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1
Taylor, Janice D., University of Western Sydney, College of Social and Health Sciences e of Nursing Family and Community Health School. "Exploring postnatal fatigue : influential factors and management strategies for women". THESIS_CSHS_NFC_Taylor_J.xml, 2003. http://handle.uws.edu.au:8081/1959.7/740.
Testo completoAbstract (sommario):
Caring for a new child is a significant, demanding, and time consuming role, often associated with increased stress. Postnatal depression is one possible outcome of increased stress and research has highlighted the importance of detecting depression in new mothers. However fatigue a correlate of depression, has only recently become a focus of research among health professionals. Understanding the nature of fatigue and its management within the postnatal period, the focus of this study, may reduce its impact on women’s lives. This longitudinal study explores changes in intensity, physical, mental and emotional dimensions of fatigue, factors associated with higher levels of fatigue, the impact of fatigue on women’s usual activities, and strategies for managing fatigue. Self-administered structured questionnaires gathered data form 504 women at 1, 6, 12 and 24 weeks after birth. Reliable and valid instruments were used to measure the relationship between the defined factors and the outcome of fatigue at the various time points. State anxiety was a consistently strong predictor of fatigue intensity across time and group. Women sought to manage their fatigue by using self-care practices and asking for help from family and friends. This research highlights two issues for health professionals – care of new mothers must include recognition that higher levels of state anxiety are associated with higher levels of postnatal fatigue: ongoing assessment of fatigue and the strategies used to manage it is essential beyond the early postnatal periodDoctor of Philosophy (PhD)
2
Robertshaw, Hazel Patricia. "Fatigue in women with breast cancer : a longitudinal study". Thesis, King's College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435010.
Testo completo
3
Taylor, Janice D. "Exploring postnatal fatigue : influential factors and management strategies for women". Thesis, View thesis, 2003. http://handle.uws.edu.au:8081/1959.7/740.
Testo completoAbstract (sommario):
Caring for a new child is a significant, demanding, and time consuming role, often associated with increased stress. Postnatal depression is one possible outcome of increased stress and research has highlighted the importance of detecting depression in new mothers. However fatigue a correlate of depression, has only recently become a focus of research among health professionals. Understanding the nature of fatigue and its management within the postnatal period, the focus of this study, may reduce its impact on women’s lives. This longitudinal study explores changes in intensity, physical, mental and emotional dimensions of fatigue, factors associated with higher levels of fatigue, the impact of fatigue on women’s usual activities, and strategies for managing fatigue. Self-administered structured questionnaires gathered data form 504 women at 1, 6, 12 and 24 weeks after birth. Reliable and valid instruments were used to measure the relationship between the defined factors and the outcome of fatigue at the various time points. State anxiety was a consistently strong predictor of fatigue intensity across time and group. Women sought to manage their fatigue by using self-care practices and asking for help from family and friends. This research highlights two issues for health professionals – care of new mothers must include recognition that higher levels of state anxiety are associated with higher levels of postnatal fatigue: ongoing assessment of fatigue and the strategies used to manage it is essential beyond the early postnatal period
4
Profant, Judith. "Fatigue and sleep complaints in women treated for breast cancer /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3129934.
Testo completo
5
Taylor, Janice D. "Exploring postnatal fatigue : influential factors and management strategies for women /". View thesis, 2003. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20051125.152732/index.html.
Testo completo
6
Guenette, Jordan Ali. "Respiratory mechanics and diaphragmatic fatigue during exercise in men and women". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/19995.
Testo completoAbstract (sommario):
Purpose: The purpose of this thesis was to determine the underlying mechanisms associated with a higher total WOB in women (Study 1) and to determine if women experience greater levels of diaphragmatic fatigue relative to men (Study 2).
Methods:
Study 1: Sixteen endurance-trained subjects (8M:8F) underwent a progressive cycling test to exhaustion while esophageal pressure and lung volumes were measured. Modified Campbell diagrams were used to calculate the inspiratory and expiratory resistive and elastic components at 50, 75, 100 l·min⁻¹ and maximal ventilations and also at standardized mass-corrected work-rates.
Study 2: Thirty-eight endurance-trained subjects (19M:19F) underwent a constant-load cycling test at 90% of peak work-rate until exhaustion. Pressure-time product of the diaphragm (PTPdi) was calculated during exercise. Trans-diaphragmatic pressure twitches (Pdi,tw) were assessed using cervical magnetic stimulation before and 10, 30 and 60 minutes after exercise. Diaphragm fatigue was defined as a ≥ 15% reduction in Pdi,tw post-exercise.
Results:
Study 1: The inspiratory resistive WOB was higher in women at all absolute ventilations (P<0.05). The expiratory resistive WOB was higher in women at 75 l·min⁻¹ (P<0.05). There were no sex-differences in the elastic WOB. However, the total WOB was significantly higher in men at relative percentages of maximal ventilation (P<0.05) but this sex-difference was reversed when the WOB was standardized for a given work-rate to body mass ratio.
Study 2: Diaphragm fatigue was present in 11 males and 8 females. The reduction in Pdi,tw at 10 and 30 min following exercise was significantly greater in men relative to women (P<0.05). Men consistently had higher absolute values for PTPdi during exercise but this sex-difference was reversed when body mass was taken into account. Over time, men continued to have a reduced contribution of the diaphragm to total inspiratory force output whereas diaphragmatic contribution in women remained relatively constant over time.
Conclusions: The higher total WOB in women is due to an increased resistive WOB which is likely attributable to their smaller airways. Despite a respiratory system that may have a higher mechanical cost of breathing, women appear to be more resistant to exercise-induced diaphragmatic fatigue.
7
Mckeown, Alison Clare. "Relationships in women with a diagnosis of chronic fatigue sysndrome (CFS)". Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527253.
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8
Bounds, Emilee M. "Effects of a functional fatigue protocol on maximal softball hitting /". Read thesis online, 2010. http://library.uco.edu/UCOthesis/BoundsEM2010.pdf.
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9
Short, Michala. "Persistent fatigue and endocrine function in women after radiotherapy for breast cancer". Thesis, The University of Sydney, 2010. http://hdl.handle.net/2123/6446.
Testo completoAbstract (sommario):
The experience of persistent fatigue after breast cancer treatment is estimated to affect approximately one in four women, but fatigue development and factors associated with cancer-related fatigue are poorly understood. Gaining a better understanding of these issues is important because persistent fatigue after radiation therapy can be a debilitating experience for cancer survivors. The objectives of this study were: (1) to determine fatigue prevalence in women with breast cancer at standardised timepoints after radiation therapy; (2) to investigate the relationships between fatigue, salivary cortisol rhythm and thyroid function; (3) to investigate the amount of radiation dose received by the thyroid gland in different radiation therapy treatment techniques; and (4) to investigate the relationship between irradiation of the thyroid, thyroid function and fatigue. Participants in this research were women diagnosed with non-metastatic breast cancer and all were referred for adjuvant radiation therapy treatment. One cohort of participants (n = 48) was assessed prior to the start of radiation therapy and then six months after treatment, and a second cohort (n = 15) was assessed at six months and then at 12 months after treatment. Behavioural assessments included questionnaires that measured the level of multidimensional fatigue (MFSI–SF), the degree of fatigue and depression symptoms (SPHERE–12), impact that fatigue had on participants’ functioning (FIS) and aspects of quality of life (EORTC QLQ–C30). Biological assessments included a three day measurement of salivary cortisol rhythm and an assessment of thyroid function (TSH, free T4 and free T3). Radiation doses to the thyroid gland were determined from participants’ treatment plans. Six months after completing adjuvant radiation therapy, women receiving treatment for breast cancer experienced significant improvements in emotional fatigue, role functioning and social functioning. High fatigue levels were prevalent in 29% of women at six months and 33% of women at 12 months after treatment, but newly developed fatigue that was not present before treatment was only found in 5% of participants. There were no significant changes in cortisol rhythm over time or between fatigued and non-fatigued participants; however, significant positive correlations were found between fatigue and morning cortisol. Regarding thyroid function, significant decreases in free T4 hormone levels were seen from six months to 12 months after radiation therapy with larger decreases in free T4 levels being related to higher fatigue. Radiation doses to the thyroid gland were significantly higher in participants who received treatment to the regional lymphatics with a supraclavicular fossa radiation field compared to participants who received localised treatment to the breast or chest wall only. In the former, changes in thyroid function were observed, as were relationships between mean radiation dose to the thyroid and thyroid function.
10
Short, Michala. "Persistent fatigue and endocrine function in women after radiotherapy for breast cancer". University of Sydney, 2010. http://hdl.handle.net/2123/6446.
Testo completoAbstract (sommario):
Doctor of Philosophy(PhD)The experience of persistent fatigue after breast cancer treatment is estimated to affect approximately one in four women, but fatigue development and factors associated with cancer-related fatigue are poorly understood. Gaining a better understanding of these issues is important because persistent fatigue after radiation therapy can be a debilitating experience for cancer survivors. The objectives of this study were: (1) to determine fatigue prevalence in women with breast cancer at standardised timepoints after radiation therapy; (2) to investigate the relationships between fatigue, salivary cortisol rhythm and thyroid function; (3) to investigate the amount of radiation dose received by the thyroid gland in different radiation therapy treatment techniques; and (4) to investigate the relationship between irradiation of the thyroid, thyroid function and fatigue. Participants in this research were women diagnosed with non-metastatic breast cancer and all were referred for adjuvant radiation therapy treatment. One cohort of participants (n = 48) was assessed prior to the start of radiation therapy and then six months after treatment, and a second cohort (n = 15) was assessed at six months and then at 12 months after treatment. Behavioural assessments included questionnaires that measured the level of multidimensional fatigue (MFSI–SF), the degree of fatigue and depression symptoms (SPHERE–12), impact that fatigue had on participants’ functioning (FIS) and aspects of quality of life (EORTC QLQ–C30). Biological assessments included a three day measurement of salivary cortisol rhythm and an assessment of thyroid function (TSH, free T4 and free T3). Radiation doses to the thyroid gland were determined from participants’ treatment plans. Six months after completing adjuvant radiation therapy, women receiving treatment for breast cancer experienced significant improvements in emotional fatigue, role functioning and social functioning. High fatigue levels were prevalent in 29% of women at six months and 33% of women at 12 months after treatment, but newly developed fatigue that was not present before treatment was only found in 5% of participants. There were no significant changes in cortisol rhythm over time or between fatigued and non-fatigued participants; however, significant positive correlations were found between fatigue and morning cortisol. Regarding thyroid function, significant decreases in free T4 hormone levels were seen from six months to 12 months after radiation therapy with larger decreases in free T4 levels being related to higher fatigue. Radiation doses to the thyroid gland were significantly higher in participants who received treatment to the regional lymphatics with a supraclavicular fossa radiation field compared to participants who received localised treatment to the breast or chest wall only. In the former, changes in thyroid function were observed, as were relationships between mean radiation dose to the thyroid and thyroid function.
11
Viberg, Lovisa, e Hillevi Sebbfolk. "Kvinnors erfarenheter av fatigue vid bröstcancerbehandling : En litteraturstudie". Thesis, Umeå universitet, Institutionen för omvårdnad, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-183308.
Testo completoAbstract (sommario):
Bakgrund: Flertalet kvinnor med bröstcancer genomgår olika stadier ochbehandlingar i sjukdomen. Olika biverkningar uppstå, exempelvis illamående,smärta och fatigue. Fatigue är ett symtom som har stor negativ påverkan på kvinnorslivskvalitet. Det finns ytterligare behov av forskning inom området då kunskapen omfatigue är bristfällig. Syfte: Syftet med litteraturstudien var att beskriva kvinnors upplevelse av fatiguevid bröstcancerbehandling. Metod: En kvalitativ litteraturstudie som innefattar tio vetenskapliga artiklar medkvalitativ metod. Databaser som har använts är Cinahl, PubMed, Medline, Scopusoch PsycInfo. Analysen utfördes med hjälp av Fribergs modell. Resultat: Fyra kategorier identifierades. I första kategorin, försämrad livskvalitet,ingår begränsningar i det dagliga livet, hjälplöshet och ensamhet samt förändradsjälvuppfattning. Andra kategorin svårigheter i relationer omfattar bristandekunskap hos anhöriga, negativ påverkan på roller inom familjen och nedsatt sexlust.I tredje kategorin, olika sätt att hantera fatigue ingår, vila, hjälp från familj ochvänner, fysisk aktivitet och religion. Fjärde kategorin, otillräckliga vårdinsatser,omfattar avsaknad av information och rädsla att inte bli tagen på allvar. Konklusion: Kvinnornas erfarenhet av fatigue visade på försämrad livskvalitet ochlidande. Ett större behov av stöd och information från sjukvården finns. Genom ökadkunskap hos sjuksköterskor kan det frambringa ett bättre bemötande och bättre vårdsamt minskat lidande för kvinnor med fatigue vid bröstcancer.Background: The majority of women with breast cancer are going throughdifferent stages and treatments during their period of illness. Fatigue is a side effectthat can appear and has a negative effect on women's quality of life. Aim: The aim of this study was to investigate women´s experiences of fatigue duringand after breast cancer treatment. Methods: A qualitative literature study which includes ten scientific articles withqualitative methods. Databases used were Cinahl, PubMed, Medline, Scopus andPsycInfo. The analyze was based on Fribergs model. Results: Four categories were identified. The first category, declining quality of lifeincludes limitations in everyday life, helplessness and loneliness and changed selfperception.The second category, struggles in relationships, brings up a lack ofknowledge among friends and family, negative influence on the roles within thefamily and reduced sexdrive. The third category, different methods to managefatigue, includes rest, help from family and friends, physical activity and religion. Thefourth category, inadequate care interventions, highlights a lack of information andfear to not be taken seriously. Conclusion: The women's experiences of fatigue showed a deteriorated quality oflife and suffering. The women are in need of more support and information aboutfatigue from healthcare. Through increased knowledge for nurses, they can givebetter treatment and care which can lead to a reduced suffering for the women withbreast cancer related fatigue.
12
Gray, Cheri Lynn. "Depression, Fatigue, Declines in Cognitive Function and Uncertainty in Women with Multiple Sclerosis". Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/321610.
Testo completoAbstract (sommario):
The purpose of this study was to describe the relationships among common signs/symptoms (depression, fatigue, declines in cognitive function) in women with multiple sclerosis (MS) using a modified version of Braden's Self Help Theoretical Model and evaluate whether depression, fatigue, declines in cognitive function and uncertainty, enabling skills (self-control in this study) and self-management (coping in this study) influence quality of life outcomes in women with MS. MS is one of the most common causes of disability among young adults and is the most prevalent neurological disease among young and middle-aged adults in certain parts of the world. Although research had previously been undertaken with regards to the common symptoms of MS, uncertainty, enabling skills, self-management and quality of life, there had been no studies undertaken that involved all of them. This descriptive study was the first to explore relationships among common symptoms of MS, uncertainty, enabling skills, self-management and quality of life in an MS population using Braden's Learned Response Chronic Illness Self Help Model. A cross-sectional descriptive study was conducted with 106 participants. Measurement tools utilized in the study included: 1) Demographic and Illness Characteristics, 2) The Modified Fatigue Impact Scale, 3) Perceived Deficits Questionnaire, 4) Patient Health Questionnaire-9, 5) Mishel's Uncertainty in Illness Scale- Adult, 6) Rosenbaum's Self-Control Scale- Modified, 7) COPE Inventory-Brief, and 8) SF-36 Health Status Questionnaire. Data analysis involved descriptive statistics, correlations and linear regression to answer the specific aims. The study findings indicate that relationships exist among depression, fatigue, declines in cognitive function, uncertainty, enabling skills and self-management in women with MS. The study findings also indicate that depression, fatigue, declines in cognitive function, uncertainty, enabling skills and self-management influence quality of life outcomes in women with MS. Finally, while only a first study, the research findings indicate using a modified version of Braden's Learned Response Chronic Illness Self Help Model (LRCISHM) is appropriate in a population of women with MS. Future research involving women with MS who meet the inclusion criteria across the contiguous United States as well as male military veterans with MS is recommended. Research involving this modified version of Braden's LRCISHM as well as research incorporating disability levels is recommended. Research to develop interventions to improve quality of life outcomes and minimize distress is also recommended.
13
Ikeuchi, Kaori. "The relation between mindfulness and the fatigue of women with breast cancer: path analysis". Kyoto University, 2020. http://hdl.handle.net/2433/259735.
Testo completo
14
Bennett, Barbara Kaye School of Medicine UNSW. "Characterising the nature of postcancer fatigue in women treated for early-stage breast cancer". Awarded by:University of New South Wales. School of Medicine, 2006. http://handle.unsw.edu.au/1959.4/31202.
Testo completoAbstract (sommario):
The problem investigated Four studies investigated the phenomenon of cancer-related fatigue (CRF) in women who had received adjuvant treatment for early-stage breast cancer, with a view to reducing the diagnostic uncertainty surrounding the syndrome and thus facilitating progress in both clinical management and aetiological research. Procedures and results A cross-sectional study of 109 women compared a ???cancer-specific??? self-report questionnaire (FACT-F) (canvassing fatigue symptoms) and a more generic questionnaire (SPHERE) (identifying depression and fatigue). Thirty-seven percent of women reported fatigue. Overall in 20%, fatigue was associated with psychological distress. Seventeen percent of women had fatigue but no depression. A qualitative study utilised focus groups to identify and compare the distinctive features of CRF with those of women with chronic fatigue syndrome (CFS). A similar set of symptoms was found in both groups, including overwhelming fatigue, un-refreshing sleep and subjective concentration problems. However, women with CFS also reported myalgia and arthralgia. Using the Structured Clinical Interview for Neurasthenia- SCIN, the third study compared the symptoms of three groups of women with fatigue: those with CRF, CFS or major depression. The detailed ???interviewer guide??? provided explicit directions for evaluating and classifying symptoms. This study confirmed the core symptom of ???profound fatigue unrelieved by rest???, and additional features that distinguished between the clinical diagnoses. The fourth study compared features of the evolution of clinically-identified fatigue syndromes in women from two prospective cohort studies; women with post-cancer fatigue (PCF) and women with post-infective fatigue syndrome (PIFS). Major conclusions A syndrome of PCF, present at least six months following adjuvant treatment and unexplained by medical or psychiatric disorder was investigated. The characteristics of PCF and those of CFS are very similar, with the fatigue state having indistinguishable descriptors. Longitudinal evaluation of the symptom complexes of PCF and PIFS suggests divergent pathways may be relevant. Co-morbid features like sleep disturbance; physical deconditioning and mood disturbance may be implicated as factors in the evolution and prolongation of PCF. These studies provide a basis for a more uniform and rigorous classification system - a necessary first step towards advancing the field both in investigating aetiology and new intervention strategies.
15
Newland, Pamela Kay. "Impact of symptoms on quality of life in women with relapsing-remitting multiple sclerosis and healthy women". Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4343.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Missouri-Columbia, 2006."December 2006" The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Vita. Includes bibliographical references.
16
Banthia, Rajni. "Post-treatment fatigue in breast cancer survivors : the role of sleep quality and depressed mood /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3130213.
Testo completo
17
Lam, Wendy Wing-Tak. "Interrelationships among physical symptom distress, psychological distress, and fatigue in women with breast cancer undergoing radiation therapy". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ29303.pdf.
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18
Merriman, John D. "Predictors of the trajectories of self-reported attentional fatigue in women with breast cancer undergoing radiation therapy". Diss., Search in ProQuest Dissertations & Theses. UC Only, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1465497.
Testo completo
19
Haas, Barbara Kay. "Fatigue, self-efficacy for physical activity, physical activity, and quality of life in women with breast cancer". Full text (off-campus access restricted to users with UT Austin EID) Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3037017.
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20
Budhrani, Pinky H. "Race/Ethnicity, Subjective and Objective Sleep Quality, Physical and Psychological Symptoms in Breast Cancer Survivors". Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4645.
Testo completoAbstract (sommario):
Breast cancer is a major health problem and comprises the largest population of cancer survivors in the United States, estimated at 2.9 million women, accounting for 22% of all cancer survivors (National Cancer Institute, 2013). The advances in breast cancer screening, diagnosis and treatment has increased the importance of survivorship needs. A major concern among breast cancer survivors (BCS) is sleep disturbances. This study used an innovative approach to examine ethnic and racial disparities in sleep disturbances present in BCS. In addition, this study also explored sleep disturbances across different races/ethnicities. This study was a secondary data analysis of baseline data from the supplement study of the MBSR Symptom Cluster Trial for Breast Cancer Survivors/ 1R01CA131080, conducted by Dr. Lengacher. Sleep was measured using the Pittsburgh Sleep Quality Index, sleep diary (subjective), and sleep actigraphy (objective). The sample consists of 79 women who had been diagnosed with breast cancer (Stage 0, I, II, III), completed lumpectomy and/or mastectomy, and were within 2 weeks to 2 years post radiation and/or chemotherapy treatment. The aims for this study were to: 1) explore racial/ethnic differences in objectively measured sleep patterns among BCS; 2) estimate and compare the correlation between objective and subjective sleep quality by racial/ethnic groups among BCS; 3) examine which sleep actigraphy measure appears to have the strongest relationship with physical and psychological symptoms; and 4) explore whether these relationships (i.e. between objective sleep and self-reported symptoms) appear to be modified by race/ethnicity.
The first aim was conducted using analysis of variance (ANOVA) and analysis of covariance (ANCOVA). Results indicated that white, non Hispanic BCS had improved objective sleep quality compared to minority BCS. The second aim was conducted using Pearson's correlation with significant correlations found between subjective and objective sleep onset latency (r= .310, p= .016), and total sleep time (TST) (r= .328, p= .011) for the white, non-Hispanic group. The third aim was conducted using Pearson's correlation with significant correlations between sleep onset latency and depression (r= .247, p= .029); sleep efficiency and depression (r= -.233, p= .040); sleep efficiency and fatigue (r= -.207, p= .045); and WASO and pain (r= .277, p= .014). There were no significant correlations between the anxiety score and actigraphy parameters.
Using the significant correlations from the results of the third aim, multiple regression analysis was conducted with age as a covariate to test the fourth aim. The main effect of depression on sleep efficiency was significant (p= .044) with less depression associated with higher sleep efficiency. The interaction term, depression by race/ethnicity, had a non-significant effect on sleep efficiency (p= .299). The main effect of pain on WASO was significant (p= .008), and increased pain was associated with longer WASO. The interaction term, race/ethnicity by pain, had a non-significant effect on WASO (p= .148). The main effect of depression predicting sleep onset latency was significant (p= .027), and the interaction term, depression by race/ethnicity, had a trend towards a significant effect (p= .092) on predicting sleep onset latency. The interaction between depression and race/ethnicity predicting sleep onset latency was further decomposed using multiple regression. The average sleep onset latency was longer in the minority group with high depression levels (42 minutes) compared to the white, non-Hispanics with high depression levels (29 minutes). Race modified the effect of depression on sleep onset latency in this sample of BCS.
These finding suggest that the experience of objective sleep disturbances is different among races/ethnicities. Additional research is needed to further explore racial/ethnic differences in subjective and objective sleep disturbances and its impact on physical and psychological symptoms among BCS. As the number of BCS continue to rise, it is becoming increasingly important to recognize sleep disturbances and their potential physical and psychological effects early in BCS, specifically in different races and ethnicities. It is anticipated that these findings may contribute to improved symptom management for women of different races and ethnicities.
21
Reynolds, Staci Kayleen. "Effects of Same-day Strength Training on Serve Performance in Female Collegiate Tennis Players". Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd746.pdf.
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Broberg, Sara, e Sophie Lidström. "Kvinnor med bröstcancer och deras erfarenheter av fysisk aktivitet vid fatigue : En litteraturstudie". Thesis, Högskolan i Gävle, Avdelningen för vårdvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-31336.
Testo completoAbstract (sommario):
Bakgrund: Bröstcancer är den vanligaste formen av cancer som drabbar kvinnor och den behandlas vanligen med kirurgi, strålning och cellgiftsbehandling. Både bröstcancer och dess behandling är känd för att ge många symtom och biverkningar varav fatigue, extrem trötthet, är en av de vanligaste. Fatigue påverkar kvinnornas vardag, sociala liv och många upplever minskad livskvalité. Att vara fysisk aktiv förebygger många sjukdomar och på så vis kan en aktiv livsstil öka välbefinnandet och bidra till en ökad livskvalité. Sjuksköterskan har som ansvar att främja och bevara hälsa vilket kan uppnås genom att informera, stödja och motivera kvinnorna till att utföra egenvård under och efter cancerbehandling. Syfte: Litteraturstudiens syfte var att beskriva vilka erfarenheter kvinnor med bröstcancer har av fysisk aktivitet vid fatigue. Metod: Beskrivande litteraturstudie utifrån 12 kvantitativa vetenskapliga artiklar identifierande utifrån databassökningar via MEDLINE på PubMed och CINAHL. Artiklarna är granskade med granskningsmallar och sammanfattade utefter likheter och skillnader. Resultat: Kvinnorna erfor att fysisk aktivitet lindrade deras fatigue. Regelbunden träning var en viktig faktor för god effekt och mer krävande träning visade sig ha bättre resultat än lättare träning. Under cellgiftsbehandling ökar symtomen av fatigue, resultatet visar då att styrketräning och högintensiv intervallträning har mycket god effekt på fatigue. Fysisk aktivitet hade god effekt vid fatigue i upp till tre månader efter behandling. Slutsats: Kvinnorna upplevde att fysisk aktivitet i olika former reducerade deras fatigue. därför bör fysisk aktivitet erbjudas som en del av bröstcancerbehandlingen då många av kvinnorna lider av fatigue.Background: Breast cancer is the most usual form of cancer affecting women and is usually treated with surgery, radiation and chemotherapy. Breast cancer and its treatment are known to cause many symptoms and side effects, which fatigue is one of the most common. Fatigue affects women's everyday lives, social life and many experiences reduced quality of life. Being physically active prevents many diseases, an active lifestyle can increase well-being and contribute to an improved quality of life. The nurses is responsible for promoting and maintaining health which they can accomplish by informing, supporting and motivating the women to perform self-care during and after cancer treatment. Aim: The purpose of the literature study was to describe which experiences women with breast cancer have of physical activity while they suffer fatigue. Method: Descriptive literature study based on 12 quantitative scientific articles identified by database searches using MEDLINE on PubMed and CINAHL. The articles are reviewed with review templates and summarized along similarities and differences. Results: The women experienced that physical activity had a good effect on reducing fatigue. Regular training was an important factor for good effect and more demanding exercise proved to have better results than lighter exercise. The result shows that resistance training and high-intensity interval training have a very good effect on fatigue when the symptoms of fatigue increase during chemotherapy. Physical activity had a good effect on fatigue for up to three months after treatment. Conclusion: Women experienced that physical activity of different types reduced their fatigue, physical activity should be offered as part of breast cancer treatment since many of the women suffer from fatigue.
23
Mlynski, Christopher. "Cardiovascular Response to a Behavioral Restraint Challenge: Urge Magnitude Influence in Men and Women". Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984125/.
Testo completoAbstract (sommario):
Agtarap, Wright, Mlynski, Hammad, and Blackledge took an initial step in providing support for the predictive validity of a new conceptual analysis concerned with behavioral restraint, defined as active resistance against a behavioral impulse or urge. The current study was designed to partially replicate and extend findings from their study, employing a common film protocol and a procedure for inducing low- and high levels of fatigue. Analyses on key data indicated that the fatigue manipulation was ineffective. On the other hand, they supported the suggestion that behavioral restraint should be proportional to the strength of an urge being resisted so long as success is perceived as possible and worthwhile. Analyses also provided evidence of gender differences for this behavioral restraint task. Women showed relatively enhanced CV responses to my manipulation of urge magnitude, performed less well, rated the behavioral restraint challenge as harder, and rated success on the more difficult behavioral restraint task as more important. A broad indication is that men and women can differ in the strength of impulses they experience in response to stimulus presentations as well as in the importance they place on resisting the impulses.
24
So, Kwok-Wei. "The symptom cluster of fatigue, pain and psychological distress and its impact on the quality of life in Chinese patients with breast cancer undergoing cancer treatment /". Connect to full text via ProQuest. Limited to UCD Anschutz Medical Campus, 2007.
Cerca il testo completoAbstract (sommario):
Thesis (Ph.D. in Nursing) -- University of Colorado Denver, 2007.Typescript. Includes bibliographical references (leaves 168-181). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;
25
von, Thiele Schwarz Ulrica. "Health and ill health in working women – balancing work and recovery". Doctoral thesis, Stockholms universitet, Psykologiska institutionen, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8297.
Testo completoAbstract (sommario):
Work conditions within the public health care sector are physically and psychosocially demanding. This means that balancing work with recovery is essential for employees in order to avoid ill health and stay healthy. This thesis is based on four studies. Study I investigated the prevalence of upper extremity disorders (UED) in female dental personnel. Results showed that 81% reported UED. Consequently, interventions aimed at reducing these risks were called for. Study II investigated the health-related effects of two work-place interventions, physical exercise (PE) and reduced working hours (RWH). Health-improvements were more consistent in the PE group, suggesting that PE may be an appropriate intervention to reduce health-risks. However, there were no effects on recovery from work or fatigue, which may result from other factors, such as overcommitment (OC), that prolong or sustain stress-related activity. Study III showed that high OC was associated with poorer next-day recovery and increased fatigue. Also, OC was a more important predictor of lack of recovery and fatigue than were psychosocial work characteristics. This highlights the importance of considering perseverative cognitions in relation to recovery from work and fatigue, and has implications for interventions targeting work-related ill health. Study IV related lack of recovery and fatigue to cumulative biological risk, allostatic load (AL), and to individual biomarkers. Women with a profile characterized by fatigue, sleep difficulties and lack of short-term recovery had a 2.9 increased risk of AL. This was not shown in analyses of individual biomarkers. In sum, this thesis shows that recovery from work is an important factor in relation to women’s work-related health. Fatigue and recovery should be considered interrelated but distinct concepts and recovery should be assessed as an early risk factor for stress-related disease with early risk being investigated using AL rather than individual biomarkers.
26
Koertge, Jenny. "Vital exhaustion and coronary artery disease in women : biological correlates and behavioral intervention /". Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-564-6/.
Testo completo
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Badr, Hanan A. "EFFECTS OF POSTPARTUM FATIGUE AND DEPRESSIVE COGNITIONS ON LIFE SATISFACTION AND QUALITY OF LIFE IN POSTPARTUM WOMEN: THE INTERVENING ROLE OF RESOURCEFULNESS". Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case153193055061821.
Testo completo
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Khemthong, Supalak. "The Relationship between frequency and satisfaction of leisure participation and health-related quality of life in women with fatigue secondary to chronic illness". Thesis, Curtin University, 2007. http://hdl.handle.net/20.500.11937/2080.
Testo completoAbstract (sommario):
Fatigue secondary to chronic illness (FSCI) is a common experience in individuals with chronic conditions, with fatigue impacting on performance of daily activities and health-related quality of life (HRQoL). Due to the higher prevalence of FSCI in women, they may experience even greater disruption to roles and activity engagement. The literature consistently points to three main aspects when defining fatigue regardless of diagnoses; a physical aspect, a psychological aspect, and the impact on activity and participation. Research into the first two aspects has demonstrated relationships between fatigue, pain, depression, and social support. However, examination of the third aspect has been largely overlooked with respect its relationship to, and impact on, fatigue. Leisure theorists have hypothesized that engagement in leisure activities makes a positive contribution to physical and mental health. Previous research has measured leisure activities based on frequency of, or satisfaction with, participation. While some research has shown that physical and social activities have positive health benefits, gaps still exist in understanding the relative contribution of different types of leisure participation to fatigue and HRQoL.For example, little research has examined the contributions of leisure participation and leisure satisfaction to HRQoL and fatigue in women with chronic conditions. One explanation for the lack of research may be the absence of measurement tools developed to classify and quantify participation in different types of leisure activities for women with FSCI. Without a measurement tool, the relative contribution of participation in different activities (by frequency and/or satisfaction) to fatigue and HRQoL cannot be examined.This PhD research aimed to fill the current gaps in understanding different types of leisure participation in related to fatigue and HRQoL. It sought to address two component parts: development and testing of the Classification of Leisure Participation (CLP) Scale; and an examination of the contribution of leisure participation to fatigue and HRQoL in women with FSCI.
29
Cormack, Stuart J., e n/a. "The changes in strength, power and associated functional physiological measures in elite women soccer players during a 12 month preparation for a major event". University of Canberra. Health and Biomedical Science, 2003. http://erl.canberra.edu.au./public/adt-AUC20050411.134745.
Testo completoAbstract (sommario):
The assessment of strength and power and the relationship of these measures to
functional variables such as speed and vertical jump ability are understood poorly.
This is particularly the case when dealing with a long-term preparation for a major
event in a sport such as women's soccer.
The results of this research suggest that a number of isoinertial speed strength
measures may be sensitive to aspects of a training program and therefore be useful
tools for determining the level of development of various underlying neuromuscular
capacities.
Further results provide a question mark about the role of maximum strength in the
development of high velocity functional movements, as increases in maximum
strength did not correlate to changes in measures of functional performance.
An important finding from this research is the potential role of specific isoinertial
speed strength parameters in the detection of neuromuscular fatigue. Time course
analysis of the results in this study suggests that the use of these measures to detect
fatigue warrants further investigation.
30
Khemthong, Supalak. "The relationship between frequency and satisfaction of leisure participation and health-related quality of life in women with fatigue secondary to chronic illness /". Full text available, 2006. http://adt.curtin.edu.au/theses/available/adt-WCU20070821.124638.
Testo completo
31
Khemthong, Supalak. "The Relationship between frequency and satisfaction of leisure participation and health-related quality of life in women with fatigue secondary to chronic illness". Curtin University of Technology, School of Occupational Therapy, 2007. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=17166.
Testo completoAbstract (sommario):
Fatigue secondary to chronic illness (FSCI) is a common experience in individuals with chronic conditions, with fatigue impacting on performance of daily activities and health-related quality of life (HRQoL). Due to the higher prevalence of FSCI in women, they may experience even greater disruption to roles and activity engagement. The literature consistently points to three main aspects when defining fatigue regardless of diagnoses; a physical aspect, a psychological aspect, and the impact on activity and participation. Research into the first two aspects has demonstrated relationships between fatigue, pain, depression, and social support. However, examination of the third aspect has been largely overlooked with respect its relationship to, and impact on, fatigue. Leisure theorists have hypothesized that engagement in leisure activities makes a positive contribution to physical and mental health. Previous research has measured leisure activities based on frequency of, or satisfaction with, participation. While some research has shown that physical and social activities have positive health benefits, gaps still exist in understanding the relative contribution of different types of leisure participation to fatigue and HRQoL.For example, little research has examined the contributions of leisure participation and leisure satisfaction to HRQoL and fatigue in women with chronic conditions. One explanation for the lack of research may be the absence of measurement tools developed to classify and quantify participation in different types of leisure activities for women with FSCI. Without a measurement tool, the relative contribution of participation in different activities (by frequency and/or satisfaction) to fatigue and HRQoL cannot be examined.This PhD research aimed to fill the current gaps in understanding different types of leisure participation in related to fatigue and HRQoL. It sought to address two component parts: development and testing of the Classification of Leisure Participation (CLP) Scale; and an examination of the contribution of leisure participation to fatigue and HRQoL in women with FSCI.
32
Shaffer, Andrea. "The experience of fatigue and quality of life in patients with advanced lung cancer". [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003301.
Testo completo
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Naraphong, Wipasiri. "Effects of a Culturally Sensitive Exercise Program on Fatigue, Sleep, Mood, and Symptom Distress among Thai Women with Breast Cancer Receiving Adjuvant Chemotherapy: A Pilot Randomized Controlled Trial". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368084924.
Testo completo
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Montalti, Camila Stein 1988. "Qualidade de vida e fadiga avaliadas pelos questionários SF-36 e FACIT-F em mulheres com e sem anemia com sangramento menstrual abundante = Quality of life and fatigue evaluated by SF-36 and FACIT-F questionnaires in anemic and non anemic women with heavy menstrual bleeding". [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/309687.
Testo completoAbstract (sommario):
Orientadores: Ilza Maria Urbano Monteiro, Maria Yolanda MakuchDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
Made available in DSpace on 2018-08-28T02:22:46Z (GMT). No. of bitstreams: 1 Montalti_CamilaStein_M.pdf: 1208610 bytes, checksum: f81cceda9a4fdf6f5d2f94dfa9b3583b (MD5) Previous issue date: 2015
Resumo: INTRODUÇÃO: Sangramento menstrual abundante (SMA) é uma queixa comum entre as mulheres e pode comprometer a qualidade de vida (QV), além de levar à diminuição da concentração sérica de hemoglobina (Hb), causando anemia e fadiga. OBJETIVO: Verificar a prevalência de anemia, taxas baixas de ferro e ferritina entre as mulheres com e sem SMA, e comparar a QV e fadiga em mulheres anêmicas e não anêmicas com SMA confirmada. MÉTODOS: Foram realizados dois cortes transversais em mulheres com queixa de SMA, entre 18 e 55 anos, atendidas no Ambulatório de Hemorragia Uterina da UNICAMP. No primeiro estudo, foi realizada uma revisão de prontuários das mulheres atendidas entre 2011 e 2014 e extraídos os dados sobre os sintomas e hemograma. As mulheres foram divididas em três grupos: SMA (n=160), sem SMA (n=45), confirmados pelo Pictorial Blood Loss Assessment Chart (PBAC), e SMA subjetivo (n=160) sem confirmação do PBAC. No segundo estudo, entre 2013 e 2014, as mulheres com SMA confirmado pelo PBAC responderam a uma ficha de avaliação, ao questionário SF-36, à escala de fadiga FACIT-F e realizaram hemograma. Foram formados dois grupos: com anemia (GCA) apresentando níveis de Hb sérica menor que 12 g/dL (n=24) e sem anemia (GSA) com níveis de Hb sérica maior ou igual a 12 g/dL (n=51). RESULTADOS: No primeiro estudo os níveis médios de Hb e ferro séricos estiveram em torno do normal e semelhantes nos três grupos, enquanto os níveis de ferritina sérica foram mais baixos no grupo SMA. As frequências de anemia foram 33,1%, 28,9% e 40% nos grupos SMA, sem SMA e SMA subjetivo, respectivamente, sem diferenças significativas. Da mesma forma, não houve diferença significativa nos percentuais de mulheres com níveis de ferro e ferritina séricos baixos. No segundo estudo, as médias de Hb, ferro e ferritina séricos foram significativamente menores no GCA. Apesar do resultado médio de ferro e ferritina séricos nos dois grupos estarem dentro da normalidade, a frequência de mulheres com ferro e ferritina séricos baixos foi maior no GCA. No questionário SF-36 não houve diferença significativa entre os grupos, com variação de escore entre 20 e 63 nos oito domínios. O escore da escala de fadiga FACIT-F também não teve diferença significativa entre os grupos (26,3 no GCA e 30,6 no GSA), mas no GCA o escore foi abaixo de 30, ou seja, apresentou fadiga grave. CONCLUSÃO: Estes resultados reforçam a hipótese de que a queixa de SMA deve ser valorizada, independentemente da anemia, uma vez que apenas um terço das mulheres com SMA apresenta Hb abaixo do normal. Como o SMA torna-se uma condição crônica em muitas mulheres, a anemia não chega a comprometer a qualidade de vida e fadiga, uma vez que esta já estava afetada pelo próprio sangramento excessivo
Abstract: BACKGROUND: Heavy menstrual bleeding (HMB) is a common complaint among women and may compromise the quality of life (QoL). It can lead to decreased serum hemoglobin (Hb) level, resulting to anemia and fatigue. OBJECTIVE: To evaluate the prevalence of anemia and iron deficiency in women with and without confirmed HMB and to compare QoL and fatigue in anemic and non-anemic women with HMB. METHODS: Two cross-sectional studies were conducted with women with HMB complaint between 18 and 55 years old at the Department of Obstetrics and Gynecology, School of Medical Sciences, UNICAMP. In the first study, we reviewed medical charts between 2011 and 2014 and data on symptoms and blood counts were extracted. Women were separated into three groups: HMB (n=160), Non-HMB (n=45), both confirmed by the Pictorial Blood Loss Assessment Chart (PBAC), and subjective HMB (Subj-HMB) (n=160) without PBAC confirmation. In the second study, between 2013 and 2014, women with HMB confirmed by PBAC completed an evaluation form, the SF-36 health survey questionnaire, the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) scale and were evaluated by the blood count. They were divided into two groups: anemic (hemoglobin <12 g/dl; n=24) and non-anemic (hemoglobin ?12 g/dl; n=51). RESULTS: In the first study, mean serum hemoglobin and iron levels were similar in all three groups, while serum ferritin levels were lower in the HMB group. Frequencies of anemia were 33.1%, 28.9% and 40% in the HMB, non-HMB and subj-HMB groups, respectively, with no statistically significant differences. Likewise, there were no significant differences in the percentages of women with low serum iron levels or low serum ferritin levels. In the second study, mean serum hemoglobin, iron and ferritin levels were significantly lower in the anemic group. Although mean serum iron and ferritin levels were within the normal limits in both groups, there were more women with low serum iron and ferritin levels in the anemic group. The SF-36 questionnaire scores ranged from 20 to 63, with no significant difference between the groups. The FACIT-F score was also similar for both groups, 26.3 in the anemic group and 30.6 in the non-anemic group, however in the anemic group the score was below 30, ie, severe fatigue. CONCLUSION: These results give strength to the hypothesis that the complaint of HMB must be valorized irrespective of its association with anemia, since only 30% of women with HMB show low hemoglobin levels. HMB has become a chronic condition in many women, so anemia does not influence QoL and fatigue because the excess bleeding itself already affects these women¿s conditions
Mestrado
Fisiopatologia Ginecológica
Mestra em Ciências da Saúde
35
Schmitt, Lisa. "Efeitos do exercício terapêutico na fadiga em mulheres com cancro da mama: uma revisão bibliográfica". Bachelor's thesis, [s.n.], 2021. http://hdl.handle.net/10284/10211.
Testo completoAbstract (sommario):
Projeto de Graduação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Licenciada em FisioterapiaObjetivo: Com esta revisão bibliográfica pretendeu-se entender os efeitos do exercício terapêutico na fadiga em mulheres com cancro da mama. Metodologia: Foi realizada uma pesquisa nas bases de dados PubMed e PEDro (Physiotherapy Evidence Database) entre Janeiro e Fevereiro de 2021, para identificar os estudos randomizados controlados que avaliassem os efeitos de exercícios na qualidade de vida, fadiga, depressão e força muscular principalmente. A qualidade metodologia foi avaliada através da escala de PEDro. Resultados: Nove estudos foram incluídos, com um total de 884 mulheres participantes. Obtiveram uma média de 6.44 segundo a escala de PEDro. Dos estudos incluídos, os exercícios terapêuticos aeróbicos e de resistência demostraram um efeito benéfico para a diminuição da fadiga. Conclusão: Os exercícios terapêuticos parecem ter um efeito positivo na redução da fadiga em mulheres com cancro da mama e tendem a melhorar sua qualidade de vida.
Objective: This literature review aimed to understand the effects of therapeutic exercise on fatigue in women with breast cancer. Methodology: A search was performed in the PubMed and PEDro (Physiotherapy Evidence Database) databases between January and February 2021, to identify randomized controlled studies that assessed the effects of exercise on quality of life, fatigue, depression and muscle strength mainly. Methodological quality was assessed using the PEDro scale. Results: Nine studies were included, with a total of 884 women participating. They obtained an average of 6.44 according to the PEDro scale. Of the studies included, aerobic and resistance therapeutic exercises have shown a beneficial effect for reducing fatigue. Conclusion: Therapeutic exercises seem to have a positive effect on reducing fatigue in women with breast cancer and tend to improve quality of life.
N/A
36
Patel, Sneha Ramesh. "Durability of Advanced Woven Composites in Aerospace Applications". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/33736.
Testo completoAbstract (sommario):
The objective of this project was to evaluate and model the effects of moisture, temperature, and combined hygrothermal aging on the durability of a graphite/epoxy woven composite material system. Imposed environmental and aging conditions were considered to be representative of service conditions for the engine of an advanced subsonic aircraft for which the composite system is a candidate material. The study was designed such that the results could be used in a residual strength based life prediction approach that accounted for both the mechanical fatigue and environmental conditions. Damage mechanisms and failure modes were determined through fatigue testing, residual strength testing, and nondestructive evaluation. The experimental data generally revealed little effect of environment on strength degradation during fatigue despite notable differences in damage accumulation processes.
Modeling efforts were concentrated on initial stiffness, moisture uptake, and residual strength prediction, where the results from the first two efforts were intended to generate inputs for the life prediction. The Ishikawa and Chou fiber undulation and bridging model [22] was shown to provide an accurate stiffness prediction and was subsequently used in parametric studies to determine the effect of weave architecture and geometry. A moisture uptake model developed by Roy [16] for laminates containing single direction cracks was extended to predict moisture uptake in laminates containing cracks in directions parallel and transverse to the loading direction. The life prediction approach was based on ideas developed by Reifsnider and colleagues [36,37,43]. The intention in this case was to use the critical element paradigm to predict the combined effects of alternating environmental (temperature and moisture) conditions imposed during fatigue. Since experimental results indicated that temperature and moisture did not significantly affect the strength and life of the material, a successful life prediction analysis was performed as a function of only fatigue stress level and cycles.Master of Science
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Poole, Matthew C. "Fatigue damage development in 3D woven glass and glass/carbon composites". Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/845964/.
Testo completoAbstract (sommario):
A number of studies have been conducted on 3D non-crimp orthogonal woven composites, but their industrial application is still in its infancy. 3D woven composites show increased through-thickness strength, reducing delamination damage, which is often a key failure mechanism for composites under various loading conditions, especially fatigue. This work investigates the fatigue performance and damage development in a 3D non-crimp orthogonal woven composite consisting of three weft tow layers, two warp tow layers, and a through-thickness z-binder that interlaces along the warp-direction. While the properties of carbon fibres are generally superior to glass fibres, they are more expensive. Therefore, it is of interest to see if the fatigue performance of a glass fibre 3D orthogonal weave can be improved via selective hybridisation using a small amount of carbon fibres. Initial work began on a commercial all-glass 3D orthogonal weave called 3D-78, which was produced by 3TEX. It was found that quasi-static tensile mechanical properties were the same for both warp and weft loading directions, but when loaded in tension-tension fatigue, the warp direction had longer fatigue lifetimes than the weft-direction. The crack density was lower in warp-direction specimens as a result of greater micro-delamination growth blunting stress concentrations around the tips of matrix cracks. The micro-delamination damage in warp-direction fatigue specimens showed a shield-like shape (not previously observed), i.e. wider along one side and narrowing to a point on the other side; where delamination was restricted (at the pointed end), fibre fractures occurred in the adjacent warp tow. The pointed portion of the micro-delamination corresponded to proximity to a z-binder crown. Other damage that was common to both loading directions (warp and weft) included: transverse cracks in transverse tow and resin-rich regions, z-binder debonding, and longitudinal tow splitting cracks. No obvious failure sites were noted for weft-direction fatigue loading. The second material used, 3DMG, was manufactured by the University of Manchester. This material was produced with two different z-binder tensions. The initial z-binder tension (3DMG-T1) resulted in a higher tensile modulus and strength-to-failure, and lower strain-to-failure, for the warp-direction, while the tensile fatigue properties of both directions were similar. Increasing the z-binder tension (3DMG-T2) reduced the tensile modulus and increased the strain-to-failure of the warp-direction, with these properties now similar in both loading directions; the tensile strength for both loading directions remained similar. However, the fatigue performance of the warp-direction was observed to increase with increased z-binder tension, while the weft-direction remained the same. The damage that developed in both materials was similar to the damage in 3D-78, and remained practically the same regardless of z-binder tension, though the energy dissipated per cycle for warp-direction specimens was higher in 3DMG-T1, which corresponds well with the lower number of cycles to failure. The final material tested was a University of Manchester hybrid 3D non-crimp orthogonal woven composite, termed 3DMHyb; here the glass fibre z-binder was replaced with carbon fibre; the z-binder tension used here was the same as 3DMG-T2. Generally, the quasi-static properties of this hybrid material were similar in both loading directions, with the exception of the tensile modulus which was approximately 10% higher, indicating that the carbon fibre z-binder may influence low strain properties. Additionally, the properties of 3DMHyb remained similar to 3DMG-T2. For fatigue performance, However, the fatigue lifetime to failure appeared to increase by a factor of just over 2 at lower peak stress/initial peak strains for the hybrid warp-direction specimens. Again, the energy dissipation per cycle was lower for specimens that had larger number of cycles to failure, in this case the hybrid specimens. Damage development also remained similar between the 3DMG-T2 and 3DMhyb specimens, indicating that the extension of fatigue life noted in 3DMHyb may be the result of the carbon fibre z-binder supressing the development of damage mechanisms leading to ultimate failure of the specimens.
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Hart, M. J. Alexandra. "Action in Chronic Fatigue Syndrome: an Enactive Psycho-phenomenological and Semiotic Analysis of Thirty New Zealand Women's Experiences of Suffering and Recovery". Thesis, University of Canterbury. Social and Political Sciences, 2010. http://hdl.handle.net/10092/5294.
Testo completoAbstract (sommario):
This research into Chronic Fatigue Syndrome (CFS) presents the results of 60 first-person psycho-phenomenological interviews with 30 New Zealand women. The participants were recruited from the Canterbury and Wellington regions, 10 had recovered. Taking a non-dual, non-reductive embodied approach, the phenomenological data was analysed semiotically, using a graph-theoretical cluster analysis to elucidate the large number of resulting categories, and interpreted through the enactive approach to cognitive science.
The initial result of the analysis is a comprehensive exploration of the experience of CFS which develops subject-specific categories of experience and explores the relation of the illness to universal categories of experience, including self, ‘energy’, action, and being-able-to-do.
Transformations of the self surrounding being-able-to-do and not-being-able-to-do were shown to elucidate the illness process.
It is proposed that the concept ‘energy’ in the participants’ discourse is equivalent to the Mahayana Buddhist concept of ‘contact’. This characterises CFS as a breakdown of contact. Narrative content from the recovered interviewees reflects a reestablishment of contact.
The hypothesis that CFS is a disorder of action is investigated in detail.
A general model for the phenomenology and functional architecture of action is proposed. This model is a recursive loop involving felt meaning, contact, action, and perception and appears to be phenomenologically supported.
It is proposed that the CFS illness process is a dynamical decompensation of the subject’s action loop caused by a breakdown in the process of contact.
On this basis, a new interpretation of neurological findings in relation to CFS becomes possible. A neurological phenomenon that correlates with the illness and involves a brain region that has a similar structure to the action model’s recursive loop is identified in previous research results and compared with the action model and the results of this research. This correspondence may identify the brain regions involved in the illness process, which may provide an objective diagnostic test for the condition and approaches to treatment.
The implications of this model for cognitive science and CFS should be investigated through neurophenomenological research since the model stands to shed considerable light on the nature of consciousness, contact and agency.
Phenomenologically based treatments are proposed, along with suggestions for future research on CFS. The research may clarify the diagnostic criteria for CFS and guide management and treatment programmes, particularly multidimensional and interdisciplinary approaches.
Category theory is proposed as a foundation for a mathematisation of phenomenology.
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Thibodeau, Elisabeth Gabrielle. "Static and Fatigue Fracture Characterization of Primary and Secondary Bonded Woven E-Glass Composites". Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/ThibodeauEG2007.pdf.
Testo completo
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Amini, Ahmad J. "Static and Fatigue Failure Response of Woven Carbon Fiber Specimens with Double Edge Notches". DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/425.
Testo completoAbstract (sommario):
Carbon fiber composites are continually seeing increased use in aerospace applications. It is necessary to understand their failure modes in order to properly design and perform analysis on structures constructed primarily from them. This thesis studies woven carbon fiber composites with and without double-edge notches in a series of static and fatigue tests performed on an Instron 8801 servo-hydraulic testing system.
Specimens were constructed of Advanced Composites Group product # LTM45EL woven carbon fiber pre-preg/epoxy and were cut to approximately 9-inch in length and 1-inch in width. Notches were cut into some of the specimens using a slitting saw blade of 0.006-in. thickness.
Ultimate strength, Young’s modulus and Poisson’s ratio for specimens were determined to be 119,418 psi, 7,149,000 psi and 0.05, respeictively. Fracture stress for specimens with notch depths of 0.10, 0.15, 0.20, 0.25, 0.30 and 0.35 was determined to be 93,481 psi, 88,193 psi, 86,968 psi, 81,112 psi, 84,197 psi and 81,955 psi, respectively. The results from these tests showed that the specimens followed Griffith’s model for brittle failure.
Average number of cycles to failure was determined to be 6,600, 37,200, 94,300 and 293,400 for fatigue tests with maximum stresses of 72.5%, 75%, 77.5% and 80% of the ultimate strength. Fatigue tests performed on notched specimens produced data that was too scattered from which to draw a statistically significant result. Numerical modeling in Abacus showed comparable results to experimental tests for stress and strain.
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Angrand, Lise. "Modèle d’endommagement incrémental en temps pour la prévision de la durée de vie des composites tissés 3D en fatigue cyclique et en fatigue aléatoire". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN005/document.
Testo completoAbstract (sommario):
Les travaux présentés dans ce document s’insère dans le cadre du Projet de Recherche Concerté PRC Composites, financé par la DGAC et impliquant le groupe Safran, l’Onera et un grand nombre de laboratoires du CNRS de le LMT Cachan. Un des objectifs principal du PRC est d’établir des modèles pour la simulation du comportement mécanique, de la durabilité et encore des procédés de fabrication des pièces composites CMC & CMO. Ces travaux de thèse se focalisent sur l’étude du comportement des composites tissés 3D aux sollicitations de fatigue mécanique. Ils font suite aux travaux menés à l’Onera sur un modèle d’endommagement en cycles pour la fatigue des composites CMO tissés 3D, nommé ODM-CMO. Nous proposons un modèle dit « temporel », nommé OD ̇M, qui détermine l’évolution de l’endommagement de façon continue, en fonction du temps. Ce modèle est alors capable d’une part de prendre en compte des chargements de fatigue cycliques, et d’autre part les chargements de fatigue complexes, aléatoires. La loi d’endommagement proposée fait intervenir deux contributions, une contribution monotone et une contribution de fatigue. La contribution monotone est totalement équivalente à la loi monotone du modèle initial ODM-CMO, les paramètres sont alors facilement identifiables. La contribution de fatigue n’est pas équivalente à la loi du modèle ODM-CMO, ceci s’explique notamment par le fait qu’il existe différentes façon de prendre en compte la notion de contrainte moyenne, notion primordiale concernant l’étude de la fatigue. Nous avons choisi de prendre en compte l’effet de contrainte moyenne en ajoutant le calcul d’une moyenne originale qui évolue au cours du chargement dans la contribution de fatigue de la loi d’endommagement. L’identification des paramètres de fatigue se déroule en deux étapes. La première étape se base sur une simplification du jeu d’équation du modèle (élasticité et endommagement non couplé) de façon à déterminer une relation simple, en 1D, entre le nombre de cycles à rupture et la contrainte maximale. Cette expression nous permet alors de tracer rapidement les diagrammes de Wöhler (σ_a ou σ_Max vs N_R) ainsi que les diagrammes de Haigh (σ_a vs σ ̅). Ces diagrammes nous permettent de faire une première identification des paramètres de la contribution de fatigue de la loi d’endommagement. La seconde étape consiste à recaler certains paramètres en utilisant le modèle complet, de façon numérique, le modèle ayant été programmé en 3D tant pour un pilotage en déformation que pour un pilotage en contrainte. La méthodologie proposée nécessite néanmoins d’avoir un nombre important de résultats d’essais de fatigue. Elle permet l’identification à d’autres températures dans le but de proposer des modélisations anisothermes. Le modèle d’endommagement est rendu probabiliste grâce à une première approche, pragmatique, en fatigue à grands nombres de cycles. Un paramètre du modèle initialement considéré comme déterministe, prend le statut de variable aléatoire, il s’agit du seuil d’endommagement de fatigue (en déformation) délimitant le domaine d’endurance illimitée. L’idée étant de pouvoir associer à une probabilité de rupture (ou de survie) à une limite de fatigue « asymptotique »The work presented in this report is part of the Collaborative Research Project PRC Composites, funded by the DGAC involving Safran, Onera and several CNRS laboratories whose LMT Cachan. One of the main objectives of this project PRC is to establish models capable to simulate the mechanical behavior, durability and still manufacturing processes for composite PMC. This thesis focus on the study of the behavior of 3D woven composite to mechanical fatigue stresses. This thesis further to the work developed at Onera on cycle damage models for fatigue on PMC, named ODM-PMC. We propose a kinetic damage model, which calculates the kinetic damage evolution, over time. This model is then able to take into account the cycle fatigue loads, and on the other hand the complex or random fatigue loads. The proposed kinetic damage law involves two damage contributions, a monotonous contribution for static loads and a fatigue contribution for fatigue loads. The monotonous contribution is fully equivalent to the monotonous law of ODM-PMC model, the parameters are easily identifiable. The fatigue contribution is not equivalent to the fatigue damage law of initial model ODM-PMC, this is explained by the fact that there are different ways to take into account the average stress effect, unavoidable concept for the study of fatigue loads. We have chosen to consider the mean stress effect by adding the calculation of a mean that evolves during the loading. The identification of fatigue parameters takes place in two steps. The first step is based on a simplification of the model equation set (elasticity and damage are not coupled) to determine a simple relationship, 1D, between the number of cycles to failure and the maximum stress. This expression allows us then quickly to draw diagrams Wohler (σ_a ou σ_Max vs N_R) as well as Haigh diagram (σ_a vs σ ̅). These diagrams allow us to make an initial identification of fatigue parameters. The second step is to readjust certain parameters using the full model 3D, numerical, the 3D model was been encoded for both strain and stress steering. Nevertheless, the methodology requires having a lot of experimental results. It allows also to identifying fatigue parameters at other temperatures in order to provide isothermal modeling. The damage model is made with a first probabilistic approach, pragmatic, to the great number of cycles fatigue. One parameter (determinist), is defined as a random variable, it is the fatigue damage threshold (strain) delimiting the endurance unlimited domain
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Dai, Shuo. "Mechanical characterisation and numerical modelling of 3D woven composites". Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16221.
Testo completoAbstract (sommario):
Three-dimensional woven composites were developed to improve the through-thickness properties which conventional two-dimensional laminate composites currently lack. However, these textile composites generally show lower in-plane mechanical properties due to fibre crimping, and also encounter modelling difficulties due to the complex geometries. In this thesis, the static and fatigue mechanical behaviour of several types of 3D woven composites were experimentally characterised, the influence of the weave architecture on the mechanical performance was revealed, and meso/macro scale numerical models with improved failure criteria were developed to simulate the tensile behaviour of the 3D woven composites. The mechanical characterisation was conducted on six woven structures under tension, compression, and flexural loading, and were also carried out on two weaves under open-hole quasi-static tensile and fatigue loading. Digital image correlation and thermoelastic stress analysis were used to characterise the strain and damage development during static and fatigue loading. The testing results showed that the angle-interlock weave W-3 had higher in-plane quasi-static properties, lower notch sensitivity, higher fatigue damage resistance, but lower delamination resistance. The meso-scale model was developed on the unit cell of the woven structure and the macro-scale model (mosaic model) was created on the testing samples. Both un-notched and notched tensile behaviour were modelled for the angle-interlock weave W-3 and a one-by-one orthogonal weave W-1, and the difference between the predicted and experimental results was within 16% for the unit cell models and within 21% for the mosaic models. A modified failure criterion was developed to better simulate the damage behaviour of the notched macro-scale model and improved the predicted notched strength by 10-20%. Whilst further experimental investigation and improvement in the modelling techniques are still required, the data presented in this thesis provided an essential update for the current 3D woven composites research, and the presented models offered the potential to predict the damage behaviour of large 3D woven structures.
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Wen, Chao. "Bounding Surface Approach to the Fatigue Modeling of Engineering Materials with Applications to Woven Fabric Composites and Concrete". Diss., North Dakota State University, 2011. https://hdl.handle.net/10365/28843.
Testo completoAbstract (sommario):
It has been known that the nucleation and growth of cracks and defects dominate the fatigue damage process in brittle or quasi-brittle materials, such as woven fabric composites and concrete. The behaviors of these materials under multiaxial tensile or compression fatigue loading conditions are quite complex, necessitating a unified approach based on principles of mechanics and thermodynamics that offers good predictive capabilities while maintaining simplicity for robust engineering calculations. A unified approach has been proposed in this dissertation to simulate the change of mechanical properties of the woven fabric composite and steel fiber reinforced concrete under uniaxial and biaxial fatigue loading. The boundary surface theory is used to describe the effect of biaxial fatigue loading. A fourth-order response tensor is used to reflect the high directionality of the damage development, and a second-order response tensor is used to describe the evolution of inelastic deformation due to damage. A direction function is used to capture the strength anisotropic property of the woven fabric composite. The comparisons between model prediction results and experimental data show the good prediction capability of models proposed in this dissertation.
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Bai, Gabriele. "Evaluation par vibrothermographie de l'endommagement de composites tissés". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0055/document.
Testo completoAbstract (sommario):
Ces travaux de thèse visent à l’application de techniques de vibrothermographie pour les matériaux composites tissés. Ces techniques, déjà développées et appliquées aux matériaux métalliques, sont basées sur la détection de l’échauffement généré dans un matériau mis en vibration en conséquence des effets viscoélastiques et des frottements des fissures. Dans la première partie du manuscrit, une technique de type CND est développée pour analyser l’endommagement diffus d’un composite tissé et pour déterminer une relation entre son état d’endommagement et son comportement thermique. Cette partie est aussi importante pour la compréhension des phénomènes qui gouvernent la vibrothermographie grâce à une première estimation des sources thermiques en jeu. Dans la deuxième partie, la vibrothermographie est appliquée à l’étude du comportement en fatigue et pour une estimation d’une limite de fatigue des composites tissés. Cette estimation diffère de l’approche mécanique classique reposant sur l’exploitation des courbes S-N parce qu’elle est effectuée en utilisant un seul échantillon et de manière beaucoup plus rapide. Elle pourra être utilisée pour mieux comprendre l’endommagement en fatigue des matériaux et pour aider les ingénieurs dans le dimensionnement des structures soumises à ce type de sollicitationThis work aims at applying vibrothermographic techniques to woven composite materials. These techniques, already developed and applied to metallic materials are based on the detection of the heating generated in a vibrating material by viscoelastic effects and friction of the crack surfaces. In the first part of the manuscript an NDT technique is developed to analyse the diffuse damage of a woven composite and to determine a relation between its damage state and its thermal behaviour. This part is important to understand the phenomena that govern vibrothermography with a first estimation of the thermal sources. In the second part, vibrothermography is applied to study the fatigue behaviour and to estimate a fatigue limit of woven composites. This estimation differs from the standard mechanical estimation based on the analysis of the S-N curves because it is carried out on a single, unique sample and over a much shorter duration. It may be used to improve the understanding of the fatigue damage of materials and to help engineers to design structures subjected to this kind of stress
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Yu, Bo. "Damage characterisation of 3D woven glass-fibre reinforced composites under fatigue loading using X-ray computed tomography". Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/damage-characterisation-of-3d-woven-glassfibrereinforced-composites-under-fatigue-loading-using-xraycomputed-tomography(e4d6ee91-e3f5-4b33-b9e7-4367cbbfcf0c).html.
Testo completoAbstract (sommario):
In the advanced polymer composites reinforced by 3D woven fibre architectures, tows areinterlaced into through-thickness direction to overcome the problems encountered in theapplications of traditional 2D laminates, such as poor interlaminar toughness anddelamination resistance. The understanding of the influence of fibre architectures on thefatigue performance of 3D woven composites is essential in providing guide for the designof fibre architecture. This PhD project is an in-depth study into the fatigue damagemechanisms of 3D woven composites reinforced by two kinds of fibre architectures,namely, 3D modified layer-to-layer (MLL) and 3D angle-interlocked (AI). 3D X-raycomputed tomography (CT) has been used as the main tool to non-destructively evaluateand quantify the evolution of fatigue damage, with an attempt to link macro behaviour withlocal micro (damage) microstructure. Part I is focused on a post-failure study on both typesof materials to identify their respective failure mechanism, using the combination of 2D(optical surface and SEM cross-sectional) imaging and 3D (X-ray CT) imaging. Somecharacteristic features are found in both materials: firstly, fatigue damage progresses by theinitiation of transverse cracks within weft yarns and subsequent propagation as interfacialdebonding crack until the catastrophic failure occurs in a localised area; secondly, bothmaterials display a high resistance to ultimate failure. However, a distinctive damage modeobserved in MLL composites is the extensive development of debonding cracks, whichresult in larger scale of damage (~10μm) than those in AI composites (1-2 μm). Part IIpresents an investigation of evolution of fatigue damage in 3D woven MLL compositesfollowed by an X-ray time-lapse experiment. An innovative algorithm was developed toenable automatic classification of damage, providing insight into the competition andinteraction of different damage modes. Fatigue damage is regularly distributed throughoutfatigue life, with a geometrical dependency on the repeating unit cells. Damageinteractions have been identified, indicating a high level of damage tolerance. Aquantitative analysis has been carried out to examine and compare the growth of differenttypes of damage as a function of fatigue cycles. Transverse cracks initiate at almost thebeginning the fatigue life (0.1%) and govern the growth of weft/binder debonds, but don’tcompromise fatigue life, whereas interply debonds have a large growth towards the end offatigue life and facilitate the ultimate failure. Other types of damage occurring in the resinhave a trivial effect on the fatigue life. Part III carries out a systematic study to find out thebest approach to detect the fatigue damage in the 3D AI composites. Different strategieshave been employed in each scan, including imaging the cracks with the load applied, withcontrast enhanced by phases contrast and staining. The image contrast was not effectivelyenhanced by applying phase contrast imaging, but significantly improved by staining. Withthe application of in-situ loading, the visibility of transverse cracks is highly improved,while longitudinal debonding cracks still cannot be resolved. Overall, the best approachwas found to be high resolution ROI (region of interest) scanning in combination withstaining, in terms of practical feasibility, scan time and image quality.
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Muller, Laura. "Estimation accélérée des performances en fatigue de matériaux et structures composites thermoplastiques par le suivi de leur auto-échauffement". Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0035/document.
Testo completoAbstract (sommario):
Cette thèse s’inscrit dans le domaine de la fatigue des matériaux composites. Elle consiste à estimer les performances en fatigue d’un matériau composite thermoplastique tissé, en fibres de carbone et matrice PA66, par des essais d’auto-échauffement. Suite à une caractérisation de l’endommagement du matériau sous chargement monotone par un suivi acoustique, thermique et optique, une campagne d’essais de fatigue est réalisée sur deux configurations du matériau, à 0° et à 45°. Plusieurs méthodes de modélisation de la courbe S-N sont proposées, afin de déterminer la limite de fatigue du matériau. Il est montré que l’estimation de cette limite et de son intervalle de confiance est rendue difficile par la forte dispersion des données expérimentales. Des essais d’auto-échauffement sont alors réalisés, consistant à appliquer un chargement de fatigue sur un nombre de cycles limité, en incrémentant la contrainte maximale appliquée palier après palier. Des outils de traitement du signal sont développés afin de déterminer une contrainte seuil et son intervalle de confiance à partir de laquelle l’échauffement s’accélère. Cependant, cette contrainte seuil reste conservative par rapport à la limite de fatigue.Une autre approche est alors développée, consistant à suivre les amplitudes du signal thermique. De nouveaux outils de traitement du signal sont développés, dans le but de réaliser des cartographies de l’éprouvette à partir des amplitudes des harmoniques. Il est alors montré qu’il est possible d’obtenir les mêmes courbes que les courbes d’auto-échauffement en réalisant un suivi des amplitudes des harmoniques, et ce pour une centaine de cycles seulement. Un nouveau protocole d’essai d’auto-échauffement est alors mis en place, fondé sur une centaine de paliers de quelques centaines de cycles seulement, permettant d’aboutir à un suivi des harmoniques avec des courbes finales quasi-continues en un minimum de tempsThis thesis is part of the study on the fatigue of composite materials. It consists in estimating the fatigue performance of a thermoplastic composite woven material, made of carbon fibres and PA66 matrix, by self-heating tests. Following a characterization of the damage to the material under monotonous loading by acoustic, thermal and optical monitoring, a fatigue test campaign is carried out on two material configurations, at 0° and 45°. Several methods for modelling the S-N curve are proposed to determine the fatigue limit of the material. It is shown that the estimation of this limit and its confidence interval is complicated by the large dispersion of experimental data. Self-heating tests are then carried out, consisting of applying a fatigue load over a limited number of cycles, increasing the maximum stress applied step by step. Signal processing tools are developed to determine a threshold stress and its confidence interval at which the heating accelerates. However, this threshold stress remains conservative in comparison to the fatigue limit. Another approach is then developed, consisting in monitoring the amplitudes of the thermal signal. New signal processing tools are being developed to map the specimen from the harmonic amplitudes. It is then shown that it is possible to obtain the same curves as the selfheating curves by monitoring the amplitudes of the harmonics, and this for only a hundred cycles. A new self-heating test protocol is then implemented, based on a hundred steps of only a few hundred cycles, allowing harmonics to be monitored with almost continuous final curves in a minimum of time
47
Rouault, Thomas. "Propagation de coupure en fatigue sur composites tissés – Etude expérimentale et modélisation". Thesis, Toulouse, ISAE, 2013. http://www.theses.fr/2013ESAE0018/document.
Testo completoAbstract (sommario):
Les pales d’hélicoptère sont des structures composites soumises à un chargement cyclique multiaxial, et leur criticité impose de porter une attention particulière à la tolérance aux dommages. Leur revêtement peut potentiellement présenter des criques suite à certains évènements (impact, défaut, foudre). Ces travaux se focalisent sur un matériau de revêtement donné (tissu de verre) et concernent l’étude de la propagation de coupure (crique) sous chargement cyclique. Les sollicitations de service ont amené à considérer la traction et le cisaillement plan. Une étude expérimentale a été menée afin d’étudier les modes d’endommagement du matériau et sa résistance à la propagation de coupure pour différentes sollicitations (en traction et en cisaillement) et pour les drapages les plus courants. Elle a permis de dégager les mécanismes d’endommagement mis en jeu, et a fourni un ensemble important de propriétés matériau et de données quantitatives de vitesse de propagation. Elle a par ailleurs guidé vers une modélisation par éléments finis adaptée à l’architecture du matériau, et la manière dont il se dégrade en fatigue. Ce modèle repose sur un maillage à l’échelle de la mèche, et la prédiction de la propagation est obtenue par l’utilisation d’une courbe de fatigue S-N. La simulation a été évaluée par comparaison des faciès de rupture, des vitesses de propagation et de l’étendue des zones d’endommagement avec les essais réalisés sur éprouvettesHelicopter blades consist of composite structures which have to sustain multi-axial cyclic loading. Because of their criticality, damage tolerance has to be considered carefully. Their skin is subjected to environmental events like impact, flaw, lightning which can cause through-thethickness cracks. The present work focuses on one given skin material (woven glass fabric) and concerns the study of the through-the-thickness crack growth under cyclic loading. In-flight loading lead to consider tension and shear. An experimental study has been carried out to study damage in the material and its crackgrowth resistance under different loadings (tension and shear) and for usual stacking sequences. It highlighted damage mechanisms and provided an important set of material data and crack growth speeds. Besides, this led to a finite element approach adapted to the woven fabric architecture, anddamage feature under fatigue loading. This modeling is based on a bundle scale mesh, a semidiscrete damage modeling and an S-N curve to predict fiber failure. Numerical simulations of crack growth tests were carried out, and results were compared with experiments in terms of crack direction, crack growth speed, and size of damaged area
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Barbière, Romain. "Comportement en fatigue et optimisation de l’interface d’un composite tissé chanvre/époxy : effet de l’humidité Influence of moisture and drying on fatigue damage mechanisms in a woven hemp/epoxy composite : acoustic emission and micro-CT analysis". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0016.
Testo completoAbstract (sommario):
Les composites à renfort d’origine végétale constituent une alternative écologique aux matériaux composites traditionnels tels que les composites à fibres de verre. Cependant, les renforts d’origine végétale sont fortement hydrophiles par rapport à la matrice polymère. Il est donc nécessaire d’étudier l’influence de l’eau sur le comportement mécanique de ces éco-matériaux.Dans ce travail, trois conditionnements ont été mis en place. Le conditionnement Ambiant correspond à l’étude du composite en environnement ambiant : stockage et essais à l’ambiante. Le conditionnement Eau permet d’étudier les échantillons dans des conditions extrêmes d’humidité : les éprouvettes sont saturées en eau puis testées dans une enceinte saturée en humidité. Le conditionnement Séché a pour objectif d’étudier le rôle de la désorption sur les propriétés mécaniques du composite. Des éprouvettes de composite tissé chanvre/époxy de deux orientations, [(0/90)]7 et [(±45)]7, ont été testées en traction et en fatigue suivant les trois conditionnements. Des analyses in situ par émission acoustique et post-mortem par MEB et microtomographie ont été réalisées.Les essais de fatigue ont permis d’établir les courbes de Wöhler pour les deux orientations et les trois conditionnements. Un modèle phénoménologique a été utilisé pour modéliser la durée de vie du composite dans toutes les configurations. Les comparaisons montrent que le conditionnement Eau a une sensibilité à la fatigue plus faible que les conditionnements Ambiant et Séché. La classification des évènements acoustiques a permis d’identifier trois classes correspondant chacune à un type d’endommagement (endommagement matriciel, endommagement interfacial et rupture de fibres). Pour les deux orientations, les résultats ont montré que la proportion en nombre et la cinétique d’apparition de chaque type d’endommagement dépendent du niveau de contrainte maximale appliquée et du type de conditionnement, les endommagements matriciels et interfaciaux étant toujours largement majoritaires. L’analyse microtomographique a montré que les endommagements sont différents selon l’orientation. Cependant, pour chaque orientation, on retrouve le même type d’endommagement pour les trois conditionnements, à différents stades de développement : plus avancé pour le conditionnement Eau, intermédiaire pour le Séché et le moins développé pour l’Ambiant.Pour analyser l’adhésion à l’interface fil/matrice, des tests de fragmentation ont été réalisés sur des éprouvettes monofilamentaires chanvre/époxy. Un moule spécifique a été conçu et développé pour réaliser ces éprouvettes par coulée. Un suivi par émission acoustique couplé à des observations en lumière polarisée a permis de mieux comprendre le phénomène de fragmentation dans ce type d’éprouvettes. Les valeurs de la contrainte maximale de cisaillement à l’interface fil/matrice (IFSS) ont été calculées et les longueurs de décohésion interfaciale ont été mesurées. Les résultats montrent que l’interface fil/matrice est affaiblie après séchage, avec une diminution de l’IFSS de 33%. Pour améliorer l’adhésion à l’interface, un traitement au peroxyde d’hydrogène et un traitement par plasma froid ont été appliqués au renfort de chanvre. Les tests de fragmentation montrent que l’IFSS est presque deux fois plus élevée avec le traitement au peroxyde et trois fois plus avec le plasma, par rapport aux éprouvettes non traitées. Un changement d’échelle a ensuite été effectué en appliquant le traitement au peroxyde d’hydrogène sur le tissu de chanvre. Le comportement en traction et en fatigue des composites chanvre/époxy élaborés avec ce tissu traité a été étudié. Les résultats obtenus à cette échelle ne sont pas satisfaisants. Le traitement par plasma reste donc la voie la plus prometteuse, mais appliquer cette technique à l’échelle d’un tissu est complexe et nécessite de mettre au point un nouveau réacteurPlant fibre composites are an environmentally friendly alternative to traditional composite materials such as fibreglass composites. However, plant fibres are highly hydrophilic in comparison with the polymer matrix. It is therefore necessary to study the influence of moisture on the mechanical behaviour of these eco-materials.In this work, three conditionings were applied. “Ambient” samples were stored and tested in ambient environment. “Wet” samples were immersed in water until saturation and tested in a climatic chamber at RH97. The objective of the “Wet/Dry” conditioning was to study the role of desorption on the mechanical properties of the composite. Woven hemp/epoxy composite samples with two orientations, [(0/90)]7 and [(± 45)]7, were tested in tension and fatigue according to the three conditionings. In situ analyses by acoustic emission and post-mortem analyses by SEM and micro-CT were carried out.Fatigue tests allowed to determine the Wöhler curves for the two orientations and the three conditionings. A phenomenological model was used to simulate the fatigue life of the composite in all configurations. The comparisons showed that the Wet samples exhibit a lower tensile strength than the Ambient specimens and a lower fatigue sensitivity, while the behaviour of the Wet/dry samples is similar to the Wet conditioning one concerning the tensile strength and similar to the Ambient one concerning the fatigue sensitivity. The classification of acoustic events allowed the identification of three clusters, each cluster corresponding to a type of damage (matrix damage, interfacial damage and fibre breakage). For the two orientations, the results showed that the proportion in number and the kinetics of development of each type of damage depend on the level of the maximum applied stress and on the conditioning. Matrix and interfacial damages are largely the most numerous acoustic events for all the configurations. Micro-CT analysis showed that the damage is different depending on the orientation. However, for each orientation, the same type of damage is observed for the three conditionings, at different stages of development: more advanced for the Wet conditioning, intermediate for the Wet/Dry one and the least developed for the Ambient one.The analysis of the yarn/matrix interface adhesion was performed through fragmentation tests realised on monofilament hemp/epoxy specimens. A specific mould was designed and developed to produce these specimens by casting. Acoustic emission monitoring and observations in polarized light allowed a better understanding of the fragmentation phenomenon in this type of material. The Interfacial Shear Strength (IFSS) values were calculated and the interfacial debonding lengths were measured. The results show that the yarn/matrix interface is weakened after drying, with a decrease in IFSS of 33%. To improve adhesion at the interface, treatments with hydrogen peroxide and non-thermal plasma were applied to the hemp yarns. Fragmentation tests showed that IFSS is almost twice as high with the peroxide treatment and three times higher with plasma, compared to untreated specimens. An upscale was made by applying the hydrogen peroxide treatment to the hemp fabric. The tensile and fatigue behaviour of hemp/epoxy composites produced with this treated fabric was studied. The results obtained at this scale are disappointing. Therefore, the non-thermal plasma treatment remains the most promising solution, but applying this technique at the fabric scale is complex and requires the development of a new reactor
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Ben, Toumi Rim. "Endommagement par fatigue et durée de vie de structures en matériaux composites à fibres continues pour application liaison au sol". Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0064.
Testo completoAbstract (sommario):
L'allègement des véhicules est un enjeu majeur de l'industrie automobile pour participer, avec l'évolution des motorisations, à la maîtrise des consommations énergétiques et la réduction des émissions de gaz à effet de serre. Dans ce travail, nous nous intéressons à l'introduction des matériaux composites dans les pièces de structure et particulièrement dans le périmètre de la liaison au sol composé d'organes de sécurité active, sujets au phénomène de fatigue multi axiale à grand nombre de cycles.Les matériaux composites présentent une solution séduisante en raison de leurs propriétés mécaniques intéressantes combinées à une faible densité. Toutefois, la fatigue des matériaux composites reste un sujet complexe relativement peu abordé. C'est dans ce cadre que s'inscrit cette thèse qui vise à mettre en place une méthodologie de dimensionnement des composants automobiles de structure, à partir d'un composite tissé verre/époxy. Cette méthodologie s'attache à être facile d'utilisation et adaptable au calcul de structure pour être applicable en Bureau d'Études. La première étape de cette étude est la caractérisation de la tenue en service du matériau sous chargements monotones et cycliques et l'identification des cinétiques d'endommagement. Au vu des résultats expérimentaux obtenus et à partir des approches de dimensionnement existantes, un critère de fatigue multi axiale est proposé. Ensuite, une optimisation du protocole d'identification des paramètres est effectuée afin de réduire au minimum le volume des campagnes d'essais. Enfin, le critère mis en place pour évaluer la durée de vie en fatigue du matériau composite tissé est validé sur des éprouvettes trouées et sur le train avant à lame compositeThe reduction of fuel consumption and greenhouse gas emissions is one of the most important challenges facing the automotive industry. An efficient strategy to meet these targets is by reducing the weight of vehicle. In this work, we are interested in introducing composite materials in automotive structural parts and especially in suspensions which are subjected in service to high-cycle fatigue loadings. Therefore, a good prediction of fatigue life is required. As continuous fibre-reinforced composites provide good mechanical properties combined with a low density, they have been increasingly used in many lightweight structures. However, the fatigue behaviour of composites has not been widely investigated. This work aims at developing an approach to predict the lifetime in service of structural automotive components, made with woven glass / epoxy composite. This approach has to be easy to use by design engineers at the scale of the structure. The first step is the characterization of the material. Then, the processes involved in degradation of the composite subjected to both monotonic and cyclic loadings were identified.Given the experimental results and the existing approaches, a multiaxial fatigue criterion is proposed. An optimization of the identification protocol is also performed to reduce the quantity of needed experimental data. Finally, the fatigue life prediction model criterion is validated by tests on notched coupons and on composite vehicle's suspension
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Malpot, Amélie. "Etude du comportement en fatigue d’un composite à matrice polyamide renforcé d'un tissu de fibres de verre pour application automobile". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2017. http://www.theses.fr/2017ESMA0002/document.
Testo completoAbstract (sommario):
Ces travaux de thèse portent sur un composite à matrice polyamide 6,6 (PA66) renforcé d’un tissu de fibres de verre (Sergé 2/2). Dans le but d’une intégration dans des pièces automobiles, on s’intéresse au comportement de ce matériau sous sollicitation cyclique. L’objectif est de mettre au point un critère de fatigue permettant de prédire la durée de vie du composite étudié. Le PA66 étant sensible à l’humidité, il est nécessaire de prendre en compte ce paramètre dans notre étude. Pour cela, le matériau est conditionné selon trois états : un état sec (RH0), un état ambiant (RH50) et un état saturé en eau(RH100). Trois séquences d’empilement sont également considérées afin de tenir compte de l’orientation des fibres dans le matériau : [(0/903], [(90/0)3] et [(±45)3]. Dans un premier temps, l’influence du conditionnement sur les propriétés microstructurales et mécaniques en traction monotone est étudiée.Le rôle plastifiant de l’eau sur le PA66 a été mis en évidence. L’instrumentation des essais de traction monotone avec un système d’émission acoustique associée à l’observation post-mortem par MEB des éprouvettes permet de proposer un scénario d’endommagement en traction quasi-statique pour chaque configuration étudiée. Dans un deuxième temps, une campagne d’essais en fatigue traction-traction est menée sur les neuf configurations de l’étude. Ces essais ont permis la mise en place et l’évaluation de deux critères de fatigue phénoménologiques : les diagrammes de durées de vie constantes et le critère de fatigue à deux paramètres basé sur les courbes S-N. Ce dernier a été enrichi afin de pouvoir prédire la durée de vie du matériau pour différents conditionnements. De manière générale, le modèle montre une bonne capacité à prédire la durée de vie du matériau pour des conditions d’essais variées. Afin de cerner la capacité du modèle à être utilisé en bureau d’études, celui-ci a été appliqué dans le cas d’essais de fatigue menés sur une mini-structure sollicitée en flexion 3 pointsThis study is focused on a woven glass-fibre-reinforced composite (2/2 twill) with a polyamide 6,6 matrix. From the perspective of its future integration in automotive parts, the fatigue behavior of this material is investigated. The aim is to develop a fatigue model able to predict the fatigue life of the composite studied. The PA66 behaviour is highly influenced by the moisture content, thus, it is necessary to take this parameter into account. Hence, three conditionings are studied: RH0, RH50 andRH100 which correspond respectively to the dry-as-moulded, the ambient and the water-saturated state.Three different stacking sequences are used in order to study the influence of fibre orientation: [(0/90)3],[(90/0)3] and [(±45)3]. First, the influence of moisture on microstructural and mechanical properties formonotonic tensile tests is studied. The plasticizing effect of water on PA66 has been highlighted. A damage scenario has been determined for every configuration studied by using acoustic emission technique during monotonic tensile tests and post-mortem SEM observations. Then, tension-tension fatigue tests are performed for all sample configurations. The results have been used to set up two phenomenological fatigue life models: the constant life diagrams and the two-parameter model based onS-N curves. The latter has been enhanced by including the relative humidity in order to be able to predict the fatigue life of the material for any conditioning. In general, this model estimates quite well the fatigue life of the material for different testing conditions. Finally, the two-parameter model has been used for fatigue life prediction of both open-hole samples and a mini-structure in order to evaluate its capability to be used in an industrial context