SAMPE Journal - March/April 2023 - 25

where:
E = flexural modulus, MPa
m = slope of the tangent to the initial straight-line
portion of the load-deflection curve, N/mm
Interlaminar Shear Strength (ILSS) Testing
ILSS
test
of
the
composites was performed
according to ASTM D2344 using the Test Resource
Universal Testing Machine (Model 313 series frame,
MN) with 50 kN load cell and at the rate of 1 mm/
min. ILSS samples were tested in the same fashion
as flexure. Five specimens for each sample set were
tested and the average ILSS value was reported.
ILSS values can be calculated using Equation 3.
[3]
where:
P = maximum load observed during the test, N;
b = measured specimen width, mm;
h = measured specimen thickness, mm.
Scanning Electron Microscopy (SEM)
The fractured samples of the flexural test were
analyzed using a Hitachi
TM3030
Sample
BF-PP
Density (g/cm3
0.9800±0.0006
)
BF-PP-TCF (0/0) 0.9950±0.0013
BF-PP-TCF (0/90) 0.9853±0.0010
Table 1. Density of BF-PP, BF-PP-TCF (0/0) and
BF-PP-TCF (0/90).
have suggested that preheating continuous fiberreinforced
laminates before overmolding enhances
interfacial bonding between the continuous fiberreinforced
laminates and short fiber reinforced
composites which further results in improved
mechanical properties13,14
. Furthermore, the PP
matrix used for preparing TCF tape and the one
used for BF-PP composite was of same grade which
another reason for the excellent bonding between
the tape and BF-PP composite. Figure 3b shows
distinct resin and fiber-rich regions which might be
due to the non-uniform spreading of fibers while
manufacturing TCF tape.
Flexural properties of BF-PP, BF-PP-TCF (0/0)
electron
microscope. Images were used to understand the
interfacial bonding and failure mode.
RESULTS AND DISCUSSION
Density Measurement
Table 1 represents the summary of the density of
BF-PP, BF-PP-TCF (0/0), BF-PP-TCF (0/90). The TCF
tape had 20wt% TCF and 80wt% PP. Based on that,
the average amount of TCF in the TCF overmolded
BF-PP composites was approximately 2wt%. The
results show that overmolding two layers of TCF
tape on BF-PP composite had minimal influence
on the density of the final composites which is
probably due to the less amount (i.e. 2wt%) of TCF
in the composite.
Flexural Testing and Morphology
Figure 3 illustrates the SEM micrographs of the
polished cross-sections of BF-PP-TCF (0/0) and
BF-PP-TCF (0/90) composites. SEM micrographs
illustrate strong interfacial bonding between the
TCF tape and BF-PP, which might be due to the preheating
of TCF tape before overmolding. Studies
and BF-PP-TCF (0/90) are summarized in Figure
4a. From literature, flexural strength and modulus
of the similar grade of PP were found to be 36.36
MPa and 0.81 GPa respectively15
. On adding 20wt%
bamboo fiber, flexural strength and modulus of the
composite were increased to 47.38 MPa and 2.36
GPa respectively which was 30% and 191% increase
respectively as compared to neat PP. Kore et al.1
also observed 36% and 58% increase in flexural
strength and modulus on adding 30wt% BF in PP.
Load-displacement curve of the BF-PP represented
in Figure 4b show linear deformation and ductile
failure, which can be confirmed in the SEM image
(Figure 5d) of the fractured BF-PP sample.
In case of hybrid composites, reinforcing fiber
position or the orientation of laminate strongly
influences the mechanical properties of the
composites. On overmolding unidirectional layers
of TCF tape, flexural strength and modulus of the
BF-PP increased significantly by ~152 % and ~164
% respectively. This enhancement in strength and
modulus was due to the improved directional
load transfer and stiffness of TCF which offered
higher resistance upon compression load15,16
On overmolding 0/90 layers of TCF tape, flexural
.
Figure 2. Schematic of flexure and/or ILSS testing condition as TCF tape was on the bottom side.
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SAMPE Journal - March/April 2023

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