{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/112473"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/112473","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Synthesis, characterization, and mode I fracture toughness of aligned carbon nanotube polymer matrix nanocomposites","abstract":"In an effort to fully understand the contribution of carbon nanotubes (CNTs) to strength and toughness enhancement in hierarchical nanoengineered composites, particularly steady state Mode I fracture toughness, RTM6 and EPON 862/W epoxy based vertically-aligned carbon nanotube (A-CNT) polymer nanocomposites (A-PNCs) are manufactured. These A-PNCs can be tested to isolate structure-property relationships between the polymer matrix and the A-CNTs without the presence of the micro-scale fibers. Additionally, A-CNT volume fraction can be varied via a densification process to realize 1-30% volume fraction (vf.%) A-PNCs. An investigation of the Mode I initiation fracture toughness via single edge notch beam (SENB) testing of A-PNCs with 1-5 vf.% uniaxially densified A-CNT forests finds that RTM6 baseline and A-PNC samples have a KIc,i of ~ 1 MPa-m¹/², with the exception of 1 vf.% having 1.33 ± 0.09 MPa-m¹/², which needs to be further explored due to process-structure questions of specimen quality. No statistically significant change is observed in EPON 862/W A-PNCs at 1-5 vf.% over baseline specimens having a KIc,i of 1.49 ± 0.06 MPa-m¹/² , indicating that A-CNTs do not offer any toughening at initiation in this system. Scanning electron microscopy of the fracture surface for both A-PNC systems reveals that < 10% of the A-CNTs available are engaged during crack bridging, i.e., in a 5 vf.% A-PNC specimen, at most 0.5 vf.% of the A-CNTs are engaged during fracture, and pull-out from the matrix is less than 1 pm. Thus, the pullout and debonding toughening contribution offered by the A-CNTs is expected and measured to be negligible. It is possible that these A-CNTs may offer steady-state toughening, however, results are not achieved due to limitations in specimen size and geometry. While changes in Mode I initiation toughness are not observed, significant changes in properties from both quasi-static and dynamic nanoindentation testing are observed. The A-CNT alignment confers a non-isotropic mechanical response when quasi-statically tested with A-CNTs parallel or perpendicular to the indentation load. An ~ 270% modulus increase over baseline for the 30 vf.% EPON 862/W A-PNC parallel configuration and a ~ 140% increase in the perpendicular configuration, are observed and dynamic nanoindentation supports this finding with, e.g., a storage modulus increase of ~ 200% in the parallel orientation. RTM6 A-PNCs show less of an increase in indentation modulus (~ 33% in 10 vf.% specimens in the parallel direction) over baseline when compared to those of EPON 862/W, likely due to the relatively stiff RTM6 (modulus is ~ 1.5x larger than EPON 862/W) and therefore there is a relatively smaller A-CNT stiffness contribution. Looking forward, the A-CNTs used in this work are noted to be unmodified/as-grown, and the A-CNT fracture results highlight the need for modifying the A-CNTs towards increased A-CNT strength (defect density reduction), and/or reducing the strength of the CNT-polymer interface, to increase A-CNT toughness contribution further.","abstract_html":"In an effort to fully understand the contribution of carbon nanotubes (CNTs) to strength and toughness enhancement in hierarchical nanoengineered composites, particularly steady state Mode I fracture toughness, RTM6 and EPON 862/W epoxy based vertically-aligned carbon nanotube (A-CNT) polymer nanocomposites (A-PNCs) are manufactured. These A-PNCs can be tested to isolate structure-property relationships between the polymer matrix and the A-CNTs without the presence of the micro-scale fibers. Additionally, A-CNT volume fraction can be varied via a densification process to realize 1-30% volume fraction (vf.%) A-PNCs. An investigation of the Mode I initiation fracture toughness via single edge notch beam (SENB) testing of A-PNCs with 1-5 vf.% uniaxially densified A-CNT forests finds that RTM6 baseline and A-PNC samples have a KIc,i of ~ 1 MPa-m¹/², with the exception of 1 vf.% having 1.33 ± 0.09 MPa-m¹/², which needs to be further explored due to process-structure questions of specimen quality. No statistically significant change is observed in EPON 862/W A-PNCs at 1-5 vf.% over baseline specimens having a KIc,i of 1.49 ± 0.06 MPa-m¹/² , indicating that A-CNTs do not offer any toughening at initiation in this system. Scanning electron microscopy of the fracture surface for both A-PNC systems reveals that &lt; 10% of the A-CNTs available are engaged during crack bridging, i.e., in a 5 vf.% A-PNC specimen, at most 0.5 vf.% of the A-CNTs are engaged during fracture, and pull-out from the matrix is less than 1 pm. Thus, the pullout and debonding toughening contribution offered by the A-CNTs is expected and measured to be negligible. It is possible that these A-CNTs may offer steady-state toughening, however, results are not achieved due to limitations in specimen size and geometry. While changes in Mode I initiation toughness are not observed, significant changes in properties from both quasi-static and dynamic nanoindentation testing are observed. The A-CNT alignment confers a non-isotropic mechanical response when quasi-statically tested with A-CNTs parallel or perpendicular to the indentation load. An ~ 270% modulus increase over baseline for the 30 vf.% EPON 862/W A-PNC parallel configuration and a ~ 140% increase in the perpendicular configuration, are observed and dynamic nanoindentation supports this finding with, e.g., a storage modulus increase of ~ 200% in the parallel orientation. RTM6 A-PNCs show less of an increase in indentation modulus (~ 33% in 10 vf.% specimens in the parallel direction) over baseline when compared to those of EPON 862/W, likely due to the relatively stiff RTM6 (modulus is ~ 1.5x larger than EPON 862/W) and therefore there is a relatively smaller A-CNT stiffness contribution. Looking forward, the A-CNTs used in this work are noted to be unmodified/as-grown, and the A-CNT fracture results highlight the need for modifying the A-CNTs towards increased A-CNT strength (defect density reduction), and/or reducing the strength of the CNT-polymer interface, to increase A-CNT toughness contribution further.","abstract_has_math":false,"creators":["Lidston, Dale L. (Dale Leigh)"],"institution":"Massachusetts Institute of Technology","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Department of Aeronautics and Astronautics.","school":null,"contributors":[],"advisors":["Brian L. Wardle."],"committee_chairs":[],"committee_members":[],"year":2017,"date_issued":"2017","date_published":"2017","updated_at":"2026-07-22T22:21:16Z","subjects":["Aeronautics and Astronautics."],"languages":["eng"],"rights":["MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."],"rights_urls":["http://dspace.mit.edu/handle/1721.1/7582"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1721.1/112473","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Brian L. Wardle."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. Department of Aeronautics and Astronautics."]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Massachusetts Institute of Technology. Department of Aeronautics and Astronautics."]},{"key":"dc:creator","label":"Author","values":["Lidston, Dale L. (Dale Leigh)"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2017-12-05T19:14:23Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2017-12-05T19:14:23Z"]},{"key":"dc:date.issued","label":"Date","values":["2017"]},{"key":"dc:publisher","label":"Institution","values":["Massachusetts Institute of Technology"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Aeronautics and Astronautics."]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://dspace.mit.edu/handle/1721.1/7582"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1721.1/112473"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.","Cataloged from PDF version of thesis.","Includes bibliographical references (pages 199-215)."]},{"key":"dc:description.abstract","label":"Abstract","values":["In an effort to fully understand the contribution of carbon nanotubes (CNTs) to strength and toughness enhancement in hierarchical nanoengineered composites, particularly steady state Mode I fracture toughness, RTM6 and EPON 862/W epoxy based vertically-aligned carbon nanotube (A-CNT) polymer nanocomposites (A-PNCs) are manufactured. These A-PNCs can be tested to isolate structure-property relationships between the polymer matrix and the A-CNTs without the presence of the micro-scale fibers. Additionally, A-CNT volume fraction can be varied via a densification process to realize 1-30% volume fraction (vf.%) A-PNCs. An investigation of the Mode I initiation fracture toughness via single edge notch beam (SENB) testing of A-PNCs with 1-5 vf.% uniaxially densified A-CNT forests finds that RTM6 baseline and A-PNC samples have a KIc,i of ~ 1 MPa-m¹/², with the exception of 1 vf.% having 1.33 ± 0.09 MPa-m¹/², which needs to be further explored due to process-structure questions of specimen quality. No statistically significant change is observed in EPON 862/W A-PNCs at 1-5 vf.% over baseline specimens having a KIc,i of 1.49 ± 0.06 MPa-m¹/² , indicating that A-CNTs do not offer any toughening at initiation in this system. Scanning electron microscopy of the fracture surface for both A-PNC systems reveals that < 10% of the A-CNTs available are engaged during crack bridging, i.e., in a 5 vf.% A-PNC specimen, at most 0.5 vf.% of the A-CNTs are engaged during fracture, and pull-out from the matrix is less than 1 pm. Thus, the pullout and debonding toughening contribution offered by the A-CNTs is expected and measured to be negligible. It is possible that these A-CNTs may offer steady-state toughening, however, results are not achieved due to limitations in specimen size and geometry. While changes in Mode I initiation toughness are not observed, significant changes in properties from both quasi-static and dynamic nanoindentation testing are observed. The A-CNT alignment confers a non-isotropic mechanical response when quasi-statically tested with A-CNTs parallel or perpendicular to the indentation load. An ~ 270% modulus increase over baseline for the 30 vf.% EPON 862/W A-PNC parallel configuration and a ~ 140% increase in the perpendicular configuration, are observed and dynamic nanoindentation supports this finding with, e.g., a storage modulus increase of ~ 200% in the parallel orientation. RTM6 A-PNCs show less of an increase in indentation modulus (~ 33% in 10 vf.% specimens in the parallel direction) over baseline when compared to those of EPON 862/W, likely due to the relatively stiff RTM6 (modulus is ~ 1.5x larger than EPON 862/W) and therefore there is a relatively smaller A-CNT stiffness contribution. Looking forward, the A-CNTs used in this work are noted to be unmodified/as-grown, and the A-CNT fracture results highlight the need for modifying the A-CNTs towards increased A-CNT strength (defect density reduction), and/or reducing the strength of the CNT-polymer interface, to increase A-CNT toughness contribution further."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["S.M."]},{"key":"dc:title","label":"Title","values":["Synthesis, characterization, and mode I fracture toughness of aligned carbon nanotube polymer matrix nanocomposites"]}]}],"canonical_facts":{"dc:contributor.advisor":["Brian L. Wardle."],"dc:contributor.department":["Massachusetts Institute of Technology. Department of Aeronautics and Astronautics."],"dc:contributor.other":["Massachusetts Institute of Technology. Department of Aeronautics and Astronautics."],"dc:creator":["Lidston, Dale L. (Dale Leigh)"],"dc:date.accessioned":["2017-12-05T19:14:23Z"],"dc:date.available":["2017-12-05T19:14:23Z"],"dc:date.issued":["2017"],"dc:description":["Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2017.","Cataloged from PDF version of thesis.","Includes bibliographical references (pages 199-215)."],"dc:description.abstract":["In an effort to fully understand the contribution of carbon nanotubes (CNTs) to strength and toughness enhancement in hierarchical nanoengineered composites, particularly steady state Mode I fracture toughness, RTM6 and EPON 862/W epoxy based vertically-aligned carbon nanotube (A-CNT) polymer nanocomposites (A-PNCs) are manufactured. These A-PNCs can be tested to isolate structure-property relationships between the polymer matrix and the A-CNTs without the presence of the micro-scale fibers. Additionally, A-CNT volume fraction can be varied via a densification process to realize 1-30% volume fraction (vf.%) A-PNCs. An investigation of the Mode I initiation fracture toughness via single edge notch beam (SENB) testing of A-PNCs with 1-5 vf.% uniaxially densified A-CNT forests finds that RTM6 baseline and A-PNC samples have a KIc,i of ~ 1 MPa-m¹/², with the exception of 1 vf.% having 1.33 ± 0.09 MPa-m¹/², which needs to be further explored due to process-structure questions of specimen quality. No statistically significant change is observed in EPON 862/W A-PNCs at 1-5 vf.% over baseline specimens having a KIc,i of 1.49 ± 0.06 MPa-m¹/² , indicating that A-CNTs do not offer any toughening at initiation in this system. Scanning electron microscopy of the fracture surface for both A-PNC systems reveals that < 10% of the A-CNTs available are engaged during crack bridging, i.e., in a 5 vf.% A-PNC specimen, at most 0.5 vf.% of the A-CNTs are engaged during fracture, and pull-out from the matrix is less than 1 pm. Thus, the pullout and debonding toughening contribution offered by the A-CNTs is expected and measured to be negligible. It is possible that these A-CNTs may offer steady-state toughening, however, results are not achieved due to limitations in specimen size and geometry. While changes in Mode I initiation toughness are not observed, significant changes in properties from both quasi-static and dynamic nanoindentation testing are observed. The A-CNT alignment confers a non-isotropic mechanical response when quasi-statically tested with A-CNTs parallel or perpendicular to the indentation load. An ~ 270% modulus increase over baseline for the 30 vf.% EPON 862/W A-PNC parallel configuration and a ~ 140% increase in the perpendicular configuration, are observed and dynamic nanoindentation supports this finding with, e.g., a storage modulus increase of ~ 200% in the parallel orientation. RTM6 A-PNCs show less of an increase in indentation modulus (~ 33% in 10 vf.% specimens in the parallel direction) over baseline when compared to those of EPON 862/W, likely due to the relatively stiff RTM6 (modulus is ~ 1.5x larger than EPON 862/W) and therefore there is a relatively smaller A-CNT stiffness contribution. Looking forward, the A-CNTs used in this work are noted to be unmodified/as-grown, and the A-CNT fracture results highlight the need for modifying the A-CNTs towards increased A-CNT strength (defect density reduction), and/or reducing the strength of the CNT-polymer interface, to increase A-CNT toughness contribution further."],"dc:description.degree":["S.M."],"dc:identifier.uri":["http://hdl.handle.net/1721.1/112473"],"dc:language.iso":["eng"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission."],"dc:rights.uri":["http://dspace.mit.edu/handle/1721.1/7582"],"dc:subject":["Aeronautics and Astronautics."],"dc:title":["Synthesis, characterization, and mode I fracture toughness of aligned carbon nanotube polymer matrix nanocomposites"],"dc:type":["Thesis"]},"updated_at":"2026-07-22T22:21:16Z"}