Center for Composite Materials - University of Delaware

Research Summary

Processing and Characterization of Carbon-Based Nanocomposites for Sensing Applications

Authors: Sarah M. Masters (BME), Zachary R. Melrose (MME) and Erik T. Thostenson

INTRODUCTION AND MOTIVATION

- Fiber reinforced composites are preferable to traditional metal alternatives in high performance applications due to their low specific weight, resistance to corrosion and high specific strength.

- Carbon nanotubes (CNT) have been proven to provide electrically conductive networks that can be used for sensing the onset and accumulation damage in composite materials.
-- The introduction of previously untested carbon allotropes into nanocomposites could produce more sensitive sensors while reducing the cost and increasing the strength of sensing nanocomposites.

- The varied surface geometries and agglomerated nature of graphite/graphene and CNT present us with processing challenges and the need to develop new procedures.
-- Research is aimed at increasing the multifunctional capabilities of nano-modified composites

SYNTHESIS AND PROCESSING

- Carbon nanomaterials are dispersed into vinyl ester using a high precision calendering mill.
-- Shear mixing degrades agglomerates, while limiting damage to the nanomaterials.
-- Speed and gap settings control dispersion.

- Commercial vinyl ester resins contain ~40% styrene, a volatile liquid that inhibits calendering.

- Synthesis of vinyl ester monomer from epoxy (EPON 862), enables dispersion in the monomer.
-- Post-milling, the styrene introduction enables crosslinking of the vinyl ester monomer for nano-resin synthesis.

MANUFACTURING

- Composite parts are manufactured using Vacuum Assisted Resin Transfer Molding (VARTM).

- Composites consist of 8 layers of unidirectional E-glass infused with vinyl ester/nanomaterial resin.

CHARACTERIZATION

- Tensile specimens are evaluated under monotonic quasi-static tensile conditions.

- Customized data acquisition system records mechanical deformation and electrical response data during testing.

- Electrical properties evaluated using ASTM techniques.

CARBON NANOSTRUCTURES

- Graphene is a one-atom-thick planar sheet of carbon atoms arranged in a hexagonal pattern.
xGnP M-15 graphene nanoplatelets are used.

- Graphite is made up of many layers of graphene.

- Graphene that is wrapped cylindrically forms CNT.

- Carbon black is a nano-
scale carbonaceous material.
-- Ketjen Black EC-600JD, a low cost, commercially-available nano-filler used for improving electrical conductivity, is tested.


MECHANICAL RESPONSE

- Intensity of calendering schedule and Young’s Modulus have a direct relationship in nanomaterial/E-glass composite specimen.

ELECTRICAL PROPERTIES

- Electrical resistivity shows a strong dependence on processing procedures in resin samples.

CONCLUSIONS

- Multifunctionality is strongly influenced by nanomaterial processing intensity.

- Highly processed graphene shows promise as a replacement for CNT in damage detecting nanocomposites given its electrical resistivity and mechanical properties.

FUTURE WORK

- Optimize processing of graphene nano-composites for sensing capabilities.

- Explore novel hybrid nanocomposites comprised of graphene and CNT.

ACKNOWLEDGEMENTS

This material is based upon work supported by the National Science Foundation under Grant No. (1138182), Mary Poats, Program Director.

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