PSI - Issue 59

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000 – 000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 59 (2024) 292–298

© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers Abstract The research discusses the peculiarities of fatigue fracture of hybrid composite sucker rods. Loading of composite sucker rods by rotational bending leads to their damage during operation with the appearance of longitudinal cracks on the side surfaces. Their occurrence is caused by delamination of the fibreglass shell, which arises due to the uneven distribution of stresses in t he rod’s cross-section. Fractographic studies of the fracture features of composite sucker rod were carried out. The surface layer of the specimen hardened by fibreglass filler is crucial for its fatigue life. The fracture of the sample under cyclic loading was initiated near their lateral surface due to the delamination of a part of glass fibres in the rod’s shell from the more plastic matrix. The reason for these delaminations was the discrepancy between their elastic moduli. This was confirmed by secondary cracks along the boundaries of the shell’s components. Once the cohesion between glass fibres and a polymer matrix was broken, the fibres deformed independently of the matrix in each loading cycle. Their final failure was due to a brittle cleavage mechanism with typical river patterns on their fracture surfaces. At the next stage of damage, ductile stretching of the polymer connecting bridges between delaminated fibres occurs, up to their rupture. The stress concentration in the tip of a fatigue crack, formed as a result of the gradual fracture of glass fibres and polymer bridges, creates preconditions for failure propagation deep into the rod's cross section. The rod's core, reinforced with carbon fibres, breaks due to tension. At the final stage, this is accompanied by the pulling of part of the carbon fibres from the polymer binder due to loss of cohesion between them. © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers VII International Conference “In -service Damage of Materials: Diagnostics and Prediction ” (DMDP 2023) Feature of fatigue fracture of the composite sucker rod Halyna Krechkovska a,b, *, Bohdan Bakun c , Ihor Kopey c , Oleksandra Student a a Karpenko Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, 5, Naukova St., Lviv, 79060, Ukraine b Lviv Polytechnic National University, 12, Stepana Bandery St, Lviv, 79013, Ukraine c Ivano-Frankivsk National Technical University of Oil and Gas, 15, Karpatska St, Ivano-Frankivsk, 76019, Ukraine

* Corresponding author. Tel.: +38-067-811-2543 E-mail address: krechkovskahalyna@gmail.com

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers

2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of DMDP 2023 Organizers 10.1016/j.prostr.2024.04.042