Multiscale Measurements Laboratory


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

This research program is focused on developing appropriate macro-mechanical models that account for the meso-structural details unique to X- and K-Cor composite sandwich panels. Currently, there is no simulation capability for predicting the mechanical behavior of structures that are fabricated using these novel composite materials. Therefore, a new modeling approach is proposed utilizing multiscale Finite Element models that are enriched using experimental details of the deformation response resulting in a hybrid numerical-experimental simulation. To obtain the experimental data, a novel mechanical characterization technique known as Digital Image Correlation (DIC) is used to elucidate on the details of the deformation fields within the sandwich structure in different loading states. These details enhance the Finite Element models by providing critical details on the elastic loading distributions, failure initiation mechanisms, and the subsequent load redistribution that occurs in these structures.

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.

Multifunctional Compliant Wing Structures for Micro-air Vehicles

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:

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.