A series of fiber pushout tests on thin-slice samples of a SCS-6/Timetal-21S composite were carried out to determine the load values at which partial and full debonding occurs. Finite element calculations of the stress field in the specimen were employed to assess the interphase strength of the composite as function of temperature. In these calculations, the semi-infinite thickness and the traction-free surface effects of the thin-slice samples on the corresponding stress field are considered. For each of these specimens, the distribution of shear stress along the fiber/matrix interface is determined in order to identify a region of stress localization which is taken in this study to be a measure of the interphase shear strength. This strength is then identified as the balance of forces at this localized field due to the traction-free surface of the composite section. Both contributions from process-induced residual stress and geometry-induced constraint of the traction-free surface to the strength are considered. The results of this study showed that the interphase shear strength decreases with an increase in temperature and processing-related residual stress contributes about 35 % to the interphase shear strength at room temperature. Furthermore, the interphase shear strength as calculated in this paper was found to be larger than that determined by considering uniformly distributed shear stress along a pushout fiber.
{"title":"Interphase Shear Strength of Titanium Metal Matrix Composites at Elevated Temperatures","authors":"M. Tamin, D. Osborne, H. Ghonem","doi":"10.1115/imece1996-0482","DOIUrl":"https://doi.org/10.1115/imece1996-0482","url":null,"abstract":"\u0000 A series of fiber pushout tests on thin-slice samples of a SCS-6/Timetal-21S composite were carried out to determine the load values at which partial and full debonding occurs. Finite element calculations of the stress field in the specimen were employed to assess the interphase strength of the composite as function of temperature. In these calculations, the semi-infinite thickness and the traction-free surface effects of the thin-slice samples on the corresponding stress field are considered. For each of these specimens, the distribution of shear stress along the fiber/matrix interface is determined in order to identify a region of stress localization which is taken in this study to be a measure of the interphase shear strength. This strength is then identified as the balance of forces at this localized field due to the traction-free surface of the composite section. Both contributions from process-induced residual stress and geometry-induced constraint of the traction-free surface to the strength are considered. The results of this study showed that the interphase shear strength decreases with an increase in temperature and processing-related residual stress contributes about 35 % to the interphase shear strength at room temperature. Furthermore, the interphase shear strength as calculated in this paper was found to be larger than that determined by considering uniformly distributed shear stress along a pushout fiber.","PeriodicalId":326220,"journal":{"name":"Aerospace and Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133534406","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}
The oxidation effects on surface crack development of oxidized Ti 15-3 and Ti β-21S Metal Matrix Composite (MMC) unidirectional laminates under applied mechanical loading are investigated in the present study. Experimental results of surface crack development as a function of applied load are presented. An approximate mechanical model is established and a stress analysis of an oxidized laminate with surface cracks is performed. To simplify the analysis, motivated by experimental observations, a periodic distribution of surface cracks in the oxide layer is assumed. The critical value of the applied mechanical load, which is necessary for the formation of new cracks, as a function of crack density and phase transformation induced eigenstrain are studied.
{"title":"Damage in Oxidized Titanium Metal Matrix Composites","authors":"D. Lagoudas, Shouze Xu, David Miller, D. Allen","doi":"10.1115/imece1996-0480","DOIUrl":"https://doi.org/10.1115/imece1996-0480","url":null,"abstract":"\u0000 The oxidation effects on surface crack development of oxidized Ti 15-3 and Ti β-21S Metal Matrix Composite (MMC) unidirectional laminates under applied mechanical loading are investigated in the present study. Experimental results of surface crack development as a function of applied load are presented. An approximate mechanical model is established and a stress analysis of an oxidized laminate with surface cracks is performed. To simplify the analysis, motivated by experimental observations, a periodic distribution of surface cracks in the oxide layer is assumed. The critical value of the applied mechanical load, which is necessary for the formation of new cracks, as a function of crack density and phase transformation induced eigenstrain are studied.","PeriodicalId":326220,"journal":{"name":"Aerospace and Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132417400","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}
A mechanistic framework is proposed which may facilitate establishment of inelastic deformation surfaces (analogous to yield surface for metals) and flow-rules for some composites. The motivation is to develop a method for three dimensional stress analysis of composites in the nonlinear regime.
{"title":"Modeling of Inelastic Metal Matrix Composite Response Under Multiaxial Loading","authors":"J. Ahmad, T. Nicholas","doi":"10.1115/imece1996-0487","DOIUrl":"https://doi.org/10.1115/imece1996-0487","url":null,"abstract":"\u0000 A mechanistic framework is proposed which may facilitate establishment of inelastic deformation surfaces (analogous to yield surface for metals) and flow-rules for some composites. The motivation is to develop a method for three dimensional stress analysis of composites in the nonlinear regime.","PeriodicalId":326220,"journal":{"name":"Aerospace and Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127350836","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}
Guidance for the formulation of robust, multiaxial, constitutive models for advanced materials is provided by addressing theoretical and experimental issues using micromechanics. The multiaxial response of metal matrix composites, depicted in terms of macro flow/damage surfaces, is predicted at room and elevated temperatures using an analytical micromechanical model that includes viscoplastic matrix response as well as fiber-matrix debonding. Macro flow/damage surfaces (i.e., debonding envelopes, matrix threshold surfaces, macro “yield” surfaces, surfaces of constant inelastic strain rate, and surfaces of constant dissipation rate) are determined for silicon carbide/titanium in three stress spaces. Residual stresses are shown to offset the centers of the flow/damage surfaces from the origin and their shape is significantly altered by debonding. The results indicate which type of flow/damage surfaces should be characterized and what loadings applied to provide the most meaningful experimental data for guiding theoretical model development and verification.
{"title":"Critique of Macro Flow/Damage Surface Representations for Metal Matrix Composites Using Micromechanics","authors":"C. Lissenden, S. Arnold","doi":"10.1115/imece1996-0486","DOIUrl":"https://doi.org/10.1115/imece1996-0486","url":null,"abstract":"\u0000 Guidance for the formulation of robust, multiaxial, constitutive models for advanced materials is provided by addressing theoretical and experimental issues using micromechanics. The multiaxial response of metal matrix composites, depicted in terms of macro flow/damage surfaces, is predicted at room and elevated temperatures using an analytical micromechanical model that includes viscoplastic matrix response as well as fiber-matrix debonding. Macro flow/damage surfaces (i.e., debonding envelopes, matrix threshold surfaces, macro “yield” surfaces, surfaces of constant inelastic strain rate, and surfaces of constant dissipation rate) are determined for silicon carbide/titanium in three stress spaces. Residual stresses are shown to offset the centers of the flow/damage surfaces from the origin and their shape is significantly altered by debonding. The results indicate which type of flow/damage surfaces should be characterized and what loadings applied to provide the most meaningful experimental data for guiding theoretical model development and verification.","PeriodicalId":326220,"journal":{"name":"Aerospace and Materials","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126329146","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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