composites. BET analysis of the graphite indicated an increase in graphite pore size on compression, however the material was proven to be an effective barrier to oxygen when prepegged with PMR-15 resin. Oxygen permeability of the PMR-15/graphite was an order of magnitude lower than the compressed graphite sheet. By providing a barrier to oxygen permeation, the rate of oxidative degradation of PMR-15 was decreased. As a result, the composite thermo-oxidative stability increased by up to 25%. The addition of a graphite sheet as a top ply on the composites yielded little change in the material's flexural strength or interlaminar shear strength

Energy spectrum of a 2D Dirac electron in the presence of a constant magnetic field

In this paper we obtain exact solutions of a 2D relativistic Dirac oscillator in the presence of a constant magnetic field. We compute the energy spectrum and discuss its dependence on the spin and magnetic field strength.Comment: 7 page