Dynamic
Damage Mechanisms in Hierarchically-structured Polymer Composites for
Multifunctional Marine Structures
This project is focused on
creating hierarchically-structured polymer composites using VARTM
processing
for multifunctional marine structures in order to elucidate on dynamic
damage
mechanisms. This is accomplished through (a) processing of model
hierarchically-structured polymer composites for VARTM using carbon
nanofibers
(CNFs), carbon nanotubed (CNTs), and carbon microfibers (CMFs) in
marine
epoxies, (b) multi-scale characterization and modeling of processing
effects on
the hierarchical structure, (c) static and dynamic mechanical
experiments to
characterize damage mechanisms using both Split Hopkinson Pressure Bar
tests
providing dynamic constitutive response and three-point bend static and
dynamic
tests providing interfacial failure will be conducted, (d)
characterization of
full-field deformations associated with the damage mechanisms using the
measurement
technique of Digital Image Correlation (DIC), (e) development of multi-scale models of the dynamic damage
mechanisms using a combination of analytical formulas, dynamic FEA, and
micromechanical analysis based on techniques such as High Fidelity
Generalized
Method of Cells, (f) development of model multifunctional structures
relevant
to marine applications by integrating bio-inspired
hierarchically-structured polymer
composites or embedding electronic
components into sandwich structures, and (g) characterization of the
effects of
the embedded components and hierarchically-structured polymer
composites on the
dynamic damage mechanisms and subsequent multifunctional performance
can then
be characterized for developing a new performance index.
Principles for Formation of Transversely
Modulated Heterophase Nanostructures
We
propose to develop a new class
of materials with controlled transversely
modulated heterophase nanostructures (TMNS).
The proposed research will integrate
theory, modeling, experimental characterization, and design of
TMNS with controlled scale and morphology. The basic idea
of this research effort is to
design TMNS by exploiting epitaxial
self-assembling of constituent phases on
a crystalline substrate. Formation of
such self-assembled nanostructures requires the
establishing epitaxial relations between each phase and the substrate.
These epitaxial relations lead to
self-organization of constituent phases
and formation of 3D heteroepitaxial
nanostructures with coherent or
semi-coherent interfaces. By
selecting different substrates or substrate
orientations and changing the thickness
of the nanostructured layer, it is
possible to control morphology of the self-assembled
nanostructures on a scale that is difficult to obtain with other
techniques. Because of the nanoscale
of the component phases, dislocation-mediated
mechanisms are suppressed resulting in significant elastic strain.
Therefore, controlling this stress becomes a
new mechanism for
manipulating film properties,
similar to semiconductor heterostructures.
Mechanical Characterization and
Modeling of X- and K-Cor Composites
A New
Sensor-Actuator System for Health Management of Propellants
We
have been developing a new technique for characterizing the properties
of propellants
in order to quantify the deterioration of properties due to
damage/aging. This
technique involves embedding fiber brag grating (FBG) sensors combined
with shape
memory alloy (SMA) actuators in propellant (or propellant simulants) to
non-destructively interrogate the material and determine the change in
properties and the development of defects, such as cracks. We are also
using digital
image correlation to map the displacement fields associated with the
deformations of the propellant. This
will help us to understand how these sensors and actuators should be
embedded so
that the effects they have on the deformation fields in the propellant
can be
more accurately related to the properties of the propellant.
Furthermore, the
signals generated by the FBG-SMA system need to be directly related to
the changes
in the properties of the propellant via computational finite element
analysis
(FEA) in order to quantify the changes in properties due to
damage/aging.
The development
of lightweight
MAVs requires new technologies for enabling energy to be harvested
while the
MAV is operational in order to provide adequate energy for long-term or
long-distance missions. While technologies like flexible solar cells
and
piezofilms exist to “harvest energy” during missions, they are
difficult to
integrate into lightweight MAVs using their existing packaging because
the
added weight and stiffness decreases the load bearing capabilities and
increases the energy requirements of the MAVs. In order to overcome
these
limitations, direct integration of the critical energy harvesting
elements,
such as silicon, into the structure of MAV components, such as sings,
is
needed. This integration can be accomplished using transfer processes
where the
choice of substrate will play a more dominant role in the compliance of
the
structure, as it currently does. Compliant design issues can then focus
on the
thickness of the substrate, the elastic properties, the density, and
the
geometry and distribution of the energy harvesting element. The key to
realizing a complete understanding of compliant design for these new
“multifunctional structures” is the multi-stage multi-material molding
process
we have currently developed that enables us to completely integrate
electronic
components with polymer and polymer composite structural members. Thus,
we are
in a unique position to provide computationally-guided design
principles for
compliant multifunctional structures in energy harvesting applications
for
MAVs.
To see videos of our MAVS: http://terpconnect.umd.edu/~skgupta/UMdBird/
Electrical
Percolation Biological Semiconductors for Label Free Biosensors
The need
for
label-free biosensing is well recognized. Our
goal is to develop a label free biosensor based on electrical
percolation
detection of biomolecules and cells. This biosensor will be more
portable than
commercial ELISA-based detectors, and will be easier to fabricate than
other commercially-viable
label-free biosensor platforms such as FTE-based detectors. It takes
advantage
of subtle percolation changes unique to SWNTs that provides the desired
sensitivity, selectivity, and wide dynamic measurement range found in
the
alternative commercial and commercially-viable platforms. We have
developed a
unique commercially-viable process for functionalizing the sensitivity
of these
biosensors for the desired pathogen detection and deploying them on
Lab-on-a-Chip platforms using standard contact printing and layered
manufacturing fabrication techniques. Because of the low-cost and easy
of
fabrication, these biosensors can be easily deployed in a variety of
commercial
and military applications, such as detection of ligands associated with
cancer
and biological agents such as anthrax, as well as multiplexed detection
of
multiple biological agents. Development of this technology requires a
more
complete understanding of the transduction mechanism for converting the
biological agent into a detection signal (in this case changes in
voltage)
without crosstalk from similar biological agents that results in false
positives. However, the platform is inherently low-cost relying on very
small
quantities (<1 mg/ml) of SWNTs, antibodies, cheap plastics, and
cheap
electronics in a very small package.
