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Maria Kashtalyan - One of the best experts on this subject based on the ideXlab platform.
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Analysis of delamination in laminates with angle-ply matrix cracks: Onset of damage and residual stiffness properties
Structural Integrity and Durability of Advanced Composites, 2015Co-Authors: Maria Kashtalyan, Constantinos SoutisAbstract:Abstract The failure process of composite laminate under quasi-static or fatigue loading involves sequential accumulation of intra- and interlaminar cracking. Matrix cracking parallel to the fibres in the off-axis plies is the first damage mode observed. It triggers development of other harmful resin-dominated modes such as delaminations. In this chapter, analytical modelling of crack-induced delaminations in composite laminates subjected to general in-plane loading is presented and discussed. A two-dimensional shear lag analysis is used to determine ply stresses in a Representative Segment and the equivalent laminate concept is applied to derive expressions for mode I and mode II and the total strain energy release rate associated with uniform local delaminations. These expressions could be used with appropriate fracture criteria to estimate the onset of local delamination in an already cracked off-axis laminate. Dependence of strain energy release rate on crack density, delamination area and ply orientation angle in unbalanced symmetric laminates is examined and discussed, and the effect of crack-induced delamination on the laminate stiffness is predicted.
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Modelling off-axis ply matrix cracking in continuous fibre-reinforced polymer matrix composite laminates
Journal of Materials Science, 2006Co-Authors: Maria Kashtalyan, Constantinos SoutisAbstract:The fracture process of composite laminates subjected to static or fatigue tensile loading involves sequential accumulation of intra- and interlaminar damage, in the form of transverse cracking, splitting and delamination, prior to catastrophic failure. Matrix cracking parallel to the fibres in the off-axis plies is the first damage mode observed. Since a damaged lamina within the laminate retains certain amount of its load-carrying capacity, it is important to predict accurately the stiffness properties of the laminate as a function of damage as well as progression of damage with the strain state. In this paper, theoretical modelling of matrix cracking in the off-axis plies of unbalanced symmetric composite laminates subjected to in-plane tensile loading is presented and discussed. A 2-D shear-lag analysis is used to determine ply stresses in a Representative Segment and the equivalent laminate concept is applied to derive expressions for Mode I, Mode II and the total strain energy release rate associated with off-axis ply cracking. Dependence of the degraded stiffness properties and strain energy release rates on the crack density and ply orientation angle is examined for glass/epoxy laminates. Suitability of a mixed mode fracture criterion to predict the cracking onset strain is also discussed.
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Analysis of local delaminations in composite laminates with angle-ply matrix cracks
International Journal of Solids and Structures, 2002Co-Authors: Maria KashtalyanAbstract:Abstract In this paper, local delaminations growing uniformly from the tips of angle-ply matrix cracks in composite laminates loaded in tension are modelled theoretically. A 2-D shear lag method is used to determine stresses in a laminate Representative Segment containing one crack and two crack tip delaminations. For the calculation of the strain-energy release rate (SERR) associated with delaminations, the damaged layer is replaced with an equivalent homogeneous one with effective elastic properties. Closed-form expressions for the total SERR and its mode I and mode II components as a linear function of the first partial derivatives of the effective elastic properties of the damaged layer with respect to delamination area are derived. Dependence of SERRs and the laminate stiffness properties on delamination area, crack density and ply orientation angle is examined for balanced [0 2 /θ 2 /− θ 2 ] s and unbalanced [0 2 /θ 2 ] s carbon/epoxy laminates. The total SERR obtained in this study is compared to a simple closed-form expression for a uniform local delamination derived in earlier work by O'Brien (Local delamination in laminates with angle-ply matrix cracks: Part II Delamination Fracture Analysis and Fatigue Characterization. NASA Technical Memorandum 104076/AVSCOM Technical Report 91-B-011). It appears that matrix crack density and delamination size influence the SERR value significantly.
Constantinos Soutis - One of the best experts on this subject based on the ideXlab platform.
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Analysis of delamination in laminates with angle-ply matrix cracks: Onset of damage and residual stiffness properties
Structural Integrity and Durability of Advanced Composites, 2015Co-Authors: Maria Kashtalyan, Constantinos SoutisAbstract:Abstract The failure process of composite laminate under quasi-static or fatigue loading involves sequential accumulation of intra- and interlaminar cracking. Matrix cracking parallel to the fibres in the off-axis plies is the first damage mode observed. It triggers development of other harmful resin-dominated modes such as delaminations. In this chapter, analytical modelling of crack-induced delaminations in composite laminates subjected to general in-plane loading is presented and discussed. A two-dimensional shear lag analysis is used to determine ply stresses in a Representative Segment and the equivalent laminate concept is applied to derive expressions for mode I and mode II and the total strain energy release rate associated with uniform local delaminations. These expressions could be used with appropriate fracture criteria to estimate the onset of local delamination in an already cracked off-axis laminate. Dependence of strain energy release rate on crack density, delamination area and ply orientation angle in unbalanced symmetric laminates is examined and discussed, and the effect of crack-induced delamination on the laminate stiffness is predicted.
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Modelling off-axis ply matrix cracking in continuous fibre-reinforced polymer matrix composite laminates
Journal of Materials Science, 2006Co-Authors: Maria Kashtalyan, Constantinos SoutisAbstract:The fracture process of composite laminates subjected to static or fatigue tensile loading involves sequential accumulation of intra- and interlaminar damage, in the form of transverse cracking, splitting and delamination, prior to catastrophic failure. Matrix cracking parallel to the fibres in the off-axis plies is the first damage mode observed. Since a damaged lamina within the laminate retains certain amount of its load-carrying capacity, it is important to predict accurately the stiffness properties of the laminate as a function of damage as well as progression of damage with the strain state. In this paper, theoretical modelling of matrix cracking in the off-axis plies of unbalanced symmetric composite laminates subjected to in-plane tensile loading is presented and discussed. A 2-D shear-lag analysis is used to determine ply stresses in a Representative Segment and the equivalent laminate concept is applied to derive expressions for Mode I, Mode II and the total strain energy release rate associated with off-axis ply cracking. Dependence of the degraded stiffness properties and strain energy release rates on the crack density and ply orientation angle is examined for glass/epoxy laminates. Suitability of a mixed mode fracture criterion to predict the cracking onset strain is also discussed.
Chijen Wang - One of the best experts on this subject based on the ideXlab platform.
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Representative Segment based emotion analysis and classification with automatic respiration signal Segmentation
IEEE Transactions on Affective Computing, 2012Co-Authors: Pauchoo Chung, Chijen WangAbstract:Human respiration has been reported as having great relevance to the emotional state. However, the respiration signal obtained using traditional biosensors not only reflects changing emotions and emotion intensities, but also contains motion artifacts. The resulting information ambiguity limits the practical application of the respiration signal as a means of reliable affective state appraisal. Thus, the present study proposes a method for extracting Representative Emotion Elicited Segments (EESs) from the respiration signal such that the affective state of the individual can be more reliably determined. The EES extraction process involves the combination of the following procedures, namely, 1) Mutual Information-Based Emotion Relevance Feature Ranking based on the Dynamic Time Warping Distance (MIDTW), and 2) Constraint-based Elicited Segment Density (CESD) analysis. Due to the innate regularity of the respiration signal, the respiration pattern under a particular emotional state would be relatively quasihomogeneous over time. Accordingly, a parameter-free Respiration quasi-Homogeneity Segmentation (RHS) algorithm is proposed for partitioning the respiration signal into quasi-homogenous Segments from which the EESs can then be extracted. The experimental results obtained for five prototypical emotions (i.e., “love,” “sadness,” “joy,” “anger,” and “fear”) show that the proposed Segmentation/extraction methodology enables the EESs to be reliably identified and yields an average classification rate of 88 percent.
Pauchoo Chung - One of the best experts on this subject based on the ideXlab platform.
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Representative Segment based emotion analysis and classification with automatic respiration signal Segmentation
IEEE Transactions on Affective Computing, 2012Co-Authors: Pauchoo Chung, Chijen WangAbstract:Human respiration has been reported as having great relevance to the emotional state. However, the respiration signal obtained using traditional biosensors not only reflects changing emotions and emotion intensities, but also contains motion artifacts. The resulting information ambiguity limits the practical application of the respiration signal as a means of reliable affective state appraisal. Thus, the present study proposes a method for extracting Representative Emotion Elicited Segments (EESs) from the respiration signal such that the affective state of the individual can be more reliably determined. The EES extraction process involves the combination of the following procedures, namely, 1) Mutual Information-Based Emotion Relevance Feature Ranking based on the Dynamic Time Warping Distance (MIDTW), and 2) Constraint-based Elicited Segment Density (CESD) analysis. Due to the innate regularity of the respiration signal, the respiration pattern under a particular emotional state would be relatively quasihomogeneous over time. Accordingly, a parameter-free Respiration quasi-Homogeneity Segmentation (RHS) algorithm is proposed for partitioning the respiration signal into quasi-homogenous Segments from which the EESs can then be extracted. The experimental results obtained for five prototypical emotions (i.e., “love,” “sadness,” “joy,” “anger,” and “fear”) show that the proposed Segmentation/extraction methodology enables the EESs to be reliably identified and yields an average classification rate of 88 percent.
Cecile Bensimon - One of the best experts on this subject based on the ideXlab platform.
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acceptable limitations on paramedic duty to treat during disaster a qualitative exploration
Prehospital and Disaster Medicine, 2018Co-Authors: Erin Smith, Frederick M Burkle, Kristine M Gebbie, David Ford, Cecile BensimonAbstract:Introduction The Australian prehospital profession has not yet facilitated a comprehensive discussion regarding paramedic role and responsibility during disasters. Whether paramedics have a duty to treat under extreme conditions and what acceptable limitations may be placed on such a duty require urgent consideration. The purpose of this research is to encourage discussion within the paramedic profession and broader community on this important ethical and legal issue. Methods The authors employed qualitative methods to gather paramedic and community member perspectives in Victoria, Australia. Results These findings suggested that both paramedic and community member participants agree that acceptable limitations on paramedic duty to treat during disaster are required. These limitations should be based on consideration of the following factors: personal health circumstances (eg, pregnancy for female paramedics); pre-existing mental health conditions (eg, posttraumatic stress disorder/PTSD); competing personal obligations (eg, paramedics who are single parents); and unacceptable levels of personal risk (eg, risk of exposure and infection during a pandemic). Conclusion It is only with the engagement of a more broadly Representative Segment of the prehospital profession and greater Australian community that appropriate guidance on limiting standards of care under extreme conditions can be developed and integrated within prehospital care in Australia. Smith E , Burkle FM Jr ., Gebbie K , Ford D , Bensimon C . Acceptable Limitations on Paramedic Duty to Treat During Disaster: A Qualitative Exploration . Prehosp Disaster Med . 2018 ; 33 ( 5 ): 466 – 470 .