{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/97252"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/97252","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Exploring the link between microstructure statistics and transverse ply fracture in carbon/epoxy composites","abstract":"Damage evolution within polymer matrix composites (PMCs) is difficult to characterize, as variability arises in the material microstructure from manufacturing and in the local strength of the constituents, which is inherently statistical. Transverse failure of unidirectional plies is particularly critical in composite laminates, as it is often a precursor for other, more catastrophic failure modes such as delamination and fiber breakage. Although it is possible to attempt to orient fibers primarily in the directional of external loads, avoiding transverse stress concentrations is unattainable, and this will often lead to failure within the ply. The possible interaction of failure mechanisms makes obtaining reliable strength predictions under general loading difficult. This project is dedicated to understanding how the underlying statistics affect the failure of unidirectional composites, and to develop tools to analyze real unidirectional composite microstructures. The first part of this study is focused on reconstructing micrographs of experimental composites and looking at various statistical metrics. We create a computational tool for predicting initial debonding sites based on geometry alone. From there, we create “virtual” microstructures that mimic some of the statistics that describe the real microstructure. We then perform some mesoscale simulations that focus on the cohesive failure of the interfaces between the fibers and the surrounding matrix material. Finally, an analytical material sensitivity formulation is derived and implemented using the direct differentiation method implemented in a C++ Interface-enriched Generalized Finite Element Method (IGFEM) framework. Emphasis is placed on extracting the sensitivity of the transverse failure response with respect to the two material parameters that characterize the interfacial cohesive failure: a critical stress (σ_c) and a critical opening displacement (δ_c).","abstract_html":"Damage evolution within polymer matrix composites (PMCs) is difficult to characterize, as variability arises in the material microstructure from manufacturing and in the local strength of the constituents, which is inherently statistical. Transverse failure of unidirectional plies is particularly critical in composite laminates, as it is often a precursor for other, more catastrophic failure modes such as delamination and fiber breakage. Although it is possible to attempt to orient fibers primarily in the directional of external loads, avoiding transverse stress concentrations is unattainable, and this will often lead to failure within the ply. The possible interaction of failure mechanisms makes obtaining reliable strength predictions under general loading difficult. This project is dedicated to understanding how the underlying statistics affect the failure of unidirectional composites, and to develop tools to analyze real unidirectional composite microstructures. The first part of this study is focused on reconstructing micrographs of experimental composites and looking at various statistical metrics. We create a computational tool for predicting initial debonding sites based on geometry alone. From there, we create “virtual” microstructures that mimic some of the statistics that describe the real microstructure. We then perform some mesoscale simulations that focus on the cohesive failure of the interfaces between the fibers and the surrounding matrix material. Finally, an analytical material sensitivity formulation is derived and implemented using the direct differentiation method implemented in a C++ Interface-enriched Generalized Finite Element Method (IGFEM) framework. Emphasis is placed on extracting the sensitivity of the transverse failure response with respect to the two material parameters that characterize the interfacial cohesive failure: a critical stress (σ_c) and a critical opening displacement (δ_c).","abstract_has_math":false,"creators":["Zacek, Scott Antonio"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Aerospace Engineering","degree_department":null,"school":null,"contributors":["Geubelle, Philippe H."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017-08-10T19:14:25Z","date_published":"2017-08-10T19:14:25Z","updated_at":"2026-07-22T22:24:32Z","subjects":["Composites","Sensitivity analysis"],"languages":["en"],"rights":["Copyright 2017 Scott Zacek"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/97252","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Geubelle, Philippe H."]},{"key":"dc:creator","label":"Author","values":["Zacek, Scott Antonio"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2017-08-10T19:14:25Z","2017-01-19","2017-05"]},{"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":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"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":["Composites","Sensitivity analysis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2017 Scott Zacek"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/97252"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Damage evolution within polymer matrix composites (PMCs) is difficult to characterize, as variability arises in the material microstructure from manufacturing and in the local strength of the constituents, which is inherently statistical. Transverse failure of unidirectional plies is particularly critical in composite laminates, as it is often a precursor for other, more catastrophic failure modes such as delamination and fiber breakage. Although it is possible to attempt to orient fibers primarily in the directional of external loads, avoiding transverse stress concentrations is unattainable, and this will often lead to failure within the ply. The possible interaction of failure mechanisms makes obtaining reliable strength predictions under general loading difficult. This project is dedicated to understanding how the underlying statistics affect the failure of unidirectional composites, and to develop tools to analyze real unidirectional composite microstructures. The first part of this study is focused on reconstructing micrographs of experimental composites and looking at various statistical metrics. We create a computational tool for predicting initial debonding sites based on geometry alone. From there, we create “virtual” microstructures that mimic some of the statistics that describe the real microstructure. We then perform some mesoscale simulations that focus on the cohesive failure of the interfaces between the fibers and the surrounding matrix material. Finally, an analytical material sensitivity formulation is derived and implemented using the direct differentiation method implemented in a C++ Interface-enriched Generalized Finite Element Method (IGFEM) framework. Emphasis is placed on extracting the sensitivity of the transverse failure response with respect to the two material parameters that characterize the interfacial cohesive failure: a critical stress (σ_c) and a critical opening displacement (δ_c).","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-08-10 without embargo terms","The student, Scott Zacek, accepted the attached license on 2017-01-18 at 11:19.","The student, Scott Zacek, submitted this Thesis for approval on 2017-01-18 at 11:24.","This Thesis was approved for publication on 2017-01-19 at 17:27.","DSpace SAF Submission Ingestion Package generated from Vireo submission #10541 on 2017-08-10 at 13:37:24","Made available in DSpace on 2017-08-10T19:14:25Z (GMT). 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Transverse failure of unidirectional plies is particularly critical in composite laminates, as it is often a precursor for other, more catastrophic failure modes such as delamination and fiber breakage. Although it is possible to attempt to orient fibers primarily in the directional of external loads, avoiding transverse stress concentrations is unattainable, and this will often lead to failure within the ply. The possible interaction of failure mechanisms makes obtaining reliable strength predictions under general loading difficult. This project is dedicated to understanding how the underlying statistics affect the failure of unidirectional composites, and to develop tools to analyze real unidirectional composite microstructures. The first part of this study is focused on reconstructing micrographs of experimental composites and looking at various statistical metrics. We create a computational tool for predicting initial debonding sites based on geometry alone. From there, we create “virtual” microstructures that mimic some of the statistics that describe the real microstructure. We then perform some mesoscale simulations that focus on the cohesive failure of the interfaces between the fibers and the surrounding matrix material. Finally, an analytical material sensitivity formulation is derived and implemented using the direct differentiation method implemented in a C++ Interface-enriched Generalized Finite Element Method (IGFEM) framework. Emphasis is placed on extracting the sensitivity of the transverse failure response with respect to the two material parameters that characterize the interfacial cohesive failure: a critical stress (σ_c) and a critical opening displacement (δ_c).","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-08-10 without embargo terms","The student, Scott Zacek, accepted the attached license on 2017-01-18 at 11:19.","The student, Scott Zacek, submitted this Thesis for approval on 2017-01-18 at 11:24.","This Thesis was approved for publication on 2017-01-19 at 17:27.","DSpace SAF Submission Ingestion Package generated from Vireo submission #10541 on 2017-08-10 at 13:37:24","Made available in DSpace on 2017-08-10T19:14:25Z (GMT). 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