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Famu-Fsu College Of Engineering
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Industrial Engineering Manufacturing Engineering
O.I. Okoli, G.F. Smith. Aspects of the Tensile Response of Random Continu
, National Science Foundation
The Florida State University invites companies to join us in commercializing a new method for monitoring the structural health of fiber-reinforced composites (FRCs). The continuous push to create faster and lighter vehicular structures has radically increased the use of fiber-reinforced composite (FRC) materials in the aerospace industry and others because these composites possess high specific strength and stiffness. Economic constraints have also contributed to the growing trend of airlines operating aircraft beyond their design lives, making their effective monitoring for structural damage an important safety feature. Increasingly, too, composite materials are used in the construction of buildings, dams, naval structures, and ground-based vehicles.
Multiscale, multifunctional advanced composite materials have the potential of creating a paradigm shift in how engineered structures are used. Their failure modes which enhance their ability to absorb impact energy are unlike those seen in metallic materials and have no single, similar self-propagating crack features. Metals show visible damage caused by impact mainly on the surface of structures, while damage is hidden inside composite structures especially when subjected to low velocity impact such as bird collisions or tool drops. This barely visible damage may cause serious decrease in material strength of the structure over its life-cycle.
Current inspection and monitoring techniques are based primarily on exterior examinations and/or externally mounted sensors placed at discrete locations. Since failures in composites are frequently microscopic, originate internally, and are slow to reveal themselves externally, current detection systems are limited in their effectiveness.
A cost issue also exists. In the case of airplanes, approximately 27% of their life-cycle cost is spent on inspection and repair. Thus, accurately and quickly identifying the location and severity of damage at the micro-structural levels is essential to detecting macroscopic fatigue and avoiding catastrophic failures. Future sensors for Structural Health Monitoring (SHM) of aerospace structures are envisioned to be an array of inexpensive, spatially distributed, integrated sensors supporting online/real-time acquisition of structural integrity information on the loading, environmental effects, structural characteristics and responses of these structures. The information obtained from the sensors can then be used to monitor the structural integrity of the components in real-time in order to avoid catastrophic failures.
With the recent advances in material research, solutions to damage monitoring will need to be based on an integrated platform. At FSU’s High-Performance Materials Institute, a novel SHM system is in development, which will detect minute structural damage in FRC materials (e.g., fiberglass, carbon fiber). Essentially, this is a biomimetic solution pre-existing in nature that can act as a guide towards ubiquitous sensing by use of Triboluminescent materials. Triboluminescence is a physical phenomenon, where upon duress crystalloid materials emit copious amounts of visible light. By integrating these triboluminescent materials in fiber-reinforced composites alongside a transmission medium, failure information can be obtained.
Dye-sensitized solar cell (DSSC) is a photoelectrochemical (PEC) system based on a semiconductor formation with a photo-sensitized anode, a conductive cathode and an electrolyte. The incorporation of conventional flat cells with FTO substrates may yet prove challenging to the integrity of engineering structures due to their rigid substrates and unavoidable thickness. FSU researchers created hybid flexible wire shaped DSSCs to replace conventional devices with similar functions. These novel structures possess higher flexibility on a smaller scale for novel integration. Moreover, the hybrid sensitizer realize both MEG effects and multiple electron transmission paths, which can improve the cell performance to a large extend.
The 3D PY sensor construction is embedded smart composites with intrinsic triboluminescent/mechanoluminescent (TL/ML) features. Hybrid wire-shaped DSSC was developed as PY sensor using as a tool in TL-based structural health monitoring (SHM) system. The current design allows it to capture, convert, and transport light signal for TL events for the detection of damage and in-situ SHM. It also allows for the harvesting of energy in systems.
Novel Features:
-High flexibility when applying wire-shaped DSSC to replace conventional FTO glass based rigid device.
-CNTs are light weight, and exhibit strong mechanical performance, and significant electrical and chemical properties, all which make it competitive when replacing other metal wires in the research.
-The combination of two efficient quantum dots (QDs) has been first applied into wire-shaped DSSCs and the effects of QDs have been enlarged when acting in concert with porous TiO2.
-All soli- state fabrication method ensures stable mechanical properties and illustrates the simplicity of assembly, which also provides a protection to cell itself.
-The novel small size wire shaped DSSC has been proved to maintain stable under various working environment, which is beneficial for future installment and other engineering applications.
This novel method allows the individual to predictably and repeatably coat semi-conductive wire shaped materials (such as carbon nano-tube yarn (CNY)) with perovskite solution (CH3NH3Pb13). Perovskite is a rising star in the photo-voltaic community. With the research community rushing to bring 2D planar perovskite solar cells to market, coating/manufacturing methods for 3D structures have been left behind. Controllable and uniform heating of the substrate is necessary for a high-quality perovskite layer. Due to the complex 3D geometry of wires, the repeatable control and uniform heating of CNYs has not been possible until this method was created. Here we use Joule Heating to accurately and stably control the temperature of the wire in order achieve a uniform perovskite layer. Not only does this method add control and repeatability to the process, but it is also more energy efficient than any other published method. This makes this process ideal for scalable research applications and eventually industrial fabrication of wire-shaped perovskite LEDs, photo-detectors, and solar cells.
Advantages:
- Uses less energy than other methods, making it a strong candidate for scalable manufacturing as perovskite solar cells continue to rise in efficiency and performance.
- Provides instant heating and cooling to the substrate using Joule heating.
- Allows for the instantaneous control over heating of the substrate by merely adjusting the power source.
Structural health monitoring (SHM) is an essential tool for ensuring safety and integrity while detecting the progression of damage within engineering structures to estimate expected failure.1-4 This is usually done over time through periodically sampled response measurements to monitor changes in material and geometrical properties of a given system. Take a commercial aircraft, for example, that usually travels at around 580 MPH. Any impact at this speed could cause damage to the material. If it goes unnoticed, then it will progress and further risk ultimate failure or the lives of that on-board.5 Because of situations like this, there is a demand for a real-time SHM device within damage-prone systems. A proposed idea to meet the demand is a flexible mechanoluminescent (ML)-organic photodiode. The device consists of a photodiode constructed on top of an ML layer which emits light when it experiences some mechanical action, such as pressure.
Organic photovoltaic (OPV) materials can be used as a photo-absorbing layer for ML light. This OPV layer is made up of a blend of donor polymer, poly (3-hexylthiophene-2,5-diyl (P3HT), and non-fullerene acceptor (BTP-4F or Y6). The broad ultraviolet-visible to near-infrared light absorption and excellent charge transport efficiency make P3HT:Y6 active materials a promising alternative as the light absorbing layer to detect photon emission from the ML layer in flexible organic photodiodes for sensing and SHM. The pressure sensor is a vertical device structure of indium tin oxide (ITO)/tin oxide (SnO2)/P3HT:Y6/silver (Ag) electrode. The current-voltage measurements revealed that the P3HT:Y6 OPVs exhibited an excellent rectification ratio. When this technology is coupled with a software and data acquisition system, sensor’s data can be received and interpreted