PSI - Issue 81

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ScienceDirect

Procedia Structural Integrity 81 (2026) 251–254

© 2026 The Authors. Copy from the contract: 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 2025 organizers Keywords: Couple stress elasticity; non-stationary load; dynamic stress state; foam; defect interaction; cavities; modified polyurethane. 1. Introduction The process of formation of a cellular structure in polyurethane foams s important in shaping the properties of foams: density, strength, and thermal insulation and vibration-absorbing characteristics. However, the influence of degrading factors, such as sunlight, causes the occurrence and spread of chemical reactions that lead to the destruction of the polymer matrix. To prevent this phenomenon, the authors proposed a method for modifying polyurethane foam. However, this process causes a change in the structure of the material during the foaming process and the formation of cavities in the foam structure during the formation of the matrix. In this work, the authors propose a method for taking into account the influence of these defects on the distribution of the stress state in the foam medium. This method allows us to assess the influence of structural heterogeneity on the mechanical behaviour of the material and establish the need to use additional technologies for stabilizing pore formation, if such influence is significant. Polyurethane foams have a wide range of applications across many industries and significant potential for innovation and improvement (Ates et al., 2022; Kim et al., 2023). Due to the availability of production technologies and the flexibility of chemical composition, it is possible to obtain polyurethane foams with varying stiffness’s, offering different mechanical, physical, strength and functional properties. As a result, such materials can be conveniently adapted to specific requirements. Among the new areas of application of polyurethane foams, one can note their use for shielding electromagnetic radiation (Wang et al., 2018). Also, shape-memory elements are used for biomedical applications (Dong et al., 2024). Abstract The article is devoted to the development of an approach to studying the interaction of defects in the form of cavities and holes in modified polyurethane foams on their mechanical behaviour under the action of unsteady loading. To study the stress state of the foam medium, the approach within the framework of couple stress elasticity is modified. The developed methodology allows account the influence of the material's microstructure based on the analysis of the stress distribution for the case different types of loading. The developed methodology allows analyzing the stress state for the case of availability cavities of different sizes and shapes. Based on analysis of the stress distribution one can conclude about the reflection of waves from the boundaries of the cavities. VIII International Conference “In - service Damage of Materials: Diagnostics and Prediction“ (DMDP 2025) Investigation of defect interaction in structurally inhomogeneous media Olena Mikulich a, *, Nazar Semenyshyn a , Olexandr Sad a a Lutsk National Technical University, 75 Lvivska str., Lutsk 43018, Ukraine

* Corresponding author. Tel.: +380-33-274-6111 E-mail address: olena@lutsk-ntu.com.ua

2452-3216 © 2026 The Authors. Copy from the contract: 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 2025 organizers 10.1016/j.prostr.2026.03.043