SAMPE Journal - January/February 2022 - 29

Physical Property
Tensile Modulus
Tensile Strength
Brown-Forsythe
Test
Welch's ANOVA Shapiro-Wilke
Test
Unequal Variances Means Statistically
Equal
Variances Equal
Tensile Elongation Variances Equal
Flex Modulus
Flex Strength
ILSS
Means Statistically
Different
Means Statistically
Equal
Unequal Variances Means Statistically
Different
Variances Equal
Variances Equal
Means Statistically
Equal
Means Statistically
Different
for the resin on the mechanical properties of the
composite panels was investigated through detailed
statistical analysis of experimental measurements.
The degree of cure achieved following each
process history is plotted in Figure 8 separately as
a function of the tensile modulus, tensile strength,
flex modulus, flex strength and the interlaminar
shear strength for the glass fiber panels produced
under various processing conditions. In each case,
the data was analyzed using one way analysis of
variance (one way ANOVA) methodology. TukeyKramer
plots at 95% confidence interval were
employed to asses the statistical similarity of the
means. The Brown-Forsythe test or F-Ratio test
was used compare the variances for data obtained
at each processing condition. Shapiro- Wilke test
was used to examine whether the data followed a
normal distribution. The results of the analysis are
compared for each property in Table 2.
As shown in Table 2, the means are found to be
statistically equal as a function of degree of cure
for tensile modulus, tensile elongation, and flex
strength at 95% confidence interval based on the
Tukey Kramer analysis; however, the means are
found to be statistically different for tensile strength,
flex modulus, and interlaminar shear strength, as a
function of the degree of cure. Irrespective of the
similarity between the means or lack thereof, it
is clear from a careful inspection of the results in
Figure 8 that the means of various properties do
not exhibit any systematic trend as a function of
the degree of cure, as summarized in Table 2. One
exception is the tensile strength, where a slight
decrease in tensile strength is noted with increasing
degree of cure from 0.87 to 0.92, which is followed
by an increase at a degree of cure of 0.95. Overall,
the results presented in this work demonstrate
that the nominal variations in the degree of cure
from 95 to 87% do not have any systematic on
impact the measured mechanical properties of
the composites panels fabricated under various
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Not normally
Distributed
Normally
Distributed
Not normally
Distributed
Normally
Distributed
Normally
Distributed
Normally
Distributed
Trend with increasing
degree of cure
None Noted
Slight decrease from
0.87 to 0.92
None Noted
None Noted
None Noted
None Noted
Table 2. Statistical analysis of
the effect of degree of cure
on mechanical performance
of glass fiber reinforced
panels produced at various
processing conditions.
Figure 8. Statistical analysis of mechanical properties as a function
of degree of cure using one way ANOVA method a) Tensile modulus b)
Tensile strength c) Tensile elongation d) Flex modulus e) Flex strength f)
Interlaminar shear strength.
process conditions. While mechanical properties
such as tensile and flex properties are strongly
dependent on the type and loading of the fiber
reinforcements, the lack of any trend as a function
of the degree of cure demonstrates the consistency
of translation of fiber properties by the resin. The
short beam shear strength is a measure of both
the matrix shear strength and the strength of the
fiber - matrix interface.13
The consistency of the
short beam shear strength for the various process
JANUARY/FEBRUARY 2022
|
SAMPE JOURNAL | 29
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SAMPE Journal - January/February 2022

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