Research Summary
Glass Fiber/Carbon Nanotube Multiscale Hybrid Composites via Electrophoretic Deposition
Authors: Qi An (Ph.D.), Andrew N. Rider and Erik T. Thostenson
INTRODUCTION AND MOTIVATION
• Interphase: a significant role in
o Load transfer mechanisms, composite strength & toughness
• Nano-scale additives: carbon nanotubes (CNT)
o Small volume fractions, occupy resin-rich interstitial regions
o Improve matrix-dominated properties
• Electrophoretic deposition (EPD):
o Environmentally-friendly ambient temperature, water-based
o Control over functionality, industrially scalable and economy
PROCESSING AND MANUFACTURING
1) Nanotube Dispersion and Functionalization
• Polyethyleneimine (PEI)-ozone functionalization under sonication:
o Single step dispersion/functionalization
o Highly stable dispersion
o Chemical bonding, toughener
2) Nanotube Integration in Fabric
• Fabric tensioner: intimate contact, 800mm2 even coating
• Field strengths: 12 ~ 64 V/cm
• Double-sided coating
3) Composite Manufacturing
• Flow media: improved infusion
• Double bag: uniform part thickness
• EPON 862 and Epi-Kure W infused at 55°C, 6 hour cure at 130°C
DEPOSITION AND CHARACTERIZATION
• Outer fiber coating: uniform film, ~2mm
• Fiber-tow interior coating: 50nm~200nm
• CNT network spans between adjacent fibers
• Deposition rate on glass fibers is about half of carbon
MECHANICAL PROPERTIES
• The shear strength increases in direct proportion to the CNT concentration and leads to 80% increase for the highest VCNTs
• Fracture morphology changed from brittle to plastic
• Fracture path switch indicates good fiber /CNT adhesion
MICROMECHANICS MODELING
• Halpin-Tsai equations: modified for 3-D random-alignment CNT reinforcement in the matrix by assuming CNT coating is a constituent of the resin
• Shear modulus increase 30% at 16% VCNT / Vm
• Match Grandom in the model with measured G12 by assuming different filler aspect ratios
o lf /df=10 fits only for low CNT VCNT/Vm
• The current model over-estimates the shear modulus, which may be related to the locally graded distribution of nanotubes throughout the matrix
ELECTRICAL PROPERTIES
Anisotropic conductivity:
CONCLUSIONS
• EPD can be successfully applied to coat insulating glass fibers for the preparation of CNT-modified glass/epoxy composites
• In-plane shear strength and electrical conductivity can be increased significantly over the baseline
• Modulus modeling using Halpin-Tsai equations estimated the stiffness increase expected for the CNT concentrations in the laminate
• CNT glass laminate with an electrically conducting network gives the potential of damage sensing
Acknowledgements
This research is funded by National Science Foundation (grant #1254540) Mary Toney, Program Director and the US Army Program Executive Office: Soldier and the Army Research Laboratory under Cooperative Agreement Number W911NF-06-2-011
