The Young's modulus and tensile strength of the epoxy nanocomposites
were determined using an Instron 8800 microforce
tester at a crosshead speed of 1 mm/min according to ASTM D-638.
Dog-bone bars (Type V) were machined using a Ceast contour
cutter. The critical stress intensity factor (K1C) was measured according
to ASTM D5045 using Single-Edge-Notch 3-Point-Bend
(SEN-3PB) testing with a span of 50.8 mm and the specimen dimensions
were 60 12.7 6.0mm3. A sharp notch was introduced
by pressing a fresh razor blade at the bottom of a saw-slot in the
middle of the test bar. The measurements were conducted on an
Instron 8800 at a crosshead speed of 1 mm/min. The K1C values
were calculated using the following equations: