Sean Webb

UES (United States)

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Kara Peters

North Carolina State University

Stephen M. Schultz

Brigham Young University

Richard H. Selfridge

KTH Royal Institute of Technology

M.A. Zikry

North Carolina State University

Spencer Chadderdon

Brigham Young University

P. Shin

North Carolina State University

Nikola Stan

Brigham Young University

T. Vella

Brigham Young University

Monica Wolfe

United States Air Force Research Laboratory

Jorge L. Chávez

United States Air Force Research Laboratory

Cooperative Institutions

North Carolina State University

Brigham Young University

United States Air Force Research Laboratory

Wright-Patterson Air Force Base

Development Agency of Serbia

UES (United States)

University of Michigan–Ann Arbor

University of Virginia

Kangwon National University

North Central State College

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Nondestructive inspection of CFRP adhesively bonded joints using embedded FBG sensors

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2013)

Sean Webb P. Shin Kara Peters Richard H. Selfridge Stephen M. Schultz

One challenging need for inspection capabilities is in adhesively bonded joints between composite components, a common location of premature failure in aerospace structures. In this work we demonstrate that dynamic, full spectral scanning of FBG sensors embedded in the adhesive bond can identify changes in bond quality through the measurement of non-linear dynamics of the joint. Eighteen lap joint specimens were fabricated with varying manufacturing quality. Ten samples also included fiber Bragg grating (FBG) sensors embedded in the adhesive bond for real-time inspection during a simulated flight condition of these single-lap joints. Prior to testing, pulse phase thermography imaging of the pristine specimens revealed defects such as air bubbles, adhesive thickness variations, and weak bonding surface between the laminate and adhesive. The lap joint specimens were then subjected to fatigue loading, with regular interrogation of the FBG sensors at selected load cycle intervals. The FBG data was collected during vibration loading of the lap joint to represent an in-flight environment. Changes in the lap joint dynamic response, including the transition to non-linear responses, were measured from both the full-spectral and peak wavelength FBG data. These changes were correlated to initial manufacturing defects and the progression of fatigue-induced damage independently measured with pulse phase imaging and visual inspections of the failure surfaces.

Lap joint

Fiber Bragg Grating

Thermography

Adhesive Bonding

Structural Health Monitoring

10.1117/12.2018443

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Citations (3)

Redox cycling-based signal amplification at alkanethiol modified nanoporous gold interdigitated microelectrodes

Analytica Chimica Acta (2024)

Yi Liu Ajith Mohan Arjun Sean Webb Monica Wolfe Jorge L. Chávez

Interdigitated electrodes (IDEs) enable electrochemical signal enhancement through repeated reduction and oxidation of the analyte molecule. Porosity on these electrodes is often used to lower the impedance background. However, their high capacitive current and signal interferences with oxygen reduction limit electrochemical detection ability. We present utilization of alkanethiol modification on nanoporous gold (NPG) electrodes to lower their background capacitance and chemically passivate them from interferences due to oxygen reduction, while maintaining their fast electron transfer rates, as validated by lower separation between anodic and cathodic peaks (ΔE) and lower charge transfer resistance (Rct) values in comparison to planar gold electrodes. Redox amplification based on this modification enables sensitive detection of various small molecules, including pyocyanin, p-aminophenol and selective detection of dopamine in the presence of ascorbic acid. Alkane thiol NPG arrays are applied as a multiplexed sensor testbed within a well plate to screen binding of various peptide receptors to the SARS COV2 S-protein by using a sandwich assay for conversion of PAPP (4-aminophenyl phosphate) to PAP (p-aminophenol), by the action of AP (alkaline phosphatase), which is validated against optical ELISA screens of the peptides. Such arrays are especially of interest in small volume analytical settings with complex samples, wherein optical methods are unsuitable.

Nanoporous

10.1016/j.aca.2024.342818

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Citations (0)

High-speed full-spectrum interrogation of fiber Bragg grating sensor application in reducing sensor strain sensitivity

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2012)

Nikola Stan Spencer Chadderdon Richard H. Selfridge Stephen M. Schultz Sean Webb

We used high-speed full-spectrum interrogation of a Fiber Bragg Grating (FBG) sensor to measure dynamic strain in different sensor packages in real-time. In this effort we performed solenoid impact tests on a variety of sensor mounting structures made with FR4, steel, and carbon fiber composite materials. Full spectrum FBG interrogation at 40 kHz repetition rate was the key that allowed us to measure and compare dynamic strain in the structures, with measurement resolution on the sub-millisecond scale. With this interrogation method we were able to measure the full character of the dynamic strain including the strain non-uniformity and distribution manifested in peak-splitting and spectrum broadening. Results showed that the FR4 board with soft epoxy responded with a maximum dynamic strain on the order of 3000 micro-strain. Adding hard materials such as steel and graphite fiber composite reduced the strain about 7 times. However, the FR4 board mounted in a free-floating configuration using hard epoxy reduced the maximum strain to a value below the noise threshold of the full spectrum interrogation configuration. Here we proposed using edge detection method of FBG interrogation due to its increased strain sensitivity which enabled us to further analyze the critical results obtained by full spectrum interrogation. We also proposed using edge detection to measure sensor strain in real time for the purpose of filtering out the strain noise from useful signal. We will use the results and data obtained with both methods to analyze and enhance the performance of our electric field sensors in environments of high static and dynamic strain.

Fiber Bragg Grating

10.1117/12.914751

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Citations (0)

Analysis of Fiber Bragg Grating Spectral Features for In-Situ Assessment of Sandwich Composites

Drew Hackney Sean Webb Kara Peters

In this paper we summarize recent advances derived from full-spectral interrogation of FBG sensors for structural health monitoring and damage identification in composites. Previous work has correlated signals from FBG reflected spectra to stress concentrations near crack tips, curing conditions during processing of composite laminates and the progression of delamination due to multiple low-velocity impacts in woven composite laminates. In this paper we investigate the information gained from FBG sensors embedded at the facesheet-core interface in foam-core sandwich composites subjected to low-velocity impact loading. We also discuss recent advances in interrogation systems for these sensors which will permit dynamic evaluation of these parameters. These results demonstrate the richness of information that can be obtained from full-spectral interrogation of FBG sensors in a complex, multiple stress component environment.

Fiber Bragg Grating

Delamination

Interrogation

10.1115/smasis2010-3886

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Citations (2)

High dynamic range high sensitivity FBG interrogation

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2013)

Nikola Stan Douglas Bailey Spencer Chadderdon Richard H. Selfridge Stephen M. Schultz

We present a fiber Bragg grating (FBG) interrogation method using a micro-controller board and optical filter that achieves high strain sensitivity and high dynamic range. This interrogation method allows high sensitivity detection of ultrasonic waves superimposed on low-frequency (on the order of 100Hz) vibrations of arbitrary magnitude. One possible application is in-situ structural health monitoring of windmill blades exposed to strong winds by using FBG sensors for detection of ultrasonic waves. Interrogator operation is based on the edge filtering method using a broadband source, fiber Fabry-Perot filter and a micro-controller board which acts as a control feedback loop that locks the filter wavelength to the mid-reflection point on the FBG spectrum. Wavelength locking method allows high sensitivity for edge filtering of high-frequency waves, while the feedback signal is the measurement of low-frequency vibration with high dynamic range. The concept of the interrogator operation and different implementations are described and discussed with experimental results.

Fiber Bragg Grating

SIGNAL (programming language)

10.1117/12.2009875

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Citations (1)

Fusion of Global and Local Measurements of Damage in Bonded Joints

Conference proceedings of the Society for Experimental Mechanics (2013)

Sean Webb P. Shin Kara Peters

Fiber Bragg Grating

Harmonic

Lap joint

Structural Health Monitoring

10.1007/978-3-319-00765-6_3

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Citations (0)

Novel Oxidants and Sources of Nitrogen for Atomic Layer Deposition

ECS Transactions (2016)

Daniel Alvarez Jeffrey Spiegelman Ed Heinlein Russell J. Holmes Chris Ramos

Significant effort has gone into developing novel metal precursors for Atomic Layer Deposition. This effort has been primarily driven by the industry need for new high K materials and low temperature deposition for metal nitride films. The need for novel oxidants and sources of nitrogen has been largely ignored. This paper focuses on delivery of anhydrous hydrogen peroxide and anhydrous hydrazine for ALD applications.

Anhydrous

Hydrazine (antidepressant)

Deposition

10.1149/07204.0243ecst

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Citations (2)

Fiber Bragg grating spectral features for structural health monitoring of composite structures

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2014)

Sean Webb Kara Peters M.A. Zikry Nikola Stan Spencer Chadderdon

We demonstrate the measurement of and applications for reflected spectral signatures obtained from FBG sen- sors in dynamic environments. Three uses of the spectral distortion measurements for monitoring of airframe structures are presented: the measurement of the dynamic response of a laminated plate to an impact event; the measurement of damage induced spectral distortion in a thin plate during vibration loading; and the measurement of the change in dynamic response of an adhesively bonded joint with the progression of fatigue damage.

Fiber Bragg Grating

Airframe

Structural Health Monitoring

Distortion (music)

10.1117/12.2059625

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Citations (4)

High-speed full-spectrum interrogation of fiber Bragg gratings for composite impact sensing

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2010)

Spencer Chadderdon T. Vella Richard H. Selfridge Stephen M. Schultz Sean Webb

This paper presents a means for the high repetition rate interrogation of fiber Bragg gratings (FBG's). The new system highlights a method that allows a tradeoff between the full spectrum capture rate and the wavelength range and/or the spectral resolution of the technique. Rapid capture of the entire reflection spectrum at high interrogation rates shows important features that are missed when using methods that merely track changes in the peak location of the spectrum. The essential feature of the new system is that it incorporates a MEMs tunable filter driven by a variable frequency openloop sinusoidal source. The paper demonstrates the new system on a laminated composite system under impact loading.

Fiber Bragg Grating

Interrogation

10.1117/12.847662

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Citations (2)

Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE (2013)

Sean Webb P. Shin Kara Peters M.A. Zikry Spencer Chadderdon

In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor embedded at the adhesive layer of a single composite lap joint subjected to harmonic excitation after fatigue loading. After a fully-reversed cyclic fatigue loading is applied to the composite lap joint, the full spectral response of the sensor is interrogated in reflection at 100 kHz during two states: with and without an added harmonic excitation. The dynamic response of the FBG sensor indicates strong nonlinearities as damage progresses. The short-time Fourier transform (STFT) is computed for the extracted peak wavelength information to reveal time-dependent frequencies and amplitudes of the dynamic FBG sensor response. Pulse-phase thermography indicates a progression in defect size at the adhesive layer that strongly suggests non-uniform loading of the FBG sensor.

Fiber Bragg Grating

Lap joint

Harmonic

10.1117/12.2010018

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Citations (2)