Investigation and characterization of constraint effects on flaw growth during fatigue loading of composite materials

An investigative program is presented in an attempt to add to the current understanding of constraint effects on the response of composite materials under cyclic loading. The objectives were: (1) to use existing data and to develop additional data in order to establish an understanding and quantitative description of flaw growth in unidirectional lamina under cyclic loading at different load direction to fiber direction angles; (2) to establish a similar understanding and description of flaw growth in lamina which are embedded in laminates between other unflawed lamina; (3) to determine the nature of the influence of constraint on flaw growth by quantitatively comparing the results of the tests; and (4) to develop a model and philosophy of constraints effects based on our investigative results

Fatigue Damage in Notched Composite Laminates Under Tension-Tension Cyclic Loads

The results are given of an investigation to determine the damage states which develop in graphite epoxy laminates with center holes due to tension-tension cyclic loads, to determine the influence of stacking sequence on the initiation and interaction of damage modes and the process of damage development, and to establish the relationships between the damage states and the strength, stiffness, and life of the laminates. Two quasi-isotropic laminates were selected to give different distributions of interlaminar stresses around the hole. The laminates were tested under cyclic loads (R=0.1, 10 Hz) at maximum stresses ranging between 60 and 95 percent of the notched tensile strength

Integration and minority fiqh: the halāl to harām ratio

Minority Fiqh, (fiqh al-‘aqalliyyāt), has been theorised by Taha Jabir al-Alwani to assist minority Muslims, particularly in a Western setting, to be able to integrate in society, as in the maxim, “integration without assimilation.” This thesis examines how a selection of Muslims in America interprets and practices Islamic jurisprudence and whether there are similarities to the theoretical fiqh al-aqalliyat. Through a qualitative study of Muslims interviewed in Jacksonville, Florida, this thesis examines how Muslims in the community interpret sharī‘ah, and its purposes (maqāṣid al-sharī‘ah) as it directly relates to them and integration. It is discussed and analysed in comparison to the traditional/taqlīd approach as well as fiqh al-aqaliyat in ordet to shed light on similarities and differences. A two-fold model of integration is assessed, which first incorporates Muslims’ behaviour modification (body), educational efforts (soul), and emotional connection (heart) with the surrounding society. Second, the host society, into which the Muslim-Americans are integrating, is evaluated by acceptance either of ethnicity, cultural traditions and/or religious values of the other. This thesis contributes to the discussion of fiqh al-‘aqalliyyāt to discuss and analyse whether there are similarities found among the respondents practices and views within their context, spanning the gap between al-Alwani’s theory of a fiqh that assists integration and lived experience. Through this process, another model of Muslim integration is proposed of overlapping elements of integration. This also adds to the data involving Muslims of Jacksonville, Florida

Multiphysics analysis of state changes during progressive damage of composite materials

For advanced heterogeneous materials in many applications, material state changes occur during service. The evolution of local details (damage initiation, accumulation, growth, and interaction) controls the progress of global property degradation, and they control the development of the final fracture event, i.e., the life of the engineering component. Traditional damage analysis approaches focus on the detection and location of flaws and defects, not on interactions or relationships between flaws or on the general change of state of the material. However, the changes in stiffness, thermal and electrical conductivity, dielectric permittivity, and structural integrity as a function of those properties are essential information. Therefore, a definitive definition and understanding of the multiphysics changes at the material level is needed. Because creation of a single microscopic crack or other distributed events does not directly affect the strength or life of the composite materials, what is needed is a method of integrating material state changes over the history of events associated with a specific history of applied fields into methodology for predicting remaining strength, stiffness, and life. The approach discussed in this article is founded on the method of Reifsnider, et al., as codified in his text on “Damage Tolerance and Durability of Material Systems” (Wiley, 2003), and on subsequent developments associated with the Energy Frontier Research Center on Heterogeneous Functional Materials led by the University of South Carolina (www.HeteroFoaM.com). As a result of capabilities developed in connection with the HeteroFoaM center, a multiphysics capability has been developed for prognosis in the presence of progressive damage. One of the most interesting aspects of that work is the “generalized compliance method” in which electrical (or thermal) conductivity, dielectric permittivity, and mechanical state variables are tracked and predicted as a method of assessing changes in material and structural integrity for progressive damage. As it happens, the relationship between changes in conduction, for example, and dielectric permittivity as a function of nonconservative deformation history is not linear and must be predicted from first principles solutions to the correct set of multiphysics equations. We have successfully illustrated this capability for polymer-based composites. We will discuss this and other details of this multidisciplinary approach

ANTICIPATING U.S. POPULATION-LEVEL HEALTH AND ECONOMIC IMPACTS USING DISCRETE-EVENT SIMULATION TO GUIDE HEALTH POLICY DECISIONS

This dissertation presents two applications of discrete-event simulation (DES) to represent clinical processes: (1) a model to quantify the risk of the maternal obese and diabetic intrauterine environment influence on progression to adult obesity and diabetes, and (2) a model to evaluate health and economic outcomes of different smoking cessation strategies. The first application considers the public health impact of the diabetic and obese intrauterine environment\u27s effect on the prevalence of diabetes and obesity across subsequent generations. We first develop a preliminary DES model to investigate and characterize the epidemiology of diabetes during pregnancy and birth outcomes related to maternal obesity and diabetes. Using data from the San Antonio Heart Study (SAHS), the 1980 Census and the NCHS we are able to verify a simplified initial version of our model. Our methodology allows us to quantify the impact of maternal disparities between different racial/ethnic groups on future health disparities at the generational level and to estimate the extent to which intrauterine exposure to diabetes and obesity could be driving these health disparities. The populace of interest in this model is women of child-bearing age. The preliminary model is next modified to accommodate data and assumptions representing the United States population. We use a mixed-methods approach, incorporating both statistical methods and discrete event simulation, to examine trends in weight-gain over time among white and black women of child-bearing age in the US from 1980 to 2008 using United States Census projections and National Health and Nutrition Examination Survey (NHANES) data. We use BMI as a measure of weight adjusted for height. We establish an underlying population representative of the population prior to the onset of the obesity epidemic. Assessing the rate of change in body mass index (BMI) of the population prior to the obesity epidemic allows us to make \u27unadjusted\u27 projections, assuming that subsequent generations carry the same risk as the initial cohort. Unadjusted projections are compared to actual trends in the US population. This comparison allows us to quantify the trends in weight-gain over time. This model is interesting as a first step in understanding the trans-generational impact of obesity during pregnancy at the population level. The aim of the second application is to understand the impact of different pharmacologic interventions for smoking cessation in achieving long-term abstinence from cigarette smoking is an important health and economic issue. We design and develop a clinically-based DES model to provide predictive estimates of health and economic outcomes associated with different smoking cessation interventions. Interventions assessed included nicotine replacement therapy, oral medications (bupropion and varenicline), and abstinence without pharmacologic assistance. We utilized data from multiple sources to simulate patients\u27 actions and associated responses to different interventions along with co-morbidities associated with smoking. Outcomes of interest included estimates of sustained abstinence from smoking, quality adjusted life years, cost of treatment, and additional health-related costs due to long-term effects of smoking (lung cancer, chronic obstructive pulmonary disease, stroke, coronary heart disease). Understanding the comparative effectiveness and intrinsic value of alternative smoking cessation strategies can improve clinical and patient decision-making and subsequent health and economic outcomes at the population level. This dissertation contributes to the field of industrial engineering in healthcare. US population-level data structures are not always available in the desired format and there is not one method for managing the data. The key element is to be able to link the mathematical model with the available data. We illustrate various methods (i.e. bootstrap techniques, mixed-effects regression, application of probability distributions) for extracting information from different types of data (i.e. longitudinal data, cross-sectional data, incidence rates) to make population-level predictions. Methods used in cost-effectiveness evaluations (i.e. incremental cost-effectiveness ratio, bootstrap confidence intervals, cost-effectiveness plane) are applied to output measures obtained from the simulation to compare alternative smoking cessation strategies to deduce additional information. While the estimates resulting from the two models are topic-specific, many of the modules created for these studies are generic and can easily be transferred to other disease models. It is believed that these two models will aid decision makers in recognizing the impact that preventative-care initiatives will have, and to evaluate possible alternatives

Incentives as connectors : insights into a breastfeeding incentive intervention in a disadvantaged area of North-West England

PMID: 22458841 [PubMed - indexed for MEDLINE] PMCID: PMC3414740 Free PMC ArticlePeer reviewedPublisher PD

The relationship of maternal BMI and child body size, home environment, and food in low-income minority women and children participating in a child obesity primary and secondary prevention project

Session presented on Saturday, July 26, 2014: Purpose: The primary and secondary obesity prevention projects were developed through community-based participatory research with a local grass-roots organization and the local WIC program. Both programs focused on nutrition guidance to mothers and encouragement of more physical activity with less time devoted to screen viewing (television and computer). The projects are based on the Ecological Model of Growth (EMG). Methods: The mothers and children were recruited through several WIC clinics within the same county. The instruments used to collect data were based on the EMG and reflected the food environment (24 hour diet recall, Household Food Inventory [HFI]), the level of stimulation in the home (HOME Screening Questionnaire [HSQ], hours of TV viewing), and maternal body size. The results from the first data collection time period for both projects are presented in this paper. Results: The association between fiber and protein was non-significant although approaching significance; the association between fiber and fat were non-significant, and the association between fat and protein was highly significant (p \u3c.000). There were no significant associations between types of food intake and child or maternal BMI. There were significant associations between the Household Food Inventory and the HSQ (p\u3c.03) and between HFI and TV hours (p =.05). Conclusion: The types of food in the home affect mother and child body size. Hours of TV watching and the level of high calorie foods in the house are positively associated. In addition, the amount of high calorie food in the household is associated with the level of stimulation in the home. This could possibly demonstrate that interactions between mother and child involve pleasurable foods (high sugar, high fat). The relationships of maternal and child body sizes may possibly be positively related to number of high calorie foods in the house although this was not conclusively shown in this project

Defect coupling: The last frontier in predicting the strength, life, and durability of fiber reinforced composite laminates

After more than 30 years of careful experimental investigation and exhaustive development of discrete damage analysis methods including integrated computational mechanics methods, our community knows a great deal about how discrete defects such as matrix cracks and defect growth (e.g. delamination) can be predicted. But many practical situations controlled by laminated multiaxial composite structures, the loss of performance and “sudden death” end of life is controlled by defect coupling which becomes a precursor to fracture plane development. Until recently, analysis methods to address such complex interaction and coupling of multiple defects and experimental methods of following the details of such interaction sequences as a foundation for understanding and model validation were not available. We believe that this barrier has been largely removed by recent work. Please click Additional Files below to see the full abstract

Hydrogen Fuel Cell Development in Columbia (SC)

This is an update to the final report filed after the extension of this program to May of 2011. The activities of the present program contributed to the goals and objectives of the Fuel Cell element of the Hydrogen, Fuel Cells and Infrastructure Technologies Program of the Department of Energy through five sub-projects. Three of these projects have focused on PEM cells, addressing the creation of carbon-based metal-free catalysts, the development of durable seals, and an effort to understand contaminant adsorption/reaction/transport/performance relationships at low contaminant levels in PEM cells. Two programs addressed barriers in SOFCs; an effort to create a new symmetrical and direct hydrocarbon fuel SOFC designs with greatly increased durability, efficiency, and ease of manufacturing, and an effort to create a multiphysics engineering durability model based on electrochemical impedance spectroscopy interpretations that associate the micro-details of how a fuel cell is made and their history of (individual) use with specific prognosis for long term performance, resulting in attendant reductions in design, manufacturing, and maintenance costs and increases in reliability and durability