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<p>Fiber reinforced polymer
composites are widely used in manufacturing advanced light weight structures
for the aerospace, automotive, and energy sectors owing to their superior
stiffness and strength. With the increasing use of composites, there is an increasing
need to monitor the health of these structures during their lifetime.
Currently, health monitoring in filament wound composites is facilitated by
embedding piezoelectrics and optical fibers in the composite during the
manufacturing process. However, the incorporation of these sensing elements
introduces sites of stress concentration which could lead to progressive damage
accumulation. In addition to introducing weak spots in the structure, they also
make the manufacturing procedure difficult. </p>
<p> </p>
<p>Alternatively,
nanofiller modification of the matrix imparts conductivity which can be
leveraged for real time health monitoring with fewer changes to the
manufacturing method. Well dispersed nanofillers act as an integrated sensing
network. Damage or strain severs the well-connected nanofiller network thereby
causing a local change in conductivity. The self-sensing capabilities of these
modified composites can be combined with low cost, minimally invasive imaging
modalities such as electrical impedance tomography (EIT) for damage detection.
To date, however, EIT has exclusively been used for damage detection in planar
coupons. These simple plate-like structures are not representative of
real-world complex geometries. This thesis advances the state of the art in
conductivity-based structural health monitoring (SHM) and nondestructive
evaluation (NDE) by addressing this limitation of EIT. The current study will
look into damage detection of a non-planar multiply connected domain – a
filament-wound glass fiber/epoxy tube modified by carbon black (CB) filler. The
results show that EIT is able to detect through holes as small as 7.94 mm in a
tube with length-to-diameter ratio of 132.4 mm-to-66.2 mm (aspect ratio of
2:1). Further, the sensitivity of EIT to damage improved with decreasing tube
aspect ratio. EIT was also successful in detecting sub-surface damage induced
by low velocity impacts. These results indicate that EIT has much greater
potential for composite SHM and NDE than prevailing work limited to planar geometries
suggest.</p>
</div>
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| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/8983763 |
| Date | 02 August 2019 |
| Creators | Akshay Jacob Thomas (7026218) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/STRUCTURAL_HEALTH_MONITORING_OF_FILAMENT_WOUND_GLASS_FIBER_EPOXY_COMPOSITES_WITH_CARBON_BLACK_FILLER_VIA_ELECTRICAL_IMPEDANCE_TOMOGRAPHY/8983763 |
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