Detecting Delamination in Carbon Fiber Composites Using Piezoresistive Nanocomposites

Carbon fiber prepreg composites are utilized successfully as structural materials for different lightweight aerospace applications. Delamination is a critical failure mode in these composite materials. As composite plies separate from each other, the composite loses some of its ability for supporting expected loads. Therefore, detection of delamination at right time is a foremost significance. This study presents a new way for detecting delamination in composite plates using piezoresistive nanocomposites. This new procedure is setup and studied through both experimental and computational investigations. In this research, nanocomposites with 5% coarse graphene platelets are fabricated for detecting delamination. 8-ply carbon fiber prepreg composite samples are fabricated by placing a Teflon film between layers of prepreg. Piezoresistive nanocomposites are attached on top of prepreg laminate samples using epoxy resin. The change in electrical resistivity of these nanocomposites due to the induced strain from flexural test (three point bend test) on delaminated and neat composite laminates are monitored to demonstrate the delamination detection and neat composite laminates are monitored to demonstrate the delamination detection method. A non-linear finite element model is developed using Abaqus software suite to compliment the mechanical testing. Virtual Crack Closure Technique (VCCT) is used to model a delamination in the composite sample. Experimental results and the simulations in this study indicate that piezoresistive nanocomposites can be used for detecting delamination in carbon fiber composite materials

Conservation in the Bale Mountains National Park: A Statistical Analysis of Population Trends of Ethiopian Wolves (Canis simensis) and Human Influences (2001-2007)

The Ethiopian wolf, Canis simensis, is a large endangered carnivore endemic to the Ethiopian highlands. Over half of the remaining population lives in the Bale Mountains National Park and this population has been monitored since 1983. The present study analyzes the monthly line transect counts in the Sanetti Plateau region of the Park from September 2001-January 2007. As a continuation of the investigation completed by Marion et.al. (2006), these data were analyzed on a yearly basis using index of wolf abundance and encounter rates (divided into three habitat regions) and on a seasonal basis, along with a population density analysis using the Distance 5.0 Release 2 program. Data from the domestic species were also analyzed to determine trends within species and possible relationships between livestock presence and wolf abundance. The present study determined a population density of 0.814 wolves per square kilometer in the transect area. It also found a marked increase in livestock (cattle and sheep/goats) presence since the Marino et.al. (2006) study. There was also a more consistent presence of livestock than previously, as there was no seasonal variation among the study years. Further population density analysis should be done to look for population increase since the 2006 canine distemper epidemic. The recent increase in livestock abundance should also continue to be monitored, especially to see if the wolf populations within optimal habitat regions become affected by the number of livestock

Voltage control in a distribution system using active power loads

High penetration of renewable energy resources such as rooftop solar photovoltaic (PV) systems is exacerbating violations of the voltage limits in power distribution networks. Existing solutions to these over-/under-voltage issues include tap-changing transformers and shunt capacitors. However, tap changers only allow voltage changes in discrete steps and shunt capacitors cannot handle over-voltage situations. To overcome these problems, this thesis proposes voltage control in a distribution system by adjusting active power loads. The proposed solution can be used for both under- and over-voltage cases at any levels of voltage adjustment. First, the active power that needs to be adjusted at selected nodes to bring the voltages within acceptable limits is calculated for under and over-voltage cases using alternating current optimal power flow (ACOPF). ACOPF is solved for three different cases by varying the cost of active power adjustment and the marginal cost from the feeder supply, which is assumed to be the market price. Secondly, demand response on electric water heaters is implemented to achieve active power adjustments at selected nodes obtained from the ACOPF results. The problem is formulated over multiple time steps to minimize the energy costs of water heaters at a specific node subject to the dynamics of the water temperature, the energy consumption, the temperature constraints, and the voltage limits at the node. The IEEE 34-bus radial distribution system is used as a case study. By solving the same problem for different price settings, it is observed that the price structure affects the energy demand only in the under-voltage system, but not in the over-voltage system. The main contribution of this thesis is to show that by adjusting active power loads, voltages in a distribution system can be maintained within the permissible limits --Abstract, page iii

Public art or art in public space: a comparative study of public art and public engagement in Braamfontein, Johannesburg and what this means for public art policy

A research report submitted to the Faculty of Humanities, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Arts and Cultural Management. Johannesburg, 2016Over the past few years there has been an increase in both the number and variety of works of public art in Johannesburg, as well as a movement towards seeing public art as a tool for social cohesion, urban regeneration and community engagement. All of these potential outcomes influence policies, strategies and production processes around public art, with varying results. This research report considers the relationship between public art and public engagement and sets up a scale of engagement that aims to measure the success of public artworks according to their potential to achieve the above outcomes. By asking the key survey question “What do you think of this work?” my research surveyed the users of the spaces surrounding sites of public artworks and uncovered that the public enthusiastically embraced the opportunity to engage with the artworks on different levels, some intended and some unforeseen. The findings in this report have relevance for future monitoring and evaluation of public art projects, as well as subsequent public policy planning in the field of public artMT 201

Kinematics of Inter-Ply Interfaces In Composite Manufacturing

The ubiquitous usage of polymer matrix composites in many applications demands a comprehensive understanding of composite interfaces and processing induced residual stresses, which critically affect both the manufacturing processes and the deformation mechanisms. Processing induced residual stresses are often responsible for causing warping, delamination, and dimensional instability in composite structures. This research includes new in-situ experimental approaches, cure cycle design, interface modification, and thermomechanical modeling for developing a fundamental understanding of the cure kinetics during composite manufacturing. Strains, ply-movement, and formation of defects are observed in-situ using digital image correlation (DIC) during the autoclave cure cycle for the first time. The processing-induced defects in the composite are further characterized by X-ray micro-computed tomography (micro-CT). A non-destructive method is developed to calculate residual stresses using DIC Strains in combination with temperature-dependent moduli obtained from Dynamic Mechanical Analysis (DMA) and Classical Laminate Theory (CLT). Cure cycle design with interrupted cure and interface modification with ZnO nanorods experiments are developed to reduce these processing- induced residual stresses and thereby increase laminate strength. The experimental results are validated through thermomechanical modeling of the composite cure process

Sensory modulation deficits and anxiety symptoms in children receiving occupational therapy

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Occupational Therapy. Johannesburg, 2016This study aimed to identify the association between observable sensory behaviours and anxiety symptoms in school-aged children. The children were between the ages of 8-10 years and attended Remedial Schools. The participants were receiving occupational therapy and were identified as having a Sensory Modulation Disorder (SMD). Parents rated their children on the Sensory Profile, and scores were correlated to the Spence Children’s Anxiety Scale, completed by the children. Participants showed high quadrant scores indicating “low registration” and sensory “over-responsivity” (avoidance and sensitivity to sensory input). Further, the participants were identified to be an “at risk” population for anxiety disorders, as scores of elevated anxiety exceeded normal populations. Although total anxiety scores correlated with only avoidance quadrant scores (and not sensitive scores as predicted,) other scores indicating emotional behaviours correlated moderately with total anxiety scores. It is concluded that children with SMD are at risk of presenting with anxiety disorder symptoms, and must thus be monitored for these.MT201

IMPACTS OF ENERGY PRICE CAP SYSTEM ON ELECTRICITY AND GAS PRICES IN THE ERA OF ENERGY CRISIS

29 million households in the United Kingdom (UK) use Energy Price Cap and the UK government spend about 43 billion dollars a year which is 1.7 percent of the GDP in subsidizing the energy price cap subsidies to the households and businesses. The energy prices in the UK have seen a significant rise in the past few years for distinct reasons. This culminating experience project explains the mechanism of the energy price cap used for the household energy supply in the UK and how it has been affected between the years 2022 to 2024. The research questions are: (Q1) How has the energy cap implemented in the UK impacted electricity prices, particularly in the context of natural gas prices? And (Q2) What are the economic implications of people spending on energy caps and subsidizing household energy bills? The findings and conclusions from the Project are: (Q1) As market conditions are fluctuating the electricity prices were increasing when the natural gas prices were increasing. But the price cap helped the consumers pay significantly less compared to the actual price. (Q2) There was a negative implication on people spending even after subsidizing the household energy bills. The demand for electricity and natural gas has gone down and energy price cap was implemented improperly as high-income households were being benefited paying less percentage of their income into energy expenditure

Temperature and silicon effects on tensile and corrosion behavior of chronium-molybdenum steel

Martensitic P91 grade steels containing 0.48, 0.96, 1.28 and 1.77 weight percent (wt%) silicon (Si) have been tested for evaluation of their tensile properties at temperatures ranging from ambient to 550°C. The effect of activation using accelerator-driven electron beams on the room-temperature tensile properties of steels containing 0.48 and 1.28 wt% Si has also been investigated. The results indicate that all four heats of steel exhibited dynamic strain ageing at temperatures up to 400°C. The activated specimens showed enhanced tensile strength but reduced ductility with increasing activation time, indicating radiation hardening of the tested materials. The electrochemically-polarized specimens showed more noble critical pitting potentials with increasing Si content due to the formation of more protective oxide films. While the tensile specimens tested at 550°C exhibited ductile failures, brittle failures were seen at ambient temperature. However, all activated specimens revealed cleavage facets, indicating predominantly brittle failures

Jewish Renewal: Revitalizing Contemporary American Judaism

The Carl and Dorothy Bennett Center for Judaic Studies at Fairfield University presents two lectures by Dr. Chava Weissler, Scholar in Residence, April 22-23, 2002. Philip and Muriel Berman Professor of Jewish Civilization, Lehigh University, and author of Voices of the Matriarchs, winner of 1999 Koret Foundation Book Award in Jewish History.https://digitalcommons.fairfield.edu/bennettcenter-posters/1221/thumbnail.jp