Development and Application of a Tool for Optimizing Composite Matrix Viscoplastic Material Parameters

This document describes a recently developed analysis tool that enhances the resident capabilities of the Micromechanics Analysis Code with the Generalized Method of Cells (MAC/GMC) and its application. MAC/GMC is a composite material and laminate analysis software package developed at NASA Glenn Research Center. The primary focus of the current effort is to provide a graphical user interface (GUI) capability that helps users optimize highly nonlinear viscoplastic constitutive law parameters by fitting experimentally observed/measured stress-strain responses under various thermo-mechanical conditions for braided composites. The tool has been developed utilizing the MATrix LABoratory (MATLAB) (The Mathworks, Inc., Natick, MA) programming language. Illustrative examples shown are for a specific braided composite system wherein the matrix viscoplastic behavior is represented by a constitutive law described by seven parameters. The tool is general enough to fit any number of experimentally observed stress-strain responses of the material. The number of parameters to be optimized, as well as the importance given to each stress-strain response, are user choice. Three different optimization algorithms are included: (1) Optimization based on gradient method, (2) Genetic algorithm (GA) based optimization and (3) Particle Swarm Optimization (PSO). The user can mix and match the three algorithms. For example, one can start optimization with either 2 or 3 and then use the optimized solution to further fine tune with approach 1. The secondary focus of this paper is to demonstrate the application of this tool to optimize/calibrate parameters for a nonlinear viscoplastic matrix to predict stress-strain curves (for constituent and composite levels) at different rates, temperatures and/or loading conditions utilizing the Generalized Method of Cells. After preliminary validation of the tool through comparison with experimental results, a detailed virtual parametric study is presented wherein the combined effects of temperature and loading rate on the predicted response of a braided composite is investigated

Modelling of Fiber/Matrix Debonding of Composites Under Cyclic Loading

The micromechanics theory, generalized method of cells (GMC), was employed to simulate the debonding of fiber/matrix interfaces, within a repeating unit cell subjected to global, cyclic loading, utilizing a cyclic crack growth law. Cycle dependent, interfacial debonding was implemented as a new module to the available GMC formulation. The degradation of interfacial stresses, with applied load cycles, was achieved via progressive evolution of the interfacial compliance. A periodic repeating unit cell, representing the fiber/matrix architecture of a composite, was subjected to combined normal and shear loadings, and degradation of the global transverse stress in successive cycles was monitored. The obtained results were compared to values from a corresponding finite element model. Reasonable agreement was achieved for combined normal and shear loading conditions, with minimal variation for pure loading cases. The local effects of interfacial debonding, and fatigue damage will later be combined as sub-models to predict the experimentally obtained fatigue life of Ti-15-3/Sic composites at the laminate level

Fatigue Analysis of Notched Laminates: A Time-Efficient Macro-Mechanical Approach

A coupled transversely isotropic deformation and damage fatigue model is implemented within the finite element method and was utilized along with a static progressive damage model to predict the fatigue life, stiffness degradation as a function of number of cycles, and post-fatigue tension and compression response of notched, multidirectional laminates. Initially, the material parameters for the fatigue model were obtained utilizing micromechanics simulations and the provided [0], [90] and [plus or minus 45] experimental composite laminate S-N (stress-cycle) data. Within the fatigue damage model, the transverse and shear properties of the plies were degraded with an isotropic scalar damage variable. The damage in the longitudinal (fiber) ply direction was suppressed, and only the strength of the fiber was degraded as a function of fatigue cycles. A maximum strain criterion was used to capture the failure in each element, and once this criterion was satisfied, the longitudinal stiffness of the element was decreased by a factor of 10 (sup 4). The resulting, degraded properties were then used to calculate the new stress state. This procedure was repeated until final failure of the composite laminate was achieved or a specified number of cycles reached. For post-fatigue tension and compression behavior, four internal state variables were used to control the damage and failure. The predictive capability of the above-mentioned approach was assessed by performing blind predictions of the notched multidirectional IM7/977-3 composite laminates response under fatigue and post-fatigue tensile and compressive loading, followed by a recalibration phase. Although three different multidirectional laminates were analyzed in the course of this study, only detailed results (i.e., stiffness degradation and post-fatigue stress-train curves as well as damage evolution states for a single laminate ([30/60/90/minus 30/minus 60] (sub 2s)) are discussed in detail here

The relationship between information literacy, internet addiction and general health of an Iranian medical students

Introduction: Given the prevalence of Internet use worldwide and its existing risks to societies especially the youngsters, information literacy can affect the use of Internet. Hence, the objective of present study is to assess the relationship between information literacy and Internet addiction and then to investigate the relationship between Internet addiction and general health of students in Iran University of Medical Sciences. Materials and Methods: It is an analytical cross-sectional study which was conducted during 2016 on students in Iran University of Medical Sciences (Tehran, Iran). The sample size for the surveyed community of 6,500 university students was 362 from the Cochran sample size formula. Then, using a simple random sampling method, from each of the colleges, the sample size was selected according to the student population. Three questionnaires of information literacy, Yang's Internet addiction, and general health scale (GHQ-28) were distributed among students. Finally, 365 questionnaires were collected and analyzed. Results: 29.9 of students were about to be addicted to the Internet, 1.3 had symptoms of Internet addiction and 68.8 had no addiction. In terms of information literacy, most of the students were in moderate level (60.5 moderate, 3.3 low, and 36.2 high information literacy level). There was a significant inverse relationship between increasing of information literacy and the Internet addiction (r = -0.45 and p<0.001). The score of general health demonstrated an inverse and significant relationship in different levels of Internet addiction (P <0.001). Conclusion: According to the findings of this study, it was perceived that the higher the information literacy, the lower the level of Internet addiction; besides, reduction of internet addiction increased the general health of students. Therefore, considering the importance of students as the leading group in societies, and favorable consequences of increased information literacy, universities' authorities have to develop and run specific programs within the educational and research schedule in order to increase the students' information literacy. Accordingly, undesirable outcomes of Internet use would be diminished and general health of society would be improved. © 2018, Semnan University of Medical Sciences. All rights reserved

The relationship between information literacy, internet addiction and general health of an Iranian medical students

Introduction: Given the prevalence of Internet use worldwide and its existing risks to societies especially the youngsters, information literacy can affect the use of Internet. Hence, the objective of present study is to assess the relationship between information literacy and Internet addiction and then to investigate the relationship between Internet addiction and general health of students in Iran University of Medical Sciences. Materials and Methods: It is an analytical cross-sectional study which was conducted during 2016 on students in Iran University of Medical Sciences (Tehran, Iran). The sample size for the surveyed community of 6,500 university students was 362 from the Cochran sample size formula. Then, using a simple random sampling method, from each of the colleges, the sample size was selected according to the student population. Three questionnaires of information literacy, Yang's Internet addiction, and general health scale (GHQ-28) were distributed among students. Finally, 365 questionnaires were collected and analyzed. Results: 29.9 of students were about to be addicted to the Internet, 1.3 had symptoms of Internet addiction and 68.8 had no addiction. In terms of information literacy, most of the students were in moderate level (60.5 moderate, 3.3 low, and 36.2 high information literacy level). There was a significant inverse relationship between increasing of information literacy and the Internet addiction (r = -0.45 and p<0.001). The score of general health demonstrated an inverse and significant relationship in different levels of Internet addiction (P <0.001). Conclusion: According to the findings of this study, it was perceived that the higher the information literacy, the lower the level of Internet addiction; besides, reduction of internet addiction increased the general health of students. Therefore, considering the importance of students as the leading group in societies, and favorable consequences of increased information literacy, universities' authorities have to develop and run specific programs within the educational and research schedule in order to increase the students' information literacy. Accordingly, undesirable outcomes of Internet use would be diminished and general health of society would be improved. © 2018, Semnan University of Medical Sciences. All rights reserved

The relationship between genetic variants associated with primary ovarian insufficiency and lipid profile in women recruited from MASHAD cohort study

Background and aim: Primary Ovarian Insufficiency (POI) is defined by the occurrence of menopause before the age of 40 years. It is often associated with cardiovascular disease (CVD). The purpose of this study was to explore the relationship between POI-associated genotypes cardiometabolic disorder risk factors. Methods: One hundred seventeen women with POI and one hundred eighty-three healthy women without POI were recruited in this study. DNA was extracted and analyzed using ASO-PCR or Tetra ARMS-PCR. Lipid profiles were also assessed. Results: Multivariate logistic regression analysis showed that individuals with GG vs. TT genotype of the rs1046089 SNP were more likely to have a higher serum LDL (p = 0.03) compared to the control group. There was also a significant association between low serum HDL and rs2303369 and rs4806660 SNP genotypes in the POI group. In the POI group, the percentage of those with high total cholesterol was lower in those with a CC genotype compared to those with a TT genotype (p = 0.03). Conclusion: Some SNPs reported to be associated with POI appear to be independently associated with dyslipidemia. These results may be helpful to identify subjects with POI who may be susceptible to CVD

The global burden of cancer attributable to risk factors, 2010-19 : a systematic analysis for the Global Burden of Disease Study 2019

Background Understanding the magnitude of cancer burden attributable to potentially modifiable risk factors is crucial for development of effective prevention and mitigation strategies. We analysed results from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 to inform cancer control planning efforts globally. Methods The GBD 2019 comparative risk assessment framework was used to estimate cancer burden attributable to behavioural, environmental and occupational, and metabolic risk factors. A total of 82 risk-outcome pairs were included on the basis of the World Cancer Research Fund criteria. Estimated cancer deaths and disability-adjusted life-years (DALYs) in 2019 and change in these measures between 2010 and 2019 are presented. Findings Globally, in 2019, the risk factors included in this analysis accounted for 4.45 million (95% uncertainty interval 4.01-4.94) deaths and 105 million (95.0-116) DALYs for both sexes combined, representing 44.4% (41.3-48.4) of all cancer deaths and 42.0% (39.1-45.6) of all DALYs. There were 2.88 million (2.60-3.18) risk-attributable cancer deaths in males (50.6% [47.8-54.1] of all male cancer deaths) and 1.58 million (1.36-1.84) risk-attributable cancer deaths in females (36.3% [32.5-41.3] of all female cancer deaths). The leading risk factors at the most detailed level globally for risk-attributable cancer deaths and DALYs in 2019 for both sexes combined were smoking, followed by alcohol use and high BMI. Risk-attributable cancer burden varied by world region and Socio-demographic Index (SDI), with smoking, unsafe sex, and alcohol use being the three leading risk factors for risk-attributable cancer DALYs in low SDI locations in 2019, whereas DALYs in high SDI locations mirrored the top three global risk factor rankings. From 2010 to 2019, global risk-attributable cancer deaths increased by 20.4% (12.6-28.4) and DALYs by 16.8% (8.8-25.0), with the greatest percentage increase in metabolic risks (34.7% [27.9-42.8] and 33.3% [25.8-42.0]). Interpretation The leading risk factors contributing to global cancer burden in 2019 were behavioural, whereas metabolic risk factors saw the largest increases between 2010 and 2019. Reducing exposure to these modifiable risk factors would decrease cancer mortality and DALY rates worldwide, and policies should be tailored appropriately to local cancer risk factor burden. Copyright (C) 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.Peer reviewe