Issue 71

Fracture and Structural Integrity - issue 71 (January 2025)

Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

Table of Contents

D.S. Lobanov, A.V. Lykova, A.M. Pankov, M.V. Ugolnikov https://youtu.be/h5AE6OqGEGA

Effect of internal technological defects and loading waveform on CFRP fatigue life ....…………. 1-10 A. Ibrahim, B. Niyaz Ahmed, E. Ashoka, A. M. Rajesh, P. B. Bharath, D. Saleemsab https://youtu.be/bblMWS65x4U Indentation fracture toughness of Aluminium-Graphite composites: influence of nano-particles ..... 11-21 M. C. Choukimath, N. R. Banapurmath, M. A. Umarfarooq https://youtu.be/Y_C8yBN_Gnc Mechanical, fracture and thermal characterization of post-cured hybrid epoxy nanocomposites reinforced with Graphene nanoplatelets and h-Boron Nitride ……………………………... 22-36 M. Vatnalmath, V. Auradi, V. Bharath, A. Bharadwaj, C. Gowda, M. Nagaral https://youtu.be/SMx-IZOI68Y Microstructure, mechanical and fractographic behaviour of the diffusion welded joints of AA2219 and Ti-6Al-4V for aerospace applications …...…………………………………….......... 37-48 Epoxy-based composites with size-fractionated waste Areca sheath: an experimental investigation on the macroscopic and vibrational properties ….......................................................................... 49-66 P. Doubek, I. Kumpová, L. Malíková, M. S. Al Khazali, S. Seitl https://youtu.be/EiBKAJwhMPA Determination of the geometric parameters of the defects based on the tomographically obtained data and their influence on the fatigue behavior of the S960 with laser cladded protective layers .... 67-79 N. E. Tenaglia, D. O. Fernandino, A. D. Basso https://youtu.be/TB152wd6VD4 Effect of cast part size on the microstructure and mechanical properties of a bainitic High-Carbon and High-Silicon Cast Steel …................................................................................................... 80-90 L. Varghese, G. C. Mohan Kumar https://youtu.be/YG-rC2DnRQA

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

K. Federowicz, K. Cendrowski, P. Sikora https://youtu.be/y_mbCTGLJLE Low-carbon cementitious composite incorporated with biochar and recycled fines suitable for 3D printing applications: hydration, shrinkage and early-age performance …..………….……...… 91-107 R. Di Bona, D. Gentile, G. P. Vanoli, G. Testa, S. Ricci https://youtu.be/FO_ZIeq7Lzo Integrated FEM-Multibody Co-Simulation of Additively Manufactured Hip Prosthesis containing cracks ………………………………………………………….................... 108-123 M. Abdulla, M. Hrairi, A. Aabid, N. A. Abdullah https://youtu.be/YulZjBFHIi4 Effect of temperature and adhesive defect on repaired structure using composite patch ......………. 124-150 P. Lehner, P. Pa ř enica, D. Jura č ka, M. Krejsa https://youtu.be/FrElY4dqEr0 Numerical analysis of 3D printed joint of wooden structures regarding mechanical and fatigue behaviour …………………………………………………………………....……… 151-163 A. Anjium, M. Hrairi, A. Aabid, N. Yatim, M. Ali https://youtu.be/NYuju4Vk79Q Integrating AI and statistical methods for enhancing civil structures: current trends, practical issues and future direction …….................................................................................................. 164-181 E. Kormanikova, K. Kotrasova https://youtu.be/j2FSvzkyfsY Numerical study of delamination process of the CFRP composite …............................................ 182-193 Y. Elmenshawy, . S. E. Ahmad, Y. O. El Gammal, H. M. El-Sheikh, M. Moawad, A. A. Elshami, M. A. R. Elmahdy https://youtu.be/Ahb30w2v1bU Investigating the repair of cracks through bacterial self-healing for sustainable concrete in aggressive sulfate attack environments ………………………...…………………………………. 194-210 K. Kozáková, L. Trávní č ek, J. Poduška, J. Klusák https://youtu.be/SgUCKbPuU0Y Critical length parameter of HDPE and its use in fatigue lifetime predictions ……………….. 211-222 E. A. Chechulina, V. A. Oborin, D. S. Gribov https://youtu.be/4-OhTuH7n7k The influence of plastic flow localization on the surface morphology of aluminum alloy specimens subjected to complex loading …...…............................................................................................ 223-238 A. N. Statnik, Iu. A. Sadykova, E. N. Prokopev, A. I. Salimon, E. V., Nazarov, N. V., Turbin, A.M. Korsunsky https://youtu.be/nqiDSAfzmcE Mechanical testing of miniature carbon fiber reinforced polymer (CFRP) samples under digital light microscopy …...….............................................................................................................. 239-245

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

S. Eleonsky, V. Pisarev https://youtu.be/E9HZlvytCoE Residual stresses caused by static and dynamic contact interaction of composite plate and steel spherical indenter …...…............................................................................................................ 246-262 V. Bilek, M. Pešata, K. Matyskova, P. Miarka https://youtu.be/M9-p_JCZMyw Long-term development of mechanical properties of concrete with different water to cement ratio and internal curing ability ……........................................................................................................ 263-272 J. Brozovsky, M. Krejsa, P. Lehner, P. Parenica, S. Seitl https://youtu.be/Z--KxiKV54U Stochastic modeling of structural fatigue damage in High Strength Steel structures ……............... 273-284 K. Annapoorna, R. Shobha, V. Bharath, S. Rajanna, S. Ashokkumar, M. Nagaral, V. Auradi https://youtu.be/WEcoRpHXLqM Effect of hybrid nano particle reinforcements on fractographic, mechanical and wear behavior of Al6061 alloy composites manufactured by ultrasonic assisted stir casting technique ………….... 285-301 C. F. Markides, S. K. Kourkoulis https://youtu.be/wYmkn34AujM Revisiting classical concepts of Linear Elastic Fracture Mechanics - Part III: The stress field in a double-edge notched finite strip by means of the “stress-neutralization” technique ……....…….... 302-316 A. Bravo Celi, D. Falliano, S. Parmigiani, D. Suarez-Riera, G. A. Ferro, L. Restuccia https://youtu.be/rH57JJvKouo Reuse of sheep wool fibers in the production of ultralightweight foamed concrete: effect of fiber treatment, length, and content on the mechanical properties ……....................................…….... 317-329 A. Khan, B. K. Naveen Kumar, K. J. Anand, E. Ashoka, G. Hareesha https://youtu.be/COg14l25eKk Development and mechanical characterization of eggshell bio-filler reinforced bamboo fiber composites ……....................................……………………………...………………..... 330-340

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

Editorial Team

Editor-in-Chief Francesco Iacoviello

(Università di Cassino e del Lazio Meridionale, Italy)

Co-Editor in Chief Sabrina Vantadori

(Università di Parma, Italy)

Filippo Berto Jianying He

(Università di Roma “Sapienza”, Italy)

(Norwegian University of Science and Technology (NTNU), Trondheim, Norway)

Section Editors Sara Bagherifard Vittorio Di Cocco Stavros Kourkoulis

(Politecnico di Milano, Italy)

(Università di Cassino e del Lazio Meridionale, Italy) (National Technical University of Athens, Greece) (National Technical University of Athens, Greece)

Ermioni Pasiou

(Perm federal research center Ural Branch Russian Academy of Sciences, Russian Federation)

Oleg Plekhov

Ł ukasz Sadowski Daniela Scorza

(Wroclaw University of Science and Technology, Poland)

(Università di Parma, Italy)

Advisory Editorial Board Harm Askes

(University of Sheffield, Italy) (Tel Aviv University, Israel) (Politecnico di Torino, Italy) (Università di Parma, Italy) (Politecnico di Torino, Italy) (Politecnico di Torino, Italy)

Leslie Banks-Sills Alberto Carpinteri Andrea Carpinteri Giuseppe Ferro Youshi Hong M. Neil James Gary Marquis Liviu Marsavina Thierry Palin-Luc Robert O. Ritchie Yu Shou-Wen Darrell F. Socie Ramesh Talreja David Taylor Cetin Morris Sonsino Donato Firrao Emmanuel Gdoutos Ashok Saxena Aleksandar Sedmak

(Democritus University of Thrace, Greece) (Chinese Academy of Sciences, China)

(University of Plymouth, UK)

(Helsinki University of Technology, Finland)

(University Politehnica Timisoara, Department of Mechanics and Strength of Materials, Romania) (Ecole Nationale Supérieure d'Arts et Métiers | ENSAM · Institute of Mechanics and Mechanical Engineering (I2M) – Bordeaux, France)

(University of California, USA)

(Galgotias University, Greater Noida, UP, India; University of Arkansas, USA)

(University of Belgrade, Serbia)

(Department of Engineering Mechanics, Tsinghua University, China)

(University of Illinois at Urbana-Champaign, USA)

(Fraunhofer LBF, Germany) (Texas A&M University, USA) (University of Dublin, Ireland)

John Yates

(The Engineering Integrity Society; Sheffield Fracture Mechanics, UK)

Regional Editorial Board Nicola Bonora

(Università di Cassino e del Lazio Meridionale, Italy)

Raj Das

(RMIT University, Aerospace and Aviation department, Australia)

Dorota Koca ń da

(Military University of Technology, Poland)

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

Stavros Kourkoulis Carlo Mapelli Liviu Marsavina

(National Technical University of Athens, Greece)

(Politecnico di Milano, Italy)

(University of Timisoara, Romania) (Tecnun Universidad de Navarra, Spain)

Antonio Martin-Meizoso Mohammed Hadj Meliani

(LPTPM , Hassiba Benbouali University of Chlef. Algeria) (Indian Institute of Technology/Madras in Chennai, India)

Raghu Prakash

Luis Reis Elio Sacco

(Instituto Superior Técnico, Portugal) (Università di Napoli "Federico II", Italy) (University of Belgrade, Serbia) (Tel-Aviv University, Tel-Aviv, Israel)

Aleksandar Sedmak

Dov Sherman Karel Sláme č ka

(Brno University of Technology, Brno, Czech Republic) (Middle East Technical University (METU), Turkey)

Tuncay Yalcinkaya

Editorial Board Jafar Albinmousa Mohammad Azadi Nagamani Jaya Balila

(King Fahd University of Petroleum & Minerals, Saudi Arabia) ( Faculty of Mechanical Engineering, Semnan University, Iran) (Indian Institute of Technology Bombay, India) (Università di Cassino e del Lazio Meridionale, Italy) (Institute of sciences, Tipaza University center, Algeria) (GM Institute of Technology, Dept. Of Mechanical Engg., India)

Costanzo Bellini

Oussama Benaimeche

K. N. Bharath

Alfonso Fernández-Canteli

(University of Oviedo, Spain) (University of Mascara, Algeria)

Bahri Ould Chikh

Angélica Bordin Colpo

(Federal University of Rio Grande do Sul (UFRGS), Brazil)

Mauro Corrado

(Politecnico di Torino, Italy)

Dan Mihai Constantinescu

(University Politehnica of Bucharest, Romania)

Abílio de Jesus

(University of Porto, Portugal) (Università della Calabria, Italy) (University of Belgrade, Serbia)

Umberto De Maio

Milos Djukic

Andrei Dumitrescu

(Petroleum-Gas University of Ploiesti, Romania)

Devid Falliano

(Dipartimento di Ingegneria Strutturale, Edile e Geotecnica, Politecnico di Torino, Italy)

Leandro Ferreira Friedrich

(Federal University of Pampa (UNIPAMPA), Brazil)

Parsa Ghannadi Eugenio Giner

(Islamic Azad university, Iran)

(Universitat Politècnica de València, Spain) (Université-MCM- Souk Ahras, Algeria) (Middle East Technical University, Turkey) (Hassiba Benbouali University of Chlef, Algeria) (Università di Roma “La Sapienza”, Italy)

Abdelmoumene Guedri

Ercan Gürses

Abdelkader Hocine Daniela Iacoviello

Ali Javili

(Bilkent University, Turkey) (University of Piraeus, Greece) (Federal University of Pampa, Brazil)

Dimitris Karalekas

Luis Eduardo Kosteski

Sergiy Kotrechko Grzegorz Lesiuk

(G.V. Kurdyumov Institute for Metal Physics, N.A.S. of Ukraine, Ukraine)

(Wroclaw University of Science and Technology, Poland)

Qingchao Li Paolo Lonetti

(Henan Polytechnic University, China)

(Università della Calabria, Italy)

Tomasz Machniewicz

(AGH University of Science and Technology) (Università Politecnica delle Marche, Italy)

Erica Magagnini Carmine Maletta

(Università della Calabria, Italy) (Università Roma Tre, Italy) (University of Porto, Portugal) (University of Porto, Portugal) (University of Bristol, UK)

Sonia Marfia

Lucas Filipe Martins da Silva

Pedro Moreira

Mahmoud Mostafavi

Madeva Nagaral

(Aircraft Research and Design Centre, Hindustan Aeronautics Limited Bangalore, India)

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

Vasile Nastasescu Stefano Natali Pavlos Nomikos

(Military Technical Academy, Bucharest; Technical Science Academy of Romania)

(Università di Roma “La Sapienza”, Italy) (National Technical University of Athens, Greece)

(Karpenko Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Ukraine)

Hryhoriy Nykyforchyn

Marco Paggi

(IMT Institute for Advanced Studies Lucca, Italy) (Università di Cassino e del Lazio Meridionale, Italy)

Gianluca Parodo Arturo Pascuzzo

(Università della Calabria, Italy)

Hiralal Patil

(GIDC Degree Engineering College, Abrama-Navsari, Gujarat, India)

Alessandro Pirondi Andrea Pranno Zoran Radakovi ć D. Mallikarjuna Reddy

(Università di Parma, Italy) (Università della Calabria)

(University of Belgrade, Faculty of Mechanical Engineering, Serbia) (School of Mechanical Engineering, Vellore Institute of Technology, India)

Luciana Restuccia

(Politecnico di Torino, Italy) (Università di Padova, Italy) (Università di Messina, Italy) (Università di Parma, Italy)

Mauro Ricotta

Giacomo Risitano Camilla Ronchei

Hossam El-Din M. Sallam

(Jazan University, Kingdom of Saudi Arabia) (Università di Roma "Tor Vergata", Italy)

Pietro Salvini Mauro Sassu Raffaele Sepe

(Università di Cagliari, Italy) (Università di Salerno, Italy)

Abdul Aabid Shaikh

(Prince Sultan University, Saudi Arabia)

Dariusz Skibicki Marta S ł owik Luca Sorrentino Andrea Spagnoli Cihan Teko ğ lu Dimos Triantis Andrea Tridello

(UTP University of Science and Technology, Poland)

(Lublin University of Technology, Poland)

(Università di Cassino e del Lazio Meridionale, Italy)

(Università di Parma, Italy)

(TOBB University of Economics and Technology, Ankara, Turkey)

(University of West Attica, Greece) (Politecnico di Torino, Italy) (Università di Pisa, Italy) (Universidade de Brasília, Brasilia) (Kettering University, Michigan,USA)

Paolo Sebastiano Valvo Cristian Vendittozzi

Charles V. White Andrea Zanichelli Shun-Peng Zhu

(Università di Parma, Italy)

(University of Electronic Science and Technology of China, China)

Special Issue

Modeling in Structural Integrity

Bartlomiej Blachowski

(IPPT PAN, Poland)

(VSB-Technical University of Ostrava, Czech Republic) (VSB-Technical University of Ostrava, Czech Republic)

Martin Krejsa Petr Lehner

Majid Movahedi Rad

(Széchenyi István University, Hungary) (California State University Fullerton, USA)

Ghosh Pratanu

Alexander Sedmak

(University of Belgrade, Serbia)

Special Issue

Russian mechanics contributions for Structural Integrity

(Mechanical Engineering Research Institute of the Russian Academy of Sciences, Russia) (Institute of Continuous Media Mechanics of the Ural Branch of Russian Academy of Science, Russia)

Valerii Pavlovich Matveenko

Oleg Plekhov

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

Special Issue

Damage Mechanics of materials and structures

Shahrum Abdullah

(Universiti Kebangsaan Malaysia) (Universiti Kebangsaan Malaysia)

Salvinder Singh

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

Fracture and Structural Integrity (Frattura ed Integrità Strutturale) is an Open Access journal affiliated with ESIS

Sister Associations help the journal managing Algeria: Algerian Association on Fracture Mechanics and Energy -AGFME Australia: Australian Fracture Group – AFG Czech Rep.: Asociace Strojních Inženýr ů (Association of Mechanical Engineers) Greece: Greek Society of Experimental Mechanics of Materials - GSEMM India: Indian Structural Integrity Society - InSIS Israel: Israel Structural Integrity Group - ISIG Italy: Associazione Italiana di Metallurgia - AIM Italy: Associazione Italiana di Meccanica Teorica ed Applicata - AIMETA Italy:

Società Scientifica Italiana di Progettazione Meccanica e Costruzione di Macchine - AIAS Group of Fatigue and Fracture Mechanics of Materials and Structures

Poland: Portugal:

Portuguese Structural Integrity Society - APFIE Romania: Asociatia Romana de Mecanica Ruperii - ARMR Serbia:

Structural Integrity and Life Society "Prof. Stojan Sedmak" - DIVK Grupo Espanol de Fractura - Sociedad Espanola de Integridad Estructural – GEF

Spain: Turkey: Ukraine:

Turkish Solid Mechanics Group

Ukrainian Society on Fracture Mechanics of Materials (USFMM)

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

Journal description and aims Fracture and Structural Integrity (Frattura ed Integrità Strutturale) is the official Journal of the Italian Group of Fracture. It is an open-access Journal published on-line every three months (January, April, July, October). Frattura ed Integrità Strutturale encompasses the broad topic of structural integrity, which is based on the mechanics of fatigue and fracture and is concerned with the reliability and effectiveness of structural components. The aim of the Journal is to promote works and researches on fracture phenomena, as well as the development of new materials and new standards for structural integrity assessment. The Journal is interdisciplinary and accepts contributions from engineers, metallurgists, materials scientists, physicists, chemists, and mathematicians. Contributions Fracture and Structural Integrity is a medium for rapid dissemination of original analytical, numerical and experimental contributions on fracture mechanics and structural integrity. Research works which provide improved understanding of the fracture behaviour of conventional and innovative engineering material systems are welcome. Technical notes, letters and review papers may also be accepted depending on their quality. Special issues containing full-length papers presented during selected conferences or symposia are also solicited by the Editorial Board. Manuscript submission Manuscripts must be written using a standard word file without any specific format and submitted via e-mail to gruppofrattura@gmail.com. Papers should be written in English. A confirmation of reception will be sent within 48 hours. The review and the on-line publication process will be concluded within three months from the date of submission. Peer review process Fracture and Structural Integrity adopts a single blind reviewing procedure. The Editor in Chief receives the manuscript and, considering the paper’s main topics, the paper is remitted to a panel of referees involved in those research areas. They can be either external or members of the Editorial Board. Each paper is reviewed by two referees. After evaluation, the referees produce reports about the paper, by which the paper can be: a) accepted without modifications; the Editor in Chief forwards to the corresponding author the result of the reviewing process and the paper is directly submitted to the publishing procedure. b) accepted with minor modifications or corrections (a second review process of the modified paper is not mandatory); the Editor in Chief returns the manuscript to the corresponding author, together with the referees’ reports and all the suggestions, recommendations and comments therein. c) accepted with major modifications or corrections (a second review process of the modified paper is mandatory); the Editor in Chief returns the manuscript to the corresponding author, together with the referees’ reports and all the suggestions, recommendations and comments therein. d) rejected. The final decision concerning the papers publication belongs to the Editor in Chief and to the Associate Editors. The reviewing process is usually completed within three months. The paper is published in the first issue that is available after the end of the reviewing process.

Publisher Gruppo Italiano Frattura (IGF) http://www.gruppofrattura.eu ISSN 1971-8993 Reg. Trib. di Cassino n. 729/07, 30/07/2007

Fracture and Structural Integrity (Frattura ed Integrità Strutturale) is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0)

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Fracture and Structural Integrity 71 (2025); International Journal of the Italian Group of Fracture

Fracture and Structural Integrity news

D

ear friends, as we embark on the first issue of 2025, I'm pleased to share a brief overview of FIS's activity throughout the past year. In 2024, we received 446 submissions and published 85 papers, resulting in an 84% rejection rate (73% at desk). The average time to rejection was just one day, and the time from submission to acceptance decreased significantly from 69 days in January 2024 to 48 days in October 2024. We published four issues featuring authors from a diverse range of countries, with representation from 11 countries in the July issue to 19 countries in the April issue. Furthermore, 2024 saw the implementation of a new publishing schedule, enabling immediate paper publication upon acceptance of proofs and the uploading of Visual Abstracts. All these results were possible only to a great community! We extend our sincere gratitude to the Editorial Boards, Reviewers, Section Editors, Guest Editors, and Authors for their invaluable contributions! The journal's success is a direct result of their dedication and effort. We begin this new year with an important announcement. Since 2007, the journal has been registered with a dual title: " Frattura ed Integrità Strutturale " in Italian and " Fracture and Structural Integrity " in English. To enhance accessibility and searchability, we have decided to adopt the English title as the primary one. Therefore, starting with the January 2025 issue, the official title of our journal is " Fracture and Structural Integrity ," with the Italian title as the “parallel”. In this issue, we are excited to introduce a new initiative for our readers: Thematic Virtual Issues. Prestigious authors will delve into hot topics in the fields of fracture and structural integrity in a series of papers. Christos F. Markides and Stavros K. Kourkoulis from the National Technical University of Athens, Greece, prepared the first Virtual Thematic Issue, "Revisiting Classical Concepts of Linear Elastic Fracture Mechanics". We hope you enjoy this new offering! Finally, mark your calendars for the upcoming joint conference organized by IGF: IGF28 - MedFract3 (https://www.igf28-medfract3.eu/). This event combines the 28th International Conference on Fracture and Structural Integrity (IGF28) with the 3rd Mediterranean Conference on Fracture and Structural Integrity (MedFract3) . The conference will be held both in person in the beautiful setting of Aci Castello (Catania, Italy) and remotely. While remote participants will be able to fully engage in all sessions and discussions, they will unfortunately miss the opportunity to savor the delicious cuisine of Sicily! The main deadlines are: - Registration: always open - Abstract Submission: 1.11.2024 to 31.05.2025 - Acceptance notification: 10.06.2025 - Early bird registration and payment: 31.07.2025 - Conference: 15.09.2025 - 18.09.2025 - Paper submission (after the conference): 15.10.2025 - Papers acceptance: 31.10.2025 Ciao Francesco Iacoviello Fracture and Structural Integrity Editor in Chief

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

Effect of internal technological defects and loading waveform on CFRP fatigue life

D.S. Lobanov, A.V. Lykova, A.M. Pankov, M.V. Ugolnikov Center of Experimental Mechanics, Perm National Research Polytechnic University, Russia

cem.lobanov@gmail.com, https://orcid.org/0000-0003-1948-436X cem.lykova@gmail.com, https://orcid.org/0000-0003-4873-6351 cem.pankov@gmail.com, https://orcid.org/0000-0001-7505-1484 mugolnikov@icloud.com, https://orcid.org/0009-0003-9997-1615

Citation: Lobanov, D.S., Lykova, A.V., Pankov, A.M., Ugolnikov, M.V., Effect of Internal Technological Defects and Loading Waveform on Structural Composite Fatigue Life, Fracture and Structural Integrity, 71 (2025) 1-10.

Received: 08.08.2024 Accepted: 01.10.2024 Published: 06.10.2024 Issue: 01.2025

Copyright: © 2024 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

K EYWORDS . Carbon-fiber composite, Mechanical behavior, Dry-spot, Wrinkles, Fatigue, Tension.

I NTRODUCTION

olymer composite materials are increasingly being prioritized in the design and manufacture of critical components in the aerospace industry due to their unique properties and advantages over traditional materials [1, 2]. However, the implementation of composites necessitates the development of manufacturing technologies [3]. The production process for composite parts can introduce various defects that may adversely affect the operational and strength performance of the final product. To identify various technological defects in composites, the most commonly used methods include ultrasonic testing [4-6], X-ray inspection [7], thermography [8, 9], acoustic emission testing [10], and fiber optic sensors [11, 12]. These techniques P

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

help mitigate potential risks from defects during production, but there are some defects which impact on operational and strength characteristics may not always be severe. Thus, further research in this area remains relevant. Various approaches are used to study the impact of defects on material properties, including computer modeling and experimental studies. Computer modeling enables predicting material behavior with defects under different operating conditions. It is possible to calculate stress and strain distributions within the material through numerical methods and assess its strength and rigidity [13, 14]. Experimental studies involve testing actual material specimens with various types of defects, providing more precise data on material behavior. These experiments can include tensile, compressive, bending, torsional, and other types of loading tests [15-17]. There are several methods for creating composites, with prepreg technology currently being the most widely used. During the manufacturing process with this technology, various defects can arise, including wrinkling, dry spots, internal delamination, foreign inclusions, cracks, voids, and other imperfections. These defects can significantly diminish both the static and fatigue strength of the product. Therefore, understanding the effect of defect size, geometry, and location on the mechanical properties of materials is crucial [18]. The ASTM E2533-09, Standard Guide for Nondestructive Examination of Polymer Matrix Composites Used in Aerospace Applications, is a key regulatory document that defines these defects in composites. Research [19-21] also indicates that the loading cycle waveform can significantly influence the pattern of damage accumulation in a material. Certain waveforms may lead to more uniform damage accumulation, potentially extending the material's life. Conversely, other waveforms can cause rapid damage accumulation in specific materials, adversely affecting their fatigue properties. This study builds upon previous research [22, 23], which examined static tests of CFRP specimens with introduced technological defects (such as wrinkles and dry spots) under tension and compression. The research utilized systems such as acoustic emission and digital image correlation to identify the locations of defects and assess their impact on the mechanical properties of CFRP. However, to gain a more comprehensive understanding of material behavior under real operating conditions, it is essential to conduct cyclic tests. These tests assess the material's fatigue life and evaluate how different loading waveforms affect its ability to endure repeated stresses without degrading its properties. This study aims to evaluate the impact of internal defects, such as dry-spot and wrinkling, on the fatigue life of CFRP under triangular and sinusoidal loading waveforms. n experimental research program was developed and performed to investigate the impact of internal technological defects on the fatigue life of structural CFRP under various cyclic loading waveforms. Specimens of structural CFRP (carbon-fiber-reinforced polymer laminate VKU 60) were made from prepreg VKU with using an epoxy binder (VSE-58) based on the autoclave molding technology. The lay-up scheme was [0/90]10. Specimens were made with the incorporated defect simulators. The primary technological defects included internal delaminations (dry-spot) with a circular shape and wrinkling (Z-shaped bends of the inner layer). The defects were positioned at the geometric center of the specimen, as illustrated in Fig. 1. Drafts of the specimens with geometric sizes are shown in Fig. 1a. The location of defects within the layer pack is shown in Fig. 1b. As embedded defects (dry-spot), a technological release film (special insulation sheet) was artificially inserted. To determine the cyclic loading parameters, all groups of specimens were first tested for quasi-static tension: (1) specimens without a defect, (2) specimens with the dry-spot defect in the form of a circle with a diameter of 10 mm, and (3) specimens with the wrinkling defect across the entire width of the specimen and a height of 10 mm. Three specimens from each group were tested. Tensile tests were conducted using an Instron 5982 electromechanical testing system (100 kN). The loading rate during tensile tests for all specimen groups was 2 mm/min. The results of the static tension tests are presented in Tab. 1. Based on the results of the quasi-static tests, a fatigue life test program was developed for all series of CFRP specimens under different waveforms. Fatigue life tests were conducted using an MTS Landmark 370.10 servohydraulic system, with a maximum load of 100 kN and a frequency of 30 Hz, under sine and triangle waveforms, as shown in Fig. 2a. The appearance of the test system is depicted in Fig. 2b. Cyclic loading parameters were set as follows: frequency of 10 Hz, stress ratio R = 0.1, and a ratio of maximum stress in the cycle to the ultimate strength of the material σ / σ в = 0.44-0.75 (Tab. 2). The average maximum stress values for each group A M ATERIAL AND METHODS

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

of specimens were used as the ultimate strength (see Tab. 1). The failure criterion was defined as either a 50% reduction in maximum load from cycle to cycle or the destruction of the specimen into parts.

a b Figure 1: Scheme of specimens ( a) with internal defects ( b ) "dry-spot" and "winkles" [25].

Maximum load, kN

Maximum stress, MPa

Defect

Without defect Dry-spot, a circle

26.1 25.9 23.8

801 801

Wrinkles 712 Table 1: Results of static tensile tests of CFRP specimens.

Defect

σ / σ в

Waveform cycle

R

1 2 3 4 5 6 7 8 9

Without defect Without defect Without defect Without defect Without defect Without defect

triangle triangle triangle

0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

0.56 0.64 0.44 0.48 0.56 0.44 0.56 0.64 0.75 0.70 0.64 0.75 0.70 0.70 0.65 0.70 0.75 0.70 0.75 0.65

sinus sinus sinus sinus sinus sinus sinus

Dry-spot Dry-spot Dry-spot Dry-spot Dry-spot Dry-spot Dry-spot Dry-spot Wrinkles Wrinkles Wrinkles Wrinkles Wrinkles Wrinkles

10 11 12 13 14 15 16 17 18 19 20

triangle triangle triangle triangle

sinus sinus sinus

triangle triangle triangle

Table 2: Loading parameters of specimens.

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

a с Figure 2: a – MTS Landmark 370.10 system; b – fatigue testing; c – waveforms of cyclic loading (sinus, triangle). b

R ESULTS AND DISCUSSION

B

ased on experimental data, the influence of critical internal defects on the fatigue life of a polymer structural composite material was assessed for triangular and sinusoidal waveforms. The influence of cycle waveform on the fatigue life of specimens with various defect types was assessed by plotting tensile fatigue curves, which are displayed in Figs. 3-5. Open points signify runouts, meaning specimens that were tested but did not reach failure due to having achieved the test limit. The lines in the figures represent a power law approximation of the test data.

Figure 3: Fatigue curves for defect-free specimens for different waveforms: ● indicates sinusoidal, ▲ indicates triangular; open points correspond to runouts. When comparing the curves for specimens without defects, with the dry-spot defect, and with the Z-shaped wrinkling defect, no effect of waveform (sinusoidal/triangular) on the fatigue life of structural CFRP was observed. In carbon fiber

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

plastic, during fatigue tests, damage accumulates such as matrix cracking, delamination and fiber damage, while in metals the accumulation of damage is mainly associated with the movement of dislocations, which requires much less energy. This is probably why the influence of the cycle shape for carbon fiber reinforced plastics is less pronounced than for metals. Therefore, to study the effect of defects on tensile fatigue life, the results from specimens tested with sinusoidal and triangular cycle shapes were combined.

Figure 4: Fatigue curves for specimens with the dry-spot defect for different waveforms: ● indicates sinusoidal, ▲ indicates triangular; open points correspond to runouts.

Figure 5: Fatigue curves for specimens with the Z-shaped wrinkling defect for different waveforms: ● indicates sinusoidal, ▲ indicates triangular.

The results of the fatigue tests were used to plot fatigue curves that demonstrate the influence of defect types on the fatigue life of CFRP. Fig. 6 displays combined fatigue life curves for various defect types, shown in absolute and relative values. For each group of specimens, its corresponding ultimate strength was used. The Basquin function is essential in material fatigue analysis. This well-known approach, with its different variations, continues to be frequently used by researchers in their studies. For instance, see studies [24, 25]. The Basquin function can be expressed as follows:

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

  

  b N a N *

(1)

For a numerical comparison, the Basquin equation parameters were determined for both defect-free specimens and those with technological defects. The results are presented in Tab. 3.

Defect

a

b

Without a defect

1017

0.0308 0.0304

Dry-spot Wrinkles

988 722

0.0319 Table 3: Basquin equation parameters for fatigue curves.

a

b Figure 6: Fatigue curves in absolute ( а ) and relative ( b ) values: ● indicates defect absence, ■ indicates dry-spot, ▲ indicates Z-shaped wrinkling.

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

Since the parameter b is approximately constant within the range from 7000 to 2×10 6 cycles, a variation in the parameter b by 0.0015 results in a difference of less than 1% in the calculated stresses. Therefore, it can be assumed that the decrease in stresses at a fixed fatigue life due to defects can be estimated by the ratio of the parameters a . It is found that with the delamination (dry-spot) defect, the stress decreases by approximately 3%, and with the wrinkling defect, it decreases by about 29%. Similarly, the drop in fatigue life at constant stresses for the dry-spot defect is calculated. The decrease in life at the same stress level is approximately 2.5 times over the entire range considered (Fig. 6a). For samples with the wrinkling defect, a quantitative comparison of fatigue life is not possible because their ranges of applied stresses do not overlap. When fatigue life curves are constructed in relative values (Fig. 6b), the effect of the wrinkling defect on the fatigue life of CFRP is practically unobserved. This indicates that for this material, the drop in fatigue properties due to the wrinkling defect corresponds to a reduction in strength properties. To evaluate the effect of defects on cyclic durability in both low-cycle and high-cycle fatigue tests, the effective stress concentration factor can be used as an analogy. This factor is derived by comparing the fatigue limits of specimens with and without stress concentrations. In this study, internal technological defects in CFRP specimens are considered as stress concentrators. To observe the differences in material behavior across the entire durability range, the coefficient of the effect of internal technological defects on fatigue resistance ( k f ) will be calculated. This coefficient is defined as the ratio of the stress amplitude of a defect-free specimen to that of a specimen with a defect for the same level of fatigue life. The calculations will be performed in a range from 3×10 3 to 3×10 6 . Fig. 7 illustrates the relationship between the calculated parameter ( k f ) and fatigue life ( N ) for specimens containing defects such as dry-spot and Z-shaped wrinkling.

Figure 7: Dependence of the coefficient of the effect of internal technological defects on fatigue resistance: ■ indicates specimens with dry-spot, ▲ indicates specimens with Z-shaped wrinkling. The graph indicates that the effect of each defect is consistent across the entire durability range, with no significant differences observed in high-cycle and low-cycle regions. Fig. 8 displays typical photographs of specimens with different types of defects after fatigue testing. Notably, similar to static tensile tests, specimens without defects typically failed near or within the grips, while those with internal technological defects failed in the working zone. In particular, during static tensile tests, specimens with delamination (dry-spot) defects failed in the grip region, whereas those with wrinkling defects failed in the working region along the defect boundary. Fig. 8b illustrates a circle of fluoroplastic film representing a dry-spot defect, with its continuation inside the specimen marked by a yellow dashed semicircle. The fracture surface analysis of CFRP specimens with internal technological defects revealed that defect-free specimens failed by transverse tearing near the grips, where additional mechanical impacts occurred (Fig. 8a). Specimens with dry-spot defects experienced internal delamination at the location of the embedded defect (Fig. 8b, yellow ellipses), followed by subsequent fiber fracture. Specimens with a Z-shaped wrinkling defect exhibited multiple delaminations across the thickness of the specimen in the defect area (Fig. 8c, yellow ellipse), which led to the development of a longitudinal main crack between the 5th and 6th layers (Fig. 8c, red rectangle) where the defect was embedded, resulting in the fracture of the loaded fibers.

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

a

b

c Figure 8: Typical photographs and fracture surfaces of failed specimens: a) without defect; b) with the dry-spot defect (circular shape); c) with the wrinkling defect (Z-shaped layer bend).

C ONCLUSIONS

N

ew experimental data on the effect of loading waveform and internal technological defects (such as dry-spot and wrinkling) on the fatigue life of VKU CFRP under cyclic tension have been obtained. Fatigue curves were constructed based on cyclic tensile tests for various waveforms and defects. The study finds that:  Internal technological defects, particularly wrinkling, significantly reduce the fatigue life of CFRP. At a fixed fatigue life, stress levels decreased by approximately 3% for specimens with delamination (dry-spot) defects and by about 29% for specimens with Z-shaped wrinkling defects. Similarly, for fixed stress levels, the fatigue life of specimens with dry-spot defects decreased by about 2.5 times compared to defect-free specimens across the entire range considered.  The type of loading waveform (sine vs. triangle) does not significantly influence the fatigue life of both defect-free and defected CFRP specimens.  The reduction in fatigue properties corresponds to a decrease in the material's strength properties for wrinkling defects.  Fracture surface analysis after static and cyclic tests revealed that dry-spot defects lead to a change in the failure mechanism of CFRP. During fatigue tests, failure initiates from delamination, followed by fiber fracture in the defect area. In the next stage, the authors plan to study the fatigue life of material specimens with defects under complex cycle shapes and negative stress ratios.

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

A CKNOWLEDGEMENTS

T

his research was funded by Ministry of science and higher education of the Russian Federation (Project No FSNM 2024-0013).

R EFERENCES

[1] Mouritz, P. (2012). Introduction to Aerospace Materials, Woodhead Publishing Limited. DOI: 10.1533/9780857095152.1.

[2] Rajak, D. K., Wagh, P. H., Kumar, A., Behera, A., Pruncu, C. I. (2022). Advanced polymers in aircraft structures, In: Materials, Structures and Manufacturing for Aircraft, Cham, Springer, pp. 65–88. DOI: 10.1007/978-3-030-91873-6_3. [3] Gunyaeva, A.G., Sidorina, A.I., Kurnosov, A.O., Klimenko, O.N. (2018). Polymeric composite materials of new generation on the basis of binder vse-1212 and the filling agents alternative to ones of Porcher Ind. and Toho Tenax, Aviation materials and technologies., 3(52), pp. 18–26. DOI: 10.18577/2071-9140-2018-0-3-18-26. (In Russia). [4] Boichuk, A.S., Dikov, I.A., Chertishchev, V.Y. (2019). Determining Porosity of Monolithic Zones in Aircraft Parts and Assemblies Made of PCMs Using Ultrasound Pulse Echo Method, Russ J Nondestruct., 55, pp. 1–7. DOI: 10.1134/S1061830919010029. [5] Murashov, V.V., Aleksashin, V.M., Mishurov, K.S. (2019). Determination of the polymerization degree of the matrix of polymer composite material using ultrasonic method, Industrial laboratory. Diagnostics of materials, 85, pp. 33-39. DOI: 10.26896/1028-6861-2019-85-4-33-39. [6] Ma, M. (2020). High precision detection method for delamination defects in carbon fiber composite laminates based on ultrasonic technique and signal correlation algorithm, Materials, 13(17), pp. 3840. DOI: 10.3390/ma13173840. [7] Chai, Y. (2020). Damage evolution in braided composite tubes under torsion studied by in-situ X-ray computed tomography, Composites Science and Technology, 188, pp. 107976. DOI: 10.1016/j.compscitech.2019.107976. [8] Liu, H. (2021). A dissection and enhancement technique for combined damage characterisation in composite laminates using laser-line scanning thermography, Composite Structures., 271(12), pp. 114168. DOI: 10.1016/j.compstruct.2021.114168. [9] Mariani, A., Malucelli, G. (2023). Insights into Induction Heating Processes for Polymeric Materials: An Overview of the Mechanisms and Current Applications, Energies, 16(11), pp. 4535. DOI: 10.3390/en16114535. [10] Zubova, E.M., Lobanov, D.S., Strungar, E.M., Wildeman, V.E., Lyamin, Y.B. (2019). Application of the acoustic emission technique to studying the damage accumulation in a functional ceramic coating, PNRPU Mechanics Bulletin, 1, pp. 39-49. DOI: 10.15593/perm.mech/2019.1.04. [11] Tableau, N. (2019). Multiaxial loading on a 3D woven carbon fiber reinforced plastic composite using tensile-torsion tests: Identification of the first damage envelope and associated damage mechanisms, Composite Structures, 227(3), pp. 111305. DOI: 10.1016/j.compstruct.2019.111305. [12] Matveenko, V. P., Shardakov, I. N., Voronkov, A. A. (2018). Measurement of strains by optical fiber Bragg grating sensors embedded into polymer composite material, Struct Control Health Monit., 25(4), pp. 1-11. DOI: 10.1002/stc.2118. [13] Belousov, I.S., Zheleznov, L.P., Burnysheva, T.V. (2024). Compression Test Simulation of Layered Composites with Delamination, Aerospace MAI Journal., 31(1), pp. 93-104. https://vestnikmai. ru/publications.php?ID=179111. [14] Medvedsky, A.L., Martirosov, M.I., Khomchenko, A.V. (2022). Composites in the presence of multiple bundles of arbitrary shape under the action of dynamic loads, Trudy MAI, 124, DOI: 10.34759/trd-2022-124-06. [15] Greco, F., Lonetti, P., Luciano, R., Nevone Blasi, P., Pranno, A. (2018). Nonlinear effects in fracture induced failure of compressively loaded fiber reinforced composites, Composite Structures., 189, pp. 688-699. DOI: 10.1016/j.compstruct.2018.01.014 [16] Staroverov, O., Mugatarov, A., Sivtseva, A., Strungar, E., Wildemann, V., Elkin, A., Sergeichev, I. (2024). Fatigue behavior of pultruded fiberglass tubes under tension, compression and torsion, Frattura Ed Integrità Strutturale, 18(69), pp. 115-128. DOI: 10.3221/IGF-ESIS.69.09. [17] Staroverov, O.A., Mugatarov, A.I., Chebotareva, E.A. (2023). Studying the Regularities of Mechanical Behavior of Fiber Reinforced Plastic Composites under Preliminary Impact and Subsequent Quasistatic and Cyclic Loads, Russ. Aeronaut., 66, pp. 652–662. DOI: 10.3103/S1068799823040037.

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D. S. Lobanov et alii, Fracture and Structural Integrity, 71 (2025) 1-10; DOI: 10.3221/IGF-ESIS.71.01

[18] Senthil, K., Arockiarajan, A., Palaninathan, R., Santhosh, B., Usha, K.M. (2013). Defects in composite structures: Its effects and prediction methods – A comprehensive review, Composite Structures., 106, pp. 139–149. DOI: 10.1016/j.compstruct.2013.06.008. [19] Benasciutti, D., Whittaker, M.T., Dirlik, T. (2022). Fracture, fatigue, and structural integrity of metallic materials and components undergoing random or variable amplitude loadings, Metals., 12(6), pp. 1-4. DOI: 10.3390/met12060919. [20] Marques, J.M.E., Benasciutti, D., Nies ł ony, A., Slavi č , J. (2021). An overview of fatigue testing systems for metals under uniaxial and multiaxial random loadings, Metals., 11(3). pp. 1-16. DOI: 10.3390/met11030447. [21] Lomakin, E.V., Tretyakov, M.P., Ilinykh, A.V., Lykova, A.V. (2019). Mechanical behavior of X15CrNi12-2 structural steel under biaxial lowcycle fatigue at normal and elevated temperatures, PNRPU Mechanics Bulletin., 1, pp. 77-86. DOI: 10.15593/perm.mech/2019.1.07. [22] Lobanov, D.S., Slovikov, S.V., Lunegova E.M. (2023). Influence of Internal Technological Defects on the Mechanical Properties of Structural CFRP, Frattura ed Integrità Strutturale, 17(65). pp. 74-87. DOI: 10.3221/IGF-ESIS.65.06. [23] Slovikov, S.V., Lobanov, D.S., Chebotareva, E.A., Melnikova, V.A. (2024). The influence of technological defects on the mechanical behavior of CFRP during buckling under compression based on DIC data and acoustic emission, Frattura ed Integrità Strutturale, 18(69). pp. 60-70. DOI: 10.3221/IGF-ESIS.69.05. [24] Yankin, A., Wildemann, V., Belonogov, N., Staroverov, O. (2019). Influence of static mean stresses on the fatigue behavior of 2024 aluminum alloy under multiaxial loading. Frattura Ed Integrità Strutturale, 14(51), 151–163. DOI: 10.3221/IGF-ESIS.51.12. [25] Firdaus, S.M.; Arifin, A.; Abdullah, S.; Singh, S.S.K.; Nor, N.M. (2023). Fatigue Life Assessment of API Steel Grade X65 Pipeline Using a Modified Basquin Parameter of the Magnetic Flux Leakage Signal. Materials, 16, 464. DOI:10.3390/ma16020464.

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A.Ibrahim et alii, Fracture and Structural Integrity, 71 (2025) 11-21; DOI: 10.3221/IGF-ESIS.71.02

Indentation fracture toughness of Aluminium-Graphite composites: influence of nano-particles

Alqahtani Ibrahim School of Aerospace, Transport and Manufacturing, Cranfield University, College Road, Cranfield MK43 0AL, UK zafer.268152@gmail.com B. Niyaz Ahmed Engineering Department, College of Engineering and Technology, University of Technology and Applied Science, Shinas-Sultanate of Oman. Niyaz.budensab@utas.edu.om E. Ashoka Department of Mechanical Engineering, Bapuji Institute of Engineering and Technology, Davangere, India. ashokamech06@gmail.com, http://orcid.org/0000-0002-3062-5883 A. M. Rajesh*, P. B. Bharath Department of Mechanical Engineering, S.J.M. Institute of Technology, Chitradurga, Karnataka, India. rajesh.am82@gmail.com; https://orcid.org/0000-0003-1843-239X bharathauto999@gmail.com; https://orcid.org/ 0000-0001-5688-7323 Doddamani Saleemsab Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal, Karnataka, India. saleemsabdoddamani@gmail.com; http://orcid.org/0000-0002-8498-1488

Citation: I brahim, A., Niyaz Ahmed, B., Ashoka, E., Rajesh, A.M., Bharath, P.B., Saleemsab, D., Indentation fracture toughness of Aluminium-Graphite composites: influence of nano-particles, Fracture and Structural Integrity, 71 (2025) 11-21.

Received: 26.08.2024 Accepted: 06.10.2024 Published: 06.10.2024 Issue: 01.2025

Copyright: © 2024 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

K EYWORDS . Indentation, Nanocomposite, Graphite Nanoparticles, Fracture Toughness, Al6061.

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