SAMPE Journal - March/April 2023 - 24

FEATURE / BAMBOO FIBER
the bonding behavior of TCF tape with BF-PP and
fracture mechanism(s). To the best of the authors'
knowledge, no study on the overmolding of CF tape
on BF-PP composites has been done.
MATERIALS AND METHODS
Materials
PP pellets (ExxonMobil™ PP3155 homopolymer,
density-900kgm-3
) were procured from
ExxonMobil™, North America, and BF of
fiber length of 0.4-7mm were obtained from
BioResources, Homewood, Alabama, USA. TCF
tape with a fiber content of 20wt% was prepared at
the Fibers and Composites Manufacturing Facility
(FCMF), University of Tennessee, Knoxville using
an in-built thermoplastic melt impregnation line.
Composites Manufacturing
From here onwards, TCF tape overmolded BFPP
composites are referred to as BF-PP-TCF.
Overmolding of BF-PP-TCF composites comprised
of two stages: (1) preparing the consolidated panel
of TCF tape with two different configurations (0/0
and 0/90) and, (2) overmolding the consolidated
tape panel with BF-PP via ECM technique.
In the first stage, for each configuration, two
layers of TCF tape were arranged in a two-cavity
mold (280mm×280mm) mounted to a Carver press
(Model# 3895.4NE1000, Carver, Inc. USA, 30 metric
tons). The temperature of the press was set at 180°
and a pressure of 5 tons (82.6 psi) was applied for
5 mins of dwell time. The samples were cooled to
room temperature to obtain the consolidated TCFPP
panel.
In the second stage, the consolidated tape panel
was placed on a Kapton film (product#2271K3
McMaster-Carr, USA). Kapton adhesive (product#
1754N13, McMaster-Carr, USA) tape was used to
hold the panel on the Kapton film. The setup was
then placed in an oven
set to 200°C. A low shear
single screw B-30 Impco plasticator was used for
compounding PP and BF. The temperature of the
four different heating zones of the plasticator were
set to 190, 195, 200, 205°C respectively. Simple
blended PP pellets and 20wt% BF were fed into the
plasticator through a vibratory feeder.
The pre-heated consolidated tape panel was
placed into a 305mm×305mm aluminum mold
mounted in a 150-ton fast acting Wabash hydraulic
compression press and the hot BF-PP charge from
the plasticator was placed on the top of the tape. 45
tons (625psi) pressure was applied for 1min dwell
time, and the consolidated panels were used for
further characterization. The manufacturing stages
of the bamboo-overmolded tape panel are shown
in Figure 1.
Testing and Analysis
Density Measurement
Micromeritics AccuPyc II 1340 gas pycnometer
was used to measure the density of the samples
according to the ASTM D5550-14 standard.
Samples of mass 0.25-0.5g were used for the density
measurement.
Flexural Testing (Three-Point Bend Test)
Test Resource Universal Testing Machine (Model
313 series frame, MN) with 50 kN load cell was used
to perform three-point bend test of the composites
in accordance with ASTM D790. Flexural test was
conducted such that the TCF layer was on the
bottom (tensile) side for overmolded samples as
shown in Figure 2. Five specimens for each sample
set were tested and the average flexural properties
were reported. Flexural strength and modulus can
be calculated using Equation 1 and 2 respectively.
[1]
where:
σf
= flexural stress, MPa;
P = load at the given point on load displacement
curve, N;
L = support span, mm;
b = width of specimen, mm;
d = depth of specimen, mm.
[2]
Figure 1. Schematic of fabrication of TCF overmolded BF-PP panels via ECM. TCF tape prepared
from in-built thermoplastic impregnation line was overmolded with BF-PP charge produced from
plasticator.
24 | SAMPE JOURNAL | MARCH APRIL 2023
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