Education

Research Description

Dr. Yuan is interested in structural health monitoring, damage tolerance of composite structures, smart materials and structures, and fracture and life prediction of advanced materials and structures. Dr. Yuan is currently developing methods for structural diagnosis and prognosis (involves evaluating remaining life of structures using failure/statistical analysis tools), is developing a wireless sensor that monitors structural integrity, is developing methods for in-situ, mount-ed/embedded sensors for multi-functional composite structures, and is studying bio-inspired morphing technologies for civil, mechanical, and aerospace structures. Within MAE, Dr. Yuan collaborates with Dr. Peters and Dr. Wu.

Publications

Adaptive signal decomposition and dispersion removal based on the matching pursuit algorithm using dispersion-based dictionary for enhancing damage imaging

Kim, H., & Yuan, F.-G. (2020), ULTRASONICS, 103. https://doi.org/10.1016/j.ultras.2020.106087

Impact diagnosis in stiffened structural panels using a deep learning approach

Zargar, S. A., & Yuan, F.-G. (2020), STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL. https://doi.org/10.1177/1475921720925044

3D printing of electroactive PVDF thin films with high beta-phase content

Chen, C., Cai, F., Zhu, Y., Liao, L., Qian, J., Yuan, F.-G., & Zhang, N. (2019), SMART MATERIALS AND STRUCTURES, 28(6). https://doi.org/10.1088/1361-665X/ab15b7

Damage Detection and Localization using Random Decrement Technique on Metallic Plates

Chang, Y. S., & Yuan, F.-G. (2019), SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2019. https://doi.org/10.1117/12.2519313

Energy-absorption performance of composite corrugated plates with corrugated-shape ditch plug initiator

Liu, Z., Jiang, H., Ren, Y., Qian, Z., & Yuan, F.-G. (2019), POLYMER COMPOSITES, 40(5), 1708–1717. https://doi.org/10.1002/pc.24924

Guided wave-based system for real-time cure monitoring of composites using piezoelectric discs and phase-shifted fiber Bragg gratings

Hudson, T. B., Auwaijan, N., & Yuan, F.-G. (2019), JOURNAL OF COMPOSITE MATERIALS, 53(7), 969–979. https://doi.org/10.1177/0021998318793512

Hygro-thermal wave propagation in functionally graded double-layered nanotubes systems

She, G.-L., Ren, Y.-R., & Yuan, F.-G. (2019), STEEL AND COMPOSITE STRUCTURES, 31(6), 641–653. https://doi.org/10.12989/scs.2019.31.6.641

On nonlinear bending behavior of FG porous curved nanotubes

She, G.-L., Yuan, F.-G., Karami, B., Ren, Y.-R., & Xiao, W.-S. (2019), INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE, 135, 58–74. https://doi.org/10.1016/j.ijengsci.2018.11.005

Piezoelectric Characterization of Boron Nitride Nanotube-Polyurethane Composites

Lee, D., Yuan, F.-G., Fay, C., Chu, S.-H., & Park, C. (2019), MICRO- AND NANOTECHNOLOGY SENSORS, SYSTEMS, AND APPLICATIONS XI. https://doi.org/10.1117/12.2513999

Research on the Actuation Performance of 2D-Orthotropic Piezoelectric Composite Materials Linear Phased Array Transducer

Wang, Z., Li, X., Yuan, F.-G., & Bao, Z. (2019), JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 19(8), 5205–5210. https://doi.org/10.1166/jnn.2019.16814

View all publications via NC State Libraries

Grants

Samuel P. Langley Distinguished Professor Program – FY21

National Aeronautics & Space Administration (NASA)(10/01/20 - 9/30/21)

×

Samuel P. Langley Distinguished Professor Program – FY21

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 10/01/20

End Date: 9/30/21

Abstract

In order to apply technologies to the field applications for inspecting the aerospace composite structures efficiently, the optical-based laser systems should be portable and noise-insensitive. Additionally, the software will be further developed to image smaller flaws (or damages) for instance from automated manufacturing process and/or operation. The objective of the proposal is to continue to develop a rapid laser ultrasonic composite inspection system for quantifying the damage. The proposal is to develop, demonstrate, and mature two innovation technologies in field applications including new hardware and software tools to be encompassed in the system. The two new innovations will overcome current major bottlenecks for rapid large area detection and characterization of either manufacturing or in-service damage in composite structures in terms of sensitivity, resolution, and accuracy. The robust system will also identify and classify the flaw types including porosity and delamination. The resolution limit of each flaw type and quality of the flaw characterization will be determined. The system with much rapid signal and imaging processing tool with high component throughput can be an order of magnitude faster than those of current either contact or non-contact NDI system. The proposal will also develop a practical inspection for data acquisition and analysis methods for processing data that enable in the field to increase automation and reduce the subjective nature of many aspects of the current inspection methodology. The system will enable operating in the field instead of being confined to the vibration-free and isolated laboratory testing. The laser generation and reception generated or received from a fiber optical cable will allow greater flexibility in interrogating hard-to-access areas. In the last year, all the Ne-He laser system and parts have been acquired and they are being assembled for testing in the controlled environments. A computer vision-based SHM system using a high-speed camera has shown initial promise of imaging the sizable damage using 14 KHz piezo excitation. The project is on-going to optimize and fine tune the system by using a piezoshaker for excitation. Several imaging algorithms used in vision-based SHM system are being proposed to image the damage. The image will compare with those by LDV-based system.

Close

Visualization of Hidden Damage in Composites from Full-Field Vibration Measurement Using a Stereo High-Speed Camera System

NCSU NC Space Grant Consortium(6/15/20 - 5/31/21)

×

Visualization of Hidden Damage in Composites from Full-Field Vibration Measurement Using a Stereo High-Speed Camera System

Sponsor: NCSU NC Space Grant Consortium

Start Date: 6/15/20

End Date: 5/31/21

Abstract

Recently, composite structures have seen greatly increased use in aerospace applications as part of both aircraft and spacecraft. The use of composites can significantly reduce vehicle weight and manufacturing time. One large setback of composites, however, is that damage inspection is difficult. Unlike other materials such as aluminum, damage to composites is typically subsurface and cannot be seen by the naked eye. This poses an issue with inspection, as more complicated and time-consuming methods are needed to ensure the safety of a component. If the time required for these inspection methods can be reduced, or even if the structure can be inspected in-situ, the structure could be inspected more frequently to reduce the amount of time damage has to propagate before detection, or inspection of the structure may require less downtime, reducing opportunity costs (for example in commercial aircraft). Ultrasonic guided-wave based techniques have shown great potential for practical applications in nondestructive inspection (NDI) and structural health monitoring (SHM) for reducing the risks of catastrophic failures in critical structures like aircraft [1-5]. By investigating the scattered ultrasonic guided waves in a structure using appropriate signal/image processing algorithms, a wealth of information about the hidden details of the structure can be unearthed, including information about the location and characteristics of any damage present. Proper algorithms can then be implemented to create a “map” of the structure, highlighting any damage that is present. This means that not only the presence of damage is known, but also its size and location. If this technology can be implemented on critical structural components of aircraft and spacecraft, damage could be detected near-real-time so that proper steps can be taken quickly to ensure safety.

Close

Multifunctional Boron Nitride Nanotube (BNNT) Materials and Applications for Structural Health Monitoring

National Aeronautics & Space Administration (NASA)(6/01/20 - 12/31/20)

×

Multifunctional Boron Nitride Nanotube (BNNT) Materials and Applications for Structural Health Monitoring

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 6/01/20

End Date: 12/31/20

Abstract

The overall objective of this research is to study the structure and the material properties of BNNTs and their nanocomposite materials for extreme environment applications and technologies. The BNNT growth will be optimized for high quality and high yield production using in-situ monitoring system. The BNNTs and their nanocomposites are fabricated in multiscale to demonstrate their material properties. Ex-situ material characterization is systematically conducted to confirm the structure and the material properties (thermal, mechanical, electrical, and radiation) of BNNTs and their nanocomposites including PVDF/BNNTs. In the case of the nanocomposites, various matrices are investigated according to BNNT’s affinity and thermal stability, including high performance polymers and metals. Multifunctional BNNT materials and applications will be demonstrated in multi-scale to target a game-changing system design and innovation for aerospace and future NASA missions. Especially the piezoelectric sensing properties through a couple of stretching techniques and 3-D printing fabrication method to induce electric polarization of BNNTs in matrix materials for enhancing the sensing performance will be studied.

Close

Multifunctional Boron Nitride Nanotube (BNNT) Materials and Applications (Dongwon Lee)

Rice University (William Marsh Rice University)(7/01/19 - 12/31/20)

×

Multifunctional Boron Nitride Nanotube (BNNT) Materials and Applications (Dongwon Lee)

Sponsor: Rice University (William Marsh Rice University)

Start Date: 7/01/19

End Date: 12/31/20

Abstract

Boron nitride nanotubes (BNNT) have been synthesized using a high temperature-pressure (HTP) method. Without a catalyst, the HTP process produces high-quality BNNTs that have small diameters (~ 5 nm), high aspect ratios (≥ 1:1000), high flexibility, high crystallinity, and piezoelectricity. Their promising material properties include high Young’s modulus (up to 1.3 TPa), excellent thermal stability (up to 900 oC in air), high thermal conductivity (300–3000 W/mK), excellent electrical insulation (with a wide band of ~ 6.0 eV), and high neutron absorption (10B ~3800 barn). With such unique material properties, BNNT materials can open up opportunities for multifunctional applications in extreme environments. The main objective of this research is to study the structure and the material properties of BNNTs and their nanocomposite materials for extreme environment applications and technologies. The BNNT growth will be optimized for high quality and high yield production using in-situ monitoring system. The BNNTs and their nanocomposites are fabricated in multiscale to demonstrate their material properties. Ex-situ material characterization is systematically conducted to confirm the structure and the material properties (thermal, mechanical, electrical, and radiation) of BNNTs and their nanocomposites including PVDF/BNNTs. In the case of the nanocomposites, various matrices are investigated according to BNNT’s affinity and thermal stability, including high performance polymers and metals. Multifunctional BNNT materials and applications will be demonstrated in multi-scale to target a game-changing system design and innovation for aerospace and future NASA missions. Especially the piezoelectric sensing properties through a couple of stretching techniques to induce -phase for enhancing the sensing performance will be studied.

Close

NIA Graduate Research Assistantship for Mr. Dongwon Lee - Investigating the Structural and Mechanical Properties of Boron Nitride Nanotubes and their Polymer Nanocomposites

Korea Institute of Science and Technology (KIST)(8/16/18 - 7/31/19)

×

NIA Graduate Research Assistantship for Mr. Dongwon Lee - Investigating the Structural and Mechanical Properties of Boron Nitride Nanotubes and their Polymer Nanocomposites

Sponsor: Korea Institute of Science and Technology (KIST)

Start Date: 8/16/18

End Date: 7/31/19

Abstract

Boron nitride nanotubes (BNNT) have been synthesized using a high temperature-pressure (HTP) method. Without a catalyst, the HTP process produces high-quality BNNTs that have small diameters (~ 5 nm), high aspect ratios (≥ 1:1000), high flexibility, high crystallinity, and piezoelectricity. Their promising material properties include high Young’s modulus (up to 1.3 TPa), excellent thermal stability (up to 900 oC in air), high thermal conductivity (300–3000 W/mK), excellent electrical insulation (with a wide band of ~ 6.0 eV), and high neutron absorption (10B ~3800 barn). With such unique material properties, BNNT materials can open up opportunities for multifunctional applications in extreme environments. The main objective of this research is to study the structure and the material properties of BNNTs and their nanocomposite materials for extreme environment applications and technologies. The BNNT growth will be optimized for high quality and high yield production using in-situ monitoring system. The BNNTs and their nanocomposites are fabricated in multiscale to demonstrate their material properties. Ex-situ material characterization is systematically conducted to confirm the structure and the material properties (thermal, mechanical, electrical, and radiation) of BNNTs and their nanocomposites. In the case of the nanocomposites, various matrices are investigated according to BNNT’s affinity and thermal stability, including high performance polymers and metals. Multifunctional BNNT materials and applications including sensor applications will be demonstrated in multi-scale to target a game-changing system design and innovation for aerospace and future NASA missions.

Close

Augmented Analysis and Data Collection for Materials Design and Evaluation

National Aeronautics & Space Administration (NASA)(10/01/18 - 9/30/20)

×

Augmented Analysis and Data Collection for Materials Design and Evaluation

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 10/01/18

End Date: 9/30/20

Abstract

Additive manufacturing (AM), also referred to as 3-D printing has been developing steadily since the 1980s. According to some reports, 3-D printing is expected to be a $5.2 billion industry by 2020. AM allows for the manufacture of highly complex geometries which are difficult to handle using traditional manufacturing techniques. However, AM still has several hurdles that it needs to overcome before its widespread adoption, especially in the manufacture of safety critical components e.g., current aerospace practice requires 100% visual inspection of the manufactured component. Often times, manual inspection of the component is much more time consuming than the lay-up process itself. Most of the conventional additive manufacturing systems fail to notice minor defects during material lay-up that may get compounded layer by layer thereby rendering the final product unsuitable for use. These defects could potentially be automatically corrected if detected before the next layer is deployed. The goal of this work is to process the data collected using high-resolution cameras and then to use computer vision technology to detect defects such as porosity, cracks, warping, delamination etc. during the lay-up process itself thereby reducing or eliminating the need for post manufacture inspection of printed objects. This could also facilitate the AM system to take corrective measures during the lay-up process itself thereby achieving a Real-time control of the manufacturing process.

Close

Structural Health Monitoring of Persistent Platforms

National Aeronautics & Space Administration (NASA)(8/01/18 - 12/31/20)

×

Structural Health Monitoring of Persistent Platforms

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 8/01/18

End Date: 12/31/20

Abstract

The Structural Mechanics and Concepts Branch at NASA Langley Research Center is currently developing a concept for in-space assembly of persistent assets consisting of repeating truss modules. In-space assembly has been recognized as a critically important approach for reducing the cost of major lunar and deep space missions. Multiple smaller payloads can be launched by a variety of vehicles, then assembled in orbit, by robotic/autonomous means. One of the objectives of the research is to develop a method of monitoring structural health through integrated sensors while also minimizing parasitic mass, power consumption, wiring complexity, costs, and volume occupied by the sensor systems. To achieve this goal, Rounak will research methods of determining global health states of the platform and specifying local module detriments such as stress fractures or MMOD impacts. One of the most promising methods is a short pulse based vibration feedback model to determine structural health across the fully assembled structure. By inputting the short pulse with known waveform and magnitude, integrated piezoelectric sensors can sense and analyze the resultant vibrations through their respective portions of the platform to characterize any damage in the struts and/or nodes. Another alternative of using vision-based monitoring techniques will be possibly considered. The usage monitoring using accelerometers for example will be explored. By maximizing the section of the assetthat is being monitored by each sensor system, the number of integrated sensors can be minimized.

Close

Samuel P. Langley Distinguished Professor Program (LaP) – FY18

National Aeronautics & Space Administration (NASA)(10/01/17 - 12/31/20)

×

Samuel P. Langley Distinguished Professor Program (LaP) – FY18

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 10/01/17

End Date: 12/31/20

Abstract

In order to apply this technology to the field applications for inspecting the entire aerospace structures, the laser systems should be portable and noise-insensitive. Additionally, the software will be further developed to image smaller flaws for instance from automated manufacturing. The objective of the proposal is to continue to develop a rapid laser ultrasonic composite inspection system for quantifying the damage. The proposal will develop, demonstrate, and mature two innovation technologies in field applications including new hardware and software tools to be encompassed in the system. The two new innovations will overcome current major obstacles for rapid large area detection and characterization of either manufacturing or in-service damage in composite structures in terms of sensitivity, resolution, and accuracy. The robust system will also identify and classify the flaw types including porosity and delamination. The resolution limit of each flaw type and quality of the flaw characterization will be determined. The system with much rapid signal and imaging processing tool with high component throughput can be an order of magnitude faster than those of current ether contact or non-contact NDI system. The proposal will develop a practical inspection for data acquisition and analysis methods for processing data that enable in the field to increase automation and reduce the subjective nature of many aspects of the current inspection methodology. The system will enable operating in the field instead of being confined to the vibration-free and isolated laboratory testing. The laser generation and reception generated or received from a fiber optical cable will allow greater flexibility in interrogating hard-to-access areas. A computer vision-based SHM system is starting in parallel with the LDV-based system. Several imaging algorithms used in vision-based SHM system are being proposed to image the damage. The image will compare with those by LDV-based system.

Close

Real-time Cure Monitoring of Composites Using Piezoelectric Wafers and Fiber Bragg Gratings/Phase-Shifted Fiber Bragg Gratings

National Aeronautics & Space Administration (NASA)(8/15/17 - 8/14/18)

×

Real-time Cure Monitoring of Composites Using Piezoelectric Wafers and Fiber Bragg Gratings/Phase-Shifted Fiber Bragg Gratings

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 8/15/17

End Date: 8/14/18

Abstract

The NASA Advanced Composites Project seeks to develop and transition technology that will reduce the timeline required for development and certification of new aircraft structure that utilizes advanced composite materials. One area of concern is the formation of porosity and fiber waviness defects in composite structural parts during various processing stages, from incoming material handling to the completion of laminate curing in an autoclave/vacuum press. To address this concern, an attempt is being made to develop an in-line, cure monitoring detection technique that can support a physics-based cure model to predict the formation of porosity and fiber waviness. It is not an essential requirement to transition this technology to industry in a mass production environment. Initial results indicate that the group velocity of a guided wave may have the potential to serve as an index for estimating the degree of cure and level of porosity. The work will be to transition to an in-line detection system that will be able to monitor the degree of cure and porosity in real-time within a part based on group velocity. The in-line defect detection system will utilize high temperature piezoelectric actuators and sensors for pitch-catch guided wave emission and response detection as well as investigate other metrics such as attenuation of wave energy which will play a critical role during the early stages of cure. A bulk wave pulse-echo technique will be investigated in addition to a guided wave technique to utilize a higher frequency spectrum (>1 MHz) and gain additional information about the part. Both methods can be operated on a single setup. This method is similar to a C-scan except for the fact that the location of the piezoelectric ultrasonic transducer is fixed and is not able to translate in the X-Y plane. A few studies have been published showing that as the porosity level increases, the ultrasonic velocity of the bulk wave propagating perpendicular to the carbon fibers decreases. Experimental studies have been and will continue to be conducted to measure strains during and after cure in CFRP panels. Fiber Bragg grating sensors (FBGs) were embedded between adjacent plies of prepreg and the wavelength shift was measured throughout the cure cycle. A change in wavelength response from the FBGs is caused by strain and change in temperature at the embedded sensor’s location. In parallel with experimental studies, analytical studies are being conducted on the cure process modeling of CFRP panels using COMPRO®, RAVEN®, and ABAQUS®. The residual strain measurements from laboratory tests will be correlated with the analytical model predictions.

Close

In-Processing Cure Monitoring of Composites

National Aeronautics & Space Administration (NASA)(8/18/16 - 10/14/17)

×

In-Processing Cure Monitoring of Composites

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 8/18/16

End Date: 10/14/17

Abstract

The NASA Advanced Composites Project seeks to develop and transition technology that will reduce the timeline required for development and certification of new aircraft structure that utilizes advanced composite materials. One area of concern is the formation of porosity and fiber waviness defects in composite structural parts during various processing stages, from incoming material handling to the completion of laminate curing in an autoclave/vacuum press. To address this concern, an attempt is being made to develop an in-line, cure monitoring detection technique that can support a physics-based cure model to predict the formation of porosity and fiber waviness. It is not an essential requirement to transition this technology to industry in a mass production environment. Initial results indicate that the group velocity of a guided wave may have the potential to serve as an index for estimating the degree of cure and level of porosity. The work will be to transition to an in-line detection system that will be able to monitor the degree of cure and porosity in real-time within a part based on group velocity. The in-line defect detection system will utilize high temperature piezoelectric actuators and sensors for pitch-catch guided wave emission and response detection as well as investigate other metrics such as attenuation of wave energy which will play a critical role during the early stages of cure. A bulk wave pulse-echo technique will be investigated in addition to a guided wave technique to utilize a higher frequency spectrum (>1 MHz) and gain additional information about the part. Both methods can be operated on a single setup. This method is similar to a C-scan except for the fact that the location of the piezoelectric ultrasonic transducer is fixed and is not able to translate in the X-Y plane. A few studies have been published showing that as the porosity level increases, the ultrasonic velocity of the bulk wave propagating perpendicular to the carbon fibers decreases. Experimental studies have been and will continue to be conducted to measure strains during and after cure in CFRP panels. Fiber Bragg grating sensors (FBGs) were embedded between adjacent plies of prepreg and the wavelength shift was measured throughout the cure cycle. A change in wavelength response from the FBGs is caused by strain and change in temperature at the embedded sensor’s location. In parallel with experimental studies, analytical studies are being conducted on the cure process modeling of CFRP panels using COMPRO®, RAVEN®, and ABAQUS®. The residual strain measurements from laboratory tests will be correlated with the analytical model predictions.

Close