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

Enhanced damage imaging of a metallic plate using matching pursuit algorithm with multiple wavepaths

Kim, H. W., & Yuan, F. G. (2018), Ultrasonics, 89, 84-101.

Extraction of guided wave dispersion curve in isotropic and anisotropic materials by Matrix Pencil method

Chang, C. Y., & Yuan, F. G. (2018), Ultrasonics, 89, 143-154.

Air-coupled nondestructive evaluation dissected

Harb, M. S., & Yuan, F. G. (2018), Journal of Nondestructive Evaluation, 37(3).

Impact damage visualization in a honeycomb composite panel through laser inspection using zero-lag cross-correlation imaging condition

Girolamo, D., Chang, H. Y., & Yuan, F. G. (2018), Ultrasonics, 87, 152-165.

A semi-analytical approach for SH guided wave mode conversion from evanescent into propagating

Yan, X., & Yuan, F. G. (2018), Ultrasonics, 84, 430-437.

On vibrations of porous nanotubes

She, G. L., Ren, Y. R., Yuan, F. G., & Xiao, W. S. (2018), International Journal of Engineering Science, 125, 23-35.

Improvement of progressive damage model to predicting crashworthy composite corrugated plate

Ren, Y. R., Jiang, H. Y., Ji, W. Y., Zhang, H. Y., Xiang, J. W., & Yuan, F. G. (2018), Applied Composite Materials, 25(1), 45-66.

Study on random decrement signature under different triggering level and length of time history

Wu, J. Z., Zheng, X. J., Hu, J., Zhang, Y. G., & Yuan, F. G. (2017), In Topics in modal analysis & testing, vol 10. (Conference Proceedings of the Society for Experimental Mechanics Series, ) (pp. 159-166).

On buckling and postbuckling behavior of nanotubes

She, G. L., Yuan, F. G., Ren, Y. R., & Xiao, W. S. (2017), International Journal of Engineering Science, 121, 130-142.

Design of novel plug-type triggers for composite square tubes: Enhancement of energy-absorption capacity and inducing failure mechanisms

Jiang, H. Y., Ren, Y. R., Gao, B. H., Xiang, J. W., & Yuan, F. G. (2017), International Journal of Mechanical Sciences, 131, 113-136.

View all publications via NC State Libraries

Grants

Structural Health Monitoring of Persistent Platforms

National Aeronautics & Space Administration (NASA)(8/01/18 - 7/31/19)

×

Structural Health Monitoring of Persistent Platforms

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 8/01/18

End Date: 7/31/19

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 - 9/30/19)

×

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

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 10/01/17

End Date: 9/30/19

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

NIA Graduate Research Assistantship for Mr. Dongwon Lee

US Air Force - Office of Scientific Research (AFOSR)(8/16/16 - 8/15/18)

×

NIA Graduate Research Assistantship for Mr. Dongwon Lee

Sponsor: US Air Force - Office of Scientific Research (AFOSR)

Start Date: 8/16/16

End Date: 8/15/18

Abstract

Boron nitride nanotubes (BNNT) have been synthesized using a high temperature-pressure (HTP) method, and studied at the National Institute of Aerospace (NIA) BNNT Lab in collaboration with NASA Langley Research Center. 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 is 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 are demonstrated in multiscale to target a game-changing system design and innovation for aerospace and future NASA missions.

Close

Samuel P. Langley Distinguished Professor Program (LaP)-FY16

National Aeronautics & Space Administration (NASA)(10/01/15 - 12/31/17)

×

Samuel P. Langley Distinguished Professor Program (LaP)-FY16

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 10/01/15

End Date: 12/31/17

Abstract

In the last year, an initial promise has been made for imaging the delamination for a honeycomb structure using standing wave concept and a zero-lag cross-correlation imaging condition in the frequency-wavenumber domain. This is very encouraging since the very small barely visible impact damages (BVIDs), one has dimension (11mm×12mm), the other (5 mm×6 mm) can be accurately imaged using this novel concept. However the system developed including pulse laser, galvomirrors, and LDV was demonstrated on an optical table (5 ft×7 ft) shown in the figure. 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 small smaller flaws for instance from automated manufacturing. The objective of the proposal is 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.

Close

An Advanced Ultrasonic Imaging System for Rapid Inspection of Ultra Large Complex Composite Structures using Time Reversal-MUSIC Technique

National Aeronautics & Space Administration (NASA)(7/07/15 - 12/07/15)

×

An Advanced Ultrasonic Imaging System for Rapid Inspection of Ultra Large Complex Composite Structures using Time Reversal-MUSIC Technique

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 7/07/15

End Date: 12/07/15

Abstract

The proposal is to develop an innovative automated ultrasonic imaging technique system, which is called AUIT system, for rapid inspection of large-area complex composites. The key innovation of the proposed approach lies in the combination of time-reversal multiple signal classification (TR-MUSIC) imaging algorithm and the guided-wave based portable linear-array technology for rapid inspection of ultra large complex composite structures. In the proposed approach, a guided-wave based automated ultrasonic imaging technique system, operating in a pulse-echo mode, is used to activate/receive guided waves. The detected ultrasonic signals from scattered waves are then processed by the TR-MUSIC algorithms to achieve super-resolution images in real-time for ultra large plate-like structures. Not only the group velocity (cg) but also the amplitude and phase information are preserved to evaluate the severity of the damage. The complex composite structures could be characterized experimentally such that no material properties are required for the whole inspection process, which is called non-parametric interrogation. Since the time-domain signals are converted to frequency-domain signals for data processing, the dispersion effect, which is a major challenge in guided wave damage detection, is compensated automatically. In common imaging systems, the resolution is no better than half of the wavelength, λ/2, which is the diffraction limit. Since MUSIC algorithm uses the noise space other the signal space, super resolution could be achieved using the TR-MUSIC imaging algorithms. Due to its super resolution imaging ability, larger wavelengths can be utilized by the AUIT system to achieve equally good damage imaging resolution compared with other imaging algorithms such as phased array (PA) and synthetic aperture focusing technique (SAFT). Thus, relative low frequencies can be used with the AUIT system leading to significant advantages. One advantage is that the hardware is allowed to be with lower sampling rate and smaller data volume storage. Also the application of lower frequency guided waves allows ultra large inspection areas compared with using higher frequency signals, since in plate-like structures, especially for composite materials, the attenuation effect increases significantly with the increase of the input frequency. The lower frequency range of low-order Lamb waves sometimes with higher sensitivity to various kinds of damage. The AUIT system can be easily integrated with robotic arm techniques to create a fully automatic scanning system. Embedded with the TR-MUSIC algorithms, the AUIT system delivers real-time, non-parametric, super resolution damage imaging for ultra large complex composite structures, with the advanced data processing and imaging capabilities. The required complexity of operations and the inspection time will be reduced significantly using the AUIT system.

Close

In-Processing Cure Monitoring of Composites

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

×

In-Processing Cure Monitoring of Composites

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 8/15/15

End Date: 8/14/17

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

Automated Data Analysis for the CLANDE System (NIA GRA for Donato Girolamo)

National Aeronautics & Space Administration (NASA)(3/01/15 - 2/28/17)

×

Automated Data Analysis for the CLANDE System (NIA GRA for Donato Girolamo)

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 3/01/15

End Date: 2/28/17

Abstract

The purpose of the project is to develop an automated data analysis system that processes the acquired three-dimensional matrix and returns in output a quantitative damage image. The data analysis system will consists of four parts: 1) wavefield construction 2) data filtering 3) damage imaging 4) flaw map damage data in an industry standard format such as STL compatible with FEM codes for structural analysis and flaw disposition procedures The first part consists in assembling the point-data acquired by the LDV in order to obtain the wavefield in the domain of interest; in the second part filters are applied in the frequency-time domain to reduce the noise and in the frequency-wavenumber domain to separate the incident field from the backscattered field; in the last and final part the filtered wavefield is further process to imagine and quantify the damage. This process is done through cross-correlation imaging condition in the frequency domain. An algorithm will be developed to automatically select the damage resonance frequencies and associate them with damage geometrical properties. The fourth part would be to develop and demonstrate a methodology to properly transfer flaw size and location information into industry standard (such as STL format, or some other widely accepted nonproprietary file format) for input into FEM software tools.

Close

Automated Monitoring of Composite Structures (NIA GRA for Rey-Yie Fong)

National Aeronautics & Space Administration (NASA)(1/01/15 - 8/15/16)

×

Automated Monitoring of Composite Structures (NIA GRA for Rey-Yie Fong)

Sponsor: National Aeronautics & Space Administration (NASA)

Start Date: 1/01/15

End Date: 8/15/16

Abstract

A variety of manufacturing techniques have been developed for polymer matrix composites (PMCs). Specifically for toughened-epoxy thermoset matrix composites, the processing parameters have been mainly determined in ah-hoc trial and error manner. Recent efforts to develop embedded sensors in the structures for monitoring purposes have resulted in methodologies to identify flaws and damage in PMC composites. Advances in new sensing materials and more sensitive sensors can even quantify very small defects down to sub-mini-meter range. The work for using air-coupled transducers mounted on the AFP is proposed for automated monitoring of possible manufacture-induced defects through many operational parameters. The air-coupled transducers will be mounted on the base plate while the composite is being cured.

Close