1. 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

2. 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

3. 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

4. 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)
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.

5. 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 = m2/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)
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.

6. 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)

7. 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)

8. 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.

9. Thank you Questions?
Presentation primarily based on works by Gojny et al,