AFRL-AFOSR-VA-TR-2015-0323 Multifunctional Shear Pressed CNT Sheets for Strain Sensing and Composite Joint Toughening

This research program investigated critical fabrication aspects, mechanical and electrical properties, andpotential applications of a novel carbon nanotube material, named shear-pressed sheet. This material isfabricated from the chemical vapor deposition grown, tall aligned carbon nanotube arrays, with the use ofautomated shear-pressing device. It was shown that such sheets, having typically 50-200 micron thickness,are self-sustained and sufficiently stiff to be removed from the substrate, handled without the shapedistortion and then used either in a dry form or as a resin-infused prepreg for interleaving laminatedcomposites and their bonded joints. Extensive set of double-cantilever beam tests of composite laminateswith integrated shear-pressed sheets showed substantial, up to two times, improvement in the Mode Iinterlaminar fracture toughness. Experimental single-lap and double-lap joints of composites withintegrated shear-pressed sheet interleaves were manufactured and experimentally evaluated. Embeddedcarbon nanotube shear-pressed sheets and the added carbon nanotube drawn sheets showed excellentelectrical resistance sensitivity and thus a potential for being used as in-situ strain and damage monitoringnetworks and devices which are practically non-intrusive and may simultaneously provide significantfracture toughness enhancements. Distribution StatementThis is block 12 on the SF298 form.DISTRIBUTION A: Distribution approved for public release. Distribution A Approved for Public Release Explanation for Distribution StatementIf this is not approved for public release, please provide a short explanation. E.g., contains proprietary information. SF298 FormPlease attach your SF298 form. A blank SF298 can be found here. Please do not password protect or secure the PDFThe maximum file size for an SF298 is 50MB. SF298_NCSU Bogdanovich Report Documentation Page.pdf Upload the Report Document. File must be a PDF. Please do not password protect or secure the PDF . Themaximum file size for the Report Document is 50MB. NCSU Bogdanovich Final Report.pdf Upload a Report Document, if any. The maximum file size for the Report Document is 50MB. Archival Publications (published) during reporting period: Ang Li, Alexander E. Bogdanovich and Philip D. Bradford, "Aligned carbon nanotube sheet piezoresistivestrain sensors". Smart Materials and Structures, 2015, Vol. 24, 095004, 10 pp.; doi:10.1088/0964-1726/24/9/095004. Changes in research objectives (if any):