Center for Composite Materials - University of Delaware

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

302-831-8149 • info-ccm@udel.edu | © 2017 University of Delaware