Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25303
C. S. Yerramalli, A. Waas
The response of polymer matrix composites under combined proportional axial and torsional loading has been studied. Experiments were performed on solid cylindrical specimens of glass/vinylester and carbon/vinylester composites at a fiber volume fraction, Vf equal to 50%. The specimens were loaded under displacement and rotation control in a proportional manner. The Budiansky-Fleck kinking model was specialized to the case of a solid cylindrical specimen and the predictions were compared to the experimental results. It was found that the compression strength of carbon composites is approximately a linear function of the applied rotation but in the case of glass composites the compression strength is initially unaffected due to shear. At a critical value of shear, the compression strength is seen to diminish rapidly. This suggests that the Budiansky-Fleck model might not be suitable for predicting the effect of shear on compression strength of glass fiber composites.
{"title":"Failure of Composites Under Combined Loading","authors":"C. S. Yerramalli, A. Waas","doi":"10.1115/imece2001/ad-25303","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25303","url":null,"abstract":"\u0000 The response of polymer matrix composites under combined proportional axial and torsional loading has been studied. Experiments were performed on solid cylindrical specimens of glass/vinylester and carbon/vinylester composites at a fiber volume fraction, Vf equal to 50%. The specimens were loaded under displacement and rotation control in a proportional manner. The Budiansky-Fleck kinking model was specialized to the case of a solid cylindrical specimen and the predictions were compared to the experimental results. It was found that the compression strength of carbon composites is approximately a linear function of the applied rotation but in the case of glass composites the compression strength is initially unaffected due to shear. At a critical value of shear, the compression strength is seen to diminish rapidly. This suggests that the Budiansky-Fleck model might not be suitable for predicting the effect of shear on compression strength of glass fiber composites.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116211636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25315
V. Jadhav, S. Sridharan
Micromechanical models with different representative volume elements have been developed to study their ability to predict nonlinear response of unidirectional composites. A simple, square cells type micro-mechanical model similar to those widely used by other researchers is compared with a more advanced 3-phase finite element based micro-mechanical model. The models utilize the “bulk” properties of the matrix without attempting to “tune” the model to fit with experimental response of laminae. This is a more fundamental approach and constitutes a departure from current practice. The models account for shear softening, matrix cracking and the presence of residual stresses. A smeared cracking approach was used to characterize the micro-cracking in matrix. Experimental studies were performed on laminae, laminates and cylinders made from carbon epoxy composites. Experimental comparisons show that the more accurate micro-mechanical model with proper partial cracking options provides good bounds on experimental response with consistent accuracy. A square cells type model however is not consistent in its predictions, thus raising questions about its applicability in any general micro-mechanics based analysis.
{"title":"Micromechanical Analysis of Nonlinear Response of Unidirectional Composites: A Fundamental Approach","authors":"V. Jadhav, S. Sridharan","doi":"10.1115/imece2001/ad-25315","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25315","url":null,"abstract":"\u0000 Micromechanical models with different representative volume elements have been developed to study their ability to predict nonlinear response of unidirectional composites. A simple, square cells type micro-mechanical model similar to those widely used by other researchers is compared with a more advanced 3-phase finite element based micro-mechanical model. The models utilize the “bulk” properties of the matrix without attempting to “tune” the model to fit with experimental response of laminae. This is a more fundamental approach and constitutes a departure from current practice. The models account for shear softening, matrix cracking and the presence of residual stresses. A smeared cracking approach was used to characterize the micro-cracking in matrix. Experimental studies were performed on laminae, laminates and cylinders made from carbon epoxy composites. Experimental comparisons show that the more accurate micro-mechanical model with proper partial cracking options provides good bounds on experimental response with consistent accuracy. A square cells type model however is not consistent in its predictions, thus raising questions about its applicability in any general micro-mechanics based analysis.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115305145","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25325
E. Jordan, W. Xie, M. Gell, L. Xie, F. Tu, K. Pattipati, P. Willett, Y. Sohn
Non-destructive determination of the remaining life of coatings of gas turbine parts is highly desirable. The present paper describes early attempts to prove the feasibility of doing this based on the optical measurement of the stress in the oxide that attaches the coating to the metal component. Both regression methods and neural network methods are compared and it was found that the neural network approach was superior for the case where multiple signal features were present. All methods provide useful predictions for the idealized case considered. Challenges presented by more complicated thermal cycles are discussed briefly.
{"title":"Prediction of Remaining Life Time Based on Measurements of Stress for Thermal Barrier Coatings","authors":"E. Jordan, W. Xie, M. Gell, L. Xie, F. Tu, K. Pattipati, P. Willett, Y. Sohn","doi":"10.1115/imece2001/ad-25325","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25325","url":null,"abstract":"\u0000 Non-destructive determination of the remaining life of coatings of gas turbine parts is highly desirable. The present paper describes early attempts to prove the feasibility of doing this based on the optical measurement of the stress in the oxide that attaches the coating to the metal component. Both regression methods and neural network methods are compared and it was found that the neural network approach was superior for the case where multiple signal features were present. All methods provide useful predictions for the idealized case considered. Challenges presented by more complicated thermal cycles are discussed briefly.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127816028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25304
L. Berhan, C. Wang, A. M. Sastry
Several promising Li-ion technologies incorporate micro- and nanoarchitectured carbon networks, typically in the form of whisker/particle blends bonded with thermoplastic binders, in the electrodes. Degradation of these battery electrode materials is currently a persistent problem, with damage presenting as blistering and/or delamination. We are investigating bonding in micro- and nanostructured materials in order to predict onset of this degradation of these stochastic materials. Here, we describe a general methodology in modeling the small junctures in these porous network materials. We have found previously that the joint properties are the controlling feature in a significant class of materials, and suggest that 3D simulations on the bonds may be used in 2D simulations of overall network behavior.
{"title":"Damage Initiation in Bonded Particulate Networks: 3D Simulations","authors":"L. Berhan, C. Wang, A. M. Sastry","doi":"10.1115/imece2001/ad-25304","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25304","url":null,"abstract":"\u0000 Several promising Li-ion technologies incorporate micro- and nanoarchitectured carbon networks, typically in the form of whisker/particle blends bonded with thermoplastic binders, in the electrodes. Degradation of these battery electrode materials is currently a persistent problem, with damage presenting as blistering and/or delamination. We are investigating bonding in micro- and nanostructured materials in order to predict onset of this degradation of these stochastic materials. Here, we describe a general methodology in modeling the small junctures in these porous network materials. We have found previously that the joint properties are the controlling feature in a significant class of materials, and suggest that 3D simulations on the bonds may be used in 2D simulations of overall network behavior.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"17 9","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133754515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25327
R. Loutfy, E. Wexler
Experimental study has been carried out to investigate thermal protection properties of thin fullerene coatings subjected to external heating. It was shown that due to low thermal conductivity and high emissivity, micron-scale fullerene films were capable of withstanding elevated temperatures (up to 800°C) resulting in over 100°C temperature decrease on the “cold” surface of the underlying substrate. Based on obtained results, practically important recommendations are made.
{"title":"Novel Concept of Advanced Thermal Protection Coating Based on Fullerenes","authors":"R. Loutfy, E. Wexler","doi":"10.1115/imece2001/ad-25327","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25327","url":null,"abstract":"\u0000 Experimental study has been carried out to investigate thermal protection properties of thin fullerene coatings subjected to external heating. It was shown that due to low thermal conductivity and high emissivity, micron-scale fullerene films were capable of withstanding elevated temperatures (up to 800°C) resulting in over 100°C temperature decrease on the “cold” surface of the underlying substrate. Based on obtained results, practically important recommendations are made.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115270568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25322
S. Sridharan, E. Jordan, M. Gell
Cr3+ photoluminescence peizo-spectroscopy (CPLPS) is a technique that allows the measurement of the hydrostatic component of stress in α alumina oxides. This method is being developed in our laboratory as a non-destructive inspection technique for thermal barrier coating systems. It has been shown that the Cr3+ concentration influences the magnitude of the shifts in the fluorescence frequencies, Δv of the R1 and the R2 peaks [1,2] and hence the apparent stress. Therefore, this work is an attempt to quantify the extent of this shift, consequent to the Cr3+ concentration in the TBC systems and to study the variation of this effect with thermal cycles on the TBCs. In addition, we have developed a method of estimating Cr3+ content based on the intensity of satellite peaks referred to as n-lines. The experiments are also designed to validate the n-line based method of estimating Cr3+ content and its affect on the apparent stress value.
{"title":"Calibration of Laser Piezospectroscopy Using Alumina/Chromia Solid Solutions Obtained by Coprecipitation","authors":"S. Sridharan, E. Jordan, M. Gell","doi":"10.1115/imece2001/ad-25322","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25322","url":null,"abstract":"\u0000 Cr3+ photoluminescence peizo-spectroscopy (CPLPS) is a technique that allows the measurement of the hydrostatic component of stress in α alumina oxides. This method is being developed in our laboratory as a non-destructive inspection technique for thermal barrier coating systems. It has been shown that the Cr3+ concentration influences the magnitude of the shifts in the fluorescence frequencies, Δv of the R1 and the R2 peaks [1,2] and hence the apparent stress. Therefore, this work is an attempt to quantify the extent of this shift, consequent to the Cr3+ concentration in the TBC systems and to study the variation of this effect with thermal cycles on the TBCs. In addition, we have developed a method of estimating Cr3+ content based on the intensity of satellite peaks referred to as n-lines. The experiments are also designed to validate the n-line based method of estimating Cr3+ content and its affect on the apparent stress value.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117268697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25310
D. Kedlaya, A. Pelegri
An analytical model, backed by numerical simulation, describing the behavior of the energy release rate of composite laminates subjected to fatigue overloads is presented. The model establishes that accumulation of damage due to intermittent surge in applied load reduces the energy release rate, G, of the material. Thus, in the case of cyclic loading with overloads, it is essential to model the failure using a damage growth law that incorporates the damage accumulation due to the overloads. The results obtained in this study, have no restrictive assumptions regarding the specimen or the delamination thickness, T and h respectively, and are presented over varying mode-mixity and h/T ratios.
{"title":"Failure Prediction of Graphite/Epoxy Laminates With Induced Intermittent Surge in Applied Load During Fatigue","authors":"D. Kedlaya, A. Pelegri","doi":"10.1115/imece2001/ad-25310","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25310","url":null,"abstract":"\u0000 An analytical model, backed by numerical simulation, describing the behavior of the energy release rate of composite laminates subjected to fatigue overloads is presented. The model establishes that accumulation of damage due to intermittent surge in applied load reduces the energy release rate, G, of the material. Thus, in the case of cyclic loading with overloads, it is essential to model the failure using a damage growth law that incorporates the damage accumulation due to the overloads. The results obtained in this study, have no restrictive assumptions regarding the specimen or the delamination thickness, T and h respectively, and are presented over varying mode-mixity and h/T ratios.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123838801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25319
Y. Frostig, E. Bozhevolnaya
A high-order model for free vibrations of singly curved sandwich beams is presented. The model takes into account the transverse flexibility of the sandwich core while the faces of the sandwich are treated as thin beams. Linear equations of motion as well as the natural boundary conditions are derived. It is shown for the curved sandwich beams, that there exist four eigen modes. A numerical analysis of free vibration of the simply supported beams is carried out. Effects of design parameters of the sandwich constituents on the eigen modes and their appropriate frequencies are investigated.
{"title":"Free Vibration of High-Order Curved Sandwich Beams","authors":"Y. Frostig, E. Bozhevolnaya","doi":"10.1115/imece2001/ad-25319","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25319","url":null,"abstract":"\u0000 A high-order model for free vibrations of singly curved sandwich beams is presented. The model takes into account the transverse flexibility of the sandwich core while the faces of the sandwich are treated as thin beams. Linear equations of motion as well as the natural boundary conditions are derived. It is shown for the curved sandwich beams, that there exist four eigen modes. A numerical analysis of free vibration of the simply supported beams is carried out. Effects of design parameters of the sandwich constituents on the eigen modes and their appropriate frequencies are investigated.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122642823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25302
G. Tandon, R. Kim
A study is conducted to examine and predict the micromechanical failure modes in a unidirectional composite when subjected to tensile loading parallel to the fibers. Experimental observations are made at some selected stress levels to identify the initiation and growth of micro damage during loading. The axisymmetric damage model of a concentric cylinder is then utilized to postulate and analyze some failure scenarios.
{"title":"Damage Evolution and Failure Modeling in Unidirectional Graphite/Epoxy Composite","authors":"G. Tandon, R. Kim","doi":"10.1115/imece2001/ad-25302","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25302","url":null,"abstract":"\u0000 A study is conducted to examine and predict the micromechanical failure modes in a unidirectional composite when subjected to tensile loading parallel to the fibers. Experimental observations are made at some selected stress levels to identify the initiation and growth of micro damage during loading. The axisymmetric damage model of a concentric cylinder is then utilized to postulate and analyze some failure scenarios.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133480147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-11-11DOI: 10.1115/imece2001/ad-25307
J. N. Baucom, M. Zikry
The role of fabric architecture on the impact-induced damage progression and perforation resistance of glass-fiber reinforced vinyl-ester resin panels under dynamic loading condition is investigated. Three fabric preforms are considered: a 2-dimensional, plain-woven laminate, a commercially available biaxially reinforced warp-knit, and a 3-dimensional, orthogonally woven preform. Composite samples are subjected to multiple impacts, until perforation, and the impactor position and acceleration are monitored throughout each event, resulting in a visualization of dynamic energy dissipation. Failure modes of the various material systems are characterized. The radial damage expansion was smallest for the 2-d laminate, larger for the biaxially-reinforced warp-knit, and largest for the 3-d orthogonal woven composite. The 3-d composite survived more hits and dissipated more total energy than the other systems. The difference may be due to the additional energy absorption mechanisms, which involve the crimped portion of z-tows in the 3-d composites. This implies that failure may be controlled by manipulation of the properties of the z-tows. It also indicates that the surface condition of 3-d orthogonally woven composites can strongly affect the progression of impact-induced damage.
{"title":"Impact-Induced Damage Progression in 2-D and 3-D Woven Composite Systems","authors":"J. N. Baucom, M. Zikry","doi":"10.1115/imece2001/ad-25307","DOIUrl":"https://doi.org/10.1115/imece2001/ad-25307","url":null,"abstract":"\u0000 The role of fabric architecture on the impact-induced damage progression and perforation resistance of glass-fiber reinforced vinyl-ester resin panels under dynamic loading condition is investigated. Three fabric preforms are considered: a 2-dimensional, plain-woven laminate, a commercially available biaxially reinforced warp-knit, and a 3-dimensional, orthogonally woven preform. Composite samples are subjected to multiple impacts, until perforation, and the impactor position and acceleration are monitored throughout each event, resulting in a visualization of dynamic energy dissipation. Failure modes of the various material systems are characterized. The radial damage expansion was smallest for the 2-d laminate, larger for the biaxially-reinforced warp-knit, and largest for the 3-d orthogonal woven composite. The 3-d composite survived more hits and dissipated more total energy than the other systems. The difference may be due to the additional energy absorption mechanisms, which involve the crimped portion of z-tows in the 3-d composites. This implies that failure may be controlled by manipulation of the properties of the z-tows. It also indicates that the surface condition of 3-d orthogonally woven composites can strongly affect the progression of impact-induced damage.","PeriodicalId":442756,"journal":{"name":"Damage Initiation and Prediction in Composites, Sandwich Structures and Thermal Barrier Coatings","volume":"164 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123193972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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