Monthly Archives June 2020

Lab member receives Fulbright Scholarship and DURA

We are very proud of Zachary Stein for receiving the Fulbright Scholarship and the Distinguished Undergraduate Researcher Award (DURA). Zac has been awarded the Fulbright Scholarship to Germany and will be conducting research on aircraft engines at the German Aerospace Center (DLR). Zachary has also been mentioned in the UCF’s Burnett Honors College spotlight, which you can see here.

He is one of nine students at UCF to receive the Fulbright Scholarship this year (Click here to learn more). The Fulbright U.S. Student Program offers research, study and teaching opportunities in over 140 countries to recent graduates and graduate students. Learn more at https://us.fulbrightonline.org/.

Each month DURA recognizes outstanding academic research by undergraduates at the University of Central Florida and Zachary was nominated for the month of July 2020. Students receive a scholarship, certificate, and recognition. For more information, go to https://our.ucf.edu/current/award-programs/.

Measurements for stress sensing of composites using tailored piezospectroscopic coatings

 

Read our paper in AIP Advances

Abstract:

Chromium-doped alpha-alumina is naturally photo-luminescent with spectral properties that are characterized by R-lines with two distinct peaks known as R1 and R2. When the material is subjected to stress, shifts in the R-lines occur, which is known as the piezospectroscopic (PS) effect. Recent work has shown that improved sensitivity of the technique can be achieved through a configuration of nanoparticles within a polymer matrix, which can be applied to a structure as a stress-sensing coating. This study demonstrates the capability of PS coatings in mechanical tests and investigates the effect of nanoparticle volume fraction on sensing performance. Here, measurements of spectral shifts that capture variation in stress of the coating during mechanical testing and in the region of substrate damage showed that stress contours are more noticeable on a soft laminate than hard laminate. It was found that the 20 % volume fraction PS coating showed the most distinct features of all the coatings tested with the highest signal-to-noise ratio and volume fraction of alpha-alumina. Post failure assessment of the PS coatings verified that the coatings were intact and peak shifts observed during mechanical testing were due to the stress in the substrate. The results suggest the ability to design and tailor the “sensing” capability of these nanoparticles and correlate the measured stress variations with the presence of stress and damage in underlying structures. This study is relevant to nondestructive evaluation in the aerospace industry, where monitoring signs of damage is of significance for testing of new materials, quality control in manufacturing and inspections during maintenance.

To view more posts like this, check out the Highlights page here.

You can also hear about Remelisa’s paper in the All Audio Posts page here.

Congrats to Our Recent Graduates of Spring 2020

Despite the difficulties presented by COVID-19, we are delighted to present the perseverance of lab members Khanh Vo, Johnathan Hernandez, Nicholas Reed, Remelisa Esteves, and Zachary Stein on successfully graduating from the University of Central Florida. Johnathan and Remelisa graduated with a Masters in Aerospace Engineering, Nicholas and Zachary graduated with a Bachelors in Aerospace Engineering, and Khanh graduated with a Bachelors in Mechanical Engineering with a minor in Materials Science. For the Master’s, Remelisa presented her thesis on Piezospectroscopic Sensing Systems – Multi-Scale and In-Situ Sensing Technology for Structural Integrity, and Johnathan presented his thesis on Experimentation and Simulation of Pulsed Eddy Current Thermography of Subsurface Aircraft Corrosive Defects. Zachary presented his thesis on Degradation From CMAS Infiltration in 7YSZ EB-PVD Thermal Barrier Coatings for his Honors in the Major thesis.

Remelisa Esteves M.S. in Aerospace Engineering

Zachary Stein B.S. in Aerospace Engineering

Nicholas Reed B.S. in Aerospace Engineering

Johnathan Hernandez M.S. in Aerospace Engineering

Khanh Vo B..S. in Mechanical Engineering Minor in Material Science

Lab Member Participated at 2020 Southeast Grad Symposium of the Society for Experimental Mechanics

Quentin Fouliard presented at the symposium his work on Thermal Barrier Coating Delamination Monitoring via Luminescence Sensing for the session named “This is Why I’m Hot: Thermal Studies” at the 2020 Southeast Grad Symposium of the Society for Experimental Mechanics (SEM) on June 15th, 2020. Quentin also served as chair for the session on fracture mechanics a.k.a. “Achy Breaky Parts” and as a panelist to provide guidance to graduate students attending the event. The panelists discussed their personal experience through graduate school and tips to lead successful research and to start a career oriented towards engineering and academia. SEM is a professional organization for engineers and scientists in academia, government and industry that focuses on experimental methods for characterization of materials, structures and systems.

New Lab Members Introduction and UCF Research Restart

UCF has opened its doors for the continuation of research amid campus closure due to COVID-19. Following CDC guidelines and new university policies, the Raghavan Research Group are cautiously resuming lab activities that require physical use of the lab.

We are also happy to announce the newest additions to our research team:

Felix Morales (Undergraduate, Aerospace Eng., minor in Material Science Eng. and Mathematics)

Vanessa D’Esposito (Undergraduate, Aerospace Eng., minor in Computer Science and Mathematics)

Rohan Madathil (Undergraduate, mechanical Eng., minor in Computer Science and Mathematics)

Terrence Edwards (Undergraduate, Aerospace Eng.)

Click here to view the newest members of our Team.

SciTech 2021

11-15 January 2021 in Music City Center, Nashville, TN

SciTech is a forum where researchers from around the world come to present their innovations, hear from high-profile experts, and attend courses and workshops to expand their technical knowledge.

https://www.aiaa.org/SciTech

Modeling luminescence behavior for phosphor thermometry applied to doped thermal barrier coating configurations

Read our paper in Applied Optics

Abstract:

Phosphor thermometry is a promising non-destructive method for accurate temperature measurement using phosphor elements that emit temperature-dependent luminescence. The method relies on the intensity and decay of luminescence arising from the phosphor elements upon excitation by an incident laser. In this work, the classical Kubelka–Munk model has been utilized and modified to model the luminescence emitted from phosphor elements that are added into thermal barrier coatings (TBCs) to enable temperature sensing using phosphor thermometry. The collectible luminescence and its time-decay behavior emerging from a tailorable multilayer TBC configuration have been predicted for different rare-earth dopants: Dy, Er, and Sm within an yttria-stabilized zirconia (YSZ) host, and with an operational gradient of temperature acting through its depth. The configurations have been designed by varying the position and thickness of the doped layer into the coating. The decay constant of the collectible luminescence has been used to determine the position in the coating from where the luminescence decay is the same as the decay of the collectible signal. This subsurface position indicates the location at which the temperature measurement is performed using phosphor thermometry under realistic operating conditions. It has been determined that YSZ:Dy provides the highest intensity of the collectible luminescence among the three dopant materials. In the TBC configuration with a fully doped coating, using YSZ:Er as a sensor enables temperature measurement from a more in-depth position in the coating. It has been shown that this position can be tailored by adjusting the geometrical configuration of the TBCs, varying the position and thickness of the doped layer. Due to the sensitivity of the dopants to temperature, the decay behavior of the emerging luminescence is demonstrated to change for different TBC configurations. The model can be used in screening the dopants to design multilayered TBCs for their suitability in temperature sensing by phosphor thermometry.

To view more posts like this, check out the Highlights page here.

You can also hear about Quentin’s paper in the All Audio Posts page here.