{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T04:58:24Z","timestamp":1790830704539,"version":"4.1.0"},"reference-count":56,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T00:00:00Z","timestamp":1790640000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"NASA Langley Research Center","award":["NNL15AA16C"],"award-info":[{"award-number":["NNL15AA16C"]}],"id":[{"id":"https:\/\/ror.org\/0399mhs52","id-type":"ROR","asserted-by":"crossref"}]},{"name":"Office of the Vice President for Research, University of South Carolina","award":["15540-E422"],"award-info":[{"award-number":["15540-E422"]}],"id":[{"id":"https:\/\/ror.org\/02b6qw903","id-type":"ROR","asserted-by":"crossref"}]},{"award":["15540-E422"],"award-info":[{"award-number":["15540-E422"]}],"id":[{"id":"https:\/\/ror.org\/02b6qw903","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Carbon fiber-reinforced polymer composites can accumulate distributed microstructural damage before visible delamination or substantial stiffness loss becomes apparent. This article presents a program-based synthesis of six publications that examined precursor fatigue damage using guided coda waves, nonlinear guided waves, high-frequency pulse-echo ultrasonics, and scanning acoustic microscopy. The evidence comprises a separate incremental coda-wave campaign to 300,000 cycles and a coordinated fatigue-relaxation program conducted in three 75,000-cycle stages. Coda-wave interferometry detected progressive propagation changes while the first-arriving guided-wave packets remained largely unchanged. Nonlinear measurements showed changes in second- and third-order parameters and sideband peak counts, while the guided-wave nonlinear response decreased by as much as 26.8% during the 8 h unloaded period. This result demonstrates that post-loading measurement time must be controlled when transient stress-related and persistent damage-related responses are compared. Within the specific Route II material system and loading protocol, the 5 Hz specimens exhibited greater degradation than the 2 and 10 Hz specimens. This frequency ranking is not proposed as a general relationship for CFRP composites. Residual-strength testing, microscopy, and SAM provided convergent supporting evidence, but the overlapping datasets and small specimen groups do not constitute independent statistical replication. The proposed framework therefore demonstrates laboratory-scale sensitivity to precursor material-state changes but does not yet provide reliable prediction of residual strength, remaining fatigue life, or probability of failure. Field implementation will require larger independent datasets, uncertainty estimation, environmental compensation, repeated sensor installations, and validation on representative structural components.<\/jats:p>","DOI":"10.3390\/s26196190","type":"journal-article","created":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T16:33:12Z","timestamp":1790699592000},"page":"6190","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Ultrasonic Assessment of Precursor Fatigue Damage in CFRP Composites: A Synthesis of Coda Waves, Nonlinear Indicators, Stress Relaxation, and Validation"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8039-3841","authenticated-orcid":false,"given":"Hossain","family":"Ahmed","sequence":"first","affiliation":[{"name":"Department of Mechanical Engineering, Georgia Southern University, Statesboro, GA 30458, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2636-0157","authenticated-orcid":false,"given":"Sourav","family":"Banerjee","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of South Carolina, Columbia, SC 29208, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"143","DOI":"10.1016\/j.paerosci.2005.02.004","article-title":"Fibre reinforced composites in aircraft construction","volume":"41","author":"Soutis","year":"2005","journal-title":"Prog. Aerosp. Sci."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Baker, A.A., Dutton, S., and Kelly, D. (2004). Composite Materials for Aircraft Structures, American Institute of Aeronautics and Astronautics. [2nd ed.].","DOI":"10.2514\/4.861680"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2585","DOI":"10.1016\/j.compscitech.2008.04.042","article-title":"Damage and fatigue in composites\u2014A personal account","volume":"68","author":"Talreja","year":"2008","journal-title":"Compos. Sci. Technol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"2535","DOI":"10.1023\/A:1004684228765","article-title":"Fatigue damage mechanisms in unidirectional carbon-fibre-reinforced plastics","volume":"34","author":"Gamstedt","year":"1999","journal-title":"J. Mater. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"149","DOI":"10.1016\/0142-1123(91)90007-L","article-title":"A micromechanics model for composites under fatigue loading","volume":"13","author":"Reifsnider","year":"1991","journal-title":"Int. J. Fatigue"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Talreja, R., and Singh, C.V. (2012). Damage and Failure of Composite Materials, Cambridge University Press.","DOI":"10.1017\/CBO9781139016063"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"636","DOI":"10.1177\/0731684418754713","article-title":"Fatigue damage analysis of fiber-reinforced polymer composites\u2014A review","volume":"37","author":"Singh","year":"2018","journal-title":"J. Reinf. Plast. Compos."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"111659","DOI":"10.1016\/j.compositesb.2024.111659","article-title":"Review on methodologies of fatigue property prediction for carbon fiber reinforced polymer","volume":"284","author":"Li","year":"2024","journal-title":"Compos. Part B Eng."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Patra, S., and Banerjee, S. (2017). Material State Awareness for Composites Part I: Precursor Damage Analysis Using Ultrasonic Guided Coda Wave Interferometry (CWI). Materials, 10.","DOI":"10.3390\/ma10121436"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Rose, J.L. (2014). Ultrasonic Guided Waves in Solid Media, Cambridge University Press.","DOI":"10.1017\/CBO9781107273610"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Su, Z., and Ye, L. (2009). Identification of Damage Using Lamb Waves, Springer.","DOI":"10.1007\/978-1-84882-784-4"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"107014","DOI":"10.1016\/j.ultras.2023.107014","article-title":"A review on guided-ultrasonic-wave-based structural health monitoring: From fundamental theory to machine learning techniques","volume":"133","author":"Yang","year":"2023","journal-title":"Ultrasonics"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"100790","DOI":"10.1016\/j.paerosci.2021.100790","article-title":"Guided waves for structural health monitoring in composites: A review and implementation strategies","volume":"129","author":"Ricci","year":"2022","journal-title":"Prog. Aerosp. Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"725","DOI":"10.1080\/10589759.2024.2324149","article-title":"Non-destructive testing and structural health monitoring technologies for carbon fiber reinforced polymers: A review","volume":"39","author":"Han","year":"2024","journal-title":"Nondestruct. Test. Eval."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Tanveer, M., Elahi, M.U., Jung, J., Azad, M.M., Khalid, S., and Kim, H.S. (2024). Recent Advancements in Guided Ultrasonic Waves for Structural Health Monitoring of Composite Structures. Appl. Sci., 14.","DOI":"10.3390\/app142311091"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"102988","DOI":"10.1016\/j.ndteint.2023.102988","article-title":"The temperature effects on embedded PZT signals in structural health monitoring for composite structures with different thicknesses","volume":"141","author":"Ren","year":"2024","journal-title":"NDT E Int."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"117554","DOI":"10.1016\/j.compstruct.2023.117554","article-title":"Ultrasonic detection methods for mechanical characterization and damage diagnosis of advanced composite materials: A review","volume":"324","author":"Yang","year":"2023","journal-title":"Compos. Struct."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"046615","DOI":"10.1103\/PhysRevE.66.046615","article-title":"Coda wave interferometry and the equilibration of energy in elastic media","volume":"66","author":"Snieder","year":"2002","journal-title":"Phys. Rev. E"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1853","DOI":"10.1121\/1.3079771","article-title":"Monitoring stress related velocity variation in concrete with a 2 \u00d7 10\u22125 relative resolution using diffuse ultrasound","volume":"125","author":"Larose","year":"2009","journal-title":"J. Acoust. Soc. Am."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"248","DOI":"10.1016\/j.cemconres.2013.07.009","article-title":"A review of ultrasonic Coda Wave Interferometry in concrete","volume":"53","author":"Larose","year":"2013","journal-title":"Cem. Concr. Res."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1016\/S0041-624X(97)00040-1","article-title":"Fatigue damage assessment by nonlinear ultrasonic materials characterization","volume":"36","author":"Nagy","year":"1998","journal-title":"Ultrasonics"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"487","DOI":"10.1016\/S0142-1123(01)00162-1","article-title":"Nonlinear ultrasonic characterization of fatigue microstructures","volume":"23","author":"Cantrell","year":"2001","journal-title":"Int. J. Fatigue"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1007\/s12541-009-0019-y","article-title":"Nonlinear ultrasonic techniques for nondestructive assessment of micro damage in material: A review","volume":"10","author":"Jhang","year":"2009","journal-title":"Int. J. Precis. Eng. Manuf."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1007\/s10921-014-0273-5","article-title":"Review of Second Harmonic Generation Measurement Techniques for Material State Determination in Metals","volume":"34","author":"Matlack","year":"2015","journal-title":"J. Nondestruct. Eval."},{"key":"ref_25","unstructured":"(2017). Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials (Standard No. ASTM D3039\/D3039M-17)."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Ahmed, H., Saadatzi, M., Patra, S., and Banerjee, S. (2019). Entropy-Based Damage Evaluation of Composite Structure and Its Application to Structural Health Management. Structural Health Monitoring 2019, DEStech Publications, Inc.","DOI":"10.12783\/shm2019\/32387"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"224","DOI":"10.1016\/j.ultras.2019.01.002","article-title":"Evidence of dissipative and growing nonlinearity in Lamb waves due to stress-relaxation and material degradation in composites","volume":"96","author":"Patra","year":"2019","journal-title":"Ultrasonics"},{"key":"ref_28","first-page":"011005","article-title":"Effect of Time-Dependent Strength Recovery of Composite Materials: Quantification Through Higher Order Ultrasonic Non-Linearity Using Lamb Waves","volume":"3","author":"Patra","year":"2020","journal-title":"J. Nondestruct. Eval. Diagn. Progn. Eng. Syst."},{"key":"ref_29","first-page":"011004","article-title":"Precursor Damage Quantification in Composite Structures Using Coda Wave Interferometry and Nonlinear Ultrasonics","volume":"8","author":"Ahmed","year":"2025","journal-title":"J. Nondestruct. Eval. Diagn. Progn. Eng. Syst."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Ahmed, H., Sadaf, A.I., Khan, A.I., Akter, K., Rahman, M., and Banerjee, S. (2025). High frequency ultrasonics for precursor damage assessments in CFRP composite structures. Nondestruct. Test. Eval., 1\u201324.","DOI":"10.1080\/10589759.2025.2601837"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"107438","DOI":"10.1016\/j.ultras.2024.107438","article-title":"Evaluation of compressive damage in concrete using ultrasonic nonlinear coda wave interferometry","volume":"144","author":"Yi","year":"2024","journal-title":"Ultrasonics"},{"key":"ref_32","first-page":"L21302.1","article-title":"Passive image interferometry and seasonal variations of seismic velocities at Merapi Volcano, Indonesia","volume":"33","author":"Wegler","year":"2006","journal-title":"Geophys. Res. Lett."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"90","DOI":"10.1007\/s10921-024-01108-2","article-title":"The Detection of Local Impact Fatigue Damage on Metal Materials by Combining Nonlinear Acoustic Modulation and Coda Wave Interferometry","volume":"43","author":"Ma","year":"2024","journal-title":"J. Nondestruct. Eval."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"106991","DOI":"10.1016\/j.ultras.2023.106991","article-title":"Towards quantifying the effect of pump wave amplitude on cracks in the Nonlinear Coda Wave Interferometry method","volume":"132","author":"Qu","year":"2023","journal-title":"Ultrasonics"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"106695","DOI":"10.1016\/j.rinp.2023.106695","article-title":"Fatigue damage quantitative evaluation of carbon fiber composites at different stress ratios based on nonlinear ultrasonic","volume":"51","author":"Quan","year":"2023","journal-title":"Results Phys."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Amif, A., and Jack, D.A. (2024). High-Resolution Ultrasound to Quantify Sub-Surface Wrinkles in a Woven CFRP Laminate. Materials, 17.","DOI":"10.3390\/ma17092002"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"107214","DOI":"10.1016\/j.ultras.2023.107214","article-title":"Wavefield imaging of nonlinear ultrasonic Lamb waves for visualizing fatigue micro-cracks","volume":"138","author":"Xu","year":"2024","journal-title":"Ultrasonics"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"103238","DOI":"10.1016\/j.ndteint.2024.103238","article-title":"Amplitude-dependent second harmonic Lamb waves for discriminating delamination from background nonlinearities in composite plates","volume":"148","author":"Shan","year":"2024","journal-title":"NDT E Int."},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Adams, M., Huijer, A., Kassapoglou, C., Vaders, J.A.A., and Pahlavan, L. (2024). In Situ Non-Destructive Stiffness Assessment of Fiber Reinforced Composite Plates Using Ultrasonic Guided Waves. Sensors, 24.","DOI":"10.3390\/s24092747"},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Zhang, F., Zhang, K., Cheng, H., Gao, D., and Cai, K. (2024). Fatigue Damage Monitoring of Composite Structures Based on Lamb Wave Propagation and Multi-Feature Fusion. J. Compos. Sci., 8.","DOI":"10.3390\/jcs8100423"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"113443","DOI":"10.1016\/j.measurement.2023.113443","article-title":"Damage localization in carbon fiber composite plate combining ultrasonic guided wave instantaneous energy characteristics and probabilistic imaging method","volume":"221","author":"Teng","year":"2023","journal-title":"Measurement"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"119459","DOI":"10.1016\/j.compstruct.2025.119459","article-title":"CFRP composite fatigue damage pattern recognition using ultrasonic guided waves","volume":"371","author":"He","year":"2025","journal-title":"Compos. Struct."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Niu, X., Zhu, L., Yang, W., Yu, Z., and Shen, H. (2023). Temperature Effects on Nonlinear Ultrasonic Guided Waves. Materials, 16.","DOI":"10.3390\/ma16093548"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"18861","DOI":"10.1038\/s41598-024-69564-4","article-title":"Impact of temperature and relative humidity variations on coda waves in concrete","volume":"14","author":"Diewald","year":"2024","journal-title":"Sci. Rep."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Ma, Y., Li, F., Wu, J., Liu, Z., Xia, H., and Xu, Z. (2024). Detecting of Barely Visible Impact Damage on Carbon Fiber Reinforced Polymer Using Diffusion Ultrasonic Improved by Time-Frequency Domain Disturbance Sensitive Zone. Sensors, 24.","DOI":"10.3390\/s24103201"},{"key":"ref_46","doi-asserted-by":"crossref","unstructured":"Sellami, F., Memmolo, V., and Hornung, M. (2025). Guided Wave Propagation in a Realistic CFRP Fuselage Panel: Proof of Concept for Early-Stage Damage Detection. Sensors, 25.","DOI":"10.3390\/s25041104"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"035017","DOI":"10.1088\/1361-665X\/ad254c","article-title":"A metamaterial-assisted coda wave interferometry method with nonlinear guided waves for local incipient damage monitoring in complex structures","volume":"33","author":"Shan","year":"2024","journal-title":"Smart Mater. Struct."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"111858","DOI":"10.1016\/j.ymssp.2024.111858","article-title":"Ultrasonic guided wave-based probabilistic diagnostic imaging method with Single-Path-Scattering sparse reconstruction for Multi-Damage detection in composite structures","volume":"223","author":"Sun","year":"2025","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"107356","DOI":"10.1016\/j.ultras.2024.107356","article-title":"Data-driven online prediction of remaining fatigue life of a steel plate based on nonlinear ultrasonic monitoring","volume":"142","author":"Sun","year":"2024","journal-title":"Ultrasonics"},{"key":"ref_50","doi-asserted-by":"crossref","unstructured":"\u0160ofer, M., \u0160ofer, P., Pag\u00e1\u010d, M., Volodarskaja, A., Babiuch, M., and Gru\u0148, F. (2023). Acoustic Emission Signal Characterisation of Failure Mechanisms in CFRP Composites Using Dual-Sensor Approach and Spectral Clustering Technique. Polymers, 15.","DOI":"10.3390\/polym15010047"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"100295","DOI":"10.1016\/j.jcomc.2022.100295","article-title":"Dielectric state variables as qualitative indicators of moisture absorption-caused mechanical property degradation in GFRP composite structures","volume":"9","author":"Das","year":"2022","journal-title":"Compos. Part C Open Access"},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"111348","DOI":"10.1016\/j.matdes.2022.111348","article-title":"Advanced structural health monitoring in carbon fiber-reinforced plastic using real-time self-sensing data and convolutional neural network architectures","volume":"224","author":"Lee","year":"2022","journal-title":"Mater. Des."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"429","DOI":"10.1007\/s40030-026-00963-8","article-title":"Structural Health Monitoring of 44-Year-Old and Contemporary Bridges: Bearing Degradation and Dynamic Response","volume":"107","author":"Hussein","year":"2026","journal-title":"J. Inst. Eng. Ser. A"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1007\/s41024-025-00710-9","article-title":"Experimental validation of fatigue cycles to failure in prestressed concrete bridges by using structural health monitoring and exponential regression","volume":"11","author":"Hussein","year":"2026","journal-title":"J. Build. Pathol. Rehabil."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"110267","DOI":"10.1016\/j.ress.2024.110267","article-title":"A general approach to assessing SHM reliability considering sensor failures based on information theory","volume":"250","author":"Wu","year":"2024","journal-title":"Reliab. Eng. Syst. Saf."},{"key":"ref_56","doi-asserted-by":"crossref","first-page":"1969","DOI":"10.1177\/14759217231184589","article-title":"Noncontact nondestructive ultrasonic techniques for manufacturing defects monitoring in composites: A review","volume":"23","author":"Mortada","year":"2024","journal-title":"Struct. Health Monit."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/19\/6190\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T04:22:06Z","timestamp":1790828526000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/19\/6190"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,29]]},"references-count":56,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2026,10]]}},"alternative-id":["s26196190"],"URL":"https:\/\/doi.org\/10.3390\/s26196190","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,29]]}}}