{"id":{"repo_id":"aachen","oai_identifier":"oai:publications.rwth-aachen.de:62316"},"canonical_url":"https://search.dev.ndltd.org/etd/aachen/oai:publications.rwth-aachen.de:62316","repository":{"repo_id":"aachen","name":"RWTH Aachen University","base_url":"https://publications.rwth-aachen.de/oai2d"},"display":{"title":"Modeling and simulation of diffusion bonding and interface properties of long fiber reinforced NiAl composites","abstract":"Several critical issues of the diffusion bonding process and interfacial properties of continuous single crystal Al2O3 (sapphire) fiber-reinforced NiAl matrix composites were studied. The first issue was the contributions of different densification mechanisms during the diffusion bonding process and the prediction of optimal hot pressing parameters for NiAl matrix coated fibers (MCFs). The choice of suitable process parameters of hot pressing is important in determining the properties of the final composite. Acceptable process parameters have to ensure fabrication of fully dense and void free composites with tolerable fiber damage as well as minimal chemical reactions between fiber and matrix in order to prevent the formation of harmful reaction products in the interface. Based on an analytical diffusion bonding model, in which primary creep of the NiAl matrix – that was studied by creep tests and dynamic tests – was included, the effects of the hot pressing parameters, i.e. pressure, temperature and time, on the deformation behavior and evolution of the microstructure of the matrix in NiAl composites, were simulated. Optimal parameters for the NiAl MCFs of 1300°C / 40 MPa / 30 ~ 60 minutes were recommended. The predictions were compared to experiments, and good agreement between the simulated and experimental results was found. The second issue was the thermal residual stress (TRS) in NiAl composites after thermal mechanical processing due to different coefficients of thermal expansion (CTEs) of fiber and matrix. Without a BN interlayer the simulated compressive axial TRS in sapphire fiber can be very high in a temperature range of 680-790 K and will result in fiber damage. By introducing a BN interlayer, the TRS level decreased and the fiber damage was lowered. However, it caused also a low interfacial strength that reduced the load transfer efficiency from the matrix to the fiber and thus, reduced the composite strength. A higher fiber volume fraction of approximately 40-60% can effectively reduce the TRS in the sapphire fiber and therefore, fiber damage would be mitigated or even eliminated. The simulations were consistent with measurements by nano-indentation. The third issue was the interfacial properties of NiAl composites. By using push-out tests, the interface shear stress for complete debonding was measured. An interfacial model was developed, in which the thermal residual shear stress at the interface and the frictional stress at the interface were included to extract the intrinsic interfacial strength of NiAl composites. According to the simulation, initial debonding can occur at the top or bottom side depending on sample thickness. The push-out test was also numerically simulated at elevated temperatures by assuming a constant value of the interfacial shear strength. Overall, a diffusion bonding model was developed to predict the optimal hot pressing parameters for achieving fully dense and void free composites with tolerable properties; TRS simulations recommended a suitable fiber volume fraction range for lower fiber damage. The models can be used as guidelines to design tough composites for future gas turbine blades.","abstract_html":"Several critical issues of the diffusion bonding process and interfacial properties of continuous single crystal Al2O3 (sapphire) fiber-reinforced NiAl matrix composites were studied. The first issue was the contributions of different densification mechanisms during the diffusion bonding process and the prediction of optimal hot pressing parameters for NiAl matrix coated fibers (MCFs). The choice of suitable process parameters of hot pressing is important in determining the properties of the final composite. Acceptable process parameters have to ensure fabrication of fully dense and void free composites with tolerable fiber damage as well as minimal chemical reactions between fiber and matrix in order to prevent the formation of harmful reaction products in the interface. Based on an analytical diffusion bonding model, in which primary creep of the NiAl matrix – that was studied by creep tests and dynamic tests – was included, the effects of the hot pressing parameters, i.e. pressure, temperature and time, on the deformation behavior and evolution of the microstructure of the matrix in NiAl composites, were simulated. Optimal parameters for the NiAl MCFs of 1300°C / 40 MPa / 30 ~ 60 minutes were recommended. The predictions were compared to experiments, and good agreement between the simulated and experimental results was found. The second issue was the thermal residual stress (TRS) in NiAl composites after thermal mechanical processing due to different coefficients of thermal expansion (CTEs) of fiber and matrix. Without a BN interlayer the simulated compressive axial TRS in sapphire fiber can be very high in a temperature range of 680-790 K and will result in fiber damage. By introducing a BN interlayer, the TRS level decreased and the fiber damage was lowered. However, it caused also a low interfacial strength that reduced the load transfer efficiency from the matrix to the fiber and thus, reduced the composite strength. A higher fiber volume fraction of approximately 40-60% can effectively reduce the TRS in the sapphire fiber and therefore, fiber damage would be mitigated or even eliminated. The simulations were consistent with measurements by nano-indentation. The third issue was the interfacial properties of NiAl composites. By using push-out tests, the interface shear stress for complete debonding was measured. An interfacial model was developed, in which the thermal residual shear stress at the interface and the frictional stress at the interface were included to extract the intrinsic interfacial strength of NiAl composites. According to the simulation, initial debonding can occur at the top or bottom side depending on sample thickness. The push-out test was also numerically simulated at elevated temperatures by assuming a constant value of the interfacial shear strength. Overall, a diffusion bonding model was developed to predict the optimal hot pressing parameters for achieving fully dense and void free composites with tolerable properties; TRS simulations recommended a suitable fiber volume fraction range for lower fiber damage. The models can be used as guidelines to design tough composites for future gas turbine blades.","abstract_has_math":false,"creators":["Chen, Hao"],"institution":"Shaker","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Gottstein, Günter"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2006,"date_issued":"2006","date_published":"2006","updated_at":"2026-07-30T19:43:28Z","subjects":["info:eu-repo/classification/ddc/530","Physik","NiAl-Verbundwekstoffe","Diffusionsschwießen","thermische Eigenspannungen","Push-out Test","NiAl composites","Diffusion bonding","thermal residual stresses"],"languages":["eng"],"rights":["info:eu-repo/semantics/openAccess"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123890%22"],"render_values":[{"text":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123890%22","href":"https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123890%22","code":true}]}]},"links":{"outbound_url":"https://publications.rwth-aachen.de/record/62316","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Gottstein, Günter"]},{"key":"dc:creator","label":"Author","values":["Chen, Hao"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:coverage","label":"Dc Coverage","values":["DE"]},{"key":"dc:date","label":"Dc Date","values":["2006"]},{"key":"dc:publisher","label":"Institution","values":["Shaker"]},{"key":"dc:relation","label":"Dc Relation","values":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-17854","info:eu-repo/semantics/altIdentifier/isbn/3-8322-5678-4"]},{"key":"dc:type","label":"Dc Type","values":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["info:eu-repo/classification/ddc/530","Physik","NiAl-Verbundwekstoffe","Diffusionsschwießen","thermische Eigenspannungen","Push-out Test","NiAl composites","Diffusion bonding","thermal residual stresses"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["info:eu-repo/semantics/openAccess"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://publications.rwth-aachen.de/record/62316","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123890%22"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Several critical issues of the diffusion bonding process and interfacial properties of continuous single crystal Al2O3 (sapphire) fiber-reinforced NiAl matrix composites were studied. The first issue was the contributions of different densification mechanisms during the diffusion bonding process and the prediction of optimal hot pressing parameters for NiAl matrix coated fibers (MCFs). The choice of suitable process parameters of hot pressing is important in determining the properties of the final composite. Acceptable process parameters have to ensure fabrication of fully dense and void free composites with tolerable fiber damage as well as minimal chemical reactions between fiber and matrix in order to prevent the formation of harmful reaction products in the interface. Based on an analytical diffusion bonding model, in which primary creep of the NiAl matrix – that was studied by creep tests and dynamic tests – was included, the effects of the hot pressing parameters, i.e. pressure, temperature and time, on the deformation behavior and evolution of the microstructure of the matrix in NiAl composites, were simulated. Optimal parameters for the NiAl MCFs of 1300°C / 40 MPa / 30 ~ 60 minutes were recommended. The predictions were compared to experiments, and good agreement between the simulated and experimental results was found. The second issue was the thermal residual stress (TRS) in NiAl composites after thermal mechanical processing due to different coefficients of thermal expansion (CTEs) of fiber and matrix. Without a BN interlayer the simulated compressive axial TRS in sapphire fiber can be very high in a temperature range of 680-790 K and will result in fiber damage. By introducing a BN interlayer, the TRS level decreased and the fiber damage was lowered. However, it caused also a low interfacial strength that reduced the load transfer efficiency from the matrix to the fiber and thus, reduced the composite strength. A higher fiber volume fraction of approximately 40-60% can effectively reduce the TRS in the sapphire fiber and therefore, fiber damage would be mitigated or even eliminated. The simulations were consistent with measurements by nano-indentation. The third issue was the interfacial properties of NiAl composites. By using push-out tests, the interface shear stress for complete debonding was measured. An interfacial model was developed, in which the thermal residual shear stress at the interface and the frictional stress at the interface were included to extract the intrinsic interfacial strength of NiAl composites. According to the simulation, initial debonding can occur at the top or bottom side depending on sample thickness. The push-out test was also numerically simulated at elevated temperatures by assuming a constant value of the interfacial shear strength. Overall, a diffusion bonding model was developed to predict the optimal hot pressing parameters for achieving fully dense and void free composites with tolerable properties; TRS simulations recommended a suitable fiber volume fraction range for lower fiber damage. The models can be used as guidelines to design tough composites for future gas turbine blades."]},{"key":"dc:source","label":"Dc Source","values":["Aachen : Shaker, Berichte aus der Materialwissenschaft VIII, 128 S. : Ill., graph. Darst. (2006). = Zugl.: Aachen, Techn. Hochsch., Diss., 2006"]},{"key":"dc:title","label":"Title","values":["Modeling and simulation of diffusion bonding and interface properties of long fiber reinforced NiAl composites"]}]}],"canonical_facts":{"dc:contributor":["Gottstein, Günter"],"dc:coverage":["DE"],"dc:creator":["Chen, Hao"],"dc:date":["2006"],"dc:description":["Several critical issues of the diffusion bonding process and interfacial properties of continuous single crystal Al2O3 (sapphire) fiber-reinforced NiAl matrix composites were studied. The first issue was the contributions of different densification mechanisms during the diffusion bonding process and the prediction of optimal hot pressing parameters for NiAl matrix coated fibers (MCFs). The choice of suitable process parameters of hot pressing is important in determining the properties of the final composite. Acceptable process parameters have to ensure fabrication of fully dense and void free composites with tolerable fiber damage as well as minimal chemical reactions between fiber and matrix in order to prevent the formation of harmful reaction products in the interface. Based on an analytical diffusion bonding model, in which primary creep of the NiAl matrix – that was studied by creep tests and dynamic tests – was included, the effects of the hot pressing parameters, i.e. pressure, temperature and time, on the deformation behavior and evolution of the microstructure of the matrix in NiAl composites, were simulated. Optimal parameters for the NiAl MCFs of 1300°C / 40 MPa / 30 ~ 60 minutes were recommended. The predictions were compared to experiments, and good agreement between the simulated and experimental results was found. The second issue was the thermal residual stress (TRS) in NiAl composites after thermal mechanical processing due to different coefficients of thermal expansion (CTEs) of fiber and matrix. Without a BN interlayer the simulated compressive axial TRS in sapphire fiber can be very high in a temperature range of 680-790 K and will result in fiber damage. By introducing a BN interlayer, the TRS level decreased and the fiber damage was lowered. However, it caused also a low interfacial strength that reduced the load transfer efficiency from the matrix to the fiber and thus, reduced the composite strength. A higher fiber volume fraction of approximately 40-60% can effectively reduce the TRS in the sapphire fiber and therefore, fiber damage would be mitigated or even eliminated. The simulations were consistent with measurements by nano-indentation. The third issue was the interfacial properties of NiAl composites. By using push-out tests, the interface shear stress for complete debonding was measured. An interfacial model was developed, in which the thermal residual shear stress at the interface and the frictional stress at the interface were included to extract the intrinsic interfacial strength of NiAl composites. According to the simulation, initial debonding can occur at the top or bottom side depending on sample thickness. The push-out test was also numerically simulated at elevated temperatures by assuming a constant value of the interfacial shear strength. Overall, a diffusion bonding model was developed to predict the optimal hot pressing parameters for achieving fully dense and void free composites with tolerable properties; TRS simulations recommended a suitable fiber volume fraction range for lower fiber damage. The models can be used as guidelines to design tough composites for future gas turbine blades."],"dc:identifier":["https://publications.rwth-aachen.de/record/62316","https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123890%22"],"dc:language":["eng"],"dc:publisher":["Shaker"],"dc:relation":["info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-17854","info:eu-repo/semantics/altIdentifier/isbn/3-8322-5678-4"],"dc:rights":["info:eu-repo/semantics/openAccess"],"dc:source":["Aachen : Shaker, Berichte aus der Materialwissenschaft VIII, 128 S. : Ill., graph. Darst. (2006). = Zugl.: Aachen, Techn. Hochsch., Diss., 2006"],"dc:subject":["info:eu-repo/classification/ddc/530","Physik","NiAl-Verbundwekstoffe","Diffusionsschwießen","thermische Eigenspannungen","Push-out Test","NiAl composites","Diffusion bonding","thermal residual stresses"],"dc:title":["Modeling and simulation of diffusion bonding and interface properties of long fiber reinforced NiAl composites"],"dc:type":["info:eu-repo/semantics/doctoralThesis","info:eu-repo/semantics/publishedVersion"]},"updated_at":"2026-07-30T19:43:28Z"}