Polyme Analysis 2010 Part 4 pot
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ü Most commonly the specimen lies on a span and the load is
applied to the centerby the loading nose producing three point
bending at a specified rate.
üThe parameters for this test are :
+The support span;
+The speed of the loading
+The maximum deflection for the test.
These parameters are based on the test specimen
thickness, and are defined differently by ASTM and ISO.
Specimen Size:
üA variety of specimen shapes can be used
üThe most commonly used specimen size:
+ 3.2mm x 12.7mm x 125mm for ASTM D790
+10mm x 4mm x 80mm for ISO 178
Test Procedure:
Flexural test
üFlexural strength
üFlexural modulus
Flexural test
b
b
L
F
δ
3
3
4 hb
Lm
E
b
=
2
2
3
hb
LF
b
=σ
m : initial slope of the load vs. deflection curve
For relatively thin samples → two point loading
For thick samples → 4 point loading
Flexural test
Izod Impact Testing
(Notched Izod)
üNotched IzodImpact is a single point test that measures
a materials resistance to impact from a swinging
pendulum.
ü Izodimpact is defined as the kinetic energy needed to
initiate fracture and continue the fracture until the
specimen is broken.
üIzodspecimens are notched to prevent deformation of
the specimen upon impact.
üThis test can be used as a quick and easy quality control
check to determine if a material meets specific impact
properties or to compare materials for general toughness.
Scope:
ü 64 x 12.7 x 3.2 mm for ASTM D256
üThe preferred thickness is 6.4 mm because it is not as likely tobend or crush
üThe depth under the notch of the specimen is 10.2 mm
ü80 x 10 x 4 mm forISO 180
üThe depth under the notch of the specimen is 8mm
Specimen Size:
Izod Impact Testing
(Notched Izod)
üThe specimen is clamped into the pendulum impact test
fixture with the notched side facing the striking edge of the
pendulum.
üThe pendulum is released and allowed to strike through
the specimen.
üIf breakage does not occur, a heavier hammer is used
until failure occurs.
üSince many materials (especially thermoplastics) exhibit
lower impact strength at reduced temperatures ⇒ to test
materials at temperatures that simulate the intended end
use environment
izodimpact.wmv
Izod Impact Testing
(Notched Izod)
Test Procedure:
üThe specimens are conditioned at the specified temperature in a freezer
until they reach equilibrium.
üThe specimens are quickly removed, one at a time, from the freezer and
impacted.
üNeither ASTM nor ISO specify a conditioning time or elapsed timefrom
freezer to impact -typical values from other specifications are 6 hours of
conditioning and 5 seconds from freezer to impact.
Reduced Temperature Test procedure:
ASTM
üImpact energy is expressed in J/m or ft-lb/in.
üImpact strength is calculated by dividing impact energy in J (orft-lb) by the
thickness of the specimen.
üThe test result is typically the average of 5 specimens.
ISO
üImpact strength is expressed in kJ/m
2
üImpact strength (a
cU
)is calculated by dividing impact energy in J by the
area under the notch.
Data
3
cU
10a ×=
bh
W
W: energy
b = width of the sample
h = thickness of the sample
üThe test result is typically the average of 10 specimens.
The higher the resulting number, the tougher the material.
