{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/21742"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/21742","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Process-induced viscoelastic residual stress analysis of graphite/epoxy composite structures","abstract":"In this research the effect of viscoelastic behavior of thermoset matrix fiber-reinforced composites on process-induced residual stresses was investigated. The material selected for study was AS4/3501-6, a commercial prepreg system manufactured by Hercules, Inc. To investigate the cure-dependent viscoelastic behavior, a series of stress relaxation tests was performed on fully and partially cured 3501-6 epoxy specimens. The master relaxation curves were modeled as functions of time and degree of cure in a thermorheologically complex manner. From this information, time and degree of cure dependent viscoelastic constitutive equations were developed for the composite. A process model was then formulated to predict residual stresses during cure. Two separable problems were analyzed with the process model. First, a finite difference scheme was used to solve the thermochemical problem to obtain degree of cure and temperature fields. The results of this analysis were then used as input for a finite element model of rectangular laminates and circular cylinders. A recursive formulation was adopted to solve the computationally intensive time-superposition integration. Both thin and thick plates and cylinders were analyzed, subjected to the manufacturer's recommended cure cycle. In the cylinder case, the effect of the mandrel structure on residual stress fields was also investigated. Stress histories and distributions were analyzed to understand how residual stresses develop and what mechanisms are most important. The common assumption of stress free laminates before cooldown was shown to be invalid. Chemical shrinkage effects, often neglected, can be quite significant. In cylinder geometries the geometrical constraint together with the influence of the mandrel makes a direct correlation difficult between process-induced stresses for laminates and cylinders.","abstract_html":"In this research the effect of viscoelastic behavior of thermoset matrix fiber-reinforced composites on process-induced residual stresses was investigated. The material selected for study was AS4/3501-6, a commercial prepreg system manufactured by Hercules, Inc. To investigate the cure-dependent viscoelastic behavior, a series of stress relaxation tests was performed on fully and partially cured 3501-6 epoxy specimens. The master relaxation curves were modeled as functions of time and degree of cure in a thermorheologically complex manner. From this information, time and degree of cure dependent viscoelastic constitutive equations were developed for the composite. A process model was then formulated to predict residual stresses during cure. Two separable problems were analyzed with the process model. First, a finite difference scheme was used to solve the thermochemical problem to obtain degree of cure and temperature fields. The results of this analysis were then used as input for a finite element model of rectangular laminates and circular cylinders. A recursive formulation was adopted to solve the computationally intensive time-superposition integration. Both thin and thick plates and cylinders were analyzed, subjected to the manufacturer's recommended cure cycle. In the cylinder case, the effect of the mandrel structure on residual stress fields was also investigated. Stress histories and distributions were analyzed to understand how residual stresses develop and what mechanisms are most important. The common assumption of stress free laminates before cooldown was shown to be invalid. Chemical shrinkage effects, often neglected, can be quite significant. In cylinder geometries the geometrical constraint together with the influence of the mandrel makes a direct correlation difficult between process-induced stresses for laminates and cylinders.","abstract_has_math":false,"creators":["Kim, Yeong Kook"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Aerospace Engineering","degree_department":null,"school":null,"contributors":["White, Scott R."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-05-07T13:17:46Z","date_published":"2011-05-07T13:17:46Z","updated_at":"2026-07-22T22:25:18Z","subjects":["Engineering, Aerospace","Engineering, Mechanical","Engineering, Materials Science"],"languages":["eng"],"rights":["Copyright 1996 Kim, Yeong Kook"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9625150","(UMI)AAI9625150"],"render_values":[{"text":"AAI9625150","href":null,"code":true},{"text":"(UMI)AAI9625150","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/21742","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["White, Scott R."]},{"key":"dc:creator","label":"Author","values":["Kim, Yeong Kook"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-05-07T13:17:46Z","10000-01-01","1996"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Aerospace Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Engineering, Aerospace","Engineering, Mechanical","Engineering, Materials Science"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 1996 Kim, Yeong Kook"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["AAI9625150","(UMI)AAI9625150","http://hdl.handle.net/2142/21742"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["In this research the effect of viscoelastic behavior of thermoset matrix fiber-reinforced composites on process-induced residual stresses was investigated. The material selected for study was AS4/3501-6, a commercial prepreg system manufactured by Hercules, Inc. To investigate the cure-dependent viscoelastic behavior, a series of stress relaxation tests was performed on fully and partially cured 3501-6 epoxy specimens. The master relaxation curves were modeled as functions of time and degree of cure in a thermorheologically complex manner. From this information, time and degree of cure dependent viscoelastic constitutive equations were developed for the composite. A process model was then formulated to predict residual stresses during cure. Two separable problems were analyzed with the process model. First, a finite difference scheme was used to solve the thermochemical problem to obtain degree of cure and temperature fields. The results of this analysis were then used as input for a finite element model of rectangular laminates and circular cylinders. A recursive formulation was adopted to solve the computationally intensive time-superposition integration. Both thin and thick plates and cylinders were analyzed, subjected to the manufacturer's recommended cure cycle. In the cylinder case, the effect of the mandrel structure on residual stress fields was also investigated. Stress histories and distributions were analyzed to understand how residual stresses develop and what mechanisms are most important. The common assumption of stress free laminates before cooldown was shown to be invalid. Chemical shrinkage effects, often neglected, can be quite significant. In cylinder geometries the geometrical constraint together with the influence of the mandrel makes a direct correlation difficult between process-induced stresses for laminates and cylinders.","Made available in DSpace on 2011-05-07T13:17:46Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9625150.pdf: 5367891 bytes, checksum: 4a49d6e7629791ee00bdd3c2f8a11ad0 (MD5) Previous issue date: 1996","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:52:54Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:24:24-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"]},{"key":"dc:title","label":"Title","values":["Process-induced viscoelastic residual stress analysis of graphite/epoxy composite structures"]}]}],"canonical_facts":{"dc:contributor":["White, Scott R."],"dc:creator":["Kim, Yeong Kook"],"dc:date":["2011-05-07T13:17:46Z","10000-01-01","1996"],"dc:description":["In this research the effect of viscoelastic behavior of thermoset matrix fiber-reinforced composites on process-induced residual stresses was investigated. The material selected for study was AS4/3501-6, a commercial prepreg system manufactured by Hercules, Inc. To investigate the cure-dependent viscoelastic behavior, a series of stress relaxation tests was performed on fully and partially cured 3501-6 epoxy specimens. The master relaxation curves were modeled as functions of time and degree of cure in a thermorheologically complex manner. From this information, time and degree of cure dependent viscoelastic constitutive equations were developed for the composite. A process model was then formulated to predict residual stresses during cure. Two separable problems were analyzed with the process model. First, a finite difference scheme was used to solve the thermochemical problem to obtain degree of cure and temperature fields. The results of this analysis were then used as input for a finite element model of rectangular laminates and circular cylinders. A recursive formulation was adopted to solve the computationally intensive time-superposition integration. Both thin and thick plates and cylinders were analyzed, subjected to the manufacturer's recommended cure cycle. In the cylinder case, the effect of the mandrel structure on residual stress fields was also investigated. Stress histories and distributions were analyzed to understand how residual stresses develop and what mechanisms are most important. The common assumption of stress free laminates before cooldown was shown to be invalid. Chemical shrinkage effects, often neglected, can be quite significant. In cylinder geometries the geometrical constraint together with the influence of the mandrel makes a direct correlation difficult between process-induced stresses for laminates and cylinders.","Made available in DSpace on 2011-05-07T13:17:46Z (GMT). No. of bitstreams: 2 license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5) 9625150.pdf: 5367891 bytes, checksum: 4a49d6e7629791ee00bdd3c2f8a11ad0 (MD5) Previous issue date: 1996","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Howard Ding (hding2@illinois.edu) on 2011-05-07T14:52:54Z Item is restricted indefinitely.","Restriction data tranferred 2014-07-01T11:24:24-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: ETDs are only available to UIUC Users without author permission","ETDs are only available to UIUC Users without author permission","U of I Only"],"dc:identifier":["AAI9625150","(UMI)AAI9625150","http://hdl.handle.net/2142/21742"],"dc:language":["eng"],"dc:rights":["Copyright 1996 Kim, Yeong Kook"],"dc:subject":["Engineering, Aerospace","Engineering, Mechanical","Engineering, Materials Science"],"dc:title":["Process-induced viscoelastic residual stress analysis of graphite/epoxy composite structures"],"dc:type":["text"],"thesis:degree_discipline":["Aerospace Engineering"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:18Z"}