Carbon Nanotubes to Improve Mechanical Properties of Epoxy Matrix Composites Eliza Montgomery The Pennsylvania State University Physics and Applications of Nanoscale 1D Systems Dr. Slava Rotkin – Lehigh University

CNT in Epoxy Matrix Increase mechanical properties Replace current carbon fiber and carbon black reinforcement materials Increase mechanical properties Enhance electrical and thermal properties* Proposed as a damage-sensing component* *will not be addressed in this presentation

Objectives Compare tensile properties of different carbon reinforcement materials for epoxy-based composites: single, double, and multi-wall nanotubes with and without functionalisation to carbon black Address dispersion issues of carbon material in epoxy related to tensile properties

Methods of Dispersion in Epoxy Matrix DWCNT with NH2 functionalisation: Dispersed into epoxy via calandering Dispersed into epoxy via sonification FH Gojny, MHG Wichnamm, U Kopke, B Fiedler, K Schulte, Composites Science and Technology 64 (2004) 2363-2371 Schwarz, Ebeling, Furth, Kunststoffverarbeitung. Vogel Buchverlag 2002. Three-roll calander used for the effective dispersion of carbon nanotubes in an epoxy matrix (a). The flow conditions in the roller clearance are schematically shown (b) Schematic of calendering process: Sonification-poses problems due to extreme vibration Calandering method used to achieve dispersion after stirring Carbon black dispersed via calandering.

Why Functionalize? e) SWNT SSA = 1300m2/g f) Carbon black SSA = ~1m2/g or less Epoxy/MWCNT b) w/ and a) w/out NH2 SSA = 200m2/g DWNT c) w/out and d) w/ NH2 SSA = 600-800m2/g Dispersion and Surface Specific Area (SSA) of Functionalized CNTs High SSA values positively relate to stress transfer due to increased interfaces between CNT and matrix High SSA values negatively relate to dispersion by increasing strong attractive forces between CNTs that lead to excessive agglomeration. Functionalisation decreases the SSA, leading to better dispersion. FH Gojny, MHG Wichmann, B Fiedler, K Schulte, Composites Science and Technology 65 (2005) 2300-2313 Interfacial adhesion between CNT and matrix polymer. Improves interfacial stress transfer and dispersion of CNT in matrix Specifically: CNT is amino-functionalised to enable covalent bonding between CNT and epoxy. Relation of amino-groups to the number of surface carbon atoms of the CNT is ~ 1/100.

Mechanical Properties Strength Stiffness Fracture toughness DWNT chosen: best improving mechanical strength overall FH Gojny, MHG Wichmann, B Fiedler, K Schulte, Composites Science and Technology 65 (2005) 2300-2313

Highlights for DWCNT in Epoxy Matrix a) w/out and b) w NH2 Stress vs. strain = functionalized performed best SEM micrographs of fracture surfaces FH Gojny, MHG Wichmann, B Fiedler, K Schulte, Composites Science and Technology 65 (2005) 2300-2313

Conclusions Dispersion difficult with larger SSA (all CNTs). Functionalism improved dispersion of CNTs in epoxy matrix for all cases. Addition of DWNT with 0.5% filler increased mechanical properties best: 10% strength, 15% stiffness, and 43% fracture toughness.

Thank you Questions? Presentation primarily based on works by Gojny et al, 2003-2005