TITLE:
Indirect Tensile Characterization of Graphite Platelet Reinforced Vinyl Ester Nanocomposites at High-Strain Rate
AUTHORS:
Brahmananda Pramanik, P. Raju Mantena, Tezeswi Tadepalli, Arunachalam M. Rajendran
KEYWORDS:
Split Hopkinson Pressure Bars, High-Strain Rate Tensile Test, Brazilian Disk Test Method, Laser Occluding Expansion Gage, Nanocomposites
JOURNAL NAME:
Open Journal of Composite Materials,
Vol.4 No.4,
October
24,
2014
ABSTRACT: An
indirect tensile testing method is proposed for characterizing low strength
graphite platelet reinforced vinyl ester nanocomposites at high-strain rate. In
this technique, the traditional Brazilian disk (diametrical compression) test
method for brittle materials is utilized along with conventional split-Hopkinson
pressure bars (SHPB) for evaluating cylindrical disk specimens. The cylindrical
disk specimen is held snugly in between two concave end fixtures attached to
the incident and transmission bars. To eliminate the complexities of
conventional strain gage application, a non-contact Laser Occluding Expansion
Gage (LOEG) has been adapted for measuring the diametrical transverse expansion
of the specimen under high-strain rate diametrical compressive loading. Failure
diagnosis using high-speed digital photography validates the viability of
utilizing this indirect test method for characterizing the tensile properties
of xGnP (exfoliated graphite nanoplatelets) reinforced and additional CTBN
(Carboxyl Terminated Butadiene Nitrile) toughened vinyl ester based
nanocomposites. Also, quasi-static indirect tensile response agrees with
previous investigations conducted using the traditional dog-bone specimen in
direct tensile tests. Investigation of both quasi-static and dynamic indirect
tensile test responses shows the strain rate effect on the tensile strength and
energy absorbing capacity of the candidate materials. The contribution of
reinforcement to the tensile properties of the candidate materials is
presented.