SAMPE Journal - January/February 2020 - 19
mm), and the stacking sequences of thin and thick
specimens were set to [08]T (nominal thickness
after cure: 1.2 mm) and [032]T (nominal thickness
after cure: 4.8 mm), respectively. Two samples
were made for each thickness (total four samples
were fabricated): one with distributed optical fiber
sensors for internal strain monitoring and one
without optical fiber for weight measurement.
The optical fibers were placed between 4-5 plies
in the thin specimen and between 4-5, 10-11, and
16-17 plies in the thick specimen during layup.
Figure 5 illustrates the photograph of a sample
with schematic of embedded optical fiber and its
cross section. The optical fibers were placed in the
specimens and extracted from edges of the samples
(Figure 5 (a)). After laying all the prepreg sheets on
an aluminum tool, it was vacuumed and cured in an
oven. The cure cycle included 1.5°C/min heating,
120°C holding for 3 hours, and 1.5°C/min cooling
to room temperature. Temperatures of the samples
were monitored using thermocouples attached on
the vacuum bag, showing that the samples were
cured under proper heat cycle. After curing, the
edges of each sample were trimmed approximately
5 mm to make smooth edge surfaces. Note that the
areas where the optical fibers were extracted were
not cut to enable optical monitoring (Figure 5 (a)).
Moisture absorption and desorption tests were
carried out using the four specimens. First,
the specimens were dried in a vacuum oven
to eliminate water molecules trapped in the
samples during storage after fabrication. Then, the
samples were placed in a thermo-hygrostat bath
controlled to 70ºC/85 %RH for strain and weight
measurement induced by moisture absorption.
After the absorption test, the samples were
moved to a vacuum oven controlled to 90ºC to
monitor strain and weight changes accompanied
Figure 4. Reflected spectrum. (a) waveform at each scatter point, (b) synthesized waveform.
by moisture desorption. Strain was measured
throughout both tests using the distributed optical
fiber sensor system with the sampling interval of
5 mm. Meanwhile, the three different areas were
named along the fiber longitudinal direction: near
edge (Area 1), center (Area 3), and between them
(Area 2) (Figure 5 (a)). Strain at each area was
calculated by averaging measured values at three
points near the center in each area. Weight changes
of the two samples without optical fibers were also
recorded using an electronic balance at several
points during the tests.
Figure 5. Configuration of specimens. (a) photograph with schematic of embedded optical fiber
sensor, (b) cross sections of 8 and 32-ply (A-A' in (a)).
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http://www.sampe.org
SAMPE Journal - January/February 2020
Table of Contents for the Digital Edition of SAMPE Journal - January/February 2020
Table of Contents
SAMPE Journal - January/February 2020 - Cover1
SAMPE Journal - January/February 2020 - Cover2
SAMPE Journal - January/February 2020 - Table of Contents
SAMPE Journal - January/February 2020 - 2
SAMPE Journal - January/February 2020 - 3
SAMPE Journal - January/February 2020 - 4
SAMPE Journal - January/February 2020 - 5
SAMPE Journal - January/February 2020 - 6
SAMPE Journal - January/February 2020 - 7
SAMPE Journal - January/February 2020 - 8
SAMPE Journal - January/February 2020 - 9
SAMPE Journal - January/February 2020 - 10
SAMPE Journal - January/February 2020 - 11
SAMPE Journal - January/February 2020 - 12
SAMPE Journal - January/February 2020 - 13
SAMPE Journal - January/February 2020 - 14
SAMPE Journal - January/February 2020 - 15
SAMPE Journal - January/February 2020 - 16
SAMPE Journal - January/February 2020 - 17
SAMPE Journal - January/February 2020 - 18
SAMPE Journal - January/February 2020 - 19
SAMPE Journal - January/February 2020 - 20
SAMPE Journal - January/February 2020 - 21
SAMPE Journal - January/February 2020 - 22
SAMPE Journal - January/February 2020 - 23
SAMPE Journal - January/February 2020 - 24
SAMPE Journal - January/February 2020 - 25
SAMPE Journal - January/February 2020 - 26
SAMPE Journal - January/February 2020 - 27
SAMPE Journal - January/February 2020 - 28
SAMPE Journal - January/February 2020 - 29
SAMPE Journal - January/February 2020 - 30
SAMPE Journal - January/February 2020 - 31
SAMPE Journal - January/February 2020 - 32
SAMPE Journal - January/February 2020 - 33
SAMPE Journal - January/February 2020 - 34
SAMPE Journal - January/February 2020 - 35
SAMPE Journal - January/February 2020 - 36
SAMPE Journal - January/February 2020 - 37
SAMPE Journal - January/February 2020 - 38
SAMPE Journal - January/February 2020 - 39
SAMPE Journal - January/February 2020 - 40
SAMPE Journal - January/February 2020 - 41
SAMPE Journal - January/February 2020 - 42
SAMPE Journal - January/February 2020 - 43
SAMPE Journal - January/February 2020 - 44
SAMPE Journal - January/February 2020 - 45
SAMPE Journal - January/February 2020 - 46
SAMPE Journal - January/February 2020 - 47
SAMPE Journal - January/February 2020 - 48
SAMPE Journal - January/February 2020 - 49
SAMPE Journal - January/February 2020 - 50
SAMPE Journal - January/February 2020 - 51
SAMPE Journal - January/February 2020 - 52
SAMPE Journal - January/February 2020 - 53
SAMPE Journal - January/February 2020 - 54
SAMPE Journal - January/February 2020 - 55
SAMPE Journal - January/February 2020 - 56
SAMPE Journal - January/February 2020 - 57
SAMPE Journal - January/February 2020 - 58
SAMPE Journal - January/February 2020 - 59
SAMPE Journal - January/February 2020 - 60
SAMPE Journal - January/February 2020 - 61
SAMPE Journal - January/February 2020 - 62
SAMPE Journal - January/February 2020 - 63
SAMPE Journal - January/February 2020 - 64
SAMPE Journal - January/February 2020 - Cover3
SAMPE Journal - January/February 2020 - Cover4
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